Guiding type grouting structure and grouting method suitable for karst cave cast-in-place pile

Abstract

The invention belongs to the field of geotechnical engineering, and provides a guiding type grouting structure and grouting method suitable for a karst cave cast-in-place pile. The guiding type grouting structure suitable for the karst cave cast-in-place pile comprises a plurality of pressure grouting pipes, a plurality of vacuum guiding pipes and a vacuumizing pump. The pressure grouting pipes and the vacuum guide pipes are arranged around a to-be-constructed pile position at intervals; each pressure grouting pipe is provided with a slurry pattern hole in the range of the karst cave, and each vacuum guide pipe comprises sub-pipes at different depth positions in the range of the karst cave; the pressure grouting pipe is used for injecting pressure grouting into cement paste or double-liquid grout, so that a high-pressure area is formed around the pressure grouting pipe; the vacuumizing pump is connected with the vacuum guide pipe and is used for extracting air in the karst cave, so that a low-pressure area is formed around the vacuum guide pipe; pressure difference is generated on the periphery of a to-be-built pile, and injected grout is guided to form a cemented solidified body on the periphery of the to-be-built pile according to the set direction by means of the physical characteristic that liquid pressure drives flowing.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering, and in particular relates to a guided grouting structure and grouting method suitable for karst cave cast-in-place piles. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] In the process of constructing cast-in-place piles in areas with strong karst development, the karst development is difficult to detect. When facing karst caves filled with soft plastic or fluid plastic materials during the construction of cast-in-place piles, various situations such as inability to form piles, pile hole deviation, stuck drill, and drill dropping occur. The existing grouting construction technology generally adopts the method of grouting and treating karst caves layer by layer, which results in extremely low efficiency, seriously affects construction efficiency, and causes waste of resources.

[0004] Existing technology provides a method for constructing cast-in-place piles in complex karst strata, which involves injecting fluidized solidified soil to seal the karst caves. However, this method does not clearly define the treatment of the karst caves and the method for filling them. The existing technology also involves drilling multiple injection holes in a ring at intervals around the perimeter of the area corresponding to the karst cave in the rock strata; solid filler is injected into the karst cave through each injection hole until the solid filler reaches the top area of ​​each karst cave, and repeated filling and grouting are then performed. This method does not clearly define the treatment method for beaded karst caves, and the karst cave treatment is not completed in one step. Therefore, when using grouting to treat karst caves, how to ensure the quality of the pile foundation, improve construction efficiency, and save construction costs during the pile foundation construction process is an urgent problem to be solved.

[0005] The two existing methods mentioned above are complex and use self-flowing grouting, which makes it impossible to control the flow direction of the grout during the grouting process. This makes it easy for the grout to run out or leak, resulting in poor grouting effect. The grouting effect on subsequent pile foundation construction is not obvious, and it is impossible to form a solidified area within the preset range. It also fails to solve problems such as pile hole collapse. Summary of the Invention

[0006] In order to solve the technical problems existing in the background art, the present invention provides a guided grouting structure and grouting method suitable for karst cave cast-in-place piles. It can control the grout flow direction and form a solidified area according to a preset range. It can effectively target underground environments such as karst caves that are not fully explored, and can achieve the purpose of one-time karst cave treatment and solve the problem of pile collapse during cast-in-place pile formation.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: The first aspect of the present invention provides a guided grouting structure suitable for karst cave cast-in-place piles.

[0008] A guided grouting structure suitable for karst cave cast-in-place piles includes: Several pressure grouting pipes, several vacuum guide pipes, and a vacuum pump; The pressure grouting pipes and vacuum guide pipes are arranged at intervals around the pile locations to be constructed. Each of the pressure grouting pipes has grout holes opened within the karst cave area, and each of the vacuum guide pipes includes sub-pipes at different depths within the karst cave area; The pressure grouting pipe is used to inject cement grout or dual-liquid grout to form a high-pressure zone around the pressure grouting pipe; the vacuum pump is connected to the vacuum guide pipe to extract air from the karst cave, so that a low-pressure zone is formed around the vacuum guide pipe; a pressure difference is generated around the proposed pile, and the physical property of the liquid itself driving the flow is used to guide the injected grout to form a cemented solidified body around the proposed pile in a set direction.

