Specifications Part 1 - Water Supply, Sewerage and Tube Well Works

to accommodate the larger diameter of the joint and to permit the joint to bemade properly.12.9.4 Excavated material should be deposited at a sufficient distance from the trenchso that damage is not caused to the pipe line through falling stones/debris.12.9.5 Prepare the bedding by laying on soft soil and alternatively compacting andwatering sparingly until an effective thickness of 100 to 150 mm is achieved.12.10 Laying12.10.1 Lay the pipe in the trench after ensuring that bell holes have been provided forat the appropriate places in the bedding (Pipes of diameter 110 mm or less,with no live load application, do not require bell holes in the trench bottom).12.10.2 These have to be refilled carefully after testing of the pipeline and prior tocomplete backfilling of the trench.12.10.3 Though not essential, the pipes should be laid with the spigots entered into thesockets in the same directions as the intended flow of water.12.11 Minimum cover:12.11.1 A minimum cover of 0.9 m when truck traffic is expected.12.11.2 A minimum cover of 1.8 m when heavy truck /locomotive traffic is expected.12.11.3 If due to the side conditions deep burial of the pipe is not possible andheavy traffic is expected over the pipe, it is advisable to use steel orreinforced concrete casing (sleeve) to prevent damage to the pipe.12.12 Anchoring12.12.1 The purpose of the anchor block is to transfer the total thrust to the trenchsides. It is therefore important to take account of the load-bearing capacity ofthe surrounding ground.12.12.2 Recommended mixture for concrete is one part cement, two parts washedsand and two parts gravel.12.12.3 Where concrete would be in direct contact with the pipe or fittings, these shouldbe wrapped with a compressible material, for example rubber sheet or foamedpolyethylene sheet.12.13 Back-filling12.13.1 The first side fill or hunching layer should be placed by hand and compacted inlayers under the lower quadrants of the pipe up to the spring level (half thevertical diameter) of the pipe.12.13.2 Compaction can be done by careful trampling with the feet or with tramplingtool.Urban Administration & Development Department Page 141