Device and method for simulating deformation and failure mechanism of deep excavation expansive soil slope

Abstract

The present invention relates to a device and method for simulating deformation and failure mechanism of deep excavation expansive soil slope. The device comprises a model box, a slope model, a dry-wet cycle simulation mechanism and a detection mechanism. The top and one opposite surface of the model box are open and a water permeable module is arranged inside. The slope model comprises a slope soil body arranged on the water permeable module and a retaining wall provided with a first water permeable area. The slope soil body has a slope surface, and the retaining wall is arranged at the lowest point of the slope surface. The dry-wet cycle simulation mechanism comprises a reservoir, a bracket, a light source and a rainfall nozzle. The reservoir is provided with a second water permeable area connected to the water permeable module, and the bracket is provided with a light source and a rainfall nozzle connected to the reservoir. The detection mechanism comprises a sensor and a camera, and the sensor and the camera are used to collect deformation data of the slope soil body. The present invention simultaneously considers the influence of atmospheric dry-wet cycle and groundwater level change on the slope soil body, and more realistically reveals the deformation and failure mechanism of the deep excavation expansive soil slope from excavation to operation.

Description

Technical Field

[0001] The invention relates to the technical field of channel slope engineering, in particular to a device and method for simulating the deformation and failure mechanism of a deep excavation expansive soil slope. Background Art

[0002] Excavation provides air-side conditions for the landslide of the expansive soil slope. At the same time, under the unloading and strong atmospheric action near the surface, the expansion and contraction characteristics of the expansive soil are activated to produce expansion and contraction cracks, changing the original relatively stable humidity field, temperature field and groundwater storage state to form an expansion and contraction activity zone. Especially during the construction period and the initial operation, this effect is more significant. The deep excavation slope is more significantly affected by the unloading and atmosphere, and is more susceptible to deformation and landslide damage. In order to reduce the impact of atmospheric factors on the slope during operation, surface replacement treatment measures have been implemented. However, this treatment method still cannot completely block the water vapor exchange between the expansive soil and the atmosphere, so the expansive soil will still be affected by precipitation and temperature changes. At the same time, the excavation operation revealed the original cracks that were formed by geological movement and were originally buried deep underground. In particular, the revealed gentle angle cracks have an adverse effect on the long-term stability of the slope and are a potential hidden danger threatening the safe water supply and efficient operation of the channel. Since it was put into operation, some deep excavation expansive soil slopes in the head section have shown obvious creep deformation, and the cumulative deformation value has exceeded the design warning value. Among them, the internal deformation is particularly affected by the gently inclined primary cracks, and the depth of the deformed body is between 2 and 8 meters.

[0003] It can be seen that the actual project operation shows that the long-term stability of deep excavated expansive soil channel slopes is affected by the combined effects of expansion and contraction cracks, primary cracks, groundwater level changes, and atmospheric dry-wet cycles. In the past, rich results have been obtained in the simulation of deformation and failure of expansive soil slopes. However, due to the characteristics of expansive soil such as expansion and contraction, cracks, and overconsolidation, as well as the internal and external factors such as long and slow-angle primary cracks and groundwater level fluctuations faced by deep excavated expansive soil slopes, the simulation of deformation and failure of such slopes still has the following shortcomings: (1) The changes in the slope humidity field and groundwater storage state during the excavation process are not considered. During the excavation of expansive soil slopes, the combined effects of rainfall and groundwater can easily lead to landslides of excavated expansive soil during construction; (2) The influence of the internal dry-wet cycle of expansive soil caused by groundwater level fluctuations is not considered. In the lower part of the atmospheric influence zone, a small number of expansion and contraction cracks are interconnected, receiving rainwater infiltration to form upper stagnant water. The water level and water volume vary greatly with the seasons. The upper stagnant water is mainly discharged by evaporation, and it may dry up when there is no rain for a long time. Expansive soils expand when they absorb water and shrink when they dehydrate. The fluctuation of groundwater level causes the change of moisture field of slopes. Meanwhile, the parts below groundwater level for a long time will keep the moisture content relatively stable. However, the existing tests mainly consider the influence of atmospheric dry-wet cycle on the moisture content of the surface soil of slopes, and do not consider the temporal and spatial changes of the moisture content of the middle and upper parts of slopes caused by groundwater level fluctuation and its influence; (3) The influence of primary cracks on slope stability is not considered or not fully considered. The long and small cracks with gentle inclination in deep excavated expansive soil slopes are generally mirror-smooth. These cracks constitute the potential sliding bed of landslides and are also the most dangerous sliding interface, which plays a restrictive role in the shape and scale of landslides. On-site investigation shows that long and small cracks develop in areas with abundant groundwater. The crack structure surface is widely distributed and has a large area. The rise of groundwater increases the hydrostatic pressure and reduces the shear strength of soil, which is the controlling factor of channel slope stability.

