Construction method for rapid plugging and grouting of leakage under anti-seepage wall in strong karst area

Abstract

The present application belongs to the technical field of water conservancy and hydropower engineering foundation treatment, and particularly relates to a construction method for rapid leakage plugging and grouting under a seepage wall in a strong karst area, comprising: determining a grouting hole position; using a pilot hole and a grouting borehole to perform dynamic geological exploration during the drilling process to obtain information such as the type, size and location of karst geological defects; based on the exploration information, performing corresponding pretreatment on different types of defects such as unfilled caves, fully filled caves and caves with water flow; then using the orifice closed segmented grouting method to perform seepage control grouting construction on the areas that have completed pretreatment and normal areas, and performing karst control grouting on the large injection volume section, and after special treatment, re-scanning the hole for regular grouting to ensure quality; finally, verifying the grouting quality by arranging inspection holes for water pressure test. The method solves the technical problems of difficulty in grouting curtain formation and uncontrollable quality under the seepage wall in the strong karst area through dynamic exploration, classified treatment and process closed loop.

Description

Technical Field

[0001] This invention belongs to the field of foundation treatment technology for water conservancy and hydropower projects, and particularly relates to a construction method for rapid sealing and grouting of seepage under an anti-seepage wall in a strong karst area. Background Technology

[0002] In the construction of high dams in karst regions, the seepage prevention system, especially the bedrock grouting under the cutoff wall (including the contact zone between the cutoff wall and the bedrock), is crucial to ensuring dam safety and preventing reservoir leakage. The geological conditions in strongly karst areas are extremely complex, typically characterized by widespread soluble rocks, solution fissures, caves (including fully filled, partially filled, and unfilled), karst conduits (including those with and without water flow), and interlayer shear zones, thus forming karst seepage channels (including dispersed and concentrated seepage channels). Grouting under the cutoff wall in such strata aims to create a continuous seepage prevention curtain penetrating deep into the relatively impermeable rock mass; its quality directly affects the seepage stability of the dam foundation and the safety of the project.

[0003] However, existing conventional grouting technologies and processes face numerous significant challenges when dealing with the specific combination of "strong karst areas" and "under the cutoff wall." First, conventional grouting processes are insufficiently targeted at treating karst caves of varying shapes and filling materials, easily leading to problems such as significant grout loss, difficulty in establishing grouting pressure, lengthy treatment cycles, and uncertain results, making it difficult to form a complete and reliable cutoff curtain. Second, the ultra-deep grouting holes required to reach the aquitard layer are extremely difficult to control in heterogeneous strata such as karst and alternating layers of soft and hard materials, easily resulting in poorly overlapping "shorts-shaped" quality defects in the deep layers of the curtain. Third, there is a lack of a standardized construction process from dynamic exploration and classification assessment of karst geology to targeted treatment; on-site decisions often rely on experience, resulting in arbitrary treatment measures and significant risks to project quality and construction safety. These shortcomings (including the contact zone between the cutoff wall and the bedrock) collectively lead to difficulties in guaranteeing seepage prevention effects, low construction efficiency, and uncontrollable costs when grouting under the cutoff wall in strong karst areas.

[0004] Therefore, there is an urgent need for a construction method for rapid sealing and grouting of seepage under the anti-seepage wall in strong karst areas to solve the above problems. Summary of the Invention

[0005] The purpose of this invention is to provide a construction method for rapid sealing and grouting of seepage under the anti-seepage wall in strong karst areas, so as to solve the above-mentioned problems.

[0006] To achieve the above objectives, the present invention provides the following solution: A construction method for rapid sealing grouting under a seepage barrier in a strong karst area includes the following steps: Determine the grouting hole locations.

[0007] Construction exploration is conducted to obtain karst geological information of the construction area below the anti-seepage wall foundation where the grouting holes are located. The karst geological information includes at least the type, scale, and location of karst geological defects.

[0008] Based on the karst geological information, corresponding preprocessing is performed on different types of karst geological defects.

[0009] Anti-seepage grouting construction was carried out on the pre-treated areas and normal areas.

[0010] After the grouting work is completed, the grouting quality is verified.

[0011] Optionally, the step of determining the grouting hole location includes: Based on the construction design drawings, measurements were taken and the center positions of each grouting hole were marked on the concrete surface of the anti-seepage wall base.

