Complex crustal stress field tunnel model test loading device and test method

Abstract

The invention belongs to the technical field of tunnel physical simulation test stress field equipment, and particularly discloses a complex crustal 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, and the loading assembly is attached to the surface of a to-be-loaded tunnel physical model; under the action of an external load, the construction of a non-uniform stress field on the surface of the to-be-tested tunnel physical model is realized through the adjustment of the loading assembly; the loading assembly comprises a loading frame, a compression column and a unit pressure head, a mounting hole is formed in the surface of the loading frame, the compression column is arranged in the mounting hole, the end, close to the to-be-tested tunnel physical model, of the compression column is connected with the unit pressure head, and the compression column is composed of elastic modulus micro unit bodies with different multiplying power; the elastic moduli with different multiplying powers are determined by obtaining a three-dimensional stress field required by a physical model test through a similarity theory according to a real stress field of a tunnel engineering prototype and then carrying out unit division and normalization on the three-dimensional stress field of the physical model, and the device can realize non-uniform loading of a complex ground stress field.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel physical simulation test stress field equipment, and in particular relates to a complex geostress field tunnel model test loading device and a test method. Background Art

[0002] For tunnel engineering, many deep tunnel projects are often affected by eccentric geostress and non-uniform geostress, which leads to asymmetric and non-coordinated deformation and damage of the tunnel. Complex geophysical model test is an important means to study tunnel engineering problems.

[0003] In the prior art, many physical model tests of underground tunnels are conducted according to uniform geostress. For example, an existing method applies axial pressure to both ends of a rock sample through a cylinder, applies confining pressure to the outer wall, and applies internal pressure to the inner wall. The entire sample is in an axisymmetric stress state to achieve uniform stress. This device is only suitable for loading rock samples, and it is difficult to quantitatively control the size of non-uniform stress fields. At the same time, for a small number of devices for testing non-uniform geostress, for example, using a honeycomb oil cylinder, dynamic and gradient stress loading is achieved through oil circuit control in a servo hydraulic system. Due to the setting of the hydraulic system and the oil circuit, the device design structure is complex, the manufacturing cost is high, and the operation is also relatively complicated. Therefore, the existing loading device for tunnel model tests with complex geostress fields is still immature, and it is urgent to design a test device with simple structure and operation, which can more accurately simulate the complex geostress field of the tunnel and achieve non-uniform loading of the complex geostress field. Summary of the invention

[0004] The present invention aims to solve the problem that the loading devices used in the prior art for tunnel model tests on complex geostress fields are not applicable to complex three-dimensional geostress 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 proposes a loading device and a testing method for tunnel model tests on complex geostress fields.

[0005] In order to achieve the above objectives, in a first aspect, the present application provides a loading device for a tunnel model test in a complex geostress field, comprising: A support plate, on the surface of which a physical model of the tunnel to be tested is placed; A loading component, wherein the loading component has a plurality of small units with different elastic moduli built therein, and the loading component is used to apply loads of different stress values ​​at different locations on the surface corresponding to the physical model of the tunnel to be tested; wherein, The loading assembly includes a loading frame, a compression column and a unit pressure head. A plurality of mounting holes are formed through the surface of the loading frame. The compression column is arranged in each mounting hole. The compression column is connected to the unit pressure head at one end close to the physical model of the tunnel to be tested. Each of the compression columns is composed of micro-unit bodies with elastic modulus of different magnifications. The micro-unit bodies with elastic modulus of different magnifications are obtained according to the tunnel engineering prototype and based on similarity theory to obtain the three-dimensional stress field of the physical model, and the three-dimensional stress field of the physical model is determined by unit division and normalization calculation.

[0006] In some possible embodiments, the loading frame includes: An outer frame, the outer frame is arranged to surround an inner area; An upper frame and a lower frame are stacked in the internal area, each of the mounting holes passes through the upper frame and the lower frame in sequence, and the distances between adjacent mounting holes are equal, and a plurality of mounting holes are arranged in an array.

