High-pressure jet grouting pile construction method suitable for deep overburden rock mass

Abstract

The application discloses a high-pressure rotary jet grouting pile construction method suitable for deep overburden rock mass in the technical field of geotechnical engineering slope reinforcement, and mainly comprises the following steps: after drilling a hole to the design depth in a deep overburden slope, a sound wave detection system is used to detect the sound wave of the rock-soil mass in the hole, a large boulder area is identified and marked, and the rock-soil mass in different areas is classified according to the corresponding relationship between the sound wave detection value and the rock-soil quality; the jetting pressure of the high-pressure pre-mixed abrasive water jet is determined according to the classification result, the large boulder area is cut and broken, and the sound wave re-detection is used for verification; after the accumulated water in the hole is pumped out, the jet grouting is rotated and lifted from the bottom of the hole upwards, and the jet grouting pressure and the slurry concentration are dynamically adjusted according to the classification result of each area, so that the high-pressure rotary jet grouting pile with equal pile diameter and equal strength is formed. Through the closed-loop control of detection classification, targeted rock breaking, re-detection verification and dynamic parameter adjustment, the application realizes accurate breaking of the large boulder, and guarantees the pile forming quality and the slope stability.

Description

Technical Field

[0001] This invention relates to the field of slope reinforcement technology in geotechnical engineering, and in particular to a high-pressure jet grouting pile construction method suitable for deep overburden rock masses. Background Technology

[0002] Construction projects often involve the excavation of underground caverns and slopes, and the stability of the rock mass directly affects the safety of the project. Especially in red-bed areas, the surrounding rock of deep overburden underground caverns and the soil and rock masses of steep, deep overburden slopes have poor self-stability. Traditional anchor bolt and cable supports lack strong anchor points, resulting in poor support effectiveness. High-pressure jet grouting piles, as a mature method for reinforcing weak foundations, are gradually being introduced into the reinforcement of deep overburden soil and rock masses.

[0003] Chinese patent document CN115853004A discloses a high-pressure jet grouting method for constructing an anti-seepage wall. This method involves drilling into a gravel layer, drilling holes in large boulders, injecting static fracturing agents to break them up, and then installing PVC pipes as a protective wall. During jet grouting, the PVC pipes and surrounding gravel are broken up and consolidated together. However, this method treats boulders as a post-drilling process, making it impossible to determine the location, size, and distribution of boulders in the hole before the jet grouting operation. Furthermore, the use of fixed parameters for grouting makes it difficult to form uniform pile bodies when dealing with thick overburden layers containing boulders and unevenly distributed soil, as incompletely broken boulders can easily create cavities in the pile body. The fixed parameters also make it difficult to achieve uniform pile bodies.

[0004] Therefore, how to accurately determine the distribution of boulders and the differences in soil and rock quality within the borehole before jet grouting operations, thoroughly and controllably break up large boulders, and form high-pressure jet grouting piles with uniform diameter and strength in heterogeneous strata is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] To overcome the above-mentioned shortcomings of existing high-pressure jet grouting construction technology, the technical problem to be solved by the present invention is to provide a high-pressure jet grouting pile construction method suitable for thick overburden rock masses, which can accurately determine the distribution of boulders and the differences in rock and soil quality in the borehole before jet grouting operation, thoroughly and controllably break up large boulders, and form high-pressure jet grouting piles of equal diameter and strength in heterogeneous strata.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows: A high-pressure jet grouting pile construction method applicable to deep overburden rock masses includes the following steps: S1. Use a drilling system to drill holes to the designed depth on slopes with thick overburden. S2. Use an acoustic detection system to conduct acoustic detection on the rock and soil in the borehole. Identify and mark the large isolated rock areas in the borehole based on the acoustic detection values. According to the preset correspondence between acoustic detection values ​​and rock and soil quality, classify the rock and soil in different areas of the borehole according to their quality. S3. Determine the injection pressure of the high-pressure premixed abrasive water jet based on the quality grading results, and use the high-pressure premixed abrasive water jet to perform rotary cutting and crushing on the marked large boulder area. S4. After the crushing is completed, use the acoustic detection system again to conduct acoustic detection inside the borehole to determine whether the crushing result meets the requirements. If it does not meet the requirements, repeat step S3. S5. Pump out the water accumulated in the borehole; S6. Utilize a high-pressure rotary jet grouting system to rotate and lift the grouting from the bottom of the borehole upwards. During the grouting process, dynamically adjust the grouting pressure and grout concentration according to the quality classification results of the soil and rock mass in each area to form high-pressure rotary jet grouting piles with equal pile diameter and equal strength.

