Kneeling for graduation thesis "Research on some problems of underwater cast-in-place pile construction (hole cleaning, wall protection, preventing reinforcing cage from floating, hole collapse and pile breaking)" Common drilling problems (including hole cleaning) and their solutions are as follows: 1 1. 1 Various drilling methods may cause hole collapse. The characteristics of hole collapse are that the water level in the hole suddenly drops, small bubbles appear at the orifice, the slag output does not increase significantly, and the rig load increases significantly. 1 1. 1. Reasons for hole collapse ① The relative density of mud is not enough, and other mud performance indicators do not meet the requirements, so that a solid mud skin is not formed on the hole wall. (2) Because the mud (or water) is not replenished in time after slag discharge, or the river is in high tide, or confined water appears in the hole, or the hole passes through gravel and other strong permeable layers, the water in the hole is lost, and the head height in the hole is not enough. (3) The casing is buried too shallowly, and the orifice at the lower end leaks or collapses, or the ground near the orifice is softened by water immersion, or the drilling rig directly contacts the casing, so that the orifice collapses due to vibration and expands into a larger hole collapse. ④ Drilling footage in soft sand is too fast. ⑤ It is suggested that the rotating speed is too fast and the idle time is too long. ⑥ If the water head is too high, the hole wall will ooze slurry or the bottom of casing will form reverse perforation. ⑦ After hole cleaning, the relative density and viscosity of mud decreased, and the mud (or water) was not replenished in time after the hole cleaning mud was sucked by the suction fan, so that the water level in the hole was lower than the groundwater level. ⑧ Improper hole cleaning operation, the water supply nozzle directly washes the hole wall, and the hole cleaning time is too long or the hole cleaning pause time is too long. Pet-name ruby collision hole wall when hanging into the steel skeleton. 1 1. 1.2, hole collapse prevention ① When drilling in loose silt or quicksand, the footage speed should be controlled, and mud with high relative density, viscosity and colloid ratio or high quality mud should be selected. (2) When the orifice collapses, the liner can be removed immediately and the borehole can be backfilled. The liner can be buried again and then the borehole can be drilled. (3) In case of hole collapse, find out the hole collapse position, and backfill the mixture of sand and clay (or gravel and loess) to 1m-2m above the hole collapse. If the hole collapse is serious, all the holes should be backfilled, and then drill holes after backfilling. (4) When cleaning the hole, a special person shall be appointed to fill mud (or water) to ensure the necessary head height in the hole. It is best not to insert the water supply pipe directly into the borehole, but to slow down the water through the sink or pool and then flow into the borehole to avoid scouring the borehole wall. Mud suction machine should be straightened to prevent it from touching the hole wall. Excessive wind pressure shall not be used and shall not exceed 1.5- 1.6 times of the water column pressure in the borehole. (5) When hoisting into the steel skeleton, the drilling center should be inserted vertically to prevent touching the hole wall. 1 1.2 Various drilling methods may cause borehole deviation. 1 1.2. 1, causes of deviation ① large boulder or exploration stone encountered during drilling ② inclined soft and hard strata junction, and the rock surface was inclined to drill; Or drilling into sandy pebble layers with different particle sizes, the bit is unevenly stressed. (3) When reaming is large, the drill bit will swing to one side. (4) The rig base is not placed horizontally or uneven settlement and displacement occur. ⑤ The drill pipe is bent and the joint is not straight. 1 1.2.2, prevention ① When installing the drilling rig, make the turntable and the base level, and the flange of the lifting pulley, the clamping hole for fixing the drill pipe and the center of the casing should be in a vertical line, and check and correct them frequently. ② Because the active drill pipe is long, the upper part swings too much when rotating. It is necessary to add a guide frame to the drilling rig, and control the faucet on the rod to drill holes in the center along the guide frame. (3) Drill pipe joints should be checked one by one and adjusted in time. When the active drill pipe is bent, it should be adjusted with jack in time. 1 1.3 falling objects may occur during drilling. 1 1.3.65438+ ② Poor joint of drill pipe or thread slipping. (3) The motor wiring is wrong, the drilling rig rotates reversely, and the drill pipe is loose. (4) The steering ring, steering sleeve and other welds are disconnected. (5) Inadvertent operation, falling into wrenches, crowbars, etc. 1 1.3.2, Precautions ① Before spudding, the falling objects in the hole should be removed, scattered iron pieces can be sucked by electromagnet, and larger falling objects and drilling tools can also be salvaged by grab cone, and then the casing mouth should be capped. ② Check drilling tools, drill pipes, wire ropes and coupling devices frequently. 