Grouting reinforcement method for karst area
By combining precise exploration using elastic wave CT and borehole television imaging with filling and grouting methods, the problems of precision and uniformity in grouting reinforcement of karst areas were solved, the reinforcement effect of karst areas was improved, construction risks were reduced, and efficient grouting reinforcement of karst areas was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-03-16
- Publication Date
- 2026-04-21
AI Technical Summary
Existing grouting reinforcement methods for karst areas suffer from insufficient accuracy in karst detection, poor selection of grouting materials, and inadequate control of construction techniques, resulting in poor reinforcement effects and an inability to effectively block the hydraulic connection between groundwater and soil cavities, thus posing safety hazards.
Precise exploration was conducted using elastic wave CT combined with borehole television imaging. The treatment area was defined based on engineering geological conditions. A combination of filling and grouting methods was adopted, with differentiated materials and parameters selected. Grouting pressure, speed, and volume were controlled to ensure uniform grout diffusion. Materials such as crushed stone, cement mortar, and two-component grout were used. Reinforcement was achieved through optimization of borehole layout and construction technology.
It achieves precise reinforcement of different types of karst areas, with uniform grout diffusion, improving the bearing capacity and stability of the foundation, reducing the risks in shield tunneling construction, and has significant economic and social benefits.
Abstract
Description
Technical Field
[0001] This invention relates to the field of tunnel construction technology, and in particular to a grouting reinforcement method for karst areas. Background Technology
[0002] Karst areas are characterized by complex geological conditions, with widespread geological defects such as karst cavities, soil caves, and dissolution fissures, which significantly impact the safety of engineering construction and subsequent operation. In shield tunnel construction, the adverse effects of karst manifest in two main ways: First, the soil layer overlying karst cavities is prone to forming soil caves under the influence of groundwater, leading to ground subsidence and compromising the stability of the structural foundation. Second, the fractured rock mass and dissolution structures beneath the structure's base will further expand over time, reducing the foundation's bearing capacity. Furthermore, the soft-over-hard strata and the distribution of beaded karst caves make it difficult to achieve earth pressure balance during shield tunneling, potentially causing problems such as arch collapse, soil loss at the working face, and excessive ground settlement. Karst caves at the tunnel bottom can also lead to sudden water and mud inrushes, shield machine head-down accidents, and extremely difficult subsequent handling.
[0003] Currently, grouting reinforcement in karst areas is the main means to solve the above problems, but existing construction methods have many shortcomings: First, the accuracy of karst detection is limited, and traditional exploration methods are difficult to accurately determine the boundary range, filling state, and water content of karst caves, resulting in blind spots in subsequent treatment; Second, the selection of grouting materials and parameters is not targeted enough, and it is impossible to carry out differentiated design according to the size of the karst cave, the filling type, and the stratum conditions, resulting in uneven grout diffusion, poor consolidation effect, and difficulty in effectively blocking the hydraulic connection between groundwater and soil caves; Third, the construction process control is not perfect, and the coordinated control of grouting pressure, speed, and grouting volume is unreasonable, which easily leads to problems such as grout loss and cross-contamination, reducing the quality of reinforcement and leaving safety hazards.
[0004] Therefore, there is an urgent need for a grouting reinforcement method that is accurate in detection, highly adaptable to parameters, and applicable to various types of karst areas, in order to overcome the shortcomings of existing technologies. Summary of the Invention
[0005] The purpose of this invention is to solve the above-mentioned problems and provide a grouting reinforcement method for karst areas that is applicable to various types of karst areas, and that ensures uniform grout diffusion during reinforcement, thereby improving the bearing capacity and stability of the foundation.
[0006] To achieve the above objectives, the technical solution of the present invention is: a grouting reinforcement method for karst areas, comprising the following steps: S1: Karst Exploration; Based on previous geological data, elastic wave CT method supplemented by borehole television imaging method is used for supplementary geological exploration to determine the location, distribution, size, filling condition and water-bearing status of karst caves; S2: Defining the scope of treatment; Based on the exploration results and engineering geological conditions, the scope of karst treatment is defined; S3: Grouting reinforcement construction: Taking into account the engineering geological conditions of the tunnel, the surrounding environment and construction technology, a combination of filling and grouting methods is used for reinforcement. S4: Quality Acceptance: Arrange inspection holes according to 5-10% of the total grouting holes. After all grouting holes meet the completion standard and the inspection holes meet the design requirements, the grouting reinforcement construction is completed.
