Testing device and method for simulating internal erosion of seawall soil body under circulating hydraulic gradient

Abstract

The invention discloses a test device and method for simulating internal erosion of a seawall soil body under a circulating hydraulic gradient. The device comprises a circulating hydraulic gradient generation system, an internal erosion triaxial test system and an automatic soil-water separation measurement system, the circulating hydraulic gradient generation system provides a circulating water head capable of changing along with time under different elevations, the internal erosion triaxial test system provides confining pressure and axial pressure, and an internal erosion test and an eroded soil body triaxial shear test can be carried out. The automatic soil-water separation measuring system can automatically separate and weigh soil particles and water in real time in the internal erosion process, the mass of soil particles lost by the test soil sample and the mass of seepage water can be converted through a mathematical formula, and real-time monitoring of the erosion damage process is achieved. The internal erosion test under the circulating hydraulic gradient under different elevations can be realized, the mass and volume of fine particle loss generated by erosion damage can be continuously measured and calculated, and the erosion damage process can be monitored in real time.

Description

Technical Field

[0001] The invention relates to the technical field of water conservancy engineering soil penetration damage test, in particular to a test device and method for simulating internal erosion of seawall soil under cyclic hydraulic gradient. Background Art

[0002] Earthen seawalls are protective structures constructed of materials such as clay, sand and gravel. However, under extreme natural disaster conditions such as typhoon storm surges, earthen seawall collapses frequently, and these damages are mostly related to internal erosion. Internal erosion refers to the seepage deformation phenomenon in which fine particles in the soil move under the action of seepage, causing changes in the soil structure. In this process, the hydraulic properties of the seawall soil change, leading to local or overall damage under seepage-stress coupling. Therefore, how to simulate the internal erosion process of earthen seawalls and accurately describe the impact of internal erosion on the hydraulic properties of seawall soil is of great significance to the safe operation of earthen seawalls.

[0003] Earthen seawalls are affected by complex hydraulic gradients due to fluctuations in water levels or waves, but current research focuses on internal erosion of soil under fixed hydraulic gradients. Experimental research on internal erosion of soil under cyclic hydraulic gradients is very limited, and the mechanism of this erosion is still poorly understood. The main reason is the lack of specialized experimental equipment, and the difficulty lies in effectively simulating the periodic fluctuations of water levels at different elevations.

[0004] In addition, in the existing erosion test, when collecting soil water for discontinuous graded soil, the traditional method of collecting and weighing the mass of the seeped soil particles is the drying method. Since the newly collected erosion products are turbid, they need to be left to stand first, and then the clear water on the particles is slowly poured out, and then the collected soil particles at the bottom of the cup are dried, and finally the mass is weighed. This collection method has complex steps, is time-consuming, has large errors, and cannot achieve continuous real-time measurement. Summary of the invention

[0005] The purpose of the present invention is to provide a test device and method for simulating the internal erosion of seawall soil under cyclic hydraulic gradient, so as to solve the problems existing in the above-mentioned prior art. It can realize the internal erosion test under cyclic hydraulic gradient at different elevations, and can continuously measure and calculate the mass and volume of fine particle loss caused by erosion damage, so as to realize real-time monitoring of the erosion damage process.

[0006] To achieve the above object, the present invention provides the following solutions:

[0007] The present invention provides a test device for simulating the internal erosion of seawall soil under cyclic hydraulic gradient, comprising a cyclic hydraulic gradient generating system, an internal erosion triaxial test system and an automatic soil-water separation measurement system;

[0008] The circulating hydraulic gradient generating system comprises a fixed bracket, a screw bracket, a screw module, a stepping motor, a stepping driver, a controller, a lifting drive device, a water storage cylinder and a water outlet pipe. The two ends of the screw module are each connected to a screw bracket, and two screw brackets are vertically slidably arranged on the fixed bracket. The screw bracket is connected to the lifting drive device and driven to move up and down by the lifting drive device. The water storage cylinder is fixed on the slider of the screw module, one end of the water outlet pipe is connected to the water storage cylinder, and the other end is connected to the top water inlet of the internal erosion triaxial test system. The screw module is connected to the stepping motor and driven by the stepping motor to realize the up and down movement of the slider. The stepping motor is connected to the stepping driver, and the stepping driver is connected to the controller. The controller controls the operation of the stepping motor through the stepping driver to drive the slider and the water storage cylinder to move up and down periodically along the screw of the screw module, so as to provide a circulating water head that can change with time.

