Foundation anti-seepage treatment construction method based on presplitting pull groove

Abstract

The invention discloses a foundation anti-seepage treatment construction method based on pre-splitting joint forming, which comprises the following steps of: drilling a pre-splitting hole in the axial direction of a foundation dam in advance, carrying out joint pulling treatment on a foundation by adopting pre-splitting blasting, pre-splitting and penetrating the foundation needing curtain grouting and anti-seepage wall construction in advance, and releasing a stress space. And the pre-split holes are detonated and cleaned, then the pre-split holes are directly grouted by adopting a hole bottom grouting method, after cracks in all directions are communicated, grout can smoothly flow in the cracks, leakage spraying is prevented, and the integrity of a grouting curtain is improved. And meanwhile, the foundation pre-seam-drawing is beneficial to guide wall construction, and the guide groove excavation difficulty is reduced. And finally, the purposes of improving the foundation anti-seepage construction efficiency and construction quality are achieved.

Description

Technical Field

[0001] This invention relates to the field of water conservancy engineering construction, specifically to a foundation seepage prevention treatment construction method based on pre-cracked joints. Background Technology

[0002] Common methods for foundation seepage control mainly include grouting with cut-off curtains and constructing cut-off walls. Curtain grouting can effectively handle complex geological conditions such as faults, fracture zones, and gravel layers, sealing bedrock fissures or seepage channels by forming a continuous water-blocking barrier, thereby improving the stability of dams or embankments. Cut-off walls, on the other hand, utilize concrete or plastic materials to construct continuous walls to completely cut off seepage paths, with a permeability coefficient as low as 1×10⁻⁷ cm / s. In engineering practice, cut-off walls are often combined with curtain grouting to form a composite seepage control system of "upper wall and lower curtain," which takes into account both efficient shallow seepage interception and sealing of deep fissures.

[0003] However, in actual construction, the seepage prevention effect of these traditional methods often falls short of expectations. For example, when performing curtain grouting in gravel layers, problems such as borehole collapse and difficulty in drilling are prone to occur, and the determination of grouting parameters largely depends on experience, which can easily lead to problems such as grout cross-contamination and leakage. For the construction of cutoff walls, in karst development areas or strata containing large-diameter boulders, trenching difficulties or seepage around the cutoff wall are likely to occur, and the final effect is constrained by multiple factors such as geological conditions, material properties, and construction technology. Summary of the Invention

[0004] The purpose of this invention is to provide a foundation seepage prevention construction method based on pre-cracked joints, in order to solve the problems of low construction efficiency and unstable quality of foundation seepage prevention in the prior art.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: to provide a foundation seepage prevention treatment construction method based on pre-splitting trenching, the foundation seepage prevention treatment construction method based on pre-splitting trenching comprising the following steps: S1. Geological exploration and scheme design: By drilling, geophysical exploration and other means, parameters such as stratum fractures and permeability are obtained, the curtain axis or the anti-seepage wall axis is determined, and multiple blasting points are determined on the axis as pre-splitting holes, and the hole diameter, hole spacing and single hole depth parameters of the pre-splitting holes are further determined. S2. Determination of Uniaxial Compressive Strength of Rock: Rock samples are taken from multiple locations to be blasted, and the uniaxial compressive strength of the rock is calculated by converting the results of point load strength tests. ; S3. Calculation of pre-splitting hole spacing: Calculate the pre-splitting hole spacing a based on the rock mass properties and hole diameter; S4. Calculation and Correction of Linear Charge Density: Calculation of Linear Charge Density And based on the rock mass integrity coefficient Make corrections; S5, Rock Mass Integrity Coefficient Calculation: Acoustic wave detection was performed at multiple locations to be blasted, and the longitudinal wave velocity of the rock and rock mass was measured using an acoustic wave detector. The rock mass integrity coefficient was calculated. ; S6. Charge and Detonation: PVC pipes are used to achieve decoupled charge, and the charge is segmented in a "bottom-concentrated + top-dispersed" manner, using reverse detonation technology; S7. Blocking and Protection: Use clay and gravel mixture as the blocking material, with a blocking length ≥1.0m and a 0.3m air gap layer at the top to buffer energy; cover the orifice with sandbags and rubber, with each bag weighing ≥20kg to suppress flying rocks; S8. Quality control and acceptance of pre-splitting blasting: Acceptance is based on the standard of fracture network continuity, and the diameter of pre-splitting holes is required to be ≥80mm. S9. High-pressure water pulsation flushing: High-pressure water pulsation flushing penetrates the gap, with a flushing time of ≥30 minutes, followed by 10 minutes of clean water backflushing to ensure that the gap is clean and unblocked, and that the hole wall does not collapse or shrink. S10. Grouting: Using the pre-cracked holes, ultrafine cement grout is injected in sections from bottom to top using the bottom-hole grouting method. S11. Grouting quality control: The permeability is verified by water pressure test, and the seepage prevention effect is verified by core drilling.