[0007] Preferably, step S2 further includes the following steps: S21: All soil cavities above the rock surface within the scope of the project's impact shall be treated; S22: When the tunnel floor is limestone, after extending the structural outline by 1m, the karst caves within 2m below the tunnel floor should be treated. S23: When the tunnel is located in a sandy soil layer, the area under the tunnel invert is all sand and there is no stable water-resistant layer. After the tunnel structure outline is extended by 3m, the karst caves within 2m below the tunnel floor are treated.
[0008] Preferably, step S3 further includes the following steps: S31: Material and proportion determination; Select filling and grouting materials according to the size of the karst cave, filling conditions and water content. Filling materials include crushed stone, cement mortar and chemical grout, and grouting materials include two-component cement grout, water and water glass grout. S32: Drilling layout; Grouting holes, filling holes, and venting holes are arranged according to the height and distribution of the karst cave. When the karst cave height is ≤1m, one grouting hole is arranged at the exploratory borehole. When the karst cave height is 1m < karst cave height ≤ 3m, two grouting holes are arranged in a triangle around the exploratory borehole, with a spacing of 2.0m × 2.0m. When the karst cave height is > 3m, grouting holes are arranged in a quincunx pattern around the exploratory borehole, with a spacing of 2.0m × 2.0m, extending 2m outside the structure. The grouting holes extend at least 0.5m below the bottom plate of the karst cave, and the filling holes extend at least 1.0m into the cavity below the top plate of the karst cave. S33: Grouting construction; grouting pressure, speed and grouting volume are controlled according to design parameters, and grouting is completed by a combination of quantitative and pressure control for single holes.
[0009] Preferably, in step S31, the material ratio is as follows: the mass ratio of the two-liquid cement:water:water glass slurry is 1:1.0:0.3, the water glass modulus is 2.4 to 3.4, and the concentration is 30 to 40 Be.
[0010] Preferably, in step S31, the cement mortar is made of 42.5 ordinary Portland cement; the chemical grout is made of polyurethane or Mari-aluminum, used for sealing karst caves with large water inflow and significant safety risks.
[0011] Preferably, the water-cement ratio in the ordinary silicate cement is 1:1.0 to 1.5.
[0012] Preferably, the grouting pressure in step S33 is controlled according to the following standards: 0.2MPa~0.3MPa for the first round of grouting in the peripheral holes, and 0.6MPa~0.8MPa for the final grouting; 0.2MPa~0.3MPa for the first round of grouting in the central holes, and 0.8MPa~1.0MPa for the final grouting; the grouting pump pressure is 1.3~1.5 times the design grouting pressure; when sealing the water inflow, the final grouting pressure P=Po+(2~4)MPa, where Po is the water inflow pressure.
[0013] Preferably, in step S33, the grouting volume is calculated using the formula P=V×η×α, where V is the estimated volume of the karst cave, η is the filling coefficient, and α is the grout diffusion coefficient.
[0014] Compared with existing technologies, the grouting reinforcement method for karst areas disclosed in this invention has the following advantages: 1. Based on the location, scale, stratum type, and engineering structure requirements of karst, clarify the scope of differentiated treatment to avoid cost waste caused by over-treatment while ensuring thorough treatment and effectively covering risk points within the scope of project impact. In particular, establish a special demonstration mechanism for extra-large karst caves to improve construction safety. 2. Different reinforcement methods are selected for karst caves of different heights and filling states. The grout is evenly diffused and solidified, which can effectively fill the caves and solidify the fracture zone, as well as block the hydraulic connection between groundwater and soil caves, improve the bearing capacity and stability of the foundation, and fundamentally reduce the risks of arch collapse, water inrush and mud inrush during shield tunneling. 3. It can be applied to grouting reinforcement construction of shield tunnels and geotechnical engineering in various karst areas. The material selection takes into account both reliability and economy. The construction technology is mature and easy to operate. No special large equipment is required, which facilitates promotion and application. At the same time, it reduces the cost of later maintenance and rectification, and has significant economic and social benefits. Detailed Implementation
[0015] A grouting reinforcement method for karst areas specifically includes the following steps: Step S1, Karst Exploration: Upon arrival at the site, a qualified professional exploration unit was commissioned to immediately organize and implement supplementary geological exploration work, combining the geological exploration data collected in the early stage. Through a combination of physical exploration and geological drilling, detailed exploration was conducted on the karst caves and soil caves in the karst development area. The core method used was elastic wave CT supplemented by borehole television imaging to ensure the accuracy of the detection.
