Karst region adaptive modular expansion pile device and construction method thereof

Abstract

The application discloses a kind of karst region adaptability modular expansion pile device and its construction method, belong to pile foundation engineering technical field, the device includes by a plurality of modular pile section splicing and is fixed by connecting piece and is formed pile body, expansion chamber, grouting system, valve control and pressure monitoring system and monitoring assembly are arranged in the pile body, the bottom end of pile body is fixed with bottom disc, and the bottom surface of bottom disc is provided with a plurality of drill bits, and the inner cavity of pile body is provided with mud filling pipeline along the axial direction.The grouting system includes the grouting pipeline arranged along the inside of pile body, and the grouting port is arranged in communication between the grouting pipeline and expansion chamber, and the switch valve is arranged on the grouting port branch, and the pressure monitoring unit is arranged on the grouting pipeline, and the monitoring assembly includes multidimensional sensor.The application can simplify construction process, reduce material consumption, improve the adaptability, reliability and safety and stability of pile foundation construction in karst region.

Description

Technical Field

[0001] This invention relates to the field of pile foundation engineering technology, and in particular to a modular expansion pile device adapted for karst areas and its construction method. Background Technology

[0002] Karst areas have complex geological conditions, often containing sinkholes of varying sizes, fracture zones, and weak interlayers, as well as abundant groundwater with significant water level fluctuations. When constructing pile foundations in such areas, problems such as pile tip or side entry into sinkholes, partial pile suspension, insufficient bearing capacity, and uneven settlement can easily occur, potentially leading to pile foundation failure in severe cases.

[0003] In existing technologies, to improve the adaptability of pile foundation construction in karst areas, measures such as increasing pile diameter, deepening pile length, full-hole grouting, installing casing, or locally enlarging the borehole are commonly adopted. While these methods can improve foundation stability to some extent, they generally suffer from problems such as numerous construction procedures, long cycles, high material consumption, and insufficient adaptability to the actual location of karst caves. In particular, when the actual location of karst caves or weak soil layers does not match the pre-designed treatment location, existing fixed-location expansion bladders or grouting hole solutions often fail to achieve the desired reinforcement effect.

[0004] On the other hand, traditional construction methods rely heavily on construction experience to determine the location of karst caves, lacking real-time identification and feedback mechanisms coupled with the drilling process, making it difficult to implement timely and accurate targeted treatment. Simultaneously, monitoring of pile verticality, joint deformation, and settlement during construction is often insufficient, affecting pile quality control and subsequent safety. Therefore, it is necessary to provide an integrated pile foundation device and construction method that can adapt to complex karst geological formations, balance construction monitoring and quality control, and enable selective filling of karst caves and localized pile reinforcement. Summary of the Invention

[0005] The purpose of this invention is to provide an adaptive modular expansion pile device and its construction method for karst areas, in order to solve the problems of poor construction adaptability, inaccurate treatment location, high construction cost and insufficient quality control in the prior art. It enables selective filling of karst caves or weak soil layers in complex karst strata and reinforcement of the pile body, thereby improving the safety, reliability and economy of pile foundation construction.

[0006] To achieve the above objectives, the present invention provides an adaptive modular expansion pile device for karst areas, comprising a pile body, a grouting system, a valve control and pressure monitoring system, and monitoring components. The pile body is composed of several hollow cylindrical modular pile sections sequentially spliced ​​along a central axis, with adjacent modular pile sections fixedly connected by connectors. At least one expansion chamber is provided in the inner cavity of each modular pile section, and a reserved opening corresponding to the position of the expansion chamber is opened on the side wall of the pile body. A base plate is fixed at the bottom end of the pile body, and several drill bits are provided on the lower surface of the base plate. A mud-filling pipe is arranged axially in the inner cavity of the pile body, and the lower end of the mud-filling pipe extends above the base plate to fill the gaps left after the expansion chamber expands. The grouting system is connected to the expansion chamber. The grouting system includes a grouting pipeline arranged axially inside the pile body. A grouting port is provided between the grouting pipeline and the expansion chamber. The upper end of the grouting pipeline is connected to a grouting pump. The valve control and pressure monitoring system includes a switching valve respectively arranged on the branch leading to each of the grouting ports, a pressure monitoring unit arranged on the grouting pipeline, and a one-way valve arranged at the grouting port or adjacent branch. The monitoring components include multi-dimensional sensors.

[0007] Preferably, the connector is a flange plate, and adjacent modular pile sections are fixedly connected to the bolt assembly through the flange plate.

