METHOD STATEMENT FOR 800MM BORED PILE CONSTRUCTION METHOD STATEMENT FOR 800MM BORED PILE CONSTRUCTION Biện pháp thi công cọc khoan nhồi D800 METHOD STATEMENT FOR 800MM BORED PILE CONSTRUCTION METHOD STATEMENT FOR 800MM BORED PILE CONSTRUCTION Biện pháp thi công cọc khoan nhồi D800 METHOD STATEMENT FOR 800MM BORED PILE CONSTRUCTION METHOD STATEMENT FOR 800MM BORED PILE CONSTRUCTION Biện pháp thi công cọc khoan nhồi D800
Project : PHU MY BRIDGE PHU CUONG Co., Ltd METHOD STATEMENT FOR CONSTRUCTION OF BORED PILE WITH TEMPORARY CASING AND BENTONITE SOLUTION APPLIED STANDARDS: Vietnamese Construction Standard TCXDVN 326:2004: Bored piles – Standard for construction, check and acceptance ASSHTO of practice for foundations Technical Specification cast in place Bored piles ( Project : PHU MY.) STEP 1: ADJUST THE PILING MACHINE ON THE PILE AXIS Prepare the drilling place, position the pile axis - Given the soil base of the construction site, our principle in this case is to move the piling machine mainly in an one-way movement, starting from side out, without running over the completed bored holes - The pile construction steps, from drilling to concreting, must follow strictly the sequence proposed for the week that has been approved by the Site Manager New holes must not be made too close to the just finished piles, as the latter need time to mature Specifically, • • The distance between adjacent piles must be at least 0.8m centre to centre of bored pile The construction time of adjacent piles must be at least 24 hours - Having determined the pile ID numbers, the Contractor will proceed to locate the pile axis, based on the surveyed marks and using use theodolite and steel measuring tape Preparations must be made in areas around the drilling place to determine the pile centerline Areas around the boreholes will be prepared to facilitate operation of the piling machine, the muck removal and movement of agitator – trucks, etc without affecting the construction of other piles - Once the pile axis has been determined, equidistant points will be established to serve as basis for the steel case positioning and pile axis check during the drilling process Prepare the piling machine: Method Statement for Bore Pile works Project : PHU MY BRIDGE PHU CUONG Co., Ltd - Before drilling, the piling machine must be serviced and trial runs to ensure smooth operation during drilling process - The drilling bucket: The opening between the drilling buckets will be smaller than the nominal size of the drill shalf by 1÷ 4cm The up and down hauling the buckets along the pile shaft, coupled with the swaying of the kelly bar during the drilling, will enlarge the bored hole at least to the nominal diameter After having completed a few initial bored piles, the rise level of concrete will be checked in order to decide on the opening of the bucket opening Haul the piling machine to the drilling place: - After positioning the pile axis, the piling machine is hauled to the drilling place The horizonal position of the machine is then adjusted using a surveyor’s level The kelly bar is adjusted to be vertically on the pile axis The deviation from vertical position of the kelly bar should not exceed 1% Verticality of the kelly bar is monitored using a plumb bob, or theodolite With a normal kelly bar length of 15 m, the deviation between its two ends must be less than 15 cm, corresponding to ½ of its size STEP 2: Casing work: - - - HOLE OPENING – CASTING INSTALLATION Casings are pre-fabricated in the workshop Because of the casings, the actual size of the bored hole is often larger than its nominal size ( (normally 80 mm÷100mm) by mm÷10mm the top end of the steel case to prevent it from sinking more than expected depth Depending on the actual geological conditions, the steel cases may be placed at 6m÷9m Based on our experience with test piling in this area, 6m long steel case is appropriate Before placing, the steel casing must not be deformed that may affect the movement of the drilling bucket within the casing Bentonite slurry: - Bentonite must be calculated in sufficient quantity, and delivered to the construction site The bentonite slurry must be prepared before drilling, using proper mixing equipment, with sufficient quantity for the entire drilling process The slurry must meet the specifications in Table 1, before it is used in the pile shafts Method Statement for Bore Pile works Project : PHU MY BRIDGE PHU CUONG Co., Ltd Table 1: (in compliance with ASSHTO specification construction standard) Physical property Density Viscosity (s) Required data of slurry before using in pile shaft 1.05÷1.15cm3 28 ÷ 45 PH Sand content 8-11