Physical simulation device and method for consolidation and compression ground surface settlement rule of loose aquifer

Abstract

The invention discloses a physical simulation device and method for a consolidation and compression ground surface settlement rule of an unconsolidated aquifer, and belongs to the technical field of optical fiber monitoring of rock-soil body deformation. The device comprises a test cylinder, a distributed optical fiber monitoring device, a water pumping and injecting device and a pressure measuring device, the distributed optical fiber monitoring device is connected with the test cylinder through an optical fiber and is used for measuring the longitudinal deformation quantity of each stratum in the seepage process; the water pumping and injecting device is connected with the test cylinder through a water guide pipe and used for simulating groundwater supply; the pressure measuring device is also connected with the test cylinder through a water guide pipe and is used for monitoring the internal water pressure change in the aquifer in the seepage process so as to obtain the water head variation in the aquifer; a dial indicator is arranged at the top of the test cylinder and used for measuring the longitudinal deformation of the model in the seepage process. By performing optical fiber monitoring on the test cylinder, simulating water injection or water pumping of the water-containing layer and recording corresponding data, the response characteristics of the loose water-containing layer under actual geological conditions can be effectively simulated and studied.

Description

Technical Field

[0001] The invention belongs to the technical field of optical fiber monitoring of rock and soil deformation, and in particular relates to a physical simulation device and method for the law of surface settlement of loose aquifer consolidation compression. Background Art

[0002] In some areas, mining areas are covered with thick loose layers with a thickness of more than 150m, and there is a confined aquifer at the bottom. The loose layer structure is four-containment and three-division. Long-term coal mining and groundwater extraction have led to a continuous decrease in the water head of the four-containment and three-containment. Studies have shown that water loss in confined aquifers in thick loose layer areas is one of the main reasons for its surface subsidence. Therefore, exploring the compression law, conduction law, and coordinated deformation law of the loose layer during the water loss of the confined aquifer is of great significance to realize the prediction of surface subsidence and ensure the safe production of coal mines.

[0003] The existing simulation device can only realize the study of the water loss compression law, conduction law, and coordinated surface settlement law of the loose layer under the drainage of a single confined aquifer. However, due to long-term coal mining and groundwater extraction in some mining areas, the fourth and third aquifers are losing water together, and surface precipitation will serve as a water source for the third aquifer.

[0004] In addition, traditional soil preparation techniques face many challenges in simulating complex underground environmental characteristics, such as loose layers with a thickness of more than 150 meters in some areas, complex and diverse aquifer distribution and soil properties. Traditional soil preparation methods are time-consuming and prone to errors in replicating the necessary fine stratigraphic details for accurate hydrogeological simulation. Summary of the invention

[0005] In view of the deficiencies in the prior art, the purpose of the present invention is to provide a physical simulation device and method for the surface settlement law of loose aquifer consolidation compression, which solves the problems in the prior art.

[0006] The purpose of the present invention can be achieved through the following technical solutions:

[0007] A physical simulation device for the surface settlement law of consolidation compression of loose aquifers comprises: a test cylinder, a distributed optical fiber monitoring device, a water pumping and injection device and a pressure measuring device; the distributed optical fiber monitoring device is connected to the test cylinder through optical fiber, and is used to measure the longitudinal deformation of each internal stratum during the seepage process; the water pumping and injection device is connected to the test cylinder through a water pipe, and is used to simulate groundwater recharge; the pressure measuring device is also connected to the test cylinder through the water pipe, and is used to monitor the change of internal water pressure in the aquifer during the seepage process, so as to obtain the change of water head in the aquifer; a dial indicator is also arranged on the top of the test cylinder, which is used to measure the longitudinal deformation of the model during the seepage process.

