Karst geological deep foundation pit excavation concentrated gushing point treatment structure

Abstract

The utility model discloses a kind of governance structure for the concentrated gushing point that appears in karst geology deep foundation pit excavation process.This scheme is by on-site positioning gushing point, partial excavation is deepened by micro-blasting, install inverted conical iron box in recess and realize gushing concentrated drainage with supporting bypass pipe;Subsequently, the combination of flexible primary sealing+hardening secondary plugging, heavy concrete and embedded grouting pipe with reinforcing mesh are used, to form containment structure;After heavy concrete hardens, carry out waterless operation and pour bottom plate, then under the condition of approaching pressure or micro-pressure, carry out grouting plugging to rock stratum, finally, use water stop flange to close standpipe and carry out secondary grouting reinforcement.This scheme realizes the closed-loop control of "containment-drainage-plugging-reduction", can effectively reduce pumping capacity, improve plugging reliability, and also take into account later structural reinforcement, to ensure the continuity of foundation pit construction and surrounding building safety.

Description

Technical Field

[0001] This utility model relates to the field of foundation pit support and groundwater control technology in building engineering, specifically to a structure for treating concentrated water inflow points in deep foundation pit excavation in karst geology. Background Technology

[0002] In karst geological conditions, groundwater is widely distributed, has numerous channels, and flows rapidly, making it difficult to fully identify and seal all seepage channels before excavation. Conventional measures such as cutoff walls and wellpoint dewatering can only lower the water level within the pit, but their effectiveness in controlling seepage around karst channels is limited, often leading to localized leakage, sudden surges, or even large-volume water inrushes, affecting the safety of pit construction and the stability of surrounding buildings. Summary of the Invention

[0003] Existing technologies lack a systematic approach to the coordinated management of multiple stages, including containment, drainage, blocking, and reduction. There is an urgent need for a technical approach that enables rapid on-site location, centralized drainage, reliable sealing, and subsequent reinforcement. This invention provides a complete process for quickly locating, containing, centrally draining, sealing in stages, grouting with low-volume pumping, and reinforcing structures at identified concentrated water inflow points during karst deep foundation pit construction. This ensures continuous foundation pit construction and minimizes the impact on the surrounding environment.

[0004] To achieve the above objectives, the present invention adopts the following technical solution: A structure for treating concentrated water inflow points in deep karst foundation pits includes a foundation pit with a water inflow area at the bottom. A depression is excavated within the water inflow area, and the depression has a truncated cone structure, wider at the top and narrower at the bottom. An inverted conical iron box is placed within the depression. The inverted conical iron box has a hollow truncated cone structure, and its volume is smaller than that of the depression. The inverted conical iron box is narrower at the top and wider at the bottom, with an open bottom. The inverted conical iron box is fastened to the bottom of the depression, and its downward projection covers the bottom surface of the depression.

[0005] A bypass pipe is installed on one side of the top of the preferred inverted conical iron box. A valve is installed on the bypass pipe, and the bypass pipe is set horizontally with its outlet facing the sump. The inverted conical iron box is used to realize the natural convergence of gushing water and guide it into the sump through the bypass pipe.

[0006] The top of the preferred inverted conical iron box is equipped with a vertical pipe. The vertical pipe is set vertically and temporary scaffolding is fixed around the outside of the vertical pipe. The vertical pipe is fixed by the temporary scaffolding.

[0007] A flexible material layer, consisting of cotton wool and / or clay, is provided at the bottom between the preferred inverted conical iron box and the recessed area.

[0008] A sealing agent layer is placed on top of the preferred inverted conical iron box and the recessed area, with the sealing agent layer located on top of the flexible material layer.

[0009] A ballast concrete layer with a thickness of 60-80mm is placed on top of the preferred sealing agent layer.

[0010] A steel mesh and anchor rods are installed in the primary counterweight concrete layer. One end of the anchor rod is inserted obliquely into the soil layer surrounding the depression area, and the outer end of the anchor rod is located within the depression area. The anchor rods are arranged around the inverted conical iron box.

[0011] Compared with the existing technology, the beneficial effects of the utility model are: the structure of this solution can achieve coordinated operation of inverted conical iron box enclosure, phased soft and hard sealing, heavy concrete, and low-pressure grouting, which greatly reduces the amount of water pumped out and shortens the construction period. Attached Figure Description

[0012] Other features, objects, and advantages of this invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings.

[0013] Figure 1 This is a schematic diagram showing the excavation of the foundation pit to the design elevation and the location of the water inrush point for this utility model.

[0014] Figure 2 This is a schematic diagram of the inverted conical iron box installed after the water inrush area is recessed in this utility model.