[0006] In one embodiment, in step S1, the borehole layout should cover possible abnormal geological areas as much as possible, and geophysical exploration should be used to accurately obtain parameters such as formation fracture rate, permeability coefficient, and rock mass integrity to avoid errors from a single method.

[0007] In one embodiment, in S1, the axis of the curtain or anti-seepage wall avoids unfavorable geological areas such as large fault zones and weak interlayers, and the axis direction can be adjusted or reinforcement measures can be added.

[0008] In one embodiment, in S1, the pre-splitting hole diameter is ≥80mm, and the deep hole uses a large diameter to improve efficiency; the hole spacing a ranges from 0.2 to 0.8m; and the rationality of the parameters is verified by blasting tests, and the drilling spacing is adjusted according to the feedback to ensure crack penetration.

[0009] In one embodiment, the point load strength test procedure in S2 is as follows: the specimen is placed between the two conical indenters of the point load tester, ensuring that the distance D between the loading points is equal to the width of the specimen's failure surface. satisfy ≥0.3; Control the loading speed to prevent failure within 10~60 seconds, and record the failure load P; When the specimens are regular specimens, the number of specimens in each group shall not be less than 10; when the specimens are irregular specimens, the number of specimens in each group shall be 15 to 20. After removing outliers, the average value is taken; when the equivalent core diameter Or the spacing between loading points When the result is not equal to 50mm, the calculation result is... Make corrections.

[0010] In one embodiment, in step S6, the PVC pipe body is reinforced by drilling holes in the sidewall of the PVC pipe to enhance the guiding effect of the explosive gas on the crack, while maintaining the uniformity of axial charge. The inner diameter of the PVC pipe should be 1 / 3 to 1 / 2 of the diameter of the pre-cracked hole. By adjusting the pipe diameter, energy buffering is achieved, and the pressure on the hole wall is reduced to 1 / 16 to 1 / 5 of the rock compressive strength to avoid crushing the hole wall.

[0011] In one embodiment, during the segmented loading of the explosive, the amount of explosive in the bottom concentrated section is increased to overcome the clamping effect at the bottom of the hole. The length of the bottom concentrated section is controlled at 1.3 times the resistance line. Small explosive cartridges are tied at 0.5m intervals in the upper dispersed section. The cartridges are tied with positioning clamps to ensure that the spacing error is ≤2cm and the cartridge diameter is ≤50% of the pipe diameter. Energy gradient release is achieved through axial uniform distribution.

[0012] In one embodiment, in step S6, the lead wire is double-insulated with heat shrink tubing and waterproof tape, and the tubing opening is sealed with epoxy resin to prevent water seepage.

[0013] In one embodiment, in step S8, the pre-cracks need to be continuous along the design axis, and the pre-crack width requirements are: hard rock ≥ 0.5cm, medium-hard rock ≥ 1.0cm, soft rock ≥ 1.5cm.

[0014] In one embodiment, in S9, pulsed pressure fluctuations are used to enhance the stripping effect on the deposits within the fissures; During the main flushing phase, the pressure is increased gradually from 0.5MPa to 1MPa in a stepwise manner for 30 minutes to avoid the collapse of the borehole wall caused by instantaneous high pressure impact. During the clean water backflushing stage, maintain a pressure of 0.3~0.5MPa for 10 minutes to carry away residual debris with low-flow-rate clean water; keep the nozzle at a 17° incident angle with the borehole wall to use shear force to strip away contaminants rather than directly impacting the rock mass; The spray distance should be controlled at 150 to 300 times the nozzle diameter.