[0007] Furthermore, before step S2, the process includes: conducting on-site rock mass matching tests and establishing a database of acoustic value ranges corresponding to different rock types and rock blocks of different sizes; in step S2, the acoustic monitoring values ​​inside the borehole are compared with the database to determine the rock type and block size at different locations inside the borehole.

[0008] Furthermore, in step S2, the acoustic detection proceeds from the bottom of the borehole to the top, detecting the rock and soil within a range of no less than 3m around the borehole.

[0009] Furthermore, the quality grading described in step S2 and the dynamic adjustment described in step S6 are performed according to the following correspondence: when the acoustic wave velocity is greater than 3500 m / s, it is grade I, corresponding to a shotcrete pressure of 40-50 MPa and a slurry water-cement ratio of no more than 1:1; when the acoustic wave velocity is 2500-3500 m / s, it is grade II, corresponding to a shotcrete pressure of 30-40 MPa and a slurry water-cement ratio of no more than 1.2:1; when the acoustic wave velocity is less than 2500 m / s, it is grade III, corresponding to a shotcrete pressure of 20-30 MPa and a slurry water-cement ratio of no more than 1.3:1.

[0010] Furthermore, in step S3, the high-pressure water pump pumps a portion of the water into the high-pressure water pipeline and another portion into the abrasive tank. The abrasive in the abrasive tank is mixed with water and then enters the high-pressure water pipeline. It is then accelerated and ejected through a water jet nozzle placed in the borehole to break the rock. The abrasive is corundum or quartz sand.

[0011] Furthermore, the water jet nozzle rotates along the borehole axis to achieve rotary rock breaking. After rock breaking is completed at a certain elevation, it is raised to the next elevation where rock breaking is required, and this cycle is repeated. The abrasive water jet is shut off in elevation sections where rock breaking is not required.

[0012] Furthermore, in step S5, before pumping out the accumulated water, a PVC protective sleeve is lowered into the borehole. The diameter of the PVC protective sleeve is 3-5 cm smaller than the borehole diameter. In step S6, the PVC protective sleeve is not removed during grouting. The high-pressure grout pressure is used to break it together with the surrounding rock and soil to form a pile.

[0013] Furthermore, before step S6, the process includes: determining the cutting and breaking capacity of the soil layer and the pile-forming capacity under different grout concentrations and different jet grouting pressures through process tests, which serves as the adjustment benchmark for the dynamic adjustment.