[0016] The elastic wave CT method employs a cross-hole CT observation system. The specific field data acquisition method involves excitation at hole 1 and reception at hole 2, with the distance between the excitation and reception points set at 0.5m. The operation procedure is as follows: First, the receiver is fixed at the bottom of hole 2. Receivers can be used individually or in a series of 12, with a series spacing of 0.5m. Then, the transmitter is used to excite points upwards from the bottom of hole 1, with a point spacing of 0.5m, until the vertical height between the excitation and reception points exceeds the hole spacing or the transmitter reaches the opening of hole 1. Next, the receiver is moved upwards with a movement distance of 0.5m, and the above excitation and reception operation is repeated until the receiver reaches the opening of hole 2, completing the cross-hole elastic wave data acquisition.
[0017] Borehole television imaging utilizes a full-hole-wall digital imaging system. Testing is conducted continuously from the borehole opening to the bottom. Before testing, the borehole must be repeatedly flushed to remove any residual material adhering to the borehole wall, ensuring the well fluid is clear and transparent to avoid affecting the imaging results. During on-site testing, the downhole equipment must be lowered smoothly and at a constant speed to ensure clear and discernible images and accurate depth recording. Depth correction is performed every 5-10 meters to improve data reliability. Later, combined with geological data from the infiltrated boreholes, the imaging images are precisely interpreted, analyzing the distribution characteristics of different lithological interfaces and karst within the rock mass. This results in a detailed exploration report, clearly defining the distribution, size, infill type, and water-bearing status of karst caves within each area, providing a basis for subsequent processing.
[0018] Step S2, Scope of processing: Based on the detection results of step S1, and combined with the engineering structural design requirements and geological conditions, the scope of karst treatment is scientifically defined, with the following specific standards: 1. All soil cavities found above the rock surface within the project's impact area must be thoroughly treated to prevent the cavities from expanding under the influence of groundwater and causing ground subsidence; 2. When the tunnel floor is composed of limestone strata, the karst caves within 2 meters below the tunnel floor must be treated, provided that the tunnel structure extends 1 meter outward from the tunnel floor outline, to ensure the stability of the tunnel boring machine operation and the tunnel foundation. 3. When the tunnel is located in a sandy soil layer, two situations are defined: ① If there is a relatively stable aquitard (such as clay or silty clay) at the bottom of the tunnel invert, and the thickness of the aquitard is greater than 2m, the karst below the aquitard does not need to be treated; ② If the bottom of the tunnel invert is all sand or there is no stable aquitard, after the tunnel structure outline is extended 3m outward, the karst (soil) cavities within 2m below the tunnel floor must be treated to avoid sand layer collapse causing water and mud inrush accidents. 4. For special karst distributions not covered above, a special demonstration should be conducted by the design, supervision, construction, owner, and surveying units to determine a reasonable scope of treatment; 5. Considering the uncertainty of karst cave development, if an extra-large karst cave (cavity size greater than or equal to 5m) exceeding the above treatment range is discovered during construction, related work must be stopped immediately, a special meeting must be held, and all parties involved must work together to determine whether to treat it and the corresponding treatment plan to ensure the safety of construction and subsequent operation.
[0019] Step S3, Grouting Reinforcement Construction: Taking into account the geological conditions of the tunnel, the surrounding buildings and structures, the shield tunneling technology, and the requirements for economy, reliability, and durability, this method adopts a combination of filling and grouting for karst reinforcement. The core is to use differentiated materials, parameters, and construction techniques according to the type and scale of the karst cave.
[0020] S31. Material and Proportion Determination: The main filling materials are crushed stone and cement mortar, while the main grouting materials are cement grout and two-component grout (cement-water glass). In special cases, chemical grouts such as polyurethane and malachite are used. The selection and proportioning of materials shall follow the following principles and shall be determined through verification production tests before formal construction. The test results shall be submitted to the supervising engineer for approval and the design for approval before they can be used for formal construction: 1. Filling materials: ① Cement mortar: The cement-sand mix ratio is controlled at 1:2 to 1:2.5, which can be adjusted appropriately according to the results of on-site tests; ② Crushed stone: Select hard, clean crushed stone with good particle shape and gradation, and control the particle size at 5mm to 10mm to ensure the compactness of the filling. 2. Grouting materials: ① Cement grout: 42.5 ordinary Portland cement is used, with a water-cement ratio controlled between 0.4:1 and 1:1, adjusted according to the grouting stage and the formation's grout absorption capacity; ② Two-component grout: water glass modulus 2.4–3.4, concentration 30–45 Be', cement:water:water glass mass ratio 1:1.0:0.3, used for edge sealing when grout loss is severe; ③ Chemical grout: polyurethane, Marifen, used only when there is a large inflow and significant safety risk, and used in conjunction with other materials to achieve efficient sealing; 3. Auxiliary materials: The grout stop at the orifice uses ∅65×3.75 welded steel pipe, anchoring agent and mechanical grout stop plug; the grouting pipe uses ∅48*4.5 PVC pipe; the feeding pipe uses ∅200*8 PVC pipe.