[0008] Preferably, the outer surface of the modular pile section is provided with an anti-corrosion coating with a thickness of not less than 200 μm, and the inner surface is provided with an inner anti-rust coating with a thickness of not less than 100 μm; the outer wall of the modular pile section in the highly corrosive area is also provided with a sacrificial zinc anode.

[0009] Preferably, each modular pile section has at least two expansion chambers along the axial direction, located at the middle and near the bottom of the modular pile section, respectively; the outer diameter of the expansion chamber after grouting expansion is 1.2-1.5 times the outer diameter of the corresponding modular pile section.

[0010] Preferably, the expansion chamber is made of reinforced polyurethane or high-strength rubber, the wall thickness of the expansion chamber is 4-6 mm, the outer surface is provided with a serrated texture, and is covered with a polyurea coating with a thickness of not less than 1 mm.

[0011] Preferably, the grouting pipeline is a seamless steel pipe connected by a threaded joint, and the grouting pipeline is fixed to the inner wall of each modular pile section by several steel clamps at predetermined intervals; the grouting port is a stainless steel structure with a diameter of 10-30mm, and is equipped with a one-way valve and an O-ring seal inside.

[0012] Preferably, the multidimensional sensor is installed at the connection point of adjacent modular pile sections or at a position flush with the expansion chamber, for synchronously monitoring pile inclination angle, axial expansion displacement, radial deformation and grouting pressure parameters.

[0013] Preferably, a screen is provided at the lower end of the mud filling pipe to prevent mud and sand from clogging the mud filling pipe during the drilling process.

[0014] This invention also provides a construction method for a modular expansion pile device adapted for karst areas, comprising the following steps: S1. Geological survey and scheme design: Conduct geological surveys of engineering sites in karst areas, and determine the pile length, pile diameter, and the height and number of expansion chambers in the pile body based on the distribution of karst caves, soil structure and groundwater level. S2. Modular pile section prefabrication and testing: Modular pile sections are prefabricated in the factory, and expansion chambers, grouting systems and mud filling pipelines are arranged inside the modular pile sections. Strength, sealing and corrosion resistance are tested. S3. On-site assembly and drilling: Modular pile sections are connected sequentially at the construction site to form a pile body of the target length. The pile body is erected and aligned with the pile position. The drilling rig drives the drilling tool to drill, so that the pile body gradually enters the formation as drilling progresses. At the same time, the drilling monitoring mechanism continuously monitors the torque or drilling speed. S4. Karst Cave Identification and Selective Grouting Expansion: When monitoring results indicate that the torque or drilling speed at a certain depth reaches a preset change threshold, the depth is determined to be a karst cave or a weak soil layer. The switch valve at the modular pile section corresponding to that depth is opened, and grout is injected into the corresponding expansion chamber through the grouting pump and grouting pipeline. The grouting pressure is monitored by the pressure monitoring unit to ensure the filling of the karst cave or weak soil layer and the reinforcement of the pile body. S5. Pile Construction: After the grouting expansion at each depth is completed and cured, a steel cage is placed inside the pile body, and concrete is poured until the design elevation is reached. The pile is then cured to form a finished pile. S6. Monitoring and Acceptance: During the construction and curing stages, multi-dimensional sensors are used to monitor the pile inclination angle, axial expansion displacement, radial deformation, and grouting pressure parameters. In the split-type implementation, the pile verticality, relative displacement and settlement at the connection points and expansion chambers can be monitored separately using inclinometers and extensometers. After construction, the pile foundation quality is evaluated by combining the results of acoustic wave detection and static load tests.

[0015] Preferably, in S4, when the pressure monitoring unit shows that the grouting pressure is maintained stably within the preset range for a predetermined time, it is determined that the corresponding karst cave or weak soil layer has been fully filled, grouting is stopped and the switch valve is closed; when the grouting pressure rises rapidly to the upper limit value, it is determined that there is no karst cave to be filled at that depth or that the expansion chamber has been fully expanded, grouting is ended and the switch valve is closed.

[0016] Therefore, the beneficial effects of the present invention using the above-mentioned karst region-adaptive modular expansion pile device and its construction method are as follows: (1) By combining modular pile sections with expansion chambers arranged in multiple locations, selective grouting expansion can be achieved for karst caves and soft soil layers of different depths, reducing material waste caused by full-hole grouting; (2) Through the coordinated action of the drilling detection mechanism, the switching valve and the pressure monitoring unit, identification, filling and reinforcement can be integrated into a single drilling process, reducing repetitive procedures; (3) By setting up mud filling pipelines, the residual gaps after the expansion chamber is expanded can be filled to improve the compactness of the pile; (4) By setting up multi-dimensional sensors or their split monitoring units, the posture and deformation of the pile body can be monitored during the construction and curing stages, thereby improving the level of construction quality control; (5) Modular pile sections are easy to prefabricate in the factory, transport and assemble on site. They can be flexibly combined according to project requirements and have good engineering applicability and economy.

