A simulation experiment system and method for seawater intrusion and land subsidence

Abstract

The application provides a simulation experiment system and method for seawater intrusion and land subsidence, and belongs to the technical field of marine simulation devices, and comprises a test box, the test box is divided into three areas along the horizontal direction by two hole glass plates, and the three areas are a seawater chamber, a main observation area and a fresh water chamber in sequence; the main observation area is filled in layers into four layers, and a pore water pressure sensor array and an electric conductivity sensor array are arranged in the soil body; four dial settlement marks for transmitting displacement are pre-buried in the main observation area from top to bottom, a pumping well is arranged in the main observation area, the well pipe of the pumping well longitudinally penetrates through the whole model, a glass pipe is arranged in the section corresponding to the confined aquifer and is wrapped with nylon gauze, and the section penetrating through the relative aquiclude is a sealed glass pipe; and the coupling relationship between the pore water pressure change and the soil body deformation is established according to the values of the settlement marks and the sensors. The application improves the accuracy of pumping simulation and reveals the cooperative disaster mechanism of seawater intrusion and land subsidence.

Description

Technical Field

[0001] This invention belongs to the field of marine simulation device technology, and particularly relates to a simulation experimental system and method for seawater intrusion and land subsidence. 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] Due to the uneven spatial and temporal distribution of surface water resources, coupled with accelerated industrialization and urbanization, many coastal cities have long relied on groundwater extraction as a supplementary water source. However, excessive groundwater extraction can trigger two interconnected and synergistic geological hazards: seawater intrusion and land subsidence, seriously threatening groundwater resources, ecosystem security, and infrastructure stability. To study these mechanisms, physical simulation experiments have become a crucial method.

[0004] Existing seepage simulation devices mainly focus on hydrogeological and geochemical processes, lacking the ability to simultaneously monitor the mechanical response of soil and rock and the ground settlement during pumping. Furthermore, mathematical analytical models used to assess the extent of seawater intrusion and sustainable extraction in confined aquifers are limited to numerical methods and cannot provide intuitive verification of physical models or data on mechanical processes. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, this invention proposes a simulation experimental system and method for seawater intrusion and land subsidence, in order to solve the problem of lacking a method for synchronous reproduction and quantitative analysis of the coupling mechanism between seawater intrusion and land subsidence in physical simulation.

[0006] To achieve the above objectives, one or more embodiments of the present invention provide the following technical solutions: In one aspect, the present invention discloses a simulation experimental system for seawater intrusion and land subsidence, comprising: a test chamber, wherein a seawater tank is provided on one side of the test chamber and a freshwater tank is provided on the other side; the test chamber is divided into three areas horizontally by two perforated glass plates, namely a seawater chamber, a main observation area, and a freshwater chamber; the main observation area is constructed in four layers, the first and third layers from top to bottom being relatively impermeable layers made of clay / silty clay, and the second and fourth layers being confined aquifers made of sand, wherein pore water pressure sensor arrays and conductivity sensor arrays are arranged within the soil; the main observation area is pre-embedded from top to bottom with four sensors for transmitting pressure. The model is constructed using micrometer settlement markers. The lower end of the first micrometer settlement marker contacts the top surface of the first relative impermeable layer, the lower end of the second micrometer settlement marker contacts the top surface of the first confined aquifer, the lower end of the third micrometer settlement marker contacts the top surface of the second relative impermeable layer, and the lower end of the fourth micrometer settlement marker contacts the top surface of the second confined aquifer. Pumping wells are installed in the main observation area. The well pipes of the pumping wells run longitudinally through the entire model. In sections corresponding to the confined aquifer, they are constructed as perforated glass tubes wrapped with nylon mesh, while in sections passing through the relative impermeable layers, they are sealed glass tubes. A coupling relationship between pore water pressure changes and soil deformation is established based on the values ​​from the settlement markers and sensors. The establishment of the coupling relationship between pore water pressure changes and soil deformation includes: By deploying pore water pressure sensor arrays in the relatively impermeable layer and the confined aquifer, the changes in pore water pressure at each point with time and space during the pumping process are monitored in real time during the pore water pressure decrease process. By setting up micrometer settlement markers on the top surfaces of the relative impermeable layer and the confined aquifer, the settlement at each monitoring point is measured to obtain the soil deformation changes. Based on the changes in pore water pressure and soil deformation, the Biot consolidation equation is used to establish the coupling relationship between the changes in pore water pressure and soil deformation.

