A complex stress field tunnel model test loading device and test method

Abstract

The application belongs to the technical field of stress field equipment for tunnel physical simulation test, and specifically discloses a complex stress field tunnel model test loading device and a test method. The device comprises a loading assembly arranged on the surface of a supporting plate, the loading assembly is attached to the surface of a tunnel physical model to be loaded, and the non-uniform stress field of the surface of the tunnel physical model to be tested is realized by adjusting the loading assembly under the action of external load. The loading assembly comprises a loading frame, a compression column and a unit ram. The surface of the loading frame is provided with mounting holes, the compression column is arranged in the mounting holes, and the end of the compression column close to the tunnel physical model to be tested is connected with the unit ram. The compression column is composed of micro-unit bodies with different elastic modulus ratios. The three-dimensional stress field required by the physical model test is obtained according to the real stress field of the tunnel engineering prototype through the similarity theory, and the three-dimensional stress field of the physical model is divided into units and normalized to determine the different elastic modulus ratios. The device can realize non-uniform loading of the complex stress field.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of stress field equipment for tunnel physical simulation test, in particular to a complex stress field tunnel model test loading device and a testing method. BACKGROUND

[0002] For tunnel engineering, many deep tunnel engineering is often affected by deviatoric stress and non-uniform stress, resulting in asymmetric and non-coordinated deformation and damage of the tunnel, and complex geological physical model test is an important means to study tunnel engineering problems.

[0003] In the prior art, many underground tunnel physical model tests are carried out under uniform stress, for example, a device in the prior art applies axial pressure to both ends of a rock sample, applies confining pressure to the outer wall, and applies internal pressure to the inner wall, so that the entire sample is in an axisymmetric stress state to realize uniform stress. The device is only suitable for loading of rock samples, and it is difficult to quantitatively control the size of the non-uniform stress field. At the same time, for a small part of the device for testing non-uniform stress, for example, a honeycomb oil cylinder is used to realize dynamic and gradient stress loading by controlling the oil distribution in the servo hydraulic system. Due to the setting of the hydraulic system and the oil path, the device design structure is complex, the manufacturing cost is high, and the operation is also complex. Therefore, the existing complex stress field tunnel model test loading device is not mature, and it is urgent to design a test device that is simple in structure and operation and can more accurately simulate the complex stress field of the tunnel and realize non-uniform loading of the complex stress field. SUMMARY

[0004] The present application aims to solve the problem that the existing complex stress field tunnel model test loading device is not applicable to complex three-dimensional stress problems, many loading devices can only be used for qualitative loading analysis, and the device design structure is complex. Based on this, the present application provides a complex stress field tunnel model test loading device and a testing method.

[0005] To achieve the above-mentioned purpose, in a first aspect, the present application provides a complex stress field tunnel model test loading device, comprising:

[0006] A supporting plate, on the surface of which a tunnel physical model to be tested is placed;

[0007] A loading assembly, which is internally provided with a plurality of small units with different elastic moduli, and is used to apply different stress value loads to different sites on the surface corresponding to the tunnel physical model to be tested; wherein,

[0008] The loading assembly comprises a loading frame, compression columns and unit pressure heads, a plurality of mounting holes are formed through the surface of the loading frame, each mounting hole is provided with a compression column, the compression column is connected to the unit pressure head at one end close to the physical model of the tunnel to be tested, wherein each compression column is composed of micro-unit bodies with different elastic modulus ratios, the physical model three-dimensional stress field is obtained according to the tunnel engineering prototype and based on the similarity theory, and the unit division and normalization calculation of the physical model three-dimensional stress field are determined.

[0009] In some embodiments that can be implemented, the loading frame comprises:

[0010] An outer frame, the outer frame surrounds an internal region;

[0011] An upper frame and a lower frame, the upper frame and the lower frame are arranged in layers in the internal region, each mounting hole penetrates the upper frame and the lower frame in turn, the distance between adjacent mounting holes is equal, and a plurality of mounting holes are arranged in an array.

[0012] In some embodiments that can be implemented, the lower frame is provided with the unit pressure head at the bottom end surface, the lower frame is magnetically connected to the unit pressure head, one end of the unit pressure head extends into the mounting hole and is in contact with the surface of the compression column, and the compression column is slidingly connected to the mounting hole.

[0013] In some embodiments that can be implemented, the compression column is connected to a pressure plate at the end away from the unit pressure head, and the pressure plate uniformly transmits the concentrated load of the loading device pressure head to one end of the compression column.

[0014] In some embodiments that can be implemented, after the compression columns with different elastic modulus consume part of the pressure value, the load is transmitted to the surface of the physical model of the tunnel to be tested through the unit pressure head, wherein the expression of the loading process of the complex stress field is:

[0015]

[0016] In the formula: is the load applied by the outside world, is the surface area of the pressure plate, is the elastic modulus of the unit column, is the strain of the compression column, is the unit stress value loaded on the model.

