Construction process of anti-seepage wall for super-deep dam foundation covering layer

Abstract

This application relates to the field of dam foundation seepage prevention and reinforcement construction technology, and in particular to a construction process for an ultra-deep dam foundation overburden seepage barrier wall. The process includes using a rotary drilling rig to drill along the axis of the seepage barrier wall, sequentially lowering multiple spliced ​​casings in sections, clearing the soil inside the casings, pouring concrete to form in-situ concrete piles, and before the concrete has initially set, connecting the grouting equipment and air source to the cement grout nozzle and air nozzle respectively, adjusting the casings so that the cluster injection assembly faces the adjacent pre-set piles, lifting and removing the casings in sections, and using the cluster injection assembly to directionally inject grout to form the seepage barrier wall. This application achieves the technical effect of forming a tightly overlapping seepage barrier wall in the ultra-deep dam foundation overburden layer, effectively solving the seepage problem, and being able to cope with obstacles in the strata, ensuring construction quality and effectiveness.

Description

Technical Field

[0001] This application relates to the field of dam foundation seepage prevention and reinforcement construction technology, and in particular to a construction process for an ultra-deep dam foundation overburden seepage prevention wall. Background Technology

[0002] In the construction of anti-seepage walls for ultra-deep dam foundation overburden layers, there are traditionally a variety of construction methods. For example, the hydraulic milling machine method uses a high-power hydraulic motor to drive a roller equipped with milling teeth to cut and break the strata. The mixture of slag and mud is discharged by a mud pump to form a trench, and then plain concrete walls are poured into the protective mud. The grab method and the drilling and splitting method are combined. First, a heavy hydraulic grab bucket is used to excavate the upper overburden layer. When encountering large boulders or bedrock, an impact drill or rotary drill is used to drill the main hole, and then a grab bucket or hydraulic milling machine is used to split the secondary holes to form a complete trench section. The water jetting method for wall construction uses high-speed water flow to cut the strata to form trenches. A forming device is used to trim the trench walls and use mud to protect the walls.

[0003] However, these traditional construction methods have obvious drawbacks. For example, the hydraulic milling machine method is expensive, difficult to handle extra-large boulders and high-strength bedrock, and requires mud slurry for deep trench construction; the combination of grabbing and drilling methods involves many processes, low construction efficiency, complex coordination and management, and high difficulty in controlling the verticality of the trench and the quality of the joints, and also requires mud slurry for wall protection; the water jetting method has limited applicable depth, is difficult to handle deep dense strata and large-diameter boulders, and has limited precision control for ultra-deep anti-seepage walls. Summary of the Invention

[0004] To overcome the shortcomings of the existing technology, this application provides a construction process for an ultra-deep dam foundation cover layer anti-seepage wall. By solving the problems of high construction difficulty of existing ultra-deep anti-seepage trenches, the need for mud slurry wall protection, geological environment difficulties such as handling large cross-section boulders, and difficulty in ensuring the continuity of overlapping, this application utilizes a combination of full-casing full-rotation segmented hole forming and clustered controllable directional jetting wall construction to achieve continuous anti-seepage construction in ultra-deep and complex environments.

[0005] This application provides a construction process for an ultra-deep dam foundation overburden seepage barrier wall, including: S1. Using a rotary drilling rig, drilling is performed along the axis of the anti-seepage wall. During the drilling process, multiple coaxially connected spliced ​​sleeves are sequentially lowered in sections. The diameter of the outermost spliced ​​sleeve is larger than the diameter of the other spliced ​​sleeve inserted into it and extending deeper. The inner sides of the opposite sides of the spliced ​​sleeve are respectively provided with a first pipe and a second pipe. The bottom of the first pipe is provided with a cement slurry nozzle, and the bottom of the second pipe is provided with an air nozzle. The air nozzle and the cement slurry nozzle are arranged adjacent to each other to form a cluster spraying assembly. S2. During the process of sinking the spliced ​​casing to form a hole, the soil inside the spliced ​​casing is cleaned and removed at the same time until the hole is drilled to the preset depth. S3. Continuously pour concrete from bottom to top into the bottom of the inner cavity of the splicing sleeve to form an in-situ concrete pile at the current hole location. S4. When the concrete pouring is completed but before it has set, connect a grouting device to the cement slurry nozzle through the first pipe, connect an air compressor to the air nozzle through the second pipe, and adjust the splicing sleeve so that the cluster spraying assembly faces the direction of the adjacent preset pile body. S5. Lift the spliced ​​casing upwards in sections and remove it. During the lifting process, use the cluster spraying component to perform directional spraying, so that the cement grout is cut and mixed with the soil and pebbles in the stratum outside the spliced ​​casing under the action of compressed gas, so as to form a tightly overlapping anti-seepage wall between adjacent plain concrete piles.

