High-pressure jet grouting pile construction method for making overflow dam waterproof curtain in high pebble geology

Abstract

The invention relates to the technical field of concrete construction, in particular to a high-pressure jet grouting pile construction method for making an overflow dam waterproof curtain in high pebble geology. Determining the position of the hole in the construction area according to a design drawing; when the impact hole forming depth reaches 1 / 2 of the design depth, clay is added to the 1 / 4 position of the design depth, and then water is added; the percussion bit performs percussion hole forming again to the designed depth; uniformly stirring fine-grained soil and backfilling the fine-grained soil to the ground height to form a backfilling area; triple-pipe-method high-pressure jet grouting is conducted in the backfill area, when the designed pile top height is reached or the grout overflowing phenomenon occurs on the ground, jet grouting is stopped, a pipeline is cleaned, and one high-pressure jet grouting pile is completed; and the other high-pressure jet grouting piles are completed according to the steps in sequence according to the design. The uniform and continuous curtain pile body is formed, the integrity and the high anti-seepage performance are achieved, the safety and stability of engineering are ensured, the construction process is simplified, and the pile forming efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete construction, and more specifically, to a construction method of high-pressure jet grouting piles for making a cut-off curtain of an overflow dam in a high-pebble geology. Background Technique

[0002] High-pressure jet grouting piles are widely used in the engineering field as cut-off curtains for foundation pits and are applicable to soil layers such as silt, silty clay, cohesive soil, silt, sandy soil, artificial fill, etc.

[0003] The high-pressure jet grouting pile is to drill a hole to the required depth by an engineering drill (or a hole-leading and jet-grouting integrated machine), lower the grouting pipe equipped with a horizontal nozzle to the designed elevation by a high-pressure jet grouting trolley, and use high-pressure equipment to eject the slurry from the nozzle at a certain pressure. The high-pressure jet impacts and cuts the soil mass, destroys the soil structure within a certain range, and the slurry is stirred and mixed with the soil for solidification. As the grouting pipe rotates and lifts, a cylindrical pile body is formed. After solidification, a consolidated body with a cylindrical shape, certain strength, and adjacent pile bodies biting into one body is formed in the soil mass. This process plays the role of water stopping and soil reinforcement.

[0004] In the prior art, the Chinese invention patent with the patent number CN111042167A provides a construction method of a high-pressure jet grouting pile cut-off curtain, including the following steps: S1 ground treatment; S2 measurement and lofting; S3 rig positioning; S4 drilling to the designed depth; S5 high-pressure jet grouting; S6 rig relocation; S7 pile formation detection. This invention adopts a secondary pile-forming method, first sprays the clay layer, and then performs high-pressure jet grouting piles after the clay layer tends to be stable, preventing the concrete from being directly contacted with groundwater and being corroded and simultaneously playing an anti-seepage role.

[0005] The Chinese invention patent with the patent number CN104631480A discloses a method for constructing a cut-off curtain for a deep foundation pit using a high-pressure jet grouting rig. The method described in this invention aims at geological layers with difficult hole-forming such as silt, cohesive soil, loess, sandy soil, artificial fill, as well as pebble layers and mudstone layers. By installing the grouting pipe and the air injection pipe inside the drill rod of the CFG rig and modifying the drill bit of the CFG rig into a down-the-hole hammer drill, a construction technology of directly spraying slurry to form piles after hole-forming is adopted.

[0006] However, the above two methods are not applicable to hard geological layers such as granite, limestone, dense pebble layers, and boulder layers (particle size > 20 cm). The high-pressure jet cannot effectively cut, it is difficult to form piles, or large boulders hinder the mixing of slurry and soil, which may block the injection holes or cause the pile body to shift, and easily lead to the discontinuity of the pile body.

[0007] In the water ecological comprehensive treatment project of the Yinzhuang-Wu'an Railway Bridge section in Qinshui County, Jincheng City, after the trial pile of the jet grouting pile curtain of the overflow weir was completed, through excavation inspection, the pile forming situation was not ideal. The specific situation is as follows: The diameters of pebbles and gravel are relatively large, and the stone content is 60% - 75%. The pile forming effect is that there is only pure cement within a range of 20 - 30 cm around the drill hole, and basically no pure cement slurry can be seen outside. Visually observed, the cement slurry cannot wrap the surrounding pebbles or gravel, and cannot effectively form a continuous curtain pile body with a width meeting the design requirements.