[0017] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0018] Figure 1 This is a front view of the overall structure of an embodiment of a modular expansion pile device adapted for karst areas according to the present invention; Figure 2 This is a three-dimensional structural schematic diagram of an embodiment of a modular expansion pile device adapted for karst areas according to the present invention; Figure 3 This is a schematic cross-sectional view of the grouting system in an embodiment of the present invention; Figure 4 This is a schematic diagram of a partial structure of the mud-filling pipe and screen according to an embodiment of the present invention; Figure 5 This is a schematic diagram of a scenario in an embodiment of the present invention; Figure 6 This is a schematic diagram illustrating the usage state in an embodiment of the present invention.

[0019] Figure Labels 1. Pile body; 2. One-way valve; 3. Multi-dimensional sensor; 4. Mud filling pipeline; 41. Screen; 5. Flange plate; 6. Expansion chamber; 7. Chassis; 71. Drill bit; 8. Grouting pipeline. Detailed Implementation

[0020] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0021] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0022] Example 1: like Figures 1 to 4 As shown, this embodiment provides a modular expansion pile device adapted for karst areas, including a pile body 1, a one-way valve 2, a multi-dimensional sensor 3, a mud filling pipeline 4, a flange plate 5, an expansion chamber 6, a base plate 7, and a grouting pipeline 8. The pile body 1 is composed of several hollow cylindrical modular pile sections sequentially spliced ​​along the central axis. Adjacent modular pile sections are fixedly connected by flange plates 5 and bolt assemblies to achieve modular expansion of the device length, facilitating segmented transportation and on-site assembly.

[0023] The modular pile section can be made of high-strength steel or reinforced concrete. The high-strength steel can be Q345B or Q460, and the reinforced concrete strength grade is preferably not lower than C40. The outer surface of the modular pile section is coated with an anti-corrosion coating, and the inner surface is coated with an internal anti-rust coating. In highly corrosive areas, sacrificial zinc anodes can also be installed on the outer wall to improve the durability of the device in complex underground environments.

[0024] At least one expansion chamber 6 is provided within each modular pile section, preferably two expansion chambers 6 are provided along the axial direction, located at the middle and near the bottom end of the modular pile section, respectively. The sidewall of the pile body 1 has pre-reserved openings at the corresponding positions of the expansion chambers 6, so that the expansion chambers 6 can expand outwards towards the karst caves or weak soil layers after grouting, forming a locally enlarged diameter reinforcement structure. The outer diameter of the expanded chamber 6 after expansion is preferably 1.2-1.5 times the outer diameter of the corresponding modular pile section. The expansion chamber 6 can be made of reinforced polyurethane or high-strength rubber, with a wall thickness preferably of 4-6 mm. The outer surface can be provided with a serrated texture and covered with a polyurea coating to improve its bonding ability and wear resistance with the surrounding solidified grout and strata.

[0025] like Figure 3 and Figure 4As shown, the grouting system includes grouting pipes 8 arranged axially along the interior of the pile body 1. The grouting pipes 8 are made of seamless steel pipes and can be connected in sections via threaded joints, and fixed to the inner wall of each modular pile section by steel clamps. The grouting pipes 8 are connected to each expansion chamber 6 via grouting ports, which are preferably made of stainless steel and equipped with one-way valves 2 and O-ring seals to prevent grout backflow and ensure system sealing. The upper end of the grouting pipes 8 is connected to an external grouting pump to supply grout to the corresponding expansion chamber 6. For the sake of simplicity in the drawings, drilling tools, drilling rigs, grouting pumps, pressure monitoring units, and some switching valves may not be individually numbered in the figures.

[0026] like Figure 4 and Figure 5 As shown, a mud-filling pipe 4 is also provided axially within the inner cavity of the pile body 1. The lower end of the mud-filling pipe 4 extends above the base plate 7, and a screen 41 is installed at its end. The mud-filling pipe 4 is used to fill any remaining gaps after the expansion chamber 6 expands, thereby further improving the compactness and stress stability of the pile. The screen 41 is used to prevent mud and sand from entering the mud-filling pipe 4 and causing blockage during drilling.