[0017] In some embodiments, each compression column is composed of elastic modulus micro-units with different magnitudes, and the physical model three-dimensional stress field is obtained according to a tunnel engineering prototype and based on similarity theory, and the unit division and normalization calculation of the physical model three-dimensional stress field comprises:

[0018] The physical model three-dimensional stress field can be calculated according to a tunnel engineering prototype and physical model related mechanical parameters according to similarity theory:

[0019] In the elastic range, the similarity relationship is satisfied:

[0020] In the plastic range, the similarity relationship is satisfied:

[0021] In the formula, the geometric similarity ratio is , the similarity ratio of density is , the similarity ratio of stress is , the similarity ratio of strain is , the similarity ratio of displacement is , the similarity ratio of elastic modulus is , the similarity ratio of Poisson's ratio is , the similarity ratio of cohesion is , the similarity ratio of internal friction angle is , and the similarity ratio of softening modulus is .

[0022] In some embodiments, each compression column is composed of elastic modulus micro-units with different magnitudes, and the physical model three-dimensional stress field is obtained according to a tunnel engineering prototype and based on similarity theory, and the unit division and normalization calculation of the physical model three-dimensional stress field further comprises:

[0023] According to the boundary conditions of the physical model, the physical model three-dimensional stress field is divided into four or six direction stresses, each direction stress is divided into a finite number of units, and the stress value of each unit is calculated, wherein the stress value expression is:

[0024]

[0025] Based on the stress value of each unit, the stress proportionality coefficient of each unit stress value and the maximum stress unit is obtained through normalization calculation, wherein the stress proportionality coefficient expression is:

[0026] ​​​​​

[0027] wherein, is the stress value of each unit, is the relative proportion.

[0028] In some embodiments that can be implemented, according to the stress proportion coefficient and prefabricated micro-units of different elastic modulus wherein, = to determine the micro-units of different elastic modulus that are assembled into the compression column.

[0029] In a second aspect, the application provides a test method of a complex stress field tunnel model test loading device, the method comprising:

[0030] Step S1: obtaining a real three-dimensional stress field of a tunnel engineering prototype based on an in-situ stress test or a stress inversion method;

[0031] Step S2: simplifying the tunnel engineering prototype into a test physical model according to the similarity theory, converting the real three-dimensional stress field into a physical model three-dimensional stress field based on a similarity ratio, the physical model three-dimensional stress field being divided into stress in six directions, or being simplified into a plane problem, considering a non-uniform stress field in four directions.

[0032] Step S3: obtaining a stress surface graph according to stress in each direction, dividing the stress surface graph into a finite number of units, calculating a corresponding stress value of each unit by volume integration, and calculating a relative proportion of the stress value of each unit to a maximum stress unit by normalization;

[0033] Step S4: selecting a compression column corresponding to an elastic coefficient according to the relative proportion of the stress value of each unit, placing the selected compression column in a loading frame in a stress distribution order according to the position of each unit; wherein the compression column is composed of a plurality of micro-units of different elastic modulus, the elastic modulus of the micro-units being different, the micro-units of different elastic modulus being combined into the compression column according to a complex stress mean value graph, and the complex stress field being constructed;

[0034] Step S5: assembling the loading device, placing the loading device on a loading surface of the tunnel physical model, and loading by a servo rigid press, the rigid loading being uniformly loaded onto each compression column through a load plate, and the complex stress field being loaded through different compression columns.

[0035] In some embodiments that can be implemented, in the step S4, if the corresponding unit stress value is the maximum , the corresponding compression column is composed of a micro-unit of the maximum elastic modulus, and other compression column units are according to the stress proportion coefficient Select the corresponding modulus of elasticity micro-unit body group.

[0036] Compared with the prior art, the technical solutions provided in the application have at least the following beneficial effects or advantages:

[0037] 1. The complex stress field tunnel model test loading device of the application, by using the similarity theory, the engineering prototype is designed into a similar physical model, and the complex stress field of the engineering prototype is converted into a three-dimensional simulated stress field through the similarity theory, the simulated stress field is divided into a finite number of units, the average stress of each unit is calculated, then each unit is normalized, different modulus of elasticity units are selected to realize the loading of the corresponding unit stress, the non-uniform stress field can be quantitatively realized, and by designing units without modulus of elasticity, high-precision compression columns with different compression modulus can be quantitatively manufactured by assembling, and the complex stress field can be accurately constructed.

[0038] 2. The internal loading frame is provided with two side fixed frames, which can realize accurate division and positioning of the non-uniform stress field, the lower fixed frame is provided with a certain magnetic control device, which can attract the iron unit pressure head, facilitating the installation of the whole loading device, and the device can be combined with the physical model loading clamp and is applicable to single-axis presses, double-axis presses and three-axis presses. It can be used for complex stress field tunnel engineering single-axis loading, two-way loading and three-way loading multi-stress field physical simulation test, and has strong scene adaptability, and during the use of the device, only the unit pressure head, the compression column with different modulus of elasticity, the loading frame and the pressure plate need to be assembled to complete the loading force transmission device, the device structure is simple, the manufacturing cost is low, and the device can be repeatedly used.