[0009] In one embodiment, the pressure grouting pipe is also connected to a grouting pressure detection device, which is used to detect the pressure inside the pressure grouting pipe until the grouting pressure is the same as the pressure inside the grouting pipe, at which point the grouting is terminated.

[0010] In one embodiment, the top of the vacuum guide tube is also connected to a slurry monitoring device, which is used to detect the slurry flow.

[0011] As one implementation method, the bottom of the vacuum guide tube is also provided with an anti-clogging wire mesh.

[0012] As one implementation method, for every x increase in the diameter of the pile to be constructed, an additional pressure grouting pipe and a vacuum guide pipe are added; the distance between the pressure grouting pipe and the vacuum guide pipe and the center of the pile to be constructed is set as d: d=(D+x) / 2; where D is the diameter of the pile to be constructed; and x is a set constant.

[0013] In one implementation, the size and shape of the grouting holes in the pressure grouting pipe are determined by the size and shape of the karst cave.

[0014] A second aspect of the present invention provides a grouting method suitable for guided grouting structures of karst cave cast-in-place piles.

[0015] A grouting method for guided grouting structures suitable for karst cave cast-in-place piles includes: Drilling control construction is carried out around the pile location to be constructed, and pressure grouting pipes and vacuum guide pipes are installed at intervals. Pressure grouting is performed in the pressure grouting pipe to control the grouting pressure and create a high-pressure zone. A vacuum pump is used to extract air from the cave, reducing the pressure around the vacuum guide pipe and creating a low-pressure zone. Stabilize the grouting pipe pressure and use a grout monitoring device to detect whether the grout has entered the vacuum guide pipe to determine whether the grouting guidance is complete. After the grouting guidance is completed and the grout has initially set, a secondary grouting is performed using a vacuum guide pipe until the grouting pressure is the same as that of the grouting pipe, at which point the secondary grouting is terminated.

[0016] As one implementation method, the termination conditions for grouting guidance are as follows: the vacuum guide pipe detects cement slurry; before the vacuum guide pipe detects cement slurry, the pressure of the pressure grouting pipe increases within a set range; after the vacuum guide pipe detects cement slurry, the pressure of the pressure grouting pipe decreases.

[0017] As one implementation method, during the pressure grouting construction process in the pressure grouting pipe, the grout pressure of the cement mortar is 1-3 MPa; the grouting pressure of the cement-water glass double-liquid fast-setting grout is 0.7-1.2 MPa.

[0018] As one implementation method, the secondary grouting process is terminated when the grout pressure of the cement mortar reaches 1.5 MPa; the grouting is terminated when the pressure of the cement-water glass double-liquid fast-setting grout reaches 0.8 MPa.

[0019] The beneficial effects of this invention are: This invention utilizes a pressure grouting pipe to inject cement grout or a two-component grout, creating a high-pressure zone around the grouting pipe. A vacuum pump extracts air from the karst cave, creating a low-pressure zone around the vacuum guide pipe. This generates a pressure difference around the proposed pile. Utilizing the physical property of liquid pressure driving flow, the injected grout is guided to form a cemented solidified body around the proposed pile in a predetermined direction. The pressure difference guides the grout flow, controlling its direction and forming a solidified area within a preset range. This method is effective for karst caves and other incompletely explored underground environments, achieving one-time karst cave treatment and resolving pile collapse during cast-in-place pile construction. It overcomes the drawback of uncontrollable grout volume in traditional gravity-flow grouting methods. It offers high pretreatment efficiency for karst caves in developed areas, significantly reducing the material required for gravity-flow grouting. Especially for pretreatment of cast-in-place piles in beaded or fully filled karst caves, rotary drilling and dry drilling can be used after treatment, saving time and costs.