[0027] like Figures 1 to 4 As shown, a base plate 7 is fixedly installed at the bottom of the pile body 1, and several drill bits 71 are provided on the lower surface of the base plate 7. During construction, the drilling rig drives the drilling tools, base plate 7, and drill bits 71 downward to drill, so that the pile body 1 gradually enters the stratum. During the drilling process, the drilling detection mechanism can monitor parameters such as torque and drilling speed in real time to help determine whether it has entered a karst cave or a weak soil layer.

[0028] The multi-dimensional sensor 3 is installed at the connection point of adjacent modular pile sections or at a position flush with the expansion chamber 6, and is used to synchronously monitor the pile inclination angle, axial expansion displacement, radial deformation, and grouting pressure parameters. In one embodiment, the multi-dimensional sensor 3 is an integrated sensor; in another embodiment, the multi-dimensional sensor 3 can be composed of multiple separate monitoring elements, such as inclinometers, extensometers, and other corresponding monitoring elements, to achieve separate monitoring of different parameters.

[0029] The construction method for the above-mentioned modular expansion pile device adapted to karst areas includes the following steps: S1. Conduct geological surveys of engineering sites in karst areas to obtain information such as the distribution of karst caves, soil structure, and groundwater level, and determine the pile length, pile diameter, and the height and number of expansion chambers 6 in the pile body 1 accordingly. S2. Prefabricate modular pile sections in the factory, and arrange expansion chambers 6, grouting pipelines 8 and mud filling pipelines 4 in the modular pile sections, and test their strength, sealing and corrosion resistance. S3. Connect the modular pile sections sequentially according to the design order at the construction site to form the pile body 1 of the target length, and erect it to align with the designed pile position. Then, use a drilling rig to drive the drilling tool to drill into the stratum. S4. When the drilling detection mechanism detects a significant change in torque or drilling speed, it determines that there may be a karst cave or weak soil layer at the corresponding depth. The corresponding branch valve is opened, and grout is injected into the corresponding expansion chamber 6 via the grouting pump and grouting pipeline 8. Figure 6 As shown, the grouting pressure change is monitored by the pressure monitoring unit; when the grouting pressure is kept stable within the preset range for a predetermined time, it can be determined that the position has been fully filled; when the grouting pressure rises rapidly to the upper limit value, it can be determined that there are no large gaps that need to be filled further, or that the expansion chamber 6 has been fully expanded. S5. After the grouting expansion at each depth is completed and cured, a steel cage is placed inside the pile body 1, and concrete is poured until the design elevation is reached. The pile is then cured to form a finished pile. S6. During the construction and curing stages, the pile posture and deformation are monitored by multi-dimensional sensor 3 or its split monitoring element; after construction is completed, the pile foundation quality is comprehensively evaluated by combining the results of acoustic wave detection and static load test.

[0030] Therefore, the present invention adopts the above-mentioned modular expansion pile device and construction method adapted to karst areas, which solves the problems of poor construction adaptability, inaccurate treatment location, high construction cost and insufficient quality control in the prior art. It realizes selective filling of karst caves or weak soil layers in complex karst strata and pile body reinforcement, and improves the safety, reliability and economy of pile foundation construction.

[0031] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A modular expansion pile device adapted for karst areas, characterized in that: The system includes a pile body, a grouting system, a valve control and pressure monitoring system, and monitoring components. The pile body is composed of several hollow cylindrical modular pile sections sequentially spliced ​​along the central axis, with adjacent modular pile sections fixedly connected by connectors. Each modular pile section has at least one expansion chamber within its inner cavity. The sidewall of the pile body has a reserved opening corresponding to the position of the expansion chamber. A base plate is fixed to the bottom end of the pile body, and several drill bits are provided on the lower surface of the base plate. A mud-filling pipe is axially arranged within the inner cavity of the pile body, with its lower end extending above the base plate to fill any gaps left after the expansion chambers expand. The grouting system is connected to the expansion chamber. The grouting system includes a grouting pipeline arranged axially inside the pile body. A grouting port is provided between the grouting pipeline and the expansion chamber. The upper end of the grouting pipeline is connected to a grouting pump. The valve control and pressure monitoring system includes a switching valve respectively arranged on the branch leading to each of the grouting ports, a pressure monitoring unit arranged on the grouting pipeline, and a one-way valve arranged at the grouting port or adjacent branch. The monitoring components include multi-dimensional sensors.

