A method for treating a bearing stratum cave at the bottom of a cast-in-place pile and a method for testing the effect thereof

Abstract

The application provides a method for treating and testing the effect of a solution cavity in a bearing stratum at the bottom of a cast-in-place pile, comprising the following steps: (1) drilling core sampling and detection of the cast-in-place pile by a core drilling method to check whether there is a solution cavity in the bearing stratum at the bottom of the pile; (2) tube wave detection from the bottom of the core hole to the bottom of the pile for the cast-in-place pile without the solution cavity to check the integrity of the bearing stratum at the bottom of the pile; (3) for the cast-in-place pile with the solution cavity in the bearing stratum, the filling in the solution cavity is first flushed clean, then high-pressure jet grouting is performed on the solution cavity in the bearing stratum to seal the solution cavity; (4) for the cast-in-place pile with the solution cavity found by the tube wave detection, a core hole is re-opened for sampling to find the position of the solution cavity, and the method of step (3) is adopted; (5) for the cast-in-place pile after the treatment of the bearing stratum at the bottom of the pile, a re-detection is performed at the original grouting hole position, the strength of the grouting body is detected, and the tube wave detection is performed on the new core hole to test the effect of the grouting reinforcement. The application increases the stability of the cast-in-place pile and reduces the safety hazards.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pile bottom bearing stratum defect problem processing construction in karst areas, and particularly relates to a method for processing and effect testing of a pile bottom bearing stratum karst cave of a cast-in-place pile. BACKGROUND

[0002] With the continuous development of engineering technology, the efficient construction of pile foundation makes it a common form of foundation in karst areas. The cast-in-place pile foundation mainly uses rock-socketed piles and auxiliary friction piles. Therefore, finding suitable and complete bedrock as a bearing stratum for rock-socketed pile foundation has become a problem that needs to be solved by many engineering and technical personnel. However, the geological conditions in karst areas are relatively complex, and the karst corrosion phenomenon is randomly distributed. The size and shape of the karst cave also have great differences. In some local areas, the development depth is extremely unstable, and the rock surface fluctuates greatly. Therefore, it is difficult to determine the complete bedrock.

[0003] In order to find the complete bedrock, before the construction of the pile foundation, the survey and design unit usually adopts two ways, i.e., "one pile one hole or multiple holes" advanced drilling and "one pile one hole" advanced drilling combined with tube wave detection. The "one pile one hole or multiple holes" advanced drilling means that the geology in the pile position range is pre-surveyed and drilled. The number of drilling holes is related to the pile diameter, and then the position of the complete bedrock is inferred according to the survey results. The "one pile one hole" advanced drilling combined with tube wave detection means that the geology in the center of the pile position is pre-surveyed and drilled to estimate the approximate depth of the complete bedrock, and then the tube wave detection is performed on the survey drilling hole in the center of the pile position to determine the position of the complete bedrock.

[0004] The "one hole or more holes" advanced drilling can infer the position of the complete bedrock by investigating the geological conditions of the drilling hole, but the result is related to the drilling result of the investigation drilling hole, and it cannot be determined whether there is a karst cave in the place not drilled within the pile diameter range, and there is a certain objective inclination of the drilling hole, and as the drilling depth increases, the possibility of the drilling hole deviating out of the pile position also increases, so that the error of the investigation result compared with the actual situation is large. The "one hole or more holes" advanced drilling combined with tube wave detection can determine the karst development within the pile diameter range by comprehensively determining the geological conditions of the investigation drilling hole and the tube wave signal, and can solve the shortcomings of the "one hole or more holes" advanced drilling, but the success rate and accuracy of the tube wave detection are related to the investigation drilling hole. For the string bead-shaped karst cave, the complete bedrock is speculated to be below the string bead-shaped karst cave, however, the hole is easy to collapse due to slurry leakage at the position of the string bead-shaped karst cave, the drill rod can be drilled down, but the tube wave probe and the PVC protection tube cannot be placed to the depth required to be detected, thereby reducing the success rate of the tube wave detection. Although the additional use of the steel casing can isolate the karst cave, the use length thereof is limited, when the karst cave is buried deep, the sidewall has a large friction on the steel casing, so that the force of the driving drill rod cannot be transmitted to the hole bottom, and then the drilling cannot continue, and the string bead-shaped karst cave has a serious phenomenon of soft and hard interbedded layers, the position of the karst cave is often soft filling or hole, and the shaking of the investigation drilling machine will make the drill rod swing back and forth, and it is easy to deviate to the soft filling or hole, so that the possibility of hole deviation will increase, and the tube wave detection signal has a certain range, when the investigation drilling hole deviates out of the pile diameter range under the influence of the objective verticality and the soft layer or hole of the karst cave, at this time, the tube wave detection is the complete bedrock outside the pile position, and the accuracy of the result is reduced. A large number of existing engineering examples show that after the above two ways are used, the karst development within the pile position range is still difficult to be determined, so that the pile bottom bearing layer may have unexplored karst caves, and there is a large safety hazard. SUMMARY

[0005] The present application provides a method for treating and testing the effect of karst cave in the pile bottom bearing layer of a cast-in-place pile, which comprehensively determines the development and integrity of the karst cave in the pile bottom bearing layer by combining the existing core drilling hole and tube wave detection result, then cuts, flushes and high-pressure sprays the karst cave in the pile bottom bearing layer, and finally tests the effect of the grouting by tube wave detection.