[0008] This geological condition is basically composed of pebbles and gravel. Among them, the proportion of 50 cm - 60 cm is about 20%, the proportion of 30 cm - 40 cm is as high as about 60%, and the proportion of below 20 cm is about 20%. The overall geological stone content far exceeds 50%. The stone content increases from west to east (right bank - left bank). The geology below the excavation surface is still uncertain, and the geology is complex. According to the "Construction Technical Regulations for High-Pressure Jet Grouting Piles", the construction of high-pressure jet grouting piles under this geological condition is extremely difficult and risky, and it is difficult to ensure the uniformity and continuity of the pile body.

[0009] Based on the working mechanism of high-pressure jet grouting piles, in the construction of ancient river channels in water conservancy projects, the construction method of high-pressure jet grouting pile pilot holes cannot achieve the anti-seepage effect. During the construction of pilot holes, when large pebbles or boulders are encountered in the stratum, the pilot hole drill bit penetrates through the boulders, resulting in the boulders or pebbles obstructing the injection of slurry to the back of the pebbles or boulders during the jet grouting and lifting process of the grouting pipe, and the soil within the designed treatment range cannot be fully stirred. After construction, some un-stirred soil layers form leakage channels, and a closed water-stop curtain cannot be formed, seriously affecting the water-stop effect. Summary of the Invention

[0010] The present invention aims to at least solve one of the technical problems existing in the prior art. For this purpose, the object of the present invention is to provide a construction method of high-pressure jet grouting piles for making a water-stop curtain for an overflow dam in high-pebble geology. The specific steps of the construction method are as follows: S1. According to the design drawings in the construction area, carry out measurement, positioning, layout, and marking work to determine the positions of the holes; S2. Conduct the first impact hole-forming operation at the determined hole positions. When the hole depth reaches 1 / 2 of the designed depth, stop the operation, add clay to the hole to 1 / 4 of the designed depth, and then add the corresponding proportion of water volume to the hole; S3. The impact drill bit conducts the impact hole-forming operation again until the designed depth; S4. Stir the fine-grained soil evenly and load it into the hole, and tamp and compact it once every 2 meters until it is backfilled to the ground height to form a backfill area; S5. Conduct high-pressure rotary jet grouting by the triple-tube method in the backfill area. When the designed pile top height is reached or slurry overflows on the ground surface, immediately stop the rotary jet grouting work of the current pile, pull out the rotary jet pipe and clean the pipeline, and one high-pressure rotary jet grouting pile is completed. S6. Complete the remaining high-pressure rotary jet grouting piles in sequence according to the above S2 to S5 as designed.

[0011] Preferably, in S2, the ratio is hole depth: clay depth: water depth = 2:1:0.1.

[0012] Preferably, in S4, the fine-grained soil is stirred evenly to become homogeneous soil, and a test pile is made to measure the slurry injection volume, which is convenient for determining parameters during the construction of subsequent engineering piles.

[0013] Preferably, in S5, the borehole diameter of the high-pressure rotary jet grouting by the triple-tube method is φ146mm, and the overall impact drilling process with a casing bit is adopted. A PVC pipe with a diameter of 100mm or a jet pipe is lowered into the casing; ensure normal slurry return and gushing during the jetting process, and use a bit with a diameter 20mm larger than the outer diameter of the jet pipe; ensure the borehole is vertical, and for every 5 meters of drilling, a spirit level is required to measure the horizontal of the fuselage and the vertical direction of the vertical shaft.

[0014] Preferably, in S5, before grouting by the triple-tube method high-pressure rotary jet grouting, measure the length of the jet pipe and confirm that the center line of the nozzle is consistent with the direction of the jet pipe.

[0015] Preferably, in S5, for grouting, first prepare the slurry. Use ordinary Portland cement with a strength grade of P.042.5, and the water-cement ratio of the high-pressure jet grouting slurry is 1:1; the mixing time of the ordinary mixer is not less than 90s, and the mixing time of the high-speed mixer is not less than 30s. The slurry is used after being sieved and used up within 4 hours from the start of preparation.