[0004] Therefore, it is urgent to propose a device for simulating the deformation and failure mechanism of deep excavation expansive soil slopes to overcome the above technical defects. Summary of the invention

[0005] To this end, the technical problem to be solved by the present invention is to overcome the technical defects existing in the prior art, and propose a device and method for simulating the deformation and failure mechanism of a deep excavated expansive soil slope, which simultaneously considers the influence of atmospheric dry-wet cycles and groundwater level changes on the slope soil, and more realistically reveals the deformation and failure mechanism of the deep excavated expansive soil slope from excavation to operation.

[0006] In order to solve the above technical problems, the present invention provides a device for simulating the deformation and failure mechanism of deep excavation expansive soil slope, comprising:

[0007] A model box body, the top of which is open, an opposite side of the model box body is set to be open, and a water-permeable module is arranged in the model box body;

[0008] A slope model, comprising a slope soil body and a retaining wall, wherein the slope soil body is arranged on the permeable module, the slope soil body has a slope surface, a retaining wall is arranged at the lowest point of the slope surface, and a first permeable area is arranged on the retaining wall;

[0009] A dry-wet cycle simulation mechanism, comprising a water reservoir, a bracket, a light source and a rainfall nozzle, wherein a second water permeable area is provided on one side of the water reservoir, the second water permeable area is connected to the water permeable module, and a light source and a rainfall nozzle are provided on the bracket, wherein the rainfall nozzle is connected to the water reservoir;

[0010] The detection mechanism comprises a sensor and a camera, wherein the sensor and the camera are used to collect deformation data of the slope soil body and obtain the deformation change law of the slope soil body.

[0011] In one embodiment of the present invention, the bracket includes a vertical pole, a supporting truss, a sliding rod and a cross beam, the supporting truss is arranged on the vertical pole, a plurality of sliding rods are arranged on the supporting truss, a cross beam is slidably arranged on the sliding rod, and the light source and the rainfall nozzle are arranged on different cross beams.

[0012] In one embodiment of the present invention, the wet-dry cycle simulation mechanism further includes a water supply pipe, and the rainfall sprinkler head is connected to the water reservoir via the water supply pipe.

[0013] In one embodiment of the present invention, the wet-dry cycle simulation mechanism further includes a water inlet pipe and a water valve. The water inlet pipe is used to supply water to the water reservoir, and the water inlet pipe is provided with a water valve.

[0014] In one embodiment of the present invention, the slope model further includes an inverted filter layer, and the permeable module is separated from the slope of the slope soil body by the inverted filter layer.

[0015] In one embodiment of the present invention, the sensors include a matrix suction meter, a moisture content meter, a piezometer and a flexible inclinometer, which are buried in the slope soil and are used to collect the matrix suction of the slope soil, the change in moisture content, the change in groundwater level inside the slope and the change in deformation inside the slope.

[0016] In one embodiment of the present invention, native cracks are prefabricated in the slope soil.

[0017] In one embodiment of the present invention, the permeable module is a permeable brick.

[0018] In one embodiment of the present invention, the light source is an ultraviolet lamp.

[0019] Based on the same inventive concept, the present invention also provides a simulation method for the deformation and failure mechanism simulation device of deep excavation expansive soil slope as described above, the method comprising:

[0020] According to the permeability coefficient, a stable seepage field is formed on the slope soil, and the water level of the reservoir is controlled by the water valve;

[0021] Through the light-rainfall model, multiple rounds of dry-wet cycles are carried out to simulate the impact of dry-wet cycles on slope soil. During each round of dry-wet cycles, the water level of the reservoir is adjusted to control the fluctuation of the groundwater level to simulate the impact of the groundwater level on the slope soil.

[0022] The matrix suction meter, moisture content meter, piezometer and flexible inclinometer were used to collect the data of matrix suction of slope soil, moisture content change, groundwater level change inside the slope and deformation change inside the slope, and the change laws of matrix suction of slope soil, moisture content change, groundwater level change inside the slope and deformation change inside the slope were obtained.