[0007] Secondly, this invention discloses a simulation experimental method for seawater intrusion and land subsidence, utilizing the aforementioned simulation experimental system for seawater intrusion and land subsidence, comprising: Clay / silty clay and sand were layered and compacted in the main observation area. After the soil was filled, it was saturated with water and left to stand. A pore water pressure sensor, conductivity sensor, micrometer settlement gauge and pumping well were installed. Turn on both peristaltic pumps, control the freshwater side pump to supply water to the freshwater chamber, and the seawater side pump to supply water to the seawater chamber at a lower speed than the freshwater side. Observe the values ​​of each sensor until the system reaches a balanced state, which is recorded as the initial balanced state. Record the readings of all sensors. The pumping equipment is started to pump water from the pumping well at a constant rate, and the values ​​of the pore water pressure sensor, conductivity sensor and micrometer sedimentation scale are monitored and recorded simultaneously to obtain the pore water pressure, conductivity and sedimentation. The changes in pore water pressure caused by pumping, the migration of the sea-sea interface, and the settlement of the top surface of the confined aquifer and the relative impermeable layer are calculated based on pore water pressure, conductivity, and settlement, thereby establishing the coupling relationship between changes in pore water pressure and soil deformation.

[0008] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a simulation experimental system for seawater intrusion and land subsidence, solving the problem in existing technologies that cannot intuitively and quantitatively reveal the synergistic mechanism of the two events. It deploys pumping wells in aquifers to accurately simulate groundwater extraction and innovatively integrates a synchronous monitoring network comprising a pore water pressure sensor array, a conductivity sensor array, and a micrometer settlement gauge. This network can capture in real-time and quantitatively three parallel and interconnected dynamic coupled processes: "pumping, time, and pore water pressure decrease," "pumping, pore water pressure decrease, effective stress increase, and soil subsidence," and "pumping, time, and saline-water interface migration to the landward side." This provides direct physical evidence and quantitative data support for understanding the underlying driving principles, assessing disaster risks, and verifying the comprehensive effectiveness of prevention and control measures.

[0009] 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

[0010] 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.

[0011] Figure 1 This is a schematic diagram of the overall structure of the simulation experiment system for seawater intrusion and land subsidence described in Embodiment 1 of the present invention.

[0012] Figure 2 This is a front view of the simulation experiment system for seawater intrusion and land subsidence described in Embodiment 1 of the present invention.

[0013] Figure 3 This is a schematic diagram of the structure of the pumping well described in Embodiment 1 of the present invention.

[0014] In the diagram: 1. Test chamber; 2. Seawater tank; 3. Freshwater tank; 4. Peristaltic pump; 5. Seawater chamber; 6. Freshwater chamber; 7. Perforated glass plate; 8. Overflow outlet; 9. Relative impermeable layer; 10. Confined aquifer; 11. Pumping well; 12. Pumping equipment; 13. Water bucket; 14. Micrometer settlement gauge; 15. Pore water pressure sensor; 16. Conductivity sensor. Detailed Implementation

[0015] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration 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.

[0016] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations of the present invention.

[0017] Where there is no conflict, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0018] The shortcomings of existing technologies are as follows: First, although traditional physical simulation devices can simulate the effects of seawater intrusion or cutoff walls, their monitoring methods mainly rely on visual observation and salinity measurement, lacking the ability to synchronously and quantitatively monitor the soil mechanical response caused by pumping, i.e., changes in pore water pressure and soil deformation. This results in the inability to reveal the mechanism of land subsidence and its coupling relationship with seawater intrusion. Second, although mainstream numerical simulation methods can quickly assess the intrusion range, they cannot provide intuitive verification of physical models, and the reliability of their calculation results lacks direct experimental data supporting the mechanical processes.