[0015] In one embodiment, in step S10, ultrafine cement with a particle size ≤15μm is selected, and the water-cement ratio is controlled at 0.3~0.5; and 2%~5% of accelerator and 5%~10% of expansion agent are added.

[0016] In one embodiment, in step S10, a steel pipe or flexible grouting valve is used. A perforated section is set at the bottom of the grouting pipe, with grout outlets of 3-5 mm in diameter and spaced 10 cm apart to ensure uniform grout diffusion. The grouting pipe is lowered to 20 cm from the bottom of the hole to prevent sediment from clogging the outlet, and is temporarily sealed with tape. The outlet is opened by high pressure during grouting. Grouting is carried out in sections from bottom to top, with each section being 5-6 m long. In special strata, the length can be shortened to 3 m or extended to 10 m. After each section is grouted, the grouting pipe is raised to the previous section and the process is repeated. Pressure control: the initial pressure is 0.3 MPa, gradually increasing to 0.5 MPa to avoid lifting and damage. If the grout absorption rate drops suddenly, intermittent grouting or adjustment of the grout concentration is used.

[0017] In one embodiment, in S11, 7 days after the completion of each grouting unit, 30% of the units are randomly selected for water pressure testing and core sampling. The water pressure test is conducted by injecting water into the borehole in sections under pressure to determine the permeability of the rock mass. The test involves drilling with diamond drill bits and clean water, washing the borehole until the return water is clear, using air pressure or water pressure plugs for section isolation, continuously observing the flow rate 5 times under stable pressure, and taking the average value when the fluctuation range is ≤10% to calculate the permeability.

[0018] In one embodiment, in S11, the core sampling inspection holes are located on the curtain axis and number 3% to 10% of the total number of pre-splitting holes, mainly arranged in areas with faults, fissures, or large grout absorption; observe the morphology of the grout stone body, the density of fissure filling, and test the compressive strength of the stone body; the qualified standard is that the grout vein filling rate is ≥90%, and the stone body is continuous without voids and tightly cemented with the surrounding rock.

[0019] The above-described technical solutions in the embodiments of the present invention have at least the following technical effects or advantages: The foundation seepage prevention treatment method based on pre-splitting trenching provided in this invention involves pre-drilling pre-splitting holes along the dam axis, and then using pre-splitting blasting to create joints in the foundation. This pre-splitting process allows for the opening of stress-relieving spaces in the foundation where curtain grouting and cutoff wall construction are required. The pre-splitting holes are then blasted and cleaned, followed by direct grouting using bottom-hole grouting. The interconnected fractures facilitate smooth grout flow within each fracture, preventing leakage and improving the integrity of the grouting curtain. Simultaneously, pre-jointing the foundation facilitates guide wall construction and reduces the difficulty of guide trench excavation. Ultimately, this method aims to improve the efficiency and quality of foundation seepage prevention construction.

[0020] Furthermore, pre-splitting grooves connect various fractures with different orientations within the rock mass of the foundation, facilitating the smooth flow of grout in subsequent anti-seepage wall or curtain grouting and preventing leakage caused by the presence of some longitudinally non-penetrating fractures. Previously, especially with curtain grouting, grouting only closed fractures; if the fractures reached by the grouting holes were not connected, grout could not be injected. However, pre-splitting grooves connect the fractures before grouting, improving the overall integrity of the grouting curtain and enabling it to not only close fractures but also form a near-plate-like curtain anti-seepage structure. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 A flowchart of a foundation seepage prevention treatment construction method based on pre-splitting trenching provided in an embodiment of the present invention. Detailed Implementation

[0023] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of this invention, it should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0026] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0027] Please see Figure 1 This application provides a foundation seepage prevention construction method based on pre-splitting trenching, specifically including the following steps: Step S1: Geological Survey and Scheme Design 1. Geological Exploration: First, through various methods such as drilling and geophysical exploration (e.g., high-density electrical resistivity tomography), a comprehensive understanding of key parameters of the foundation, such as rock strata fissures, permeability, and rock mass integrity, is obtained. The layout of boreholes should cover potentially anomalous geological areas as much as possible. For example, in karst development areas or fault zones, more frequent drilling is required to ensure data accuracy and avoid errors that may arise from relying on a single exploration method.