[0009] The automatic soil-water separation measurement system includes a soil-water separation device and a first weighing device. The soil-water separation device includes a soil-water separation cylinder and a filter. The soil-water separation cylinder is placed on the first weighing device. The lower side feed port of the soil-water separation cylinder is connected to the bottom discharge port of the internal erosion triaxial test system through a discharge pipeline. A separation cylinder outlet pipe is provided on the upper side of the soil-water separation cylinder. The filter is arranged in the soil-water separation cylinder and is located between the feed port and the separation cylinder outlet pipe.

[0010] Preferably, the automatic soil-water separation measurement system further comprises a water collecting device and a second weighing device, the water collecting device comprises a water collecting tank, the water collecting tank is placed on the second weighing device, and the outlet of the separation cylinder water outlet pipe leads to the water collecting tank.

[0011] Preferably, the lifting drive device includes a winch, a wire rope and a pulley, the winch is fixed to the bottom of the fixed bracket, the pulley is installed on the top of the fixed bracket, one end of the wire rope is wound around and connected to the winch, and the other end passes around the pulley and is connected to the screw bracket at the upper end.

[0012] Preferably, the circulating hydraulic gradient generating system also includes a water tank, a water pump and a power supply. The water pump is arranged in the water tank and connected to the water storage cylinder through a water inlet pipe. The power supply provides electrical energy to the stepper motor, the stepper driver, the controller and the water pump.

[0013] Preferably, the filter screen is detachably connected to the soil-water separation cylinder by bolts.

[0014] Preferably, the internal erosion triaxial test system includes a pressure sensor, a displacement sensor, an axial pressure loading rod, a sample cap, a pressure chamber, a pressure chamber base and an instrument frame, the pressure chamber is used to hold the sample, the sample cap is placed in the pressure chamber and located on the top of the sample, the upper water inlet of the sample cap is connected to the water outlet pipe, the pressure chamber base is arranged at the bottom of the pressure chamber, and a funnel-shaped discharge port is provided on the pressure chamber base, the axial pressure loading rod is arranged at the upper end of the pressure chamber, the lower end of the axial pressure loading rod is used to abut against the upper end of the sample cap, the upper part of the axial pressure loading rod is connected to the pressure sensor and the displacement sensor, and the pressure sensor and the displacement sensor are connected to the upper end of the instrument frame.

[0015] Preferably, a porous water-permeable plate is provided on the top and bottom of the sample in the pressure chamber, respectively, and filter paper is provided between the porous water-permeable plate on the top and the sample cap.

[0016] Preferably, the first weighing device and the second weighing device are electronic balances; and four groups of supporting angle brackets are connected around the bottom of the fixed bracket.

[0017] The present invention also provides a test method for simulating the internal erosion of seawall soil under cyclic hydraulic gradient, based on the test device for simulating the internal erosion of seawall soil under cyclic hydraulic gradient described above, comprising the following steps:

[0018] placing a simulated seawall soil sample in a pressure chamber of the internal erosion triaxial test system;

[0019] The circulating hydraulic gradient generating system provides a circulating water head that changes with time at different elevations;

[0020] Water flows into the pressure chamber from the top of the sample, and the water flowing through the sample and the fine particles eroded are discharged through the outlet at the bottom of the sample to simulate the erosion process;

[0021] The seepage water carrying fine particles enters the soil-water separation device for soil-water separation and is weighed in real time by the first weighing device; the excess water is discharged from the top of the soil-water separation cylinder through the separation cylinder outlet pipe into the water collecting tank and is weighed in real time by the second weighing device;

[0022] Calculate the mass and volume of the fine particles by formulas according to the readings of the first weighing device;

[0023] After the soil and water separation is completed, close the erosion outlet valve, perform axial pressure loading according to stress or strain mode, and conduct triaxial test on the sample while keeping the confining pressure of the sample unchanged.

