Alternating positive and negative pressure loading foundation treatment assembly unit, system and method

Abstract

The application relates to the technical field of foundation treatment and soft soil reinforcement engineering, in particular to a positive-negative pressure alternating loading foundation treatment combined unit, a system and a method, the combined unit comprises a vacuum film, the vacuum film is provided with a first area and a second area surrounding the first area; the first area is provided with at least two pipelines, the pipelines are communicated with each other through sealing interfaces; the sealing interfaces are communicated with drainage plates penetrating through the vacuum film, and the sealing interfaces are sealingly connected with the joints of the vacuum film; the ends of the pipelines away from the sealing interfaces are provided with sealing joints; and the second area is provided with an adhesive layer surrounding the first area. The scheme provided by the application can realize the unification of structural modularization and sealing reliability through vacuum film partition integration of pipelines, drainage plates and surrounding adhesive layers, provide a stable carrier for positive-negative pressure alternating loading, and is convenient for rapid installation and independent sealing.

Description

Technical Field

[0001] This application relates to the field of foundation treatment and soft soil reinforcement engineering technology, and in particular to a combined unit, system and method for foundation treatment with alternating positive and negative pressure loading. Background Technology

[0002] Foundations in soft soil areas typically suffer from high porosity, high compressibility, slow consolidation, and low strength. Traditional vacuum preloading involves laying a sealing membrane on the foundation and then applying a vacuum, using atmospheric pressure to generate additional stress and accelerate foundation consolidation. However, existing vacuum preloading processes are prone to overlapping gaps when laying large areas of membrane, leading to air leakage. Repairing leaks is difficult and negatively impacts both the vacuum level and the reinforcement effect. Secondly, during prolonged vacuum suction, a mud cake layer easily forms on the outer surface of the drainage board, reducing permeability and causing poor drainage. Furthermore, vacuum preloading only uses negative pressure, limiting the consolidation rate and making it difficult to further increase the strength gain. Summary of the Invention

[0003] One of the purposes of this application is to provide a combined unit for alternating positive and negative pressure loading of foundation treatment, which overcomes the shortcomings of the prior art. Through vacuum membrane integrated pipeline, drainage board and adhesive layer, it achieves the unity of structural modularity and sealing reliability, provides a stable carrier for alternating positive and negative pressure loading, and facilitates rapid installation and independent sealing.

[0004] The second objective of this application is to provide a positive and negative pressure alternating loading foundation treatment system, which can form an overall sealing layer covering the foundation to be preloaded through staggered first and second subsystems. Combined with the coordinated control of vacuum and pressurization systems, it realizes positive and negative pressure alternating loading treatment of the foundation, which has the advantage of improving the foundation treatment efficiency.

[0005] The third objective of this application is to provide a foundation treatment method using alternating positive and negative pressure loading. By using alternating positive and negative pressure loading and dynamically adjusting parameters based on real-time monitoring data, the drainage of pore water and the consolidation rate of the soil can be accelerated, significantly improving the bearing capacity of the foundation, effectively controlling settlement, and shortening the construction cycle. This method is particularly suitable for complex geological conditions.

[0006] One of the objectives of this application is achieved through the following technical solution: A combined unit for alternating positive and negative pressure loading of foundation treatment is provided, including a vacuum membrane. The vacuum membrane has a first region and a second region surrounding the first region. The first region has at least two pipes, which are interconnected through a sealed interface. The sealed interface is connected to a drainage board that penetrates the vacuum membrane, and the joint between the sealed interface and the vacuum membrane is sealed. A sealing joint is provided at the end of each pipe away from the sealed interface. The second region has an adhesive layer surrounding the first region.

[0007] In some embodiments, the vacuum membrane includes a double-layer sealing membrane, which is thermoplastically sealed to form an installation cavity and a fitting portion, the fitting portion surrounding the installation cavity; wherein the installation cavity is the first region and the fitting portion is the second region.

[0008] In some implementations, the first region is a polygonal region, and the pipeline is laid out along the direction from the center to the vertex of the first region.

[0009] In some embodiments, the adhesive layer is a cold-applied self-adhesive tape.

[0010] In some embodiments, the pipe diameter is 50mm to 100mm; the drainage board has an opening ratio of 5% to 15%, an opening diameter of 5mm to 10mm, and the outer surface of the drainage board is covered with non-woven fabric; the sealing interface is a quick-connect connector.

[0011] The second objective of this application is achieved through the following technical solution: A combined positive and negative pressure alternating loading foundation treatment system is provided, including a first subsystem, a second subsystem, a vacuum system, a pressurization system and a detection system. The first subsystem and the second subsystem are respectively connected to the vacuum system and the pressurization system through valve control devices. The first subsystem and the second subsystem each include multiple positive and negative pressure alternating loading foundation treatment combination units. The combination units of the first subsystem are interconnected through pipelines, and the combination units of the second subsystem are interconnected through pipelines. The combination units of the first subsystem and the combination units of the second subsystem are arranged alternately on the surface of the foundation to be preloaded, and adjacent combination units are stacked crosswise and sealed together by an adhesive layer to form a sealing layer covering the foundation to be preloaded.