[0021] S32. Grouting parameter design: 1. Grouting diffusion radius: The diffusion radius is selected by engineering analogy method. When the filling material is silty soil or silty clay soil, the diffusion radius is 1m to 1.5m; when the filling material is sandy soil, the diffusion radius is 2m to 2.5m. It is determined and corrected during construction based on grouting test or verification of the grouting effect in the early stage. 2. Grouting Hole Layout: ① For cave height ≤ 1m: Layout one grouting hole at the exploration borehole where the cave has been exposed; ② For cave height ≤ 3m: Layout two grouting holes in a triangular pattern around the exploration borehole, spaced 2.0m × 2.0m apart; ③ For cave height > 3m: Layout grouting holes in a quincunx pattern around the exploration borehole, spaced 2.0m × 2.0m apart, extending 2m beyond the structure; If the cave has a finite boundary and the outermost row of holes does not expose the cave, then this hole does not need grouting, and one hole is recessed inward as a side hole for grouting treatment; ④ The grouting hole extends at least 0.5m below the cave floor, and the rock-filling hole extends at least 1.0m into the cavity below the cave roof; When the final borehole section encounters karst with poor properties and large scale, or a zone with densely developed fissures, deepen the borehole to 0.5m into the lower intact rock mass; ⑤ 200mm diameter PVC pipes are used for filling crushed stone holes, with a hole spacing of 4m, and the holes are evenly distributed according to the boundary of the karst cave; sleeve valve pipes or welded steel pipes are used for grouting holes to reduce the risk of grout leakage, and can be adjusted appropriately according to the site conditions; ⑥ Venting holes are set during the grouting process, and the number is determined according to the size of the karst cave to ensure the grout filling is complete. 3. Grouting pressure: The first round grouting pressure for peripheral holes is 0.2MPa~0.3MPa, and the final grouting pressure is 0.6MPa~0.8MPa; the first round grouting pressure for central holes is 0.2MPa~0.3MPa, and the final grouting pressure is 0.8MPa~1.0MPa; the grouting pump pressure needs to reach 1.3~1.5 times the design pressure; when sealing water inflow, the final grouting pressure is calculated according to the formula P=Po+(2~4)MPa, where Po is the water inflow pressure; 4. Grouting speed: Controlled according to the grout absorption capacity (porosity) of the formation and the power parameters of the grouting equipment, and dynamically adjusted according to the actual situation during construction to ensure uniform diffusion of grout; 5. Grouting volume: ① The grouting volume per hole is calculated using the formula Q=πD² / 4·L·n·α·η, where Q is the grouting volume, D is the grouting range, L is the grouting section length, n is the soil porosity or rock fracture ratio, α is the grout filling coefficient, and η is the grout consumption rate; ② The overall grouting volume is calculated using the formula P=V×η×α (V is the estimated volume of the karst cave, η is the filling coefficient, and α is the grout diffusion coefficient). Karst caves with different filling states are refined according to the following standards: For fully filled karst caves, P1=V×0.4 when grouting with cement grout; for semi-filled karst caves, grouting is carried out according to height using cement mortar (height ≤ 3m) or a combination of crushed stone + cement grout (height > 3m), and the corresponding grouting volume is calculated proportionally; for unfilled karst caves, grouting is carried out according to height using cement mortar (1m < height ≤ 3m), cement grout (height ≤ 1m), or a combination of crushed stone + cement grout (height > 3m); dual-liquid grout and chemical grout are used as auxiliary measures, and the grouting volume is based on on-site measurement. Note: The above grouting volume is a theoretical value and does not take into account losses. In actual construction, it is necessary to combine the rock fissures around the karst cave, the connectivity of the karst cave, and the influence of groundwater. The grout diffusion coefficient should be determined through on-site tests, and adjusted after confirmation by all parties. The final grouting volume shall be based on the actual amount generated on site.
