AFTESGUIDELINES ON WATERPROOFING AND DRAINAGE OF UNDERGROUND STRUCTURES Version 1 – approved by Technical Committee 3 May 2000 Drafted by J.L. MAHUET – Chairman, GT9 on Waterproofing of Underground Structures with the assistance of P. HINGANT (SCETAUROUTE-DTTS) – M. JERRAM & C.TRUFFANDIER (SNCF) – J.L. REITH & B. CONSTANTIN (CETU) J.P. BENNETON (LRPC, Lyon) Mlle BEORO (LRPC, Nancy) – J.F. JABY (EOS) ) MM. MERLE & MOREAU (DORKEN France) – MM. MANRY & AUMOITTE (WAVIN) MM. SAFFAR & PORTAIL (COBLOND) - M. FAYOUX (ALKOR DRAKA) M. JOLLY (PAVITEX) – M. ROUGERIE (POLYFEUTRE) M. LEBLAIS (SIMECSOL) – M. ANDRE (SNCF) – M. CHEZE (SIAAP) kindly helped with the final editing SUMMARY Pages Pages 1 - FIELD OF APPLICATION OF GUIDELINES . . . . . . . . . 2 - DEFINITIONS AND VOCABULARY . . . . . . . . . . . . . . . . 3 - PREPARATION AND ACCEPTANCE OF BACKING SURFACES TO RECEIVE A GEOMEMBRANE WATERPROOFING SYSTEM IN CUT-AND-COVER TUNNELS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1 - FIELD OF APPLICATION . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2 - BACKING SURFACE PREPARATION AND ACCEPTANCE 3.2.1 - Characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2.2. - Acceptance of backing surfaces and corrective measures for non-conformities . . . . . . . . . . . . . . . . . . . . . . . 3.2.3 - Summary table of backing surface acceptance operations . 4 - CHARACTERISTICS OF GEOTEXTILE AND GEOCOMPOSITE PROTECTIVE BARRIERS . . . . . . . . . . . 4.1 - GENERAL CHARACTERISTICS OF PROTECTIVE BARRIERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2 - CHEMICAL COMPOSITION OF GEOTEXTILE FIBRES . 4.3 - MINIMUM UNIT WEIGHT OF PROTECTIVE BARRIER . 4.4 - HYDRAULIC CHARACTERISTICS . . . . . . . . . . . . . . . . . . . 4.5 - PHYSICAL AND CHEMICAL PORPERTIES . . . . . . . . . . . 4.6 - RESISTANCE OF PROTECTIVE BARRIERS AGAINST HEAT DAMAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 - GEOSPACERS AND DRAINAGE . . . . . . . . . . . . . . . . . . 5.1 - DRAINAGE FUNDAMENTALS . . . . . . . . . . . . . . . . . . . . . 5.2 - DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.3 - REFERENCE STANDARDS AND TESTS . . . . . . . . . . . . . . 6 - INTERCEPTION OF LOCALISED LEAKS . . . . . . . . . . 6.1 - ROOF AND SIDEWALL INTERCEPTORS . . . . . . . . . . . . . 116 116 117 117 117 117 118 119 119 119 119 119 119 120 121 121 121 122 122 122 122 6.2 - TEMPORARY INTERCEPTION AND DRAINAGE OF INVERT IN STRUCTURES RENDERED COMPLETELY WATERTIGHT BY A GEOMEMBRANE WATERPROOFING SYSTEM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.1 - Driven tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6.2.2 - Cut-and-cover tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 - DRAINAGE SYSTEM ASSOCIATED WITH A GEOMEMBRANE WATERPROOFING SYSTEM AT BOTTOM OF TUNNEL ROOF . . . . . . . . . . . . . . . . . . . . . 7.1 - PURPOSE OF DRAINAGE SYSTEM . . . . . . . . . . . . . . . . 7.2 - CHANGES IN DRAINAGE SYSTEM DESIGN . . . . . . . . 7.3 - DESIGN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.4 - ACCEPTATION OF DRAINAGE SYSTEM . . . . . . . . . . . . 123 123 124 125 125 125 127 127 8 - POROUS CONCRETE . . . . . . . . . . . . . . . . . . . . . . . . . 8.1 - POROUS CONCRETE MIX COMPOSITION . . . . . . . . 8.2 - POROUS CONCRETE SPECIFICATIONS . . . . . . . . . . . 8.3 - POROUS CONCRETE DRAINAGE SYSTEM . . . . . . . . . 9 - PERMANENT DRAINAGE SYSTEM FOR SIDEWALL AND ROOF JOINTS . . . . . . . . . . . . . . . . . . . 9.1 - DESCRIPTION OF CONTRACTION JOINT DRAINAGE SYSTEMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9.1.1 - Physical and chemical characteristics of seepage . . . . . . . 9.1.2 - Frost protection to drainage system . . . . . . . . . . . . . . . . . 9.1.3 - Drain discharge and hydrostatic pressure . . . . . . . . . . . . . 9.2 - DRAINAGE SYSTEM DESIGN . . . . . . . . . . . . . . . . . . . . 127 127 128 128 10 - BIBLIOGRAPHY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133 TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 115 • 128 128 128 130 130 131 protective puncture barrier placed against the backing. aware that these omissions in the French regulations might impede the development of these new waterproofing and drainage techniques. the use of. . . undertook in 1997 the task of updating the CCTG General Specifications in the following areas: • Preparation and acceptance of tunnel backing surfaces destined to receive a geomembrane waterproofing system. it is subject to the hydrostatic pressure. for example. unless the Guidelines are made part of the contract documents. 2 . November/ December 1998. • Protective static puncture barrier placed in contact with the backing surface. The definitions of the more important terms in these Guidelines are as follows: • Waterproofing. each fulfilling a precise function: .50m wide.3 of Fascicule 67 Titre III CCTG General Specifications and tables 1 and 2 below. the pressure is not total but not necessarily zero). or absence from the specifications in Fascicule 67 Titre III relevant to these new products. Structure built within the confines of a supporting structure (diaphragm walls. partially-immersed and other tunnels. The new AFTES Guidelines were published in the journal Tunnels et Ouvrages Souterrains No. • Formulation and publication of AFTES “expert opinions” to add to the list of waterproofing products and techniques not currently covered by the text of or Waterproofing and drainage of underground structures now refers to complexes or systems combining several materials of sometimes widely differing compositions and functions. geosynthetics as a waterproofing or drainage material in underground structures has greatly expanded.00m to 1. it may act as a first ‘watertight barrier’ to enable thermal seaming of the geomembrane to proceed. etc. chemical and (most importantly) hydraulic properties of de-bonding geotextiles. over each concrete joint in the tunnel roof. meaning that it may completely surround the structure.2. there are gaps in the materials and procedures specifications regarding the preparation of the backing surface to which they are applied. • Unsupported tunnel. The physical and mechanical properties of the protective barrier are specified in Article 7.Waterproofing may be total. or permanent and contribute to the waterproofing of the structure.1 of CCTG General Specifications in Fascicule 67 Titre III – property such that a product or combination of products prevents the passage of a liquid such as water: . and the meanings of some of them have been officially defined at European level. in which case it is not exposed to hydrostatic pressure (in this case. Article 2. in order. This barrier must always consist of a membrane of synthetic material (PVCP or polyethylene). The physical and mechanical properties of the protective barrier are also specified in Article 7. for example. New terms have recently appeared. Berlin walls. This barrier is also used in the form of strips. as with “umbrella” waterproofing for example for a tunnel roof. • Drainage. It consists essentially of a nonwoven geotextile. Interception at a point or over an area of water flowing into an underground structure. Drainage may be temporary. 1. • Geospacers. directly on the permanent concrete. 150. Independent extrados waterproofing complex consisting of several materials. in which case the waterproofing and drainage systems are installed after building. • Supported tunnel. etc. and in this case. This water is collected and disposed of by means of the structure’s main drainage system.protective mechanical barrier on top of the geomembrane when the permanent lining is reinforced.2. • Geomembrane waterproofing system.) which acts as the backing for the waterproofing and drainage systems.4. under the waterproofing geomembrane. TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 116 • .Waterproofing may be partial. and the physical. Polymer structure consisting of sheets of thermo-formed material or monofilament or any other structure whose purpose is to impart a high void ratio promoting the free flow of water under either temporary or permanent conditions. While. which should be amended accordingly. It is sometimes called the ‘extrados protection’ in connection with a geomembrane waterproofing system to a driven tunnel or cut-and-cover tunnel built within a supported trench. leading to the appearance on the market of innovative techniques and products. synthetic geomembrane-type waterproofing products are themselves generally adequately described in the CCTG General Specifications. • Protective dynamic puncture barrier. Structure built without temporary support (in excavation with sloping sides). to allow the waterproofing complex to be installed in the correct manner. on top of the waterproofing geomembrane. AFTES working group GT9. .Guidelines on waterproofing and drainage of underground structures 1 – FIELD OF APPLICATION OF GUIDELINES commentary on Article 4 of Chapter III of Fascicule 67 Titre III of the CCTG General Specifications. Berlin walls. These Guidelines are applicable to the waterproofing and drainage of underground structures such as machine-bored. 