[0019] To address the aforementioned shortcomings, the purpose of this invention is to provide a comprehensive simulation experimental system and method for seawater intrusion and land subsidence. This system can simultaneously induce seawater intrusion and land subsidence processes within the same physical model. Through an integrated array of pore water pressure sensors, conductivity sensors, and a micrometer-scale subsidence gauge, it achieves synchronous, real-time, and quantitative monitoring of the "seepage field-chemical field-mechanical field," thereby directly capturing and quantitatively analyzing the dynamic coupling mechanism between freshwater and brackish water interface migration and aquifer compression and subsidence during pumping. This provides solid experimental evidence for revealing the co-evolutionary laws of the two disasters.

[0020] Example 1 In one or more embodiments, a simulation experimental system for seawater intrusion and land subsidence is disclosed, such as Figures 1-2As shown, it includes: a test chamber 1, with a seawater tank 2 on one side and a freshwater tank 3 on the other side; the test chamber 1 is divided into three areas horizontally by two perforated glass plates 7, namely a seawater chamber 5, a main observation area, and a freshwater chamber 6; the main observation area is filled in four layers, with the first and third layers being relatively impermeable layers 9 made of clay / silty clay from top to bottom, and the second and fourth layers being confined aquifers 10 made of sand, and the sand is washed, soaked, and dried before filling. An array of pore water pressure sensors 15 and an array of conductivity sensors 16 are installed inside. Four micrometer settlement markers 14 for transmitting displacement are pre-embedded from top to bottom in the main observation area. The lower end of the first micrometer settlement marker contacts the top surface of the first opposing aquifer, the lower end of the second micrometer settlement marker contacts the top surface of the first confined aquifer, the lower end of the third micrometer settlement marker contacts the top surface of the second opposing aquifer, and the lower end of the fourth micrometer settlement marker contacts the top surface of the second confined aquifer. Pumping wells 11 are also installed in the main observation area. Figure 3 As shown, the well pipe of the pumping well runs longitudinally through the entire model. In the section corresponding to the confined aquifer 10, it is set as a glass tube with a hole and wrapped with nylon mesh, while the section passing through the relative impermeable layer 9 is a sealed glass tube. This design ensures that the pumping action only acts on the target confined aquifer.

[0021] In this embodiment, sand is used to simulate a confined aquifer, and a relatively impermeable layer made of clay / silty clay is set up to construct a physical model basis that can simultaneously generate significant seawater intrusion and land subsidence.

[0022] In this embodiment, the test chamber 1 is assembled from 1.2cm acrylic transparent panels into a topless box with a length × height × width of 200cm × 100cm × 70cm.

[0023] Furthermore, the test chamber 1 is equipped with overflow ports 8 on both the left and right sides, such as... Figures 1-2As shown, from left to right, the structure consists of a seawater chamber 5 for simulating the sea boundary, a main observation area for simulating the soil, and a freshwater chamber 6 for simulating the land boundary. To achieve a stable and controllable head, the seawater chamber 5 and the freshwater chamber 6 are connected on both sides of the main observation area by perforated glass plates 7 covered with nylon mesh. Seawater and freshwater are supplied to the chambers from the seawater tanks and freshwater tanks on both sides by peristaltic pumps 4, respectively. The seawater is a 35g / L NaCl solution, and carmine is used as the staining agent due to its low pollutant content and strong coloring power. By setting different overflow outlet heights 8, with the overflow outlet on the freshwater side higher than that on the seawater side (65cm on the freshwater side and 60cm on the seawater side in this embodiment), a stable hydraulic gradient from land to sea is maintained. The water levels in the seawater chamber and the freshwater chamber are independently controlled through the overflow outlets, thereby forming a controllable and stable head difference at both ends of the confined aquifer. Therefore, a stable groundwater flow from land to sea is established in the test chamber to simulate the freshwater runoff in the real coastal zone, thereby providing an initial dynamic equilibrium state for the freshwater interface and serving as the basic driving condition for subsequent pumping to trigger seawater intrusion.