[0022] S33. Construction process flow and control: Grouting construction must be carried out strictly according to the following procedures: borehole layout → soil drilling (casing installation) → bedrock drilling → simple water pressure test → grouting → borehole sealing, while ensuring the following key control points are met: 1. Pre-construction preparation: Determine the location, direction and burial depth of all underground pipelines in the construction area, and relocate or reinforce pipelines that may affect grouting construction; install ground settlement and deformation monitoring points, complete initial value monitoring, and monitor in real time during construction to avoid excessive ground settlement; 2. Selection of Mechanical Equipment: Select drilling rigs and grouting pumps with low failure rate, easy maintenance, readily available spare parts, and easy mobility to ensure efficient drilling and grouting; the grouting pump pressure must meet design requirements and be equipped with an automatic recorder to measure and record grouting flow rate, pressure, and time in real time; all equipment should be properly maintained and equipped with sufficient backup equipment to ensure construction continuity; 3. Grouting process control: During grouting, follow the principle of "from thin to thick, step by step" and adjust the grout concentration according to changes in pressure and grout absorption. If ordinary cement grout is severely lost, first use double-liquid grout to seal the edges, and then carry out internal grouting. During construction, record all original data truthfully and accurately, including grouting volume, pressure, time, grout mix ratio, and geological anomalies. Record construction accidents, abnormal phenomena, and damage to monitoring facilities in detail and report them to the supervisor, owner, and design unit in a timely manner for collaborative research and handling. 4. Grouting Completion Criteria: ① Single Hole Completion Criteria: Combining quantitative and pressure control, if the grouting volume reaches 1.2 times the design volume but there is still no pressure rise, a five-party meeting will be held to determine measures such as using double-liquid grout to shorten the gel time, and the grouting will be completed after the pressure reaches the design final pressure; or, if each hole section reaches the design final pressure and stabilizes for 10 minutes, and the grouting speed is 1 / 4 of the initial speed or the grouting volume reaches 80% of the design volume, the grouting of that hole can be completed; ② Entire Section Completion Criteria: All designed grouting holes meet the completion criteria, with no missed grouting; inspection holes meet the design requirements; the cement grout water-cement ratio can be adjusted within the range of 0.4, 0.6, 0.8, and 1.0 according to the site conditions.
[0023] Step S4, Quality Acceptance: Grouting reinforcement is a concealed project, and its quality acceptance must be strictly carried out in accordance with the following requirements: 1. After the completion of each unit project, promptly organize and analyze all construction data, including core sampling, water pressure test, grouting records, geophysical testing, ground settlement and deformation observation, and quality inspection data, and submit them to the owner, supervisor, and design unit; 2. Arrange inspection holes at 5-10% of the total grouting holes, and check the grouting effect by means of core sampling, water pressure test, etc., to ensure that the bearing capacity, impermeability and stability of the reinforced foundation meet the design requirements; 3. Only after all inspection holes are qualified and the construction data is complete and accurate, and the quality acceptance is completed, can subsequent construction procedures such as tunnel boring be carried out.
[0024] Furthermore, in the present invention, if the following abnormalities occur during the grouting process: ① Grouting interruption A. Identify the cause of the grouting interruption, resolve it as soon as possible, and resume grouting as early as possible; B. If grouting cannot be resumed immediately or there is a risk of pipe burial when injecting thick grout, flush the core pipe immediately and then resume grouting; C. When the injection rate decreases significantly after grouting is resumed and grouting stops within a short period of time, remedial measures should be taken.
[0025] ② Significant grout leakage When a large amount of grout leakage occurs, the following principles are generally adopted for handling: The grouting is carried out using a low-pressure, concentrated slurry, flow-limited, volume-limited, and intermittent grouting method, with an interval of 6 to 8 hours. If necessary, mortar or other filling materials can be used to first seal the large gaps before treating them using method 1); To shorten the grout setting time, cement-water glass or other quick-setting materials can be used for grouting.
[0026] ③ During the grouting process, grout flows out from other boreholes.
[0027] The main measures to prevent cross-contamination of grout are: increasing the spacing between the first-sequence holes; appropriately extending the interval between the construction of two adjacent sequences, and waiting for the grout from the previous sequence hole to basically solidify before starting the drilling work of the next sequence hole.
[0028] Treatment measures after cross-grouting occurs: If the cross-grouting hole is grouting condition, grouting can be carried out simultaneously, one pump for one hole; otherwise, the cross-grouting hole should be plugged. After the grouting of the injection hole is completed, the cross-grouting hole should be swept and flushed, and then drilling and grouting can continue.