2. The modular expansion pile device adapted for karst areas according to claim 1, characterized in that: The connector is a flange plate, and adjacent modular pile sections are fixedly connected to each other by the flange plate and bolt assembly.

3. The modular expansion pile device adapted for karst areas according to claim 1, characterized in that: The outer surface of the modular pile section is provided with an anti-corrosion coating with a thickness of not less than 200 μm, and the inner surface is provided with an inner anti-rust coating with a thickness of not less than 100 μm; the outer wall of the modular pile section in the highly corrosive area is also provided with a sacrificial zinc anode.

4. The modular expansion pile device adapted for karst areas according to claim 1, characterized in that: Each modular pile section has at least two expansion chambers along the axial direction, located at the middle and near the bottom of the modular pile section, respectively; the outer diameter of the expansion chamber after grouting expansion is 1.2-1.5 times the outer diameter of the corresponding modular pile section.

5. A modular expansion pile device adapted for karst areas according to claim 1, characterized in that: The expansion chamber is made of reinforced polyurethane or high-strength rubber, with a wall thickness of 4-6 mm, a serrated texture on the outer surface, and a polyurea coating with a thickness of not less than 1 mm.

6. The modular expansion pile device adapted for karst areas according to claim 1, characterized in that: The grouting pipeline is a seamless steel pipe connected by threaded joints. The grouting pipeline is fixed to the inner wall of each modular pile section by several steel clamps at predetermined intervals. The grouting port is made of stainless steel with a diameter of 10-30mm and is equipped with a one-way valve and an O-ring seal inside.

7. The modular expansion pile device adapted for karst areas according to claim 1, characterized in that: The multidimensional sensor is installed at the connection point of adjacent modular pile sections or at a position flush with the expansion chamber, and is used to synchronously monitor the pile inclination angle, axial expansion and contraction displacement, radial deformation and grouting pressure parameters.

8. A modular expansion pile device adapted for karst areas according to claim 1, characterized in that: The lower end of the mud filling pipe is equipped with a screen to prevent mud and sand from clogging the mud filling pipe during the drilling process.

9. A construction method for a modular expansion pile device adapted for karst areas as described in any one of claims 1-8, characterized in that: Includes the following steps: S1. Geological survey and scheme design: Conduct geological surveys of engineering sites in karst areas, and determine the pile length, pile diameter, and the height and number of expansion chambers in the pile body based on the distribution of karst caves, soil structure and groundwater level. S2. Modular pile section prefabrication and testing: Modular pile sections are prefabricated in the factory, and expansion chambers, grouting systems and mud filling pipelines are arranged inside the modular pile sections. Strength, sealing and corrosion resistance are tested. S3. On-site assembly and drilling: Modular pile sections are connected sequentially at the construction site to form a pile body of the target length. The pile body is erected and aligned with the pile position. The drilling rig drives the drilling tool to drill, so that the pile body gradually enters the formation as drilling progresses. At the same time, the drilling monitoring mechanism continuously monitors the torque or drilling speed. S4. Karst Cave Identification and Selective Grouting Expansion: When monitoring results indicate that the torque or drilling speed at a certain depth reaches a preset change threshold, the depth is determined to be a karst cave or a weak soil layer. The switch valve at the modular pile section corresponding to that depth is opened, and grout is injected into the corresponding expansion chamber through the grouting pump and grouting pipeline. The grouting pressure is monitored by the pressure monitoring unit to ensure the filling of the karst cave or weak soil layer and the reinforcement of the pile body. S5. Pile Construction: After the grouting expansion at each depth is completed and cured, a steel cage is placed inside the pile body, and concrete is poured until the design elevation is reached. The pile is then cured to form a finished pile. S6. Monitoring and Acceptance: During the construction and curing stages, multi-dimensional sensors are used to monitor the pile inclination angle, axial expansion displacement, radial deformation, and grouting pressure parameters. In the split-type implementation, the pile verticality, relative displacement and settlement at the connection points and expansion chambers can be monitored separately using inclinometers and extensometers. After construction, the pile foundation quality is evaluated by combining the results of acoustic wave detection and static load tests.

10. The construction method of a modular expansion pile device adapted for karst areas according to claim 9, characterized in that: In S4, when the pressure monitoring unit shows that the grouting pressure is maintained stably within the preset range for a predetermined time, it is determined that the corresponding karst cave or weak soil layer has been fully filled, grouting is stopped and the switch valve is closed; when the grouting pressure rises rapidly to the upper limit value, it is determined that there is no karst cave to be filled at that depth or the expansion chamber has been fully expanded, grouting is ended and the switch valve is closed.

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