[0006] In drilling operations in ultra-deep overburden formations, the contact area between the casing outer wall and the formation increases positively with depth. When the depth reaches a certain level, the accumulated sidewall frictional resistance exceeds the rated output power of the equipment. By employing the aforementioned coaxial nested casing structure, progressing from shallow to deep and from coarse to fine, the inner casing extending into the deeper layers only comes into direct contact with the soil after extending beyond the bottom of the larger casing above it during its descent. The upper main casing section descends within the internal cavity of the upper casing, dividing the continuous side frictional resistance across the entire depth into multiple localized independent frictional forces. This reduces the torque and downward pressure power required for drilling equipment in ultra-deep formations, preventing stuck drill bits due to excessive frictional resistance. Simultaneously, the layered nesting of multiple steel casings provides rigid guidance for the lower edge of the drill bit, resisting the lateral compressive forces caused by uneven soil density in deep and complex formations, and reducing borehole deviation errors. Meanwhile, the high-pressure jetting pipeline is directly integrated inside the casing, eliminating the need for a secondary insertion of flexible grouting pipes into such ultra-deep holes during conventional construction. This saves pore space and reduces the risk of pipeline entanglement and damage. Because full casing drilling is used, no mud slurry is required for wall protection during the borehole formation process, eliminating the need for waste mud disposal. While the casing is being pulled out from bottom to top, the jetting assembly integrated at the bottom of the casing performs air and slurry jetting, mixing with the in-situ soil and rock within the hole and the in-situ injected plain concrete. This achieves simultaneous connection between casing removal, filling of porous strata, and construction of the anti-seepage wall, ensuring the continuous quality of the anti-seepage wall even in deep boulders and gravel geological conditions.

[0007] Optionally, in step S5, when there are blocks in the stratum that obstruct the overlap of the anti-seepage spray, the swing angle of the splicing sleeve during directional spraying is increased to diffuse and increase the spray area of ​​the grout, so that the cement grout can wrap around the block and overlap with the adjacent wall.

[0008] By adopting the above-mentioned technical solution, it is possible to address the problem of large boulders and other geological obstacles buried in ultra-deep overburden dam foundations. These objects can easily become key nodes blocking the overlap of the seepage-proof grout with the water curtain. To solve this problem, the spray angle of the jet output from the clustering component at the end of the splicing sleeve can be increased in real time, causing the originally concentrated high-pressure cement grout to expand and spray out in a fan shape. The wider lateral diffusion area allows the jet stream to fully flow around and cover the periphery of the boulder, and fill the surrounding gaps. In this way, without the need for mechanical cutting or pulling out of the large geological obstacle, a closed loop can be achieved along its outline, thus crossing the geological barrier zone and forming a closed cement-soil bonded wall with the adjacent solid walls above, below, or to the sides. This effectively avoids the risk of leaving large, penetrating transverse seepage cracks and improves the safety of the entire length of the seepage-proof structure in complex and deep conditions.

[0009] Optionally, the spray angle range can be increased to 15° to 30°.

[0010] By adopting the above technical solution, the adjustable swaying angle used to change the jet coverage when encountering geological obstacles is expanded to a control range of 15° to 30°. This angle range ensures that the jet coverage surface after radial expansion has sufficient geometric width to bypass the boundaries of common large pebbles and boulders and re-converge, while effectively preventing excessive swaying angles from causing a drastic attenuation of kinetic energy and cutting compressive stress in the high-pressure concentrated jet due to excessive extension. This maintains strong cutting ability, capable of breaking up dense soil blocks and achieving mixed replacement, while ensuring that the wrapping radius of the cement grout filling and bonding achieves maximum utilization efficiency, thus ensuring that the wrapping joint wall in deep, weak areas still possesses good waterproof sealing performance and shear strength.

[0011] Optionally, in step S1, multiple coaxially connected spliced ​​casings are nested and drilled in three sections, including a first spliced ​​casing, a second spliced ​​casing, and a third spliced ​​casing arranged from top to bottom. The diameter of the first spliced ​​casing is 2.0m and its corresponding pipe body is located at a depth of 0 to 70m. The diameter of the second spliced ​​casing is 1.8m and its corresponding pipe body is located at a depth of 70 to 140m. The diameter of the third spliced ​​casing is 1.6m and its corresponding pipe body is located at a depth of 140 to 200m.

[0012] By adopting the above technical solution, the first spliced ​​casing with the largest diameter provides wall support in the shallow surface layer from 0 to 70m. When the second spliced ​​casing is nested inside the first spliced ​​casing and continues drilling, its first 70m of casing is inside the first spliced ​​casing, with no formation adhesion, and friction only occurs between the 70 and 140m section and the formation along the route. Similarly, when the third spliced ​​casing drills to an extremely deep layer of 200m, the first 140m of casing is isolated and protected by the external casing. Based on engineering mechanics, this three-stage diameter reduction structure disperses the total frictional resistance of the original 200m long single-hole casing wall into three single-hole section frictional resistances, each no longer than 70m. After this subtractive decomposition, the full-rotation main equipment only needs to overcome the sidewall resistance of a single section to complete the operation, enabling conventional rated power drilling equipment to explore to a depth of 200m in the overburden layer, reducing reliance on ultra-heavy customized construction equipment and equipment upgrade costs.

[0013] Optionally, in step S5, the innermost splicing sleeve at the deepest point is first pulled upward by surface equipment, while the cluster spraying component at the bottom of the sleeve is used for swing spraying. After the bottom of the innermost splicing sleeve is raised to the position of the bottom of the splicing sleeve of the adjacent upper layer, the swing spraying is stopped, and the innermost splicing sleeve is completely pulled out. Then, the splicing sleeves are lifted one by one from bottom to top along the hole depth direction until the topmost pipe section is taken out of the hole.

[0014] By adopting the above technical solution, when pulling steel pipes from working surfaces with extremely deep holes (e.g., up to 200m), if a whole-body pulling method is used, the instantaneous pulling force required will be many times greater than the drilling pressure, which can easily cause breakage at the casing connection or tensile yielding of the pipe body. This application relies on the previously mentioned coaxial nested spliced ​​casing structure to prioritize the pulling of the spliced ​​casing located at the bottom and wrapped by the outer pipe; at this time, the other spliced ​​casings in the upper section remain in the hole to play the role of retaining soil and protecting the wall. The spliced ​​casing located at the bottom only needs to overcome the soil friction in its own 60 to 70m exposed section to smoothly slide into the other spliced ​​casings above it and be pulled out of the ground; subsequently, each layer of casing is pulled out and lowered step by step from the inside out. The relay pulling process distributes the peak pulling load of the whole hole pile to each independent section, reduces the tensile load requirements of the lifting equipment, prevents engineering accidents caused by pipe jamming and breakage during deep hole pulling, and ensures efficient and continuous grouting operations from the bottom of the hole to the hole opening.