7 of Annexe 4 of Fascicule 67 Titre III CCTG General Specifications. The appearance of such new products soon revealed a lack of detail in. sometimes called ‘intrados’ protection in connection with a geomembrane waterproofing system to a driven (reinforced) tunnel or cut-and-cover tunnel within a supported trench. The geotextile ply is placed in contact with the backing surface. for example. • Mechanical protective geocomposite.DEFINITIONS AND VOCABULARY Since the official issue in January 1992 of Titre III of this Fascicule. under the waterproof geomembrane. in the event of a major inflow of water. Updated lists of AFTES “expert opinions” are published regularly in the journal Tunnels et Ouvrages Souterrains. Combination of a nonwoven geotextile and a thin sheet of generally PVCP or polyethylene synthetics. The present wording of these Guidelines extends the field of application of Article 3 to backing surfaces of cutand-cover tunnels whose sidewalls consist of diaphragm walls. sometimes associated with a PVCP or polyethylene film such that. They provide additional details to be inserted into the CCTP Contract Specifications and CC AP Special Conditions in Fascicule 67 Titre III of the CCTG General Specifications on Waterproofing of Underground Structures.translucid synthetic waterproofing geomembrane. cut-and-cover.3 and No.4. 3.2. suffer from the same omissions in Article 9. especially as. unlike the ‘umbrella’ type geomembrane waterproofing system used in some tunnels. Figure 1 illustrates the various components associated with a geomembrane waterproofing system. sheet piling and similar steel support.Characteristics a) Diaphragm wall – precast diaphragm wall – concrete counterwall Specifications in Article 9. b) Slurry wall 3. Strip drain consisting either of a geospacer or drainage geocomposite of variable width placed parallel to the tunnel centreline whose main function is to facilitate the discharge of water flowing in from the backing towards the drainage system at the bottom of the sidewall or roof.1 . i. Berlin walls.e.sheet piling with concrete counterwall . Working group GT9 suggest the following specification: “The slurry shall have the mechanical strength required by the CCTP Contract Specifications before installing the geomembrane waterproofing system. etc.2.sheet piling with high density polystyrene filling the troughs.precast diaphragm wall .2 . 150) of Tunnels et Ouvrages Souterrains add important details on tunnel waterproofing to Article 9 of Fascicule 67 Titre III of CCTG General Specifications.1 . A combination of geospacer and one or more geotextiles providing a filtering effect.PREPARATION AND ACCEPTANCE OF BACKING SURFACES TO RECEIVE A GEOMEMBRANE WATERPROOFING SYSTEM IN CUT-AND-COVER TUNNELS AFTES Guidelines on the preparation of tunnel surfaces destined to receive a geo- These Guidelines apply to all tunnels built in a shored trench using the following types of support: . Strip drain consisting either of a geospacer or drainage geocomposite of variable width placed at right angles to the tunnel centreline whose main function is to facilitate the discharge of water flowing in from the backing towards the drainage system at the bottom of the sidewall or roof.FIELD OF APPLICATION • Drainage geocomposite. the geomembrane waterproofing system in this case is always exposed to hydrostatic pressure under operational conditions. Circular drains made of synthetic material or box-outs in the banquette to collect discharge from a geomembrane waterproofing system and convey it to the main drainage system.nailed shotcrete .Berlin wall (steel soldiers with timber or precast concrete lagging) . • Horizontal drainage strip.1.Guidelines on waterproofing and drainage of underground structures membrane waterproofing system published in the November/December issue (No. The present text expands the recommendations applicable to tunnels to include installation of a geomembrane waterproofing system in cut-and-cover tunnels. This type of support is not covered by Fascicule 67.Illustrates the various components associated with a geomembrane waterproofing system. having temporary support in the form of diaphragm walls.2. Figure 1 . Drainage geocomposites are generally used as permanent drainage to the sidewalls in cut-and-cover tunnels built in unsupported trenches. specifications regarding backing surface preparation in cut-and-cover supported tunnels. • Drainage hoop. 3 .4 of Fascicule 67 Titre III.BACKING SURFACE PREPARATION AND ACCEPTANCE • Sidewall or roof bottom drainage. of Fascicule 67 Titre III are adequate.Mechanical protective geocomposite and horizontal drainage strip Photo 2 – Geospacer on steel temporary support 3.1. However. TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 117 • .diaphragm wall . Photo 1 .slurry wall . 1. and the only verification needed is maximum misalignment between the surface and the steel members. d) Shotcrete .2. the only verification needed is misalignment between steel members and plates. of Fascicule 67 Titre II .2) Verification of surface roughness of diaphragm wall: Article 3.Sheet piling support with polystyrene filling troughs b) Slurry walls The general geometry should raise no problems.Hybrid support: Berlin wall and nailed shotcrete TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 118 • . . para.c1) Steel The specification in Article 3.c2) Polystyrene Add the following to Article 9. 150 of Tunnels et Ouvrages Souterrains applies. Any edges exceeding 5cm shall be feathered to 45° with mortar or other type of incompressible material.1.d2) Verification of backing surface roughness of shotcrete: Article 3.3. The verification should be performed according to the procedure in Appendix 1 of the recommendations.1) Verification of general geometry of shotcrete surface: Article 3.4c of Fascicule 67 Titre III – Precast diaphragm wall with concrete counterwall: Add to Article 9.2. and superficial cohesion of the slurry. The verification should be performed according to the procedure in Appendix 1 of the recommendations. of the guidelines published in No. 150 of Tunnels et Ouvrages Souterrains should be added to those in Article 9.1 of recommendations published in No.2.” Photo 3 . Photo 4 .Guidelines on waterproofing and drainage of underground structures “Dry. 4. The fillet is generally mortar radiused to more than 5cm radius. 150 of Tunnels et Ouvrages Souterrains should be added to those in Article 9. Steel sections shall be flush with the slurry wall surface to within 5cm. of Fascicule 67 Titre III.1 of recommendations published in No.Acceptance of backing surfaces and corrective measures for non-conformities Once special points have been dealt with as described above.2.4 below.1. the acceptance procedure for the prepared backing surface comprises the following operations: a) Diaphragm wall – precast diaphragm wall – concrete counterwall .2. b above.2.Ground diaphragm wall support Photo 5 .2 of the recommendations published in No. 150 of Tunnels et Ouvrages Souterrains applies. The verification should be performed according to the procedure in Appendix 2 of the recommendations.1. 150 of Tunnels et Ouvrages Souterrains applies.3.2. of Fascicule 67 Titre III: “Surfaces or panels shall be flush to within 5cm.a1) diaphragm wall with trowelled mortar finish as described in Article 9.2. c) Berlin wall and sheet piling with polystyrene filling Ditto para. panels and polystyrene blocks.d.1) Verification of general geometry of backing surfaces: Article 3. c) Berlin wall and sheet piling with polystyrene filling the troughs .” d) Shotcrete The specification in Article 3.4b of Fascicule 67 Titre III: “The polystyrene shall be a perfect fit in the sheet piling troughs and shall be class EM as described in French standard NFT 56 201 with minimum compressive strength of not less than 90 kPa.1. The verification should be performed according to the procedure in Appendix 2 of the recommendations.2.2. e) Fillet a2. 150 of Tunnels et Ouvrages Souterrains applies.2.” a2.2. A fillet should be formed where the vertical surface meets the tunnel invert (applicable to all surfaces mentioned above).a2) Diaphragm wall – ground down without trowelled mortar “Length of intermediate fastening nails for the geomembrane waterproofing system shall be set with reference to the mechanical strength of the slurry. loose superficial slurry shall be removed. .1. Characteristics of the geotextile protective barrier appear below in table 2. 3.2 of the recommendations published in No. of the guidelines published in No. . the geotextile might be replaced locally by a protective/draining geocomposite as described below. As in the case of driven tunnels. 4.600 g/m 2 for concrete segments (machine-bored tunnels) .02. a) Driven tunnels The CCTP Contract Specification may require a higher value.GENERAL CHARACTERISTICS OF PROTECTIVE BARRIERS Article 13. 150. 4 . This minimum remains unchanged in the specifications to be included in a CCTP Contract Specification. may consist These characteristics concern chiefly mechanical strength (static puncture strength).4.Summary table of backing surface acceptance operations The sequence of surface acceptance operations described in Table 1. of Fascicule 67 Titre III of the CCTG General Specifications states that the principal function of these geosynthetics is to provide mechanical protection against puncturing or tearing of the waterproof geomembrane.4. As stated elsewhere in these recommendations. and bearing in mind developments in tunnel support. 