[0015] Figure 3 This is a schematic diagram illustrating the sealing of the leaking parts at the edge of the inverted conical iron box during the initial sealing stage of this utility model.

[0016] Figure 4 This is a schematic diagram of the secondary hardening and leak-sealing stage of this utility model.

[0017] Figure 5 This is a schematic diagram of the present invention, showing the arrangement of steel mesh, anchor bolts, etc. around the iron box.

[0018] Figure 6 This is a schematic diagram of the pouring of counterweight concrete according to this utility model.

[0019] Figure 7 This is a schematic diagram of the water pump placement in this utility model.

[0020] Figure 8 This is a schematic diagram showing the small tube reserved for this utility model.

[0021] Figure 9 This is a schematic diagram of the backfill concrete of this utility model. Detailed Implementation

[0022] The present invention will be further described in detail below through embodiments. The embodiments are only used to illustrate the present invention and do not limit the scope of the present invention.

[0023] A structure for treating concentrated water inflow points in deep karst foundation pits includes a foundation pit 1, a water inflow area 2 at the bottom of the foundation pit 1, and a recessed area 3 excavated within the water inflow area 2. The recessed area 3 has a truncated cone structure, wider at the top and narrower at the bottom. Since the water inflow point is located within the water inflow area 2, the water flowing from the water inflow point enters the recessed area 3 by excavating the recessed area 3 downward within the water inflow area 2. An inverted conical iron box 4 is placed within the recessed area 3. The inverted conical iron box 4 has a hollow truncated cone structure, and its volume is smaller than that of the recessed area 3. Moreover, the inverted conical iron box 4 is narrower at the top and wider at the bottom, with an open bottom. The inverted conical iron box 4 is fastened to the bottom of the recessed area 3. Furthermore, the downward projection of the inverted conical iron box 4 covers the bottom surface of the recessed area 3. A bypass pipe 5 is installed on one side of the top of the inverted conical iron box 4. A valve is installed on the bypass pipe 5, which is horizontally positioned with its outlet facing the sump 8. The inverted conical iron box 4 is used to allow the gushing water to naturally converge and be guided into the sump 8 through the bypass pipe 5. A vertical pipe 6 is installed on the top of the inverted conical iron box 4. The vertical pipe 6 is vertically positioned, and temporary scaffolding 7 is fixed around the outside of the vertical pipe 6 to secure it. The inverted conical iron box 4 encloses the gushing water area 2, allowing the gushing water to be discharged into the sump 8 through the bypass pipe 5. A bottom between the inverted conical iron box 4 and the recessed area 3 is provided with A flexible material layer 10, composed of cotton wool and / or clay, is placed on top. The flexible material (such as cotton wool or clay bags) is used to initially seal the leakage areas at the edges of the inverted conical iron box 4. A sealing agent layer 11 is then placed on top of the flexible material layer 10 between the inverted conical iron box 4 and the recessed area 3. The sealing agent layer 11 is made of cement or water glass and is used for a secondary hardening and sealing of the inverted conical iron box 4. Furthermore, a ballast concrete layer 12, 60-80 mm thick, is placed on top of the sealing agent layer 11. A steel mesh 13 and anchor rods 9 are installed inside the ballast concrete layer 12. One end of the anchor rod 9 is inserted obliquely into the soil layer surrounding the depression area 3, and the outer end of the anchor rod 9 is located inside the depression area 3. The anchor rods 9 are arranged around the inverted conical iron box 4. The anchor rods 9 provide pull-out support for the ballast concrete layer 12. In addition, a grouting pipe 13 is installed around the depression area 3. The grouting pipe 13 is installed at an angle and extends into the area around the seepage channel 14. A riser 15 is installed on the top of the inverted conical iron box 4. The riser 15 and the inverted conical iron box 4 are connected by a flange, and a water-stop steel ring is installed between the flanges. After the strength of the counterweight concrete layer 12 meets the design requirements, the valve on the bypass pipe is closed and the water pump 16 is used to pump out the water inside the inverted conical iron box 4. Then, a structural cushion layer 17 is laid at the bottom of the foundation pit 1 and the bottom slab concrete layer 18 is poured. The cushion layer is an intermediate structural layer between the reinforced concrete foundation and the foundation soil. It is made of plain concrete and mainly serves to level, isolate, and protect the foundation. After the bottom slab concrete layer 18 hardens to the design strength, the grouting pipe 13 is used to grout and seal the rock strata around the water inflow point under near-flat or low-pressure conditions. After the grouting is completed, the riser 6 is removed and the remaining pipes of the inverted conical iron box 4 are sealed with a water-stop flange. A small pipe 19 is reserved for subsequent micro-pump pumping and secondary grouting. Finally, the sealing point is leveled with concrete and backfilled.