[0012] The order of grouting holes is dynamically adjusted according to design requirements and leakage conditions.

[0013] Each grouting hole is uniquely numbered according to the design requirements.

[0014] Optionally, the step of obtaining the karst geological information of the construction area below the anti-seepage wall foundation for the grouting hole locations includes: During the drilling process at the grouting holes, pilot holes and grouting holes are used to conduct dynamic geological exploration during the construction period in order to quickly determine the leakage situation under the wall.

[0015] Optionally, the leakage under the wall includes leakage at the contact zone between the wall and the karst strata, and karst leakage in the bedrock under the wall.

[0016] Among them, karst leakage in the bedrock beneath the wall includes leakage caused by one or more karst geological defects such as dissolution fissures, caves, and karst conduits.

[0017] Among them, karst caves include unfilled karst caves, semi-filled karst caves, and fully filled karst caves.

[0018] Karst conduits include both conduits with and without water flow.

[0019] Optional, When the leakage under the wall is at the contact zone between the wall and the karst strata, with the design approval, the construction sequence of the grouting holes is adjusted, that is, the downstream drain is constructed first, and the upstream drain is constructed first. Depending on the amount of leakage, one or more of the sealing methods such as sand-mixed grouting, two-liquid grouting, and chemical grouting are used for rapid sealing treatment.

[0020] When the type of karst geological defect in the bedrock is an unfilled cave, obtain the size of the unfilled cave.

[0021] When the size of the unfilled karst cave is such that the depth of the drill bit falls is greater than a set threshold, high-flow fine stone concrete or cement mortar is pumped into the karst cave for backfilling, and the hole is swept after it sets.

[0022] When the size of the unfilled karst cave is such that the depth of the drill bit drop is less than or equal to the set threshold, graded sand is injected into the karst cave or hydraulic flushing is used for backfilling.

[0023] Optionally, when the type of karst geological defect is a fully filled cave, the type of filling material of the fully filled cave is obtained.

[0024] When the filling material of the fully filled karst cave is mainly clay, the grouting pressure should be increased, and high-pressure flushing grouting or high-pressure replacement grouting should be used for treatment.

[0025] When the filling material of the fully filled karst cave is mainly sand, high-pressure jet grouting is used for treatment.

[0026] Optionally, when the karst geological defect is a water-flowing cave, an epoxy resin-based chemical grout that can solidify under flowing water conditions is injected into the water-flowing cave.

[0027] Optionally, the steps for performing anti-seepage grouting construction include: Curtain grouting was carried out using a method of sealing the orifice, circulating inside the orifice, and grouting in sections from top to bottom.

[0028] During the grouting process, when encountering a grouting section with a large injection volume that is difficult to complete, karst-controlled grouting is implemented.

[0029] After completing the pretreatment for karst geological defects or the karst control grouting, the borehole is re-scanned and conventional grouting is performed on the borehole section until the designed grouting completion criteria are met.

[0030] Optionally, the steps for verifying grouting quality include: After the anti-seepage grouting construction is completed and the specified curing period is reached, inspection holes are arranged in the construction area according to a preset ratio.

[0031] The inspection hole was subjected to segmented drilling and water pressure testing.

[0032] Based on the results of the water pressure test, determine whether the grouting quality of the construction area meets the design requirements.

[0033] Optionally, karst controlled grouting methods include one or more of the following: low-pressure grouting, thick grouting, flow-limited grouting, volume-limited grouting, intermittent grouting, waiting for setting, re-grouting, grouting stable grout, grouting mixed grout, and grouting paste grout.

[0034] Compared with the prior art, the present invention has the following advantages and technical effects: This invention establishes a standardized construction process from dynamic exploration and classification assessment to targeted treatment, changing the traditional approach of blindly relying on experience in strong karst areas. Real-time geological exploration and information acquisition during construction provide accurate basis for subsequent decision-making. Classified pretreatment measures based on the type, size, and infill material properties of karst caves significantly improve the targeting and effectiveness of treating different types of karst defects. Combined with specialized grouting technology and a rigorous quality verification closed loop, it enhances the certainty of forming a continuous and reliable seepage barrier in complex and heterogeneous strata. This method is highly systematic, helping to improve the controllability of the construction process and the reliability of project quality, and plays a positive role in ensuring the seepage prevention safety of dam foundations in strong karst areas. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described 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. Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0038] Reference Figure 1 This invention discloses a construction method for rapid sealing grouting under a seepage barrier in a strong karst area, comprising the following steps: Determine the grouting hole locations.