[0012] In some embodiments, the detection system includes a pore water pressure gauge, a settlement plate, and a vacuum gauge, and is used to collect data on the degree of consolidation of the foundation, settlement rate, and positive and negative pressure parameters.

[0013] The third objective of this application is achieved through the following technical solution: A combined method for alternating positive and negative pressure foundation treatment is provided, employing the aforementioned alternating positive and negative pressure foundation treatment system, including the following steps: S1. Install the detection system on the foundation to be preloaded, then install the combined units of the first and second subsystems in an alternating manner, and then install the vacuum system and pressurization system; S2. Start the vacuum system and simultaneously perform vacuum treatment on the first and second subsystems, continuing the treatment until the foundation consolidation degree meets the stage requirements. S3. The first subsystem maintains a vacuum, and the pressurization system is started to pressurize the second subsystem while running for the first set time. S4. Start the pressurization system to pressurize the first subsystem, restore the second subsystem to vacuum, and run for the first set time at the same time; S5. Repeat S3 and S4 to form a cyclic load; S6. Adjust the first set duration, the output power of the vacuum system, and the output power of the pressurization system according to the monitoring data of the detection system until the foundation consolidation degree reaches the design requirements.

[0014] In some embodiments, the foundation consolidation degree reaching the stage requirement specifically means that the foundation consolidation degree reaches 70%; the positive pressure range of the pressurization treatment is +20kPa to +60kPa, and the negative pressure range of the vacuum treatment is -60kPa to -80kPa; the first set duration is 7 days to 30 days.

[0015] In some implementations, the foundation consolidation degree meeting the design requirements specifically means that the characteristic value of the foundation bearing capacity is not less than 80 kPa and the settlement is not greater than 50 cm.

[0016] Compared with the prior art, the technical solution provided in this application has the following beneficial effects: (1) Through modular prefabrication and self-sealing structure design, standardized factory production and rapid on-site installation are realized. With the help of multiple types of pipelines and sealing interfaces, the problems of difficult sealing of large-area membranes, low construction efficiency and poor drainage in traditional foundation treatment are solved, ensuring the smoothness of drainage channels and overall sealing. When local faults such as air leakage occur, the corresponding combination unit can be quickly located and disassembled for replacement or repair, ensuring the continuity of foundation treatment and reinforcement effect.

[0017] (2) The first and second subsystems are independently controlled and staggered, and combined with positive and negative pressure control devices and monitoring and adjustment units, to achieve precise switching of positive and negative pressure conditions and dynamic adjustment of parameters, effectively peel off the mud skin on the outside of the drainage board to restore permeability, solve the problem of low reinforcement efficiency and easy blockage of drainage board caused by traditional vacuum preloading single loading, and significantly improve the foundation reinforcement effect.

[0018] (3) By combining vacuum preloading and alternating positive and negative pressure in a step-by-step loading process, the cyclic load is used to change the soil stress path, promote soil structure reorganization and drainage consolidation, and adjust the positive and negative pressure parameters and cycle with real-time monitoring data. This solves the problems of slow consolidation rate and difficult settlement control in traditional vacuum preloading, effectively shortens the foundation treatment cycle, improves the foundation bearing capacity and controls the final settlement. Attached Figure Description

[0019] The above and other objects, features and advantages of this application will become more apparent from the more detailed description of exemplary embodiments thereof in conjunction with the accompanying drawings, wherein the same reference numerals generally represent the same components in the exemplary embodiments thereof.

[0020] Figure 1 This is a front view of the alternating positive and negative pressure loading foundation treatment unit shown in the embodiments of this application; Figure 2 yes Figure 1 A magnified top view of point A in the middle; Figure 3 yes Figure 1 Enlarged view from below at point A; Figure 4 This is a side view of the alternating positive and negative pressure loading foundation treatment unit shown in the embodiments of this application; Figure 5 This is another structural schematic diagram of the alternating positive and negative pressure loading foundation treatment combined unit shown in the embodiments of this application; Figure 6 This is another structural schematic diagram of the alternating positive and negative pressure loading foundation treatment combined unit shown in the embodiments of this application; Figure 7 This is another structural schematic diagram of the alternating positive and negative pressure loading foundation treatment combined unit shown in the embodiments of this application; Figure 8 This is a schematic diagram of the structure of the alternating positive and negative pressure loading foundation treatment system shown in the embodiments of this application.

[0021] Figure label: 1. Vacuum membrane; 11. First zone; 12. Second zone; 2. Piping; 3. Sealing interface; 4. Drainage board; 5. Sealing joint; 6. Adhesive layer; 100. First subsystem; 200. Second subsystem; 300. Vacuum system; 400. Pressurization system. Detailed Implementation

[0022] Preferred embodiments of the present application will now be described in more detail with reference to the accompanying drawings. While preferred embodiments of the present application are shown in the drawings, it should be understood that the present application may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make the present application more thorough and complete, and to fully convey the scope of the present application to those skilled in the art.

[0023] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used in this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any or all possible combinations of one or more of the associated listed items.