[0028] 2. Axis Determination: Based on the survey results, determine the axis of the curtain wall or anti-seepage wall. When planning the axis, try to avoid large fault zones, weak interlayers, and other unfavorable geological bodies. If it is impossible to avoid them, the axis direction needs to be adjusted or additional reinforcement measures need to be designed.

[0029] 3. Parameter Design: On a defined axis, multiple blasting points are arranged; these points are the pre-splitting holes. Then, the parameters such as the hole diameter, hole spacing, and single hole depth of the pre-splitting holes are designed.

[0030] Hole diameter: The diameter of the pre-splitting hole must be no less than 80mm to meet the requirements for subsequent grouting pipe placement. For deeper holes, a larger hole diameter is recommended to improve construction efficiency.

[0031] Hole spacing: The range of hole spacing a is usually between 0.2 and 0.8 meters.

[0032] Parameter verification: The designed parameters need to be verified through on-site blasting tests, and the parameters such as the borehole spacing should be adjusted according to the test feedback results to ensure that a through crack can be formed in the end.

[0033] Step S2: Determination of uniaxial compressive strength of rock 1. Rock sampling: Rock samples were taken at multiple locations to be blasted.

[0034] 2. Point Load Test: On-site point load strength tests were conducted on the collected rock samples. The test procedure is as follows: The specimen was placed between the two conical indenters of the point load apparatus, with the distance between the loading points (D) and the width of the specimen's failure surface (…). ) must meet A relationship ≥0.3. Control the loading rate so that the specimen fails within 10 to 60 seconds, and record the failure load (P) at this time. The number of specimens in each test group should be no less than 10 (regular specimens) or 15 to 20 (irregular specimens), and the average value should be taken after removing outliers.

[0035] 3. Strength Conversion: The uniaxial compressive strength of the rock is calculated using the results of point load strength tests. .

[0036] Calculate the point load strength index The formula is:

[0037] To break the load, The equivalent core diameter (calculated based on the sample failure area). Equivalent core diameter The calculation formula is:

[0038] in, The average width (mm) of the failure surface at the minimum cross-section between the two loading points. The distance between the loading points of the specimen is (mm). Take 3.1416. When or When the value is not equal to 50mm, the calculated value needs to be adjusted. The results were corrected.

[0039] Ultimately, the uniaxial compressive strength of the rock The calculation formula is:

[0040] in, The unit is MPa. This is an empirical coefficient, and its value varies depending on the lithology.

[0041] Step S3: Calculation of pre-cracked hole spacing The spacing 'a' of the pre-cracked holes is calculated using the following empirical formula:

[0042] in, This refers to the diameter of the pre-cracked hole.

[0043] (1) For intact hard rock (such as granite), take 8 to 12 times the pore size.

[0044] (2) For rocks or soft rocks with well-developed fissures, take 5 to 8 times the pore size.

[0045] (3) is a correction factor, which is determined according to the integrity of the rock mass: 0.8 to 1.0 for intact rock mass; 0.7 to 0.9 for layered rock mass; and 0.5 to 0.7 for fractured zone.

[0046] Step S4: Calculation and correction of linear charge density 1. Basic Calculation: Density of Linear Charge The formula for calculating (kg / m³) is as follows:

[0047] in, denoted as uniaxial compressive strength of rock (MPa), and 'a' is the spacing between pre-splitting holes (m).

[0048] 2. Applicable Conditions and Corrections: This formula is applicable to traditional pre-splitting blasting scenarios with free faces (such as slope and tunnel excavation), and where the rock mass compressive strength is between 30 and 150 MPa. However, this invention is applied to cutoff curtains or cutoff walls, which are cases without free faces. Therefore, a rock mass integrity coefficient must be introduced. The density of the linear charge is corrected.