4.3. the draining capacity for example of the protective barrier under both temporary and permanent conditions is not considered in Fascicule 67 Titre III. The unit weight for diaphragm walls not finished with trowelled mortar and shotcrete may be increased on the basis of mean maximum depth of sidewall roughness measured during suitability tests on site. Depending on seepage rates. because TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 119 • . also called ‘extrados protection’ on supported trench cutand-cover structures. on the basis of shotcrete roughness values (mean maximum depth at sidewall and roof of shotcrete roughness) measured following the suitability test performed on site. under permanent operating conditions.1000 g/m2 for steel support.800 g/m2 for metal fibre reinforced shotcrete . 4. This will make it possible to intercept and drain small water flows during construction. more particularly in the case of a geomembrane waterproofing system in tunnels.or a geocomposite consisting of a thin PVCP or polyethylene geomembrane. of the recommendations published in Tunnels et Ouvrages Souterrains No.3.MINIMUM UNIT WEIGHT OF PROTECTIVE BARRIER . .1 .Adaptation of the mechanical characteristics of the protective barrier with reference to the recommendations on preparation and acceptance of tunnel backing surfaces preparatory to installing a geomembrane waterproofing system published in the November/December issue (No. of Annexe 3 specifies a minimum unit weight of 600 g/m2. 150) of Tunnels et Ouvrages Souterrains. polypropylene or similar materials must be used.2 of Annexe 3 and Article 7 of Annexe 4 of Fascicule 67 Titre III of CCTG General Specifications issued in January 1992 describe the characteristics to be specified for the geotextiles and geocomposites associated with geomembrane waterproofing systems.3.3 . 4.CHEMICAL COMPOSITION OF GEOTEXTILE FIBRES Much research has indicated a not inconsiderable risk of hydrolysis of polyester fibre in an alkaline environment and this material must not be used in underground structures where the material is usually in contact with concrete. This protective barrier. 4. 150 is also applicable to the acceptance of cut-and-cover tunnel backing surfaces.Incorporation of a drainage function in the protective barrier.either of a geotextile made exclusively of synthetic fibres of at least 700 g/mm2 unit weight in cut-and-cover tunnels and 600 g/m2 in driven tunnels. The minimum unit weight for Berlin walls is 1000 g/m2. Article 7.Guidelines on waterproofing and drainage of underground structures 3. minimum unit weights for protective barrier materials have been introduced for the following types of surface: . and 13. Articles 7.4 – HYDRAULIC CHARACTERISTICS Working group GT9 recommends that a drainage capability should be added to the mechanical strength originally devolved on protective barriers against static puncture by Fascicule 67 Titre III. There follows a summary of the relevant parts of the Fascicule 67 Titre III CCTG General Specifications (as regards minimum permitted and not nominal unit weights). The present Guidelines therefore expand the specifications in Fascicule 67 on the following points: .diaphragm walls – precast diaphragm walls – concrete counterwalls – slurry walls – sheet piling with polystyrene filling. This draining function is even more important on completion of the works.3 .2 . preventing water passing through the geotextile with the possibility of interfering with thermal seaming of the strips of synthetic waterproofing geomembrane. bonded in the factory to a geotextile of the same nature and physical and chemical characteristics as the geotextile described above. the increase in unit weight should refer to the different acceptance situations in Table 1 appended to the recommendations published in Tunnels et Ouvrages Souterrains No. .4. b) Cut-and-cover tunnels Article 7 of Annexe 4 specifies a minimum unit weight of 700 g/m2. durable protection against static puncture due to surface defects. geosynthetics form the first component of a geomembrane waterproofing system. 150. preferably light in colour. These adaptations are also offered with reference to the recommendations in Article 3 and apply more specifically to cut-and-cover tunnels.2.CHARACTERISTICS OF GEOTEXTILE AND GEOCOMPOSITE PROTECTIVE BARRIERS As stated in section 2 Definitions and Vocabulary. This minimum value remains unchanged for the following types of surface: . They are placed in contact with the backing surface to accommodate excessive surface roughness and provide reliable.2. the characteristics show in table 2 in para.02.2. Appendix 1. The only difference concerns the characteristics of geotextile protective barriers. apply to cut-and-cover tunnels. with reference to acceptance conditions as described in Table 1 of the recommendations published in Tunnels et Ouvrages Souterrains No. It might be noted that protective geocomposites are commercially available with the following properties: .600 g/m2: thickness 200 microns minimum .minimum capacity 15 litres/metre/hour .PHYSICAL AND CHEMICAL PROPERTIES Working group GT9 recommend adapting and amending the specifications concerning . Standard These values were determined from a transmissivity test performed by the procedure described in French standard NF EN 15012958 under the conditions described in para. in cut-and-cover tunnels). 5. connected to the sidewall or roof drainage system if designed as permanent installations.1000 g/m2: thickness 100 microns minimum .1200 g/m2: thickness 100 microns minimum.drainage with a thick layer of geogrid . This hydraulic characteristic is not required for protective barriers in which the geomembrane waterproofing system does not provide permanent drainage (for example.501 for synthetic membrane protective barriers and NF EN ISO 10319 for geotextiles and similar products. At places where inflow is more than 30 l/min. interception and drainage must be provided by drains.7 0.Specifications for driven tunnels Minimum requirement (*) Support shuttered or trowelled concrete.6 x 10-6 Table 1 . as described in section 6 of these Guidelines. • Underground structures with large areas of support and diffuse seepage liable to pass through the geotextile protective barrier: Replace the geotextile protective barrier with a geocomposite consisting of a geotextile placed against the backing surface having a unit weight of up to 600 to 1200 g/m 2 (to suit mean maximum roughness depth at bottom of sidewall and roof) and a transmissivity of not less than 4.Specifications for cut-and-cover tunnels TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 120 • .6 x 10-6 4.6 x 10-6 4. On the geomembrane face. These new specifications are shown against structures and backing surface types in tables 1 and 2 below.8 0.8 1 Elongation at max force (%) 50 50 50 50 70 Tensile strength (kN/m) 12 12 12 12 30 (*) Minimum not nominal specification Table 2 . another factor considered will be permeability to water (NFENISO 10319).watertightness with a thin synthetic layer (PVCP). for higher flows. These values are proposed for water flows habitually encountered in underground structures.5 . wall hybrid Geotextile unit weight (g/m2) 700 700 800 800 1000 Static puncture (kN) 0.6 x 10-6 4. sheet piling with polystyrene filling Shotcrete w/o fibre w/fibre Ground Berlin diaphragm wall. wall. w/o fibre w/fibr NFEN 963 Unit weight (g/m ) 600 80 600 1000 NFP 84507 Static puncture 8mm dia needle (kN) 0. to prevent fouling if for example the inflowing seepage displays ‘incrusting’ properties. GT9 recommend the following modifications to the geomembrane waterproofing system.3.6 x 10-6 m2/s The geocomposite is fastened to the backing surface by means of synthetic disks as described in the GT9 recommendations on the use of PVC disk fasteners for geomembrane waterproofing systems published in Tunnels et Ouvrages Souterrains No 138.tensile properties according to French standard NFP 84.507.6 7 Elongation at max force (%) 70 70 70 70 Tensile strength (kN) 12 12 12 12 NFEN ISO 10319 NFEN ISO 10319 NFEN ISO 12958 2 Transmissivity at 150 kPa (m2/s) 4. working group GT9 recommends the following minimum hydraulic values: . These protective geocomposites may usefully be recommended if the seepage water is highly ‘incrusting’ or carries a heavy load of fines from the surrounding ground.8 0. GT9 will expand this recommendation at a later date after examining geotextile filtering properties. • Underground structures displaying locally high flows (more than 0.6 x 10-6 m2/s. .Guidelines on waterproofing and drainage of underground structures it must collect water flowing in from the surrounding ground and convey it to the drainage system generally installed at the bottom of the sidewall or roof. install hoops consisting of geospacers of variable width to convey the water to the drainage system at the bottom of the sidewall or roof before installing the geotextile protective barrier.800 g/m2: thickness 150 microns minimum . Steel arch Concrete segments and plate support Shotcrete support Minimum requirement Proposed hydraulic characteristics Following many comparative laboratory