Construction technology of wet-sprayed pile \x0d\ ① The construction site of wet-sprayed cement pile should be leveled in advance, and all obstacles below the ground (including stones, roots, garbage, etc. ) must be removed, and accurately release the pile location. Drainage and dredging should be carried out in low-lying areas or pond areas, and then plain soil (miscellaneous fill is not allowed) should be backfilled to a flat elevation; \x0d\ ② Construction machinery: The power of deep pile construction machinery should be above 45KW, with three layers of drilling blades, with two blades on each layer, the distance between the top and bottom is 300mm, the included angle between two horizontal blades is 30 degrees, and the width of each blade is 100mm. \x0d\ ③ The construction operation steps are as follows: \ x0d \ a. Rig positioning; \ x0d \ b. Drill pipe sinking; \x0d\ c. When shotcrete is lifted below the ground 1m, slow speed should be adopted; When lifting to 0.25m below the ground, stop shotcreting and stir for a few seconds to ensure the pile head is uniform and dense; \ x0d \ d. Repeatedly stirring, sinking and shotcreting; \ x0d \ e. Repeatedly stir and lift to above 0.25m ground; \ x0d \ f. Turn off the mixer; \x0d\ ④ The cement used for cement slurry mixing pile is 42.5-grade ordinary cement, the pile diameter is 1250px, the cement dosage is 50~60kg/m, and the formula test strength of pile body is1.2mpa. Before construction, it is necessary to pass indoor formula test and pile-forming technology test to master the pile-forming technology and various technical parameters of this site. \x0d\ ⑤ Allowable deviation value \ x0d \ a. The error of cement dosage is not greater than1%; \ x0d \ b. In order to ensure the verticality of the mixing pile, attention should be paid to the flatness of the lifting equipment and the verticality of the guide frame to the ground, and the verticality deviation should not be greater than1.5%; \ x0d \ C. The deviation of pile position shall not be greater than125px; ; \ x0d \ d. The time for the mixer to sink or rise shall be recorded by special personnel, and the time error shall not be greater than 5 seconds; \ x0d \ e. After seven days of piling, excavation inspection shall be conducted to observe the uniformity of piling and mixing. After 28 days of pile formation, the unconfined compressive strength of the pile was tested by drilling and coring. The frequency and inspection standard of sampling pile number shall be implemented according to the relevant inspection letter of provincial height index. The control standard of unconfined compressive strength (90-day age) of pile body is1.2 MPa \ x0d \ 6 Precautions \ x0d \ a. Cement slurry should be mixed in strict accordance with the predetermined proportion. The prepared mud shall not be isolated or allowed to stand for too long, and the label of mud used for more than 2 hours shall be lowered; When mud is poured into aggregate, it should be filtered to avoid mud caking and damage to the pump body. \ x0d \ B. Before pumping mud, the pipeline should be kept wet to facilitate mud transportation. When mixing cement slurry on site, there should be a special person to record the cement dosage and the start and end time of pumping cement slurry. \ x0d \ C. Mud supply must be continuous and mixing must be uniform. Once the slurry is stopped for some reason, in order to prevent pile breakage and lack of slurry, the slurry mixer should sink to 0.5m below the slurry stop surface, and then the slurry is lifted after the slurry supply is resumed. If the machine stops for more than 3 hours for any reason, in order to prevent the slurry board from blocking the pipe, the slurry conveying pipe should be disassembled and cleaned for later use. \x0d\ d 2% gypsum (cement weight) should be added to the cement slurry. \ x0d \ e. Pay attention to the experienced team in the bidding construction of deep mixing piles. \x0d\ ⑦ Suggestions on construction parameters of cement mixing piles \ x0d \ a. The penetration rate should be ≤ 1.0m/min. In order to ensure the uniformity of ash in the pile, it is not advisable to bring slurry when drilling. At the same time, cement slurry should be mixed according to the determined water cement ratio (generally 0.4~0.5). Cement slurry must be pre-stirred for more than 4 minutes before entering the shotcrete pool, and must be stirred at any time in the shotcrete pool to ensure that the cement slurry does not segregate. \ x0d \ b. The mixing and lifting speed of sprayed concrete is