[0023] The above technical solution of the present invention has the following advantages compared with the prior art:

[0024] The present invention provides a device and method for simulating the deformation and failure mechanism of a deep excavated expansive soil slope, which simultaneously considers the influence of atmospheric dry-wet cycles and groundwater level changes on the slope soil, and more realistically reveals the deformation and failure mechanism of the deep excavated expansive soil slope from excavation to operation. The device and method are particularly suitable for the design of new projects for deep excavated expansive soil slopes in the fields of water conservancy and transportation and for reference in the reinforcement and disposal of existing projects. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to make the contents of the present invention more clearly understood, the present invention is further described in detail below based on specific embodiments of the present invention in conjunction with the accompanying drawings.

[0026] Figure 1 A schematic structural diagram of a device for simulating deformation and failure mechanism of deep excavated expansive soil slope provided in an embodiment of the present invention.

[0027] Figure 2 It is a schematic diagram of the filling, excavation and support process of the deep expansive soil slope of the present invention.

[0028] Figure 3 It is a schematic diagram of the combination of primary cracks in the deep excavated expansive soil slope of the present invention.

[0029] Figure 4 It is a process line diagram of atmospheric dry-wet cycle and groundwater level fluctuation of the present invention.

[0030] Figure 5 The present invention obtains a visual graph of the internal deformation data of the soil body that changes with time.

[0031] Figure 6 This is the slope soil surface partition map obtained by the present invention.

[0032] Figure 7 This is a schematic diagram of sliding failure under the combined action of upper layer primary cracks and expansion and contraction cracks obtained by the present invention.

[0033] Among them, the accompanying drawings are described as follows: 1. Model box; 21. Slope soil; 211. Slope surface; 22. Retaining wall; 221. First permeable area; 31. Reservoir; 311. Second permeable area; 321. Vertical pole; 322. Support truss; 323. Sliding rod; 324. Crossbeam; 33. Light source; 34. Rainfall sprinkler; 35. Water supply pipe; 36. Water inlet pipe; 41. Sensor; 42. Camera; 43. Flexible inclinometer; 5. Permeable module; 6. Baffle; 7. Excavated soil layer; 8. Prefabricated fractured salt layer. DETAILED DESCRIPTION

[0034] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments so that those skilled in the art can better understand the present invention and implement it, but the embodiments are not intended to limit the present invention.

[0035] Reference Figure 1 As shown, an embodiment of the present invention provides a device for simulating deformation and failure mechanism of deep excavation expansive soil slope, comprising a model box 1, a slope model, a dry-wet cycle simulation mechanism and a detection mechanism, wherein the top of the model box 1 is open, an opposite surface of the model box 1 is set to be open, and a permeable module 5 is arranged in the model box 1; the slope model comprises a slope soil body 21 and a retaining wall 22, the slope soil body 21 is arranged on the permeable module 5, the slope soil body 21 has a slope surface 211, and a retaining wall 22 is arranged at the lowest point of the slope surface 211, and the retaining wall 22 A first water permeable area 221 is arranged on it; the dry-wet cycle simulation mechanism includes a water reservoir 31, a bracket, a light source 33 and a rainfall nozzle 34, a second water permeable area 311 is arranged on one side of the water reservoir 31, the second water permeable area 311 is connected to the water permeable module 5, and a light source 33 and a rainfall nozzle 34 are arranged on the bracket, wherein the rainfall nozzle 34 is connected to the water reservoir 31; the detection mechanism includes a sensor 41 and a camera 42, the sensor 41 and the camera 42 are used to collect deformation data of the slope soil body 21, and obtain the deformation change law of the slope soil body 21.

[0036] The present invention provides a device for simulating the deformation and failure mechanism of a deep excavated expansive soil slope, which simultaneously considers the influence of atmospheric dry-wet cycles and groundwater level changes on the slope soil, and more realistically reveals the deformation and failure mechanism of the deep excavated expansive soil slope throughout the entire process from excavation to operation. The device is particularly suitable for the design of new projects for deep excavated expansive soil slopes in the fields of water conservancy and transportation and for reference in the reinforcement and disposal of existing projects.