[0006] The technical scheme provided by the present application is a method for treating and testing the effect of karst cave in the pile bottom bearing layer of a cast-in-place pile, which comprises the following steps,

[0007] (1) According to the development of the karst cave in the geological investigation data of the construction site, the proportion and detection area of the cast-in-place pile core drilling method detection are determined, and the integrity of the pile body and the pile bottom bearing layer is investigated;

[0008] (2) The drilled core method is used to drill core sampling operation on the selected cast-in-place pile, and the existence of karst cave in the pile bottom bearing stratum of the cast-in-place pile is statistically analyzed;

[0009] (3) For the cast-in-place pile in which the bearing stratum has karst cave discovered by the drilled core method, the karst cave in the pile bottom bearing stratum discovered in the drilling core process is reinforced by reinforcement measure A, and the reinforcement measure A comprises the following steps: another hole is drilled for core sampling, and two grouting holes are formed in communication with the original drilled core hole and the karst cave, the karst cave in the two grouting holes is cut and washed by high-pressure water in turns until it is clean, the cement slurry is sprayed into the karst cave of the two grouting holes by using a high-pressure grouting pump in turns until the karst cave is filled, and the two grouting holes are closed by using orifice grouting in turns;

[0010] (4) The tube wave detection method is used to perform tube wave detection operation on the cast-in-place pile in which no karst cave is discovered by the remaining drilled core, and the detection range is from bottom to top from the bottom of the drilled core hole to the pile bottom, the integrity of the pile bottom bearing stratum is checked, and the existence of karst cave in the pile bottom bearing stratum of the cast-in-place pile is statistically analyzed by the tube wave signal;

[0011] (5) For the cast-in-place pile in which no karst cave is discovered by the tube wave detection, no karst cave treatment is performed, and only ordinary grouting and orifice grouting are used to close the drilled core hole, for the cast-in-place pile in which karst cave is discovered by the tube wave detection, a new hole is drilled for core sampling, and whether the new grouting hole has karst cave is observed, for the cast-in-place pile in which no karst cave is discovered by the new drilled core sampling, after the drilled core hole and the grouting hole are closed by ordinary grouting and orifice grouting, static load test is directly performed on the cast-in-place pile to test the bearing capacity, for the cast-in-place pile in which karst cave is discovered by the new drilled core sampling, the discovered karst cave in the pile bottom bearing stratum is reinforced by reinforcement measure B, and the reinforcement measure B comprises the following steps: the karst cave in the grouting hole is cut and washed by high-pressure water until it is clean, the cement slurry is sprayed into the karst cave of the grouting hole by using a high-pressure grouting pump until the karst cave is filled, and the grouting hole is closed by using orifice grouting;

[0012] (6) After the karst cave treatment of the pile bottom of the cast-in-place pile, re-drilling core sampling is performed on the original grouting hole by using the drilled core method, the strength of the grouting body is detected, and the tube wave detection of the range of the pile bottom bearing stratum is performed on the re-drilled core hole to test the effect of grouting reinforcement.

[0013] Further, the reinforcement measure A in step (3) is as follows:

[0014] a. The original drilled core hole is used as grouting hole one, and another drilled core hole is drilled in the pile diameter range symmetrically to the original drilled core hole to serve as grouting hole two, the core drilling machine is lifted off after drilling to the predetermined depth, the caterpillar type rotary jet drilling machine is opened to the hole position through the caterpillar, and the hole scanning operation of the two grouting holes is performed respectively to prevent the occurrence of hole collapse, and the number of hole scanning can be increased if necessary;

[0015] b. Clean the surface of the pile top, and use high-strength cement mortar to bury the orifice pipe at the orifice of the two grouting holes, and configure the corresponding detachable grout stop valve. After the strength of the cement mortar meets the construction requirements of orifice grouting, it can be used;

[0016] c. Install a grouting nozzle at the bottom of the grouting pipe. Through the caterpillar type rotary jet drilling machine, the grouting nozzle is sent to one of the grouting holes through a section of grouting pipe, and the other grouting hole is used as a drainage hole. Then, through the high-pressure grouting pump, high-pressure clean water is delivered, and the caterpillar type rotary jet drilling machine is used to lift the grouting pipe back and forth, so that the high-pressure clean water sprayed by the bottom grouting nozzle repeatedly cuts and washes the karst cave. Two grouting holes are cut and washed alternately until the return grout of the two grouting holes used as drainage holes is clean water, and the process can be stopped;

[0017] d. Pour cement into the mixing barrel and mix with water to make the required cement slurry. Then, the water supply pipe of the high-pressure grouting pump is connected to the cement mixing barrel from the clean water barrel. Through the high-pressure grouting pump, high-pressure cement slurry is delivered to the grouting hole where the grouting nozzle is located. At this time, the other grouting hole is used as a grout discharge hole and an open grout stop valve is installed. The caterpillar type rotary jet drilling machine is used to lift the grouting pipe back and forth, so that the high-pressure cement slurry sprayed by the bottom grouting nozzle fills the karst cave. When the overflow of the grout at the grout stop valve reaches the configured grout consistency, slowly lift the grouting pipe. After the grouting pipe is completely removed from the grouting hole, stop grouting. At this time, close the grout stop valve of the grout discharge hole, and install an open grout stop valve on the orifice pipe of the grouting hole used for grouting. Then, use the high-pressure grouting pump to pressurize the grouting hole used for grouting with thick cement slurry. After a period of stabilization, the orifice grouting is completed, and the two grouting holes are used alternately for high-pressure rotary jet grouting and orifice grouting;

[0018] e. Observe the setting condition before the cement slurry is finally set. Rotate the grouting holes to supplement the grout until all the grouting holes are full of grout, and the shrinkage during the setting process of the grout is offset.

[0019] Further, the specific steps of step (5) of re-drilling core sampling and reinforcement measure B are as follows:

[0020] a. Another drilling core hole is symmetrically opened within the pile diameter range. A new drilling hole is used as a grouting hole. After drilling to the predetermined depth and finding the karst cave, the drilling core drilling machine is lifted. The caterpillar type rotary jet drilling machine is opened to the hole position through the caterpillar, and the hole scanning operation of the grouting hole is performed to prevent hole collapse. If necessary, the number of hole scanning can be increased;

[0021] b. Clean the surface of the pile top, and use high-strength cement mortar to bury the orifice pipe at the orifice of the two grouting holes, and configure the corresponding detachable grout stop valve. After the strength of the cement mortar meets the construction requirements of orifice grouting, it can be used;

[0022] c. Install the grouting nozzle at the bottom of the grouting pipe, send the grouting nozzle to the grouting hole through the grouting pipe by the caterpillar rotary jet drilling machine, then deliver the high-pressure clean water by the high-pressure grouting pump, and use the caterpillar rotary jet drilling machine to lift the grouting pipe up and down to make the high-pressure clean water jetted by the bottom grouting nozzle repeatedly cut and clean the karst cave until the grouting hole returns to the grouting of clean water;

[0023] d. Pour the cement into the mixing barrel to mix with water to make the required cement slurry, then change the water supply pipe of the high-pressure grouting pump from the clean water barrel to the cement mixing barrel, deliver the high-pressure cement slurry to the grouting hole by the high-pressure grouting pump, and use the caterpillar rotary jet drilling machine to lift the grouting pipe up and down to make the high-pressure cement slurry jetted by the bottom grouting nozzle to fill the karst cave, when the grouting hole overflows, the slurry concentration is reached, slowly lift the grouting pipe, and stop grouting when the grouting pipe is completely out of the grouting hole, at this time, the opened stop valve is connected to the orifice pipe of the grouting hole, and the high-pressure grouting pump is used to pressurize the thick cement slurry in the grouting hole, and the orifice grouting is ended after a period of stabilization.