[0020] Advantages of additional aspects of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0021] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0022] Figure 1 This is a plan view of the guided grouting structure applicable to karst cave cast-in-place piles according to an embodiment of the present invention; Figure 2This is a cross-sectional view of a guided grouting structure applicable to karst cave cast-in-place piles according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the pressure grouting pipe and vacuum guide pipe according to an embodiment of the present invention; Figure 4 This is a cross-sectional view of the pressure grouting pipe and vacuum guide pipe according to an embodiment of the present invention; Figure 5 This is a grouting process diagram of a guided grouting structure applicable to karst cave cast-in-place piles according to an embodiment of the present invention.

[0023] Among them, 1 is the pressure grouting pipe, 1-1 is the pressure grout outlet hole, 2 is the vacuum guide pipe, 2-2 is the first sub-pipe, 2-2 is the second sub-pipe, 2-3 is the third sub-pipe, 2-4 is the anti-blocking wire mesh, 3 is the proposed construction pile position, 4 is the vacuum pump, 5 is the grouting pressure detection device, 6 is the grout detection device, 7 is the soil layer, 8 is the rock layer, and 9 is the karst cave. Detailed Implementation

[0024] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0025] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0026] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0027] In this invention, terms such as "upper," "lower," "left," "right," "front," "back," "vertical," "horizontal," "side," and "bottom" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. These terms are used only to facilitate the description of the structural relationships of the various components or elements of this invention and do not specifically refer to any component or element in this invention. They should not be construed as limiting the invention.

[0028] In this invention, terms such as "fixed connection," "connected," and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0029] according to Figure 2 This invention provides a guided grouting structure suitable for karst cave cast-in-place piles, comprising: a plurality of pressure grouting pipes 1, a plurality of vacuum guide pipes 2, and a vacuum pump 4; the pressure grouting pipes 1 and vacuum guide pipes 2 are arranged at intervals around the intended pile location 3; as shown... Figure 3 and Figure 4 As shown in (a), each of the pressure grouting pipes 1 has a grouting hole 1-1 within the karst cave 9, and each of the vacuum guide pipes includes sub-pipes at different depths within the karst cave, such as... Figure 3 and Figure 4 As shown in (b), for example, each vacuum guide tube 2 includes a first sub-tube 2-1, a second sub-tube 2-2, and a third sub-tube 2-3; the bottom of the vacuum guide tube 2 is also provided with an anti-clogging wire mesh 2-4; the size and shape of the grouting holes in the pressure grouting pipe are determined by the size and shape of the karst cave. Figure 2 In the process, cave 9 is located within rock stratum 8. Pressure grouting pipe 1, vacuum guide pipe 2, and the proposed pile all pass through soil stratum 7 and rock stratum 8 to reach cave 9. The bottom of the proposed pile is lower than the lowest point of cave 9.

[0030] The pressure grouting pipe 1 is used to inject cement grout or dual-liquid grout to form a high-pressure zone around the pressure grouting pipe 1; the vacuum pump 4 is connected to the vacuum guide pipe 2 and is used to extract air from the karst cave 9, so that a low-pressure zone is formed around the vacuum guide pipe 2; a pressure difference is generated around the proposed pile, and the physical property of the liquid itself driving the flow is used to guide the injected grout to form a cemented solidified body around the proposed pile in a set direction.

[0031] according to Figure 1 The spacing arrangement of pressure grouting pipes and vacuum guide pipes around the proposed pile location; the number of pressure grouting pipes and vacuum guide pipes can be varied depending on the diameter of the proposed pile. For example, the following can be used: Figure 1 The four-hole arrangement shown in Figure (a) can be adopted. Figure 1 The six-hole arrangement shown in Figure (b) can also be adopted. Figure 1 The eight-hole arrangement shown in Figure (c) can be specifically configured by those skilled in the art according to the actual situation.

[0032] For every x increase in the diameter of the pile to be constructed, one pressure grouting pipe and one vacuum guide pipe are added; the distance between the pressure grouting pipe and the center of the pile to be constructed is set as d: d=(D+x) / 2; where D is the diameter of the pile to be constructed; x is a set constant.

[0033] For example, pressure grouting pipes and vacuum guide pipes are arranged at intervals around the pile location to be constructed. For piles with a diameter of 800mm, two sets of guide pipes are used (one pressure grouting pipe and one vacuum guide pipe in each set). For every 400mm increase in pile diameter, one more set of guide pipes is added. The distance from the pressure grouting pipe and vacuum guide pipe to the center of the pile is d=(D+400) / 2.

