Karst region foundation pit gushing water treatment and reinforcement method

Abstract

The application provides a karst region foundation pit gushing water treatment and reinforcement method, wherein the gushing water treatment comprises the following specific steps: determining the position of a cave cavity in the foundation pit range; analyzing and evaluating the risk level of gushing water damage when the foundation pit is excavated to a preset depth and in the use stage of the foundation pit; vertically arranging a flow guide hole, the bottom end of the flow guide hole penetrating through the cave cavity, and a flow guide pipe being sleeved in the flow guide hole, and a water permeable hole being arranged on the side wall of the flow guide pipe in the cave cavity; fixing the flow guide pipe; vertically arranging a plurality of gravel filling holes communicating with the cave cavity, and inserting a flow meter for gushing water observation into the gravel filling hole; filling gravel into the cave cavity through the gravel filling hole; foundation pit excavation support and underground gushing water monitoring. The application can overcome the potential subsequent risk caused by plugging in the traditional karst cavity treatment, and improve the uplift and compression bearing capacity of the foundation pit.

Description

Technical Field

[0001] This invention relates to the field of water inrush prevention and control technology, and in particular to a method for treating and reinforcing water inrush in foundation pits in karst areas. Background Technology

[0002] Traditional methods for preventing and reinforcing water inrushes at the bottom of foundation pits in karst areas involve filling the karst cavities after determining the location of the inrush. The usual practice is to first clear the silt around the inrush point, then seal the groundwater in the foundation pit with cement grout. After controlling the inrush, high-grade commercial concrete is poured into the karst cavity to squeeze out the water, silty clay slurry, fine sand, gravel, and some of the mixed commercial concrete. This is then gradually pumped out using coarse-drilled hoses. Theoretically, water inrushes can also be controlled by diversion measures during construction and filling the karst cavities later. However, these methods require significant labor and economic investment and cannot quickly and effectively control karst water inrushes throughout the entire process. Furthermore, the partial sealing of karst cavities can pose a risk of damage to subsequent construction and surrounding buildings and structures due to the inrush. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for the treatment and reinforcement of sudden water inrush in foundation pits in karst areas. This method overcomes the potential subsequent risks caused by sealing in traditional karst cavity treatment and improves the uplift and compressive bearing capacity of the foundation pit.

[0004] To achieve the above objectives, the present invention provides a method for treating sudden water inrush in foundation pits in karst areas, comprising the following specific steps:

[0005] S1. Determine the location of karst cavities within the excavation pit area;

[0006] S2. Analyze and evaluate the risk level of sudden water inrush damage during the excavation of the foundation pit to the preset depth and during the use of the foundation pit;

[0007] S3. A vertically arranged guide hole is provided, the bottom end of which passes through the cavity of the karst cave, and a guide pipe is sleeved inside the guide hole. Water-permeable holes are provided on the side wall of the guide pipe located in the cavity of the karst cave.

[0008] S4. Fixed guide tube;

[0009] S5. Vertically set several gravel filling holes that communicate with the cavity of the karst cave, and insert flow meters for observing sudden water inrush into the gravel filling holes.

[0010] S6. Fill the cavity of the cave with gravel through the gravel filling hole;

[0011] S7. Excavation and support of foundation pits and monitoring of groundwater inrush.

[0012] Optionally, in step S1, the location of the karst cavity within the foundation pit area is determined based on geotechnical engineering exploration, geotechnical engineering investigation, and foundation drawings.

[0013] Optionally, in step S2, based on step S1, according to Bernoulli's principle, on-site investigation of the characteristics and causes of underground structural damage caused by sudden water inrush in karst areas, and rock strata parameters in karst areas, the risk level of sudden water inrush damage during the excavation of the foundation pit to the preset depth and the use stage of the foundation pit is analyzed and evaluated.

[0014] Optionally, in step S4, grouting is performed on the gap between the guide hole at the top of the cave cavity and the outer wall of the guide pipe to fix the guide pipe.

[0015] Optionally, the diameter d1 of the guide hole is in the range of 600mm≤d≤800mm.