[0039] Additional aspects and advantages of the application will be in part apparent and in part pointed out hereinafter. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the embodiments of the application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only constitute some embodiments of the application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0041] Figure 1 is a structural schematic view of the test loading device according to the embodiment of the application;

[0042] Figure 2 is a structural schematic view of the loading assembly according to the embodiment of the application;

[0043] Figure 3is a sectional view of a loading assembly according to an embodiment of the present application;

[0044] Figure 4 is a top view of a loading assembly according to an embodiment of the present application;

[0045] Figure 5 is a schematic diagram of a compression column composed of micro-units with different elastic modulus according to an embodiment of the present application;

[0046] Figure 6 is a structural schematic diagram of a micro-unit according to an embodiment of the present application;

[0047] Figure 7 is a three-dimensional in-situ stress nephogram after deep cavern testing and inversion according to an embodiment of the present application;

[0048] Figure 8 is a schematic diagram of a top surface in-situ stress distribution calculated by a physical model according to an embodiment of the present application;

[0049] Figure 9 is a schematic diagram of a principle of averaging any unit according to an embodiment of the present application;

[0050] Figure 10 is a schematic diagram of a top surface in-situ stress after averaging according to an embodiment of the present application;

[0051] Figure 11 is a flow chart of a testing method of a test loading device according to an embodiment of the present application.

[0052] Reference signs

[0053] 1, loading assembly; 2, physical model of a tunnel to be tested; 3, supporting plate; 11, pressure plate; 12, loading frame; 121, outer frame; 122, upper frame; 123, lower frame; 13, compression column; 14, unit pressure head. DETAILED DESCRIPTION

[0054] The embodiments of the present application will be described in detail below with reference to the drawings. The embodiments described with reference to the drawings are exemplary, and it should be understood that the specific embodiments described herein are merely intended to explain the present application and not to limit the present application.

[0055] It should be noted that unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in the description herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

[0056] The terms "first", "second", "third", etc. are used only to distinguish descriptions, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. For example, the first end plate and the second end plate are only used to distinguish different end plates, and do not limit the order, the first end plate can also be named as the second end plate, and the second end plate can also be named as the first end plate, without departing from the scope of various described embodiments. And the terms "first", "second", "third" do not limit the indicated features to be different.

[0057] In the description of the embodiments of the present application, unless otherwise explicitly specified and limited, the terms "connected", "connected" and the like should be understood in a broad sense, for example, can be fixedly connected, can be detachably connected, or integrated; can be mechanically connected, can be electrically connected; can be directly connected, can be indirectly connected through an intermediate medium, can be the internal communication of two elements or the interaction relationship between two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. The meaning of "a plurality of" is at least two, that is, two and more than two.

[0058] It should be noted that in the present application, the words "in an embodiment", "exemplarily", "for example" and the like are used to represent as an example, illustration or explanation. Any embodiment or design scheme described as "in an embodiment", "exemplarily", "for example" in the present application should not be interpreted as more preferred or more advantageous than other embodiments or design schemes. In fact, the use of "in an embodiment", "exemplarily", "for example" and the like is intended to present the relevant concept in a specific way, meaning that the specific features, structures or properties described in combination with the embodiments can be contained in at least one embodiment of the present application. The appearance of the above words at various positions in the specification does not necessarily mean the same embodiment, nor is it an independent or alternative embodiment that is not mutually exclusive with other embodiments. Those skilled in the art explicitly and implicitly understand that the embodiments described herein can be combined with other embodiments.

[0059] For some canyon areas, many deep tunnel projects are often affected by the bias stress, non-uniform stress, resulting in asymmetric deformation and damage of the tunnel. The complex geophysical model test is an important means to study the tunnel engineering problem, and the corresponding test loading device is used to equivalently apply stress to the tunnel physical model, so as to effectively study the asymmetric deformation and damage process of the tunnel. The inventors find that in many underground tunnel physical model tests, the uniform stress is used for testing, which cannot meet the needs of the stability analysis of the surrounding rock of the underground cavern under the complex stress environment. Of course, there is also a gradient stress plate to realize the stress gradient loading. The device is only suitable for two-dimensional stress gradient loading, and does not give the quantitative gradient stress calculation method, and is not applicable to the complex three-dimensional stress problem. In addition, the honeycomb oil cylinder is used to realize the dynamic and gradient stress loading through the oil distribution control in the servo hydraulic system. The device has a complex structure, high manufacturing cost and complex operation.