[0024] e. Install the grouting nozzle at the bottom of the grouting pipe again, deliver the high-pressure cement slurry by the high-pressure grouting pump, and use the caterpillar rotary jet drilling machine to send the grouting nozzle to the bottom of the core hole through the grouting pipe to jet and fill, when the hole liquid of the core hole orifice overflows, the slurry concentration is reached, at this time, the caterpillar rotary jet drilling machine is used to slowly lift the grouting pipe from the bottom of the hole, the high-pressure cement slurry is jetted by the bottom grouting nozzle to continue to fill the core hole, and the grouting is stopped when the grouting pipe is completely out of the core hole, at this time, the opened stop valve is connected to the orifice pipe of the core hole, and the high-pressure grouting pump is used to pressurize the thick cement slurry in the core hole, and the orifice grouting is ended after a period of stabilization.

[0025] f. Observe the setting condition before the cement slurry is finally set, supplement the grouting of the orifice until the orifice slurry is full, and offset the shrinkage during the setting process of the slurry.

[0026] Further, the detection proportion of the cast-in-place pile in step (1) is not less than 5% of the total number of cast-in-place piles, and the detection proportion of local areas is increased according to the development of the karst cave.

[0027] Further, the number of core holes detected by the core drilling method in step (2) is related to the diameter of the cast-in-place pile. When the pile diameter is ≤1m, the number of core holes is one, and the hole is opened at a position 10-15cm away from the center of the pile; when 1m

[0028] Further, the position of the core hole is reasonably arranged to avoid the steel bar, and the final hole of the core hole requires entering the pile bottom bearing stratum not less than three times of the pile diameter and not less than 5m, and when the karst cave is encountered, the karst cave bottom plate needs to be penetrated and at least 0.5m into the bedrock.

[0029] Further, the step (3) describes the case of one core hole, when the number of core holes is two or more, without new grouting hole, the existing core hole is directly used as the grouting hole, and each grouting hole is used for high-pressure rotary jet grouting and hole mouth pressure grouting in turn, among the two or more core holes, the core hole without karst cave is not used as the karst cave grouting hole, and only ordinary grouting and hole mouth pressure grouting are used to close the hole mouth.

[0030] Further, when the number of grouting holes in the step (3) is three or more, only two grouting holes are left for construction operation when cutting, cleaning, high-pressure grouting and hole mouth pressure grouting are carried out, and the remaining grouting holes are installed with closed stop valve in advance;

[0031] Further, in the step (4), when the number of core holes is two or more, the remaining core holes are closed by ordinary grouting and hole mouth pressure grouting, and only one core hole is left for tube wave detection to detect the integrity of the bearing stratum, and in the step (5), when the number of core holes is two or more, the newly opened grouting holes should be as evenly arranged as possible with the original core holes.

[0032] Further, in the steps (3) and (5), the high-pressure water pressure is 30MPa, the rotary jet speed is 10r / min, the grouting pipe lifting speed is 10cm / min, the cutting and cleaning section is 50cm above and below the karst cave position, the high-strength cement slurry with water-cement ratio of 0.6:1.0 and strength grade of 42.5 is used for high-pressure rotary jet grouting, the grouting pressure is 30MPa, the rotary jet speed is 15r / min, the grouting pipe lifting speed is 10cm / min, the rotary jet grouting section is 50cm above and below the karst cave position, and the grouting pressure is 2MPa, and the pressure is kept for 10min.

[0033] Further, in the step (5), the karst cave found by the tube wave detection method is small and locally distributed, so only one grouting hole is used to cut, clean and fill completely, and the original core hole is not used for karst cave grouting because no karst cave is found, and only ordinary grouting and hole mouth pressure grouting are used to close the hole.

[0034] Further, in the steps (3) and (5), the diameters of the core holes and the grouting holes are both 110mm, the final hole depth of the grouting holes in the steps (3) and (5) is consistent with that of the core holes, the grouting nozzle of the steps (3) and (5) is composed of a nozzle and a drill bit, and the bottom is closed, only the nozzle has a grouting outlet, which is installed at the bottom of the grouting pipe, and the grouting pipe needs to be checked for water before each section is installed to prevent blockage in the pipe.

[0035] Further, the step (6) retests the cast-in-place pile after 28 days of grouting completion, and for the karst cave found by the core drilling method, a grouting hole can be optionally re-drilled and re-inspected.

[0036] Further, after the cast-in-place pile treatment is completed, the karst development condition is analyzed again according to the results of the core drilling method and the tube wave detection, in combination with the geological survey data, and the detection proportion of the cast-in-place pile in the area where the pile bottom bearing layer has the karst cave is expanded.

[0037] Compared with the prior art, the beneficial effects achieved by the present application are:

[0038] The present application combines the core drilling method with the tube wave detection method, improves the success rate and accuracy of the tube wave detection, more completely explores, as far as possible, eliminates the cast-in-place pile with the karst cave in the pile bottom bearing layer, and performs high-pressure jet grouting treatment on the karst cave in the pile bottom bearing layer, finally, the effect is verified by the tube wave detection, which greatly improves the stability of the cast-in-place pile and reduces the safety hidden danger. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a construction process schematic diagram of the present application;

[0040] Figure 2 is a schematic diagram of high-pressure jet grouting;

[0041] Figure 3 and Figure 4 are a schematic diagram of orifice grouting and a local enlarged view of orifice grouting, respectively;

[0042] Figure 5 is a schematic diagram of tube wave detection;

[0043] Figure 6 is a front view of a grouting nozzle.