[0016] Optionally, the diameter d2 of the crushed stone filling hole is in the range of 100mm≤d≤400mm.

[0017] The present invention also provides a reinforcement method based on the above-mentioned method for controlling sudden water inrush, comprising the following specific steps:

[0018] (S1) When the foundation pit is excavated to the preset depth, on-site sampling is conducted and the physical and mechanical properties of the rock strata at the bottom of the foundation pit are tested. Based on the test results and foundation pit monitoring data, the anti-surge bearing capacity of the bottom of the foundation pit is evaluated after the crushed stone filling hole and the diversion pipe are grouted and piled. When the evaluation results meet the requirements, the flow capacity of the karst cavity is retained. When the evaluation results do not meet the requirements, grout is injected into the karst cavity through the crushed stone filling hole.

[0019] (S2) Grouting into the gravel filling hole;

[0020] (S3) Grouting into the guide pipe.

[0021] Optionally, in step (S1), the physical and mechanical index tests include shear strength, deformation modulus, and block integrity tests.

[0022] Optionally, in step (S2), the quick-setting expanding grout is injected into the crushed stone filling hole by a compaction grouting method.

[0023] Optionally, in step (S3), the quick-setting expansion grout is injected into the guide pipe by a compaction grouting method.

[0024] Beneficial effects:

[0025] The present invention provides a method for treating sudden water inrush in karst foundation pits. By setting up diversion pipes and gravel filling holes, the water flow characteristics of the karst cavities are preserved, which can significantly reduce the sudden water inrush pressure at the bottom of the foundation pit and serve as the main discharge channel and backup channel for karst sudden water inrush.

[0026] Based on the method for treating sudden water inrush, the present invention provides a method for reinforcing foundation pits in karst areas. By filling, solidifying, and compacting the diversion pipes and gravel filling holes with grout, the method rapidly transforms the diversion pipes and gravel filling holes into part of the uplift and compressive bearing capacity of the underground structure. If necessary, it can also preserve the flow performance of the karst cavity. The structure is ingeniously designed and fully utilizes its functions, effectively reducing the cost of preventing and controlling sudden water inrush in karst areas and overcoming the potential subsequent risks caused by sealing in traditional karst cavity treatment methods. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the structures shown in these drawings without creative effort.

[0028] Figure 1 This is a cross-sectional view of a typical stratigraphic structure in a karst region.

[0029] Figure 2 This is a cross-sectional view of the method for treating sudden water inrush in foundation pits in karst areas disclosed in this invention;

[0030] Figure 3 This is a cross-sectional view of the foundation pit excavation to a preset depth in the karst area foundation pit reinforcement method disclosed in this invention;

[0031] Figure 4 This is a cross-sectional view showing the retention of flow capacity in the karst cavity of the reinforcement method for foundation pits in karst areas disclosed in this invention.

[0032] Figure 5 This is a cross-sectional view of the grouting filling of karst cavity in the karst area foundation pit reinforcement method disclosed in this invention.

[0033] Attached reference numerals: 1. Cave cavity; 2. Surface disturbed soil; 3. Overburden layer; 4. Soluble rock layer; 5. Preset depth; 6. Drainage hole; 7. Drainage pipe; 8. Water permeable hole; 10. Crushed stone filling hole; 11. Crushed stone; 12. Flow meter; 13. Sediment; 14. Grouting pipe.

[0034] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0035] 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 a part of the embodiments of the present invention, and not all of them. 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.

[0036] In the description of this invention, unless otherwise explicitly defined, terms such as "set up," "install," and "connect" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this invention in conjunction with the specific content of the technical solution.

[0037] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0038] Example 1:

[0039] See Figure 1 and 2 A method for treating sudden water inrush in a karst foundation pit according to a first embodiment of the present invention includes the following specific steps:

[0040] S1. Determine the location of cavity 1 within the excavation pit area;

[0041] The typical stratigraphic structure of the area where the karst cavity 1 is located, from top to bottom, consists of surface disturbed soil 2, overburden 3, and soluble rock layer 4. The karst cavity 1 is located within the soluble rock layer 4. The location of the karst cavity 1 within the foundation pit area is known based on geotechnical engineering exploration, geotechnical engineering investigation, and foundation drawings.