[0060] Therefore, the inventors provide a complex stress field tunnel model test loading device and the corresponding test method. The device measures the real three-dimensional stress field of the actual tunnel project prototype, determines the elastic modulus of the compression column corresponding to different positions, and the compression column is composed of multiple micro-units. After determining the installation of the compression column and the loading assembly, the loading assembly is placed on the loading surface of the tunnel physical model, which can more accurately simulate the complex stress field of the tunnel and realize the non-uniform loading of the complex stress field. In the following, the complex stress field tunnel model test loading device and the corresponding test method will be further described through more embodiments.

[0061] Please refer to Figures 1 to 10 The embodiment provides a complex stress field tunnel model test loading device. The device comprises a supporting plate 3 and a loading assembly 1. The surface of the supporting plate 3 is used to place a tunnel physical model 2 to be tested. The loading assembly 1 is arranged on the surface of the tunnel physical model 2 to be tested in the circumferential direction. The tunnel physical model 2 to be tested is preferably a rectangular body. Each surface of the tunnel physical model 2 to be tested can be selectively arranged according to actual requirements. The loading assembly 1 is internally provided with multiple small units with different elastic moduli. The loading assembly 1 is used to apply different stress values to different positions of the surface corresponding to the tunnel physical model 2 to be tested. The loading assembly 1 can be selectively fixed with the supporting plate 3. When the loading assembly 1 only tests the top surface of the tunnel physical model 2 to be tested, the loading assembly 1 can be fixed by external force. The number of the loading assembly 1 can be selected according to experimental requirements, which is not limited herein.

[0062] Optionally, the support plate 3 is mainly used for placing the tunnel physical model 2 to be tested, so as to facilitate the stability of the tunnel physical model 2 to be tested during the test process. The tunnel physical model 2 to be tested can be a rock sample obtained from a corresponding tunnel engineering prototype, or can be obtained by 3D printing. Preferably, the tunnel physical model 2 to be tested is a rectangular body with six surfaces. During the loading test experiment, the real three-dimensional stress field is converted into a physical model three-dimensional stress field according to the similarity ratio. The physical model three-dimensional stress field can be divided into six directions of stress. For a plane problem, it can be simplified to four directions of stress. The loading assembly 1 is applied to each direction and placed. The inner surface of the loading assembly 1 is attached to the surface of the tunnel physical model 2 to be tested.

[0063] It should be noted that during the test experiment, the number of loading assemblies 1 can be selected according to actual needs. For example, five loading assemblies 1 are arranged on the surfaces of the tunnel physical model 2 to be tested. The loading assembly 1 and the support plate 3 can not be fixed. After the distribution of the compression columns 13 with different elastic moduli in the loading assembly 1 is determined, the tunnel physical model 2 to be tested is placed on the surface of the support plate 3. The loading assembly 1 is placed on each loading surface of the tunnel physical model 2 to be tested. The loading assembly 1 is uniformly loaded on the outer surface based on the single-axis press, double-axis press or three-axis press by combining the physical model loading clamp.

[0064] In some embodiments, as shown in Figures 2 to 4 The loading assembly 1 includes a loading frame 12, a compression column 13 and a unit pressure head 14. A plurality of mounting holes are provided on the surface of the loading frame 12. The compression column 13 is arranged in each mounting hole. The compression column 13 is connected to the unit pressure head 14 near one end of the tunnel physical model to be tested. Each compression column 13 is composed of different elastic modulus micro-unit bodies with different magnifications. The different elastic modulus micro-unit bodies are obtained according to the tunnel engineering prototype and based on the similarity theory to obtain the physical model three-dimensional stress field, and the unit division and normalization calculation of the physical model three-dimensional stress field are determined.

[0065] Optionally, the loading frame 12 includes an outer frame 121, an upper frame 122 and a lower frame 123. The outer frame 121 surrounds to form an internal area which is a rectangular cavity. The upper frame 122 and the lower frame 123 are stacked in the internal area. Each mounting hole penetrates the upper frame 122 and the lower frame 123 in turn, and the distance between adjacent mounting holes is equal. The plurality of mounting holes are arranged in an array.

[0066] In some embodiments, the outer frame 121, the upper frame 122 and the lower frame 123 can be integrally formed, a cavity region can be spaced between the upper frame 122 and the lower frame 123, a sunken groove is reserved at the top of the upper frame 122 and the bottom of the lower frame 123, a unit pressure head 14 is arranged in the groove at the bottom end of the lower frame 123, one end of the unit pressure head 14 extends into the mounting hole and abuts against the surface of the compression column 13, the compression column 13 is in sliding connection with the mounting hole, and the pressure plate 11 is connected to the end of the compression column 13 away from the unit pressure head 14. The pressure plate 11 is configured to uniformly transmit the stress applied to the surface of the pressure plate 11 away from the compression column 13 to each compression column 13.