[0039] Construction exploration is conducted to obtain karst geological information of the construction area below the anti-seepage wall foundation where grouting holes are located. The karst geological information includes at least the type, scale, and location of karst geological defects.

[0040] Based on karst geological information, corresponding preprocessing is performed on different types of karst geological defects.

[0041] Anti-seepage grouting construction was carried out on the pre-treated areas and normal areas.

[0042] After the grouting work is completed, the grouting quality is verified.

[0043] This invention first involves surveying and setting out according to the design to determine the grouting hole locations on the concrete surface of the anti-seepage wall foundation. Subsequently, during drilling, pilot holes and grouting boreholes are used for exploration to dynamically acquire key karst geological information, such as the type, scale, and location of karst defects below the borehole locations. Based on this information, different types of defects, including unfilled caves, fully filled caves, and caves with water flow, are pretreated accordingly, including pumped concrete backfilling, high-pressure flushing and replacement, and chemical grouting. After pretreatment, anti-seepage grouting is uniformly applied to both defective and normal areas using the borehole-sealing grouting method. Karst-controlled grouting is implemented in sections with large injection volumes, and after special treatment, the boreholes are re-scanned for conventional grouting until the standards are met. After all grouting is completed, inspection holes are installed and a water pressure test is conducted to verify the grouting quality. The implementation of this method has yielded significant results: its systematic "exploration-classification-treatment" process completely changes the blind approach of traditional techniques in highly karst areas. Through precise identification and targeted pretreatment of various types of karst, the effectiveness of subsequent grouting is ensured. Combined with specialized grouting techniques and rigorous quality verification, a continuous, reliable curtain meeting anti-seepage standards can ultimately be formed under extremely complex geological conditions. This fundamentally solves the core technical problems of difficult grouting curtain formation and uncontrollable quality under anti-seepage walls in highly karst areas, significantly improving construction efficiency and project safety and reliability.

[0044] As an optional implementation, the step of determining the grouting hole location includes: Based on the construction design drawings, measurements were taken and the center positions of each grouting hole were marked on the concrete surface of the anti-seepage wall base.

[0045] The order of grouting holes is dynamically adjusted according to design requirements and leakage conditions.

[0046] Each grouting hole is uniquely numbered according to the design requirements.

[0047] First, based on the construction design drawings, the center position of each grouting hole was precisely marked on the concrete surface of the anti-seepage wall foundation through measurement and layout. Then, the construction area was divided into grouting units according to the design. Finally, each hole was assigned a unique number according to a predetermined numbering rule. This process ensured accurate positioning of all holes, clear zoning of construction tasks, and provided clear identification for subsequent drilling, grouting, and quality recording, achieving orderly management and quality traceability throughout the construction process.

[0048] As an optional implementation method, the steps for obtaining karst geological information of the construction area below the anti-seepage wall foundation regarding the grouting hole locations include: During the drilling process at the grouting holes, pilot holes and grouting holes are used to conduct dynamic geological exploration during the construction period in order to quickly determine the leakage situation under the wall.

[0049] Dynamic geological exploration was conducted to determine the karst geological information of the grouting well locations.

[0050] During the drilling of grouting boreholes, pilot holes and grouting boreholes are used simultaneously for dynamic geological exploration. This dynamic exploration allows for the real-time identification of key karst geological information, such as the type, scale, and location of karst defects encountered at the grouting boreholes. This process integrates geological exploration into construction, enabling real-time information acquisition and updating, and providing a direct and reliable basis for subsequent precise and efficient classification and treatment decisions.

[0051] As an optional implementation method, leakage under the wall includes leakage at the contact zone between the wall and the karst strata, and karst leakage in the bedrock under the wall.

[0052] Among them, karst leakage in the bedrock beneath the wall includes leakage caused by one or more karst geological defects such as dissolution fissures, caves, and karst conduits.

[0053] Among them, karst caves include unfilled karst caves, semi-filled karst caves, and fully filled karst caves.

[0054] Karst conduits include both conduits with and without water flow.