[0042] S2. Analyze and evaluate the risk level of sudden water inrush damage during the excavation of the foundation pit to the preset depth of 5 and during the use of the foundation pit;

[0043] The preset depth 5 is determined based on the location of the karst cavity 1 in step 1. Based on step S1, according to Bernoulli's principle, on-site investigation of the characteristics and causes of underground structural damage caused by sudden water inrush in karst areas, and parameters of soluble rock strata in karst areas, the risk level of sudden water inrush damage during the excavation of the foundation pit to the preset depth 5 and during the use of the foundation pit is analyzed and evaluated.

[0044] S3. A vertical guide hole 6 is set, the bottom end of the guide hole 6 passes through the cavity 1 of the karst cave, and a guide pipe 7 is sleeved inside the guide hole 6. A water-permeable hole 8 is set on the side wall of the guide pipe 7 located in the cavity 1 of the karst cave.

[0045] Within the planar boundary of the karst cave at a certain interval in the foundation pit, diversion holes 6 are constructed vertically, penetrating the karst cave cavity 1 at their bottom and entering the lower stable soluble rock layer 4, and then diversion pipes 7 are inserted. At the same time, in the section of the karst cave cavity 1, permeable holes 8 are evenly provided on the side wall of the diversion pipe 7 to facilitate the entry of the sudden water in the karst cave cavity 1 into the diversion pipe 7 for orderly discharge.

[0046] S4, Fixed guide tube 7;

[0047] S5. Vertically set several gravel filling holes 10 that are connected to the cavity 1 of the cave, and insert flow meters 12 for observing sudden water inrush into the gravel filling holes 10.

[0048] Within the boundary of the karst cavity 1, which is at risk of sudden water inrush, gravel filling holes 10 are vertically installed at certain intervals, and a flow meter 12 for observing sudden water inrush is inserted into the gravel filling hole 10.

[0049] S6. Fill the cavity 1 of the cavern with gravel through the gravel filling hole 10;

[0050] The slenderness ratio and ellipticity of the crushed stone 11 are controlled to better fill the pores, reduce the amount of subsequent grouting, and save costs. Crushed stone 11 is filled into the cavity 1 of the karst cave through the crushed stone filling hole 10. During the filling process, the filling quality is controlled in conjunction with the guide pipe and video monitoring technology to fill the cavity 1 area as evenly as possible. At the same time, the crushed stone filling hole 10 is not sealed temporarily, serving as a backup channel for emergency drainage of sudden water inrush and for water level monitoring during the excavation of the foundation pit.

[0051] S7. Excavation and support of foundation pit and monitoring of groundwater inrush. During the excavation and support of foundation pit, the heave resistance of the foundation pit is monitored by methods such as elevation measurement and vertical displacement monitoring of soil layers. The water volume change of groundwater inrush in the karst cavity 1 is monitored by flow meter 12, and the flow meter 12 and the diversion pipe 7 are protected.

[0052] Based on Bernoulli's principle in hydraulics, the method for treating sudden water inrush in karst pits in this invention, by setting up a diversion pipe 7 and a gravel filling hole 10, first preserves the water flow characteristics of the karst cavity, which can significantly reduce the sudden water inrush pressure at the bottom of the pit. This serves as the main discharge channel and backup channel for karst sudden water inrush, overcoming the potential subsequent risks caused by sealing in traditional karst cavity treatment.

[0053] See Figure 2In some embodiments of the present invention, in step S4, grouting is performed on the gap between the guide hole 6 located at the top of the cave cavity 1 and the outer wall of the guide pipe 7 to fix the guide pipe 7.

[0054] Preferably, the rapid-setting expanding grout is injected in sections from bottom to top into the gap between the guide hole 6 and the guide pipe 7 at a preset depth 5 from the top of the karst cavity 1 to the bottom of the foundation pit. This sectioned grouting method ensures high precision and controllable grouting effect. The rapid-setting expanding grout solidifies and stabilizes quickly. First, a small amount of grout is injected to seal the gap between the guide hole 6 and the guide pipe 7 at the top of the karst cavity 1. Then, a compaction grouting method is used to increase the grout volume, injecting the grout into the gap between the guide hole 6 and the guide pipe 7 to fix the guide pipe 7.