[0016] Preferably, in S5, for the high-pressure rotary jet grouting by the triple-tube method, first send high-pressure water, then send cement slurry and compressed air; during jetting, first reach the predetermined jetting pressure and slurry injection volume, and then gradually lift the grouting pipe. The overlapping length of the grouting pipe lifted in sections shall not be less than 1mm.

[0017] Preferably, in S5, for the high-pressure rotary jet grouting by the triple-tube method, the high-pressure jet grouting slurry works continuously in the borehole. When the jet pipe reaches the designed depth, start jetting cement slurry and compressed air, and then stand still in place for 1 to 3 minutes. When the jetting pressure and slurry injection quantity reach the specified values and the slurry flows out of the hole, carry out jetting operations from bottom to top. When the designed height is reached, stop jetting and pull out the water jet pipe, stop lifting at the formation interface, stand still and jet for 5 - 10 minutes and increase the slurry supply volume. When the water-cement ratios of the slurry are 1:1 and 0.6:1, the corresponding slurry densities are 1.5g / cm³ and 1.6g / cm³ respectively.

[0018] Preferably, in step S5, static pressure filling grouting is carried out in the sunken injection holes by the triple tube method high-pressure jet grouting until the slurry surface is stable.

[0019] Preferably, in step S6, the construction between two adjacent high-pressure jet grouting piles is carried out at least 48 hours apart.

[0020] The beneficial effects of the present invention are as follows: The present invention adopts the impact drill hole-forming process to break the pebbles or boulders within the range of the rotary drilling pile, reduce the pebble particle size, and improve the formation conditions; by breaking the large-size pebbles, the obstruction of the formation to the cement slurry is reduced, enabling the cement slurry to better penetrate and wrap the surrounding formation, and improving the continuity and integrity of the pile formation. After the impact drill hole is formed, homogeneous fine-grained soil is backfilled to optimize the formation structure. At the same time, by precisely proportioning the cement slurry and the fine-grained soil, the fluidity and wrapping property of the cement slurry are improved.

[0021] The backfilling of the fine-grained soil makes the formation more uniform, enabling the cement slurry to better penetrate and wrap the pebbles or gravels. On the premise of ensuring the design anti-seepage requirements, the amount of cement slurry is optimized, reducing the waste of cement slurry, lowering the material cost, and at the same time ensuring the anti-seepage performance and strength of the curtain pile body, forming a continuous curtain pile body that meets the design requirements.

[0022] Through the impact drill hole-forming and the backfilling of fine-grained soil, the formation conditions are improved, enabling the high-pressure jet grouting pile to be effectively constructed in the formation with a high stone content; expanding the applicable range of the high-pressure jet grouting pile, enabling it to be applied to more projects with complex geological conditions, and improving the generality and practicability of the technology. The present invention forms a uniform and continuous curtain pile body with integrity and high anti-seepage performance, ensuring the safety and stability of the project, simplifying the construction process, and improving the pile-forming efficiency; reducing the rework rate, improving the construction efficiency, and ensuring the project quality and progress. The solution of the present invention has high practicability and popularization value, and is particularly suitable for projects with complex geological conditions similar to high stone content.

[0023] The additional aspects and advantages of the present invention will become apparent in the following description or be understood through the practice of the present invention. Specific Embodiments

[0024] In order to be able to more clearly understand the above-mentioned objects, features, and advantages of the present invention, the present invention will be further described in detail below with reference to specific embodiments. It should be noted that, without conflict, the embodiments of the present application and the features in the embodiments can be combined with each other.

[0025] Many specific details are set forth in the following description in order to fully understand the present invention. However, the present invention can also be implemented in other ways different from the description herein. Therefore, the protection scope of the present invention is not limited by the specific embodiments disclosed below.