[0008] Furthermore, the test cylinder includes a cylindrical cylinder, which includes three small cylindrical cylinders distributed in sequence from top to bottom, and two adjacent small cylindrical cylinders are fixed by an intermediate connecting flange to achieve a detachable fixed connection; a top flange and a bottom tray are respectively arranged at the upper and lower ends of the cylindrical cylinder, and a water injection hole is arranged on the small cylindrical cylinder, the water injection hole can be connected to a water pipe, and the water injection hole can be sealed by a rubber plug; a porous plate is arranged at the lower part of the cylindrical cylinder, and a drainage hole is connected at the lower part of the porous plate.

[0009] Furthermore, two mutually perpendicular auxiliary cross bars are placed on the top of the columnar tube for hanging and fixing the optical fiber to keep the optical fiber in a vertical state.

[0010] Furthermore, an overflow hole tube is arranged on the central axis of the columnar tube, a plurality of through holes are opened on the outer surface of the lower end of the overflow hole tube, and the bottom of the overflow hole tube is open.

[0011] Furthermore, the outer wall of the test cylinder is provided with a millimeter scale, the pressure measuring device is provided with a millimeter scale, and the surface of the pressure measuring device is provided with a water pipe fixed in the vertical direction with hot melt adhesive.

[0012] The physical simulation method of the surface settlement law of the consolidation compression of the loose aquifer uses the above-mentioned physical simulation device of the surface settlement law of the consolidation compression of the loose aquifer, and comprises the following steps:

[0013] S1, based on the stratum distribution obtained from the actual engineering drilling data, the stratum is divided into four inclusions, three compartments and one surface;

[0014] S2, combining the existing loose layer mechanical parameters, selecting appropriate soil raw materials, and establishing the stratum physical model through 3D printing;

[0015] S3, installing the columnar tube, setting the fiber optic monitoring points, adding soil layers, laying the fiber optics and installing the dial indicator;

[0016] S4, connecting the columnar tube with the pressure measuring device and the water pumping and injection device by using a water pipe;

[0017] S5, replenishing water to the aquifer in the test soil column to make the aquifer reach a saturated state, and allowing the soil column to settle to a stable state;

[0018] S6, design injection and drainage plan: four-container drainage → three-container pumping → four-container water injection → three-container water injection.

[0019] S7, according to the injection and drainage plan, using the water pumping device to inject or pump water, and when implementing the injection and drainage plan, recording each group of data;

[0020] S8, analyze and process the optical fiber monitoring data, dial gauge data, and liquid column height data of the pressure measuring device to obtain the loose layer water loss compression law, conduction law, and coordinated deformation law with the surface.

[0021] Furthermore, the steps of establishing the physical model specifically include:

[0022] S21, selecting soil suitable for 3D printing according to the soil characteristics of the loose layer, and screening and washing;

[0023] S22, crushing and drying the screened and washed soil;

[0024] S23, mixing the crushed and dried soil with peat, calcium oxide and polyacrylic acid to improve creep properties;

[0025] S24, extrusion of soil mixture using 3D printer; need to ensure that the mixture can be pumped efficiently and solidifies quickly enough for subsequent deposition in the normal 3D printing sequence;

[0026] S25, after printing is completed, the 3D printed structure is cured, and then the porosity and permeability of the printed soil are tested in the laboratory.

[0027] 8. The physical simulation method for the surface settlement law of the consolidation and compression of loose aquifers according to claim 6 is characterized in that, in S3, when installing the columnar tube, a soil layer is added, and the soil layer is perforated so that the optical fiber can pass through, and the optical fiber is placed on the auxiliary cross bar and passes through the porous plate in the vertical direction, and then goes up to the auxiliary cross bar in the vertical direction, and the optical fiber is placed on the auxiliary cross bar in turn, and the optical fiber passing through the soil layer is kept in the plumb line direction; after the test columnar tube and the soil layer are installed, the overflow hole tube is inserted into the inside of the three-container, and a dial indicator is installed on the top of the soil layer.