[0024] A structure for treating concentrated water inflow points in deep karst foundation pit excavation also relates to a method for treating concentrated water inflow points in deep karst foundation pit excavation, including the following steps: Step 1: Water inflow point location: Determine the location of concentrated water inflow points formed by karst channels bypassing the anti-seepage curtain from deep within the stratum in the foundation pit; that is, when the foundation pit is excavated to the design elevation, the location of concentrated water inflow points formed by karst channels bypassing the anti-seepage curtain from deep within the stratum in the foundation pit that cannot be effectively blocked by the anti-seepage curtain and cannot be sealed by temporary grouting is determined through on-site observation, and the water inflow volume is estimated.

[0025] Step 2: Excavation: Deepen the excavation of the concentrated water inflow area to form a local depression; specifically, use micro-blasting combined with mechanical chiseling to deepen the excavation of the concentrated water inflow area to form a local depression for installing water inflow control devices and providing working space for subsequent operations.

[0026] Step 3: Install the inverted conical iron box: Cover the recessed area with an inverted conical iron box. The top of the inverted conical iron box is equipped with a horizontal bypass pipe and a vertical pipe. The horizontal bypass pipe is used to guide the gushing water to a temporary sump, and the vertical pipe is used for later drainage and sealing. Specifically, an inverted conical iron box (or enclosure) is placed over the recessed area. The top of the iron box is equipped with a horizontally arranged bypass pipe with a valve that guides the gushing water to the temporary sump, and a vertically arranged vertical pipe, which is fixed by temporary scaffolding. The purpose of the iron box is to enclose the gushing water area and ensure that the gushing water is drained into the sump through the bypass pipe. Anchor rods are drilled around the iron box to increase the buoyancy resistance for the next step of ballast concrete. Step 4: Initial sealing of water leakage around the iron box: Use flexible materials to initially seal the leakage points on the edge of the inverted conical iron box, so that the water flow is concentrated and directed to the horizontal bypass pipe; specifically, use flexible materials such as cotton wool and clay to initially seal the leakage points on the edge of the iron box in the water gushing area, ensuring that the water flow is concentrated and directed to the bypass pipe.

[0027] Step 5: Secondary Sealing of Leaks Around the Iron Box: Use a quick-setting sealant to further seal around the inverted conical iron box until there is virtually no leakage. Use cement, water glass, or other sealants to further seal around the iron box, ensuring no further leakage occurs. The sealant can be cement-based quick-setting sealant, polyurethane grouting sealant, epoxy resin sealant, etc. These materials can be used alone or in combination, depending on the severity of the leakage, the substrate material, construction conditions, and waterproofing durability requirements. During construction, generally, the leakage point is cleaned first, and then the selected sealant is used to seal it, ensuring no further leakage occurs around the iron box.

[0028] Step 6: Pouring the counterweight concrete: A reinforcing mesh is laid around the inverted conical iron box, and grouting pipes are pre-embedded. Then, the counterweight concrete is poured, with the top of the concrete flush with the design elevation of the foundation pit floor. The riser passes through the counterweight concrete and extends outwards. After ensuring there is basically no water leakage around the iron box, a reinforcing mesh is laid around it and welded to the anchor rods. Grouting pipes are pre-embedded around the iron box (for later grouting to seal leaks in the strata). Next, the capping concrete is poured, with the top of the capping concrete at the same elevation as the foundation pit floor. The thickness of the counterweight concrete is approximately 60 to 80 cm. A steel ring is installed at the bottom of the riser at the top of the iron box, serving as a water-stop ring for the next step of pouring the foundation slab. The extended steel riser is connected with flanges for easy disassembly and later sealing. Step 7: Pouring the structural cushion layer and base slab concrete: Close the valve of the horizontal bypass pipe to allow all the gushing water to enter the riser. Control the water level in the riser by pumping water. Pouring the structural cushion layer and permanent base slab concrete under waterless conditions in the foundation pit; specifically, after the counterweight concrete reaches its strength, close the valve of the horizontal pipe to ensure that all the gushing water enters the riser. Place the water pump into the iron box through the riser to pump water and control the water level in the riser (pumping can be stopped as needed). Pouring the cushion layer and base slab concrete under waterless conditions in the foundation pit. Step 8: Grouting to seal the stratum at the gushing point: After the permanent base slab concrete reaches its design strength, grout the stratum around the gushing point through the pre-embedded grouting pipe to seal the leak; specifically, under conditions where the pressure difference between the riser water level and the groundwater level outside the foundation pit is small or equal, grout the stratum around the gushing point through the grouting pipe to seal the leak, in order to further reduce or completely control the gushing water at the seepage point.