[0007] In some possible embodiments, the unit pressure head is provided on the bottom end surface of the lower frame, the lower frame is magnetically connected to the unit pressure head, and one end of the unit pressure head extends into the mounting hole and contacts the surface of the compression column, and the compression column is slidably connected to the mounting hole.

[0008] In some possible embodiments, one end of the compression column away from the unit pressure head is connected to a pressure plate, and the pressure plate evenly transfers the concentrated load of the loading device pressure head to one end of the compression column.

[0009] In some possible embodiments, after the compression columns 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, wherein the loading process expression of the complex geostress field is: Where: The load imposed by the outside world, is the surface area of ​​the pressure plate, is the elastic modulus of the unit column, is the compression strain of the compression column, is the element stress value loaded on the model.

[0010] In some possible embodiments, each of the compression columns is composed of micro-units of elastic modulus with different magnifications, and the micro-units of elastic modulus with different magnifications are used to obtain a three-dimensional stress field of a physical model based on a tunnel engineering prototype and similarity theory, and the three-dimensional stress field of the physical model is divided into units and normalized and calculated and determined, including: The three-dimensional stress field of the physical model can be calculated according to the tunnel engineering prototype and the relevant mechanical parameters of the physical model according to the similarity theory: In the elastic range, similarity relations are satisfied: ; ; ; In the plastic range, similarity relations are satisfied: ; ; Where: 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 the internal friction angle is , the similarity ratio of softening modulus is .

[0011] In some possible embodiments, each of the compression columns is composed of micro-units of elastic modulus with different magnifications, and the micro-units of elastic modulus with different magnifications obtain a three-dimensional stress field of a physical model based on a tunnel engineering prototype and similarity theory, and perform unit division and normalization calculation and determination on the three-dimensional stress field of the physical model, further comprising: According to the boundary conditions of the physical model, the three-dimensional stress field of the physical model is divided into stresses in four or six directions, the stress in each direction is divided into a finite number of units, and the stress value of each unit is calculated respectively, wherein the stress value expression is: According to the stress value of each unit, the stress proportionality coefficient between the stress value of each unit and the maximum stress unit is obtained based on normalization calculation, wherein the stress proportionality coefficient expression is: In the formula, is the stress value for each element, For relative proportions.

[0012] In some possible embodiments, according to the stress proportionality coefficient And prefabricated micro-units with different elastic modulus ratios ,in, = to determine the microunits assembled into the compressed column.

[0013] In a second aspect, the present application provides a method for testing a loading device for a tunnel model test in a complex geostress field, the method comprising: Step S1: obtaining a true three-dimensional geostress field of a tunnel engineering prototype based on an in-situ geostress test or a geostress inversion method; Step S2: Simplify the tunnel engineering prototype into an experimental physical model according to similarity theory, and convert the real three-dimensional ground stress field into a three-dimensional stress field of the physical model based on the similarity ratio. The three-dimensional stress field of the physical model is divided into stresses in six directions, or simplified into a plane problem, considering the non-uniform stress fields in four directions.

[0014] Step S3: obtaining a stress surface diagram according to the stress in each direction, dividing the stress surface diagram into a finite number of units, calculating the corresponding stress value of each unit by volume integral, and calculating the relative ratio of the stress value of each unit to the maximum stress unit by normalization; Step S4: According to the relative proportion of the stress values ​​of each unit, a compression column with a corresponding elastic coefficient is selected, and the selected compression column is placed 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-units with different elastic moduli, and the elastic modulus magnifications of the micro-units are different. According to the complex stress averaging diagram, the micro-units with different magnifications of elastic moduli are combined into the compression column to realize the construction of a complex geostress field; Step S5: Assemble the loading device, place it on the loading surface of the tunnel physical model, and load it through a servo rigid press. Rigid loading evenly loads stress to each compression column through the load plate, and realizes loading of complex stress fields through different compression columns.

[0015] In some possible embodiments, in step S4, if the corresponding unit stress value is the maximum , then the corresponding compression column is composed of the micro-unit with the maximum elastic modulus, and the other compression column units are based on the stress proportionality coefficient Select the elastic modulus microunit composition of the corresponding ratio.