[0067] It should be noted that, in combination with Figure 3 It is shown that the lower frame 123 is magnetically connected with the unit pressure head 14. Specifically, the unit pressure head 14 can be made of high-hardness steel material, and the shape of the unit pressure head 14 can be a cylindrical inverted T shape. The lower frame 123 can be made of magnetic material, so that the lower frame 123 is magnetically connected with the unit pressure head 14. The inner circumferential wall of the groove at the top of the upper frame 122 can abut against the pressure plate 11, or the pressure plate 11 is spaced apart from the inner circumferential wall of the sunken groove at the top of the upper frame 122 by a certain space. When the load is applied to the outer surface of the pressure plate 11, the stress is uniformly applied to each compression column. Thus, the inner loading frame is provided with two side fixed frames, which can realize accurate division and positioning of the non-uniform stress field. The lower fixed frame has a certain magnetic attraction control device, which can attract the iron pressure head, thereby facilitating installation of the entire loading device.

[0068] It should be further noted that, during the load loading process, since the hardness of the different physical models 2 to be measured is different, and the stroke of the pressure plate 11, the compression column 13 and the unit pressure head 14 is actually small, the depth of the sunken groove reserved at the top of the upper frame 122 and the bottom of the lower frame 123 can be selected according to actual needs,

[0069] Optionally, the mounting holes provided in the loading frame 12 can be arranged in a 9x9 array as shown in Figure 4 Of course, it can also be 6x6 or 12x12, and the specific arrangement can be selected according to actual needs. Of course, it can be understood that the more dense the mounting holes are arranged, that is, the more compression columns 13 are arranged in the loading frame 12, the more accurate the non-uniform stress field loaded is, and the better the effect of simulating the complex stress field tunnel model test is.

[0070] As shown in Figures 5 to 10As shown, the specific process for selecting the mounting hole on the surface of the loading frame 12 and the elastic modulus of the compression column 13 is as follows: by obtaining the corresponding real three-dimensional stress field and converting it into the physical model three-dimensional stress field according to the similarity ratio, the stress in each direction is plotted into a stress surface graph, which is divided into a finite number of units (such as Figure 9 As shown), the stress value of each unit is calculated by volume integration, the relative proportion of the stress value of each unit to the maximum stress unit is calculated by normalization, and the compression column with the corresponding elastic coefficient is selected according to the relative proportion of the stress value of each unit, and the compression column is placed in the loading frame according to the stress distribution order according to the unit position.

[0071] It can be understood that the number of divided units represents the number of openings of the loading frame 12 and the number of compression columns arranged, and according to the structure of the test loading device, after the compression columns 13 with different elastic moduli consume part of the pressure value, the load is transmitted to the surface of the physical model of the tunnel to be tested through the unit pressure head 14, wherein the loading process expression of the complex stress field is:

[0072]

[0073] In the formula: P is the load applied by the outside world, A is the surface area of the pressure plate, E is the elastic modulus of the unit column, ε is the strain of the compression column, σ is the unit stress value loaded on the model.

[0074] Optionally, as shown in Figure 5 Each compression column 13 is composed of different elastic modulus micro-unit bodies with different magnifications, and the different elastic modulus micro-unit bodies with different magnifications are obtained according to the tunnel engineering prototype and based on the similarity theory to obtain the physical model three-dimensional stress field, and the unit division and normalization calculation of the physical model three-dimensional stress field are determined.

[0075] It should be noted that the micro-unit body can be made of plastic materials with different elastic modulus magnifications, or made of elastic materials with different elastic modulus magnifications, and the micro-unit body can be set to have equal proportional or equal difference elastic modulus, as shown in Figure 5 The different elastic modulus micro-unit bodies can be =1E, =2E… =bE, for the compression columns 13 with different elastic moduli, the micro-unit bodies with different elastic modulus magnifications can be selected, but it should be noted that in order to ensure that the lengths of all compression columns 13 are the same, each compression column 13 is composed of the same number of micro-unit bodies.

[0076] It should be further noted that, asFigure 6 As shown, Figure 6 The structure of the micro unit is shown, and the opposite surfaces of the micro unit are connected by the grooves and the pins. When the micro unit is assembled into the compression column 13, the pin of one micro unit is matched with the groove of the next micro unit to realize connection and assembly into the compression column 13. Of course, the micro unit can also be assembled into the compression column 13 in other structures.

[0077] Optionally, as Figures 7 to 10 As shown, in the process of determining the elastic modulus of each compression column 13, first, the three-dimensional stress field of the physical model can be calculated according to the tunnel engineering prototype and the related mechanical parameters of the physical model according to the similarity theory:

[0078] In the elastic range, the similarity relationship is satisfied: ; ; ;

[0079] In the plastic range, the similarity relationship is satisfied: ; ;

[0080] In the formula, the geometric similarity ratio is , the similarity ratio of density is , the similarity ratio of stress is , the similarity ratio of strain is , the similarity ratio of displacement is , the similarity ratio of elastic modulus is , the similarity ratio of Poisson's ratio is , the similarity ratio of cohesion is , the similarity ratio of internal friction angle is , and the similarity ratio of softening modulus is .