[0014] The beneficial effects of this invention are: 1. The use of an acoustic detection system to proactively determine the distribution of rock strata within the borehole before breaking operations, pre-identify and mark areas with large boulders, transforming the passive encounter-based processing of existing technologies into proactive prediction, and classifying the quality of the rock and soil within the borehole according to the acoustic detection values, providing a reliable basis for setting rock breaking parameters and jet grouting parameters; 2. High-pressure premixed abrasive water jet is used to rotate and cut and crush the marked large boulders. The abrasive particles significantly enhance the cutting ability of the jet, which can thoroughly crush hard large boulders. The injection pressure is determined according to the quality grading results, which realizes targeted rock breaking. After crushing, the results are verified by sonic testing. If the results are not up to standard, the crushing is repeated. This forms a closed-loop control of detection, crushing and verification, which ensures that the boulders are crushed to the standard before entering the pile construction process, thus fundamentally avoiding the presence of cavities in the pile body. 3. During the shotcreting process, the shotcreting pressure and grout concentration are dynamically adjusted according to the quality classification results of the soil and rock masses in each area, so that the grouting bodies with the same pile diameter and strength are formed in strata with different hardness, which ensures the pile quality in the heterogeneous thick overburden and ensures the stability of the excavated slope in the thick overburden. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the construction system used in this invention; The markings in the diagram are as follows: 11-Drilling rig and drill rod, 21-Sonic probe, 31-Rock breaking water tank, 32-High-pressure water pump, 33-High-pressure water pipeline, 34-Abrasive tank, 35-Water jet nozzle, 36-Pump pressure control system, 37-Valve, 41-Swirl jet water tank, 42-Pumping mixer, 43-Cement silo, 44-High-pressure grouting pipe, 45-Mud nozzle, 51-Drainage pipeline, 52-Drainage suction head, 53-Drainage pump, 61-Thick overburden slope, 62-Large boulder, 71-PVC retaining wall sleeve. Detailed Implementation

[0016] The invention will be further described below with reference to the accompanying drawings.

[0017] It should be noted that if this invention uses directional terms such as up, down, left, right, front, and back, these are for describing the relative positions of components and are not specific references to the absolute positions of related components or the relationships between them. They are only used to explain the relative positional relationships and movements of components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. If this invention uses terms related to quantity such as "many," "multiple," or "several," these specifically refer to two or more.

[0018] like Figure 1 As shown, the construction system upon which the construction method of this invention relies includes a drilling system, an acoustic detection system, a high-pressure pre-mixed abrasive water jet rock-breaking system, a pump pressure control system, a high-pressure rotary jetting system, and a pumping and drainage system. The drilling system includes a drilling rig and drill rod 11, used to drill boreholes on a slope 61 with a thick overburden layer; the acoustic probe 21 of the acoustic detection system is lowered into the borehole to perform acoustic detection on the rock and soil inside and around the borehole; the high-pressure pre-mixed abrasive water jet rock-breaking system includes a rock-breaking water tank 31, a high-pressure water pump 32, a high-pressure water pipeline 33, an abrasive tank 34, and a water jet nozzle 35; the pump pressure control system 36 controls the flow of water from the high-pressure water pump 32 to the high-pressure water pipeline 33 and the abrasive tank 34 by controlling the opening of the control valve 37. The pumping pressure forms an abrasive water jet that is ejected from the water jet nozzle 35; the high-pressure rotary shotcrete system includes a rotary jet water tank 41, a pumping mixer 42, a cement silo 43, a high-pressure grouting pipe 44, and a mud nozzle 45. The pumping mixer 42 extracts water from the rotary jet water tank 41 and cement ash from the cement silo 43 according to the ratio, mixes them to form mortar, and then ejects it from the mud nozzle 45 through the high-pressure grouting pipe 44; the drainage system includes a drainage suction head 52 and a drainage pump 53 respectively installed at both ends of the drainage pipe 51.

[0019] The high-pressure jet grouting pile construction method applicable to deep overburden rock masses in this embodiment includes the following steps: S1. Drilling: Using a drilling rig and drill rod 11, drill a borehole to the designed depth on the slope 61 with a thick overburden layer. The borehole diameter and depth shall be determined according to the design requirements. After drilling, ensure that there are no residual rock and soil debris in the borehole, and that the borehole wall is as smooth and uniform as possible to ensure the accuracy of subsequent acoustic testing data and the smooth progress of rock breaking and shotcreting operations.