[0015] Optionally, the wall thickness of the splicing sleeve is not less than 60mm, and both the first and second pipes are located inside the wall of the splicing sleeve.

[0016] By adopting the above technical solution, the thickness of the casing wall on one side of the ultra-deep excavation equipment is no less than 60 mm to meet the preset strength requirements, thus constructing a robust casing wall. The critical first and second high-pressure long pipes (used to transport kinetic fluid) are completely embedded inside this wall, allowing its exterior to withstand the pressure of high-pressure rock formations during ultra-deep diving, as well as the cutting of hard ground materials and the impact of falling drill bits, maintaining its shape and preventing collapse. Simultaneously, this embedded, closed-loop pipe arrangement avoids entanglement and damage during hoisting and rotation, and also prevents the pipe system from being crushed by sediment and mud during the pouring of tens of cubic meters of concrete after the central hole, thus ensuring a continuous supply of slurry during underwater wall construction and providing a deep-diving foundation structure for the full-rotation drilling tool under extreme service conditions.

[0017] Optionally, in step S3, when the in-situ concrete pile body is poured in stages, before the next stage of splicing sleeve is poured after the previous stage of splicing sleeve is completed and before the next stage of splicing sleeve is to be continued, the splicing sleeve is pre-drilled downwards by no less than 50cm so that the bottom end of the splicing sleeve cuts into the interior of the poured but not yet initially set concrete, and then the subsequent splicing is carried out.

[0018] By employing the aforementioned technical solution, during the backfilling of large-aggregate plain concrete at this pile location in different layers and at different times, the operating equipment impacts downwards and penetrates deeply into the bottom layer of concrete that has already formed but is still in the fluid and solidification buffer period, with an insertion depth of at least 50 centimeters. This operation fully utilizes the settlement impact and crushing force of the pipe wall edge to peel off and agitate the thin film-like water-slag separation layer accumulated at the top and bottom of the interface between the two layers, thereby effectively promoting the forced slurry stirring of the newly poured concrete and its coarse and fine aggregates, wedging them deep into the upper layer of concrete, forming an overlapping and mutually integrated bonding band. As a result, the old material and new slurry backfilled in different batches are bidirectionally embedded and interlocked under the action of hydrothermal physical compression, ultimately becoming a huge monolithic pile segment. This eliminates the shear weakness layer and interlayer lateral seepage hazards that often occur at the boundary of large-volume concrete pouring, forming a seepage-proof performance from the pile bottom to the pile top.

[0019] Optionally, both the first and second pipes are provided with multiple sets, and one set is provided in the pipe wall on each of the opposite sides of the splicing sleeve; an air nozzle and at least two cement slurry nozzles are provided inside any single side of the pipe wall, and the cement slurry nozzles are respectively provided above and below the air nozzle on the axis, so that the air nozzle is placed between the two sets of cement slurry nozzles to form a single-sided single-sided cluster spraying assembly.

[0020] By adopting the above technical solution, the arrayed grouting input pipes are arranged in a double-sided impact distribution. On each side, a centrally located horizontally positioned high-pressure air nozzle is used, along with two clusters of cement grout nozzles at its lower and upper ends, forming a sandwich-structured jet nozzle. The leading air bubble layer and low-resistance channel generated by the airflow released through the central air nozzle effectively protect the high-density cement grout column injected simultaneously through both upper and lower nozzles and holes, preventing energy loss and attenuation caused by overlapping and mixing media. Relying on this structure, the cement grout group is injected under the guidance of the air blade, significantly increasing the lateral penetration depth. This enhances the strong reshaping and replacement capacity for disintegrating deep gravel and boulders and filling cavities, increases the width across the partition layer, and forms a wide, deep, seepage-proof, anti-clogging, and dense cementitious body, improving its thickness and quality.

[0021] Optionally, the total number of cement slurry nozzles inside the two side walls of the splicing sleeve is 8, and the total number of air nozzles is 2, forming a fluid jet structure.

[0022] By adopting the above technical solution, a total of 8 high-flow-rate cement slurry injection holes and 2 main tunnel vents are arranged on both sides, forming a multi-nozzle jet structure. This parameter configuration significantly increases the number of injection points that penetrate the strata laterally and longitudinally, as well as the densely interwoven and overlapping impact trajectories, during each rotation and ascent of the same distance. This interconnects the injection sections, reducing blind spots and avoiding defects such as water and sand leakage. Multiple jet filling increases the mixing ratio and infiltration volume of the high-density hardened cement slurry surrounding the soil. With high injection pressure, the equipment can continuously drill to depths of hundreds of meters per day at high efficiency, while simultaneously constructing a 100-meter-level impermeable wall, forming a 100-meter-level impermeable water curtain wall with standard impermeability.

[0023] Optionally, in step S5, when performing directional cluster spraying, the cement slurry pressure is 30 to 40 MPa and the compressed gas pressure is 2.0 MPa; when the splicing sleeve with the cluster spraying component is pulled upward, the swing spraying lifting speed of the splicing sleeve is 30 to 50 cm / min.