[0024] Preferably, the calculation method of fine particle mass and volume is as follows:

[0025] When the test time is t1, the total mass measured by the first weighing device is read as M A1 , its mathematical expression is:

[0026] M A1 =M g +M w1 +M s1 =M g +ρ w (VV s1 )+ρ s V s1 (1.1),

[0027] Where M g is the mass of the water-soil separation device; M w1 is the mass of water in the soil-water separation cylinder at time t1; M s1 is the mass of the soil in the soil-water separation cylinder at time t1; V is the volume of the soil-water separation cylinder; V s1 is the volume of soil in the soil-water separation cylinder at time t1; ρ w is the density of water; ρ s is the density of soil;

[0028] When the test time is t2, the total mass measured by the first weighing device is read as M A2 , its mathematical expression is:

[0029] M A2 =M g +M w2 +M s2 =M g +ρ w (VV s2 )+ρ s V s2 (1.2),

[0030] Where M w2 is the mass of water in the soil-water separation cylinder at time t2; M s2 V is the mass of soil in the soil-water separation cylinder at time t2; s2 is the volume of soil in the soil-water separation cylinder at time t2;

[0031] By subtracting formula (1.1) from formula (1.2), we can get:

[0032]

[0033] Where ΔV s is the volume of soil collected in the water-soil separation device during the period t1 to t2; m s It is the mass of soil collected in the water-soil separation device during the time period from t1 to t2.

[0034] Preferably, the seepage water mass m w The calculation method is as follows:

[0035] When the test time is t1, the total mass measured by the second weighing device is read as M B1 When the test time is t2, the total mass measured by the second weighing device is read as M B2 , the mass of seepage water in the time period t1 to t2 is m w for:

[0036] m w =M B2 -M B1 -ρ W ΔV S (1.5).

[0037] Compared with the prior art, the present invention has achieved the following technical effects:

[0038] The present invention provides a test device and method for simulating the internal erosion of the seawall soil under a cyclic hydraulic gradient. The cyclic hydraulic gradient generating system controls the stepping motor to drive the screw to rotate through a controller to realize the periodic up and down movement of the water storage cylinder on the screw. The cyclically moving water storage cylinder is connected to the upper part of the soil sample, and the lower part of the soil sample is connected to the atmosphere, thereby forming a cyclic hydraulic gradient inside the soil sample, simulating the periodic change of the hydraulic gradient in the seawall soil under the action of waves. The internal erosion triaxial test system can set different confining pressures and axial pressures to simulate the stress state of the soil sample, and realize the simulation of the internal erosion process of the soil sample under different stress states. The internal erosion triaxial test system can perform triaxial shear tests on the sample to test the mechanical properties of the soil before and after internal erosion, so as to intuitively study the degradation effect of internal erosion on the mechanical properties of the soil. The automatic soil-water separation measurement system can continuously measure and calculate the mass and volume of fine particle loss caused by erosion damage through the readings of the first weighing device, and realize real-time monitoring of the erosion damage process.

[0039] Furthermore, a funnel-shaped discharge port is provided on the base of the triaxial pressure chamber, so that the friction resistance of the eroded soil-water mixture can be further reduced when passing through the funnel-shaped discharge port.

[0040] Placing filter paper and a porous permeable plate under the sample cap in sequence can effectively avoid seepage concentration during the test, allow the seepage water to infiltrate evenly, and improve the test reliability.

[0041] The soil-water separation cylinder is provided with a filter which can be disassembled and replaced by bolts. The filter can be replaced regularly to prevent clogging. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] 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 will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0043] Figure 1 It is a front view of a test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient in an embodiment of the present invention;

[0044] Figure 2 It is a structural schematic diagram of a circulating hydraulic gradient generating system in an embodiment of the present invention;

[0045] Figure 3 It is a structural schematic diagram of an internal corrosion triaxial test system in an embodiment of the present invention;

[0046] Figure 4 It is a structural schematic diagram of the automatic soil-water separation measurement system in an embodiment of the present invention.

