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

15.17.11.3 If a portion of shoring to be left in the trenches / pits at such places, where it isabsolutely necessary to do so as to avoid damage which may be caused tobuilding, cables, gas-mains, water-mains, sewers, etc. in close proximity of theexcavation, by pulling out the shoring from the excavations. Contractor shallnot claim, on any reason, whatsoever for the shoring which may have been leftin.15.17.12 Steel plate shoring15.17.12.1 Where the subsoil conditions are expected to be of a soft and unstablecharacter in trench / pit excavation the normal method of timbering may proveinsufficient to avoid subsidence of the adjoining road surfaces and otherservices. In such circumstance Contractor will be required to use steel trenchsheeting or sheet piling adequately supported by timer struts, walling, etc., asper the instructions, manner and method directed by engineer. Contractor shallsupply, pitch, drive and subsequently remove trench sheeting or piling inaccordance with other item of the specification.15.17.13 Bedding15.17.13.1 The bedding for pipe shall be provided as specified in the drawings or as perdirections of engineer.15.17.13.2 The trench bottom shall be even and smooth so as to provide a proper supportfor the pipe over its entire length, and shall be free from stones, lumps, rootsand other hard objects that may endure the pipe or coating. Holes shall be dugin the trench bottom to accommodate sockets so as to ensure continuescontact between the trench and the entire pipe barrel between socket holes.15.17.14 Concrete cushion, embedment and encasement.15.17.14.1 Concrete embedment and encasement wherever required, shall be constructedas per the details given in approved drawings or as directed by the engineer,where concrete bedding is to be placed beneath the pipeline, the sub-gradeshall be prepared to dimensions as shown in the drawings.15.17.14.2 The bottom of the trench may be sloped on the sides or kerbed, but thethickness of concrete shall be as specified in the drawings or as directed by theEngineer. Dry mix will not be permitted.15.17.14.3 For earth, granular material or concrete embedment, each pipe section shallhave uniform bearing on the sub grade for the full length of the pipe barrel,suitable excavation shall be made to receive the pipe, bell or collar and allowadequate room for proper workmanship in making the joint.15.17.14.4 Adjustment to line and grade shall be made by scraping away or filling in withgravel or concrete and not by wedging or blocking up to bell. Pipe sockets andbarrels shall be clean and free from dirt at the time of jointing.15.17.14.5 The concrete for bedding portion will be mixed moist or damp to give a slumpof not more than 25 mm and for sides and top portions of encasement, ifspecified, will be mixed to obtain a slump between 25 mm and 80 mm.15.17.14.6 All water in the trench must be disposed off prior to placing of concrete. Thereshould be no cleavage line between the bedding concrete and the sideembedment concrete.Urban Administration & Development Department Page 191