[0024] It should be understood that although the terms "first," "second," "third," etc., may be used in this application to describe various information, this information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0025] In existing technologies, vacuum preloading is commonly used for soft soil foundation treatment, which accelerates consolidation by laying a sealing membrane and applying vacuum. However, during large-area construction, air leakage is prone to occur at the membrane overlaps, making repairs difficult and leading to a decrease in vacuum levels. Furthermore, after prolonged vacuum treatment, a mud cake layer forms on the surface of the drainage board 4, reducing permeability and obstructing drainage. In addition, vacuum preloading only uses negative pressure for foundation consolidation, but with reduced permeability of the drainage board 4, the consolidation rate decreases over time under single negative pressure, making it difficult to further increase the rate of foundation strength growth.

[0026] To address the aforementioned issues, this application provides a combined unit, system, and method for alternating positive and negative pressure loading of the foundation treatment system, which offers advantages such as improved sealing, reduced air leakage, optimized drainage path, and enhanced foundation treatment efficiency.

[0027] The technical solutions of the embodiments of this application are described in detail below with reference to the accompanying drawings.

[0028] See Figures 1 to 7 This application provides a combined unit for alternating positive and negative pressure loading of foundation treatment, including a vacuum membrane 1. The vacuum membrane 1 has a first region 11 and a second region 12 surrounding the first region 11. The first region 11 has at least two pipes 2, which are interconnected through a sealing interface 3. The sealing interface 3 is connected to a drainage board 4 that penetrates the vacuum membrane 1, and the sealing interface 3 is sealed to the joint of the vacuum membrane 1. A sealing joint 5 is provided at the end of the pipe 2 away from the sealing interface 3. The second region 12 has an adhesive layer 6 surrounding the first region 11.

[0029] Vacuum membrane 1 is a flexible, airtight insulating material. The first region 11 is used to arrange pipes 2 and drainage boards 4. The second region 12 is an annular area surrounding the first region 11 and has an adhesive layer 6. Vacuum membrane 1 is laid on the surface of the foundation to be preloaded. Multiple vacuum membranes 1 are arranged in an array and sealed by overlapping and cross-laden adhesive layers 6 in the second region 12, forming an overall sealing layer covering the foundation to be preloaded. The combined unit has at least two pipes 2, which are connected by a sealing interface 3 located at the center of the diagonal of the first region 11. In specific implementations, the first region 11 can be equilateral triangle, square, hexagon, etc. For example, when the first region 11 is square, the pipes 2 are arranged perpendicularly or aligned to each other. The number of pipes 2 in the first region 11 is typically, but not limited to, two, three, or four. When the combined unit has two pipes 2, the structural form of the combined unit can be referenced. Figure 5 and Figure 7 ,in Figure 5 The combined unit shown can be defined as a linear combined unit, while Figure 7 The combined unit shown can be defined as an L-type combined unit. When the combined unit has three pipes 2, the structural form of the combined unit can be referred to... Figure 6 This combined unit can be defined as a T-type combined unit. When the combined unit has four pipes 2, the structural form of the combined unit can be referred to Figure 1The combined unit can be defined as a cross-shaped combined unit. Cross-shaped, T-shaped, straight, and L-shaped combined units together form a sealing layer covering the foundation to be preloaded, and are connected to form different pipeline network systems. In practical applications, the construction area of ​​the foundation to be preloaded ranges from several thousand to tens of thousands of square meters. To facilitate construction, the foundation is generally designed as a rectangular structure, thus the number of combined units used can reach several thousand to tens of thousands. When laying the combined units, to improve construction efficiency and reduce splicing errors caused by human experience, the foundation to be preloaded can be divided into an inner and outer ring. The outer ring surrounds the inner ring and is a rectangular ring formed by connecting several combined units end to end. The aforementioned cross-shaped combined units form the inner ring, while the outer ring is composed of straight, T-shaped, and L-shaped combined units. The straight combined units are located at the four corners of the rectangular ring, and two of the straight units are used not only to connect to the inner ring but also to connect to the external vacuum system 300 and pressurization system 400, respectively. In addition to connecting to the inner ring, one of the T-shaped combined units, pipe 2, connects to the external vacuum system 300 or pressurization system 400. The remaining combined units of the rectangular ring are L-shaped combined units. The first region 11 can be designed as a square, with its geometric characteristics of equal sides and right angles, providing a natural symmetry benchmark for the layout of pipe 2. When pipe 2 is arranged perpendicularly along the diagonal of the square (such as in a cross-shaped unit) or aligned along the edges (such as in a straight or L-shaped unit), a regular coordinate interface layout can be formed, ensuring that the interfaces of pipe 2 in adjacent units correspond one-to-one in spatial position. For example, the four pipes 2 of a cross-shaped unit extend along the diagonal of the square to the four vertices, and the interfaces of adjacent units can be directly connected through sealing joints 5 without additional angle adjustments, significantly reducing construction errors. At the same time, within the square area, the perpendicular or aligned pipes 2 can form a cross network, with their intersection point located at the center of the area, ensuring that positive and negative pressure loads are evenly transmitted from the center to the surrounding areas, reducing pressure blind spots. In this configuration, the combined unit connects the pipes 2 via the sealing joint 5. The vertical or aligned layout fixes the interface direction (e.g., 0°, 90°, 180°). For example, the four interfaces of the cross-shaped unit point to the four vertices of the square (90° vertical distribution), the two interfaces of the L-shaped unit are perpendicular at 90°, and the interfaces of the straight unit are aligned at 180°. The three can be combined to form a sealing layer of any shape.