[0024] By employing the aforementioned technical solution, relying on the high-pressure injection of cement grout, a pressure differential kinetic energy of 30 to 40 MPa is maintained, while simultaneously ensuring a constant output pressure of 2.0 MPa for compressed air. Furthermore, the lifting speed of the splicing sleeve is strictly controlled within a stable range of 30 to 50 centimeters per minute. Utilizing powerful jet cutting energy, the grout is unaffected by the backflow of high-pressure water in deep-water, heavy-rock environments, effectively breaking up rock fragments and replacing mudstone layers along the path. Simultaneously, the slow and stable lifting speed provides the grout with an optimal time window, allowing it to fully penetrate, tumble, and mix, completing physical consolidation and chemical hydration reactions, encapsulating every inch of sand and gravel. This precise combination of high-pressure, strong impact and slow lifting creates an ultra-durable, dense, high-strength soil-stabilized structure in the deepest part of the dam foundation, achieving a tight connection and forming a dam foundation with good seepage resistance.

[0025] In summary, the construction technology for the ultra-deep dam foundation overburden seepage barrier wall provided in this application, by adopting a full-casing drilling and grouting pipeline arrangement, eliminates the need for the construction of traditional mud wall protection systems and the waste slurry treatment and discharge process, thus improving the environmental compliance rate of the work site. Furthermore, the multi-stage spliced ​​casing with successively decreasing diameters and concentric nesting is used in the casing system for segmented drilling and segmented extraction operations. The smooth cavity inside the outer casing isolates the stratum envelope surface of adjacent lower-level inner casings. During the two-way cycle of drilling and casing extraction, the increase in resistance caused by side friction of the borehole wall is distributed and reduced, lowering the operating load of the main unit. Simultaneously, the rigidly nested multi-layer casing wall improves the lateral stiffness of the deep-hole drilling tools, ensuring the vertical accuracy of the wall, and the synchronous layer-by-layer lifting and jet grouting wall construction process achieves continuous curtain seepage prevention under complex geological conditions of ultra-deep overburden layers. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the overall structure of an embodiment of this application; Figure 2 yes Figure 1 A magnified view of part A in the diagram; Figure 3 This is a partial structural diagram of this application; Figure 4 yes Figure 1 A magnified view of part B in the diagram; Figure 5 yes Figure 1 Partial structural diagram; Figure 6 yes Figure 1 A partial structural diagram.

[0027] In the diagram: 1. Drilling equipment; 2. Cutoff wall; 3. Splicing sleeve; 31. First pipeline; 311. Cement slurry nozzle; 32. Second pipeline; 33. First splicing sleeve; 34. Second splicing sleeve; 35. Third splicing sleeve; 4. In-situ concrete pile; 5. Cutoff wall. Detailed Implementation

[0028] The following will be combined with the appendix Figure 1-6 The technical solutions of the various embodiments of this application have been clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0029] Reference Figures 1 to 3 This application discloses a construction process for an ultra-deep dam foundation overburden seepage barrier wall, including step S1: using a rotary drilling device 1 to drill along the axis of the seepage barrier wall 2, and during the drilling process, multiple coaxially connected spliced ​​sleeves 3 are sequentially lowered in sections. The diameter of one spliced ​​sleeve 3 located on the outer layer is larger than the diameter of another spliced ​​sleeve 3 inserted into it and extending deeper. The inner sides of the opposite sides of the spliced ​​sleeve 3 are respectively provided with a first pipe 31 and a second pipe 32. The bottom of the first pipe 31 is provided with a cement slurry nozzle 311, and the bottom of the second pipe 32 is provided with an air nozzle. The air nozzle and the cement slurry nozzle 311 are arranged adjacent to each other to form a cluster spraying assembly.

[0030] Specifically, the splicing sleeve 3 is a hollow, vertically continuous cylindrical structure. The rotary drilling device 1 is located at the top of the splicing sleeve 3 and fixedly connected to its upper end. The power output end of the rotary drilling device 1 is rigidly connected to the top of the splicing sleeve 3 via a flange and bolt assembly, thereby driving the splicing sleeve 3 to rotate and drill downwards along the axis of the anti-seepage wall 2. Both the first pipe 31 and the second pipe 32 extend parallel to the axial direction of the main body of the splicing sleeve 3, and the inner walls of both pipes have smooth circular cross-sections. The cement slurry nozzle 311 and the air nozzle are both embedded and fixed at the bottom inner side of the splicing sleeve 3. The outlet end face of the cement slurry nozzle 311 and the outlet end face of the air nozzle are arranged adjacent to each other, with a center-to-center distance of 2 to 5 centimeters. In terms of spatial arrangement, they together form a clustered spray assembly, the jet opening direction of which is perpendicular to the outer surface of the splicing sleeve 3.

[0031] By employing a spliced ​​casing 3 with a clustered jet assembly for casing drilling and internal soil sampling, the traditional mud wall protection process is eliminated, avoiding the risks of deep borehole collapse and mud contamination. Simultaneously, the variable-diameter spliced ​​casing 3 can mitigate the drilling resistance load limitations imposed by ultra-deep formations on large equipment and the potential for borehole verticality bias.

[0032] The machinery responsible for cleaning the soil inside the borehole can also be replaced by a gravity grab bucket. The grab bucket uses a traction cable to work in conjunction with a tall external crane to lift and lower the bucket vertically. It relies on the weight of its own body to strike the soil vertically downwards, breaking up the solidified soil at the bottom of the pit. Then, the mechanical claws and connecting rods on the bucket gather and grab the debris, which is then lifted to the outside of the wellhead for pure physical dumping.