[0047] In the figure: Ⅰ-circulating hydraulic gradient generation system, Ⅱ-internal erosion triaxial test system, Ⅲ-automatic soil-water separation measurement system, 1-water storage tank, 2-water pump, 3-water inlet pipe, 4-fixed bracket, 5-pulley, 6-winch, 7-wire rope, 8-hook, 9-screw bracket, 10-linear bearing, 11-screw module, 12-water storage cylinder, 13-stepping motor, 14-power supply, 15-stepping driver, 16-controller, 17-water outlet pipe, 18- Pressure sensor, 19-displacement sensor, 20-pressure chamber, 21-axial pressure loading rod, 22-sample cap, 23-top porous water-permeable plate, 24-pressure chamber base, 25-bottom porous water-permeable plate, 26-discharge pipeline, 27-feed port, 28-first weighing device, 29-filter screen, 30-soil-water separation cylinder, 31-bolt, 32-separation cylinder outlet pipe, 33-second weighing device, 34-water collecting tank, 35-instrument stand, 36-support angle bracket. DETAILED DESCRIPTION

[0048] 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.

[0049] The purpose of the present invention is to provide a test device and method for simulating the internal erosion of seawall soil under cyclic hydraulic gradient, so as to solve the problems existing in the prior art. The internal erosion test under cyclic hydraulic gradient at different elevations can be realized, and the mass and volume of fine particle loss caused by erosion damage can be continuously measured and calculated, so as to realize real-time monitoring of the erosion damage process.

[0050] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0051] Embodiment 1

[0052] like Figure 1-Figure 4 As shown, this embodiment provides a test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient, including a cyclic hydraulic gradient generating system I, an internal erosion triaxial test system II and an automatic soil-water separation measurement system III; the cyclic hydraulic gradient generating system I provides a cyclic water head that can change sinusoidally with time and other cyclic water heads that change complexly with time, the internal erosion triaxial test system II provides confining pressure and axial pressure, and can perform internal erosion tests and triaxial shear tests on soil after erosion, and the automatic soil-water separation measurement system III can automatically separate and weigh soil particles and water in real time during the internal erosion process;

[0053] The circulating hydraulic gradient generating system I comprises a fixed bracket 4, a screw bracket 9, a screw module 11, a stepping motor 13, a stepping driver 15, a controller 16, a lifting drive device, a water storage cylinder 12 and a water outlet pipe 17. The two ends of the screw module 11 are respectively connected to a screw bracket 9, and the two screw brackets 9 are vertically slidably arranged on the fixed bracket 4. The screw bracket 9 is connected to the lifting drive device and is driven to move up and down by the lifting drive device; the water storage cylinder 12 is fixed on the slider of the screw module 11, one end of the water outlet pipe 17 is connected to the bottom of the water storage cylinder 12, and the other end is connected to the top water inlet of the internal erosion triaxial test system II; the screw module 11 is connected to the stepping drive device. The stepper motor 13 is connected to the stepper driver 15, and the stepper driver 15 is connected to the controller 16. The controller 16 controls the operation of the stepper motor 13 through the stepper driver 15 to drive the slider and the water storage cylinder 12 to make periodic up and down movements along the screw of the screw module 11, so as to provide a circulating water head that can change with time. The circulating water storage cylinder 12 is connected to the upper part of the soil sample through the outlet pipe 17, and the lower part of the soil sample is connected to the atmosphere, so as to form a circulating hydraulic gradient inside the soil sample, simulating the periodic changes of the hydraulic gradient in the seawall soil under the action of waves;

[0054] The automatic soil-water separation measurement system III includes a soil-water separation device and a first weighing device 28. The soil-water separation device includes a soil-water separation cylinder 30 and a filter screen 29. The soil-water separation cylinder 30 is placed on the first weighing device 28. The lower feed port 27 of the soil-water separation cylinder 30 is connected to the bottom discharge port of the internal erosion triaxial test system II through the discharge pipeline 26. The upper side of the soil-water separation cylinder 30 is provided with a separation cylinder outlet pipe 32. The filter screen 29 is arranged in the soil-water separation cylinder 30 and is located between the feed port 27 and the separation cylinder outlet pipe 32. The main body of the soil-water separation cylinder 30 is made of acrylic plates bonded together. The soil-water separation cylinder 30 is provided with a filter screen 29 that can be disassembled and replaced by bolts 31. The filter screen 29 is a fine filter screen with an aperture of about 29 μm. The separation cylinder outlet pipe 32 is arranged at the top of the soil-water separation cylinder 30 in an inclined structure.