[0020] S2. Acoustic Wave Detection and Quality Grading: Before formal detection, an on-site rock mass matching test is conducted. Acoustic wave tests are performed on rocks of different types and sizes at the engineering site to establish a database of acoustic wave value ranges corresponding to different rock types and sizes. Then, the acoustic wave probe 21 of the acoustic wave detection system is lowered to the bottom of the borehole and raised segment by segment from the bottom to the top of the borehole to detect the rock and soil within a range of no less than 3m around the borehole. Acoustic wave detection values ​​at each elevation are obtained and compared with the database to determine the rock type and size at different locations within the borehole. Based on this, the elevation area where the large boulders 62 are located is identified and marked. At the same time, according to the preset correspondence between acoustic wave detection values ​​and rock and soil quality, the rock and soil in different areas of the borehole are graded for quality. The preferred basis for a detection range of no less than 3m is that the design pile diameter and grout diffusion influence range of high-pressure jet grouting piles are generally within 3m. A detection range of less than 3m may miss the pile body and boulders within its influence range, resulting in incomplete fragmentation; a detection range that is too large will unnecessarily increase the workload and construction costs.

[0021] In this embodiment, the quality classification and dynamic adjustment of the shotcrete parameters are carried out according to the following correspondence: when the acoustic wave velocity is greater than 3500m / s, it is Class I, corresponding to a shotcrete pressure of 40-50MPa and a slurry water-cement ratio of no more than 1:1; when the acoustic wave velocity is 2500-3500m / s, it is Class II, corresponding to a shotcrete pressure of 30-40MPa and a slurry water-cement ratio of no more than 1.2:1; when the acoustic wave velocity is less than 2500m / s, it is Class III, corresponding to a shotcrete pressure of 20-30MPa and a slurry water-cement ratio of no more than 1.3:1. The optimal basis for this correspondence is as follows: the acoustic wave velocity reflects the integrity and hardness of the soil and rock mass; the higher the wave velocity, the harder the soil and rock mass. In the Class I region, large boulders are very hard, requiring higher grouting pressure to ensure cutting and breaking ability, and a lower water-cement ratio to ensure grout concentration and pile strength. In the Class III region, the soil and rock mass is loose and weak, and lower grouting pressure can achieve cutting and replacement. Appropriately relaxing the water-cement ratio can improve grout pumpability and avoid grout waste. Excessive grouting pressure will increase energy consumption and may disturb the slope, while too low a pressure will not be able to effectively cut hard boulders. The three levels of parameters are set in a gradient of decreasing pressure and increasing water-cement ratio, matching the progressively decreasing hardness of the soil and rock mass. It should be noted that the above parameters are only for preliminary reference for different specific projects and should be adjusted according to the grout return situation of the test pile, pumping stability, core sampling quality, etc.

[0022] S3. Abrasive Waterjet Rotary Cutting and Crushing: The injection pressure of the high-pressure pre-mixed abrasive waterjet is determined based on the quality grading results. After the rock-breaking system is activated, the pressure leading to the high-pressure water pipe 33 and the abrasive tank 34 is pre-adjusted by controlling the opening of the valve 37 through the pump pressure control system 36. The high-pressure water pump 32 pumps part of the water from the rock-breaking water tank 31 into the high-pressure water pipe 33, and the other part into the abrasive tank 34. The abrasive and water in the abrasive tank 34 are mixed and then enter the high-pressure water pipe 33, where they meet the high-pressure water. The mixture is then accelerated and ejected through the water jet nozzle 35 placed in the borehole, performing rotary cutting and crushing on the area where the marked large boulder 62 is located. In the pre-mixed abrasive waterjet, high-hardness abrasive particles continuously impact the rock surface with the high-speed water flow, and its cutting ability is significantly stronger than that of pure water jet, effectively crushing hard large boulders. The preferred abrasive is either corundum or quartz sand, both of which are high-hardness solid particles with strong cutting ability. Corundum has higher hardness and better crushing efficiency, while quartz sand is widely available and has a lower cost. The choice can be made based on the hardness of the boulder and the project cost.

