This part of the Specifications only deals with the permanent steel liner or casing. When permanent steel casing is shown on the Drawings, the steel shall conform to the Indian Standard Specification IS 2062: 2011 or equivalent.
The minimum thickness of the permanent steel casing/liner shall be 10 mm. The minimum length shall be from 100 mm above the bottom of the pile cap to 5 metres under the riverbed or into firm strata. If the permanent casing is used in the boring operation or if the handling and transport require a greater thickness to avoid deformation or buckling, the increase in thickness shall be provided by the Contractor at his own expense.
The steel casing/liner shall be furnished in appropriate lengths and the joints shall be approved by the Engineer.
Also, read for Design of Pile Foundation.
The casing or liner shall be handled and stored in a manner that shall prevent buckling and other deformation as well as accumulation of dirt, oil and paint. When placed in the work it shall be free from dirt, oil, grease, paint, mill scale and loose or thick rust.
The outside surface of the permanent casing of piles to river piers, for the depth indicated on the Drawings from the underside of the pile cap, shall receive two coats of anti-corrosion tar type paint. The paint shall be approved by the Engineer and its application shall follow the manufacturer’s instructions.
The Contractor shall demonstrate to the satisfaction of the Engineer that his proposed construction methods for the piles do not result in the pile shafts being weakened by contamination of the concrete, by sectional reduction, by washing out of cement, by breaking during pulling of temporary casings or in any other way, including the construction of neighbouring piles.
Also read for ANCHORAGE VALUE OF HOOKS AND BENDS
A) Assumed Procedure
The following construction procedure has been assumed in the tender design. The final construction procedure shall be as approved by the Engineer prior to commencing piling operations.
also, read for: What is liner in pile foundation?
1. Place permanent steel casing, if required, in position and embed casing toe into river bed or firm strata. If no permanent steel casing is specified a sufficient length of temporary steel casing shall be used to stabilise the upper part of the borehole.
2. Bore and excavate inside the steel casing down to casing toe level, or to a level approved, and continue excavation to final pile tip level using either temporary casing underwater or using drilling mud. The fluid level inside casings shall at all times be at least 2 metres higher than outside the casings.
3. Carefully clean up all mud or sedimentation from the bottom of the borehole.
4. Place reinforcement cage, inspection pipes etc.
5. Concrete continuously underwater, or drilling fluid, by use of the tremie method.
6. Withdraw the temporary boring casing concurrently with concreting to the instructed level.
7. After hardening, break out the top section of the concrete pile to reach sound concrete.
B) Approval of Construction Method
In the tender, the Contractor shall describe the construction method he proposes, including the name of the proposed Sub-contractor (if any), information on boring equipment, materials, methods of work and control of quality. The Contractor shall submit references from similar jobs carried out by him and/or his proposed Sub-contractor.
During contract negotiations, the Contractor shall submit all requested supplementary detailed information in writing.
After the Contract has been awarded, the Contractor shall prepare a detailed programme and establish a procedure for the pile construction. The detailed programme shall contain all required information on materials, equipment, methods of work etc. and be approved in writing by the Engineer. Such approval shall not, however, relieve the Contractor of his responsibilities for pile construction.
The import of any boring equipment or materials by the Contractor, before he has received the Engineer’s approval of proposed construction methods, shall be at the Contractor’s risk.