[0026] S1. According to the design drawings in the construction area, carry out measurement, positioning, setting out and marking work to determine the positions of the holes. S2. Conduct the first impact hole-forming operation at the determined hole positions. When the hole depth reaches 1 / 2 of the design depth, stop the operation, add clay to the hole to 1 / 4 of the design depth, and then add the corresponding proportion of water (hole depth: clay depth: water depth = 2:1:0.1). S3. The impact drill bit conducts the impact hole-forming operation again until the design depth is reached. Through the impact drill bit and the drill body, the water and clay with the corresponding ratio are extruded to make the clay reach a certain strength and adhere tightly to the hole wall, further improving the hole wall stability and reducing the hole collapse rate. S4. Stir the fine-grained soil excavated from the river channel evenly to become homogeneous soil, make test piles, and measure the grouting volume to facilitate the determination of parameters during the construction of subsequent engineering piles. Place a funnel at the hole opening, and use an excavator to load the evenly stirred fine-grained soil into the hole. Ram and compact it once every 2 meters with an impact drill (the bottom is modified into a flat plate) until it is backfilled to the ground height to form a backfill area. S5. Conduct high-pressure jet grouting by the triple-tube method in the backfill area. When the design pile top height is reached or slurry overflows on the ground, immediately stop the jet grouting work of the current pile, pull out the jet grouting pipe and clean the pipeline, and one high-pressure jet grouting pile is completed. The borehole diameter is φ146mm. The overall impact drilling process with a casing drill bit is adopted. After drilling to the pile bottom elevation, the casing and drill pipe are pulled out integrally. A 100mm diameter PVC pipe or a jet grouting pipe is lowered into the casing. The applicable pressure situation is judged by the fragmented PVC pipe. Before drilling, measure and layout the holes according to the design drawings, and mark the pile number, hole number, serial number, and the elevation of each hole opening. The main drill pipe of the drill rig is accurately aligned with the backfill area, and a spirit level is used to measure the horizontal and vertical directions of the machine body to ensure the stability of the drill rig. To ensure normal backflow and gushing of slurry during the jetting process, a drill bit with a diameter 20mm larger than the outer diameter of the jet grouting pipe is used. To ensure the verticality of the borehole, every 5 meters of drilling, a spirit level is needed to measure the horizontal of the machine body and the vertical direction of the vertical axis. When installing the drill rig, it should be adjusted strictly according to the requirements of the drawings. The hole position deviation is less than 5cm, and the hole bottom deviation slope is less than 1%.

[0027] Before grouting, measure the length of the injection pipe to confirm whether the center line of the nozzle is consistent with the direction of the injection pipe, and mark scales on the injection pipe; before constructing the high-pressure jet grouting pile, it is necessary to conduct a ground trial spray to ensure the precise adjustment of the spray direction and swing angle; the performance of the grouting pump should be suitable for the type and concentration of the grouting slurry, its rated working pressure should exceed 1.2 times the maximum grouting pressure, the pressure fluctuation range should be controlled below 20% of the grouting pressure, and it must have sufficient slurry discharge capacity and stable working performance; ensure that the grouting pipeline can withstand 1.2 times the maximum grouting pressure, and install pressure gauges at the grouting pump, grouting orifice and inlet pipeline to ensure safety, ensure that there are sufficient pressure values at each part, and ensure that the pressure value of each link is greater than or equal to the design requirements to prevent accidents caused by pipeline leakage; after the ground trial spray passes the acceptance, measures should be taken when lowering the injection pipe to prevent the nozzle from getting stuck.

[0028] Prepare the grouting slurry. The type of slurry stirred should be coordinated with the slurry discharge capacity of the grouting pump, and it should be ensured that the slurry is evenly and continuously mixed to ensure the continuous slurry supply requirement of the high-pressure jet grouting pile; for high-pressure rotary jet grouting, ordinary Portland cement with a strength grade of P.042.5 is used, and the water-cement ratio of the high-pressure jet slurry is 1:1; the mixing time of the ordinary mixer is not less than 90s; the mixing time of the high-speed mixer is not less than 30s. The slurry should be screened before use, and it is advisable to use it within 4h from the start of preparation to use; various slurries must be fully mixed, determine the density, temperature and other parameters of the slurry and make records; when the ambient temperature is lower than 10°C, it shall not exceed 5h; when the ambient temperature is higher than 10°C, it shall not exceed 3h; when the storage time of the slurry is greater than the effective time, the strength grade should be reduced for use or disposed of as waste slurry. The temperature of the slurry should be maintained at 5°C to 40°C; the weighing of the slurry-making materials can be carried out by mass or volume measurement method, but the error should be controlled within a range not exceeding 5%; before using the slurry, it is necessary to check the slurry delivery pipeline and pressure gauge to ensure that the slurry can be smoothly sprayed into the formation; when appropriate admixtures and additives are added to the cement slurry to form a composite slurry, it should be determined through experiments.