tests of hydraulic transmissivity on several types of geotextile.static puncture strength according to NFP 84. In order to ensure lasting performance of the draining capability of the protective barrier.5 l/min): At leakage sites. or filled with grout if designed as temporary installations.filtration with a layer of geotextile . The drains must be 4.6 0. the geotextile is combined with a synthetic film of the following thickness (to suit the relevant geotextile unit weight): .7 0.minimum transmissivity 4. Protective geocomposite: partial protection against heat damage is provided by the synthetic film on the geomembrane side.Vertical drainage geocomposite on supported-trench cut-and-cover tunnel sidewalls Synthetic materials basically providing drainage performance as defined and described in section 1 above are used. . To control this type of damage. it often happens that the protective barrier. it is usually conceived as preformed cellular panels 8-20mm thick (thickness to suit discharge required under 100-150 kPa green concrete pressure). in the meantime. b) Area drainage As with localised drainage.50m to 2. Fire resistance of protective barrier In the absence of any tests and French or European standards. in which case. geotextiles. Photo 6 . it generally consists of strips of geocomposite with a filter layer. GT9. Hoops and horizontal strip drains are simply pinned to the backing and connected up to the geomembrane waterproofing system drainage system.DRAINAGE FUNDAMENTALS Photo 7 . recommends the following practices to suit different types of protective barrier: .Geotextile protective barrier: use fastening disks of the type described in the recommendations published in Tunnels et Ouvrages Souterrains No.GEOSPACERS AND DRAINAGE GEOCOMPOSITES 5. usually a geotextile. among other things. but in view of the sensitivity to fire of. in which case the drain material is generally used alone without a geomembrane waterproofing system (except in a few cases where it may for example be used in combination with a partial geomembrane waterproofing system installed only at the roof or cover decking). and horizontally in driven tunnels at the cold joint between invert and roof. the working group realise the need to introduce fire resistance specifications in the medium term.Permanent seepage interception and drainage in an underground structure. the fire resistance of protective barriers was not specifically dealt with by GT9. they must always be used in conjunction with a geomembrane waterproofing system. . provided they are fitted at the edges with a waterstop (precompressed type) to prevent ingress of cement laitance when concreting the permanent lining. following laboratory and field testing. Strips of geospacer may also be used.Permanent drainage in which case. generally placed at the bottom of the roof or sidewall.RESISTANCE OF PROTECTIVE BARRIERS AGAINST HEAT DAMAGE During thermal welding of special synthetic disks to the geomembrane with hot air at 200-300°C. Polyethylene film performs better against accidental burning provided the film is not less that 200 microns thick.Temporary drainage in which case. These drainage materials can be used for the following functions: Localised drainage may be used in the following situations: . especially as manufacturers already possess this type of product in the laboratory. two cases are met with. in particular.Guidelines on waterproofing and drainage of underground structures 4. Drain strips must always be connected to a longitudinal drain. considerably reducing it static puncture strength locally.Temporary interception of water flowing into the driven or cut-and-cover tunnel. the drainage system provides the main seepage control system for the structure by intercepting and discharging seepage from the surrounding ground and preventing the build-up of hydrostatic pressure. Such specifications requiring.5 l/min. is accidentally burned superficially or more deeply. The system described in section 1 above may take the form of a hoop when installed as vertical strips of variable width or in the form of horizontal strips 1. The strips are generally pinned to the backing (in driven or supported cut-and-cover tunnels). In this configuration.vertically across joints in the linings to driven tunnels or in open trench diaphragm walls. .1 . 5 . .00m wide. which are frequently the source of ignition and sustain the subsequent fire in a geomembrane waterproofing system.6 . a minimum fire resistance of class MI or BI (DIN 4102) can be expected in the near future.Temporary localised drain using geospacer strip TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 121 • . These drain materials can be installed as follows: a) Localised drainage Interception and drainage of inflow with localised peaks in excess of 0. preference should be given to products of this type. 138 having a skirt of substantially larger diameter than the disk proper to provide greater protection locally against accidental heat damage. In this case.05 or as a default value 0. both in driven and cut-and-cover tunnels.2 . The pipes are held in place at intervals with pats of rapid hardening cement or metal staples.20m per layer. They do not usually need to be connected to the geomembrane waterproofing system except if the lea- TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 122 • . When designing the drainage system for the invert or cover deck. if necessary. and sometimes the invert.Temporary area drainage. to intercept localised leaks where the water might adversely affect the bond with the surrounding ground or support. of between 0. in the absence of precise data on the flows to be considered in designing the drainage system. before applying shotcrete or installing a geomembrane waterproofing system in order to allow these works to proceed normally. using geospacers or geocomposites whose characteristics are chosen with reference to table 3. but never where exposed to hydrostatic pressure. It is usually the sidewalls that are so equipped. is used mainly in cut-and-cover tunnels built in supported or unsupported trenches. However. under the following circumstances: a) Before spraying shotcrete. The drain strips are unwound vertically with an overlap (depending on the system) of 0. for example.REFERENCE STANDARDS AND TESTS Working group GT9 recommends designers including the following tests and standards in the Specification for drain materials to be incorporated in underground structures. 1993) on recommendations on the use of geotextiles – determination of hydraulic properties in drain and filter systems.Transmissivity test with gradient i = 1 performed as described in para. without losing sight of the fact that they must reflect the conditions under which the materials will actually be used. and these call for special longitudinal interception and drainage systems.ROOF AND SIDEWALL INTERCEPTORS Temporary or permanent interception may be considered.a) Driven Tunnels above. Therefore. which includes a waterproofing capability.10m to 0.Classification of drainage geospacers and geocomposites The transmissivity test should be performed by the procedure in NF EN ISO 12958 with a gradient i = 1.1 à 0. 5.DESIGN The designer must not specify the drainage capacity of the material on the basis of the capacity of the longitudinal drain.Long term creep test under compressive stress according to the standard in force. although it should be modified with the test specimen placed between a rigid panel and a flexible membrane. it is strongly advised to use drainage geocomposites having a filter layer to ensure durability of the drainage system. For a permanent drainage system. but this type of drain is quite rare in France. They are pinned to the backing with overlaps. general made of PVC.Permanent area drainage.Localised interception. semi-cylindrical flexible pipes are used. A post-creep transmissivity test should also be required. Two types of interceptor can be considered: .02 or 0. it will be between 50 kPa and 100 kPa.2 below. or inflows at the invert as mentioned in section 6. with hemispherical or cylindrical drains of suitable diameter for the flow rates involved. 6 . b) Cut-and-cover tunnels b1) Ver tical drainage for open trench tunnel . 6. Category Drainage capacity Drain dia. In this case. Test pressure should be 150 kPa for 6 hours (the time required for concreting the roof).25 à 0. and might also begin to refer to draft European standard NF EN 13252 on characteristics of geotextiles in drainage systems. by the method described in XP ENV 1897 on determination of creep properties under compression – classification index (G38126) (this standard is as yet experimental in France). Preformed cellular panels are generally used for this purpose.10m and 0. The drain strips are pinned to the backing at the top and. the classification in table 3 might apply.1 l/s/m Ø 100 mm 2 0. a) Driven tunnels a) Driven tunnels Drainage geospacers and geocomposites are ranked in table 3 below. due to the height of the strip. . but from the expected seepage flow from the surrounding ground. the vertical drain material is subject to a permanent pressure whose value depends on the height of the backfill.