[0055] In this embodiment, the automatic soil-water separation measurement system III also includes a water collection device and a second weighing device 33. The water collection device includes a water collection box 34, which is made of acrylic plates bonded together. The water collection box 34 is placed on the second weighing device 33, and the bottom outlet of the separation cylinder water outlet pipe 32 leads to the water collection box 34. The soil-water mixture passes through the fine filter in the soil-water separation cylinder 30 to achieve soil-water separation. The eroded fine particles are filtered by the fine filter and deposited at the bottom of the soil-water separation cylinder 30. The excess water is discharged into the water collection box 34 through the separation cylinder water outlet pipe 32.

[0056] In this embodiment, the lifting drive device includes a winch 6, a wire rope 7 and a pulley 5. The winch 6 is fixed to the bottom of the fixed bracket 4, and the pulley 5 is installed on the top of the fixed bracket 4. One end of the wire rope 7 is wound around the winch 6, and the other end passes around the pulley 5 and is connected to the screw bracket 9 at the upper end through a hook.

[0057] In this embodiment, the circulating hydraulic gradient generating system I also includes a water tank 1, a water pump 2 and a power supply 14. The water pump 2 is arranged in the water tank 1. The water pump 2 is connected to the water storage cylinder 12 through the water inlet pipe 3, and water is supplied to the water storage cylinder 12 through the water pump 2 and the water inlet pipe 3; the power supply 14 provides electric energy for the stepper motor 13, the stepper driver 15, the controller 16 and the water pump 2. The stepper driver 15 is connected to the stepper motor 13, the power supply 14 and the controller 16 through the line. The program is set by the controller 16 to realize the periodic up and down movement of the water storage cylinder 12 on the 1.5-meter screw rod, thereby realizing the provision of water heads under different height differences and circulating water heads that can change over time.

[0058] In this embodiment, the internal erosion triaxial test system II includes a triaxial pressure chamber, a confining pressure system and a water supply system. Specifically, it includes a pressure sensor 18, a displacement sensor 19, an axial pressure loading rod 21, a sample cap 22, a pressure chamber 20, a pressure chamber base 24 and an instrument stand 35. The pressure chamber 20 is used to hold the sample, and the sample is set in the middle of the pressure chamber 20 to hold the simulated seawall soil sample. The sample cap 22 is placed in the pressure chamber 20 and is located at the top of the sample. Its diameter is slightly larger than the sample diameter. The upper water inlet of the sample cap 22 is connected to the outlet pipe 17 of the circulating hydraulic gradient generating system I, and the lower part of the soil sample is connected to the atmosphere, thereby forming a circulating hydraulic gradient inside the soil sample to simulate the hydraulic gradient in the seawall soil under the action of waves. The pressure chamber base 24 is arranged at the bottom of the pressure chamber 20, and a funnel-shaped discharge port is arranged on the pressure chamber base 24. The discharge port is connected to the feed port 27 of the soil-water separation cylinder 30 through a discharge pipe 26 (using a hose). The axial pressure loading rod 21 is arranged at the upper end of the pressure chamber 20. The lower end of the axial pressure loading rod 21 is used to abut against the upper end of the sample cap 22. The upper part of the axial pressure loading rod 21 is connected to the pressure sensor 18 and the displacement sensor 19, which are used to receive and transmit pressure signals and record the deformation of the sample in axial displacement in real time. The pressure sensor 18 and the displacement sensor 19 are connected to the upper end of the instrument frame 35. The system can set different confining pressures and axial pressures to simulate the stress state of the soil sample, realize the simulation of the internal erosion process of the soil sample under different stress states, and can perform triaxial shear tests on the sample to test the mechanical properties of the soil before and after internal erosion.

[0059] In this embodiment, a porous water-permeable plate is provided at the top and bottom of the sample in the pressure chamber 20, namely a top porous water-permeable plate 23 and a bottom porous water-permeable plate 25. Filter paper is provided between the top porous water-permeable plate 23 and the sample cap 22, which can effectively avoid seepage concentration during the test, make the seepage water infiltrate evenly, and improve the reliability of the test.