[0024] Furthermore, the aforementioned pumping well 11 is connected to a high-precision pumping device 12 via pipeline to achieve constant flow pumping, simulating human groundwater extraction activities. The pumped water is discharged into a bucket 13 for unified treatment after the experiment.

[0025] Furthermore, an array of pore water pressure sensors (15) and an array of electrical conductivity sensors (16) were deployed within the soil. Several pore water pressure sensors and electrical conductivity sensors were installed in each layer of the soil to capture, in situ and in real-time, pressure field changes caused by pumping and the migration of the seawater-freshwater interface. Additionally, a micrometer settlement gauge (14) was used to directly measure the settlement relative to the top surface of the impermeable layer and the confined aquifer. All sensors were connected to a multi-channel data acquisition unit to achieve synchronous data acquisition and recording.

[0026] This embodiment integrates a pore water pressure sensor array, a conductivity sensor array, and a micrometer settlement gauge, enabling synchronous, real-time, and in-situ monitoring of the seepage field, chemical field, and mechanical field, thereby directly capturing and quantitatively analyzing the coupling process of the two disasters.

[0027] Based on the above system, the experimental process of this invention is as follows: First, the system is initialized by filling and compacting the prepared clay / silty clay and sand in layers. After the soil is filled, it is left to stand for at least 5 hours with water before installing the sensors and pumping wells.

[0028] Subsequently, the peristaltic pumps 4 on both sides were turned on, and the freshwater side pump was controlled to supply water to the freshwater chamber 6 at a certain speed, while the seawater side pump supplied water to the seawater chamber 5 at a lower speed than the freshwater side. The seawater was a 35g / L NaCl solution stained with carmine. The water level was stably controlled at 65cm on the freshwater side and 60cm on the seawater side through the overflow port 8. The water level and the readings of each sensor were continuously observed. When the water levels on both sides remained stable, the overflow was uniform, and the readings of each sensor did not change significantly during the continuous observation period, the system was considered to have reached the initial equilibrium state, and the readings of each sensor at this time were recorded.

[0029] Then, the pumping equipment 12 is started to pump water from the pumping well 11 at a slow rate, and the decrease in pore water pressure, the migration of the seawater interface, and the settlement of the top surface of the confined aquifer and the relative impermeable layer are monitored and recorded simultaneously.

[0030] Specifically, pore water pressure sensor arrays are deployed in the relatively impermeable layer and the confined aquifer to capture the pore water pressure drop process and monitor the changes in pore water pressure p (unit: Pa) at various points over time and space during pumping. When the spatiotemporal distribution of pore water pressure changes due to pumping, the time term coefficients are expanded as follows:

[0031] in, The density of pore water; For time.

[0032] Substituting into the continuity equation, we get:

[0033] in, To satisfy Darcy's law for percolation flow.

[0034] Substituting Darcy's law, we get:

[0035] Summarized as follows:

[0036] Where p is the pore water pressure; The equivalent seepage coefficient is expressed in terms of pore water pressure. These are the parameters for pressure water storage. Porosity is the equivalent compressibility coefficient; Q is the source and sink term, which is usually negative during pumping. From this, the diffusion response of pore water pressure under pumping conditions can be obtained.