[0023] During the crushing operation, the water jet nozzle 35 rotates 360° along the borehole axis to achieve rotary rock breaking; after rock breaking at a certain elevation is completed, it is raised to the next elevation where rock breaking is required, and so on. The rotation speed and lifting speed are dynamically adjusted according to the actual rock breaking effect; the abrasive water jet is turned off in the elevation section where rock breaking is not required to avoid disturbance to the section where rock breaking is not required and energy waste.

[0024] S4. Retesting the Crushing Effect: After crushing, the acoustic probe 21 is lowered into the borehole again for acoustic detection. The retested acoustic value is compared with the acoustic value range corresponding to the quality grade to determine whether the crushing result meets the requirements. If it meets the requirements, proceed to the next step; if not, repeat step S3 until the requirements are met. This forms a closed-loop control of detection, crushing, and verification, ensuring that large boulders are effectively crushed before shotcreting and pile foundation construction.

[0025] S5. Lowering the PVC wall casing and draining accumulated water: First, lower the PVC wall casing 71 into the borehole to the bottom to prevent borehole collapse after rock breaking and ensure smooth progress of subsequent procedures. The diameter of the PVC wall casing 71 is 3-5 cm smaller than the borehole diameter, and its height is flush with the borehole. The optimal size difference is as follows: if it is less than 3 cm, the annular gap is too small, and the casing is prone to scraping and getting stuck with the borehole wall during lowering, making it difficult to lower into place; if it is greater than 5 cm, the gap is too large, resulting in poor wall fit and requiring more grout to fill during jet grouting, causing waste. Then, lower the drainage pipe 51 along the PVC wall casing 71 to the bottom of the borehole, start the drainage pump 53, and use the drainage suction head 52 to promptly drain the accumulated water in the borehole during the abrasive water jet rock breaking process to prevent the accumulated water from diluting the jet grout concentration and affecting the pile strength; after drainage is completed, pull out the drainage pipe 51 and the drainage suction head 52.

[0026] S6. Rotary Lifting Shotcrete Pile Formation: Before shotcreting, process tests are conducted to determine the cutting and breaking capacity of the soil layer and the pile formation capacity under different slurry concentrations and different jet grouting pressures. This serves as an adjustment benchmark for dynamic adjustment. For specific projects, parameters can be specifically modified based on the slurry return situation of the test piles, pumping stability, and core sampling quality. During shotcreting, the mud nozzle 45 is lowered to the bottom of the hole along the PVC wall sleeve 71. The water in the jet grouting water tank 41 and the cement ash in the cement silo 43 are mixed evenly in the pump mixer 42 and then transported to the mud nozzle 45 through the high-pressure grouting pipe 44. The mud nozzle 45 is then rotated and lifted upwards from the bottom of the borehole for shotcreting.

[0027] During the shotcreting process, the PVC protective sleeve 71 is not removed. The high-pressure grout pressure is used to break it up together with the surrounding soil and rock to form the pile body, eliminating the need for pipe removal and improving construction efficiency. At the same time, the shotcreting pressure and grout concentration are dynamically adjusted according to the quality classification results of the soil and rock in each area. Specifically, when the shotcreting is upgraded to the Class I area, a shotcreting pressure of 40-50 MPa and a grout water-cement ratio of no more than 1:1 are used; when upgraded to the Class II area, a shotcreting pressure of 30-40 MPa and a grout water-cement ratio of no more than 1.2:1 are used; and when upgraded to the Class III area, a shotcreting pressure of 20-30 MPa and a grout water-cement ratio of no more than 1.3:1 are used. This ensures that after cutting and replacing strata of different hardness, jet grouting bodies of equal diameter and strength are formed, ultimately creating uniform and dense high-pressure jet grouting piles.