‘Area’ interception. The following tests should be specified: b) Cut-and-cover tunnels Inflow is usually less in cut-and-cover tunnels than in driven tunnels. 5. with a flow section habitually ranging from 6 cm2 to 20 cm2. Note that the designer might use experimental standard G 38. the first step will be to check that the transmissivity of the drainage material is compatible with the permeability of the surrounding ground.25 l/s/m Ø 125 mm 3 0. and connected to the temporary drainage or dewatering system. The capacity of the longitudinal drainage system will ultimately be of course set on the basis of the expected inflow rate. but must also refer to operational requirements specified by the owner (in particular. at 2% slope 1 0.1) transmissivity test should be specified under 50 kPa stress. mainly under the invert. The diameters in table 3 show the cross section theoretically needed to discharge the flows considered but do not allow for any fouling that might be expected with reference to the chemistry of the water.3 .INTERCEPTION OF LOCALISED LEAKS It may be necessary to intercept localised inflows of water. extra interceptors should be provided.Guidelines on waterproofing and drainage of underground structures . The vertical drainage system must connect with a polyethylene system with an inspection cover at most every 50m for cleaning the system. In the most common cases. B2) Horizontal drainage A low-gradient (i = 0. locations and dimensions of inspection points).061 (Feb. . depending on the system. at intermediate levels. the designer will have to calculate the longitudinal flow rate to check the drainage capacity (under a low hydraulic gradient) of the drain material specified and decide the spacing of pumpage points. .20m.1 . 5. For localised major inflows.5 l/s/m Ø 150 mm Table 3 . used in combination with a geomembrane waterproofing system to drain areas in the roof discharging high seepage flows.3. length of filled portion) must be the subject of a specific operating procedure submitted to the Engineer for approval. inflow is intercepted and disposed of in the following manner: .Stage 2: waterproof roof. If polymers are nage system of the geomembrane waterproofing system or the clean water main drainage system. Generally. . – Driven tunnels The connection to the temporary or permanent longitudinal drainage system of the geomembrane waterproofing system can be made as follows: The invert is usually concreted before installing the roof waterproofing system. it must always be filled with quick setting cement or polymer resins after the permanent tunnel lining has been concreted.30m to 0.TEMPORARY INTERCEPTION AND DRAINAGE OF INVERT IN STRUCTURES RENDERED COMPLETELY WATERTIGHT BY A GEOMEMBRANE WATERPROOFING SYSTEM b) After spraying shotcrete on vertical surfaces: in this case. for example. the method of filling the drain (type of filling material.Half-round drain ▼ Drawing 1 TEMPORARY SIDEWALL AND ROOF INTERCEPTION ▼ Figure 3 . it is advisable to use cylindrical PVC drains for temporary installations or cylindrical HDPE drains for permanent systems. to suit construction method: Figure 1 . it is recommended using two-part water-reactive polyurethanes which are much less pervious than single-component polyurethanes. 6.Drain panel strip drainage Figure 2 . grouting pressure. drains for localised inflows are usually connected directly to the clean water main drainage system.The same PVC or polyurethane pipes are generally used as before spraying shotcrete. Temporary drainage problems very often only concern intercepting and draining water flowing between the blinding concrete and floor geomembrane waterproofing system during the various construction phases. When using very large diameters to permanently drain large flows from. with a compressive strength of not less than 150 kPa. for semi-cylindrical pipes and geospacer strips. intermittently or permanently flowing karsts under hydrostatic pressure.or directly (depending on drain diameter and flow rate) into the permanent drai- Invert drainage can be provided in the following ways.1.either directly into the horizontal strip drain of the geomembrane waterproofing system. it is better to use strips of geospacer of the cellular drainage panel type as shown in sketch 1 on drawing 1. 6. waterproofing is done in two stages: .50m width is more efficient in intercepting leakage through a diaphragm wall joint. The connection with the geomembrane is effected either by a metal system (flange-to-flange type) or (the most commonly used arrangement) by a synthetic stub collar as shown in sketch 3 on drawing 1 below. In cut-and-cover tunnels. it is recommended a drain of at least 100mm diameter. . If a PVC drain provides the temporary leak interception function.Stage 1: waterproof invert and bottoms of sidewalls .2.Guidelines on waterproofing and drainage of underground structures kage exceeds 1 l/m. again in polyethylene.Connection between drain intercepting localised leakage and geomenbrane waterproofing system TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 123 • ▼ . Whatever material is used. used. The connection of this type of circular drain with the geomembrane of a geomembrane waterproofing system must be treated as a ‘singular point’ in the contractor’s waterproofing detail design drawings. in which case. As with any large permanent drainage system. because a 0.2 . Photo 8 . where the sidewall support may allow water to seep into the trench. Drawing 2 TEMPORARY INVERT DRAINAGE DURING CONSTRUCTION . Temporary interception and drainage at invert under geomembrane waterproofing system To avoid water pockets forming under the geomembrane waterproofing system. 5. The width of the panel is governed by the drainage capacity required. with inflow coming from the side support and excavation bottom. The sketch shows the most commonly used system because.Cellular drain pannel 6. a panel 20mm deep has a capacity of 1.3 l/s per metre width. Sketch 5 . Sketch 1 .” • Sketch 1: Cellular panel between blinding concrete and geomembrane waterproofing system. – Cut-and-cover tunnels Temporary drainage problems only arise with supported-trench tunnels. Sketch 3 . Compared to the alternative in sketch 1. preference is given to Where pump sumps are present. as dictated by the rate at which water collects in the sump or manhole. Its disadvantage is that it collects only part of the flow from the invert and hampers the work of installing the geomembrane waterproofing system (at the transverse seaming locations) and steel fixing. There are two possible situations: Sketch 2 . Marseille. it has the advantage of not interfering with the installation of the waterproofing system and fixing steel reinforcement.Junction between geomembrane waterproofing system and temporary pump sump TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 124 • . • Sketch 2: Flat gully drain at the lowest point of the invert between the blinding concrete and geomembrane waterproofing system. and more importantly. After providing the localised drainage arrangements described in para. This arrangement appears the most suitable for heavy inflows. this arrangement is mostly used where high inflows are encountered. although generally. b) Bottom to top method Geomembrane waterproofing system installation and invert concreting proceed from the lowest point on the longitudinal tunnel profile to the highest. the connection to the geomembrane waterproofing system must be made as shown in sketch 5.Longitudinal drains in blinding concrete in cut-and-cover tunnel The headers discharge into a sump or manhole at the lowest point.2.Guidelines on waterproofing and drainage of underground structures a) Top to bottom method Geomembrane waterproofing system installation and invert concreting proceed from the highest point on the longitudinal tunnel profile to the lowest.2. Capacity is governed by the flow to be discharged (see table 3).Flat gully drain a) Tunnel above water table This is the simplest case because no particular drainage system is needed except perhaps for providing a manhole or sump at low points to pump out rainwater. or grouting the ground if inflows are too heavy.sketch 1 for low inflows rates . firstly because of the discharge capacity offered by the 150mm circular drain commonly used. Circular drain diameter is chosen with reference to drainage capacity shown in table 3. • Sketch 3: Cylindrical drain in drainage trench. it is important to provide for permanent or intermittent pumping. The three arrangements already mentioned apply. apart from its good hydraulic capacity. There is a choice of three possibilities from the arrangements shown in drawing 2 “Invert drainage during construction. because it avoids all interference with geomembrane waterproofing system installation and steel fixing. the water collected is conveyed by a pair of lateral headers.1. drawing 2. b) Tunnel below water table This is the commonest situation. as shown in sketch 4. drawing 2.TGV HST tunnel.sketch 3 for high inflow rates with the risk of pockets of water lifting the geomembrane waterproofing system when pouring the invert concrete. For example. The steel cover to the pump sump must be watertight all the time the tunnel is exposed to hydrostatic pressure.Drain embedded in blinding concrete or invert base concrete Sketch 