[0037] Micrometer settlement gauges are installed on the top surfaces of the relatively impermeable and confined aquifers to measure soil deformation. These gauges measure the vertical displacement, or settlement, at each monitoring point. In theoretical analysis, soil deformation can be represented as a displacement vector. (i.e., settlement), combined with the pore water pressure p, when pumping causes a change in pore water pressure, the effective stress changes accordingly. The total stress and the effective stress satisfy:

[0038] According to the constitutive relation of linear elasticity with small deformation, we have:

[0039]

[0040] According to the static equilibrium equations, we can obtain:

[0041] In summary:

[0042] According to the definition of volumetric strain, we can obtain:

[0043] in, and These are the total stress and the effective stress tensor, respectively. For Biot coefficients; It is the Hamiltonian differential operator; C is a second-order unit tensor; C is a fourth-order elasticity matrix; For strain tensor; For mixed density; For volumetric strain; Let g be the acceleration due to gravity. This paper adopts the sign convention of tensile stress being positive and compression being negative; therefore, under compression... <0. This explains why changes in pore water pressure cause changes in effective stress and soil deformation.

[0044] Furthermore, based on the previous two points, this invention establishes a coupling relationship between pore water pressure changes and soil deformation. The present invention employs the Biot consolidation equation:

[0045]

[0046] Where M is the Biot modulus, used to characterize the energy storage capacity and compressibility of a saturated porous media system; For source and sink terms, negative values ​​are taken when pumping water; To satisfy Darcy's law for percolation flow.

[0047] As one implementation method, carmine red is used to color a 35 g / L NaCl solution to approximate seawater salinity conditions, and the migration process at the brackish water interface is visually identified through color changes. Conductivity sensor arrays are deployed in the relatively impermeable layer and the confined aquifer to monitor the water conductivity (unit: ...) in real time. The changes are observed, and based on the pre-established calibration relationship between conductivity and NaCl concentration, the calibration equation satisfies:

[0048] in, The effective concentration of NaCl is expressed in g / L; EC is the conductivity, expressed in g / L. ; and The coefficients are denoted as the fitting coefficients of the calibration equation, and the slope and intercept are denoted as , respectively. After converting the measured conductivity at each monitoring point into the equivalent NaCl concentration, the freshwater concentration and the 35 g / L NaCl concentration in saline water are used as the two reference points, namely the freshwater end-member concentration and the saline end-member concentration. The area where the equivalent NaCl concentration is in the range of 10%-90% of the saline end-member concentration is defined as the freshwater-saline water transition zone, and the position corresponding to the equivalent NaCl concentration reaching 50% of the saline end-member concentration is defined as the freshwater-saline water interface.

[0049] There is a corresponding relationship between the structural layout and calculation of this experimental setup. Pumping wells are used to generate source-sink disturbances, and their effect is represented as source-sink terms in the governing equations. An array of pore water pressure sensors is used to acquire pore water pressure *p* at different locations, providing monitoring variables for the pressure diffusion equation and Biot's consolidation equation; a micrometer settlement gauge is used to measure the vertical displacement of the soil, and its results can be compared with the displacement vector... and volumetric strain Correspondingly, the conductivity sensor array is used to acquire the water conductivity EC in real time, and convert it to NaCl equivalent concentration through the calibration relationship between conductivity and NaCl equivalent concentration. This device is used to determine the location of the brackish water transition zone and interface. Therefore, it not only enables simultaneous monitoring of pore pressure, sedimentation, and salt migration processes under pumping conditions, but also provides a basis for calculation. Furthermore, through this complete technical solution, the present invention achieves intuitive reproduction and precise quantitative analysis of complex hydrological and mechanical coupling processes.

[0050] By integrating an array of pore water pressure sensors, an array of conductivity sensors, and a micrometer-based settlement gauge, this invention can not only monitor salinity changes caused by seawater intrusion like existing technologies, but also synchronously and quantitatively capture the mechanical response, i.e., settlement, induced by pumping, within a physical model. This allows for the direct establishment of a complete and continuous quantitative causal chain linking "pumping volume, real-time decrease in pore water pressure, accurate calculation of effective stress, and soil settlement," thereby fundamentally revealing the intrinsic coupling mechanism between these two hazards: seawater intrusion and land subsidence.