[0049] 3. Revised formula:

[0050] Step S5: Rock mass integrity coefficient calculate 1. Acoustic wave detection: Detection holes are set at multiple locations to be blasted, and acoustic wave detection is performed using an acoustic wave detector equipped with a "one-shot-two-receive" transducer.

[0051] 2. Wave velocity measurement: Longitudinal wave velocity Detection holes were set at the pre-splitting blasting test sites. An acoustic wave detector equipped with one transmitting transducer and two receiving transducers was used to measure the distance between the two receiving transducers and the time difference of sound wave propagation at the detection holes. The longitudinal wave velocity of the rock mass in the fractured area was denoted as... The longitudinal wave velocity of a single rock in a fractured region is denoted as . The calculation formula is as follows: Longitudinal wave velocity of rock mass:

[0052] Rock longitudinal wave velocity:

[0053] in, Given the known installation spacing between the two receiving transducers, For and These represent the time difference of sound wave propagation measured in the rock mass and rock environment, respectively.

[0054] Calculate: Rock mass integrity coefficient The calculation formula is:

[0055] Step S6: Loading and Detonation 1. Decoupled Charge: Based on the calculated linear charge density, select a PVC pipe with an inner diameter of 1 / 3 to 1 / 2 of the pre-fractured hole diameter. This setup (decoupling coefficient ≥ 2) achieves energy buffering by adjusting the pipe diameter, reducing the borehole wall pressure to 1 / 16 to 1 / 5 of the rock compressive strength, thereby preventing borehole wall crushing. To enhance the guiding effect of the explosive gas on the fracture while maintaining the uniformity of the axial charge, the sidewalls of the PVC pipe can be reinforced by drilling (Φ5~8mm).

[0056] 2. Segmented loading: The explosive is loaded in segments using a method of "concentrated at the bottom and dispersed at the top".

[0057] Bottom Concentration Section: To overcome the clamping effect at the bottom of the hole, the amount of explosive at the bottom needs to be increased by 20% to 30%. The length of the concentration section is controlled at 1.3 times the resistance line.

[0058] Upper section: A small cartridge is tied at every 0.5 meters. The cartridges are fixed with positioning clamps to ensure that the spacing error is no more than 2cm and the diameter of the cartridge does not exceed 50% of the inner diameter of the PVC pipe, so as to achieve a uniform axial gradient release of energy.

[0059] 3. Initiation Network: An electronic detonator is fixed in the middle of a PVC pipe. Reverse initiation technology is used at the bottom of the hole. The detonator lead wire must be double-insulated with heat shrink tubing and waterproof tape before exiting the pipe opening, which is then sealed with epoxy resin to prevent water leakage.

[0060] Step S7: Blocking and Protection Plugging: Use a mixture of clay and gravel with a particle size of less than 10mm as the clogging material, with a clogging length of not less than 1.0 meter. Leave a 0.3-meter air gap layer at the top to buffer the blast energy.

[0061] Protection: Cover the orifice with sandbags and rubber sheets, each weighing no less than 20 kg, to effectively suppress flying stones.

[0062] Step S8: Quality Control and Acceptance of Pre-splitting Blasting The acceptance criteria focus on achieving a continuous fracture network along the design axis. Simultaneously, the width of the pre-cracks must meet the requirements for different lithologies. Hard rock (Class I and II): Width ≥ 0.5 cm.

[0063] Medium-hard rock (Grade III): Width ≥ 1.0 cm.

[0064] Soft rock (Class IV and V): Width ≥ 1.5cm.

[0065] Detection method: Six detection points are selected at equal intervals of 100 meters, and the width and continuity of the cracks are measured using a meter stick.

[0066] Step S9: High-pressure water pulse flushing 1. Pulsating flushing: High-pressure water flushing is performed on the through-cracks using pulsed pressure fluctuations (such as a 0.3Hz pulse frequency) to enhance the removal of deposits within the cracks.

[0067] 2. The specific rinsing process is as follows: Main flushing phase: lasting no less than 30 minutes. The pressure is increased gradually from 0.5MPa to 1.0MPa in a stepwise manner to avoid impact and collapse of the borehole wall caused by instantaneous high pressure.