[0060] In this embodiment, the fixed bracket 4 is mainly welded from Q235A steel, including four 6-meter-long steel pipe frames. Four groups of support angle brackets 36 are connected around the bottom of the fixed bracket 4 to stabilize the entire device and prevent it from falling over. The screw bracket 9 is made of steel structure. The screw bracket 9 is sleeved on the four 6-meter steel pipes of the fixed bracket 4. The two are connected by a linear bearing 10 to enable the screw bracket 9 to move up and down on the fixed bracket 4. A hanging nose is welded on the top screw bracket 9, and the hook 8 passes through the hanging nose and is connected to the wire rope 7. In this way, the screw bracket 9 can move up and down under the action of the winch 6 and the pulley 5. Such a design can effectively realize the circulation head adjustment under different elevation heads.

[0061] In this embodiment, the first weighing device 28 and the second weighing device 33 are electronic balances with an accuracy of 0.01 g. The soil-water separation cylinder 30 is filled with water and the balance reading is read before the experiment begins, and its initial mass filled with water is recorded. Then, the soil and water mixture flows into the soil-water separation cylinder 30, and then the electronic balance reading is read at each time interval, so that the mass of eroded fine particles and outflowing water can be calculated by a formula.

[0062] Embodiment 2

[0063] This embodiment provides a test method for simulating the internal erosion of seawall soil under cyclic hydraulic gradient. Based on the test device for simulating the internal erosion of seawall soil under cyclic hydraulic gradient described in Embodiment 1, before starting the experiment, the soil-water separation cylinder 30 is filled with water and the reading of the first weighing device 28 is read to record the initial mass filled with water. Then the soil and water mixture flows into the soil-water separation cylinder 30, and then the electronic balance reading is read at each time interval, so as to calculate the mass of eroded fine particles and outflowing water by formula;

[0064] The specific steps include:

[0065] The simulated seawall soil sample is placed in a triaxial transparent organic glass pressure chamber 20 of the internal erosion triaxial test system II, and the confining pressure environment is simulated by the confining pressure system and the water supply system;

[0066] The circulating hydraulic gradient generating system I provides a circulating water head that changes sinusoidally with time at different elevations and other circulating water heads that change complexly with time; the principle is: the screw module 11 is positioned at different elevations through the steel wire rope 7, the winch 6 and the pulley 5, and the screw module 11 is set to a rotation mode (including: uniform rotation, accelerated rotation, decelerated rotation, forward rotation, reverse rotation, etc.) through the controller 16 to achieve the water storage cylinder 12 to make periodic up and down movements on the screw, thereby achieving the provision of water heads at different height differences and circulating water heads that can change sinusoidally with time and other circulating water heads that change complexly with time;

[0067] Water flows through the sample cap 22 in the pressure chamber 20 and penetrates from the top of the sample. The water flowing through the sample and the fine particles eroded are discharged through the outlet at the bottom of the sample to simulate the erosion process.

[0068] During the erosion process of the sample, the seepage water carrying fine particles enters the water-soil separation device for soil-water separation, and is weighed in real time by the first weighing device 28; the filter screen 29 can prevent fine soil particles from passing through, thereby achieving the soil-water separation effect; the excess water is discharged from the top of the soil-water separation cylinder 30 through the separation cylinder outlet pipe 32 to the water collecting tank 34, and is weighed in real time by the second weighing device 33; the mass, volume and seepage water mass of the fine particles can be calculated by formulas according to the readings of the first weighing device 28 and the second weighing device 33 (electronic balance);

[0069] After the soil-water separation is completed, the outlet valve of the pressure chamber base 24 is closed, and axial pressure loading is performed in the stress or strain mode, and the triaxial test of the sample is performed while keeping the confining pressure of the sample unchanged.

[0070] The calculation method of fine particle mass and volume is as follows:

[0071] When the test time is t1, the total mass measured by the first weighing device 28 is read as M A1 , its mathematical expression is:

[0072] M A1 =M g +M w1 +M s1 =M g +ρ w (VV s1 )+ρ s V s1 (1.1),

[0073] Where M g is the mass of the water-soil separation device; M w1 is the mass of water in the soil-water separation cylinder at time t1; M s1 is the mass of the soil in the soil-water separation cylinder at time t1; V is the volume of the soil-water separation cylinder; V s1 is the volume of soil in the soil-water separation cylinder at time t1; ρ w is the density of water; ρ s is the density of soil;

[0074] When the test time is t2, the total mass measured by the first weighing device 28 is read as M A2 , its mathematical expression is:

[0075] M A2 =M g +M w2 +M s2 =M g +ρ w (VV s2 )+ρ s V s2 (1.2),

[0076] Where M w2 is the mass of water in the soil-water separation cylinder at time t2; M s2 V is the mass of soil in the soil-water separation cylinder at time t2; s2 is the volume of soil in the soil-water separation cylinder at time t2;

[0077] By subtracting formula (1.1) from formula (1.2), we can get:

[0078]

[0079] Where ΔV s is the volume of soil collected in the water-soil separation device during the period t1 to t2; m s It is the mass of soil collected in the water-soil separation device during the time period from t1 to t2.