[0033] Preferred, refer to Figure 1 and Figure 4 In step S1, the spliced ​​casing 3 is drilled in three sections with varying diameters. The spliced ​​casing 3 includes a first spliced ​​casing 33, a second spliced ​​casing 34, and a third spliced ​​casing 35 arranged sequentially from top to bottom. The diameter of the first spliced ​​casing 33 is 2.0 meters and the depth of its corresponding pipe body is from 0 to 70 meters. The diameter of the second spliced ​​casing 34 is 1.8 meters and the depth of its corresponding pipe body is from 70 meters to 140 meters. The diameter of the third spliced ​​casing 35 is 1.6 meters and the depth of its corresponding pipe body is from 140 meters to 200 meters.

[0034] The first splicing sleeve 33, the second splicing sleeve 34, and the third splicing sleeve 35 are arranged in a coaxial, relative, sliding nested configuration. During the downward drilling and upward pulling process, the inner second splicing sleeve 34 can smoothly rise and fall axially within the cavity of the first splicing sleeve 33, and the inner third splicing sleeve 35 can smoothly rise and fall axially within the cavity of the second splicing sleeve 34. The top ends of each of the multiple splicing sleeves 3 are independently controlled by the surface drilling equipment 1 or the hydraulic pipe pulling tool. With this coaxial sliding nested structure, the subsequent pipe section located in the inner layer can directly pass through the outer, fixed pilot pipe section and extend out at the bottom, thereby constructing a stepped, reduced-diameter borehole.

[0035] Step S2 is as follows: During the process of sinking the spliced ​​sleeve 3 to form a hole, the soil inside the spliced ​​sleeve 3 is cleaned and removed until the hole is drilled to the preset depth.

[0036] Specifically, refer to Figure 1 and Figure 2 A rotary drilling rig is inserted into the spliced ​​casing 3 for construction. The rotary drilling rig is located in the central space of the spliced ​​casing 3, and its end is equipped with a valve barrel-type drill bit. The valve barrel-type drill bit forms a mechanical cutting engagement with the deep soil at the bottom of the hole, continuously collecting slag and removing it from the hole to clear solid obstacles in the cavity of the spliced ​​casing 3.

[0037] Step S3 is to continuously pour concrete from bottom to top into the bottom of the inner cavity of the splicing sleeve 3 to form an in-situ concrete pile 4 at the current hole location.

[0038] Specifically, refer to Figure 1 , Figure 5 and Figure 6 The concrete pouring adopts the tremie method, with the lower end of the tremie pipe inserted into the bottom of the inner cavity of the splicing sleeve 3. Concrete is continuously discharged from the lower outlet of the tremie pipe, gradually accumulating from bottom to top and filling the inner cavity of the splicing sleeve 3. The in-situ concrete pile body 4 refers to an underground solid pile foundation formed by directly pouring special unreinforced concrete without steel reinforcement in the original location after drilling a hole in the ground. The in-situ concrete pile body 4 is formed by curing ultra-retarded concrete material with self-compacting properties, which is poured in situ in the central deep pit of the splicing sleeve 3. This concrete material contains composite anti-dispersing agents, high-efficiency water-reducing agents, bentonite-based stabilizers, and expansion agents.

[0039] In step S3, when the in-situ concrete pile body 4 inside the splicing sleeve 3 is poured in stages, before the next stage of splicing sleeve 3 is poured after the previous stage of splicing sleeve 3 is completed and before the next stage of splicing sleeve 3 is to be poured, the splicing sleeve 3 is pre-drilled downwards by no less than 50 centimeters so that the bottom end of the splicing sleeve 3 is cut into the interior of the poured and yet-to-set concrete, and then the subsequent splicing is carried out.

[0040] Reference Figure 2 The bottom of the splicing sleeve 3 features a sharp-edged circular structure. During construction, reverse driving causes this ring to plunge downwards forcefully, creating a cutting stroke exceeding 50 centimeters. This forces the steel blade on the outer edge of the ring to penetrate vertically into the core area of ​​the newly poured in-situ concrete pile, which is still not fully solidified. During this deep penetration, a violent lateral pushing occurs between the smooth and hard steel backing shell of the splicing sleeve 3 and the freshly poured wet concrete mixture containing flowing coarse sand, accompanied by frictional re-rolling, compression, and interlocking.

[0041] Step S4 is as follows: when the concrete pouring is completed but before it has initially set, a grouting device is connected to the cement grout nozzle 311 through the first pipe 31, an air compressor is connected to the air nozzle through the second pipe 32, and the splicing sleeve 3 is adjusted so that the cluster spraying assembly faces the direction of the adjacent preset pile body.

[0042] Specifically, refer to Figure 1 and Figure 2 The output end of the grouting equipment is connected to the upper inlet of the first pipe 31 via a high-pressure hose, and the output end of the air compressor is connected to the upper inlet of the second pipe 32 via a high-pressure air pipe. The adjustment of the splicing sleeve 3 is achieved by the rotation mechanism of the rotary drilling equipment 1. The rotary drilling equipment 1 drives the splicing sleeve 3 to rotate around its axis by a preset angle until the jet outlet direction of the cluster spraying assembly is aligned with the center line connecting the adjacent preset piles.

[0043] The total number of cement slurry nozzles 311 inside the two side walls of the splicing sleeve 3 is eight, and the total number of air nozzles is two, forming a fluid jet structure.

[0044] Two independent cluster spraying zones are embedded inside the splicing sleeves 3 on the left and right sides, respectively. Each zone contains four neatly arranged cement slurry nozzles 311, two at a higher position and two at a lower position, used to spray high-pressure cement slurry to break up sandstone. A separate air nozzle is installed precisely at the center of the zone along its centerline. When all nozzles operate in parallel at full load, the crisscrossing high-pressure jets converge to form a dense, highly compacted, interlocking fluid planar structure with powerful compressive destructive force.