[0055] As an optional implementation method, when the leakage under the wall is at the contact zone between the wall and the karst stratum, with the design approval, the construction sequence of the grouting holes can be adjusted, that is, the downstream drain can be constructed first, and depending on the amount of leakage, one or more sealing methods such as sand-mixed grouting, two-liquid grouting, and chemical grouting can be used for rapid sealing treatment.

[0056] When the type of karst geological defect in the bedrock is an unfilled cave, obtain the scale of the unfilled cave.

[0057] When the size of the unfilled karst cave is such that the depth of the drill bit falls beyond the set threshold, high-flow fine stone concrete or cement mortar is pumped into the karst cave for backfilling, and the hole is swept after it has set.

[0058] When the size of the unfilled karst cave is such that the depth of the drill drop is less than or equal to the set threshold, graded sand is injected into the karst cave or hydraulic flushing of the borehole is used for backfilling.

[0059] When karst geological defects are found to be unfilled cavities, their size is first determined, i.e., the depth of the drill bit fallout is measured. If the depth of the drill bit fallout is greater than a set threshold, high-flowability fine-aggregate concrete or cement mortar is pumped into the cavity for backfilling. If the depth of the drill bit fallout is less than or equal to the set threshold, graded sand is added or hydraulic flushing of the borehole is used for backfilling. In both cases, the borehole must be cleaned after backfilling to allow it to set. This tiered backfilling strategy matches appropriate filling materials to cavities of different sizes, ensuring that the cavities are effectively and densely filled, laying a solid foundation for the subsequent formation of a continuous impermeable body.

[0060] The preferred threshold value is 2m.

[0061] The "drop depth" is a field record directly obtained during drilling at grouting locations. When the drill bit enters an unfilled karst cave, it will lose support and "drop" into the karst cave. Operators can accurately measure and record the depth from the borehole opening to the top of the karst cave, as well as the length of the "dropped" section through the karst cave, using drilling records such as drill rod advance on the drilling rig. This length is the "drop depth." This information is one of the direct results of dynamic geological exploration.

[0062] As an optional implementation, when the type of karst geological defect is a fully filled cave, the type of filling material of the fully filled cave is obtained.

[0063] When the filling material of a fully filled karst cave is mainly clay, increase the grouting pressure and use high-pressure flushing grouting or high-pressure replacement grouting for treatment.

[0064] When the filling material of a fully filled karst cave is mainly sand, high-pressure jet grouting is used for treatment.

[0065] When a karst geological defect is identified as a fully filled cave, the first step is to determine the type of filling material. If the filling material is primarily clay, the grouting pressure is increased, and high-pressure flushing grouting or high-pressure replacement grouting is used. If the filling material is primarily sand, high-pressure jet grouting is employed. This step matches the most effective treatment technology to the different physical properties of the filling material, effectively compacting or replacing the material within the cave, significantly improving its groutability and impermeability, and clearing a key obstacle for the subsequent formation of a continuous anti-seepage curtain.

[0066] As an alternative implementation method, when the type of karst geological defect is a water-flowing cave, an epoxy resin-based chemical grout that can solidify under flowing water conditions is injected into the water-flowing cave.

[0067] When a karst geological defect is identified as a water-flowing cave, an epoxy resin-based chemical grout that can solidify under flowing water conditions is injected into the cave. This step, by selecting a chemical grout with special erosion resistance and rapid curing properties, effectively overcomes the problem of ordinary cement grout being easily diluted and washed away in flowing water. It ensures that the grout can be effectively retained, gelled, and solidified within the seepage channel, thereby reliably sealing the water-flowing cave and cutting off an important concentrated leakage channel.

[0068] Among them, epoxy resin-based chemical grouts that can cure under dynamic water conditions can effectively cure in dynamic water environments by selecting suitable water-based epoxy resins, underwater-specific curing agents, and possibly adding additives that promote underwater curing, such as certain hydrophilic modifiers, thereby sealing leakage channels. Compared to solvent-based epoxy, water-based systems also have advantages in terms of construction safety and environmental friendliness.

[0069] As an optional implementation method, the steps for performing anti-seepage grouting construction include: Curtain grouting was carried out using a method of sealing the orifice, circulating inside the orifice, and grouting in sections from top to bottom.

[0070] During the grouting process, when encountering a grouting section with a large injection volume that is difficult to complete, karst-controlled grouting is implemented.