[0068] Backflush stage: Maintain a pressure of 0.3 to 0.5 MPa and backflush continuously with clean water at a low flow rate for 10 minutes to remove any remaining debris.

[0069] 3. Nozzle Parameters: The flushing nozzle maintains a 17° incident angle with the orifice wall, utilizing shearing force rather than direct impact to remove contaminants. The spray distance should be controlled between 150 and 300 times the nozzle diameter. After flushing, ensure the crevices are clean and unblocked, and that the orifice wall shows no signs of collapse or narrowing.

[0070] Step S10: Grouting Grouting material: Primarily ultrafine cement grout. Ultrafine cement with a particle size ≤15μm (D95≤20μm) is selected, and its permeability coefficient can reach 1×10⁻⁶. -6 The grout has a speed of cm / s and can penetrate micro-cracks as small as 0.05 mm. The water-cement ratio should be controlled between 0.3 and 0.5. To control the diffusion range of the grout, 2% to 5% calcium chloride or water glass can be added as a quick-setting agent to shorten the initial setting time to 30 to 60 minutes. At the same time, 5% to 10% UEA expanding agent should be added to compensate for grout shrinkage.

[0071] The specific grouting process is as follows: The pre-splitting holes are used directly, and bottom grouting is carried out in sections from bottom to top. Steel pipes (such as DN15 welded steel pipes) or flexible grouting valves are used as grouting pipes, with perforated pipe sections at the bottom. The diameter of the grout outlet holes is 3 to 5 mm, and the spacing is 10 cm to ensure uniform diffusion of the grout.

[0072] Lower the grouting pipe to 20cm from the bottom of the hole to avoid clogging by sediment. Grout in sections from bottom to top, with each section typically 5 to 6 meters long (3 to 10 meters for special geological formations). After each section is completed, raise the grouting pipe to the next section and repeat the operation.

[0073] The grouting pressure should be controlled between 0.3 and 0.5 MPa, with an initial pressure of 0.3 MPa, gradually increasing, but not exceeding the fracturing pressure of the formation to prevent uplift and damage.

[0074] When the grout absorption rate of a single hole is less than 5 mL / min, grouting must be continued at this pressure for 30 minutes before it can be stopped. If the grout absorption rate suddenly drops midway, intermittent grouting or adjustment of the grout concentration can be used to handle the situation.

[0075] Step S11: Grouting Quality Control 1. Water Pressure Test: Seven days after the completion of each grouting unit, a water pressure test is conducted on 30% of the samples. The permeability of the rock mass is determined by injecting water into the borehole in stages under pressure. During the test, the flow rate is continuously observed five times under stable pressure. If the fluctuation range is less than or equal to 10%, the average value is used to calculate the permeability. The acceptable standard is: permeability ≤ 1 Lu. The formula for calculating permeability is:

[0076] Where Q is the steady flow rate (L / min), P is the pressure (MPa), and L is the length of the test section (m).

[0077] 2. Core drilling: Core sampling inspection holes are located on the curtain axis, accounting for 3% to 10% of the total number of grouting holes, and are mainly arranged in areas with faults, fissures, or high grout absorption. Observe the morphology of the grout-contaminated stones, the filling density of the fissures, and test the compressive strength of the stones (≥1MPa required).

[0078] The qualification standard is that the grout vein filling rate is not less than 90%, and the stone body is continuous without voids and tightly cemented to the surrounding rock. The filling rate formula is:

[0079] in The volume of the slurry-concreted stone. This represents the residual void volume.