[0030] In this embodiment, the sealing interface 3 is used for the connection between the internal pipes 2 of the combined unit, and to realize the through connection between the pipe 2 and the drainage plate 4. The sealing interface 3 can be a two-way connector, a three-way connector or a four-way connector. The center of the sealing interface 3 is provided with an interface for connecting the drainage plate 4. The interface is a stainless steel quick-connect connector and passes through the vacuum membrane 1. The joint between the interface and the vacuum membrane 1 is sealed by epoxy resin potting.

[0031] In this embodiment, the sealing joint 5 is located at the other end of the pipeline 2 and is used as a connection joint between the combined units and the external system. Specifically, a threaded quick-connect composite structure can be adopted to realize the quick connection of the pipeline 2 of the combined unit.

[0032] In this embodiment, modular prefabrication and self-sealing structure design enable standardized factory production and rapid on-site installation. Combined with multi-form pipelines 2 and sealing interfaces 3, it solves the problems of difficult sealing of large-area membranes, low construction efficiency, and poor drainage in traditional foundation treatment, ensuring the smoothness of drainage channels and overall sealing. When local faults such as air leakage occur, the corresponding combination unit can be quickly located and disassembled for replacement or repair, ensuring the continuity of foundation treatment and reinforcement effect.

[0033] Furthermore, the vacuum membrane 1 includes a double-layer sealing membrane, which is connected by thermoplastic sealing to form an installation cavity and an adhesive portion, with the adhesive portion surrounding the installation cavity; wherein, the installation cavity is the first region 11, and the adhesive portion is the second region 12. Specifically, the vacuum membrane 1 can be a double-layer polymer composite vacuum membrane 1, with an outer layer being a tensile and puncture-resistant membrane and an inner layer being an aging-resistant membrane. The circumferential edges of the two membrane materials are fused together using a thermoplastic sealing process to form an annular adhesive portion; simultaneously, an unfused portion is retained in the central region of the membrane material to form the installation cavity. The installation cavity, as the first region 11, is used to lay the pipes 2 and drainage boards 4 to improve the protective effect, while the adhesive portion, as the second region 12, is used to achieve a sealing layer for sealing the foundation to be pre-loaded through an adhesive layer.

[0034] Furthermore, the first region 11 is a polygonal region, and the pipeline 2 is laid out along the direction from the center to the vertex of the first region 11.

[0035] The first region 11 can be shaped like an equilateral triangle, square, or regular hexagon. For example, the regular geometric characteristics of a square make it easier to control the spacing of the pipes 2. When the pipes 2 extend along the diagonal, they can cover the maximum span from the center to the four corners of the square region, thereby reducing pressure transmission blind spots during vacuum suction or pressurization. Two, three, or four pipes 2 laid along the diagonal can form a cross network, with their intersection point located at the center of the region, forming a symmetrical drainage channel layout. This ensures that the stress distribution of the vacuum membrane 1 is more uniform when subjected to alternating positive and negative pressure, avoiding sealing failure caused by local deformation. At the same time, this intersection point is used to install the sealing interface 3, which is sealed to the vacuum membrane 1 by hot-melt welding or adhesive.

[0036] Correspondingly, the shape of the first region 11 can also be rectangular, triangular, or regular hexagonal. For example, when the assembly unit is regular hexagonal, the first region 11 is a regular hexagonal mounting cavity with a diagonal of 1m and a side length of 0.5m. It is formed by thermoplastic encapsulation of a double-layer sealing film. The fitting part is an annular area surrounding the mounting cavity. The number of pipes 2 in the regular hexagonal assembly unit is 2 to 6, connected at the center through a six-way quick-connect sealing interface 3, and used to connect to the drainage board 4. The outer ends of the six pipes 2 extend from the vertices of the hexagon and are fitted with sealing joints 5 for splicing adjacent units. The units are overlapped and covered, sealed by the adhesive layer 6 of the fitting part, forming an overall leak-free sealing layer.

[0037] Furthermore, the adhesive layer 6 is a cold-adhesive self-adhesive tape. The width of the adhesive layer 6 can be set to 30-50mm, as long as it ensures that adjacent combined units can be sealed tightly. Specifically, the cold-adhesive self-adhesive tape can be a pressure-sensitive tape with a butyl rubber substrate or a modified bitumen substrate. Its self-adhesive properties can adapt to the unevenness of the foundation surface and form a continuous sealing interface, ensuring a tight sealing layer. The designed cold-adhesive self-adhesive tape can also simplify the construction process, avoid the risk of thermal damage to the membrane material from the hot-melt process, and ensure the long-term sealing stability of the foundation treatment system.

[0038] Furthermore, the pipe diameter of the pipe 2 is 50mm to 100mm; the opening ratio of the drainage plate 4 is 5% to 15%, the opening diameter is 5mm to 10mm, and the outer surface of the drainage plate 4 is covered with non-woven fabric; the sealing interface 3 is a quick-connect connector.