[0071] After completing the pretreatment of karst geological defects or karst control grouting, the borehole is re-scanned and conventional grouting is performed on the borehole section until the designed grouting completion criteria are met.

[0072] First, curtain grouting is performed using a method of orifice sealing, internal circulation, and top-down segmented grouting. If a grouting section with a large injection volume is encountered and difficult to complete, karst-controlled grouting is implemented. After pretreatment of karst defects or karst-controlled grouting, the borehole is re-scanned and conventional grouting is performed on the same section until the design completion standard is met. This step combines high-pressure grouting technology adapted to deep boreholes, special control measures for high grout consumption sections, and a closed-loop re-grouting system to ensure final quality, thereby constructing a complete, dense, and reliable seepage-proof curtain in complex karst formations.

[0073] As an optional implementation, the steps for verifying grouting quality include: After the anti-seepage grouting construction is completed and the specified curing period is reached, inspection holes are arranged in the construction area according to the preset ratio.

[0074] The inspection holes were drilled in sections and subjected to water pressure tests.

[0075] Based on the results of the water pressure test, determine whether the grouting quality of the construction area meets the design requirements.

[0076] After the anti-seepage grouting construction is completed and the specified curing period is reached, inspection holes are arranged in the construction area according to a predetermined ratio. The inspection holes are then drilled in sections and subjected to water pressure tests. Based on the permeability results obtained from the water pressure tests, it is determined whether the grouting quality in the construction area meets the design requirements. This step, through independent and objective physical sampling and hydraulic testing, provides the final quantitative verification of the quality of the concealed grouting curtain. It is an indispensable key quality loop to ensure that the grouting project under the anti-seepage wall in strongly karst areas achieves the expected anti-seepage standards and realizes the safe and reliable operation of the project.

[0077] As an optional implementation method, karst controlled grouting methods include one or more of the following measures: low-pressure grouting, thick grouting, flow-limited grouting, volume-limited grouting, intermittent grouting, waiting for setting, re-grouting, grouting stable grout, grouting mixed grout, and grouting paste grout.

[0078] Taking the Xiangyang Reservoir seepage control project as an example, the core of this project lies in the bedrock grouting under the asphalt concrete core wall of the dam. This project aims to construct a reliable seepage barrier that penetrates deep into the bedrock at the base of the core wall. Given that the project area is located in a zone of strong karst development, with lithology mainly consisting of argillaceous limestone and microcrystalline limestone, and with well-developed solution fissures, caverns, and interlayer shear zones forming potential concentrated seepage channels, the construction technology adopted must be specifically designed for these unique geological conditions to ensure the continuity and effectiveness of the seepage barrier. The entire construction process follows a systematic procedure, starting from the preparation of the working face and the construction of specialized construction equipment, all the way to the final quality verification. Each step must be closely integrated with the actual geological conditions revealed on site.

[0079] The initial stage of construction involves preparing the working face and setting up specialized construction facilities. Because the core wall foundation is designed as a sloping section with a maximum gradient of 50 degrees, conventional grouting equipment cannot be stably positioned and operated on such slopes. Therefore, a sliding drilling grouting construction trolley system was specially designed and manufactured. The main body of this system is a rectangular working platform welded from Q235 channel steel, with a top surface dimension of 3m × 3.2m. A 30mm thick wooden plank is laid on the top surface of the platform to form a working plane. A 1.2m high guardrail is welded around the platform and securely fastened with safety netting, forming a closed aerial work area. The bottom of the platform is machined to a corresponding slope according to the gradient of the foundation slope, ensuring that the working surface is level after the platform is in place. The movement and positioning of the platform rely on a JM-12T slow-speed winch fixed to the top platform of the core wall foundation, which is pulled by a 24mm diameter steel wire rope. The securing of the winch itself is crucial, and this is achieved by drilling holes in the concrete base structure, inserting 25mm diameter round steel anchor rods, and then injecting M30 cement mortar. Simultaneously, to protect the asphalt concrete core wall construction surface below from contamination, a water-retaining weir is installed at the lowest point of the slope at the copper water-stop groove. A thick plastic sheet is laid upstream of the weir to form a guide surface, collecting wastewater generated during drilling, flushing, and grouting into a collection tank positioned along the slope. From there, wastewater is pumped to a three-stage sedimentation tank for treatment.