[0081] According to the boundary conditions of the physical model, the three-dimensional stress field of the physical model is divided into four or six directions of stress, each direction of stress is divided into a finite number of units, and the stress value of each unit is calculated, wherein the stress value expression is:

[0082]

[0083] According to the stress value of each unit, the stress ratio coefficient of each unit stress value and the maximum stress unit is calculated based on normalization, wherein the stress ratio coefficient expression is:

[0084]

[0085] In the formula, is the stress value of each unit, This refers to a relative proportion.

[0086] According to the stress proportionality coefficient And prefabricated micro-units with different ratios of elastic modulus ,in, = To determine the micro-units assembled into a compressed column (such as...) Figure 5 As shown), specifically, by processing and manufacturing micro-units with elastic modulus of different magnifications. Thus, compression columns 13 with different elasticity simulations can be achieved through the free combination of micro-units.

[0087] It is understood that the complex geostress field tunnel model test loading device in the above embodiment designs a similar physical model of the engineering prototype through similarity theory, transforms the complex geostress field of the engineering prototype into a three-dimensional simulated stress field through similarity theory, divides the transformed simulated geostress field into a finite number of units, calculates the average stress magnitude of each unit, and then normalizes each unit. By selecting units with different elastic moduli, the corresponding unit stress can be loaded, and a non-uniform stress field can be quantitatively realized. Furthermore, by designing units that do not require elastic moduli, and by assembling them, high-precision compression columns with different compression moduli can be quantitatively manufactured, thereby achieving the precise construction of a complex stress field.

[0088] Furthermore, the loading frame features two fixed frames on either side, enabling precise division and positioning of non-uniform stress fields. The lower fixed frame has a magnetic control device to hold the iron unit indenter, facilitating the installation of the entire loading device. The device can be combined with physical model loading fixtures and is applicable to single-axis, bi-axis, and tri-axis presses. It can be used for multi-stress field physical simulation tests of single-axis, bi-axis, and tri-axis loading in tunnel engineering with complex geostress fields, exhibiting strong adaptability to various scenarios. During use, the loading force transmission device is completed simply by assembling the unit indenter, compression columns with different elastic moduli, the loading frame, and the pressure plate. The device has a simple structure, low manufacturing cost, and is reusable.

[0089] Please see Figures 7 to 11 This embodiment provides a test method for a loading device in a tunnel model test of a complex geostress field, the method including:

[0090] Step S1: Obtain the real three-dimensional geostress field of the tunnel engineering prototype based on methods including in-situ geostress testing or geostress inversion;

[0091] In this step, the true three-dimensional geostress field of the tunnel prototype is obtained through in-situ geostress testing and geostress inversion; that is, as shown in the figure. Figure 7The in-situ stress test result and the engineering prototype stress field obtained by inversion are shown in combination. The in-situ stress test and stress inversion method are prior art, and will not be described here.

[0092] Step S2: According to the similarity theory, the tunnel engineering prototype is simplified into a test physical model, and the real three-dimensional stress field is converted into a physical model three-dimensional stress field based on the similarity ratio. The physical model three-dimensional stress field includes stress in six directions;

[0093] In this step, according to the similarity theory, the tunnel engineering prototype is simplified into a test physical model, and the real three-dimensional stress field is converted into a physical model three-dimensional stress field based on the similarity ratio. The stress in six directions can be divided into six directions (the plane problem can be simplified into four directions of stress), that is, as shown in Figure 8 The complex stress distribution diagram of the top of the tunnel physical model is shown in the similarity theory calculation.

[0094] Step S3: According to the stress in each direction, a stress surface diagram is obtained, the stress surface diagram is divided into a finite number of units, the stress value of each unit is calculated by volume integration, and the relative proportion of the stress value of each unit to the maximum stress unit is calculated by normalization;

[0095] In this step, the stress surface diagram is drawn for each direction of stress, which is divided into a finite number of units, and the stress value of each unit is calculated by volume integration, that is, as shown in Figure 9 The unit stress averaging calculation process is shown. The relative proportion of the stress value of each unit to the maximum stress unit is calculated by normalization, as shown in Figure 10 The complex stress averaging diagram of the top of the tunnel physical model is shown.

[0096] Step S4: According to the relative proportion of the stress value of each unit, a compression column corresponding to the elastic coefficient is selected, and the compression column is placed in the loading frame in the stress distribution order according to the position of each unit; wherein the compression column is composed of a plurality of different elastic modulus micro units, the elastic modulus of the micro unit body is different, different elastic modulus micro units are composed into a compression column according to the complex stress averaging diagram, and the construction of the complex stress field is realized;

[0097] In this step, according to the relative proportion of the stress value of each unit, a compression column corresponding to the elastic coefficient is selected, and the compression column is placed in the loading frame in the stress distribution order according to the position of each unit. Figure 5 As shown, the compression column can be composed of a plurality of different elastic modulus micro units, each micro unit can be made into different elastic modulus, different elastic modulus micro units are composed into a compression column according to the complex stress averaging diagram, and the construction of the complex stress field is realized, wherein the maximum The maximum elastic modulus stainless steel micro unit is used to compose the compression column unit, and other compression column units are composed according to the stress proportion coefficient Select the elastic modulus micro-unit corresponding to the selected magnification.