[0016] Compared with the prior art, the technical solution provided in the present application has at least the following beneficial effects or advantages: 1. The complex geostress field tunnel model test loading device of the present application designs a similar physical model through similarity theory of the engineering prototype, converts the complex geostress field of the engineering prototype into a three-dimensional simulated stress field through similarity theory, divides the converted simulated geostress field into a finite number of units, calculates the average stress of each unit, and then normalizes each unit. By selecting units with different elastic modulus to realize the loading of the corresponding unit stress, the non-uniform stress field can be quantitatively realized, and then by designing units without elastic modulus units and assembling compression columns with different compression moduli that can be quantitatively produced with high precision, the precise construction of the complex stress field can be realized.

[0017] 2. The loading frame is provided with fixed frames on both sides to realize the accurate division and positioning of the non-uniform stress field. The lower fixed frame has a certain magnetic control device that can absorb the iron unit pressure head, which is convenient for the installation of the entire loading device. At the same time, the device can be combined with the physical model loading fixture, which is applicable to uniaxial presses, biaxial presses and triaxial presses. It can be used for multi-stress field physical simulation tests of uniaxial loading, bidirectional loading and triaxial loading in tunnel engineering with complex geostress fields. It has strong adaptability to scenarios. During the use of the device, the loading and force transmission device can be completed by assembling the unit pressure head, compression columns with different elastic moduli, loading frames and pressure plates. The device has a simple structure, low production cost and can be reused.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 is a schematic structural diagram of a test loading device according to an embodiment of the present application; Figure 2 is a schematic structural diagram of a loading component according to an embodiment of the present application; Figure 3 is a cross-sectional view of a loading assembly according to an embodiment of the present application; Figure 4 is a top view of a loading assembly according to an embodiment of the present application; Figure 5 is a schematic diagram of a compression column composed of microunits with different elastic moduli according to an embodiment of the present application; Figure 6is a schematic structural diagram of a micro unit body according to an embodiment of the present application; Figure 7 It is a three-dimensional geostress cloud map after deep cavern testing and inversion according to an embodiment of the present application; Figure 8 is a schematic diagram of top surface ground stress distribution calculated according to the physical model shown in the embodiment of the present application; Fig. 9 is a schematic diagram of the averaging principle of any unit shown in an embodiment of the present application; Fig.10 is a schematic diagram of the averaged ground stress on the top surface of the physical model according to an embodiment of the present application; Fig.11 It is a flow chart of a testing method of a test loading device according to an embodiment of the present application.

[0021] Reference numerals 1. Loading assembly; 2. Physical model of the tunnel to be tested; 3. Support 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

[0022] The embodiments of the present invention are described in detail below. The embodiments described with reference to the accompanying drawings are exemplary. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0023] It should be noted that, unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0024] The terms "first", "second", "third", etc. are only used to distinguish descriptions and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. For example, the first end plate and the second end plate are only used to distinguish different end plates, and their order is not limited. 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 the various described embodiments. And the terms "first", "second", "third", etc. do not limit the indicated features to be different.

[0025] In the description of the embodiments of the present application, unless otherwise clearly specified and limited, the terms "connected", "connection", etc. should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances. The meaning of "plurality" is at least two, that is, two or more.

[0026] It should be noted that, in the present application, words such as "in one embodiment", "exemplarily", "for example", etc. are used to indicate examples, illustrations or descriptions. Any embodiment or design described in the present application as "in one embodiment", "exemplarily", "for example" should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "in one embodiment", "exemplarily", "for example", etc. is intended to present related concepts in a concrete way, meaning that specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present application. The appearance of the above words in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] For some canyon areas, many deep tunnel projects are often affected by partial stress and non-uniform stress, resulting in asymmetric and coordinated deformation and damage of the tunnel. Complex geophysical model test is an important means to study tunnel engineering problems. The corresponding test loading device is used to apply equivalent stress to the tunnel physical model to effectively study the asymmetric and coordinated deformation and damage process of the tunnel. The inventor found that many underground tunnel physical model tests are carried out according to uniform stress, which cannot meet the needs of underground cavern surrounding rock stability analysis under complex stress environment. Of course, there is also a method of realizing stress gradient loading through gradient stress plate; this device is only suitable for two-dimensional stress gradient loading, and no quantitative gradient stress calculation method is given, which is not applicable to complex three-dimensional stress problems, and uses honeycomb cylinders to realize dynamic and gradient stress loading through oil circuit control in the servo hydraulic system; the device has a complex design structure, high manufacturing cost and complex operation.