[0044] In the figure: 1 is a caterpillar type jet grouting drill; 2 is a soil layer; 3 is a rock layer; 4 is a karst cave; 5 is a cast-in-place pile; 6 is a grouting hole; 7 is a grouting hole; 8 is a grouting pipe; 9 is a grouting nozzle; 10 is an orifice pipe; 11 is a grouting valve; 12 is a high-pressure grouting pump; 13 is a stirring barrel; 14 is a variable diameter joint; 15 is a tube wave probe; 16 is a drill bit; 17 is a nozzle. DETAILED DESCRIPTION

[0045] The technical solutions of the present application will be described clearly and completely below in combination with the drawings of the present application. The technical solutions shown in the drawings are specific solutions of the embodiments of the present application, and are not intended to limit the scope of the claimed present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0046] In the description of the application, it should be understood that the terms "upper", "lower", "inner", "outer", "left", "right", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship commonly understood by those skilled in the art, and are only for the purpose of facilitating the description of the application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the application.

[0047] The pile bottom bearing stratum karst cave 4 of the cast-in-place pile 5 in the embodiment is plugged by the method of high-pressure rotary jet grouting, and finally treated by hole sealing with orifice grouting. For the pile bottom karst cave 4 found by the core drilling method, first, the buried depth of the karst cave 4 is determined, then a new drilling hole is drilled in the pile diameter range symmetrically to the original core hole, and the new drilling hole and the original core hole are used as two grouting holes 6 of the pile bottom bearing stratum karst cave; the orifice pipes 10 are embedded in the orifices of the two grouting holes 6 with high-strength cement mortar, and corresponding grout stop valves 11 are provided; the outer diameter of the orifice pipe 10 is consistent with the outer diameter of the grouting hole 6; the grouting nozzle 9 with a nozzle 17 and a drill bit 16 and a bottom closure is installed at the bottom of the grouting pipe 8, and a section of the grouting pipe 8 is connected to the rotary jet drill 1 and sent to the position of the karst cave 4 in one of the two grouting holes 6, at this time the other grouting hole 6 is used for drainage; the high-pressure grouting pump 12 is used to deliver high-pressure water, and the rotary jet drill 1 is used to lift the grouting pipe 8 back and forth, so that the high-pressure water jetted from the bottom grouting nozzle 17 repeatedly cuts and washes the karst cave 4, and the two grouting holes 6 are cut and washed alternately until the backflow of the grouting holes 6 used for drainage is clear water; according to the predetermined water-cement ratio, cement is added to the mixing barrel 13 to make the required cement slurry, then the water supply pipe of the high-pressure grouting pump 12 is connected to the cement mixing barrel 13 from the water tank, and the high-pressure cement slurry is delivered to the grouting hole 6 where the grouting nozzle 9 is located by the high-pressure grouting pump 12, at this time the other grouting hole 6 is used for grouting and the open grout stop valve 11 is installed; the rotary jet drill 1 is used to lift the grouting pipe 8 back and forth, so that the high-pressure cement slurry is jetted from the bottom grouting nozzle 17 to fill the karst cave 4, when the overflow of the grout stop valve 11 reaches the configuration slurry consistency, the grouting pipe 8 is slowly lifted, and the grouting is stopped after the grouting pipe 8 is completely lifted out of the grouting hole 6, at this time the grout stop valve 11 of the drainage hole 7 is closed, and the open grout stop valve 11 is installed on the orifice pipe 10 of the grouting hole 6 used for grouting, then the high-pressure grouting pump 12 is used to pressurize the grouting hole 6 used for grouting, and the orifice grouting is completed after a period of stabilization, and the high-pressure rotary jet grouting and orifice grouting are alternately performed in the two grouting holes 6.For the pile bottom karst cave 4 discovered by tube wave detection method, first determine the depth of the cave 4 revealed by tube wave signal, then symmetrically drill core holes in the range of pile diameter, use the new core drilling rig to drill a new hole as a grouting hole 6, after drilling to the predetermined depth and discovering the cave 4, start high pressure jet grouting; The original core hole does not participate in the cave grouting, only ordinary grouting and orifice grouting can be used to seal the hole; The orifice of the core hole and the grouting hole 6 is buried with a high-strength cement mortar orifice pipe 10, and is equipped with a corresponding grout valve 11, the outer diameter of the orifice pipe 10 is consistent with the outer diameter of the core hole and the grouting hole 6; The grouting nozzle 9 with nozzle 17 and drill bit 16 and closed bottom is installed at the bottom of the grouting pipe 8, and a section of grouting pipe 8 is connected to the caterpillar type jet grouting rig 1 to send it to the cave 3 position of the grouting hole 6; Through the high pressure grouting pump 12 to transport high pressure water, and use the caterpillar type jet grouting rig 1 to lift the grouting pipe 8 back and forth, so that the high pressure water jetted out by the bottom grouting nozzle 17 repeatedly cuts and washes the cave 4, and the return grouting of the grouting hole 6 is water, which can stop; According to the predetermined water-cement ratio, cement is added to the mixing barrel 13 to make the required cement slurry, then the water supply pipe of the high pressure grouting pump 12 is connected to the cement mixing barrel 13 from the water tank, the high pressure cement slurry is transported to the grouting hole 6 by the high pressure grouting pump 12, and the grouting pipe 8 is lifted up and down by the caterpillar type jet grouting rig 1, so that the high pressure cement slurry is jetted out by the bottom grouting nozzle 17 to fill the cave 4, when the grouting hole 6 liquid overflows, the grouting pipe 8 is slowly lifted out of the grouting hole 6 after the grouting pipe 8 is completely lifted out of the grouting hole 6, the grouting can be stopped at this time, the opened grout valve 11 is connected to the orifice pipe 10 of the grouting hole, and the high pressure grouting pump 12 is used to pressurize the grouting hole 6 with thick cement slurry, and the orifice grouting of the grouting hole 6 can be completed after a period of stabilization; Then install the grouting nozzle 9 at the bottom of the grouting pipe 8, transport the high pressure cement slurry by the high pressure grouting pump 12, and send the grouting nozzle 9 to the bottom of the core hole through a section of grouting pipe 8 by the caterpillar type jet grouting rig 1; When the hole liquid of the core hole orifice overflows, the grouting pipe 8 is slowly lifted from the bottom of the hole by the caterpillar type jet grouting rig 1, so that the high pressure cement slurry is jetted out by the bottom grouting nozzle 17 to continue to fill the core hole, and the grouting is stopped when the grouting pipe 8 is completely lifted out of the core hole, the opened grout valve 11 is connected to the orifice pipe 10 of the core hole at this time, and the high pressure grouting pump 12 is used to pressurize the core hole with thick cement slurry, and the orifice grouting of the core hole can be completed after a period of stabilization.