[0098] Step S5: Assemble the loading device, place the loading device on the loading surface of the tunnel physical model, and load through the servo rigid press. The rigid loading is uniformly loaded to each compression column through the load plate, and the complex stress field is loaded through different compression columns.

[0099] In this step, the loading device is assembled, placed on the loading surface of the tunnel physical model, and loaded through the servo rigid press. The rigid loading is uniformly loaded to each compression column through the load plate, and the complex stress field is loaded through different compression columns.

[0100] In the above method steps, the loading test of the complex stress field tunnel physical model can be realized, and the following advantages are mainly provided:

[0101] (1) The device structure is simple, the manufacturing cost is low, and it can be reused. As long as the unit pressure head, different elastic modulus compression columns, loading frames and pressure plates are assembled, the loading force transmission device can be completed.

[0102] (2) Quantitative non-uniform stress field can be realized. A method for quantitatively constructing a non-uniform stress field is provided, and a micro-element of different elastic modulus units is designed. Through assembly, high-precision compression columns with different compression modulus can be quantitatively manufactured, and the complex stress field can be accurately constructed.

[0103] (3) The loading frame is provided with two side fixed frames, which can realize accurate division and positioning of the non-uniform stress field. The lower fixed frame is provided with a certain magnetic control device, which can attract the iron pressure head, and the installation of the whole loading device is facilitated.

[0104] (4) The device has strong scene adaptability. The device can be combined with the physical model loading clamp, and is applicable to single-axis press, double-axis press and three-axis press, and can be used for complex stress field tunnel engineering single-axis loading, two-way loading and three-way loading multi-stress field physical simulation test.

[0105] In the description of the present application, it should be understood that the orientations or positional relationships indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like are based on the orientations or positional relationships shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the application.

[0106] In the description of the application within this specification, reference can be made to terms such as "one embodiment", "some embodiments", "certain embodiments" or "an embodiment" among others. Such terminology can mean that a particular feature, structure, material or characteristic is included in at least one embodiment of the application. Such terminology can also mean that a particular feature, structure, material or characteristic is included in at least one, but not necessarily all embodiments of the application. Further, such terminology can mean that a particular feature, structure, material or characteristic is included in one or more embodiments of the application.

[0107] It is clear that the described embodiments are only some of the embodiments of the application and not all of the embodiments. Reference in this specification to "an embodiment" means that a particular feature, structure, material or characteristic described in connection with the embodiment is included in at least one embodiment of the application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment or to the same alternative embodiment. It is explicitly contemplated that one or more features, structures, materials or characteristics described in connection with an embodiment can be combined with features, structures, materials or characteristics of another embodiment or alternative embodiment. It is further understood that the embodiments described herein can be combined with any other embodiment unless explicitly stated otherwise.

[0108] Although embodiments of the application have been illustrated and described, it will be clear to those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made thereto without departing from the spirit and scope of the application, which should be limited only by the scope of the claims and the equivalents thereof.

[0109] Other embodiments of the present application will be apparent to those skilled in the art from consideration of the specification and practice of the application disclosed herein. It is intended that the present application cover any and all variations of the application that come within the scope of the claims and their equivalents. It is intended that the specification and examples be considered exemplary only, with the true scope and spirit of the application being indicated by the following claims.

Claims

1. A loading device for a tunnel model test of a complex stress field, characterized in that, The utility model relates to a tunnel physical model loading device, including: A pallet (3) is placed on the surface of the tunnel physical model to be measured; A loading assembly (1) is provided with a plurality of small units with different elastic modulus, and the loading assembly (1) is used to apply different stress value loads to different positions on the surface corresponding to the tunnel physical model to be measured; wherein, The loading assembly (1) includes a loading frame (12), a compression column (13) and a unit pressure head (14), a plurality of mounting holes are provided on the surface of the loading frame (12), the compression column (13) is arranged in each mounting hole, one end of the compression column (13) close to the tunnel physical model to be measured is connected with the unit pressure head (14), wherein each compression column (13) is composed of different elastic modulus micro-unit bodies, the different elastic modulus micro-unit bodies are obtained according to the tunnel engineering prototype and based on the similarity theory, the physical model three-dimensional stress field is divided and normalized, and the calculation is determined; Wherein, the loading frame (12) includes: An outer frame (121) is provided with an internal area; An upper frame (122) and a lower frame (123) are arranged in the internal area, each mounting hole penetrates the upper frame (122) and the lower frame (123) in sequence, the distance between adjacent mounting holes is equal, and a plurality of mounting holes are arranged in an array; The lower frame (123) is provided with the unit pressure head (14) at the bottom end surface, the lower frame (123) and the unit pressure head (14) are magnetically connected, and one end of the unit pressure head (14) extends into the mounting hole and is in contact with the surface of the compression column (13), the compression column (13) and the mounting hole are slidingly connected; The compression column (13) is connected with a pressure plate (11) at one end away from the unit pressure head (14), and the pressure plate (11) uniformly transmits the concentrated load of the loading device pressure head to one end of the compression column (13); After the compression column (13) with different elastic modulus consumes part of the pressure value, the load is transmitted to the surface of the tunnel physical model to be measured through the unit pressure head (14), wherein the loading process expression of the complex stress field is: where F is the externally applied load, A is the surface area of the compression plate, E is the modulus of elasticity of the compression column, ε is the strain of the compression column under compression, σ is the cell stress value applied to the model.