[0029] For the high-pressure rotary jet of the triple-tube method, first send high-pressure water, then send cement slurry and compressed air; during spraying, the predetermined spraying pressure and slurry supply volume should be reached first, and then gradually lift the grouting pipe. The overlapping length of the segmented lifting of the grouting pipe shall not be less than 100mm.

[0030] Triple-tube method high-pressure jet grouting. Check that the grouting pipeline has descended to the designed height. After the nozzle reaches the designed height, insert the nozzle to the pre-determined depth. After passing the supervision acceptance, start the high-pressure jet grouting. Using the jet grouting technology, make the jet pipe move in a rotating and rising motion to form a columnar pile in the formation; both air and slurry should be continuously transported. The high-pressure grouting slurry works continuously in the borehole. When the jet pipe reaches the designed depth, start jetting the cement slurry and compressed air (usually sent in after 30 seconds), and then stand still in place for 1 to 3 minutes. When the jet pressure and the grouting quantity reach the specified values and the slurry flows out of the hole mouth, carry out the jetting operation from bottom to top at the preset lifting, rotating or swaying speed. When reaching the designed height, stop jetting and lift out the water jet pipe; the lifting speed should depend on the formation and the backflow situation. Stop lifting at the formation boundary, statically jet for 5 - 10 minutes and increase the slurry supply; during the jetting process, it is necessary to follow the instructions of the supervisor and regularly test the density of the cement slurry. When the water-cement ratio of the slurry is 1:1 and 0.6:1, the corresponding slurry densities are 1.5 g / cm³ and 1.6 g / cm³ respectively; during the jetting process, always pay attention to and check the pressure of the mud / water pump, slurry flow rate, pressure, air pressure and air volume of the air compressor, drilling rig rotation speed, lifting speed and slurry consumption to ensure that these factors can meet the requirements. At the same time, during the construction process, the operation process curve should be recorded and plotted in a timely manner.

[0031] During the high-pressure jet grouting process, if situations such as a sudden drop or rise in pressure, or abnormal backflow concentration or backflow volume at the hole mouth occur, stop the construction in a timely manner to find out the reasons and carry out corresponding treatments; when connecting and disassembling the jet pipe, it should be carried out quickly to avoid the occurrence of hole collapse or pipe blockage; after connecting and disassembling the pipe, the position of the lowered pipe should be 0.5 m lower than the original stop jetting height, and then carry out secondary jetting overlap to ensure the vertical continuity; when the high-pressure jet is interrupted due to certain reasons, stop jetting in a timely manner and record the interrupted depth to resume as soon as possible; when a mechanical failure occurs, try to shorten the downtime; during the construction process, if the slurry jetting is insufficient and affects the designed diameter of the body, carry out re-jetting; when dealing with large-area slurry leakage or gushing, the condition of the soil layer, the overall effect of the jet grouting and the rationality of the jet grouting process parameters can be understood in a timely manner by observing the jetting state.

[0032] Filling and re-injection: After the jetting work is completed, the slurry will solidify and separate out water, resulting in a depression on the surface of the coagulated body. It is necessary to carry out static pressure filling grouting in the sunken jet holes until the slurry surface is stable. When jetting in the clay layer or silt layer, do not re-inject the gushing slurry. During the recording of the re-injection process, it is necessary to record the re-injection time, number of times, grouting volume, amount of cement used and the quality of the re-injection.

[0033] S6. Complete the remaining high-pressure jet grouting piles in sequence according to the design. Construction shall be carried out with at least a 48-hour interval between two adjacent high-pressure jet grouting piles.

[0034] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, various modifications and changes can be made to the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. Construction method of high-pressure rotary jet grouting piles for cut-off curtain of overflow dam in high cobble geology, characterized in that: The specific steps of the construction method are as follows: S1. According to the design drawings in the construction area, carry out measurement, positioning, setting out and marking work to determine the positions of the holes; S2. Conduct the first impact hole-forming operation at the determined hole positions. When the hole depth reaches 1 / 2 of the designed depth, stop the operation, add clay to the hole to 1 / 4 of the designed depth, and then add the corresponding proportion of water volume to the hole; S3. The impact drill bit conducts the impact hole-forming operation again until the designed depth; S4. Stir the fine-grained soil evenly and fill it into the hole, and compact it by ramming every 2 meters until it is backfilled to the ground height to form a backfill area; S5. Carry out high-pressure jet grouting by the triple-tube method in the backfill area. When the designed pile top height is reached or slurry overflows on the ground, immediately stop the jet grouting work of the current pile, pull out the jet grouting pipe and clean the pipeline, and one high-pressure jet grouting pile is completed; S6. According to the design, complete the remaining high-pressure jet grouting piles in sequence according to the above S2 to S5.