[0028] Further, in S5, the step of making the test soil column reach a stable state includes:

[0029] S51, close the drain hole, use the pumping and injection device and control the water flow rate through the glass rotor flowmeter to intermittently inject water into the first, second, third and fourth containments at a small flow rate,

[0030] S52, let the soil column stand still and wait for the liquid column in the dial indicator and the pressure measuring device to stabilize.

[0031] S53, repeat S51 and S52. After water is injected and the soil column is left to stand, when the height of the liquid column in the pressure measuring device no longer decreases or remains stable, it means that the test soil column is stable and the aquifer has reached a saturated or oversaturated state. Record the elevation of each soil layer in the test column after it stabilizes, and record the height of the liquid column in the pressure gauge.

[0032] Furthermore, in S8, the collected distributed optical fiber monitoring data is based on the relationship between the axial strain and temperature of the optical fiber and the Brillouin frequency shift as follows:

[0033] v B (ε,T)=vB (0,T0)+D1ε+D2(T-T0)

[0034] In the formula, v B (ε,T) represents the drift of the fiber Brillouin frequency when the ambient temperature is T and the strain is ε; v B (0, T0) represents the drift of the fiber Brillouin frequency when the temperature is T0 and the strain is 0; D1 and D2 represent the proportionality coefficients of strain and temperature related to the fiber type, respectively.

[0035] Beneficial effects of the present invention:

[0036] 1. Improve monitoring accuracy and real-time performance: Through distributed optical fiber monitoring technology, the present invention can continuously and in real time monitor the micro-deformation inside the formation and the surface settlement, greatly improving the accuracy and real-time performance of the monitoring data.

[0037] 2. Accurate simulation of complex strata: Soil 3D printing technology can accurately reproduce the natural strata structure, including the physical and chemical properties of the soil, to ensure the representativeness of the experimental results.

[0038] 3. Shorten the experimental preparation time: 3D printed soil models can be prepared quickly, significantly reducing the experimental preparation time.

[0039] 4. Convenient observation and data collection: The structural design of the device takes into account the convenience of use and the need for data collection, such as transparent materials and easy-to-install monitoring equipment, so that every change in the experimental process can be intuitively observed and accurately recorded.

[0040] 5. The present invention combines distributed optical fiber monitoring technology with soil 3D printing technology to design a reasonable drainage and irrigation test method, which can effectively explore the internal deformation law of the aquifer, the conduction law of adjacent strata, and the coordinated surface settlement law when groundwater at different water levels migrates. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0042] Figure 1 This is an overall view of the physical simulation device for the surface settlement law of the loose aquifer consolidation compression of the present invention;

[0043] Figure 2 It is a schematic diagram of the small columnar tube structure in the physical simulation device for the surface settlement law of the loose aquifer consolidation compression of the present invention;

[0044] Figure 3 It is a schematic diagram of the structure of the test cylinder in the physical simulation device for the surface settlement law of the loose aquifer consolidation compression of the present invention;

[0045] Figure 4 It is a top view of a test cylinder in the physical simulation device for the surface settlement law of loose aquifer consolidation compression of the present invention;

[0046] Figure 5 It is a front view of the overflow hole pipe in the physical simulation device for the surface settlement law of the loose aquifer consolidation compression of the present invention;

[0047] Figure 6 It is a schematic front view of a pressure measuring device in a physical simulation device for the consolidation and compression of a loosely structured aquifer according to the present invention;

[0048] In the figure: 1-distributed optical fiber monitoring device, 2-water extraction and injection device, 3-test cylinder, 4-optical fiber, 5-water pipe, 6-pressure measuring device, 7-dial indicator, 8-top flange, 9-water injection hole, 10-middle connecting flange, 11-overflow hole pipe, 12-columnar cylinder, 13-bottom tray, 14-drainage hole, 15-millimeter scale, 16-threaded hole, 17-porous plate, 18-auxiliary cross bar, 20-small cylindrical cylinder. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] Example 1