[0037] In one embodiment, the above-mentioned dry-wet cycle simulation mechanism also includes a water supply pipe 35, a water inlet pipe 36 and a water valve. The rainfall nozzle 34 is connected to the water reservoir 31 through the water supply pipe 35, and can stably convert the water in the water reservoir 31 into simulated rainfall to provide a humid environment for the slope model. The water inlet pipe 36 is used to supply water to the water reservoir 31. A water valve is provided on the water inlet pipe 36. This setting enables the operator to easily adjust the water level of the water reservoir 31. During the simulation process, if it is necessary to increase the simulation time, the water flow of the water inlet pipe 36 can be increased through the water valve to quickly increase the water level of the water reservoir 31 to ensure that there is sufficient water to supply the simulated rainfall; if the frequency of humidity changes needs to be adjusted during the simulation process, the water level of the water reservoir 31 can also be accurately controlled by adjusting the water valve, so that the dry-wet cycle simulation is more in line with the humidity fluctuation law of the actual environment. Through the coordinated work of components, the stability and reliability of the dry-wet cycle simulation mechanism during operation are ensured. The stable water level regulation ensures the continuity and stability of the simulated rainfall, so that the dry-wet cycle simulation process will not be interrupted due to insufficient water or unstable water supply. This provides solid and reliable simulation conditions for in-depth research on the deformation and failure mechanism of deep excavated expansive soil slopes in a dry-wet cycle environment.

[0038] Complex environment simulation includes atmospheric dry-wet cycle simulation and groundwater level fluctuation simulation. Specifically, in order to simulate the influence of groundwater level on the slope, a water-permeable module 5 is set at the bottom of the model box 1. The water-permeable module 5 is separated from the slope of the slope soil body 21 by a filter layer. The filter layer is composed of sand and geotextile. The water-permeable module 5 can use permeable bricks. The water level of the reservoir 31 is controlled by a water valve, and the light source 33 and the rainfall nozzle 34 are used to simulate the influence of sunshine and rainfall respectively, so as to achieve the purpose of simulating atmospheric dry-wet cycle. Each round of atmospheric dry-wet cycle is based on the moisture content measured by the moisture meter. When the moisture content drops to the initial moisture content, it is regarded as the end of the dehumidification process. Combined with the actual project, more than 3 rounds of atmospheric dry-wet alternating cycles are simulated in the whole experiment. During each round of atmospheric dry-wet cycle, the fluctuation of the groundwater level is synchronously adjusted and controlled by the water level of the reservoir 31, that is, the highest groundwater level is reached after rainfall, and it gradually decreases to the lowest groundwater level during long-term drought, so as to achieve the groundwater level fluctuation with the atmospheric dry-wet cycle.

[0039] In one embodiment, the bracket includes a vertical pole 321, a support truss 322, a slide bar 323 and a crossbeam 324. The support truss 322 is arranged on the vertical pole 321, and a plurality of slide bars 323 are arranged on the support truss 322. The slide bar 323 is slidably provided with a crossbeam 324. The light source 33 and the rain nozzle 34 are arranged on different crossbeams 324. Preferably, the light source 33 can be an ultraviolet lamp, and the rain nozzle 34 simulates the rainfall stage, and the ultraviolet lamp simulates the dehumidification stage, so as to realize the simulation test process of alternating dry and wet cycles. In actual use, the rainfall and sunshine height are controlled by the up and down sliding of the crossbeam 324 on the slide bar 323, which can not only ensure that the rain nozzle 34 and the ultraviolet lamp do not interfere with each other during use, but also control the uniformity of rainfall and ensure the uniform illumination of the bathroom heater lamp by height.

[0040] In one embodiment, native cracks are prefabricated in the slope soil 21. Specifically, Figure 2 As shown in the figure, the filling and excavation simulation of the slope model with primary fissures includes the filling and consolidation of expansive soil with prefabricated primary fissures, water storage to form a stable groundwater level, layer-by-layer graded excavation of the slope after consolidation, and retaining wall support at the foot of the slope. (1) Before compaction, the required fill mass is calculated based on the natural density of the expansive soil, the predetermined compaction degree, and the size of each layer of fill. The soil sample is dried and crushed. After repeated drying, the soil sample is adjusted to the optimal moisture content. During the water distribution process, the soil sample is repeatedly broken up with a spike rake and suffocated with canvas for 24 hours to ensure that the moisture content of the soil sample is uniform. (2) In order to simulate the formation process of the deep excavation slope and the influence of multiple factors such as excavation and unloading, the reshaped soil sample is used. According to the length and height of the slope model, it is filled to the top in the model box 1 in layers. The filling is carried out by layered compaction method, and the compaction degree is strictly controlled. During the filling process, a ramming hammer is used to carry out sufficient side treatment to ensure that the soil and the tempered glass are closely attached to each other. The boundary soil is compacted with a rubber hammer. After each layer of soil is filled, a ring knife is used to take samples to detect the compaction and moisture content of the layer of soil to ensure that each step meets the requirements of the experimental design. (3) After the filling is completed, it is left to stand for a period of time to form a stable humidity field and stress field. Thereafter, the water level of the reservoir 31 is stored to the set groundwater level according to the set groundwater level, and the water level is controlled by a water valve to maintain it unchanged. (4) Before the slope cutting process, the slope boundary is drawn on the outside of the tempered glass of the model box 1, and the excavation is carried out according to the set excavation line to form an excavation slope. (5) A concrete retaining wall 22 is used to simulate the effect of the anti-sliding piles at the foot of the excavation slope. The first permeable area 221 is set at the lower part of the retaining wall 22 to simulate the normal seepage phenomenon of the channel. At the same time, a geotextile is laid on the surface of the first permeable area 221 to achieve the anti-filtration function.