[0039] See Figure 8 This application also proposes a positive and negative pressure alternating loading foundation treatment system, including a first subsystem 100, a second subsystem 200, a vacuum system 300, a pressurization system 400 and a detection system. The first subsystem 100 and the second subsystem 200 are respectively connected to the vacuum system 300 and the pressurization system 400 through valve control devices. The first subsystem 100 and the second subsystem 200 each include multiple positive and negative pressure alternating loading foundation treatment combination units. The combination units of the first subsystem 100 are interconnected through pipes 2, and the combination units of the second subsystem 200 are interconnected through pipes 2. The combination units of the first subsystem 100 and the combination units of the second subsystem 200 are arranged alternately on the surface of the foundation to be preloaded, and adjacent combination units are stacked crosswise and sealed together by adhesive layer 6 to form a sealing layer covering the foundation to be preloaded.

[0040] The valve control device is used to achieve independent switching and stable on / off between the first subsystem 100 and the second subsystem 200 in the vacuum system 300 and the pressurization system 400, and to meet the dynamic control of alternating positive and negative pressure loading. Specifically, an electric stainless steel ball valve can be used, with a rated pressure range of -0.1 to +1.0 MPa. It is equipped with an electric actuator and a PLC control system to ensure that the system achieves precise pressure control during cyclic loading of 7 to 30 days / stage, and ultimately ensures the design target of foundation bearing capacity and settlement.

[0041] The combined units of the first subsystem 100 and the second subsystem 200 are arranged in a checkerboard grid. The combined unit of the first subsystem 100 is block A, and the combined unit of the second subsystem 200 is block B. Blocks A and B are arranged alternately, and blocks A and B form blocks C. Blocks C are distributed in an array on the foundation to be preloaded.

[0042] Before deploying the system on the foundation site to be preloaded, the ground must first be leveled to ensure there are no significant undulations. Precise surveying and layout are then conducted using RTK-GPS or a total station to determine the boundaries of the area to be reinforced and the installation location of the cofferdam. To improve construction safety, supplementary geological surveys can be performed, using static cone penetration tests or vane shear tests to verify the physical and mechanical parameters of the soft soil layer, and to determine the organic matter content and distribution of underground obstacles in the foundation to be preloaded. If construction is affected, local replacement or clearing may be carried out to ensure the stability of subsequent construction. In addition, before deploying the system, three-dimensional positioning can be performed using the BIM model to determine the installation points of the drainage board 4. The software is used to divide the foundation to be preloaded into the first subsystem 100 construction area and the second subsystem 200 construction area. Then, a layer of non-woven fabric is laid on the surface of the foundation to be preloaded. The drainage board 4 is arranged in a square grid, with the penetration depth reaching the bottom of the silty clay layer. The top of the drainage board 4 extends out of the ground. Then, the drainage board 4 is installed one by one with cross-shaped combined units, straight combined units, T-shaped combined units and L-shaped combined units. The staggered arrangement of the combined units forms a sealing barrier through the adhesive layer 6.

[0043] During the operation of the foundation treatment system, the first subsystem 100 and the second subsystem 200 are connected to the vacuum system 300 or the pressurization system 400 respectively via valve control devices. First, both the first subsystem 100 and the second subsystem 200 are simultaneously evacuated. Once the foundation consolidation reaches the preset requirements, the vacuum state of the first subsystem 100 is maintained, while the second subsystem 200 is switched to a positive pressure state. After running for a period of time, the first subsystem 100 is switched back to the positive pressure state, and the second subsystem 200 is switched back to the vacuum state, with the two systems alternately applying pressure to create cyclic stress. During the vacuum preloading process, the detection system monitors the pressure parameters of each area in real time and dynamically adjusts the switching frequency of the subsystem's operating mode according to the foundation consolidation.

[0044] Compared with the existing technology, this system forms a positive and negative pressure cycle by alternating loading of the first subsystem 100 and the second subsystem 200, which effectively improves the pore water discharge efficiency. When the first subsystem 100 switches to positive pressure, it can peel off the mud skin on the outside of the drainage board 4, thereby improving the permeability of the drainage board 4.

[0045] Furthermore, the detection system includes a pore water pressure gauge, a settlement plate, and a vacuum gauge, which is used to collect data on the degree of consolidation of the foundation, the settlement rate, and positive and negative pressure parameters.

[0046] Specifically, pore water pressure gauges are deployed every 2 meters along the foundation depth to form a three-dimensional monitoring network, capturing changes in pore water pressure gradients across different soil layers. Settlement plates are distributed in a 100m × 100m grid, and displacement data is collected and transmitted to a central processor via wired or wireless means. Vacuum gauges are installed at the branch pipe connections of each assembly unit to monitor the negative pressure level in each area in real time. The pore water pressure gauges, settlement plates, and vacuum gauges are integrated via a data bus to form a multi-parameter synchronous acquisition system used to calculate the degree of consolidation, assess the settlement rate, and regulate positive and negative pressure parameters.