[0051] like Figure 1 As shown, the physical simulation device for the surface settlement law of consolidation compression of loose aquifers comprises: a test tube 3, a distributed optical fiber monitoring device 1, a water pumping and injection device 2 and a pressure measuring device 6; the distributed optical fiber monitoring device 1 is connected to the test tube 3 through an optical fiber 4, and is used to measure the internal longitudinal deformation of each stratum during the seepage process; the water pumping and injection device 2 is connected to the test tube 3 through a water pipe 5, and is used to simulate groundwater recharge; the pressure measuring device 6 is also connected to the test tube 3 through the water pipe 5, and is used to monitor the internal water pressure change in the aquifer during the seepage process, so as to obtain the water head change in the aquifer; a dial gauge 7 is also arranged on the top of the test tube 3, and is used to measure the total longitudinal deformation of the stratum model during the seepage process.

[0052] like Figures 2 to 4As shown, the test tube 3 includes a cylindrical tube 12, and the cylindrical tube 12 includes three small cylindrical tubes 20 distributed in sequence from top to bottom. Two adjacent small cylindrical tubes 20 are fixed by an intermediate connecting flange 10 to achieve a detachable fixed connection; the upper and lower ends of the cylindrical tube 12 are respectively provided with a top flange 8 and a bottom tray 13, and the small cylindrical tube 20 is provided with a water injection hole 9, which can be connected to the water pipe 5, and the water injection hole 9 can be sealed by a rubber plug; the bottom of the cylindrical tube 3 is provided with a porous plate 17, and the bottom of the porous plate 17 is connected to the drainage hole 14;

[0053] Two mutually perpendicular auxiliary cross bars 18 are placed on the top of the columnar tube 3 to suspend and fix the optical fiber so that the optical fiber remains in a vertical state.

[0054] A water overflow hole 11 is arranged on the central axis of the cylindrical tube 3. Figure 5 As shown, a plurality of through holes are provided on the outer surface of the lower end of the overflow hole pipe 11 and the bottom of the overflow hole pipe 11 is open, so that the water in the aquifer can be gathered in the hole pipe under the internal pressure of the formation model to prevent the water from other aquifers from flowing into it. At the same time, the saturation degree of the aquifer can be judged according to the water level inside it, and a centralized water source can be provided for pumping water from the aquifer.

[0055] The outer wall of the test tube 3 is provided with a millimeter scale 15, which intuitively displays the position of the upper and lower boundaries of each stratum, so as to facilitate the installation of soil samples according to the stratum thickness design.

[0056] like Figure 6 As shown, the pressure measuring device 6 is provided with a millimeter scale 5, and the surface of the pressure measuring device 6 has a water pipe 5 fixed with hot melt adhesive along the vertical direction; in this embodiment, the material of the pressure measuring device 6 is organic glass, and its width, height and thickness are 1000×3000mm×5mm;

[0057] In this embodiment, the sealing performance is improved by a rubber ring between the intermediate connecting flanges 10, and a threaded hole 16 is provided on the intermediate connecting flange 10, and a detachable fixed connection is achieved by matching with mounting bolts.

[0058] In this embodiment, the columnar tube 12 is made of organic glass; the size of the small columnar tube 20 is height×diameter×wall thickness=1000mm×300mm×20mm.

[0059] In this embodiment, the measuring range of the dial gauge 7 is 10 mm, and the measuring accuracy is 0.01 mm.