[0080] Among them, the mass of seepage water m w The calculation method is as follows:

[0081] When the test time is t1, the total mass measured by the second weighing device 33 is read as M B1 When the test time is t2, the total mass measured by the second weighing device 33 is read as M B2 , the mass of seepage water in the time period t1 to t2 is m w for:

[0082] m w =M B2 -M B1 -ρ W ΔV S (1.5).

[0083] Because the soil occupies a certain volume in the soil-water separation cylinder 30, and the corresponding volume of water is discharged into the water collection tank 34, the mass measured by the second weighing device 33 includes not only the mass of the seepage water, but also the mass of the water corresponding to the volume of the soil. B2 With M B1 After obtaining the total amount of water in the time period t1 to t2 by the difference between the values ​​of W ΔV S ), the seepage water quality during the time period t1 to t2 can be obtained.

[0084] The present invention provides a test device and method for simulating internal erosion of seawall soil under a circulating hydraulic gradient. The circulating hydraulic gradient generating system can realize the circulating water head supply at different soil elevations, and can effectively simulate the periodic cyclic fluctuation of the water level of the seawall soil under the action of waves; the internal erosion triaxial test system can set different confining pressures and axial pressures to simulate the stress state of the soil sample, realize the simulation of the internal erosion process of the soil sample under different stress states, and can perform triaxial shear tests on the samples to test the mechanical properties of the soil before and after internal erosion; the automatic soil-water separation measurement system can realize the separation of soil particles and water by a filter screen, the soil particles are deposited at the lower part of the soil-water separation cylinder, and the water is collected in a water collecting box. The two are weighed in real time by an electronic balance, and the mass of soil particles lost by the test soil sample and the mass of seepage water can be converted by a mathematical formula, thereby realizing real-time monitoring of the erosion and damage process.

[0085] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient, characterized in that: It includes a circulating hydraulic gradient generation system, an internal erosion triaxial test system, and an automatic soil-water separation measurement system; The circulating hydraulic gradient generating system comprises a fixed bracket, a screw bracket, a screw module, a stepping motor, a stepping driver, a controller, a lifting drive device, a water storage cylinder and a water outlet pipe. The two ends of the screw module are each connected to a screw bracket, and two screw brackets are vertically slidably arranged on the fixed bracket. The screw bracket is connected to the lifting drive device and driven to move up and down by the lifting drive device. The water storage cylinder is fixed on the slider of the screw module, one end of the water outlet pipe is connected to the water storage cylinder, and the other end is connected to the top water inlet of the internal erosion triaxial test system. The screw module is connected to the stepping motor and driven by the stepping motor to realize the up and down movement of the slider. The stepping motor is connected to the stepping driver, and the stepping driver is connected to the controller. The controller controls the operation of the stepping motor through the stepping driver to drive the slider and the water storage cylinder to move up and down periodically along the screw of the screw module, so as to provide a circulating water head that can change with time. The automatic soil-water separation measurement system includes a soil-water separation device and a first weighing device. The soil-water separation device includes a soil-water separation cylinder and a filter. The soil-water separation cylinder is placed on the first weighing device. The lower side feed port of the soil-water separation cylinder is connected to the bottom discharge port of the internal erosion triaxial test system through a discharge pipeline. A separation cylinder outlet pipe is provided on the upper side of the soil-water separation cylinder. The filter is arranged in the soil-water separation cylinder and is located between the feed port and the separation cylinder outlet pipe.

2. The test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to claim 1, characterized in that: The automatic soil-water separation measurement system also includes a water collecting device and a second weighing device. The water collecting device includes a water collecting box. The water collecting box is placed on the second weighing device. The outlet of the separation cylinder water outlet pipe leads to the water collecting box.