[0047] This application also proposes a method for alternating positive and negative pressure foundation treatment, which employs the aforementioned alternating positive and negative pressure foundation treatment system and includes the following steps: S1. Install the detection system on the foundation to be preloaded, then install the combined units of the first subsystem 100 and the second subsystem 200 in an alternating manner, and then install the vacuum system 300 and the pressurization system 400. S2. Start the vacuum system 300 and simultaneously perform vacuum treatment on the first subsystem 100 and the second subsystem 200 until the foundation consolidation degree meets the stage requirements. S3. The first subsystem 100 maintains a vacuum, and the pressurization system 400 is started to pressurize the second subsystem 200, while running for the first set time. S4. Start the pressurization system 400 to pressurize the first subsystem 100, and restore the second subsystem 200 to vacuum, while running for the first set time. S5. Repeat S3 and S4 to form a cyclic load; S6. Adjust the first set duration, the output power of the vacuum system 300 and the output power of the pressurization system 400 according to the monitoring data of the detection system until the foundation consolidation degree reaches the design requirements.

[0048] Specifically, after the vacuum system 300 is activated, negative pressure is applied to both sets of units simultaneously. When the soil initially consolidates, it switches to an alternating pressurization mode: one set maintains negative pressure to keep the soil in a compressed state, while the other set applies positive pressure to induce pore water migration. By periodically switching the pressurization targets, mud cake blockage caused by continuous negative pressure on the surface of drainage board 4 is avoided, while the positive pressure gradient enhances drainage efficiency. During the treatment process, the pressurization cycle and pressure value are dynamically adjusted based on real-time monitoring of settlement rate and pore water dissipation data to ensure that the soil completes consolidation under the optimal load combination.

[0049] In step S1, the installation points of the cross-shaped combination units of the first subsystem 100 are first located using a total station, forming a grid layout of blocks A. Then, the installation points of the L-shaped combination units of the second subsystem 200 are located at the midpoints of the row spacing in the grid layout of blocks A, forming a grid layout of blocks B. During the installation of the combination units, the adhesive layers 6 of the two subsystem combination units are ensured to be overlapped crosswise and bonded using linear pressure rollers to meet the sealing requirement of a pressure drop ≤ 1.5 kPa for 30 minutes under a vacuum of -80 kPa. If necessary, a flat plate can be temporarily placed at the bottom of the vacuum membrane 1 to provide a roller-bonding effect.

[0050] In step S4, when the second subsystem 200 restores the vacuum, the vacuum system 300 is started through the valve control device, and the vacuum level is raised to above -70kPa within 30 minutes, and then maintained for the first set time to ensure the stability of pressure switching.

[0051] In step S6, for different soil conditions, test area data can be used to determine the specific parameters for subsequent large-scale implementation, specifically through indoor consolidation tests on silty clay layers. Generally, when the degree of consolidation is <70%, the soil skeleton has not yet formed a stable structure, and applying positive pressure at this time can easily lead to shear failure; when the degree of consolidation is >70%, the pore water pressure dissipation rate drops to below 0.5 kPa / d, and the soil enters a slow consolidation stage, with the efficiency improvement of continued vacuum treatment being <10%. Field monitoring data shows that when the degree of consolidation reaches 70%, the foundation settlement rate stabilizes at 1.2 mm / d, and the void ratio drops to 1.2. At this time, initiating alternating positive and negative pressure loading can shorten the subsequent consolidation cycle by 40%, and the final settlement deviation is <5%. When test area data is unavailable, dynamic adjustments can be made by combining the results of on-site foundation settlement monitoring, pore water pressure monitoring, and consolidation degree monitoring. Among them, foundation settlement monitoring obtains surface and deep settlement rate data through settlement plates and layered settlement meters. When the settlement rate slows significantly and fails to reach the design settlement amount, drainage can be accelerated by increasing the positive pressure or shortening the positive-negative pressure alternation cycle, and the first subsystem 100 and the second subsystem 200 can be switched for the next cycle of loading. In this application, settlement monitoring is the primary control item, and other monitoring data are auxiliary items.

[0052] In this application, the cycle alternation period can be dynamically adjusted according to the changes in pore water pressure dissipation rate, settlement rate, and consolidation degree. For example, when the settlement plate monitoring data is ≤1mm / d for 3 consecutive days, the output power of the pressurization system 400 is increased by 20%, and the first set duration is shortened to 7 days; when the pore water pressure gauge detects a dissipation rate <1kPa / d, the output power of the vacuum system 300 is reduced by 10%, and the first set duration is extended to 30 days; when the foundation consolidation degree reaches 80%, the alternation period of positive and negative pressure is adjusted to 20 days; when it reaches 90%, it switches to vacuum maintenance mode until the calculated final settlement amount is ≤50cm.

[0053] Through the aforementioned real-time monitoring and dynamic adjustments, the foundation treatment process can better conform to the soil consolidation development law, avoid the risks caused by excessively rapid drainage or overloading, thereby optimizing the reinforcement effect and ensuring construction safety.