[0060] Example 2

[0061] In this embodiment, based on the physical simulation device of the surface settlement law of consolidation compression of loose aquifer, a physical simulation method of the surface settlement law of consolidation compression of loose aquifer is proposed, which includes the following steps:

[0062] S1, based on the stratum distribution obtained from the actual engineering drilling data, the stratum is divided into four inclusions, three compartments and one surface;

[0063] S2, combining the existing loose layer mechanical parameters, selecting appropriate soil raw materials, and establishing the stratum physical model through 3D printing;

[0064] The steps to establish a physical model include:

[0065] S21, selecting soil suitable for 3D printing according to the soil characteristics of the loose layer, and screening and washing;

[0066] 1) The soil selection process includes:

[0067] Select soils rich in montmorillonite with high clay content, because these soils show better structural support and stability in 3D printing; prepare aquifer soil, use clay and sand, the addition of clay can simulate the clay component in natural soil and improve the water holding capacity of the printed object; prepare aquiclude soil, use clay, and select the binder water glass (sodium silicate solution) to improve the waterproofness of the clay after printing.

[0068] 2) The process of soil screening and washing is: screening and washing the collected soil to remove impurities and larger particles to ensure the fineness and purity of the soil.

[0069] S22, crushing and drying the screened and washed soil to increase the total surface area of ​​the material, promote chemical reaction, ensure uniformity of material mixing and smoothness of subsequent printing;

[0070] The process of soil crushing and drying is as follows:

[0071] 1) Mechanically crush the screened and washed soil to a certain particle size to increase the total surface area of ​​the material and promote subsequent chemical reactions;

[0072] 2) Dry the crushed soil in an oven to remove excess moisture and ensure the effectiveness of the chemical treatment.

[0073] S23, mixing the crushed and dried soil with an appropriate amount of peat, calcium oxide and polyacrylic acid (PAA) to improve creep properties;

[0074] Specifically, in aquifer soil, calcium oxide is added to reduce the adhesion between particles. This modification can improve the creep properties of the soil; peat is added to increase soil porosity; in aquiclude soil, polyacrylic acid (PAA) is added to provide good waterproofing effects while maintaining the softness of the soil, which is beneficial to the performance of creep properties.

[0075] S24, extrusion of soil mixture using 3D printer; need to ensure that the mixture can be pumped efficiently and solidifies quickly enough for subsequent deposition in the normal 3D printing sequence;

[0076] S25, after printing is completed, the 3D printed structure needs to be properly cured to achieve the required physical and mechanical properties; after that, the porosity and permeability of the printed soil are tested in the laboratory to ensure that it meets the requirements of the simulation test;

[0077] 1) The process of testing the porosity of printed soil is:

[0078] First, a soil sample of known volume was obtained by the ring knife method, and then dried and weighed to determine the bulk density. Then, the particle density was measured using the pycnometer method, and the porosity was finally calculated by the ratio of the bulk density to the particle density. The porosity ρ is expressed as:

[0079]

[0080] Where: b is the bulk density (volume mass) of the soil, usually expressed in g / cm 3 or kg / m 3 ρ B is the density of the soil particles, in the same units.

[0081] 2) The process of testing the permeability of printed soil is as follows:

[0082] Soil permeability is tested by constant head or variable head tests. In constant head tests, a fixed hydraulic head is maintained and the amount of water passing through the soil column is measured to calculate the permeability coefficient. Variable head tests are suitable for low permeability soils and evaluate soil permeability by measuring the change in hydraulic head over time.

[0083] The constant head permeability coefficient K can be calculated by the following formula:

[0084]

[0085] Q is the amount of water that passes through the soil sample in time t, usually in m 3 or L; L is the length of the soil sample, in m; A is the permeable area, in m 2 ; h is the head difference, the unit is m. t is the time, the unit is second.

[0086] S3, installing the columnar tube 3, setting the optical fiber monitoring point, adding the soil layer, laying the optical fiber and installing the dial indicator 7;

[0087] When installing the columnar tube 3, add a soil layer, perforate the soil layer so that the optical fiber can pass through, put the optical fiber on the auxiliary cross bar 18 and pass through the porous plate 17 in the vertical direction, then go up to the auxiliary cross bar 18 in the vertical direction, and put the optical fiber on the auxiliary cross bar 18 in turn, keeping the optical fiber passing through the soil layer in the direction of the plumb line; after the test columnar tube 3 and the soil layer are installed, insert the overflow hole tube 11 into the inside of the three-layer, and install the dial indicator 7 on the top of the soil layer.

