长螺旋钻机钻孔灌注桩的注意事项（Matters needing attention of bored pile in long auger drilling machine）

长螺旋钻机钻孔灌注桩的注意事项（Matters needing attention of bored pile in long auger drilling machine） 长螺旋钻机钻孔灌注桩的注意事项(Matters needing attention of bored pile in long auger drilling machine) Points for attention of bored pile in long spiral drill During the drilling of long spiral drilling machine, the verticality of drilling must be paid attention to, and the main technical measures to control the verticality of drilling are: (1) compaction and leveling of construction site. (2) installation of Henan Sanli mechanical drilling rig should strictly check the verticality and flatness and active drilling pipe, drilling process should regularly check the verticality of Kelly bar, found that the deviation should be immediately adjusted. (3) check the drill bit, drill rod and drill pipe joint regularly, find problems and repair or replace them in time. (4) drilling in soft and hard soil interface or inclined rock surface should be drilled at low speed and low pressure. When drilling deviation is found, the clay should be backfilled in time and then drilled at low speed and low pressure. (5) drilling in complex formations and installing a support device on the drill pipe when necessary. Attention should be paid to underwater concrete pouring process 1 when the concrete is made of high-grade cement, attention should be paid to the relation between the initial setting time and the final setting time of the concrete and the time of the grouting of the single pile, and concrete retarder shall be added if necessary. The mixing ratio (especially the water cement ratio) and mixing time shall be strictly controlled at the construction site. Grasp the workability of concrete and slump of concrete to prevent segregation and blockage of concrete in the course of pouring. 2 buried pipe depth during initial grouting The provisions of China's JGJ94-94 standard, perfusion catheter at the bottom to the hole bottom distance should be 300 ~ 500mm, early irrigation catheter depth should be greater than or equal to 800mm. When calculating the initial filling amount of concrete, the individual construction unit only calculates the amount of concrete needed for the length of 1.3m pile, and calculates the amount of concrete accumulated in the pipe. The initial grouting capacity is not enough, and the buried pipe depth is not up to the standard value. On the other hand, the length of the pipe specification construction units for too little, the conduit piping installation difficulties, sometimes catheter to the hole bottom distance is too large, and the catheter installation personnel failed to notice the actual distance of cast-in-place concrete class, form the first pouring amount due to insufficient depth is not up to the standard value. At the beginning of V should be designed according to the amount of concrete filling pile diameter, pipe diameter, pipe length, installation hole mud density are calculated, and V is not less than V0+V1. V0 is the concrete quantity of 1.3m pile length, V0 = 1.2 * 1.3 PI D2/4 (unit: m3); theoretical filling coefficient of 1.2 piles; D design pile diameter (m). V1 is the concrete quantity accumulated in the early irrigation catheter, V1 = (H - d2/4) (P + 0.55 PI d) /2.4 (unit: m3); length H (m); D catheter installation - vessel diameter (m); P - mud hole density (t /m3); friction coefficient 0.55 - the inner wall of the conduit; 2.4 concrete density (t /m3). 3 concrete filling pipe Plugging mainly by catheter breaking causes of the leakage, catheter end from the bottom hole depth is too small, the completion of the two hole cleaning after pouring concrete for too long time, water hydrant is not standardized, concrete preparation quality, perfusion catheter depth is too large caused by pouring concrete at. The catheter before installation should be specifically responsible for the inspection, the naked eye and method of combining beat hearing examination, inspection items are the existence of joint catheter holes, holes and cracks of the catheter is sealed, the thickness of the catheter is qualified. If necessary, test the water pressure by assembling and check whether the catheter leaks or not. The distance between the bottom of the perfusion catheter and the bottom of the hole should be between 300 and 500mm, and the maximum value should be taken as much as possible under the condition that the initial grouting capacity of the grouting equipment is enough. Water hydrant to be carefully made, its diameter and roundness should meet the requirements, its length should be less than 200mm. After the completion of the second cleaning, the concrete shall be started immediately. If the concrete is delayed for some reason, the hole shall be cleaned again. Otherwise, it may cause the sand suspension in the hole to sink, and make the sediment at the bottom of the hole too thick, and cause the blockage of the water separation pipe to escape the pipe blockage. 4 pouring concrete process, reinforcement cage floating There are three main reasons for the rise of reinforced concrete cage in pouring concrete process: (1) the initial setting time and the final setting time of the concrete are too short, so that the concrete in the hole is too early to agglomerate, and when the concrete surface rises to the bottom of the reinforcing cage, the concrete block holds the reinforcing steel cage. (2) when the hole cleaning the mud hole suspended sand too much, in the process of concrete pouring sand back to sink in the concrete surface, the formation of sand layer is dense, and with the hole in the concrete increased gradually, when the sand up to the steel cage when they hold at the bottom of the reinforcement cage. (3) when the concrete is poured to the bottom of the reinforcing cage, the pouring speed is too fast, and the reinforcing steel cage rises. If the reinforcement cage floating, should immediately identify the causes, and take appropriate measures to prevent repeated incidents. 5, the pile concrete strength is low or concrete segregation The main reason of low strength of concrete or segregation of concrete is that concrete mix ratio is not strict, mixing time is not enough and cement quality is poor. It is an effective measure to prevent the concrete segregation and strength of the pile body to control the quality of the cement entering the storehouse strictly, control the concrete mix proportion of the construction site, master the mixing time and the workability of the concrete. 6 pile concrete slag or broken pile There are four main reasons for the concrete pile or broken pile in the pile body: (1) the amount of initial concrete is not enough, the depth of buried pipe is too small after the initial irrigation, or the pipe is not in the concrete. (2) the concrete pouring process, the tube length control is not allowed, the catheter drawn out of the concrete surface. (3) the initial setting time and the final setting time of concrete are too short, or the pouring time is too long, so that the upper part of concrete is caking, resulting in concrete slag inclusion. (4) when the hole cleaning the mud hole suspended sand too much, in the process of concrete pouring sand back to sink in the concrete surface, the formation of sedimentary sand, hinder the normal rise in concrete. When the concrete break through the sedimentary sand, sand and some scum encased in concrete. In serious cases, it may cause pipe blockage and cause the concrete to be interrupted. The depth of the buried pipe shall be controlled between 2~6 meters. If the grouting is smooth and the mud of the orifice is returned to normal, the buried pipe depth may be appropriately increased so as to increase the filling speed and shorten the concrete pouring time of the single pile. The concrete pouring process of extubation should be specifically responsible for the command, and respectively by theoretical calculation of concrete poured into the hole surface and the weight measured hole concrete surface, low value to control the length of the tube, ensure the catheter depth more than 2 meters. The pouring time of single pile concrete should be controlled at 1.5 times the initial setting time of concrete. 7 pile top concrete is not dense or strength is not up to the design requirements, the main reason is that the over irrigation height is not enough, too much slurry, and the concrete surface of the hole is not determined. For the pile diameter is less than 1000mm over filling pile, the pile length height of not less than 4%. For the pile with diameter > 1000mm, the height of the grouting is not less than 5% of the length of the pile. For large volume concrete pile, the pile top 10 meters of concrete should be adjusted with the ratio increase of gravel content, reduce the pile head laitance. In the final stage of the grouting, the determination of the concrete surface in the hole shall be determined by rigid cylinder sampling method.