4 . circular drains (with or without an outer covering of geotextile) around which a waterproofing geomembrane is wrapped. it does have disadvantages. The gully has the advantage of allowing the flow section to be easily increased by increasing gully depth. were very widely used in the nineteen-eighties. of being distorted by the concreting work. the lower half carrying away the water. Despite the undeniable improvement from this type of drainage system. shown in sketch 1 on drawing 3 was to place the drain on top of the banquette. the steel angle and flat are both co-rolled (galvanised steel + PVC on top face). the geomembrane is anchored either on a co-rolled flat pinned to the banquette. c) Circular drains replaced by gullies with rigid covers In the nineteen-nineties.DRAINAGE SYSTEM ASSOCIATED WITH A GEOMEMBRANE WATERPROOFING SYSTEM AT BOTTOM OF TUNNEL ROOF there was the poor crushing strength of the drain. since they are in danger Photo 9 . These arrangements at the bottom of each roof arch collect seepage water flowing in from the surrounding ground. substantially reducing discharge capacity of the drain.Puymorens tunnel Rigid cover to drainage system using "metal tiles" withdrain strip TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 125 • .CHANGES IN DRAINAGE SYSTEM DESIGN The appearance of these seepage collection systems coincides with the use of the first synthetic geomembranes employed for providing a tunnel with ‘umbrella’ type seepage control. without any danger of crushing reducing the flow section. which have led to profound changes in the design and function of these drainage systems. as shown in sketch 3 of drawing 3. This new technique consists of boxing-out the shape of the future gully in the top of the banquette (so no drain pipe is needed) covered with rigid material which allows water to pass.2 . b) Generalisation of rigid straight circular drains These 100mm dia. In addition to this hydraulics problem. This type of drainage system quickly came up against problems. The geomembrane waterproofing system runs on top of the gully cover and.1. this kept it straight and the waterproof geomembrane was laid over it before it was fixed in place on the banquette. This process was marked by the following three stages. Generally the water drained towards the intrados of the lining was discharged directly onto the footpath through plastic tees at approximately ten metre intervals. This technique paved the way for the first CCTV inspection and cleaning arrangements. generally placed under the tunnel roadway. The drainage system was simply suspended from the support. or even a synthetic material capable of successfully withstanding loads applied by the green concrete. a) Use of agricultural-type circular drains These 80mm dia. connected to the drain by pipes inclined at an angle of 45°. or (this was the case in some Only the top half of the drain has slots spaced 120° apart. 7. This frequently crushed the drain. Laying the drain straight improved flow efficiency for the drained water and reduced the risk of fouling (depending on water chemistry). drawing 3. 7. A shotcrete shell sprayed just before concreting the roof provided strength for the drain during this phase of the works. The design of these systems subsequently evolved over time to reflect the practices and experience of engineers and respond to emerging concerns of owners regarding their maintenance. In this technique. the covering materials may be metal. circular drains are placed directly in a chase provided in the top of the banquette. As shown in sketch 2. collected by the geomembrane waterproofing system on the extrados of the permanent tunnel lining. the straight drain connects every 40-50 metres to a header. usually comprising a bay in the sidewall of variable dimensions. before concreting the banquette. concrete. the trend in drainage system design was to place the whole system inside the banquette. The water is then conveyed either by a combined or separate drainage system to a natural discharge point. such as the fact of having to follow the often tortuous configuration of the supports and the very many places where head losses resulted from the changes of direction of the drain. the waterproof geomembrane passes over the drain to a point in the banquette where it is joined to a steel angle embedded in the concrete or a flat pinned to the concrete. flow is improved by placing a horizontal strip of geospacer just above the drainage system. with no impact on the width of the banquette. by means of PVC strips pinned to the support.Guidelines on waterproofing and drainage of underground structures 7 . In tunnels where this technique is now used. – PURPOSE OF DRAINAGE SYSTEM The first development of this type of drainage system. such as with the branch pipes connecting to the under-road header. especially when concreting the tunnel lining when pressures of 100-150 kPa from the green concrete are common. means available and frequency of drain system cleaning during the operational life of the structure.Agricultural drain on banquette ▼ ▼ TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 126 • Sketch 3 Gully with rigid cover ▼ Drawing 3 DRAINS ASSOCIATED WITH GEOMEMBRANE WATERPROOFING SYSTEM AT BOTTOM OF ROOF Sketch 4 . on . drawing 3. as illustrated in sketch 4. the basis of the following criteria: These inspection bays provide for maintenance during operation of the structure.Inspection & cleaning bay for geomembrane waterproofing . drainage inspection and maintenance bays are housed in the lining at drain level. . They are spaced 25m to 200m apart. This type of cover has the advantage of saving a few centimetres in width at the lift surface between the banquette and roof sidewall concrete.Straight drain in banquette concrete ▼ Sketch 1 .flow rate of water intercepted .Guidelines on waterproofing and drainage of underground structures of the A43 motorway tunnels in France) is welded directly to synthetic grid material forming the rigid gully cover.physical and chemical characteristics of the water (see design section below) Sketch 2 . In nearly all road tunnels built or being built over the last five years. from each inspection and maintenance bay.011.Main tunnel drainage: The porous concrete under the invert is additional to the drainage system at sidewalls and roof. or by using only sand with a coarse gravel (0/5 et 10/20 for example).Ammonia NH4+ content . where sidewall and roof are waterproofed with a geomembrane waterproofing system. Porous concrete is characterised by its crushing strength and permeability. • Maintenance of drainage system As stated above. Porous concrete mixes are usually obtained either by using only gravel (5/10 and 10/20 or 10/20 alone for example). for example.Concentration of aggressive substances by the test procedure described in French standard NFP 18.1 . At the design stage. Void ratio is greater than 15%. after pouring all permanent linings. It is never reinforced or pumped.Guidelines on waterproofing and drainage of underground structures 7.POROUS CONCRETE MIX COMPOSITION 8 . It is strongly recommended that only siliceous aggregate should be used.ACCEPTANCE OF DRAINAGE SYSTEM . the spacing between the inspection and maintenance bays is very important for successful maintenance of the structure. but also with reference to the physical and chemical characteristics of the water.bottom of horizontal strip drain to overlap rigid covering.CO2 content Porous concrete is sometimes call nofines concrete. 8. of the drainage geocomposite or geospacer type.rigid covering material and horizontal strip drain to be strong and retain flow characteristics under pressure from green concrete (150 kPa) c) Construction criteria Photo 11 – Hurtieres tunnel – Drainage system at bottom of roof – Manufactured PVC units with rigid PVC covers . the complete drainage system must be inspected by CCTV.laitance not to penetrate into drainage system when placing roof concrete (the waterproofing geomembrane must always be anchored in a watertight manner to the banquette and rigid covering) . to the following criteria: a) Hydraulic criteria . b) Cement Cements must comply with French standard NFP 15.POROUS CONCRETE In order to obtain the desired permeability. and may be combined with the following drainage or waterproofing systems: . gap graded aggregate is strongly recommended. 2_ .Total suspended solids. TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 127 • . the following analyses should be made on water samples taken from the construction site: . Bay spacing should above all be specified on the basis of the flow to be controlled of course. 