322.1. General 1. Gaskets shall be in accordance with Section 212.
2. Gaskets shall be fitted into the grooves provided in the edges of the segment to be sealed in the manner recommended by the gasket manufacturer. The gasket dimensions shall be compati-ble with the groove profile, subject to the specified tolerances.
3. Gaskets shall be fitted to segments before being taken into the tunnel and shall be protected from damage during transport.
4. Care shall be taken to avoid displacing the gaskets during segment handling. No deleterious material shall be permitted in the groove or on the gasket.
5. Compression and hydrophilic rubber gaskets shall be bonded in position in the groove provided in the edges of the segment in accordance with the manufacturer’s instructions.
6. Hydrophilic and composite (compression/hydrophilic) gaskets shall be protected from the effects of rain or accidental wetting.
Segments with hydrophilic or composite gaskets shall not be erected in standing water.
7. Gaskets to be cast into the concrete segment shall be securely held in place in the mould during casting, and shall not be damaged during the demoulding process or cause damage to the segment.
323. Grouting
323.1. Cavity grouting of segmental lining
1. The term cavity grouting shall mean the grouting required to fill the cavities or voids between the excavated profile and the per-manent linings of underground works including that due to ground relaxation and any void between permanent and tem-porary linings. Grout for cavity grouting shall be as described in Section 213.
2. Primary grouting is the initial cavity grouting which is applied immediately after a unit of lining has been built.
3. Where primary grouting does not completely fill all cavities, secondary grouting shall be carried out.
4. The Contractor shall provide a grouting method statement for the Engineer’s agreement. The proposals shall include details and location of the mixing plant and grout pump, mix design and constituents, pumping rates and pressures, injection points, methods of monitoring, recording and controlling the sequence, preventing grout leakage and reconciling the volume of grout placed with the theoretical volume required.
323.2. Primary grouting
1. Primary grouting shall be undertaken at a pressure sufficient to place the grout properly but not greater than 1 bar above the prevailing hydrostatic pressure at the location of grouting unless the lining and equipment have been designed for higher pressures, and agreed with the Engineer.
2. Primary grouting shall be timed so as to minimise ground movement.
3. For linings erected behind a closed-face TBM, primary grout shall be injected via the shield tail skin unless otherwise agreed with the Engineer. In other cases primary grout shall be injected through grout holes provided in the linings.
4. In segmental linings grouted through grout holes, primary grouting shall proceed in sequence from invert to soffit in such manner that all air and excess water are expelled from the cavity progressively ahead of grouting. Valves shall be con-nected into the grout holes in order to allow the grout to set under pressure when the grout hose is disconnected. After the grout has set, permanent plugs shall be installed.
5. Any sealing material or device installed at the leading edge of the ring to prevent grout loss shall be removed upon comple-tion of primary grouting.
6. For segmental linings grouted through the tail shield, the Con-tractor shall propose a grouting sequence for approval by the Engineer.
7. The Contractor shall ensure that grouting pressures do not result in ground heave or overstress or distortion of lining or distortion or damage to gaskets or damage to other structures.
8. Grouting equipment shall be fitted with a pressure gauge and automatic pressure release valves capable of being preset to a specific pressure. Grout pressure is to be measured at the nozzle with a suitable gauge.
9. Primary grouting to segmentally lined shafts constructed by underpinning shall be carried out after the erection of each ring.
10. Grouting shall be carried out at pressures to completely fill the cavity with grout.
11. Where shafts are constructed by sinking as caissons, grouting shall be undertaken on completion of the primary lining and shall be carried out in such a manner that any lubrication fluid is displaced by grout without distortion of the lining.
12. Where the primary void filling is by pea gravel injection, subse-quent grouting shall be carried out in stages to the agreement of the Engineer.
13. Grouting of pipe jack tunnels shall be in accordance with Section 319.3.13.
323.3. Secondary grouting
1. Secondary grouting shall be undertaken in selected rings by means of removing grout plugs from the tunnel lining and drilling a hole to the back of the existing grout.
2. Secondary grouting is the regrouting of lining and shall be completed as soon as practicable but within 14 days of the primary grouting or when the face has advanced 50 m from the location of primary grouting whichever first occurs.
Secondary grouting shall be at a pressure consistent with filling all voids but shall not exceed the design pressures stated in the Particular Specification.
3. Upon completion of grouting, threaded grout plugs shall be fully tightened into the lining.
323.4. Cavity grouting of in situ lining
1. The Contractor shall grout all cavities, voids and spaces remaining unfilled outside the in situ concrete lining. Grouting of a section of lining will not be allowed until that section has achieved its design strength.
2. Procedures for cavity grouting of in situ lining to tunnels and shafts constructed with a waterproof membrane shall be subject to agreement with the Engineer.
3. Grout for cavity grouting shall be as described in Section 213, except where otherwise agreed by the Engineer, who may direct that large voids be filled with other materials. The grout consistency shall be sufficiently fluid, but not more so, to ensure that the grout flows freely under low (<100 kN/m2)
pressure into all parts of the space to be filled via grout pipes or grout holes provided for the purpose.
4. The injection points shall be provided and used for cavity grouting at an average of at least one per 2.5 linear metres of tunnel and more frequently in any areas of excessive over-break. Vent pipes shall be provided extending to the highest points of cavities. The injection points for cavity grouting in arched roofs shall be located within 500 mm of the crown unless otherwise agreed by the Engineer.
5. The Contractor’s proposals for the installation of grout pipes shall be submitted to the Engineer for agreement. Grout pipes and grout holes for cavity grouting shall be at least 40 mm internal diameter.
6. Grouting shall be carried out by equipment similar to that used for segmental tunnel grouting. Grouting pressures shall be such as will not damage the Works or any other property.
7. Grout pipes shall not remain within 25 mm of a finished con-crete internal surface, and when no longer required all injection holes in concrete linings shall be filled with dry pack mortar to within 25 mm of the finished concrete surface and finally made good.