[0029] Surface grouting: When dealing with surface grouting, low-pressure or gravity-flow grouting should be used, while increasing the grout concentration. If necessary, fine sand or other materials should be added. After the grouting path is blocked, the grouting pressure should be gradually increased and grouting should be performed at the normal grouting pressure. Intermittent grouting can also be used to deal with the problem.
[0030] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.
Claims
1. A grouting reinforcement method for karst areas, characterized in that, Includes the following steps: S1: Karst Exploration; Based on previous geological data, elastic wave CT method supplemented by borehole television imaging method is used for supplementary geological exploration to determine the location, distribution, size, filling condition and water-bearing status of karst caves; S2: Defining the scope of treatment; Based on the exploration results and engineering geological conditions, the scope of karst treatment is defined; S3: Grouting reinforcement construction: Taking into account the engineering geological conditions of the tunnel, the surrounding environment and construction technology, a combination of filling and grouting methods is used for reinforcement. S4: Quality Acceptance: Arrange inspection holes according to 5-10% of the total grouting holes. After all grouting holes meet the completion standard and the inspection holes meet the design requirements, the grouting reinforcement construction is completed.
2. The grouting reinforcement method for karst areas according to claim 1, characterized in that, Step S2 further includes the following steps: S21: All soil cavities above the rock surface within the scope of the project's impact must be treated; S22: When the tunnel floor is limestone, after extending the structural outline by 1m, the karst caves within 2m below the tunnel floor slab should be treated. S23: When the tunnel is located in a sandy soil layer, the area under the tunnel invert is all sand and there is no stable water-resistant layer. After the tunnel structure outline is extended by 3m, the karst caves within 2m below the tunnel floor are treated.
3. The grouting reinforcement method for karst areas according to claim 1, characterized in that, Step S3 further includes the following steps: S31: Material and proportion determination; Select filling and grouting materials according to the size of the karst cave, filling conditions and water content. Filling materials include crushed stone, cement mortar and chemical grout, and grouting materials include two-component cement grout, water and water glass grout. S32: Drilling layout; Grouting holes, filling holes, and venting holes are arranged according to the height and distribution of the karst cave. When the karst cave height is ≤1m, one grouting hole is arranged at the exploratory borehole. When the karst cave height is 1m < karst cave height ≤ 3m, two grouting holes are arranged in a triangle around the exploratory borehole, with a spacing of 2.0m × 2.0m. When the karst cave height is > 3m, grouting holes are arranged in a quincunx pattern around the exploratory borehole, with a spacing of 2.0m × 2.0m, extending 2m outside the structure. The grouting holes extend at least 0.5m below the bottom plate of the karst cave, and the filling holes extend at least 1.0m into the cavity below the top plate of the karst cave. S33: Grouting construction; grouting pressure, speed and grouting volume are controlled according to design parameters, and grouting is completed by a combination of quantitative and pressure control for single holes.
4. The grouting reinforcement method for karst areas according to claim 1, characterized in that, In step S31, the material ratio is as follows: the mass ratio of the two-liquid cement:water:water glass slurry is 1:1.0:0.3, the water glass modulus is 2.4 to 3.4, and the concentration is 30 to 40 Be.
5. The grouting reinforcement method for karst areas according to claim 3, characterized in that, In step S31, the cement mortar uses 42.5 ordinary Portland cement; the chemical grout uses polyurethane or Mari-aluminum, which is used for sealing karst caves with large water inflow and significant safety risks.
6. The grouting reinforcement method for karst areas according to claim 5, characterized in that, The water-cement ratio in the ordinary silicate cement is 1:1.0 to 1.
5.
7. The grouting reinforcement method for karst areas according to claim 1, characterized in that, In step S33, the grouting pressure is controlled according to the following standards: for the peripheral holes, the first round is 0.2MPa to 0.3MPa, and the final grouting is 0.6MPa to 0.8MPa; for the central holes, the first round is 0.2MPa to 0.3MPa, and the final grouting is 0.8MPa to 1.0MPa; the grouting pump pressure is 1.3 to 1.5 times the design grouting pressure; when sealing the water inflow, the final grouting pressure P = Po + (2 to 4)MPa, where Po is the water inflow pressure.
8. The grouting reinforcement method for karst areas according to claim 1, characterized in that, In S33, the grouting volume is calculated using the formula P=V×η×α, where V is the estimated volume of the karst cave, η is the filling coefficient, and α is the grout diffusion coefficient.