[0088] In addition, vaseline is applied to the inner wall of the columnar tube 3, and the rubber ring is placed between adjacent middle connecting flanges 10 when installing the columnar tube 3. In order to obtain complete optical fiber monitoring data, a fiber optic Bragg grating strain sensor is set at 100mm, 700mm, 1680mm, 2150mm, 2380mm, 2620mm, and 2700mm from the bottom according to the design of different soil layer thicknesses, and the pressure measuring tube connector of the pressure measuring device 6 is at the same height as the fiber optic Bragg grating strain sensor.

[0089] S4, use the water pipe 5 to connect the columnar tube 3 with the pressure measuring device 6 and the water pumping and injection device 2.

[0090] The pressure measuring tube of the pressure measuring device 6 is a transparent glass tube with a height of 3000mm and an outer diameter of 12mm. One end of the water pipe 5 is plugged into the rubber plug on the water injection hole 9, and the other end is wrapped with polytetrafluoroethylene tape to increase the airtightness and prevent the pressure measuring tube from leaking and affecting the accuracy of the test data. After the pressure measuring tube is filled with water, add an appropriate amount of blue or red ink for observation and recording;

[0091] S5, replenish water to the aquifer in the test soil column to make the aquifer reach saturation state, and let the soil column stand until it reaches a stable settlement state.

[0092] The steps to achieve a stable state for the test soil column include:

[0093] S51, close the drain hole 14, use the pumping and injection device 2 and control the water flow rate through the glass rotor flowmeter to intermittently inject water into the first, second, third and fourth containments at a small flow rate,

[0094] S52, let the soil column stand still and wait for the liquid column in the dial gauge 7 and the pressure measuring device 6 to stabilize.

[0095] S53, repeat steps S51 and S52. After water is injected and the soil column is left stationary, when the height of the liquid column in the pressure measuring device 6 no longer decreases or remains stable, it means that the test soil column is stable and the aquifer has reached a saturated or oversaturated state. Record the elevation of each soil layer in the test column after it stabilizes, and record the height of the liquid column in the pressure gauge.

[0096] S6, design injection and drainage plan: four-container drainage → three-container pumping → four-container water injection → three-container water injection.

[0097] The detailed operation steps of the injection and drainage scheme are as follows:

[0098] 1) Open the bottom drain hole 14;

[0099] 2) Close the bottom drainage hole 14, and use the pumping and injection device 2 to extract the three water through the overflow hole pipe 11;

[0100] 3) Use the pumping and injection device 2 to inject water through the injection hole 9 at the location of the four-container

[0101] 4) using the water injection device 2 to inject water through the water injection hole 9 at the location of the three-container;

[0102] 5) Repeat the cycle from step 1) to step 4).

[0103] S7, according to the injection and drainage plan, use the water pumping device 2 to inject or pump water, and record each group of data when implementing the injection and drainage plan.

[0104] The recorded data groups include: water discharge and replenishment of the bottom four aquifers, water pumping and replenishment of the three aquifers, distributed optical fiber monitoring data, height of liquid column corresponding to each aquifer in the pressure measuring device, and dial indicator readings.

[0105] During the implementation of the injection and drainage plan, the liquid column in the pressure measuring device changes rapidly when the injection and drainage are just completed, so the recording frequency needs to be increased to once every 5 to 10 minutes. As time goes by, the recording time interval should be appropriately extended.

[0106] S8. Analyze and process the optical fiber monitoring data, dial gauge data, and liquid column height data of the pressure measuring device to obtain the loose layer water loss compression law, conduction law, and coordinated deformation law with the surface.