[0029] Step 9: Riser Sealing and Grouting Reinforcement: After the sealing and grouting are completed, remove the water pump, seal and grout the riser to complete the final sealing of the water inflow point. Specifically, after the sealing and grouting are completed, remove the water pump and riser, seal the remaining riser with a water-stop flange, and leave a small reserved pipe on the sealing plate. A mini water pump can be placed in the small pipe to continue pumping water. After the flange is sealed, remove the small water pump and perform well sealing grouting through the small pipe. After the grouting strength reaches the required level, remove the grouting pipe, weld the small pipe opening to seal it, and finally level the well sealing point with concrete.

[0030] This solution enables rapid location and centralized drainage: it achieves localized containment and centralized drainage of the water inrush point through an inverted conical iron box and bypass pipe; Phased and reliable sealing: Flexible primary sealing + hardened secondary sealing + pressure grouting triple sealing significantly reduces the risk of leakage; Small drainage volume and simple construction: Waterless operation can be achieved after the weighted concrete has hardened, and the drainage volume is much lower than that of traditional wellpoint dewatering. Compatible with subsequent reinforcement: The pre-embedded grouting pipe and the closed structure of the steel pipe provide convenience for subsequent reinforcement and maintenance; Ensure the safety of the foundation pit and its surroundings: effectively control the water level inside the foundation pit to prevent the surrounding buildings from settling or tilting due to a significant drop in groundwater.

[0031] The specific inverted cone-shaped iron box enclosure: the inverted cone structure forms a natural confluence area, and the bypass pipe achieves centralized drainage. This is a dedicated "physical fence" for the sudden surge of karst channels.

[0032] Two-stage sealing: First, flexible materials (cotton wadding, clay bags) are used to quickly stop the leak, and then hardening materials (cement / water glass) are used for permanent sealing, forming a progressive sealing that significantly reduces construction risks.

[0033] Counterweight concrete + steel mesh + anchor bolts: A high pull-out resistance structure is formed around the iron box to prevent the structure from floating or becoming unstable due to water pressure.

[0034] Low-pressure / micro-pressure grouting: After the base plate has hardened, it is used to perform secondary sealing with near-flat or micro-pressure, which also takes into account the later reinforcement. This is an effective grouting method for fine cracks in karst channels.

[0035] The overall "enclosure-drainage-blocking-lowering" closed loop: from positioning, enclosure control, drainage, phased sealing, low-pressure grouting to final backfilling, it forms an integrated construction process.

Claims

1. A structure for treating concentrated water inflow points in deep foundation pit excavation in karst geology, characterized in that, The structure includes a foundation pit with a water inflow area at the bottom. Within the water inflow area, there is a recessed area with a truncated cone structure. The recessed area is wider at the top and narrower at the bottom. An inverted conical iron box is placed within the recessed area. The inverted conical iron box has a hollow truncated cone structure, and its volume is smaller than that of the recessed area. Moreover, the inverted conical iron box is narrower at the top and wider at the bottom, with an open bottom. The inverted conical iron box is fastened to the bottom of the recessed area, and its downward projection covers the bottom surface of the recessed area.

2. The structure for treating concentrated water inflow points in karst deep foundation pit excavation according to claim 1, characterized in that, A bypass pipe is installed on one side of the top of the inverted conical iron box. A valve is installed on the bypass pipe, and the bypass pipe is set horizontally with its outlet facing the sump. The inverted conical iron box is used to realize the natural convergence of gushing water and guide it into the sump through the bypass pipe.

3. The structure for treating concentrated water inflow points in karst deep foundation pit excavation according to claim 2, characterized in that, A vertical pipe is installed on the top of the inverted conical iron box. The vertical pipe is set vertically and temporary scaffolding is fixed around the outside of the vertical pipe. The vertical pipe is fixed by the temporary scaffolding.

4. The structure for treating concentrated water inflow points in karst deep foundation pit excavation according to claim 3, characterized in that, A flexible material layer, consisting of cotton wool and / or clay, is placed at the bottom between the inverted conical iron box and the recessed area.

5. The structure for treating concentrated water inflow points in karst deep foundation pit excavation according to claim 4, characterized in that, A sealing agent layer is placed on top of the inverted conical iron box and the recessed area, with the sealing agent layer located on top of the flexible material layer.

6. The structure for treating concentrated water inflow points in karst deep foundation pit excavation according to claim 5, characterized in that, A 60-80mm thick ballast concrete layer is placed on top of the sealant layer.

7. The structure for treating concentrated water inflow points in karst deep foundation pit excavation according to claim 6, characterized in that, A steel mesh and anchor rods are installed inside the ballast concrete layer. One end of the anchor rod is inserted obliquely into the soil layer surrounding the depression area, and the outer end of the anchor rod is located within the depression area. The anchor rods are arranged around the inverted conical iron box.

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