[0051] Example 2 In one or more embodiments, an experimental method for simulating seawater intrusion and land subsidence is disclosed. Using this experimental system, a physical experimental method is provided to directly verify how a decrease in pore water pressure leads to an increase in effective stress, thereby inducing soil subsidence, in the context of seawater intrusion. The method includes the following steps: Step S1: Fill the main observation area with clay / silty clay and sand in layers and compact it. After the soil is filled, let it stand for at least 5 hours with water. Install pore water pressure sensor, conductivity sensor, micrometer settlement gauge and pumping well.

[0052] Step S2: Turn on both peristaltic pumps 4, control the freshwater side pump to supply water to the freshwater chamber 6 at a certain speed, and control the seawater side pump to supply water to the seawater chamber 5 at a lower speed than the freshwater side. The seawater is a 35g / L NaCl solution stained with carmine. Through the overflow port 8, stabilize the water level at 65cm on the freshwater side and 60cm on the seawater side. Observe the values ​​of each sensor until the system reaches a balanced state, which is recorded as the initial balanced state. At this time, record the readings of all sensors.

[0053] Step S3: Start the pumping equipment 12 to pump water from the pumping well 11 at a slow speed at a constant rate, and simultaneously monitor and record the values ​​of the pore water pressure sensor, conductivity sensor, and micrometer sedimentation scale to obtain the pore water pressure, conductivity, and sedimentation.

[0054] Step S4: Calculate the changes in pore water pressure caused by pumping, the migration of the sea-sea interface, and the settlement of the top surface of the confined aquifer and the relative impermeable layer based on the pore water pressure, conductivity, and settlement, thereby establishing the coupling relationship between changes in pore water pressure and soil deformation.

[0055] This embodiment demonstrates how controlled pumping in a saturated aquifer with a stable brackish water interface allows for a direct representation and study of the entire process by which groundwater over-extraction simultaneously triggers the synergistic disaster of seawater intrusion and land subsidence.

[0056] The descriptions of each embodiment in the above embodiments have different focuses. For parts not described in detail in a certain embodiment, please refer to the relevant descriptions in other embodiments.

[0057] The above description is merely a preferred embodiment of the present invention and is not intended to limit the 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 simulation experimental system for seawater intrusion and land subsidence, characterized in that, include: The test chamber has a seawater tank on one side and a freshwater tank on the other. The test chamber is divided into three areas horizontally by two perforated glass plates: a seawater chamber, a main observation area, and a freshwater chamber. The main observation area is constructed in four layers. From top to bottom, the first and third layers are relatively impermeable layers made of clay / silty clay, and the second and fourth layers are confined aquifers made of sand. A pore water pressure sensor array and a conductivity sensor array are installed within the soil. Four micrometer settlement markers for transmitting displacement are pre-embedded in the main observation area from top to bottom. The first micrometer settlement marker… The lower end of the first sub-insulator is in contact with the top surface of the first relative impermeable layer; the lower end of the second sub-insulator is in contact with the top surface of the first confined aquifer; the lower end of the third sub-insulator is in contact with the top surface of the second relative impermeable layer; and the lower end of the fourth sub-insulator is in contact with the top surface of the second confined aquifer. Pumping wells are installed in the main observation area. The well pipes of the pumping wells run longitudinally through the entire model. In sections corresponding to the confined aquifer, they are perforated glass tubes wrapped with nylon mesh; in sections passing through the relative impermeable layers, they are sealed glass tubes. A coupling relationship between pore water pressure changes and soil deformation is established based on the values ​​of the settlement markers and sensors. The establishment of the coupling relationship between pore water pressure changes and soil deformation includes: By deploying pore water pressure sensor arrays in the relatively impermeable layer and the confined aquifer, the changes in pore water pressure at each point with time and space during the pumping process are monitored in real time during the pore water pressure decrease process. By setting up micrometer settlement markers on the top surfaces of the relative impermeable layer and the confined aquifer, the settlement at each monitoring point is measured to obtain the soil deformation changes. Based on the changes in pore water pressure and soil deformation, the Biot consolidation equation is used to establish the coupling relationship between the changes in pore water pressure and soil deformation. The seawater tank is connected to the seawater chamber via a peristaltic pump, and the freshwater tank is connected to the freshwater chamber via a peristaltic pump. The test chamber is equipped with overflow outlets on both the left and right sides, with the overflow outlet on the freshwater side being higher than that on the seawater side. Several pore water pressure sensors and conductivity sensors are installed in each layer of the soil to capture in situ, real-time changes in the pressure field caused by pumping and the migration of the seawater-freshwater interface.