[0055] As the foundation pit is excavated to the preset depth 5, the guide holes 6 and guide pipes 7 above the preset depth 5 are removed. Therefore, grouting is only performed in the gap between the top of the karst cavity 1 and the preset depth 5, which can reduce the waste of grout and save costs.

[0056] See Figure 2 In some embodiments of the present invention, the diameter d1 of the guide hole 6 is in the range of 600mm≤d≤800mm. The guide pipe 7 is a steel pipe, and the outer diameter of the guide pipe 7 is preferably 100mm smaller than the diameter d1 of the guide hole 6.

[0057] See Figure 2 In some embodiments of the present invention, the aperture d2 of the gravel filling hole 10 is in the range of 100mm≤d≤400mm. The aperture d2 is determined according to the size of the karst cavity 1, the amount of water flowing in and the flow rate, etc. The aperture of the gravel filling hole 10 is preferably 300mm.

[0058] Example 2:

[0059] See Figures 3-5 According to a second embodiment of the present invention, a reinforcement method based on the above-described method for controlling sudden water inrush includes the following specific steps:

[0060] (S1) The foundation pit is excavated to the preset depth of 5. On-site sampling is conducted, and physical and mechanical properties tests are performed on the bottom of the foundation pit. Based on the test results and foundation pit monitoring data, the anti-surge bearing capacity of the bottom of the foundation pit is evaluated after the crushed stone filling hole 10 and the diversion pipe 7 are grouted and piled. The physical and mechanical properties tests include shear strength, deformation modulus, and block integrity tests.

[0061] When the evaluation results meet the requirements, the permeability of the karst cavity 1 can be preserved. By using the solidification grouting of the stone filling hole 10 and the diversion pipe 7 to form piles, the bearing capacity of the foundation can be strengthened and improved, and the uneven settlement and deformation of the underground structure can be controlled.

[0062] When the evaluation results do not meet the requirements, grouting is injected into the karst cavity 1 through the gravel filling hole 10. First, the weather during the construction period is selected to avoid the potential occurrence of sudden water inrush. The gravel filling hole 10 is properly cleared, and the grouting pipe 14 is inserted and installed into the gravel filling hole 10. Grouting is carried out on the gravel layer in the karst cavity 1 through the grouting pipe 14. The grouting pipe 14 is preferably a seamless steel pipe. The grouting pipe 14 is vibrated and inserted into the gravel layer for no less than 500mm, and is centered. The grout is a non-dispersible micro-expansion gelling grout, which is injected slowly in layers at low pressure to avoid additional diffusion of grout and pollution of groundwater.

[0063] (S2) Grout into the crushed stone filling hole 10.

[0064] Rapid-setting expansion grouting material was used to solidify, fill, and compact the gravel filling holes 10 and grouting pipes 14 from the bottom of the foundation pit to the top of the karst cave.

[0065] (S3) Grouting into the guide pipe 7. The sediment 13 at the bottom of the guide pipe 7 does not require special treatment.

[0066] The interior of the diversion pipe 7 is filled, solidified and compacted by using a fast-setting expansion grout. Some of the grout diffuses through the permeable holes 8 into the adjacent gravel layer in the cavity 1 of the karst cave, forming an enlarged cross-section of the enclosed body and quickly forming a pile. This pile has good tensile and compressive bearing capacity.

[0067] After the gravel filling hole 10 and the diversion pipe 7 are grouted to form a pile, the sudden surge of water in the cavity 1 of the karst cave cannot be discharged, which will generate buoyancy. The gravel filling hole 10 and the diversion pipe 7 formed by grouting can resist the buoyancy of the sudden surge of water.