7.flow section between 150 cm 2 and 450 cm 2 .541. May 1985. the drainage system at the bottom of the roof must fulfil the following functions: • Collect and drain seepage water. A flow test might also be specified to supplement this inspection.DESIGN Photo 10 – Foix tunnel – Drainage system at bottom of roof – Precast concrete with rigid concrete covers In the first place.301 and display the NF mark.Drainage to part only of the tunnel or tunnel invert.3 .Sulphate SO4 content . The tunnel civil works construction contract should provide for checking the successful future performance of the drainage system at the bottom of the roof by specifying that.4 . for the following substances: . b) Mechanical criteria . a) Aggregate Aggregate must comply with the specifications in French standard NFP 18.continuity of flow between tunnel support and gully by providing for example a mortar transition curve . usually under the invert.Determination of calco-carbonic aggressivity – calculation of water saturation index .minimum absorption section (openings allowing water to pass) of rigid gully covering material 400 cm2 per metre tunnel length. Porous concrete is used mainly for horizontal surfaces.Magnesium Mg2+ content . g.02 m/s. aggregate for porous concrete must qualify as 'non-reactive' (NR). other cement types can be substituted by referring to French standard P 18. Since porous concrete is intended to be exposed to a permanent flow of water. The porous concrete must be accompanied by a drainage system to be able to monitor. especially its calco-carbonic aggressivity and total suspended solids.drainage system inspection chambers every 25-50 metres at most (the actual spacing is determined on the basis of the chemical analyses mentioned above).POROUS CONCRETE SPECIFICATIONS 9 . to be 100mm minimum diameter with provision for CCTV inspection 9. These drainage systems are mainly intended to intercept localised leaks through the contraction joints in underground structures. above should be performed when designing the drainage system. In the event of unavailability. The tests mentioned in para. especially at tunnel roofs and cover decking. Depending on the aggressivity of the environment as determined from the water analyses. K is the permeability coefficient dh J = ds is the hydraulic gradient V is the flow velocity or flow per unit area.1 .Physical and chemical characteristics of seepage .CEM.POROUS CONCRETE DRAINAGE SYSTEM The cement and aggregate must not produce disorders such as alkali aggregate reaction liable to adversely affect concrete integrity (French standard NFP 18. and if necessary.3. They are generally used in This requirement also applies to integrated structure tunnels (e. a) Compressive strength Twenty-eight day characteristic strength fc 28 is measured on 16 x 32cm cylinders. They are most often employed to intercept and discharge the seepage which usually occurs through joints in the sidewalls of cut-and-cover tunnels in which cast-in-place or prefabricated diaphragm walls provide the permanent structural support. or CPJ.CEMIII/B. The permeability coefficient is measured with the Darcy formula V = KJ = K dh ds If supplies are not readily available.011.3 . or V ≥ 0. The design and density of this drainage system will of course depend on the flow to be discharged to the main tunnel clear water drainage system and the physical and chemical characteristics of the intercepted water. In view of the permanent flow of water in porous concrete.physical and chemical characteristics of the water. diaphragm walls with inner lining concealing the drainage system). TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 128 • . to repair defective intrados and extrados waterproofing systems.ES or CLK.CEM. generally installed vertically.V/B cement. This subject will be dealt with at length in forthcoming guidelines on treatment of leaks into underground structures to be issued by working group GT9 in 2001.seepage flow rate and pressure. . 7. it is recommended providing manholes.CEM. Working group GT9 recommends avoiding any risk of clogging or loss of strength over time by preferably using French designations CHF.possible frost protection to drainage system The minimum requirements are as follows: . which must be checked and assessed by the procedure described in section 7. Seepage is intercepted by these systems. Because of their high void ratios. These drainage systems are also used.1 . discharging into open gullies at the sidewall toe which themselves discharge into the main tunnel drainage system. for inspecting and maintaining the drainage system. the permanent drainage system will have provision for inspection and cleaning.DESCRIPTION OF CONTRACTION JOINT DRAINAGE SYSTEMS Drawing 4 shows sketches of the various types of drainage systems currently used in underground structures.3 . 'potentially reactive' (PR) or 'worst case potentially reactive' (PRP) aggregate may be used. it might also be possible to use either CLC.drains. preferably polyethylene. whose CaCO content is less than 50%. In such cases. These tests are referred to in the LCPC recommendations mentioned above. The appropriate drainage system is chosen with reference to the following parameters: .III/C. 9.2 . It is recommended specifying V ≥ 0. in order to avoid any risk of the pores being partially or completely blocked by calcium carbonate precipitate.1.20 l/dm2/s structures not waterproofed by means of a geomembrane waterproofing system on the extrados or waterproofing system bonded to the intrados. in which c) Aggregate – cement compatibility 8. It is recommended specifying fc 28 ≥ 8 MPa b) Permeability Permeability is determined by measuring the flow of water passing through a 16 x 32cm cylinder. ensure the durability of its performance. such concrete must be classified as 'prevention class C' according to the 'Recommendations for the prevention of distress due to alkali aggregate reaction' issued by LCPC. porous concretes are relatively low-strength. subject to thorough investigation based on experimental data acceptable to the Engineer. it is strongly recommended not to use even C3A-poor ordinary (French designation CPA) or slag (CPJ) cement. For this reason. 8. or even removal and replacement.541).Guidelines on waterproofing and drainage of underground structures Cement content will not usually be less than 350kg cement per m3 concrete.PERMANENT DRAINAGE SYSTEM FOR SIDEWALL AND ROOF JOINTS If required by the results of the physical and chemical analyses of the water from the surrounding ground.ES cement.II/B containing less than 80% clinker. It is therefore necessary to find a compromise between concrete strength and permeability. a precompressed waterstop is recommended between the backing and anchor strip. the multi-stage seal is installed after controlling the leak by grouting.Manufactured strip with bolted flanges (sketch 5) The manufactured strip consists of a flexible polyethylene or PVCP synthetic geomembrane clamped at its edges between a pair of 'flanges'. In the event of high hydrostatic pressure.1 to 1 litre/minute). The manufactured strip generally consists of a flexible polyethylene or PVCP geomembrane. • Leakage water with high calco-carbonic aggressivity or heavy TSS load If the seepage water is qualified as highly 'incrusting' or heavily loaded. This drainage system is recommended for leakage of 0. a precompressed waterstop is placed underneath it along each edge. 35.5 litre/minute). by reason of its elongation potential. of Fascicule 67 Titre III of the CCTG General Specifications. The manufactured strip usually consists of an elastomer geomembrane.Internal drain and bonded thin film cover strip (sketch 4) This drainage system is used in vertical and horizontal configurations on in situ concrete in places where complete watertightness (and minimum dampness) is required.20m wide strip is bonded to the backing over its whole length with polymer adhesive (epoxy). if the leakage rate is locally high (0. formed to an 'omega' shape allowing the joint to open quite wide under high hydrostatic pressures. in horizontal configurations.1 to 0. which can be unmade.' is more applicable to joints in castin-place and prefabricated diaphragm walls and more generally.1 and 0. can be used for joints subject to large displacements. if leakage is very slight (drips).50m wide (to suit joint width) and pinned to the backing surface. but only for low to moderate leakage rates (less than 0. the following 'dismantlable' drainage systems must be specified: . In this particular case. the following 'non-dismantlable' drainage systems can be used: . TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 129 • . is made of polymer products which must comply with the specifications in Article 7. especially from the roof or cover deck.5 litre/minute at low hydrostatic pressure.2 litre/minute). preferably 20-30mm dia.30m wide. For heavy leakage.Guidelines on waterproofing and drainage of underground structures • Seepage with low calco-carbonic aggressivity or TSS content If the seepage water is what is called poorly 'incrusting' or poorly loaded. in machine rooms for example. for roof vaults and cover decking. The strip of thin film polymer.Strip drain covered with mortar or shotcrete (sketch 1.30m to 0. . This type of system is also used to repair operational tunnels suffering from watertightness problems. drawing 1) This drainage system is preferably used in the vertical position. 