[0080] Determining the grouting hole locations is fundamental to all subsequent work. Based on the approved construction drawings, construction personnel used total stations and other surveying instruments to precisely measure and mark the center positions of each curtain grouting hole and consolidation grouting hole on the already poured core wall foundation concrete surface, using bright paint. Subsequently, the construction area was divided into grouting units according to the design documents, and each hole was uniquely numbered according to established numbering rules, creating a detailed hole location file to guide construction and facilitate process recording and management.

[0081] Drilling is a crucial step in revealing geological conditions and creating grouting channels. Drilling equipment is selected based on the hole type and depth. For consolidation grouting holes, down-the-hole drills or rotary drilling rigs are typically used, requiring the drilling direction to be perpendicular to the concrete surface of the foundation. For curtain grouting holes, core drilling rigs are commonly used, equipped with diamond drill bits, and drilling proceeds in sections from top to bottom. During drilling, controlling the borehole inclination is extremely strict, as this is crucial to ensuring effective overlap of the deep curtain and avoiding the formation of seepage-proof blind zones. Therefore, multiple preventative and corrective measures are implemented. When starting the borehole, it is essential to ensure the drilling rig's vertical shaft is stable and oriented accurately. During drilling, short straight drill rods, long core tubes, or drill collars are preferred to increase bottom hole pressure stability. When encountering karst caves or weak strata, low drilling speed and light drill pressure parameters are used. Borehole inclination is measured every ten to fifteen meters, and the bottom hole deviation is calculated promptly, with particular emphasis on keeping the deviation within a minimum range for the upper twenty meters of the borehole. If deviation exceeds the limit, immediately activate the pre-planned correction measures such as guide plate correction or bottom pipe correction. After drilling to the designed depth, borehole flushing is required, using high-flow-rate pressurized water to flush out rock powder and debris from the borehole until the return water becomes clear.

[0082] Grouting is the most crucial technological step in this project, and its success or failure directly affects the quality of the seepage barrier. The curtain grouting employs a proven method of "orifice sealing, in-hole circulation, and top-down segmented grouting." After the first segment of grouting is completed, a robust orifice pipe is embedded at the orifice and allowed to solidify. Subsequent grouting is then carried out using sealing devices installed on the orifice pipe. The lower end of the grouting pipe is no more than 50cm from the bottom of the hole to ensure effective circulation of the grout at the bottom. Consolidation grouting uses a "top-down, in-hole circulation, segmented injection" method. The first segment utilizes a mechanical plugging device to seal and grout within the concrete above the bedrock surface. The grout is made of ordinary Portland cement with a strength grade of no less than 42.5, uniformly mixed at a centralized grouting station and transported to each work point via pipelines. The water-cement ratio of the grout is gradually adjusted from thin to thick, typically starting at 5:1 or 3:1 and gradually concentrated to a 0.5:1 thick grout depending on the injection rate. The grouting pressure is strictly implemented according to the design pressure gauge based on different hole sequences and depths, and is dynamically adjusted according to the injection rate during the grouting process, following the principle of "graded pressure increase".

[0083] The geological information obtained through dynamic exploration during construction is a valuable basis for guiding grouting operations. Through pilot holes and ongoing grouting boreholes, the specific type, size, spatial location, infill material properties, and presence of water flow of any encountered karst geological defects are determined in real time. The principle of classified treatment is applied to different types of defects, which is the core of this plan for dealing with strong karst geology. For unfilled karst caves, different measures are taken according to their size: when the drill drop depth is greater than 2m, it is considered a large-scale cave, and high-flow-rate C20 fine-aggregate concrete or cement mortar is pumped into the borehole for backfilling. After it has fully solidified, the borehole is swept clean for subsequent grouting. When the drill drop depth is less than or equal to 2m, well-graded sand is poured into the karst cave, or a "hydraulic flushing" method is used for backfilling. For fully filled karst caves, the treatment varies depending on the composition of the filling material: if the filling material is mainly clay, the grouting pressure is appropriately increased, and techniques such as "high-pressure flushing grouting" and "high-pressure displacement grouting" are used to flush away and replace some of the viscous filling material, improving groutability. If the filling material is mainly sand, "high-pressure jet grouting" is used, utilizing a high-speed grout flow to cut and mix the sand layer, forming a solidified mass. For karst caves where significant water flow is found, conventional cement grout is easily washed away; therefore, epoxy resin-based chemical grouts that can solidify under flowing water conditions are used for injection and sealing.