1 1.3.3, treatment methods After drilling, find out the situation in time. If the drill bit is buried by sediments or collapsed rocks, we should first clean the drill hole so that fishing tools can contact the drill pipe and drill bit. 1 1.4 In reverse circulation and positive circulation rotary drilling, drilling paste and buried drilling often occur. The characteristic of drilling paste is slow penetration or even pump stop when drilling in fine soil. Prevention and treatment methods: For the rotary drilling rig with positive and negative circulation, the mud pack can be removed, the relative density and viscosity of mud can be adjusted, the pumping capacity can be appropriately increased, and a proper amount of sand and gravel can be put into the hole to solve the problem of mud pack sticking, and a bit cone with small scraper teeth and large slurry outlet can be selected; If drilling mud is serious, stop drilling and remove drilling mud. Check and calculate the inner diameter of drill pipe, the size of drilling slag inlet and outlet and slag discharge equipment. 1 1.5 reaming and reducing reaming are common, and the surface aperture is generally too large. When the ground water is moving, the soil is loose, or the drill bit swings too much, reaming is easy to happen. The causes of reaming are the same as those of hole collapse, ranging from reaming to hole collapse. If only partial collapse and reaming occur in the hole, and the hole can still reach the design depth, there is no need to deal with it, but the concrete pouring quantity is greatly increased. If drilling is affected by continued collapse after reaming, it shall be treated as a hole collapse accident. Shrinkage, that is, the extraordinary reduction of pore size, is generally manifested as the signs of sticking, lifting the drill bit or lifting the horn during drilling. There are two reasons for reducing the diameter: one is that the bit is not repaired in time, and the bit with serious wear often drills a hole slightly smaller than the designed pile diameter; The other is because there is soft plastic soil (commonly known as rubber soil) in the stratum, which shrinks the pore size after swelling in water. Shrinkage may occur in various drilling methods. In order to prevent shrinkage cavity, the former should repair the worn bit in time, and the latter should use high-quality mud with low water loss rate to protect the wall, and must turn quickly and slowly, and drill again for two or three times; Or hoist the drill cone with a hoist, and repeatedly sweep the hole up, down, left and right to enlarge the hole diameter until the reduced part meets the design requirements. For holes with shrinkage cavity, the reinforcing cage should be poured immediately after it is in place to avoid shrinkage or exposure.

1 1.6 plum blossom hole (or cross hole) often appears when drilling with impact cone, and the punched hole is not round, which is called plum blossom hole or cross hole. 1 1.6. 1. Cause ① The cone top steering device fails, so that the impact cone does not rotate and always impacts up and down in one direction. ② The relative density and viscosity of mud are too high, and the impact rotation resistance is too large, which makes it difficult to rotate the bit. (3) During operation, the wire rope is too loose or the stroke is too small, the impact cone just rises and falls, and the bit rotation time is insufficient or little, so the impact position cannot be changed. (4) Uneven layers, such as boulders and accumulation layers, are prone to rock exploration, resulting in local hole walls protruding and holes not being round. 1 1.6.2, preventive measures ① check the flexibility of the steering device frequently and repair or replace the failed steering device in time. ② Choose mud with proper viscosity and relative density, and remove slag in time. (3) When using a low stroke, each impact section uses a high stroke impact, and alternately impacts to trim the hole shape. (4) After the plum blossom hole appears, it can be backfilled with mixed clay of sawdust and pebbles, and then compacted again. 1 1.7 cone sticking often occurs when percussive cone drilling. 1 1.7. 1. Reason ① The drill hole formed a plum blossom shape, and the punch cone was stuck by the narrow part. (2) If the punch cone is not welded in time, the drilling diameter will gradually decrease, and the welded punch cone is larger, and it is easy to get stuck in high stroke. (3) The probe stone extending into the hole is not big enough to be broken, and the cone foot or cone top is stuck. ④ Stones or other objects fall from the orifice, and the punch cone is stuck. ⑤ In the clay layer, the impact stroke is too high and the mud is too thick, so that the impact cone is absorbed. ⑥ If the rope is too loose, the cone will topple and hold against the hole wall.