3. The test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to claim 1, characterized in that: The lifting drive device includes a winch, a wire rope and a pulley. The winch is fixed to the bottom of the fixed bracket, and the pulley is installed on the top of the fixed bracket. One end of the wire rope is wound around and connected to the winch, and the other end passes around the pulley and is connected to the screw bracket at the upper end.

4. The test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to claim 1, characterized in that: The circulating hydraulic gradient generating system also includes a water tank, a water pump and a power supply. The water pump is arranged in the water tank and connected to the water storage cylinder through a water inlet pipe. The power supply provides electrical energy to the stepper motor, the stepper driver, the controller and the water pump.

5. The test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to claim 1, characterized in that: The filter screen is detachably connected to the soil-water separation cylinder by bolts.

6. The test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to claim 1, characterized in that: The internal erosion triaxial test system includes a pressure sensor, a displacement sensor, an axial pressure loading rod, a sample cap, a pressure chamber, a pressure chamber base and an instrument frame. The pressure chamber is used to hold the sample. The sample cap is placed in the pressure chamber and located on the top of the sample. The upper water inlet of the sample cap is connected to the water outlet pipe. The pressure chamber base is arranged at the bottom of the pressure chamber. A funnel-shaped discharge port is provided on the pressure chamber base. The axial pressure loading rod is arranged at the upper end of the pressure chamber. The lower end of the axial pressure loading rod is used to abut against the upper end of the sample cap. The upper part of the axial pressure loading rod is connected to the pressure sensor and the displacement sensor. The pressure sensor and the displacement sensor are connected to the upper end of the instrument frame.

7. The test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to claim 6, characterized in that: A porous water-permeable plate is provided on the top and bottom of the sample in the pressure chamber, respectively, and filter paper is provided between the porous water-permeable plate on the top and the sample cap.

8. The test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to claim 2, characterized in that: The first weighing device and the second weighing device are electronic balances; four groups of supporting angle brackets are connected around the bottom of the fixed bracket.

9. A test method for simulating internal erosion of seawall soil under cyclic hydraulic gradient, characterized in that: The test device for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to any one of claims 1 to 8 comprises the following steps: placing a simulated seawall soil sample in a pressure chamber of the internal erosion triaxial test system; The circulating hydraulic gradient generating system provides a circulating water head that changes with time at different elevations; Water flows into the pressure chamber from the top of the sample, and the water flowing through the sample and the fine particles eroded are discharged through the outlet at the bottom of the sample to simulate the erosion process; The seepage water carrying fine particles enters the soil-water separation device for soil-water separation and is weighed in real time by the first weighing device; Calculate the mass and volume of the fine particles by formulas according to the readings of the first weighing device; After the soil and water separation is completed, close the erosion outlet valve, perform axial pressure loading according to stress or strain mode, and conduct triaxial test on the sample while keeping the confining pressure of the sample unchanged.

10. The test method for simulating internal erosion of seawall soil under cyclic hydraulic gradient according to claim 9, characterized in that: The mass and volume of fine particles are calculated as follows: When the test time is t1, the total mass measured by the first weighing device is read as M A1 , its mathematical expression is: M A1 =M g +M w1 +M s1 =M g +ρ w (V-V s1 )+ρ s V s1 (1.1), Where M g is the mass of the water-soil separation device; M w1 is the mass of water in the soil-water separation cylinder at time t1; M s1 is the mass of the soil in the soil-water separation cylinder at time t1; V is the volume of the soil-water separation cylinder; V s1 is the volume of soil in the soil-water separation cylinder at time t1; ρ w is the density of water; ρ s is the density of soil; When the test time is t2, the total mass measured by the first weighing device is read as M A2 , its mathematical expression is: M A2 =M g +M w2 +M s2 =M g +ρ w (V-V s2 )+ρ s V s2 (1.2), Where M w2 is the mass of water in the soil-water separation cylinder at time t2; M s2 V is the mass of soil in the soil-water separation cylinder at time t2; s2 is the volume of soil in the soil-water separation cylinder at time t2; By subtracting formula (1.1) from formula (1.2), we can get: Where, ΔV s is the volume of soil collected in the water-soil separation device during the period t1 to t2; m s It is the mass of soil collected in the water-soil separation device during the time period from t1 to t2.

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