[0045] The first pipe 31 and the second pipe 32 are each provided with multiple sets, and one set is provided in each of the opposite sides of the pipe wall of the splicing sleeve 3; an air nozzle and at least two cement slurry nozzles 311 are provided inside any one side of the pipe wall. The cement slurry nozzles 311 are respectively provided above and below the air nozzle on the axis, so that the air nozzle is placed between the two sets of cement slurry nozzles 311, which together form a single-sided single-sided cluster spraying assembly.

[0046] Inside one side of the splicing sleeve 3, a first set of cement slurry nozzles 311, an air nozzle, and a second set of cement slurry nozzles 311 are arranged sequentially along the axial direction of the sleeve wall. The first set of cement slurry nozzles 311 is located above the air nozzle, and the second set of cement slurry nozzles 311 is located below the air nozzle. The axis of the air nozzle is parallel to the axis of the two sets of cement slurry nozzles 311 and lies in the same vertical plane. Inside the opposite side of the splicing sleeve 3, another set of single-sided cluster spraying components is arranged in the same manner, with the cluster spraying components on both sides distributed symmetrically in opposite directions.

[0047] The leading bubble layer and low-resistance channel generated by the airflow released through the middle air nozzle can effectively protect the high-density cement slurry column injected simultaneously from the upper and lower nozzles, allowing it to avoid energy loss and attenuation caused by overlapping and mixed media. The cement slurry group is injected under the guidance of the air blade, and the lateral penetration depth is greatly improved.

[0048] The wall thickness of the splicing sleeve 3 is not less than 60 mm, and the first pipe 31 and the second pipe 32 are both located inside the wall of the splicing sleeve 3.

[0049] The splicing sleeve 3 exhibits the structural characteristics of a thick-walled base plate, with a wall thickness of 60 to 80 millimeters. The first pipe 31 and the second pipe 32, which serve as channels for transmitting slurry and pressure energy, both have hollow, unfilled, and smooth circular cross-sections in their longitudinal cavities. These pipes are completely buried deep inside the pipe wall, isolated from the external environment, thus preventing the pipelines from being exposed and damaged under the cutting, abrasion, and impact of the high-hardness soil layer.

[0050] Optionally, the grouting volume can be adjusted according to different geological formations: when the geological type is sand, gravel, or pebble, the amount of cement grout used is 554 to 750 kg / m; when the geological type is pebble block, the amount of cement grout used is 700 to 900 kg / m.

[0051] Step S5 is as follows: lift the splicing sleeve 3 upward in sections and take it out. During the lifting process, use the cluster spraying component to perform directional spraying, so that the cement grout is cut and mixed with the soil and pebbles in the stratum outside the splicing sleeve 3 under the action of compressed gas, so as to form a tightly overlapping anti-seepage wall 5 between adjacent plain concrete piles.

[0052] Specifically, refer to Figure 2 and Figure 3 In step S5, the surface equipment first pulls and lifts the innermost splicing sleeve 3 at the deepest point, while the cluster spraying assembly at the bottom of the sleeve performs a swing spraying operation. After the bottom of the innermost splicing sleeve 3 is lifted to the position of the bottom of the adjacent upper-level splicing sleeve 3, the swing spraying stops, and the innermost splicing sleeve 3 is completely pulled out. Then, the splicing sleeves 3 are lifted one by one from bottom to top along the hole depth direction until the topmost pipe section is taken out of the hole.

[0053] Specifically, first, the third splicing sleeve 35, which is the deepest and has the thinnest inner diameter, is pulled upwards. It is then pulled upwards by surface equipment while simultaneously using the high-pressure jetting component at the bottom of the third splicing sleeve 35 to perform swing spraying. Once the bottom of the third splicing sleeve 35 is raised to the position of the bottom of the second splicing sleeve 34, the swing spraying stops and it is completely pulled out. Then, the second splicing sleeve 34 is raised using surface equipment while simultaneously swing spraying. Once it is raised to the position of the bottom of the first splicing sleeve 33, it is pulled out. Then, the first splicing sleeve 33 is raised using surface equipment while simultaneously swing spraying until it is pulled out.

[0054] When lifting the splicing sleeve 3 upwards, a segmented lifting method is adopted, with each lifting height being 1 to 2 meters. During the lifting process, the cement slurry nozzle 311 continuously sprays cement slurry at a pressure of 30 to 40 MPa, and the air nozzle continuously sprays compressed air at a pressure of 2.0 MPa. The cement slurry forms a high-speed jet under the entrainment of the compressed air. The jet impacts and cuts the soil and pebbles in the strata outside the splicing sleeve 3, while mixing the cement slurry with the cut soil and rock debris to form a cement-soil cementitious band. After the cementitious band solidifies, it constitutes the seepage-proof wall 5.

[0055] The air supply and grouting pipes are directly embedded in the drill splicing casing 3. After the concrete is poured in situ, the splicing casing 3 is continuously lifted before the concrete has initially set and directional air grout is immediately sprayed. This realizes the synchronous construction of in-situ casing wall molding, continuous grouting and deep spraying, and constructs the seepage prevention structure between the main pile and the continuous wall between the piles.

[0056] In step S5, when performing directional cluster spraying, the cement slurry pressure is 30 to 40 MPa and the compressed gas pressure is 2.0 MPa; when the splicing sleeve 3 with the cluster spraying assembly is pulled upward, the swing spraying lifting speed of the splicing sleeve 3 is 30 to 50 cm / min.

