Construction method statement of bored pile

Preparation works are including: - Shop drawing of bored piles is approved by the Consultant . - Bored pile construction sequence, operation area of drilling machine team, equipment movement chart conforms to construction schedule of each bored pile

Construction method statement of bored pile 1. Flow chart : Page 1 of 8 Preparation work Setting out of pile (Inspect center point) Preliminary drilling Install temp.casing (Inspect center pile) Boring work Preliminary cleaning (Inspect bored hole) Mix bentonite (Inspect bentonite) Install rebar cage (Inspect connection) Fabricate rebar cage (Inspect rebar) Air lifting cleaning (Inspect bentonite) Pouringconcrete Remove temp. casing Backfill over pile End 2. List equipment : List of major construction equipments will use for pilling work : No. Name of equipment Number Used for Remark 1 Drilling equipment DH350-5 01 each Drilling hole 2 Backhoe 0.8m3 01 each Excavate Exis.pavement 3 Dumptruck 12m3 03 each Disposal of soil 4 Mix truck 05 each Concreting 5 Air compressor Denyo 01 each Cleaning hole 6 Sand Sieve 01 each Separation sand and betonite 7 Bentonite mixing system 01 set Mixing and treating bentonite Including tanks 8 Tremipipe pipe D =300mm, L = 56 m 01 set Concreting 1m x 2pcs 2m x 2 pcs 3m x 12 pcs 9 Air compress pipe D=90mm L = 56 m 01 set Cleaning hole 6m x 7 pcs 10 Bending machine 01 each Rebar 11 Cutting machine 01 each Rebar 12 Water pump 6 inch 02 each Recover bentonite 13 Water pump 4 inch 02 each Supply bentonit 14 Water pump 2 inch 02 each Serving 15 Casing D1100, t=10mm L = 6m 02 each Boring 16 Drilling bucket D1000 02 each Boring 17 Cleaning bucket D1000 02 each Cleaning 18 Steel plate 1,5x6x0.01m 4 sheet Support machine 19 Generator 125KVA 1 Unit Supply power Page 2 of 8 3. Detailed method statement : 3.1 Preparation work: Preparation works are including: - Shop drawing of bored piles is approved by the Consultant . - Bored pile construction sequence, operation area of drilling machine team, equipment movement chart conforms to construction schedule of each bored pile - Preparation of manpower and equipments for construction work - Preparation of materials (mixed concrete, rebar, bentonite, and other materials) - Preparation of test instrument : slump, bentonite liquid, depth of boring hole, diameter of bored pile, . 3.2 Setting out bored pile Center point of every bored pile is set out exactly by total station base on coodination of the designed location. After set up the center point, the off-set point will make to keep enough distance from boring pile. 3.3 Preliminary drilling After mark the off set point, it will start the excavation for checking the obstruction structure and underground utility by using adequate equipment and manpower. The initial excavation will execute up to 1.5m from the existing ground. The preliminary drilling will execute by using the drilling device with drilling bucket attachment for installing of the temporary casing. The attachment device will check the center point and vertical. 3.4 Installing of temporary casing After preliminary drilling, it will install the temporary casing up to the preliminary drilling elevation. The diameter of the temporary casing is 10cm bigger than the design diameter. Length of the temporary casing will use 6m. Contractor will check the location and verticality of the by survey. Incase the location and verticality is not satisfy the specification, it will re-install the temporary casing. After installing the temporary casing it will start the backfill and compaction around the temporary casing. Page 3 of 8 3.5 Boring Work Before starting the boring work, it will pour the bentonite slurry into the bore hole. The level of the bentonite slurry will be kept more than higher of the ground water level to avoid the collapse in the bore hole. The boring work will use the drilling bucket. The speed of the bucket will be as the lifting is about 0.5m/s and lowering is about 1.5m/s The boring soil will stock near the hole. The stock soil from the bore hole will be loading to the dump truck by using the backhoe and disposal out of the project. will check the verticality and soil condition during the boring time. When the boring reaches the bearing layer, will request the inspection of the bearing layer to consultant. 3.6 Preliminary cleaning of boring hole: After boring, it will change the bucket from drilling to cleaning. Contractor will check the requirement depth of the bored hole. After checking, it will wait the next work for monitoring the sedimentation for approximately 20-:-30 munites. Contractor will check the depth of the bored hole again. In case it has the more than 20 cm of sedimentation in the bored hole, Contractor will execute the cleaning work by using the cleaning bucket. 3.7 Bentonite slurry control : Contractor will use and control the bentonite slurry for protection the collapse in the bore hole during the boring work. The design mix of bentonite slurry is as following the table. The mix of the bentonite slurry will use the bentonite mixing system. Design mix of the bentonite slurry: ≤ 5% The quality of the bentonite will check 1 time per bore hole as before pouring into the bore hole. The result of test will be as following the table No Item Range of result 1 Density Less than 1.10g/ml 2 Viscosity 30-90s or less than 20 cP 3 pH 9.5-12 Page 4 of 8 3.8 Installation of rebar cage: Before installing the rebar cage, Contractor will complete finishing the inspection of the rebar cage. After preliminary cleaning, Contractor will install the working stage on top of the temporary casing. The rebar cage will be lowered into the bore hole to design elevation by crane. The lap of the main rebar will use the tie wire(steel, minimum 1.5mm diameter) The rebar cage will be hanged by 3 pecies rebar. 