[0041] In this embodiment, the cracks with a gentle inclination angle are smooth and have low shear strength. Coarse salt can be used for simulation. When groundwater flows through, the coarse salt dissolves to form cracks. Figure 3 As shown in the figure, by prefabricating cracks at different heights, the effects of cracks at different positions can be simulated respectively. In particular, for the topmost crack, the position of the original slow-angle crack in this layer is set according to the depth of 30 cm of the atmospheric influence zone in the existing model, thereby forming a combination of expansion and contraction cracks and long and slow-angle cracks, thereby simulating the combined sliding failure.

[0042] In one embodiment, the sensor 41 includes a matrix suction meter, a moisture meter, a piezometer and a flexible inclinometer 43, which are buried in the slope soil 21 and are used to collect the matrix suction, moisture content change, groundwater level change inside the slope and deformation change inside the slope of the slope soil 21. Preferably, the moisture meter and the piezometer can be arranged in a pre-buried manner, and the matrix suction meter and the flexible inclinometer 43 can be arranged in a drilled buried manner; for the soil matrix suction, moisture content, internal displacement and other data, cluster analysis can be used for partition analysis, and for surface crack changes, digital image processing technology can be used for tracking and identification.

[0043] Furthermore, the number of cameras 42 can be multiple, and multiple cameras 42 can be arranged on the front and side, and the front and side cameras 42 can respectively collect the changes in the surface cracks of the slope soil 21, the overall expansion and contraction deformation of the slope, and the expansion and contraction deformation of the side and the closure of the original cracks, etc. Figure 6 As shown, continuous slope surface photos can be processed by digital image technology to track and classify slope surface deformations at different locations.

[0044] The present invention comprehensively considers the changes in moisture content of the surface soil affected by the atmospheric dry-wet cycle, and the changes in moisture content of the internal soil in the middle and upper part of the slope affected by groundwater level fluctuations. In this way, it can simulate the situation where long-term drought causes the groundwater level to drop, and rainwater recharge in rainy seasons causes the groundwater level to rise.

[0045] Corresponding to the above-mentioned deep excavation expansive soil slope deformation and failure mechanism simulation device, the embodiment of the present invention also provides a deep excavation expansive soil slope deformation and failure mechanism simulation method, the method comprising the following steps:

[0046] Step 1: forming a stable seepage field for the slope soil 21 according to the permeability coefficient, and controlling the water level of the reservoir 31 through a water valve;

[0047] Step 2: Carry out multiple rounds of dry-wet cycles through the light-rainfall mode to simulate the influence of dry-wet cycles on the slope soil 21. During each round of dry-wet cycles, the fluctuation of the groundwater level is controlled by adjusting the water level of the reservoir 31 to simulate the influence of the groundwater level on the slope soil 21.

[0048] Step 3: Use a matrix suction meter, a moisture meter, a piezometer and a flexible inclinometer 43 to respectively collect the matrix suction, moisture content change, groundwater level change inside the slope and deformation change data of the slope soil 21, and obtain the matrix suction, moisture content change, groundwater level change inside the slope and deformation change law of the slope soil 21.

[0049] The following is a detailed description of a method for simulating the deformation and failure mechanism of a deep excavated expansive soil slope provided by the present invention through a specific case.

[0050] (1) Overall design: The actual engineering slope is 15m high from the top of the slope to the wading section, and the slope ratio is set to 1:2.5. The slope model is scaled down according to the ratio of prototype: model = 10:1. The initial moisture content of the expansive soil is 20%. The slope is 325cm long, 150cm high, and 100cm wide, of which the width of the top of the slope is 30cm. In the experiment, environmental parameters are set according to the local climatic conditions of the project. By burying instruments such as moisture meter, matrix suction meter, osmometer, and flexible inclinometer 43 in the model, key parameters such as the internal moisture content, matrix suction, groundwater level, and deformation of the slope are monitored in real time, realizing the simulation of the deformation and failure mechanism of the deep excavation expansive soil slope under complex environmental conditions.