[0054] Furthermore, the requirement that the foundation consolidation degree reaches the stage specifically means that the foundation consolidation degree reaches 70%; the positive pressure range of the pressurization treatment is +20kPa to +60kPa, and the negative pressure range of the vacuum treatment is -60kPa to -80kPa; the first set duration is 7 days to 30 days.

[0055] Specifically, when the second subsystem 200 applies a positive pressure of +20kPa to +60kPa, an outward pressure gradient is formed inside the combined unit, forcing the pore water to flow in the opposite direction. The water flow generates shear force on the mud skin on the surface of the drainage plate 4. When the shear force exceeds the adhesion force between the mud skin and the drainage plate 4, the mud skin peels off. Subsequently, the first subsystem 100 restores a negative pressure of -60kPa to -80kPa, generating an inward suction force that discharges the peeled mud skin debris through the channels of the drainage plate 4, avoiding secondary blockage. Experimental comparison shows that the permeability recovery rate of the drainage plate 4 using alternating positive and negative pressure loading reaches 85%, while that of traditional vacuum preloading is only 32%.

[0056] Furthermore, the requirement that the foundation consolidation meets the design requirements specifically means that the characteristic value of the foundation bearing capacity is not less than 80 kPa, and the estimated final settlement is not greater than 50 cm.

[0057] Corresponding to the foregoing embodiments, this application also provides an application example of a combined unit, system, and method for alternating positive and negative pressure loading of foundation treatment.

[0058] 1. Engineering conditions A coastal soft soil area has an area of ​​160,000 m2, a length of 400 m and a width of 400 m. The soil strata, from top to bottom, consist of a silt layer and a silty clay layer. The silt layer is 6 m thick, and the silty clay layer is 4 m thick. The design requirements are a foundation bearing capacity characteristic value ≥ 80 kPa and a post-construction settlement ≤ 50 cm.

[0059] 2. Site pretreatment and surveying / layout 2.1 The target site was leveled to ensure a smooth surface without significant undulations. RTK-GPS or a total station was used for precise surveying and layout to determine the boundaries of the area to be reinforced and the installation location of the cofferdam. Simultaneously, supplementary geological surveys were conducted, with three exploration boreholes laid out along the site's central axis. Static cone penetration tests were used to verify the physical and mechanical parameters of the soft soil layer, and vane shear tests were used to determine the undrained shear strength of the silt layer. The distribution of underground obstacles (such as gravel and tree roots) was identified, and localized obstacles were manually cleared and replaced with native soil to ensure the stability of subsequent construction.

[0060] 2.2 Drainage Board 4: A 1m × 1m square grid is used for planning and layout (a total of 160,000 drainage boards 4). The site is divided into an inner ring area (398m × 398m) and an outer ring area (400m × 400m, a 1m wide rectangular ring). The quantity and layout of the four types of combination units are determined. The inner ring area uses all cross-shaped combination units, totaling 158,404 units. The four corners of the outer ring area use straight-line combination units (4 units in total), T-shaped combination units (2 units in total), and the remaining positions use L-shaped combination units (794 units in total).

[0061] 3. Drainage board installation Polyester non-woven fabric is laid on the foundation, and 160,000 drainage boards 4 are inserted in a 1m×1m square grid with a penetration depth of 10m. A 50cm length is reserved at the top of the drainage board 4 to connect with the prefabricated sealing interface 3 at the bottom of the combined unit.

[0062] 4. Module assembly The cross-shaped combination unit has four mutually perpendicular pipes 2 arranged along two diagonals. The connection nodes of the four pipes 2 are equipped with sealed plug sockets. The inner circle area is divided into a first subsystem 100 and a second subsystem 200. The cross-shaped combination unit can connect adjacent units in four directions at the same time, respectively connecting and constructing the first subsystem 100 and the second subsystem 200, and connecting the combination units in the outer circle area to form a complete loop.

[0063] The L-shaped modular unit has two mutually perpendicular pipes 2. The connection node of the two pipes 2 is equipped with a sealed plug-in socket. This connection node is located at the center point of the first area 11 and is used to splice with the cross-shaped modular unit.

[0064] A straight-line combination unit is provided with one straight pipe 2. Two straight-line combination units are connected to the vacuum system 300 and the pressurization system 400 respectively. The straight-line combination units are all connected to the cross-shaped combination unit of the first subsystem 100. The pipes 2 of the remaining two straight-line combination units are closed to form a complete loop.

[0065] The T-type combination unit is equipped with three pipes 2, one of which is connected to the vacuum system 300 or the pressurization system 400, and the remaining interfaces are connected to the L-type combination unit of the second subsystem 200 and the cross-type combination unit of the second subsystem 200.

[0066] The first subsystem 100 is connected to the vacuum system 300 through one of its linear combination units and to the pressurization system 400 through another linear combination unit; the second subsystem 200 is connected to the vacuum system 300 through one of its T-type combination units and to the pressurization system 400 through another T-type combination unit.

[0067] 5. Module assembly and system installation After the first subsystem 100 and the second subsystem 200 are assembled, a sealing test is performed. The entire sealing layer is evacuated to -60 kPa. After the valve is closed, the pressure drop is ≤1.5 kPa after 30 minutes, confirming that the sealing is qualified.