2. The construction method of high-pressure jet grouting piles for the water-stop curtain of an overflow dam in high-pebble geology according to claim 1, characterized in that: In S2, the ratio is hole depth: clay volume depth: water volume depth = 2:1:0.

1.

3. The construction method of high-pressure jet grouting piles for the water-stop curtain of an overflow dam in high-pebble geology according to claim 1, characterized in that: In S4, the fine-grained soil is stirred evenly to become homogeneous soil, and a test pile is made to measure the slurry injection volume to facilitate the determination of parameters during the construction of subsequent engineering piles.

4. The construction method of high-pressure jet grouting piles for the cut-off curtain of an overflow dam in high-pebble geology according to claim 1, characterized in that: In S5, the borehole diameter of the high-pressure jet grouting by the triple-tube method is φ146mm, and the overall impact drilling process with a casing drill bit is adopted. A PVC pipe with a diameter of 100mm or a jet grouting pipe is lowered into the casing; ensure normal backflow and gushing of slurry during the jetting process, and use a drill bit with a diameter 20mm larger than the outer diameter of the jet grouting pipe; ensure the verticality of the borehole. Every 5 meters of drilling, a spirit level is required to measure the horizontal of the fuselage and the vertical direction of the vertical axis.

5. The construction method of high-pressure jet grouting piles for the water-stop curtain of the overflow dam in high cobble geology according to claim 1, characterized in that: In S5, before the high-pressure jet grouting by the triple-tube method, measure the length of the jet grouting pipe to confirm that the center line of the nozzle is consistent with the direction of the jet grouting pipe.

6. The construction method of high-pressure jet grouting piles for the cut-off curtain of an overflow dam in high-pebble geology according to claim 5, characterized in that: In S5, prepare the slurry for grouting first. Use ordinary Portland cement with a strength grade of P.O 42.5, and the water-cement ratio of the high-pressure jet grouting slurry is 1:1; the mixing time of the ordinary mixer is not less than 90s, and the mixing time of the high-speed mixer is not less than 30s. The slurry is used after being sieved and used up within 4 hours from the start of preparation.

7. The construction method of high-pressure jet grouting piles for the cut-off curtain of the overflow dam in high-pebble geology according to claim 1, characterized in that: In S5, for the high-pressure jet grouting by the triple-tube method, first send high-pressure water, then send cement slurry and compressed air; during jetting, after reaching the predetermined jetting pressure and slurry injection volume, gradually lift the grouting pipe. The overlapping length of the segmented lifting of the grouting pipe shall not be less than 100mm.

8. The construction method of high-pressure jet grouting piles for the water-stop curtain of an overflow dam in high-pebble geology according to claim 7, characterized in that: In S5, for the high-pressure jet grouting by the triple-tube method, the high-pressure jet grouting slurry works continuously in the borehole. When the jetting pipe reaches the designed depth, start jetting the cement slurry and compressed air, and then stand still in place for 1 to 3 minutes. When the jetting pressure and slurry injection quantity reach the specified values and the slurry flows out of the hole, carry out the jetting operation from bottom to top. When the designed height is reached, stop jetting and lift out the water jetting pipe, stop lifting at the formation boundary, statically jet for 5 - 10 minutes and increase the slurry supply volume. When the water-cement ratios of the slurry are 1:1 and 0.6:1, the corresponding slurry densities are 1.5g / cm³ and 1.6g / cm³ respectively.

9. The construction method of high-pressure jet grouting piles for the water stop curtain of the overflow dam in high cobble geology according to claim 1, characterized in that: In S5, carry out static pressure filling grouting in the sunken jetting holes until the slurry surface is stable.

10. The construction method of high-pressure jet grouting piles for the cut-off curtain of an overflow dam in high cobble geology according to claim 1, characterized in that: In S6, the construction of adjacent two high-pressure jet grouting piles should be carried out at least 48 hours apart.