[0051] The main components of the model soil are quartz and clay, of which quartz accounts for 41.3% and clay minerals account for 44.9%. The main component of clay minerals is illite-montmorillonite mixed layer minerals, accounting for 48.9%. The clay content of the soil is relatively high, and the expansion effect is obvious. According to the geotechnical test procedures, its basic physical indicators were measured, among which the optimal moisture content was 22% and the maximum dry density was 1.77g·cm -3 , the free expansion rate is 54.5%.

[0052] In order to reduce the influence of the boundary of the model box 1 on the test results, vaseline was evenly applied within the filling range of the model box 1. A concrete retaining wall 22 was used to simulate the effect of anti-slide piles. A first permeable area 221 was set at the lower part of the retaining wall 22 to simulate the normal seepage phenomenon of the channel, and a geotextile was laid on the surface of the first permeable area 221 to achieve the anti-filtration function.

[0053] (2) Slope model filling and excavation simulation with primary cracks: During the sample preparation process, the compaction degree of the slope model was controlled to be above 95%. The slope model with an initial slope ratio of 1:2.5 was set to have a slope height of 150 cm, a length of 325 cm, a slope top width of 30 cm, and a slope foot bottom of 50 cm. The slope foot height after excavation was 30 cm. The soil was filled with a length of 325 cm and a height of 150 cm. The filling was carried out by layered compaction, and baffles 6 were added to the tempered glass to meet the filling requirements. Before compaction, the required fill mass was accurately calculated based on the natural density of the expansive soil, the predetermined compaction degree, and the size of each layer of fill. Subsequently, the soil sample was dried and crushed to pass through a sieve with a diameter of 5 mm. After repeated turning and drying, the soil sample was adjusted to an optimal moisture content of 20%. During the water distribution process, the soil samples were repeatedly broken up with a spike rake and covered with canvas for 24 hours to ensure uniform moisture content of the soil samples.

[0054] In the slope soil 21 obtained after the final excavation, primary cracks are prefabricated at pre-set positions. After analysis, the primary cracks are prefabricated with coarse salt to form a fissure salt layer 8. Existing studies have shown that the short-term doping and compression of coarse salt particles have little effect on the physical properties of the expansive soil itself. The prefabricated fissure salt layer 8 can form one or several erosion layers inside the slope soil 21 by means of water storage and dissolution as needed, which is used to simulate the sliding surface produced by the complex primary cracks of the excavated slope. In view of the possible salinization of the soil, most of the coarse salt can be dissolved and flowed out by continuous storage and drainage, so as to minimize the impact of the coarse salt particles themselves on the expansive soil slope and eliminate experimental interference factors. For some coarse salts that are closely combined with the soil, even if they are not fully dissolved, they will be affected by capillary evaporation during the dehumidification process, resulting in the migration of these coarse salt particles similar to the drought process of some saline-alkali lands, and finally enriched on the slope surface. This can reflect the crack channels of infiltration and evaporation inside the soil to a certain extent. On this basis, the enrichment amount can roughly indicate the location and size of the concentrated leakage points on the slope surface, providing a reference basis for the key monitoring and analysis areas of subsequent experiments, such as Figure 7 As shown in the figure, the stronger evaporation effect at the top of the slope makes the cracks on the slope surface obvious, which clearly indicates the sliding area during the dry-wet cycle.

[0055] During the subsequent filling process, a rammer is used to compact the soil mass, and a rammer hammer is used to perform sufficient side treatment to ensure the tight fit at the boundary between the soil mass, toughened glass, and the baffle 6. The boundary soil is carefully tamped with a rubber hammer. After each layer of soil is filled, a core cutter is used to take samples to detect the compaction degree and moisture content of the soil layer, ensuring that each step meets the precise requirements of the test design. According to the pre-determined instrument layout positions, piezometers and moisture content meters are buried. After the excavation is completed, the matric suction meter and the flexible inclinometer 43 are buried.

[0056] After the slope filling is completed, it is left to stand for 48 - 72 hours to complete compression consolidation in order to achieve the soil water balance of the soil mass. After standing, calculate the time required to form a stable seepage flow based on the permeability coefficient to reach a stable groundwater level. For example, when the permeability coefficient is 10 -6 m / s, the initial groundwater level is set at 0.6 m. When storing water to the initial groundwater level, it takes another 24 - 48 hours to form a stable seepage field.