[0068] 6. Construction Process 6.1 Open the valve control device and start the vacuum system 300 to perform vacuum treatment on the first subsystem 100 and the second subsystem 200. The vacuum degree is controlled at -80kPa and maintained for 60 days. During this period, the degree of consolidation of the foundation is monitored by a pore water pressure gauge. 6.2 After the foundation consolidation degree reaches 70%, continue to vacuum the first subsystem 100. Close the channel between the vacuum system 300 and the second subsystem 200 through the valve control device, open the channel between the pressurization system 400 and the second subsystem 200, and pressurize the second subsystem 200. The pressure value is controlled at +30kPa for 14 days. After running for 14 days, switch the first subsystem 100 to pressurization and the second subsystem 200 to vacuum, continuing for 14 days; repeat the alternating cycle four times.

[0069] 6.3 Test the degree of consolidation, void ratio and settlement rate. Construction is completed after the design requirements are met.

[0070] The various embodiments of this application have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. A combined unit for alternating positive and negative pressure loading of foundation treatment, characterized in that, The device includes a vacuum membrane, which has a first region and a second region surrounding the first region. The first region has at least two pipes that are interconnected by a sealing interface. The sealing interface is connected to a drainage plate that penetrates the vacuum membrane, and the sealing interface is sealed to the seam of the vacuum membrane. A sealing joint is provided at the end of each pipe away from the sealing interface. The second region has an adhesive layer surrounding the first region.

2. The alternating positive and negative pressure loading foundation treatment unit according to claim 1, characterized in that, The vacuum membrane includes a double-layer sealing membrane, which is connected by a thermoplastic seal to form an installation cavity and a fitting portion, the fitting portion surrounding the installation cavity; wherein, the installation cavity is the first region, and the fitting portion is the second region.

3. The alternating positive and negative pressure loading foundation treatment unit according to claim 1, characterized in that, The first region is a polygonal region, and the pipeline is laid out along the direction from the center to the vertex of the first region.

4. The alternating positive and negative pressure loading foundation treatment unit according to claim 1, characterized in that, The adhesive layer is a cold-adhesive self-adhesive tape.

5. The alternating positive and negative pressure loading foundation treatment unit according to claim 1, characterized in that, The pipe diameter is 50mm to 100mm; the drainage board has an opening rate of 5% to 15%, an opening diameter of 5mm to 10mm, and the outer surface of the drainage board is covered with non-woven fabric; the sealing interface is a quick-connect connector.

6. A foundation treatment system with alternating positive and negative pressure loading, characterized in that, It includes a first subsystem, a second subsystem, a vacuum system, a pressurization system, and a detection system. The first subsystem and the second subsystem are respectively connected to the vacuum system and the pressurization system through valve control devices. The first subsystem and the second subsystem each include multiple positive and negative pressure alternating loading foundation treatment combination units as described in any one of claims 1-5. The combination units of the first subsystem are interconnected through pipelines, and the combination units of the second subsystem are interconnected through pipelines. The combination units of the first subsystem and the combination units of the second subsystem are arranged alternately on the surface of the foundation to be preloaded, and adjacent combination units are stacked crosswise and sealed together by an adhesive layer to form a sealing layer covering the foundation to be preloaded.

7. The alternating positive and negative pressure loading foundation treatment system according to claim 6, characterized in that, The detection system includes a pore water pressure gauge, a settlement plate, and a vacuum gauge. The detection system is used to collect data on the degree of consolidation of the foundation, the settlement rate, and positive and negative pressure parameters.

8. A method for foundation treatment using alternating positive and negative pressure loading, characterized in that, The foundation treatment system using alternating positive and negative pressure loading as described in any one of claims 6 or 7 includes the following steps: S1. Install the detection system on the foundation to be preloaded, then install the combined units of the first and second subsystems in an alternating manner, and then install the vacuum system and pressurization system; S2. Start the vacuum system and simultaneously perform vacuum treatment on the first and second subsystems, continuing the treatment until the foundation consolidation degree meets the stage requirements. S3. The first subsystem maintains a vacuum, and the pressurization system is started to pressurize the second subsystem while running for the first set time. S4. Start the pressurization system to pressurize the first subsystem, restore the second subsystem to vacuum, and run for the first set time at the same time; S5. Repeat S3 and S4 to form a cyclic load; S6. Adjust the first set duration, the output power of the vacuum system, and the output power of the pressurization system according to the monitoring data of the detection system until the foundation consolidation degree reaches the design requirements.

9. The foundation treatment method with alternating positive and negative pressure loading according to claim 8, characterized in that, The requirement that the foundation consolidation degree reaches the stage specifically means that the foundation consolidation degree reaches 70%; the positive pressure range of the pressurization treatment is +20kPa to +60kPa, and the negative pressure range of the vacuum treatment is -60kPa to -80kPa; the first set duration is 7 days to 30 days.

10. The foundation treatment method with alternating positive and negative pressure loading according to claim 8, characterized in that, The requirement that the foundation consolidation meets the design requirements specifically means that the characteristic value of the foundation bearing capacity is not less than 80 kPa and the settlement is not greater than 50 cm.

Images