Claims

1. A high-pressure jet grouting pile construction method applicable to deep overburden rock masses, characterized in that, Includes the following steps: S1. Use a drilling system to drill holes to the designed depth on slopes with thick overburden. S2. Use an acoustic detection system to conduct acoustic detection on the rock and soil in the borehole. Identify and mark the large isolated rock areas in the borehole based on the acoustic detection values. According to the preset correspondence between acoustic detection values ​​and rock and soil quality, classify the rock and soil in different areas of the borehole according to their quality. S3. Determine the injection pressure of the high-pressure premixed abrasive water jet based on the quality grading results, and use the high-pressure premixed abrasive water jet to perform rotary cutting and crushing on the marked large boulder area. S4. After the crushing is completed, use the acoustic detection system again to conduct acoustic detection inside the borehole to determine whether the crushing result meets the requirements. If it does not meet the requirements, repeat step S3. S5. Pump out the water accumulated in the borehole; S6. Utilize a high-pressure rotary jet grouting system to rotate and lift the grouting from the bottom of the borehole upwards. During the grouting process, dynamically adjust the grouting pressure and grout concentration according to the quality classification results of the soil and rock mass in each area to form high-pressure rotary jet grouting piles with equal pile diameter and equal strength.

2. The high-pressure jet grouting pile construction method applicable to deep overburden rock masses as described in claim 1, characterized in that, Before step S2, the process also includes: conducting on-site rock mass matching tests and establishing a database of acoustic value ranges corresponding to different rock types and rock blocks of different sizes; in step S2, the acoustic monitoring values ​​in the borehole are compared with the database to determine the rock type and block size at different locations in the borehole.

3. The high-pressure jet grouting pile construction method applicable to deep overburden rock masses as described in claim 1, characterized in that, In step S2, the acoustic detection proceeds from the bottom of the borehole to the top, detecting the rock and soil within a range of no less than 3m around the borehole.

4. The high-pressure jet grouting pile construction method applicable to deep overburden rock masses as described in claim 1, characterized in that, The quality grading described in step S2 and the dynamic adjustment described in step S6 are performed according to the following correspondence: when the sound wave velocity is greater than 3500 m / s, it is grade I, corresponding to a shotcrete pressure of 40-50 MPa and a slurry water-cement ratio of no more than 1:1; when the sound wave velocity is 2500-3500 m / s, it is grade II, corresponding to a shotcrete pressure of 30-40 MPa and a slurry water-cement ratio of no more than 1.2:1; when the sound wave velocity is less than 2500 m / s, it is grade III, corresponding to a shotcrete pressure of 20-30 MPa and a slurry water-cement ratio of no more than 1.3:

1.

5. The high-pressure jet grouting pile construction method applicable to deep overburden rock masses as described in claim 1, characterized in that, In step S3, a high-pressure water pump pumps a portion of the water into a high-pressure water pipeline and another portion into an abrasive tank. The abrasive in the abrasive tank mixes with the water and then enters the high-pressure water pipeline. The mixture is then accelerated and ejected through a water jet nozzle placed in the borehole to break the rock. The abrasive is corundum or quartz sand.

6. The high-pressure jet grouting pile construction method applicable to deep overburden rock masses as described in claim 5, characterized in that, The water jet nozzle rotates along the borehole axis to achieve rotary rock breaking. After rock breaking is completed at a certain elevation, it is raised to the next elevation where rock breaking is required, and so on. The abrasive water jet is turned off in elevation sections where rock breaking is not required.

7. The high-pressure jet grouting pile construction method applicable to deep overburden rock masses as described in claim 1, characterized in that, In step S5, before pumping out the accumulated water, a PVC protective sleeve is lowered into the borehole. The diameter of the PVC protective sleeve is 3-5 cm smaller than the borehole diameter. In step S6, the PVC protective sleeve is not removed during grouting. The high-pressure grout pressure is used to break it up together with the surrounding rock and soil to form a pile.

8. The high-pressure jet grouting pile construction method applicable to deep overburden rock masses as described in claim 1, characterized in that, Before step S6, the process also includes: determining the cutting and breaking capacity of the soil layer and the pile formation capacity under different grout concentrations and different jet grouting pressures through process tests, which serves as the adjustment benchmark for the dynamic adjustment.

Images