[0034] It should be noted that the spacing between the pressure grouting pipe and the vacuum guide pipe should be determined based on the construction survey results (the extent and size of the karst cave, the physical properties of the filling material, the groundwater conditions, etc.); the grouting pressure and vacuum pressure should be determined based on the grout mix ratio, the physical properties of the filling material, and the groundwater conditions, etc.

[0035] In this embodiment, the pressure grouting pipe 1 is also connected to the grouting pressure detection device 5. The grouting pressure detection device is used to detect the pressure inside the pressure grouting pipe until the grouting pressure is the same as the pressure inside the grouting pipe, at which point the grouting is terminated. The grouting pressure detection device here can be implemented using a grouting pressure gauge.

[0036] In this embodiment, the top of the vacuum guide tube 2 is also connected to a slurry monitoring device 6 (such as a slurry monitoring instrument), which is used to detect the slurry flow.

[0037] according to Figure 5 As shown, this embodiment of the invention provides a grouting method suitable for guided grouting structures in karst caves, comprising: Step 1: Conduct drilling control construction around the pile location to be constructed, and install pressure grouting pipes and vacuum guide pipes at intervals; Step 2: Perform pressure grouting construction in the pressure grouting pipe, and control the grouting pressure to form a high-pressure zone; Grouting pressure: The grouting pressure of cement mortar should not be too high, as excessive pressure will form a large solidified mass, which is not conducive to guiding control; The grouting pressure of cement-water glass double-liquid fast-setting grout should be 0.7-1.2 MPa, and the grouting pressure of the double-liquid should not be too low, as excessive pressure is not conducive to the formation of solidified mass.

[0038] Step 3: Use a vacuum pump to extract air from the cave and reduce the pressure around the vacuum guide tube to create a low-pressure area; Step 4: Stabilize the grouting pipe pressure and use a grout monitoring device to detect whether the grout has entered the vacuum guide pipe to determine whether the grouting guidance is complete. The termination conditions for the completion of grouting guidance are: the vacuum guide pipe detects cement grout; before the vacuum guide pipe detects cement grout, the pressure of the pressure grouting pipe is increased within the set range; after the vacuum guide pipe detects cement grout, the pressure of the pressure grouting pipe is reduced.

[0039] Step 5: After the grouting guidance is completed and the grout has initially set, perform secondary grouting using a vacuum guide pipe until the grouting pressure is the same as that of the grouting pipe, then terminate the secondary grouting. Secondary grouting pressure: For secondary grouting, which serves as a supplementary reinforcement, the grout pressure of the cement mortar should reach 1.5 MPa before termination; for cement-water glass double-liquid fast-setting grout, the grouting should be terminated when the pressure reaches 0.8 MPa.

[0040] In this embodiment, after determining the pile location, the specific conditions of the karst cave at the pile location are determined through construction survey; the arrangement of the pressure grouting pipe and vacuum guide pipe, the grout type, grouting pressure, and other technical parameters are determined; according to the determined technical parameters, drilling is carried out to install the pressure grouting pipe and vacuum guide pipe; pressure grouting and vacuum pump operation are performed to guide the grout to form a cemented and solidified body around the pile; after the guidance construction is completed, grouting is stopped; secondary pressurized grouting is carried out using the vacuum guide pipe, with the grouting pressure based on the grouting pressure of the first grouting; after the grout has gained strength, pile foundation construction is carried out to further verify the grouting effect, adjust and optimize technical parameters, and improve the effectiveness of subsequent pretreatment grouting.

[0041] The guided grouting structure and grouting method of this invention, applicable to the construction of cast-in-place piles in karst caves, are highly reliable and effectively utilize the physical properties of the grout. By artificially creating a pressure difference for guidance, it solves the drawback of uncontrollable grouting volume in traditional gravity-flow grouting methods. It has high pretreatment efficiency for karst caves in karst development areas. At the same time, based on the water loss velocity test, it can pretreatment of the foundation for different strata that are difficult to drill holes in (e.g., silt layer, sand layer, breccia layer, etc.). It can effectively address the underground environment of various strata in karst caves that are not fully explored, thereby meeting the construction conditions of rotary-drilled cast-in-place piles, saving construction time, reducing costs, and being environmentally friendly.