[0080] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A construction method for foundation anti-seepage treatment based on pre-splitting a trench, characterized in that, The method comprises the following steps: S1, geological survey and scheme design: parameters such as stratum fissure and permeability are obtained by means of drilling and geophysical prospecting, and a curtain axis or a cutoff wall axis is determined, a plurality of blasting points to be blasted are determined as pre-splitting holes on the axis, and parameters such as pre-splitting hole diameter, hole spacing and single hole depth are further determined; S2, rock uniaxial compressive strength determination: rock sampling is performed on multiple blasting points, and the rock uniaxial compressive strength is obtained by converting the point load strength test results ; S3, pre-splitting hole spacing calculation: pre-splitting hole spacing a is calculated according to rock mass properties and hole diameter; S4, Linear charge density calculation and correction: Calculate linear charge density and according to rock mass integrity coefficient correction; S5, rock mass integrity coefficient Calculation: Sound wave detection is carried out at multiple blasting points, and the longitudinal wave velocity of rock and rock mass is measured by a sound wave detector , and the rock mass integrity coefficient is calculated ; S6, charging and detonation: uncoupled charging is realized by using a PVC pipe, and segmented charging is performed in a "bottom concentrated + upper scattered" manner, and reverse detonation technology is adopted; S7, plugging and protection: clay + gravel mixture is selected as the plugging material, the plugging length is greater than or equal to 1.0 m, and a 0.3 m air spacing layer is pre-set at the top to buffer energy; sandbags + rubber are covered on the hole mouth, and the weight of a single sandbag is greater than or equal to 20 kg to suppress flying stones; S8, pre-splitting blasting quality control and acceptance: acceptance is performed according to the standard of fissure network penetration, and the pre-splitting hole diameter is required to be greater than or equal to 80 mm; S9, high-pressure water pulsating flushing: high-pressure water pulsating flushing is performed through the joint crack, the flushing time is greater than or equal to 30 minutes, and clean water is back-flushed for 10 minutes, so as to ensure that the joint crack is clean and free of blockage, and the hole wall is free of collapse and shrinkage; S10, grouting: directly using the pre-splitting hole, the hole bottom grouting method is adopted to perform segmented grouting of superfine cement slurry from bottom to top; S11, grouting quality control: water permeability is verified by water pressure test, and impermeability effect is verified by drilling core taking.

2. The foundation anti-seepage treatment construction method based on pre-splitting slotting according to claim 1, characterized in that: In S1, the drilling arrangement should cover possible abnormal geological areas as much as possible, and parameters such as stratum fissure rate, permeability coefficient and rock mass integrity are accurately obtained by cooperating with geophysical prospecting, so as to avoid errors of a single means.

3. The foundation anti-seepage treatment construction method based on pre-splitting slotting according to claim 1, characterized in that: In S1, the curtain or cutoff wall axis avoids unfavorable geological areas such as large fault zones and weak interlayers, and the axis direction can be adjusted or reinforcement measures can be added.

4. The foundation anti-seepage treatment construction method based on pre-splitting slotting according to claim 1, characterized in that: In S1, the pre-splitting hole diameter is greater than or equal to 80 mm, and a large hole diameter is adopted for a deep hole to improve efficiency; the hole spacing a ranges from 0.2 to 0.8 m; and the parameter rationality is verified by blasting test, and the drilling spacing is adjusted according to feedback to ensure crack penetration.

5. The foundation anti-seepage treatment construction method based on pre-splitting slotting according to claim 1, characterized in that: In the S2, the point load strength test procedure is as follows: the test piece is placed between the two conical pressure heads of the point load instrument, the spacing D between the loading points is ensured to be equal to the width of the test piece failure surface satisfies ≥0.3; the loading speed is controlled to be within 10-60 seconds to cause failure, and the failure load P is recorded; When the test piece is a regular test piece, the number of test pieces in each group is not less than 10; when the test piece is an irregular test piece, the number of test pieces in each group is 15-20; The average value is taken after removing outliers; when the equivalent core diameter or the load point spacing is not equal to 50 mm, the results are corrected. are corrected.

6. The foundation anti-seepage treatment construction method based on pre-splitting slotting according to claim 1, characterized in that: In S6, the PVC pipe body is subjected to strengthening treatment, holes are drilled in the side wall of the PVC pipe to enhance the guiding effect of blast gas on the crack, and axial charging uniformity is maintained; the inner diameter of the PVC pipe should be 1 / 3-1 / 2 of the pre-splitting hole diameter, energy buffering is realized by adjusting the pipe diameter, the hole wall pressure is reduced to 1 / 16-1 / 5 of the rock compressive strength, and the hole wall is prevented from being crushed.