[0048] The tube wave detection method in this embodiment of the invention is used to assist in locating the pile bottom karst cave 4 that was not detected by the core drilling method, and to verify the effect of grouting the karst cave in the bearing layer. When the core drilling method fails to detect the karst cave 4, the core hole is first cleaned, and then the tube wave probe 15 is placed in the core hole until it reaches the bottom of the hole. Then, the tube wave transmitter is turned on to emit pulse signals to the surrounding rock strata 3, and the vibration waveform signals reflected back from the rock strata 3 are received simultaneously. At this time, the tube wave probe 15 is slowly pulled from the bottom of the hole to the bottom of the pile to explore whether the karst cave 4 exists and its specific burial depth, providing a drilling reference for the newly opened grouting hole 6. After the karst cave 4 at the bottom of the cast-in-place pile 5 has been grouted and cured for 28 days, the original grouting hole 6 can be re-drilled at a specific depth to test the strength of the grout body, and tube wave detection is performed again from the bottom of the hole to the bottom of the pile to verify the effect of grouting.

[0049] This invention provides a method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness. Specifically, using one core drilling operation as an example, the construction steps are as follows:

[0050] (1) Based on the development of karst cave 4 in the geological survey data of the construction site, determine the proportion and testing area of ​​cast-in-place pile 5, and determine the pile position and pile bottom elevation of the cast-in-place pile 5 that need to be tested.

[0051] (2) Core drilling was used to drill and sample the pile body and bearing stratum of cast-in-place pile 5. The diameter of the core drilling hole was 110 mm. During drilling, the length of the concrete of cast-in-place pile 5, the thickness of the sediment at the pile bottom, the lithology of the bearing stratum at the pile bottom, and the drilling speed were accurately recorded. The core drilling hole was required to penetrate into the bearing stratum at least three times the pile diameter and at least 5 m. When encountering karst cave 4, it was also necessary to penetrate the bottom plate of karst cave 4 and penetrate into the intact bedrock for at least 0.5 m. The core drilling method was used to statistically analyze each cast-in-place pile 5 where karst caves were found, and the specific burial depth of each cast-in-place pile 5 karst cave 4 was recorded.

[0052] (3) Reinforcement measures A were taken to treat the cast-in-place pile 5, which was found to have karst caves by core drilling:

[0053] a. Use the original core hole as grouting hole 6-1. Also, within the pile diameter range, use the core drilling machine to drill a new hole with a diameter of 110mm to be used as grouting hole 6-2. The final hole requirements are the same as the final hole requirements of the original core hole.

[0054] b. After drilling to the designated depth, hoist the core drilling rig and move the crawler-type rotary grouting rig 1 to the hole position via the crawler. Then, perform hole sweeping operations on the two grouting holes 6 to prevent hole collapse. If necessary, the number of hole sweeping operations can be increased.

[0055] c. The pile top surface is cleaned, and the high-strength cement mortar is used to embed the orifice pipe 10 with an outer diameter of 110 mm at the orifice of the two grouting holes 6, and the corresponding detachable grout valve 11 is configured. After the strength of the cement mortar meets the construction requirements of the orifice grouting, it can be used;

[0056] d. Check the flow through the nozzle 17 and drill teeth 16 and the bottom closed grouting nozzle 9 and grouting pipe 8, then install the grouting nozzle 9 at the bottom of the grouting pipe 8, and send the grouting nozzle 9 to the position of the solution cavity 4 in the grouting hole one through a section of grouting pipe 8 by the track-type rotary jet drilling machine 1, and the grouting hole two is used as a drainage hole;

[0057] e. Block the water supply pipe, connect the grouting pipe 8 with the grouting pipe 8, open the high-pressure grouting pump 12, let the air in the grouting pump be exhausted first, then put the water supply pipe into the water bucket, transport high-pressure clean water through the high-pressure grouting pump 12, and use the track-type rotary jet drilling machine 1 to lift the grouting pipe 8 up and down, so that the high-pressure clean water jetted by the bottom grouting nozzle 17 repeatedly cuts and washes the solution cavity 4, the pressure of the high-pressure clean water is 30 MPa, the rotary jet speed is 10 r / min, the lifting speed of the grouting pipe 8 is 10 cm / min, and the cutting and washing section is the position of the solution cavity 4 and its extension of 50 cm above and below;

[0058] f. When the water discharged from the grouting hole two is basically clear, the grouting pipe 8 and the grouting nozzle 9 are removed and placed in the grouting hole two to cut and wash the solution cavity 4 in the same way, and at this time the grouting hole one is used as a drainage hole. The two grouting holes are cut and washed alternately until the return grout of the two grouting holes used as drainage holes is clear water, and then the process is stopped;

[0059] g. Pour the cement into the mixing bucket 13, add water and mix to make high-strength cement slurry with a water-cement ratio of 0.6:1.0 and a strength grade of 42.5;

[0060] h. Then change the water supply pipe of the high-pressure grouting pump 12 from the water bucket to the cement mixing bucket 13, transport high-pressure cement slurry to the grouting hole where the grouting nozzle 9 is located through the high-pressure grouting pump 12, at this time the other grouting hole is used as a grouting hole and the opened grout valve 11 is installed, use the track-type rotary jet drilling machine 1 to lift the grouting pipe 8 up and down, so that the high-pressure cement slurry jetted by the bottom grouting nozzle 17 fills the solution cavity 4, the grouting pressure is 30 MPa, the rotary jet speed is 15 r / min, the lifting speed of the grouting pipe is 10 cm / min, and the rotary jet grouting section is the position of the solution cavity 4 and its extension of 50 cm above and below;