[0042] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A guided grouting structure suitable for karst cave cast-in-place piles, characterized in that, include: Several pressure grouting pipes, several vacuum guide pipes, and a vacuum pump; The pressure grouting pipes and vacuum guide pipes are arranged at intervals around the pile locations to be constructed. Each of the pressure grouting pipes has grout holes opened within the karst cave area, and each of the vacuum guide pipes includes sub-pipes at different depths within the karst cave area; The pressure grouting pipe is used to inject cement grout or dual-liquid grout to form a high-pressure zone around the pressure grouting pipe; the vacuum pump is connected to the vacuum guide pipe to extract air from the karst cave, so that a low-pressure zone is formed around the vacuum guide pipe; a pressure difference is generated around the proposed pile, and the physical property of the liquid itself driving the flow is used to guide the injected grout to form a cemented solidified body around the proposed pile in a set direction.

2. The guided grouting structure for karst cave cast-in-place piles as described in claim 1, characterized in that, The pressure grouting pipe is also connected to a grouting pressure detection device, which is used to detect the pressure inside the pressure grouting pipe until the grouting pressure is the same as the pressure inside the grouting pipe, at which point the grouting is terminated.

3. The guided grouting structure for karst cave cast-in-place piles as described in claim 1, characterized in that, The top of the vacuum guide tube is also connected to a slurry monitoring device, which is used to detect the slurry flow.

4. The guided grouting structure for karst cave cast-in-place piles as described in claim 1, characterized in that, The bottom of the vacuum guide tube is also equipped with an anti-clogging wire mesh.

5. The guided grouting structure for karst cave cast-in-place piles as described in claim 1, characterized in that, For every x increase in the diameter of the pile to be constructed, one pressure grouting pipe and one vacuum guide pipe are added; the distance between the pressure grouting pipe and the center of the pile to be constructed is set as d: d=(D+x) / 2; where D is the diameter of the pile to be constructed; x is a set constant.

6. The guided grouting structure for karst cave cast-in-place piles as described in claim 1, characterized in that, The size and shape of the grouting holes in the pressure grouting pipe are determined by the size and shape of the karst cave.

7. A grouting method based on a guided grouting structure suitable for karst cave cast-in-place piles as described in any one of claims 1-6, characterized in that, include: Drilling control construction is carried out around the pile location to be constructed, and pressure grouting pipes and vacuum guide pipes are installed at intervals. Pressure grouting is performed in the pressure grouting pipe to control the grouting pressure and create a high-pressure zone. A vacuum pump is used to extract air from the cave, reducing the pressure around the vacuum guide pipe and creating a low-pressure zone. Stabilize the grouting pipe pressure and use a grout monitoring device to detect whether the grout has entered the vacuum guide pipe to determine whether the grouting guidance is complete. After the grouting guidance is completed and the grout has initially set, a secondary grouting is performed using a vacuum guide pipe until the grouting pressure is the same as that of the grouting pipe, at which point the secondary grouting is terminated.

8. The grouting method as described in claim 7, characterized in that, Termination conditions for grouting guidance: Cement slurry is detected by the vacuum guide pipe; before the cement slurry is detected by the vacuum guide pipe, the pressure of the pressure grouting pipe is increased within the set range; after the cement slurry is detected by the vacuum guide pipe, the pressure of the pressure grouting pipe is reduced.

9. The grouting method as described in claim 7, characterized in that, During the pressure grouting process using pressure grouting pipes, the grout pressure of cement mortar is 1-3 MPa; the grouting pressure of cement-water glass double-liquid fast-setting grout is 0.7-1.2 MPa.

10. The grouting method as described in claim 7, characterized in that, During the secondary grouting process, the cement mortar grout pressure was stopped when it reached 1.5 MPa; the cement-water glass double-liquid fast-setting grout pressure was stopped when it reached 0.8 MPa.

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