[0057] At the ground baseline, the cement grout pressure is consistently maintained at an ultra-high pressure of 30 to 40 MPa, and the compressed gas pressure also operates at full load pressure of 2.0 MPa. The jacking frame's clamping groove restrains the main lifting ring to limit the upward speed of the pipe wall, allowing it to move only 30 to 50 centimeters at a time.

[0058] Preferably, in step S5, when there are blocks in the stratum that obstruct the overlap of the anti-seepage spray, the swing angle of the splicing sleeve 3 during directional spraying is increased to diffuse and increase the spray area of ​​the grout, so that the cement grout can wrap around the block and overlap with the adjacent wall.

[0059] Specifically, the "block" refers to a lone rock or boulder that lies across the seepage prevention design path and whose cross-sectional dimension is greater than the radial cutting depth of the jet. When the splicing sleeve 3 moves upward in the vertical pull-out channel and approaches the side edge of the block, the cluster jet assembly works in coordination with the internal pipeline to switch and release the rotation section limit control of the outlet flow channel, causing the jet that was originally concentrated at one point to expand into an arc-shaped fluid curtain structure. This arc-shaped fluid curtain is forced to cross the outer edges of both ends of the large boulder, spreads and bends along its leeward side, reconverges in the leeward area, and wedges into the pre-set wall section connection junction located on the other side of the block.

[0060] For sections with special obstruction conditions such as extra-large boulders, specific areas are marked and tracked in the coordinate recording array. After completion, high-precision drilling rigs are used to extract tensile core samples in the local anomaly areas of the seepage prevention wall 5, and deep well pressure testing equipment is connected to perform pressure leak detection, forming a complete detection assembly system.

[0061] Preferably, the range of the sway spray angle is increased to 15 to 30 degrees.

[0062] By increasing the limiting threshold through the torsional angle parameter applied at the output end of the rotary component, the high-pressure multiphase slurry that is compressed and released from the cavity unfolds along the arc tangent. The outermost circumference of the unfolded slurry covers the width of the central block's cross-sectional area and successfully docks with the side impermeable wall section 2.

[0063] The implementation principle of this embodiment is as follows: A robust steel spliced ​​casing 3 serves as a rigid solid retaining wall. The rotary drilling rig 1 drives the spliced ​​casing 3 downwards, while a grab bucket or rotary drilling rig simultaneously removes soil from inside the casing 3. This principle completely avoids the problems of mud wall protection leading to hole collapse and environmental pollution at deeper depths. After drilling to the predetermined depth, before pulling out the spliced ​​casing 3, plain concrete is poured from bottom to top using the internal cavity of the casing 3 as a mold, forming a load-bearing and seepage-proof main pile. Before the internal concrete has solidified, the spliced ​​casing 3 is pulled out upwards. Simultaneously, a jetting component deeply embedded in the wall of the spliced ​​casing 3 sprays ultra-high pressure cement slurry and compressed air to both sides (i.e., the direction of adjacent piles), cutting and mixing the external soil to form a seepage-proof wall 5 that bonds two adjacent main piles together. A three-section structure (top 2.0m, middle 1.8m, bottom 1.6m diameter) is adopted. In ultra-deep strata up to 200 meters deep, if a pipe of uniform diameter were used, the lateral friction of the strata would cause it to seize up. By using a variable diameter, staggered design, upward friction is released (creating a suspended buffer section), eliminating the overload resistance of heavy-duty, fully rotating equipment. This allows the main unit, which originally required enormous power, to drill to a depth of 200 meters with only 1 / 3 of the energy consumption, and the variable diameter structure effectively prevents deviation in deep boreholes. Heavy-duty steel pipes over 60mm thick are used, and the high-pressure air pipe and grouting pipe are completely enclosed within the pipe wall. The underground rock at ultra-deep depths is violently turbulent and compressed, and the internal impact is immense when hundreds or thousands of cubic meters of concrete are poured. The internal armor of the pipeline isolates it from bidirectional mechanical friction and rock impact, ensuring continuous flow of air and grout in extreme underwater environments. One air nozzle in the middle and two grout nozzles on the top and bottom are installed on both sides of the pipe wall. A clever air-blade sandwich principle is employed. Due to the extreme water and soil pressure deep underground, the pure cement grout jet will rapidly attenuate; while the high-pressure (2.0MPa) air jet will first displace the mud and water, forming a leading low-resistance air bubble channel. Subsequently, the ultra-high pressure (30-40MPa) cement grout is injected along the channel opened by the airflow, expanding the lateral cutting depth and rock-breaking ability, ensuring a deep overlap between the old and new walls. When encountering extra-large boulders that cannot be cut by the high-pressure jet, the jet angle is increased to 15° to 30°. The jetted grout changes from a straight line to a large fan shape. The broad fan-shaped jet directly bypasses the outline of the huge boulder and re-converges from the back of the boulder. It wraps around it and binds it in the gaps, thus crossing the geological barrier zone and achieving a comprehensive waterproof seal. The relay-pull method of pulling out the bottom layer and cutting off and unloading the top layer not only reduces the crane load, but also ensures that the grouting of each section is completed before initial setting, avoiding the formation of cold joints that leak water. During the staged concrete pouring, the equipment is inserted downwards at least 50cm. The principle is to use the blade at the nozzle to forcibly pierce and stir the thin film and laitance on top of the upper layer of concrete, allowing the new material and the old material to wedge into each other and overlap, thus eliminating horizontal seepage and horizontal cracks that may occur during staged pouring.

[0064] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the technical solutions of the embodiments of this application.