[0107] The collected distributed optical fiber monitoring data is based on the relationship between the axial strain and temperature of the optical fiber and the Brillouin frequency shift:

[0108] v B (ε,T)=v B (0,T0)+D1ε+D2(T-T0)

[0109] In the formula, v B (ε,T) represents the drift of the fiber Brillouin frequency when the ambient temperature is T and the strain is ε; v B (0, T0) represents the drift of the fiber Brillouin frequency when the temperature is T0 and the strain is 0; D1 and D2 represent the proportionality coefficients of strain and temperature related to the fiber type, respectively.

[0110] The dial gauge data reflects the change of top displacement with water level and time. By measuring the reading of the dial gauge when the water level changes, the longitudinal deformation of the model during the seepage process is measured. The height of each liquid column in the pressure measuring device reflects the change of the corresponding aquifer head through the internal hydraulic pressure of the soil column aquifer.

[0111] In the description of this specification, the description with reference to the terms "one embodiment", "example", "specific example", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0112] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments, and the above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, and these changes and improvements all fall within the scope of the present invention to be protected.

Claims

1. Physical simulation device for surface settlement law of loose aquifer consolidation compression, characterized in that: include: A test cylinder (3), a distributed optical fiber monitoring device (1), a water pumping and injection device (2), and a pressure measuring device (6); the distributed optical fiber monitoring device (1) is connected to the test cylinder (3) via an optical fiber (4) and is used to measure the longitudinal deformation of each internal layer during the seepage process; the water pumping and injection device (2) is connected to the test cylinder (3) via a water pipe (5) and is used to simulate groundwater recharge; the pressure measuring device (6) is also connected to the test cylinder (3) via the water pipe (5) and is used to monitor the change in internal water pressure in the aquifer during the seepage process, thereby obtaining the change in water head in the aquifer; a dial gauge (7) is also provided on the top of the test cylinder (3) and is used to measure the longitudinal deformation of the model during the seepage process.

2. The physical simulation device for the surface settlement law of loose aquifer consolidation compression according to claim 1 is characterized in that: The test tube (3) comprises a columnar tube (12), wherein the columnar tube (12) comprises three small columnar tubes (20) arranged in sequence from top to bottom, and two adjacent small columnar tubes (20) are fixed via an intermediate connecting flange (10) to achieve a detachable fixed connection; a top flange (8) and a bottom tray (13) are respectively arranged at the upper and lower ends of the columnar tube (12), and a water injection hole (9) is arranged on the small columnar tube (20), and the water injection hole (9) can be connected to a water pipe (5), and the water injection hole (9) can be sealed by a rubber plug; a porous plate (17) is arranged at the lower part of the columnar tube (3), and a drainage hole (14) is connected at the lower part of the porous plate (17).

3. The physical simulation device for the surface settlement law of loose aquifer consolidation compression according to claim 2 is characterized in that: Two mutually perpendicular auxiliary cross bars (18) are placed on the top of the columnar tube (3) for hanging and fixing the optical fiber so that the optical fiber remains in a vertical state.

4. The physical simulation device for the surface settlement law of loose aquifer consolidation compression according to claim 3 is characterized in that: A water overflow hole tube (11) is arranged on the central axis of the columnar tube (3), a plurality of through holes are provided on the outer surface of the lower end of the water overflow hole tube (11), and the bottom of the water overflow hole tube (11) is open.

5. The physical simulation device for the surface settlement law of loose aquifer consolidation compression according to claim 4 is characterized in that: The outer wall of the test cylinder (3) is provided with a millimeter scale (15), the pressure measuring device (6) is provided with a millimeter scale (15), and the surface of the pressure measuring device (6) is provided with a water pipe (5) fixed in the vertical direction by hot melt adhesive.