2. The loading device for a tunnel model test of a complex stress field according to claim 1, wherein Each compression column (13) is composed of different elastic modulus micro-unit bodies, the different elastic modulus micro-unit bodies are obtained according to the tunnel engineering prototype and based on the similarity theory, the physical model three-dimensional stress field is divided and normalized, and the calculation is determined, including: The physical model three-dimensional stress field can be calculated according to the tunnel engineering prototype and the related mechanical parameters of the physical model according to the similarity theory: In the elastic range the similarity relation is satisfied: ; ; ; In the plastic range the similarity relation is satisfied: wherein: the geometric similarity ratio is , the density similarity ratio is , the stress similarity ratio is , the strain similarity ratio is , the displacement similarity ratio is , the elastic modulus similarity ratio is , the Poisson's ratio similarity ratio is , the cohesion similarity ratio is , the internal friction angle similarity ratio is , the softening modulus similarity ratio is .

3. The loading device for a complex stress field tunnel model test according to claim 1, characterized in that, Each of the compression columns (13) is composed of micro-unit bodies with different elastic modulus ratios, the micro-unit bodies with different elastic modulus ratios are obtained according to a tunnel engineering prototype and based on a similarity theory to obtain a physical model three-dimensional stress field, and unit division and normalization calculation of the physical model three-dimensional stress field are determined, and further comprising: According to the boundary conditions of the physical model, the physical model three-dimensional stress field is divided into four or six direction stresses, each direction stress is divided into a finite number of units, and the stress value of each unit is calculated, wherein the stress value expression is: According to the stress value of each unit, based on the normalization calculation, the stress ratio coefficient of each unit stress value and the maximum stress unit is obtained, wherein the stress ratio coefficient expression is: In the formula, is the stress value for each unit, is the relative proportion.

4. The loading device for a complex stress field tunnel model test according to claim 3, characterized in that, According to the stress ratio coefficient and preformed micro-cells of different elastic modulus ratios wherein, to determine micro-cells to be assembled into the compression column (13).

5. A test method of the complex stress field tunnel model test loading device according to any one of claims 1 to 4, the method comprising: Step S1: obtaining a real three-dimensional ground stress field of a tunnel engineering prototype based on in-situ ground stress test or ground stress inversion method; Step S2: simplifying the tunnel engineering prototype into a test physical model according to the similarity theory, and converting the real three-dimensional ground stress field into a physical model three-dimensional stress field based on a similarity ratio, the physical model three-dimensional stress field is divided into six direction stresses, or it is simplified into a plane problem, considering four direction non-uniform stress field; Step S3: obtaining a stress surface graph according to each direction stress, dividing the stress surface graph into a finite number of units, calculating the corresponding stress value of each unit by volume integration, and calculating the relative proportion of each unit stress value and the maximum stress unit by normalization; Step S4: according to the relative proportion of each unit stress value, selecting a compression column with corresponding elastic coefficient, and placing the selected compression column in the loading frame according to the stress distribution order according to the position of each unit; wherein the compression column is composed of a plurality of micro-unit bodies with different elastic modulus ratios, the elastic modulus ratios of the micro-unit bodies are different, the micro-unit bodies with different elastic modulus ratios are composed of the compression column according to the complex stress mean value graph, and the complex stress field is constructed; Step S5: assembling the loading device, placing the loading device on the loading surface of the tunnel physical model, and loading by a servo rigid press, the rigid loading is uniformly loaded to each compression column through a load plate, and the complex stress field is loaded through different compression columns.

6. The testing method of the loading device for the complex stress field tunnel model test according to claim 5, in step S4, if the corresponding unit stress value is the maximum , the corresponding compression column is composed of the micro-unit body with the maximum elastic modulus, and the other compression column units are selected according to the stress proportionality coefficient to select the micro-unit body with the corresponding elastic modulus.

Images