2. The simulation experimental system for seawater intrusion and land subsidence as described in claim 1, characterized in that, When the spatiotemporal distribution of pore water pressure changes due to pumping, the pore water pressure satisfies the following diffusion control equation: Where p is the pore water pressure; The equivalent seepage coefficient is expressed in terms of pore water pressure. These are the parameters for pressure water storage. Porosity The equivalent compression factor is Q; Q represents the source and sink terms. For time.

3. The simulation experimental system for seawater intrusion and land subsidence as described in claim 1, characterized in that, When pumping causes a change in pore water pressure, the effective stress changes accordingly, and the soil deformation changes as follows: in, For Biot coefficients; It is the Hamiltonian differential operator; C is a second-order unit tensor; C is a fourth-order elasticity matrix; For strain tensor; For mixed density; For volumetric strain; is the displacement vector; p is the pore water pressure; This is the acceleration due to gravity.

4. The simulation experimental system for seawater intrusion and land subsidence as described in claim 1, characterized in that, The establishment of the coupling relationship between pore water pressure change and soil deformation using the Biot consolidation equation is as follows: Where M is the Biot modulus; For source and sink terms, negative values ​​are taken when pumping water; To satisfy Darcy's law for percolation flow.

5. The simulation experimental system for seawater intrusion and land subsidence as described in claim 1, characterized in that, The conductivity sensor array monitors the changes in water conductivity in real time, and converts the conductivity into an equivalent NaCl concentration based on a pre-established calibration relationship between conductivity and NaCl concentration, thereby determining the brackish water transition zone and interface location.

6. The simulation experimental system for seawater intrusion and land subsidence as described in claim 5, characterized in that, The determination of the brackish water transition zone and interface location specifically involves: Based on the pre-established calibration relationship between conductivity and NaCl concentration, the conductivity values ​​obtained by each conductivity sensor in real time are converted into the equivalent NaCl concentration at the corresponding location. Taking the freshwater end-member concentration and the 35 g / L NaCl saline end-member concentration as the benchmark, the area where the equivalent NaCl concentration is in the range of 10% to 90% of the saline end-member concentration is determined as the freshwater-saline transition zone, and the location corresponding to the equivalent NaCl concentration reaching 50% of the saline end-member concentration is determined as the freshwater-saline interface location.

7. A simulation experimental method for seawater intrusion and land subsidence, utilizing the simulation experimental system for seawater intrusion and land subsidence as described in any one of claims 1-6, characterized in that, include: Clay / silty clay and sand were layered and compacted in the main observation area. After the soil was filled, it was saturated with water and left to stand. A pore water pressure sensor, conductivity sensor, micrometer settlement gauge and pumping well were installed. Turn on both peristaltic pumps, control the freshwater side pump to supply water to the freshwater chamber, and the seawater side pump to supply water to the seawater chamber at a lower speed than the freshwater side. Observe the values ​​of each sensor until the system reaches a balanced state, which is recorded as the initial balanced state. Record the readings of all sensors. The pumping equipment is started to pump water from the pumping well at a constant rate, and the values ​​of the pore water pressure sensor, conductivity sensor, and micrometer sedimentation scale are monitored and recorded simultaneously to obtain the pore water pressure, conductivity and sedimentation. The changes in pore water pressure caused by pumping, the migration of the sea-sea interface, and the settlement of the top surface of the confined aquifer and the relative impermeable layer are calculated based on pore water pressure, conductivity, and settlement, thereby establishing the coupling relationship between changes in pore water pressure and soil deformation.

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