[0061] i. When the grout overflowing from the stop valve 11 of the grouting hole used for grout discharge reaches the consistency of the prepared grout, slowly lift the grouting pipe 8. Grouting can be stopped only after the grouting pipe 8 is completely pulled out of the grouting hole. At this time, close the stop valve 11 of the grouting hole used for grout discharge, and install the open stop valve 11 on the orifice pipe of the grouting hole used for grouting. Then, connect the grout delivery pipe of the high-pressure grouting pump 12 to the stop valve 11 of the grouting hole used for grouting through the reducing joint 14, and pressurize it with concentrated cement grout at a pressure of 2MPa. After stabilizing the pressure for 10 minutes, the orifice grouting can be ended. The two grouting holes are alternately subjected to high-pressure jet grouting and orifice grouting.

[0062] j. Observe the solidification of the cement grout before its final setting, and add grout to each orifice in turn until all orifices are filled with grout to offset the shrinkage during the solidification process.

[0063] (4) The tunneling pile 5 for which no karst cave 4 was found in the remaining core drilling was conducted using the tunneling wave detection method. The detection range was from the bottom of the existing core hole to the bottom of the pile to determine the burial depth of karst cave 4, and to treat it through reinforcement measure B:

[0064] a. The original core hole will not be used for grouting of karst cave 4. In addition, within the pile diameter range, a new 110mm diameter hole will be drilled using the core drilling rig core to be used as a grouting hole. The final hole requirements are the same as those of the original core hole.

[0065] b. After drilling to the designated depth, hoist the core drilling rig and move the crawler-type rotary grouting rig 1 to the hole position via the crawler. Then, perform hole sweeping operations to prevent hole collapse. If necessary, the number of hole sweeping operations can be increased.

[0066] c. Clean the surface of the pile top, and use high-strength cement mortar to embed a hole pipe 10 with an outer diameter of 110mm at the opening of the core hole and the grouting hole, and configure a corresponding detachable grout stop valve 11. The grouting can be completed after the strength of the cement mortar meets the construction requirements of the hole grouting.

[0067] d. Check the flow between the grouting nozzle 9 with nozzle 17 and drill teeth 16 and the grouting pipe 8 with the bottom closed. Then install the grouting nozzle 9 at the bottom of the grouting pipe 8 and send the grouting nozzle 9 to the karst cave position in the grouting hole through the grouting pipe 8 section by section by section of the crawler rotary jet drilling rig 1.

[0068] e. Block the water supply pipe, connect the slurry pipe with the grouting pipe 8, open the high-pressure grouting pump 12, let the air in the grouting pump be exhausted first, then put the water supply pipe into the clean water bucket, transport high-pressure clean water through the high-pressure grouting pump 12, and use the caterpillar type rotary jet drilling machine 1 to repeatedly lift and lower the grouting pipe 8, so that the high-pressure clean water jetted out by the bottom grouting nozzle 17 repeatedly cuts and washes the karst cave 4. The pressure of the high-pressure clean water is 30 MPa, the rotary jet speed is 10 r / min, the lifting speed of the grouting pipe is 10 cm / min, and the cutting and washing section is the position of the karst cave 4 and the extension of 50 cm above and below the position;

[0069] f. Stop when the grouting hole returns to clean water;

[0070] g. Pour cement into the mixing bucket 13, add water to mix to prepare high-strength cement slurry with a water-cement ratio of 0.6:1.0 and a strength grade of 42.5;

[0071] h. Then change the water supply pipe of the high-pressure grouting pump 12 from the clean water bucket to the cement mixing bucket 13, transport high-pressure cement slurry to the grouting hole where the grouting nozzle 9 is located through the high-pressure grouting pump 12, use the caterpillar type rotary jet drilling machine 1 to repeatedly lift and lower the grouting pipe, so that the bottom grouting nozzle 17 sprays high-pressure cement slurry to fill the karst cave. The grouting pressure is 30 MPa, the rotary jet speed is 15 r / min, the lifting speed of the grouting pipe is 10 cm / min, and the rotary jet grouting section is the position of the karst cave 4 and the extension of 50 cm above and below the position;

[0072] i. When the hole liquid overflowing from the orifice of the grouting hole reaches the configuration slurry consistency, slowly lift the grouting pipe 8, and stop grouting when the grouting pipe 8 is completely removed from the grouting hole. At this time, the opened stop valve 11 is connected to the orifice pipe 10 of the grouting hole, then the slurry pipe of the high-pressure grouting pump 12 is connected to the stop valve 11 through the reducing joint 14, and the concentrated cement slurry with a pressure of 2 MPa is stored, and the pressure is stabilized for 10 minutes to end the orifice grouting;

[0073] j. Install the grouting nozzle 9 at the bottom of the grouting pipe 8 again, use the caterpillar type rotary jet drilling machine 1 to send the grouting nozzle 9 to the bottom of the core hole through a section of grouting pipe 8, connect the slurry pipe of the high-pressure grouting pump 12 with the grouting pipe 8, transport the cement slurry with a pressure of 1 MPa through the high-pressure grouting pump 12 for jet grouting, when the hole liquid overflowing from the orifice of the core hole reaches the configuration slurry consistency, at this time, use the caterpillar type rotary jet drilling machine 1 to slowly lift the grouting pipe 8 from the bottom of the hole, so that the bottom grouting nozzle 17 sprays cement slurry with a pressure of 1 MPa to continue grouting the core hole, stop grouting when the grouting pipe is completely removed from the core hole. At this time, the opened stop valve 11 is connected to the orifice pipe 10 of the core hole, the slurry pipe of the high-pressure grouting pump 12 is connected to the stop valve 11 through the reducing joint 14, and the concentrated cement slurry with a pressure of 2 MPa is stored, and the pressure is stabilized for 10 minutes to end the orifice grouting;

[0074] k.Observing the solidification of the cement paste before the final setting, and supplementing the paste in each orifice in turn until all the orifices are full of paste, and the shrinkage in the solidification of the paste is offset.