[0057] Before the excavation work, the slope excavation boundary line and the layered excavation height are marked on the outside of the toughened glass of the model box 1. The excavation is carried out in layers according to the excavation boundary line. At the front edge of the slope toe, a counter-pressure toe is set, and the excavation is in a stepped shape. Temporary diversion ditches are arranged in the area of intensive water seepage points for diversion, and the gushing water is collected into the drainage ditch 701. When the excavation reaches the slope toe, the height of the retaining wall 22 is 35 cm. Among them, water-permeable holes are set below 30 cm in height so that groundwater can pass through the retaining wall 22. After the slope excavation is completed, the construction baffle 6 is removed.

[0058] (3)Complex environment simulation: Consider the cycle of "light dehumidification - rainfall humidification" as a complete atmospheric dry-wet alternation cycle, and regard the cycle of "groundwater level decline - groundwater level rise" as a complete groundwater level fluctuation process, and the duration of the atmospheric dry-wet alternation cycle is the same as that of the groundwater level fluctuation process. Given that precipitation will recharge the groundwater level in actual projects and the groundwater level will decline in the dry season, the change of the groundwater level is thus affected by the atmospheric dry-wet conditions.

[0059] Rainfall nozzles 34 and light sources 33 are set at a height of 50 cm from the top of the slope soil mass 21. Through the "light - rainfall" cycle, the atmospheric dry-wet cycle is simulated. Specifically, the sliding of the cross beam 324 on the sliding rod 323 is used to control the height of rainfall and sunlight to ensure the operation stability of the device and that they do not interfere with each other. During the dry-wet alternation test process, corresponding climate simulation is carried out with reference to the local climate data. During the simulated rainfall stage, the maximum rainfall intensity that the rainfall nozzle 34 can simulate is 6.49 mm / h, that is, 155.76 mm / d, which can simulate the rainfall intensity of rainstorm - heavy rainstorm. According to different working conditions, the corresponding rainfall intensity is selected. During the simulated dehumidification stage, the light intensity is designed to be a constant 470 W / m 2This test refers to the local climate conditions of A, specifically, Figure 4 As shown in the figure, a stable rainfall of 80 mm and a groundwater level of 100 cm were maintained during the simulated rainfall stage. In the dehumidification stage after the rainfall stage, the water reservoir recharge of the groundwater level was removed and gradually reduced to 30 cm, in order to achieve a dual cycle of atmospheric dryness and wetness and groundwater. According to existing engineering practice experience, after three rounds of dry-wet cycles, the slope suffered serious deformation and damage, so the test carried out four rounds of dry-wet cycles.

[0060] In order to simulate the influence of groundwater level on the slope, a permeable module 5 is provided in the model box 1, and the permeable module 5 is separated from the expansive soil slope soil body 21 by a filter layer composed of sand and geotextile. The permeable module 5 is connected to the reservoir 31, and the water level of the reservoir 31 is controlled by a water valve, so as to achieve the purpose of controlling the groundwater level. During each round of atmospheric dry-wet cycle, the fluctuation of the groundwater level is controlled by adjusting the water level of the reservoir 31. The highest groundwater level is reached after rainfall, and gradually decreases to the lowest groundwater level during long-term drought. The initial groundwater level is set to 0.6m, which is the lowest groundwater level. After rainfall, it gradually rises to 0.9m, which is the highest groundwater level.

[0061] (4) Internal and external multi-source and multi-type monitoring data collection and analysis: The experiment arranged corresponding sensors 41 for groundwater and surface dry-wet cycles to monitor the moisture content of the surface soil of the slope soil 21, matrix suction, and the change law of groundwater level and deformation inside the slope. Specifically, for the observation of groundwater level, micro-osmometers were symmetrically arranged at 75 cm and 30 cm from the foot of the slope, 175 cm and 55 cm from the foot of the slope, and 25 cm from the side of the model box 1. For the observation of moisture content, micro-moisture meters were symmetrically arranged at 175 cm and 275 cm from the foot of the slope, 10 cm, 30 cm, and 45 cm from the excavated slope, and 25 cm from the side of the model box 1. For the observation of matrix suction, they were arranged near the positions of the two upper layers of moisture meters. A flexible inclinometer 43 is used to observe the internal deformation of the slope. The flexible inclinometers 43 are symmetrically arranged at 50 cm, 125 cm, and 250 cm from the slope foot to observe the internal deformation of different parts. The flexible inclinometer 43 is fixed at the bottom by making an umbrella-shaped anchor, and bentonite is injected at the bottom to prevent contact penetration damage. The flexible inclinometer 43 is slowly lowered to the required measurement position through a catheter (a protective pipe pre-installed at the monitoring point). After the burial is completed, the soil is filled in the catheter, and then the catheter is pulled out to ensure that the disturbance to the flexible inclinometer 43 is small during the soil and water balance process of the soil slope. The internal deformation measurement results of the flexible inclinometer 43 are as follows: Figure 5 As shown, the displacement values ​​of the flexible inclinometer 43 at different depth measuring points changing with time in different dry-wet cycle periods can be obtained.