[0084] During grouting, it is common to encounter borehole sections with persistently high injection rates, making it difficult to meet the completion criteria. This situation often occurs in shear dissolution zones with intense karst development. To address this, a "karst-controlled grouting" procedure is initiated. This procedure comprehensively utilizes various control measures, including low pressure, concentrated grout, flow restriction, volume restriction, intermittent grouting, waiting for setting, and re-grouting. If necessary, more stable grouts, mixed grouts, or paste-like grouts can be injected, aiming to gradually fill the water passage rather than blindly pursuing high injection volumes. Regardless of the specific treatment measures employed, after the treatment is completed, the borehole must be re-scanned to remove any residue. The section must then be re-grouted strictly according to conventional grouting process requirements until the designed grouting completion criteria are met. This achieves a closed-loop process of "conventional grouting, special treatment, and conventional re-grouting," ensuring that each special section ultimately forms a qualified impermeable body.

[0085] Safety and quality control were prioritized throughout the construction process. Vertical uplift observation holes were installed at key locations along the grouting axis, and precision uplift monitoring devices were installed. Continuous monitoring was conducted whenever high-pressure flushing, water pressure testing, or grouting operations were performed within a 20-meter radius to ensure that the rock mass uplift deformation was strictly controlled within the design limits, preventing damage to the upper core wall foundation concrete structure due to excessive pressure. All grouting process parameters, such as pressure, flow rate, grout specific gravity, and grout change records, were recorded accurately and completely in a dedicated form by a recorder in real time.

[0086] Once all sections of a grouting hole have been constructed and approved by the supervising engineer, the sealing operation is carried out immediately. The sealing method adopts the "displacement and pressure grouting sealing method", injecting a 0.5:1 thick grout into the hole and applying a certain pressure through a grouting pump to seal the hole, ensuring that the grout inside the hole is dense. After the grout at the hole opening solidifies, it is grouted again to finally form a smooth and dense hole opening.

[0087] The effectiveness of grouting projects ultimately needs to be verified through rigorous quality inspection. Seven days after the completion of all consolidation grouting, inspection holes are installed at locations designated by the supervising engineer, representing no less than 5% of the total number of grouting holes. Diamond drill bits are used to extract core samples from these inspection holes to observe the filling and bonding of the cement grout within the cores, and water pressure tests are conducted in sections. The quality standard for consolidation grouting is that the permeability value measured by the water pressure test is no greater than 5 Lu. Inspection of curtain grouting is conducted 14 days after the completion of all hole construction, with inspection holes installed at 10% of the total number of holes in a single row. Core sampling and sectioned water pressure tests are also performed, but the design seepage prevention standard is higher, requiring a permeability value no greater than 3 Lu. The construction of inspection holes must also follow the entire process of drilling, flushing, water pressure testing, and sealing. Only when the water pressure test results of all inspection holes meet the design standards can the grouting project for that unit be rated as qualified.

[0088] From the erection of a dedicated construction platform to the precise layout and drilling of each borehole, to the categorized and refined grouting and special treatment based on real-time geological information, and finally to rigorous quality inspection, this implementation plan describes a complete grouting construction process applicable to strongly karst areas, targeting the bedrock beneath the anti-seepage wall. This process emphasizes the progressive logic of exploration, classification, and treatment, closely integrating dynamic geological surveys with engineering construction. Through a series of targeted technological combinations, it aims to transform complex and variable geological conditions into construction objects that can be handled according to standardized procedures, thereby constructing a continuous, stable, and long-term anti-seepage concealed project in strongly karst strata.

[0089] In the description of this invention, it should be understood that the terms "longitudinal", "lateral", "up", "down", "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, and are only for the convenience of describing this invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0090] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.

Claims

1. A construction method for rapid sealing and grouting of seepage under an anti-seepage wall in a strongly karst area, characterized in that, Includes the following steps: Determine the grouting hole locations; Construction exploration to obtain karst geological information of the construction area below the anti-seepage wall base where the grouting holes are located, wherein the karst geological information includes at least the type, scale and location of karst geological defects; Based on the karst geological information, corresponding preprocessing is performed on different types of karst geological defects; Anti-seepage grouting construction will be carried out in the pre-treated areas and normal areas; After the grouting work is completed, the grouting quality is verified.