35. by reason of its 'stiffness. hot-air welded for its whole length to a co-rolled anchor strip (galvanised steel with a thin film of PVCP or polyethylene on top face) pinned to the backing surface. . The seal system is then similar to a single or two-stage seal as described in the AFTES Guidelines on seals in underground structures published in Tunnels et Ouvrages Souterrains No. This type of system. polyethylene. A fire resistant mortar can be used if fire resistance is specifically required. The composition and diameter of the round strip allowing the joint to expand and contract depend on expected joint movements.2. Sept/Oct 1979. The 0.20m to 0. . inside the joint. This type of installation.Manufactured strip bonded with polymer adhesive (sketch 3) This drainage system is preferably used with in situ concrete in vertical configurations but more importantly.Manufactured strip heat-welded to corolled anchor (sketch 2) This type of drain is preferably used in vertical configurations and.15m to Photo 12 – Manufactured strip drain heat-welded to co-rolled anchor 0. 0. The elastomer properties of the strip (more than 400% elongation) and the watertight edge bond makes this type of drain suitable for high-displacement roof and deck joints where leakage is locally high (between 0. the multi-stage seal must be designed in accordance with the typical sketches in the recommendations published in Tunnels et Ouvrages Souterrains No. Its relatively high cost is offset by its durability. It generally consists of an internal drain. generally polyethylene chlorosulphonate (Hypalon or equivalent). where there is heavy leakage. usually reinforced to prevent it bulging if accidentally exposed to hydrostatic pressure.Formed elastomer strip pinned to backing (sketch 6) These factory pre-formed strips are usually made of synthetic rubber such as EPDM or SBR. . joints with little or no movement. The strip drain is then covered with trowelled or sprayed mortar or concrete to protect it from damage. Average thickness of this thin film is usually 2mm. as will be described in forthcoming AFTES guidelines. It is 0. The strip drain usually consists of a cellular-plate geospacer as described in section 5 above. 5 and 1 litre/minute . The drainage arrangements illustrated in figure 7. The strip is fastened to the backing with stainless steel screws and wall plugs.Guidelines on waterproofing and drainage of underground structures with leakage rates of less than 0. . reference should be made to the engineering arrangements recommended in section 6. whose thermal conductivity at 0°C is less than 0. spaced approximately 2. the arrangement shown in sketch 5 is adopted with.2 . are routinely used for this type of leakage intercepted or draining to the dam drain system. The dimensions of the polyethylene half-round gutter and chase should be commensurate with the flow rate to be controlled. minimum compressive strength not less than 90 kPa. *Wet-process cross-linked polyethylene compressive strength to be not less than 90 kPa.1. finish chase sides with polymer resin-based mortar. • Temperature between –3°C and –15°C for not more than 5 days. usually 3mm narrower than the strip.00m c/c to suit leakage rates observed. 1.035 W/m/°C. • Temperature between 0 and –3°C for not more than 5 days. This high thermal capacity drain is generally formed as follows: . or affect the whole length of the tunnel. usually 80mm deep and 100mm wide. If the water is very 'incrusting' or carries a high solid load.Frost protection to drainage system In some situations. Strip specifications are as follows: *Polystyrene foam to be class EM as described in French standard NFT 56.Drainage with chase and rigid thermal insulant (sketch 9) This type of drainage arrangement requires prior study of thermal conditions in order to determine the dimensions of the chase and shape of the polystyrene or polyethylene foam strip acting as both drain and thermal insulant. a 0.5 – 0. This problem is influenced by the duration of freezing weather and the length of the tunnel. spaced approximately 2.Drill drain holes in bottom of chase. The following drainage systems may be specified. 9.00m c/c. commonly consisting of a 1520mm thickness of closed-pore polyethylene foam weighing more than 30 kg/m3.3 – Drain discharge and hydrostatic pressure If seepage water drain discharge and pressures are high.201. 3050mm diameter. leakage between 0. between the backing and the synthetic geomembrane strip.Cut a chase with double-blade saw.33m apart at sidewalls and 0.045 W/m/°C. and 80 x 8mm E26 galvanised mild steel clamping strips.5 litre/minute .00m to 1.30m apart.6 litre-minute. usually spaced 0. It may be confined to the portals or cut-and-cover sections.Force-fit an EPDM or equivalent hollow formed strip into the chase.25m apart at roof. The maintenance capability of this arrangement comes from the fact that the flange-type fixing system can be unmade.Insert factory-formed closed-pore polyethylene or polystyrene foam strips. Photo 13 – Frejus ventilation shaft – Drainage with cellular plate geospacers and polyethylene foam frost protection TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 130 • Photo 14 – Strasbourg – Drain strips with rigid polystyrene foam thermal insulant . depending on the physical and chemical characteristics of the seepage water mentioned above.Possibly.Cut a chase with a three-blade saw. The possibility of reinforcing with steel mesh the mortar or shotcrete backfill may be considered with reference to (i) the dimensions of the chase and (ii) the maximum pressure if the drain might accidentally run full.1. This type of drainage system usually has an opening at the top for periodically flushing out the drain with low or medium pressure water. the drainage systems must have provision for dismantling or cleaning. thermal conductivity at 0°C to be less than 0.25m to 0. In order to prevent the strip being forced out of the chase by accidental hydrostatic pressure from the ground or sucked out by the slipstream from lorries in road and motorway tunnels. it is advisable to hold it in place with 5cm wide stainless steel tabs. leakage less than 0. 9. To provide mechanical protection to the drain strip in urban tunnels and prevent it being forced out of the slot by accidental hydrostatic pressure. glued in place with adhesive.1 of these Guidelines.Prefabricated elastomer hollow strip (sketch 8) This type of drainage system is made as follows: . thermal conductivity at 0°C less than 0. another strip of thermal insulation.50m long. . .Drill drain holes in bottom of chase. . Apart from their frost protection function. the drainage system may be exposed to sub-zero temperatures in winter months with consequences which may have a disastrous effect on operation of the structure. generally spaced 0. it is expressly recommended to fit this type of drain with an orifice for periodically flushing it out with low or medium pressure water.Manufactured strip with internal frost protection layer and bolted flanges Generally speaking. The hollow strip can be removed for drain maintenance after removing these tabs.05 W/m/°C. . depending on the intensity of the cold and seepage rates: .6mm stainless steel cover strip is recommended. usually 200mm deep and 150mm wide. thermal insulation which may or may not be necessary.leakage rates to be intercepted and discharged Drawing 4 PERMANENT SIDEWALL AND ROOF DRAINAGE SYSTEMS ▼ ▼ Sketch 1 . determined as described in section 7. as dictated by a thermal study lasting not less than 5 consecutive days to determine the lowest temperatures recorded at the site.Drain strip with sprayed concrete or mortar over Sketch 2 .stresses which may or may not occur.2 .physical and chemical characteristics of the leakage water. and must always be accessible at the top to monitor and periodically clean the drain.DRAINAGE SYSTEM DESIGN .Manufacture strip drain with polymer adhesive TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 131 • . with highly 'incrusting' or heavily loaded water. due to the amplitude of joint movements (generally related to thermal gradient) cm2. For example.3.Manufactured strip drain heat-welded to co-rolled steel anchorage ▼ Sketch 3 . . Dimensions and capacities of the permanent drainage systems are based on the following parameters: .Guidelines on waterproofing and drainage of underground structures 9. above. it is recommended that the free drain section should not be less than 120 . Pre-formed drain pinned to backing Sketch 7 .Internal drain with thin film cover bonded to backing Sketch 5 .Guidelines on waterproofing and drainage of underground structures Drawing 4 PERMANENT SIDEWALL AND ROOF DRAINAGE SYSTEMS ▼ ▼ Sketch 4 .Manufactured strip drain bolted along edges Sketch 6 .Formed hollow elastomer strip in chase Sketch 9 .Drainage with chase and frost protection TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 132 • ▼ .Half-round drain in chase ▼ ▼ ▼ Sketch 8 . G. n° 138 : • T.C.O.S.Guidelines on waterproofing and drainage of underground structures BIBLIOGRAPHIE •••••• Fascicule 67 .S. "Etanchéité des ouvrages souterrains" Recommandations de l'AFTES : • T. n° 82 : • T.S.E.G.O.O. k TUNNELS ET OUVRAGES SOUTERRAINS – HORS-SERIE N° 2 – 2005 • 133 • . Recommandations pour l'emploi de rondelles PVC pour les fixations d'un D. Recommandations pour la préparation des supports de tunnels recevant un dispositif d'étanchéité par géomembrane.G. n° 150 : Recommandations relatives aux joints d'étanchéité dans les ouvrages souterrains Recommandation sur les réparations d'étanchéité en souterrains Essais de poinçonnement dynamique sur un D. n° 121 : • T.Titre III du C.S.S.E.T.O. n° 35 : • T.O.