Claims

1. A construction process of a cutoff wall for an ultra-deep dam foundation cover layer, characterized in that, include: S1. Using a rotary drilling device (1), drilling is performed along the axis of the seepage-proof wall (2) to form a hole. During the hole-forming process, multiple coaxially connected spliced ​​sleeves (3) are sequentially lowered in sections. The diameter of one of the spliced ​​sleeves (3) located on the outer layer is larger than the diameter of another spliced ​​sleeve (3) inserted into it and extending deeper. The inner sides of the opposite sides of the spliced ​​sleeve (3) are respectively provided with a first pipe (31) and a second pipe (32). The bottom of the first pipe (31) is provided with a cement slurry nozzle (311), and the bottom of the second pipe (32) is provided with an air nozzle. The air nozzle and the cement slurry nozzle (311) are arranged adjacent to each other to form a cluster spraying assembly. S2. During the process of the splicing sleeve (3) sinking to form a hole, the soil inside the splicing sleeve (3) is cleaned and removed until the hole is drilled to the preset depth. S3. Continuously pour concrete from bottom to top into the bottom of the inner cavity of the splicing sleeve (3) to form an in-situ concrete pile (4) at the current hole location. S4. When the concrete pouring is completed and has not yet set, a grouting device is connected to the cement slurry nozzle (311) through the first pipe (31), an air compressor is connected to the air nozzle through the second pipe (32), and the splicing sleeve (3) is adjusted so that the cluster spraying assembly faces the adjacent preset pile body. S5. Lift the splicing sleeve (3) upwards in sections and remove it. During the lifting process, use the cluster spraying assembly to perform directional spraying, so that the cement slurry can be cut and mixed with the soil and pebbles in the stratum outside the splicing sleeve (3) under the action of compressed gas, so as to form a tightly overlapping anti-seepage wall (5) between the adjacent plain concrete piles.

2. The construction technology for an ultra-deep dam foundation overburden seepage barrier wall according to claim 1, characterized in that, In step S5, when there are blocks in the stratum that obstruct the overlap of the anti-seepage spray, the swing angle of the splicing sleeve (3) during directional spraying is increased to diffuse and increase the spray area of ​​the grout, so that the cement grout can wrap the block and overlap with the adjacent wall.

3. The construction technology for an ultra-deep dam foundation overburden seepage barrier wall according to claim 2, characterized in that, The range of the sway spray angle is increased to 15° to 30°.

4. The construction technology for an ultra-deep dam foundation overburden seepage barrier wall according to claim 1, characterized in that, In step S1, the multiple coaxially connected splicing sleeves (3) are nested and drilled in three sections, including a first splicing sleeve (33), a second splicing sleeve (34), and a third splicing sleeve (35) arranged from top to bottom. The first splicing sleeve (33) has a diameter of 2.0m and its corresponding pipe body is located at a depth of 0 to 70m. The second splicing sleeve (34) has a diameter of 1.8m and its corresponding pipe body is located at a depth of 70 to 140m. The third splicing sleeve (35) has a diameter of 1.6m and its corresponding pipe body is located at a depth of 140 to 200m.

5. The construction technology for an ultra-deep dam foundation overburden seepage barrier wall according to claim 1, characterized in that, In step S5, the surface equipment first pulls and lifts the splicing sleeve (3) at the deepest and innermost point, while the cluster spraying component at the bottom of the sleeve is used to perform swing spraying. After the bottom of the innermost splicing sleeve (3) is lifted to the bottom of the adjacent upper layer splicing sleeve (3), the swing spraying stops and the innermost splicing sleeve (3) is completely pulled out. Then, the splicing sleeve (3) is lifted one by one from bottom to top along the hole depth direction until the topmost pipe section is taken out of the hole.

6. The construction technology for an ultra-deep dam foundation overburden seepage barrier wall according to claim 1, characterized in that, The wall thickness of the splicing sleeve (3) is not less than 60mm, and the first pipe (31) and the second pipe (32) are both located inside the wall of the splicing sleeve (3).

7. The construction technology for an ultra-deep dam foundation overburden seepage barrier wall according to claim 1, characterized in that, In step S3, when the in-situ concrete pile body (4) is poured in stages, before the splicing sleeve (3) of the previous stage is completed and the next stage of splicing sleeve (3) is to be poured, the splicing sleeve (3) is to be drilled downwards by no less than 50cm so that the bottom end of the splicing sleeve (3) is cut into the interior of the poured and yet to be initially set concrete, and then the subsequent splicing is carried out.

8. The construction technology for an ultra-deep dam foundation overburden seepage barrier wall according to claim 1, characterized in that, The first pipe (31) and the second pipe (32) are each provided with multiple sets, and one set is provided in the pipe wall on each of the opposite sides of the splicing sleeve (3); an air nozzle and at least two cement slurry nozzles (311) are provided inside any one side of the pipe wall. The cement slurry nozzles (311) are respectively provided above and below the air nozzle on the axis, so that the air nozzle is set between the two sets of cement slurry nozzles (311) to form a single-sided single-sided cluster spray assembly.

9. The construction technology of an ultra-deep dam foundation overburden seepage barrier wall according to claim 8, characterized in that, The total number of cement slurry nozzles (311) inside the two side walls of the splicing sleeve (3) is 8, and the total number of air nozzles is 2, forming a fluid jet structure.

10. The construction technology of an ultra-deep dam foundation overburden seepage barrier wall according to claim 1, characterized in that, In step S5, when performing directional cluster spraying, the cement slurry pressure is 30 to 40 MPa and the compressed gas pressure is 2.0 MPa; when the splicing sleeve (3) with the cluster spraying assembly is pulled upward, the swing spraying lifting speed of the splicing sleeve (3) is 30 to 50 cm / min.

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