7. The pre-splitting slot-based foundation anti-seepage treatment construction method according to claim 1, characterized in that: In S6, the amount of concentrated bottom segment is increased to overcome the hole bottom clamping effect, and the length of the bottom concentrated segment is controlled at 1.3 times the resistance line; the upper scattered segment is bound with small cartridges at intervals of 0.5 m, the cartridge binding uses positioning clamps to ensure that the spacing error is ≤2 cm, and the cartridge diameter is ≤50% of the pipe diameter, and the energy gradient release is achieved by uniform distribution in the axial direction.

8. The pre-splitting slot-based foundation anti-seepage treatment construction method according to claim 1, characterized in that: In S6, the foot line uses double insulation of heat shrink tube + waterproof tape, and the pipe opening is sealed with epoxy resin to prevent water seepage.

9. The pre-splitting slot-based foundation anti-seepage treatment construction method according to claim 1, characterized in that: In S8, the pre-splitting crack needs to be continuously penetrated along the design axis, and the pre-splitting crack width requirement is: hard rock ≥0.5 cm, medium-hard rock ≥1.0 cm, and soft rock ≥1.5 cm.

10. The pre-splitting slot-based foundation anti-seepage treatment construction method according to claim 1, characterized in that: In S9, pulse pressure fluctuation is used to enhance the stripping effect on the accumulated material in the fissure; In the main flushing stage, the pressure is gradually increased from 0.5 MPa to 1 MPa in a "stepwise increase" manner, and the hole wall collapse caused by instantaneous high pressure impact is avoided; In the clear water backflushing stage, the pressure is maintained at 0.3-0.5 MPa for 10 minutes to carry away the residual debris with low flow rate clear water; the nozzle and the hole wall maintain an incident angle of 17°, and the shear force is used to strip the contaminants instead of directly impacting the rock mass; The jetting distance is controlled at 150-300 times the nozzle diameter.

11. The pre-splitting slot-based foundation anti-seepage treatment construction method according to claim 1, characterized in that: In S10, ultra-fine cement with a particle size of ≤15 μm is selected, and the water-cement ratio is controlled at 0.3-0.5; 2%-5% of a quick-setting agent and 5%-10% of an expansive agent are added.

12. The pre-splitting slot-based foundation anti-seepage treatment construction method according to claim 1, characterized in that: In S10, a steel pipe or a flexible grouting valve is used, a flower pipe section is arranged at the bottom of the grouting pipe, the grout outlet diameter is 3-5 mm, the spacing is 10 cm, and the grout is uniformly dispersed; the grouting pipe is lowered to a distance of 20 cm from the hole bottom to avoid blockage of the grout outlet by sediment, and the grout outlet is temporarily sealed by a tape; the grouting pipe is lifted to the next section after each section is grouted to repeat the process; The pressure control: the initial pressure is 0.3 MPa, which is gradually increased to 0.5 MPa to avoid lifting damage; when the slurry absorption rate suddenly drops, intermittent grouting or adjustment of the slurry concentration is used.

13. The pre-splitting slot-based foundation anti-seepage treatment construction method according to claim 1, characterized in that: In the S11, after each grouting unit is completed for 7 days, water pressure test and coring are performed at a proportion of 30%; the water pressure test is performed by segmentally pressurizing and injecting water into the borehole to measure the water permeability of the rock mass; the diamond drill bit is used for drilling with clean water, the hole is washed until the return water is clear, the air pressure or water pressure type plug is used for segmental isolation, the flow is continuously observed for 5 times under stable pressure, and the average value is calculated to obtain the water permeability when the fluctuation range is less than or equal to 10%.

14. The construction method for foundation anti-seepage treatment based on pre-splitting tension slots according to claim 1, characterized in that: In the S11, the coring inspection hole is located on the curtain axis, and the number is 3% to 10% of the total number of pre-split holes, and is mainly arranged in the areas with faults, fracture development or large slurry absorption; The morphology of the slurry stone body, the fracture filling density, and the compressive strength of the stone body are observed and tested; the qualified standard is that the slurry vein filling rate is greater than or equal to 90%, and the stone body is continuous without voids and is tightly cemented with the surrounding rock.

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