3.9 Install the tremie pipe After installing the rebar cage, the tremie pipe will be install at center of the bore hole. The bottom of the tremie pipe will set about 20-30cm from the bottom of the bored hole. The length of the tremie pipe will use 3m, 2m and 1m for adjusting pipe,and will be combined from 1m,2m,3m parts for convernience adjust the length of tremie. 3.10 Air lifting cleaning of bored hole: After installing the tremie pipe, Contractor will check the depth of bored hole. In case the bored hole is still clean, it will start the preparation of concreting work. In case it has sediment, the bored hole will be cleaned by air lifting method. The air lifting method will use the tremie pipe and D90mm pressed-air pipe. The air lifting method will be continue up to cleaning of sediment. 3.11 Concreting work: The concreting work will use the tremie pipe. It will insert sponge into the tremie pipe avoid to segregation The every mixer truck will check the concrete slump before unloading the concrete. Slump of any trucks is less than requirement will be rejected. The tremie pipe will keep to embed in the concrete at least 2m. Contractor will measure the top of concrete level at every mixer truck The top of concrete will be cast above the cut off level to at least 1.5m Page 5 of 8 3.12 Pull up of casing: After concreting it will cut the hanging rebar of rebar cage. Temporary will be pull up by using adequate equipment. 3.13 Temporary backfilling above pile casting level : After concreting, the bored pile will be curing at least 4 hours for temporary backill. After backfilling, it will cover the steel plate at the bored pile Page 6 of 8 4. Safety on site 4.1 Characteristics of bored pile construction: - Boring machine and crane are used. - The construction equipments are numerous and heavy. - Construction material is much, heavy and cumbersome. Therefore, the working safety must be strictly considered. 4.2 Specific methods: For the laborers working on site: - All technique staffs and workers work onsite have training on labor safety and sanitation of bored pile construction - Strictly conform to all regulations on labor safety, sanitation and other regulations. - It will have health checked to ensure good health for assigned work (especially for the people having heart disease, vertigo disease, high blood pressure, who will not be arranged to work at high or deep locations… ) The sickly people will be timely replaced in the construction time. - It will trained suitable with the assigned work and have experience in the construction. The worker must not be work in contrary with the trained job. - Have been equipped sufficiently the safety devices such as clothes, boot, glove, welding glass, safety belt etc… - When working in the step of craning or installation (load casing, steel case …) the worker will keep out of reach of heavy things and lifting equipment. For equipment and machinery working on site: Those equipments will get absolute safety, specific as follows: Have calibration certificate issued from authorized body. The spare parts of equipment and machinery working on site will be regularly checked and maintained in order to assure the safety. (especially systems of brake, cable, crane hook…) Regularly check construction equipment prior to starting working shift to timely repair the fails, assure progress of work. Page 7 of 8 In the construction progress, the operator and serviceman must check and maintain the important spare parts such as: Pulley, cable, brake system of boring machine and crane in serving for construction of bored pile. Regular check and tighten of screw must be done to bolts, circuit breaker cabinet, welding wire, welding machine. Occasionally add lubricant to equipments and machinery, water for cooling. In the construction process, should any equipment have unusually phenomenon, those will be stopped and checked for safety, then restart for construction. In the construction process, the operator will not leave control cabin. If the left of control cabin is unavoidable, he must report to the team leader or technical staff to arrange another worker for temporary replacement. For the crane worker: will have sufficient safety devices (safety helmet, safety clothes, glove …) and will know the up and down signal for crane operator. Must have signal board, ban board, and fence at the dangerous construction locations. If the problem arise in the construction progress, the will report to Employer, Engineer and functional bodies for settle the problem on time. The electricity safety will be paid special attention in the construction process. The worker, when working at the location involving to electricity, will be equipped with electricity safety devices such as rubber boot, insulated glove … Strict prohibition Do not throw devices, equipment from high place to the ground. Do not drink wine, bear and other stimulant in the working shifts. Do not travel out of the working area. Do not sit at the foundation hole in the breaking time. Do not travel or sit under the loading/unloading heavy things. Propagation The slogan with safety content is written. Propagate the safety regulations to all workers. Make all workers fully aware of the labor safety on site. Page 8 of 8