2. The construction method for rapid sealing grouting under a seepage barrier in a strong karst area according to claim 1, characterized in that, The step of determining the grouting hole location includes: According to the construction design drawings, the center position of each grouting hole is marked on the concrete surface of the anti-seepage wall base. The order of grouting holes is dynamically adjusted according to design requirements and leakage conditions; Each grouting hole is uniquely numbered according to the design requirements.

3. The construction method for rapid sealing grouting under a seepage barrier in a strongly karst area according to claim 1, characterized in that, The steps for obtaining the karst geological information of the construction area below the anti-seepage wall foundation for the grouting hole locations include: During the drilling process at the grouting holes, pilot holes and grouting holes are used to conduct dynamic geological exploration during the construction period in order to quickly determine the leakage situation under the wall.

4. The construction method for rapid sealing grouting under a seepage barrier in a strongly karst area according to claim 1, characterized in that, The leakage under the wall includes leakage at the contact zone between the wall and the karst strata, and karst leakage in the bedrock under the wall; Among them, karst seepage in the bedrock under the wall includes seepage caused by one or more karst geological defects such as dissolution fissures, caves and karst conduits; Among them, karst caves include unfilled karst caves, semi-filled karst caves, and fully filled karst caves; Karst conduits include both conduits with and without water flow.

5. The construction method for rapid sealing grouting under a seepage barrier in a strong karst area according to claim 4, characterized in that: When the leakage under the wall is the leakage at the contact zone between the wall and the karst stratum, with the design approval, the construction sequence of the grouting holes is adjusted, that is, the downstream drain is constructed first, and the upstream drain is constructed first. Depending on the amount of leakage, one or more of the sealing methods such as sand-mixed grouting, double-liquid grouting and chemical grouting are used for rapid sealing treatment. When the type of karst geological defect in the bedrock is an unfilled cave, obtain the size of the unfilled cave; When the size of the unfilled karst cave is such that the depth of the drill bit falls is greater than a set threshold, high-flow fine stone concrete or cement mortar is pumped into the karst cave for backfilling, and the hole is swept after it has set. When the size of the unfilled karst cave is such that the depth of the drill bit drop is less than or equal to the set threshold, graded sand is injected into the karst cave or hydraulic flushing is used for backfilling.

6. The construction method for rapid sealing grouting under a seepage barrier in a strongly karst area according to claim 4, characterized in that, When the type of karst geological defect is a fully filled cave, the type of filling material of the fully filled cave is obtained; When the filling material of the fully filled karst cave is mainly clay, the grouting pressure should be increased, and high-pressure flushing grouting or high-pressure replacement grouting should be used for treatment. When the filling material of the fully filled karst cave is mainly sand, high-pressure jet grouting is used for treatment.

7. The construction method for rapid sealing grouting under a seepage barrier in a strongly karst area according to claim 4, characterized in that, When the type of karst geological defect is a water-flowing cave, an epoxy resin-based chemical grout that can solidify under flowing water conditions is injected into the water-flowing cave.

8. The construction method for rapid sealing grouting under a seepage barrier in a strongly karst area according to claim 1, characterized in that, The steps for performing anti-seepage grouting construction include: Curtain grouting was carried out using a method of orifice sealing, internal circulation, and top-down segmented grouting. During the grouting process, when encountering a grouting section with a large injection volume that is difficult to finish, karst control grouting is implemented. After completing the pretreatment for karst geological defects or the karst control grouting, the borehole is re-scanned and conventional grouting is performed on the borehole section until the designed grouting completion criteria are met.

9. The construction method for rapid sealing grouting under a seepage barrier in a strong karst area according to claim 1, characterized in that, The steps for verifying grouting quality include: After the anti-seepage grouting construction is completed and the specified curing period is reached, inspection holes are arranged in the construction area according to a preset ratio. The inspection hole was subjected to segmented drilling and water pressure testing; Based on the results of the water pressure test, determine whether the grouting quality of the construction area meets the design requirements.

10. The construction method for rapid sealing grouting under a seepage barrier in a strongly karst area according to claim 8, characterized in that, The methods of controlled grouting in karst include one or more of the following: low-pressure grouting, thick grouting, flow-limited grouting, volume-limited grouting, intermittent grouting, waiting for setting, re-grouting, grouting stable grout, grouting mixed grout, and grouting paste grout.

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