[0068] Based on the method for treating sudden water inrush, the present invention provides a method for reinforcing foundation pits in karst areas. By filling, solidifying, and compacting the diversion pipe 7 and the gravel filling hole 10 with grout, the diversion pipe 7 and the gravel filling hole 10 are quickly transformed into part of the uplift and compressive bearing capacity of the underground structure. If necessary, the flow performance of the karst cavity can also be preserved. The structure is ingeniously designed and fully utilizes its functions, thereby improving the uplift and compressive bearing capacity of the foundation pit and effectively reducing the cost of preventing and controlling sudden water inrush in karst areas.

[0069] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made using the contents of the present invention specification and drawings under the inventive concept of the present invention, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A reinforcement method for treating sudden water inrush in foundation pits in karst areas, characterized in that, The methods for controlling sudden water inrush include the following specific steps: S1. Determine the location of karst cavities within the foundation pit area; In step S1, the location of karst cavities within the foundation pit area is determined based on geotechnical engineering exploration, geotechnical engineering investigation, and foundation drawings. S2. Analyze and evaluate the risk level of sudden water inrush damage during the excavation of the foundation pit to the preset depth and during the use of the foundation pit; S3. A vertically arranged guide hole is provided, the bottom end of which passes through the cavity of the karst cave, and a guide pipe is sleeved inside the guide hole. Water-permeable holes are provided on the side wall of the guide pipe located in the cavity of the karst cave. S4. Fixed guide tube; S5. Vertically set several gravel filling holes that communicate with the cavity of the karst cave, and insert flow meters for observing sudden water inrush into the gravel filling holes. S6. Fill the cavity of the cave with gravel through the gravel filling hole; S7. Excavation and support of foundation pit and monitoring of groundwater inrush; During the excavation and support of foundation pit, the anti-heaving of foundation pit is monitored by elevation measurement and vertical displacement monitoring of soil layers, and the water volume change of groundwater inrush in the cavity of the karst cave is monitored by flow meter, and the flow meter and diversion pipe are protected. The subsequent reinforcement methods include the following specific steps: (S1) When the foundation pit is excavated to the preset depth, on-site sampling is conducted and the physical and mechanical properties of the rock strata at the bottom of the foundation pit are tested. Based on the test results and foundation pit monitoring data, the anti-surge bearing capacity of the bottom of the foundation pit is evaluated after the crushed stone filling hole and the diversion pipe are grouted and piled. When the evaluation results meet the requirements, the flow capacity of the karst cavity is retained. When the evaluation results do not meet the requirements, grout is injected into the karst cavity through the crushed stone filling hole. (S2) Grouting into the gravel filling hole; (S3) Grouting into the guide pipe.

2. The reinforcement method of the method for treating sudden water inrush according to claim 1, characterized in that, In step S2, based on step S1, according to Bernoulli's principle, on-site investigation of the characteristics and causes of underground structural damage caused by sudden water inrush in karst areas, and rock strata parameters in karst areas, the risk level of sudden water inrush damage during the excavation of the foundation pit to the preset depth and the use stage of the foundation pit is analyzed and evaluated.

3. The reinforcement method of the method for treating sudden water inrush according to claim 1, characterized in that, In step S4, grout is injected into the gap between the guide hole at the top of the cave cavity and the outer wall of the guide pipe to fix the guide pipe.

4. The reinforcement method of the method for treating sudden water inrush according to claim 1, characterized in that, The diameter d1 of the guide hole is in the range of 600mm≤d≤800mm.

5. The reinforcement method of the method for treating sudden water inrush according to claim 1, characterized in that, The diameter d2 of the crushed stone filling hole is in the range of 100mm≤d≤400mm.

6. The reinforcement method of the method for treating sudden water inrush according to claim 1, characterized in that, In step (S1), the physical and mechanical index tests include shear strength, deformation modulus and block integrity tests.

7. The reinforcement method of the method for treating sudden water inrush according to claim 1, characterized in that, In step (S2), the quick-setting expansion grout is injected into the crushed stone filling hole by the compaction grouting method.

8. The reinforcement method of the method for treating sudden water inrush according to claim 1, characterized in that, In step (S3), the quick-setting expansion grout is injected into the guide pipe by the compaction grouting method.

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