[0075] (4) After the grouting is completed, the grouting nozzle 8, grouting pipe 7, high-pressure grouting pump 12 and other equipment are flushed to prevent the equipment from being blocked.

[0076] (5) After the cast-in-place pile 5 is grouted for 28 days, the core drilling method is used to reopen the hole and take samples at the original grouting hole position, the strength of the grouted body is detected, and the tube wave detection of the pile bottom bearing layer range is performed on the reopened core drilling hole to test the grouting reinforcement effect.

[0077] In the above embodiment, the number of core drilling holes is used as an example, and the number is related to the pile diameter. For two or more core drilling holes, two grouting holes can be selected for high-pressure rotary jet grouting and orifice grouting.

[0078] The above describes the principles and advantages of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present application, which should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness, characterized in that, Includes the following steps: (1) Based on the development of karst caves in the geological survey data of the construction site, determine the proportion and testing area of ​​the core drilling method for cast-in-place piles, and explore the integrity of the pile body and the bearing layer at the bottom of the pile; (2) Core drilling was used to sample the selected cast-in-place piles and statistical analysis was conducted on the presence of karst caves in the bearing stratum at the bottom of the piles. (3) For cast-in-place piles where the bearing layer is found to have karst caves by core drilling, reinforcement measures A are used to reinforce the karst caves in the bearing layer at the bottom of the pile discovered during core drilling. The reinforcement measures A include the following steps: drilling another hole to take core samples, forming two grouting holes that are connected to the original core drilling hole to form karst caves, using high-pressure clean water to cut and clean the karst caves in the two grouting holes in turn until they are clean, using a high-pressure grouting pump to spray cement slurry into the karst caves in the two grouting holes in turn until the karst caves are filled, and using grouting at the orifice to seal the two grouting holes in turn. (4) Use the tube wave detection method to conduct tube wave detection operations on cast-in-place piles where no karst caves were found in the remaining core drill. The detection range is from bottom to top, from the bottom of the core drill hole to the bottom of the pile. Check the integrity of the bearing layer at the bottom of the pile and count the tube wave signals to show the presence of karst caves in the bearing layer at the bottom of the cast-in-place pile. (5) For cast-in-place piles where no karst caves are found by pipe wave detection, no karst cave treatment is carried out. The core hole is sealed by ordinary grouting and borehole grouting. For cast-in-place piles where karst caves are found by pipe wave detection, the hole is reopened for core sampling to observe whether there are karst caves in the new grouting hole. For cast-in-place piles where no karst caves are found by re-core sampling, after sealing the core hole and grouting hole with ordinary grouting and borehole grouting, a static load test is directly performed on this type of cast-in-place pile to test its bearing capacity. For cast-in-place piles where karst caves are found by re-core sampling, the karst caves in the bearing layer of the pile bottom are reinforced by reinforcement measure B. The reinforcement measure B includes the following steps: using high-pressure water to cut and clean the karst caves in the grouting hole until they are clean; using a high-pressure grouting pump to spray cement slurry into the karst caves in the grouting hole until the karst caves are filled; and sealing the grouting hole by borehole grouting. (6) After the karst cave at the bottom of the cast-in-place pile is treated, a re-inspection is carried out. The core drilling method is used to re-drill core samples at the original grouting hole position to test the strength of the grout body. The pipe wave detection is carried out on the core hole at the bottom of the pile bearing layer to verify the effect of grouting reinforcement.

2. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 1, characterized in that, The specific reinforcement measure A in step (3) is as follows: a. Use the original core drill hole as grouting hole one. Simultaneously drill a new hole within the pile diameter range, using the core drilling rig, as grouting hole two. After drilling to the predetermined depth, hoist the core drilling rig and move the tracked jet grouting rig to the hole position. Perform hole cleaning operations on both grouting holes to prevent hole collapse; increase the number of cleaning operations if necessary. b. Clean the surface of the pile top, and embed orifice pipes at the openings of both grouting holes using high-strength cement mortar, and install corresponding removable grout stop valves. The grouting can proceed once the cement mortar strength meets the requirements for orifice grouting. c. Install grouting nozzles at the bottom of the grouting pipe. Use a tracked rotary jet grouting rig to deliver the grouting nozzles through sections of grouting pipe to one of the grouting holes. The other grouting hole is used for drainage. High-pressure clean water is then pumped in using a high-pressure grouting pump. The tracked rotary jet grouting rig is used to raise and lower the grouting pipe back and forth, causing the high-pressure clean water from the bottom grouting nozzles to repeatedly cut and clean the karst cave. The two grouting holes are used alternately for cutting and flushing until the grout returned from both holes when used for drainage is clear water. d. Pour cement into a mixing tank, add water, and mix to prepare the required cement slurry. Then, connect the water supply pipe of the high-pressure grouting pump from the clean water tank to the cement mixing tank. The high-pressure grouting pump delivers the high-pressure cement slurry to the grouting hole where the grouting nozzle is located. Meanwhile, another grouting hole is used for grout discharge, and an open stop valve is installed. A crawler-type rotary jet grouting rig is used to raise and lower the grouting pipe, causing the bottom grouting nozzle to spray high-pressure cement slurry to irrigate the karst cave. When the overflowing liquid at the stop valve reaches the prepared slurry consistency, the grouting pipe is slowly raised. Grouting can only be stopped after the grouting pipe is completely pulled out of the grouting hole. At this point, the stop valve of the discharge hole is closed, and an open stop valve is installed on the orifice pipe of the grouting hole used for grouting. Then, the high-pressure grouting pump is used to pressurize the grouting hole with concentrated cement slurry. After a period of stabilization, the orifice grouting can be stopped. The two grouting holes are alternately subjected to high-pressure rotary jet grouting and orifice grouting. e. Observe the solidification of the cement grout before its final setting, and replenish the grout to each orifice in turn until all orifices are filled with grout to offset the shrinkage during the solidification process.

3. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 2, characterized in that, The specific steps of re-drilling core samples and reinforcement measure B in step (5) are as follows: a. In addition, within the pile diameter range, symmetrically drill a new hole as a grouting hole using a core drilling rig. After drilling to the predetermined depth and discovering the karst cave, lift the core drilling rig and move the tracked jet grouting rig to the hole position via the track. Then, perform hole sweeping operations on the grouting hole to prevent hole collapse. If necessary, the number of hole sweeping operations can be increased. b. Clean the top surface of the pile, and use high-strength cement mortar to embed the orifice pipe at the opening of the core hole and the grouting hole. The grouting can be completed after the strength of the cement mortar meets the construction requirements of the orifice grouting. c. Install grouting nozzles at the bottom of the grouting pipe, and send the grouting nozzles through the grouting pipe sections to the grouting holes using a crawler-type rotary grouting drill. Then, use a high-pressure grouting pump to deliver high-pressure clean water, and use the crawler-type rotary grouting drill to raise and lower the grouting pipe back and forth, so that the high-pressure clean water ejected from the bottom grouting nozzles repeatedly cuts and cleans the karst cave until the grouting hole returns grout to clean water. d. Pour cement into a mixing tank, add water and mix to make the required cement slurry. Then, switch the water supply pipe of the high-pressure grouting pump from the clean water tank to the cement mixing tank. The high-pressure cement slurry is delivered to the grouting hole through the high-pressure grouting pump. The crawler-type rotary jet drilling rig is used to raise and lower the grouting pipe back and forth, so that the bottom grouting nozzle sprays out high-pressure cement slurry to irrigate the karst cave. When the grout overflows from the grouting hole and reaches the prepared slurry consistency, the grouting pipe is slowly raised. Grouting can be stopped only after the grouting pipe is completely pulled out of the grouting hole. At this time, the open grout stop valve is connected to the orifice pipe of the grouting hole, and the high-pressure grouting pump is used to pressurize the grouting hole with concentrated cement slurry. After stabilizing for a period of time, the orifice grouting can be stopped. e. Next, install grouting nozzles at the bottom of the grouting pipe, and deliver high-pressure cement slurry through a high-pressure grouting pump. Use a crawler-type rotary grouting drill to send the grouting nozzles through sections of grouting pipe to the bottom of the core hole for injection. When the slurry overflows from the core hole opening and reaches the prepared slurry consistency, use the crawler-type rotary grouting drill to slowly lift the grouting pipe from the bottom of the hole, so that the bottom grouting nozzles can spray high-pressure cement slurry to continue grouting the core hole. Stop grouting when the grouting pipe is completely pulled out of the core hole. At this time, connect the opened grout stop valve to the core hole opening pipe, and use a high-pressure grouting pump to pressurize the core hole with concentrated cement slurry. After stabilizing for a period of time, the grouting at the hole opening can be ended. f. Observe the solidification of the cement grout before its final setting, and add grout to the orifice until the orifice is full of grout to counteract the shrinkage during the solidification process.

4. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 2, characterized in that, The number of core holes detected by the core drilling method in step (2) is related to the diameter of the cast-in-place pile. When the pile diameter is ≤1m, the number of core holes is one, which is drilled at a position 10-15cm away from the center of the pile; when 1m < pile diameter ≤1.6m, the number of core holes is two, which are drilled at 1 / 3 and 2 / 3 of the pile diameter. When the pile diameter is greater than 1.6m, the number of core drilling holes should not be less than three, and they should be evenly distributed within the pile location. The final drilling hole should be at least three times the pile diameter and at least 5m into the bearing layer at the bottom of the pile. When encountering a karst cave, it should penetrate through the bottom plate of the karst cave and enter the bedrock at least 0.5m.

5. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 2, characterized in that, The step (3) describes the case where there is only one core hole. When there are two or more core holes, there is no need to open new grouting holes. The existing core holes can be used as grouting holes directly. Each grouting hole is subjected to high-pressure jet grouting and hole-mouth grouting in turn. Among the two or more core holes, the holes where no karst cave is found are not used as karst cave grouting holes. Only ordinary grouting and hole-mouth grouting are performed to seal the hole.

6. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 5, characterized in that, When the number of grouting holes in step (3) is three or more, during cutting and cleaning, high-pressure grouting and grouting at the hole opening, only two grouting holes should be left for construction work in turn, and the other grouting holes should be equipped with closed grouting valves in advance. In step (4), when the number of core holes is two or more, the excess core holes should be sealed by ordinary grouting and orifice grouting, leaving only one core hole for pipe wave detection to check the integrity of the bearing layer. In step (5), when the number of core holes is two or more, the newly opened grouting holes should be arranged as evenly as possible with the original core holes.

7. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 3, characterized in that, In steps (3) and (5), the high-pressure clean water pressure is 30 MPa, the jet grouting speed is 10 r / min, the grouting pipe lifting speed is 10 cm / min, the cutting and cleaning section is the location of the karst cave and its vertical extension is 50 cm, high-strength cement grout with a water-cement ratio of 0.6:1.0 and a strength grade of 42.5 is used for high-pressure jet grouting, the grouting pressure is 30 MPa, the jet grouting speed is 15 r / min, the grouting pipe lifting speed is 10 cm / min, the jet grouting section is the location of the karst cave and its vertical extension is 50 cm, the grout holding pressure is 2 MPa, and the pressure is stabilized for 10 min.

8. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 1, characterized in that, The karst caves discovered by the tube wave detection method in step (5) are small and locally distributed. Therefore, only one grouting hole is needed to cut, clean and fill them completely. Since no karst caves were found in the original core hole, it is not used for karst cave grouting. Ordinary grouting and grouting at the hole opening are sufficient to seal the hole.

9. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 1, characterized in that, In step (6), the cast-in-place pile is re-inspected 28 days after the grouting is completed, and for any karst caves discovered by the core drilling method, one grouting hole is randomly selected for re-core drilling and re-inspection.

10. The method for treating karst caves in the bearing stratum at the bottom of cast-in-place piles and verifying its effectiveness according to claim 3, characterized in that, The diameter of the core hole and the grouting hole in steps (3) and (5) is 110mm. The final hole depth of the grouting hole in steps (3) and (5) is required to be consistent with that of the core hole. The grouting nozzle in steps (3) and (5) consists of a nozzle and a drill tooth, and the bottom is closed, leaving only one grout outlet. It is installed at the bottom of the grouting pipe. The grouting pipe must be checked for water flow before each section is installed to prevent blockage inside the pipe.

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