[0062] In order to facilitate the observation of the development of the side cracks of the slope soil body 21, both sides of the model box 1 are sealed with tempered glass.

[0063] The present invention provides a method for simulating the deformation and failure mechanism of a deep excavated expansive soil slope, which simultaneously considers the influence of atmospheric dry-wet cycles and groundwater level changes on the slope soil, and more realistically reveals the deformation and failure mechanism of the deep excavated expansive soil slope throughout the entire process from excavation to operation. The method is particularly suitable for the design of new projects for deep excavated expansive soil slopes in the fields of water conservancy and transportation and for reference in the reinforcement and disposal of existing projects.

[0064] Obviously, the above embodiments are merely examples for clear explanation and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the protection scope of the invention.

Claims

1. A device for simulating deformation and failure mechanism of deep excavation expansive soil slope, characterized by: include: A model box body, the top of which is open, an opposite side of the model box body is set to be open, and a water-permeable module is arranged in the model box body; A slope model, comprising a slope soil body and a retaining wall, wherein the slope soil body is arranged on the permeable module, the slope soil body has a slope surface, a retaining wall is arranged at the lowest point of the slope surface, and a first permeable area is arranged on the retaining wall; A dry-wet cycle simulation mechanism, comprising a water reservoir, a bracket, a light source and a rainfall nozzle, wherein a second water permeable area is provided on one side of the water reservoir, the second water permeable area is connected to the water permeable module, and a light source and a rainfall nozzle are provided on the bracket, wherein the rainfall nozzle is connected to the water reservoir; A detection mechanism, comprising a sensor and a camera, wherein the sensor and the camera are used to collect deformation data of the slope soil and obtain deformation change rules of the slope soil; The dry-wet cycle simulation mechanism also includes a water supply pipe, and the rainfall sprinkler is connected to the water reservoir through the water supply pipe; The dry-wet cycle simulation mechanism also includes a water inlet pipe and a water valve, wherein the water inlet pipe is used to supply water to the water reservoir, and a water valve is arranged on the water inlet pipe; The slope model further includes an inverted filter layer, and the permeable module is separated from the slope of the slope soil body by the inverted filter layer; The sensors include a matrix suction meter, a moisture content meter, a piezometer and a flexible inclinometer, which are buried in the slope soil and are used to collect matrix suction of the slope soil, moisture content changes, groundwater level changes inside the slope and deformation changes inside the slope.

2. The device for simulating deformation and failure mechanism of deep excavation expansive soil slope according to claim 1, characterized in that: The bracket includes a vertical pole, a supporting truss, a sliding rod and a cross beam. The supporting truss is arranged on the vertical pole. A plurality of sliding rods are arranged on the supporting truss. A cross beam is slidably arranged on the sliding rod. The light source and the rainfall nozzle are arranged on different cross beams.

3. The device for simulating deformation and failure mechanism of deep excavation expansive soil slope according to claim 1, characterized in that: The slope soil body is prefabricated with native cracks.

4. The device for simulating deformation and failure mechanism of deep excavation expansive soil slope according to claim 1, characterized in that: The permeable module is a permeable brick.

5. The device for simulating deformation and failure mechanism of deep excavation expansive soil slope according to claim 1, characterized in that: The light source is an ultraviolet lamp.

6. A simulation method for the deep excavation expansive soil slope deformation and failure mechanism simulation device according to any one of claims 1 to 5, characterized in that: Methods include: According to the permeability coefficient, a stable seepage field is formed on the slope soil, and the water level of the reservoir is controlled by the water valve; Through the light-rainfall model, multiple rounds of dry-wet cycles are carried out to simulate the impact of dry-wet cycles on slope soil. During each round of dry-wet cycles, the water level of the reservoir is adjusted to control the fluctuation of the groundwater level to simulate the impact of the groundwater level on the slope soil. The matrix suction meter, moisture content meter, piezometer and flexible inclinometer were used to collect the data of matrix suction of slope soil, moisture content change, groundwater level change inside the slope and deformation change inside the slope, and the change laws of matrix suction of slope soil, moisture content change, groundwater level change inside the slope and deformation change inside the slope were obtained.

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