6. A physical simulation method for the law of consolidation and compression of loose aquifer surface settlement, using the physical simulation device for the law of consolidation and compression of loose aquifer surface settlement as claimed in claim 5, characterized in that: The following steps are involved: S1, based on the stratum distribution obtained from the actual engineering drilling data, the stratum is divided into four inclusions, three compartments and one surface; S2, combining the existing loose layer mechanical parameters, selecting appropriate soil raw materials, and establishing the stratum physical model through 3D printing; S3, installing the columnar tube (3), setting the optical fiber monitoring point, adding the soil layer, laying the optical fiber and installing the dial indicator (7); S4, using a water pipe (5) to connect the columnar tube (3) with the pressure measuring device (6) and the water pumping and injection device (2); S5, replenishing water to the aquifer in the test soil column to make the aquifer reach a saturated state, and allowing the soil column to settle to a stable state; S6, design injection and drainage plan: four-container drainage → three-container pumping → four-container water injection → three-container water injection. S7, according to the injection and drainage plan, using the water pumping device (2) to inject or pump water, and when implementing the injection and drainage plan, recording each set of data; S8, analyze and process the optical fiber monitoring data, dial gauge data, and liquid column height data of the pressure measuring device to obtain the loose layer water loss compression law, conduction law, and coordinated deformation law with the surface.

7. The physical simulation method for surface settlement law of loose aquifer consolidation compression according to claim 6 is characterized in that: The steps to establish a physical model include: S21, selecting soil suitable for 3D printing according to the soil characteristics of the loose layer, and screening and washing; S22, crushing and drying the screened and washed soil; S23, mixing the crushed and dried soil with peat, calcium oxide and polyacrylic acid to improve creep properties; S24, extrusion of soil mixture using 3D printer; need to ensure that the mixture can be pumped efficiently and solidifies quickly enough for subsequent deposition in the normal 3D printing sequence; S25, after printing is completed, the 3D printed structure is cured, and then the porosity and permeability of the printed soil are tested in the laboratory.

8. The physical simulation method for surface settlement law of loose aquifer consolidation compression according to claim 6 is characterized in that: In S3, when installing the columnar tube (3), a soil layer is added, and the soil layer is perforated so that the optical fiber can pass through. The optical fiber is placed on the auxiliary cross bar (18) and passes through the porous plate (17) in the vertical direction, and then goes up to the auxiliary cross bar (18) in the vertical direction, and the optical fiber is placed on the auxiliary cross bar (18) in turn, and the optical fiber passing through the soil layer is kept in the direction of the plumb line; after the test columnar tube (3) and the soil layer are installed, the overflow hole tube (11) is inserted into the inside of the three-layer, and a dial indicator (7) is installed on the top of the soil layer.

9. The physical simulation method for surface settlement law of loose aquifer consolidation compression according to claim 6 is characterized in that: In S5, the step of making the test soil column reach a stable state includes: S51, close the drain hole (14), use the pumping and injection device (2) and control the water flow rate through the glass rotor flowmeter to intermittently inject water at a small flow rate into the first containment, the second containment, the third containment and the fourth containment, S52, leaving the soil column still until the liquid column in the dial gauge (7) and the pressure measuring device (6) is stable. S53, repeat S51 and S52. After water is injected and the soil column is left to stand, when the height of the liquid column in the pressure measuring device (6) no longer decreases or remains stable, it means that the test soil column is stable and the aquifer has reached a saturated or oversaturated state. Record the elevation of each soil layer in the test column after it stabilizes, and record the height of the liquid column in the pressure gauge.

10. The physical simulation method for surface settlement law of loose aquifer consolidation compression according to claim 6 is characterized in that: In S8, the collected distributed optical fiber monitoring data is based on the relationship between the axial strain and temperature of the optical fiber and the Brillouin frequency shift: v B (ε,T)=v B (0,T0)+D1ε+D2(T-T0) In the formula, v B (ε,T) represents the drift of the fiber Brillouin frequency when the ambient temperature is T and the strain is ε; v B (0, T0) represents the drift of the fiber Brillouin frequency when the temperature is T0 and the strain is 0; D1 and D2 represent the proportionality coefficients of strain and temperature related to the fiber type, respectively.

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