1 1.7.2. Treatment method ① If the drill bit is stuck in the plum blossom, if there is room for the cone head to move downward, the drill bit can be rotated downward and lifted in the direction of larger diameter. You can also loosen the wire rope and let the drill cone rotate at an angle, so it is possible to lift the drill cone out. (2) The drill should not be stuck forcibly to prevent hole collapse and drilling. Bottom-up docking method should be adopted to tap the stones at the drilling point, sometimes making the drill move up and down, or getting rid of the sticking point, or making the falling stones fall. (3) Put the fishhook or fishing line into the hole with thick steel wire rope, lift the punch hook backward, and swing it up and down, left and right several times at the same time or alternately with the big rope for testing, and sometimes lift the punch cone out. (4) During fishing, continue to stir the mud to prevent the mud from burying the drill bit. ⑤ Use other tools, such as a small punch cone and a small slag bucket, to impact into the hole, so as to squeeze the stuck stone into the hole wall, or lift the punch cone after it hits the stuck point. But keep the rope stable to prevent the cone from falling suddenly. ⑥ Run compressed air or high-pressure water pipe into the hole, aim at one side of the stuck cone or suck the cone for a period of time, and then release the stuck point and push it out forcefully. ⑦ Align the drill bit with the hole wall with specially processed tools. ⑧ When the above methods are ineffective, you can try the underwater blasting PO method. Generally, waterproof ZHA medicine (less than 1kg) can be put into the hole, placed at the bottom of the cone along the chute of the cone, and then detonated to loosen the stuck cone, and then lifted by the hoist and chain block at the same time.

1 1.8 Common external rod fracture of rotary drilling rig. 1 1.8.65438+ (2) The improper rotation speed during drilling increases the torsional or bending stress on the drill pipe, thus causing the drill pipe to break. (3) The drill pipe is used for too long, and the joint is damaged or worn too much. (4) The geology is hard and the footage is too fast, which makes the drill pipe overloaded. ⑤ A foreign body appeared in the hole, which suddenly increased the resistance and failed to stop drilling in time. 1 1.8.2. Prevention and treatment ① Don't use drill pipes with severe bending. It is required that the connection of each drill pipe and the connection thread between the drill pipe and the drill bit are intact, and the drill pipe joint connected with the screw sleeve should have anti-loosening facilities to prevent reverse rotation and looseness. (2) The drilling speed should be controlled during drilling. Be careful when you encounter hard and complicated geology. (3) During drilling, always check the wear of various parts of the drilling tool and whether the joint strength is sufficient. Do not meet the requirements, it should be replaced in time. (4) If there is any foreign body during drilling, it must be treated first before drilling. ⑤ If the drill pipe has been broken, you can salvage the drill pipe according to the above salvage method. And check the reason, switch to a new or large drill pipe to continue drilling. 1 1.9 mud loss in well 1 1.9 1. Reasons for slurry leakage ① When drilling in gravel or quicksand with strong water permeability, especially in the stratum with groundwater flowing, dilute slurry leaks from the hole wall. (2) The liners are buried too shallow, and the backfill soil is not compacted enough, resulting in slurry leakage at the blade root. (3) The liner is poorly made and the joints are not tight, which leads to slurry leakage. (4) The water head is too high, and the water column pressure is too high, so that mud oozes from the hole wall. 1 1.9.2, treatment method ① All rotary drilling rigs in the first case should use thick or high-quality mud to drill holes. The impact drilling rig can add thick mud mixed with flaky and pebbles or backfill clay for repeated impact to strengthen the wall protection. (2) It belongs to casing leakage, and should be handled according to the provisions on casing manufacture and burial in the above specifications. If the slurry leakage at the joint is not serious, divers can plug the joint with cotton and wadding. In case of serious water leakage, the lining should be dug out and buried again after repair. -.Sealing failure 12. 1. 1 Accident causes and preventive measures (1) The distance between the bottom of the conduit and the bottom of the hole is too high or too low. Cause: Due to calculation error, the distance between the lower opening of the conduit and the bottom of the hole is too high or too low. Too high makes the first batch of concrete not enough to be buried under the conduit (above 1m). Too low makes it difficult for the first batch of concrete to fall, resulting in mud mixed with concrete. Preventive measures: accurately measure the length and number of each catheter, and check the hole depth and the total length of the catheter. The assembled conduit can also be directly lowered to the bottom of the hole, and the length can be checked with each other. The first batch of concrete is not enough. Cause: Due to calculation error, the first batch of concrete was not enough, and pipe burying failed. Precautionary measures: carefully calculate and recheck the first batch of concrete according to the aperture and conduit diameter. (3) The quality of the first batch of concrete is poor. Reason: the workability of the first batch of concrete is too poor, and it is difficult to convert the slurry. Or slump is too large, resulting in segregation. Preventive measures: do a good job in mix design and strictly control the workability of concrete. (4) the catheter enters the slurry. The sealing performance of the catheter is poor. After the first batch of concrete was poured, excessive external mud pressure penetrated into the conduit, resulting in the mixing of concrete and mud. 12.10.2 treatment method after the first batch of concrete back sealing fails, the conduit should be shelved, the reinforcing cage should be hoisted, and the hole should be cleaned immediately. 12.2 grouting stopped due to material supply and equipment failure. 12.2. 1 accident causes and preventive measures: due to equipment failure, the supply of concrete materials was interrupted for a long time, resulting in concrete condensation and broken piles. Precautionary measures: the process capability should be evaluated before construction, and some equipment should be considered for standby; There should be an emergency plan for accidents. 12.2.2 treatment method (1) If the broken pile is deep from the ground, consider lifting the reinforcing cage to re-form the hole. (2) If the broken pile is shallow from the ground, pile extension can be used. (3) If the original hole cannot be used, fill the pile after backfilling. 12.3 causes and preventive measures of hole collapse during grouting 12.3. 1: hole collapse occurred during grouting due to improper hole cleaning, too thin mud and collision with hole wall when placing reinforcing cage. Preventive measures: See section11.1.1. 12.3.2 treatment method (1) If the hole collapse is not serious, grouting can be continued and the progress can be accelerated appropriately. (2) If it is impossible to continue pouring, it should be backfilled in time and re-bored. 12.4 the catheter is emptied and falls off. 12.4. 1 cause of accident and prevention (1) causes of catheter emptying: due to measurement and calculation errors, the catheter was emptied when pouring concrete, and the pipe was filled with mud; Or the buried depth of the conduit is too small, and mud flows into the conduit. Preventive measures: carefully measure and recheck the hole depth and catheter length; The buried depth of the conduit should take an appropriate conservative value. ⑵ Reason for dropping the pipe: the connection of the pipe joint does not meet the requirements; The conduit is hung on the reinforcing cage and pulled off by force. Caution: Carefully reconnect the catheter connector after taking out the catheter each time; When the buried depth of the catheter is large, the catheter should be removed in time. 12.4.2 treatment method (1) When the concrete surface is deep from the ground, it should be re-perforated. (2) The concrete surface is shallow from the ground, so the pile extension method can be adopted. 12.5 concrete is difficult to float during pouring, and there is no frost boiling phenomenon. 12.5.65438+2 poor workability of concrete. (3) The buried depth of the conduit is too large. (4) At the end of grouting, because the height of concrete column in the conduit is reduced, the overpressure is reduced. 5) The consistency of mud and muck outside the conduit increases, and the relative density increases. 12.5.2 Remedial measures: (1) Lift the catheter to reduce the buried depth of the catheter. ⑵ Extend the conduit and increase the height of concrete column in the conduit. (3) Water can be added into the hole to dilute the mud, and part of the precipitated soil can be taken out. 12.6 insufficient filling height 12.6. 1 accident cause and prevention: inaccurate measurement; The pile head reserve is too small. Preventive measures: various methods can be used to ensure accuracy; The reserved amount of over-irrigation at the pile head can be appropriately increased. 12.6.2 treatment method: dig the pile head, and then take the pile. -