[0028] Therefore, the inventors proposed a loading device for a tunnel model test of a complex geostress field and a corresponding testing method. The device determines the elastic modulus of compression columns corresponding to different locations by measuring the prototype real three-dimensional geostress field of an actual tunnel project. The compression column is composed of a plurality of micro-units. After determining that the compression column is installed to form a loading assembly, the loading assembly is placed on the loading surface of the tunnel physical model to more accurately simulate the complex geostress field of the tunnel and realize non-uniform loading of the complex geostress field. Below, the loading device for a tunnel model test of a complex geostress field and the corresponding testing method will be further described through more embodiments.

[0029] See also Figures 1 to 10 The present embodiment provides a loading device for a tunnel model test in a complex geostress field, the device comprising a support plate 3 and a loading component 1, the surface of the support plate 3 is used to place a tunnel physical model 2 to be tested, a loading component 1 in contact with the surface of the tunnel physical model 2 to be tested is arranged circumferentially, 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 component 1 has multiple built-in small units with different elastic moduli, the loading component 1 is used to apply different magnitude stress value loads to different locations on the surface corresponding to the contact with the tunnel physical model 2 to be tested, the loading component 1 can be selectively fixed to the support plate 3, when the loading component 1 is only used to test the top surface of the tunnel physical model 2 to be tested, it can be fixed by external force, at the same time, the number of loading components 1 to be set can be selected according to experimental requirements, and is not limited here.

[0030] Optionally, the support plate 3 is mainly used to place the physical model 2 of the tunnel to be tested, so as to ensure the stability of the physical model 2 of the tunnel to be tested during the test process. The physical model 2 of the tunnel to be tested can be a rock sample obtained from the corresponding tunnel engineering prototype, or can be obtained through 3D printing. Preferably, the physical model 2 of the tunnel to be tested is a rectangular body with six faces. During the loading test experiment, the real three-dimensional geostress field is converted into the three-dimensional stress field of the physical model according to the similarity ratio. The three-dimensional stress field of the physical model can be divided into stresses in six directions. At the same time, the plane problem can be simplified to stresses in four directions. The loading component 1 is applied and placed in each direction, and the inner surface of the loading component 1 is in contact with the surface of the physical model 2 of the tunnel to be tested.

[0031] It should be noted that, during the test experiment, the number of loading components 1 to be set can be selected according to actual needs. For example, loading components 1 are set on the five surfaces of the physical model 2 of the tunnel to be tested, and the loading components 1 and the support plate 3 may not be fixed in any way. After determining the compression columns 13 with different elastic moduli distributed in the loading component 1, the physical model 2 of the tunnel to be tested is placed on the surface of the support plate 3, and the loading component 1 is placed on each loading surface of the physical model 2 of the tunnel to be tested. The loading component 1 is combined with the physical model loading fixture to uniformly load stress on the outer surface of the loading component 1 based on a uniaxial press, a biaxial press or a triaxial press.

[0032] In some embodiments, Figures 2 to 4 As shown, 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 formed through the surface of the loading frame 12. A compression column 13 is arranged in each mounting hole. The compression column 13 is connected to the unit pressure head 14 at one end close to the physical model of the tunnel to be measured, wherein each compression column 13 is composed of micro-unit bodies with elastic modulus of different magnifications. The micro-unit bodies with elastic modulus of different magnifications are obtained according to the tunnel engineering prototype and based on similarity theory to obtain the three-dimensional stress field of the physical model, and the three-dimensional stress field of the physical model is determined by unit division and normalization calculation.

[0033] Optionally, the loading frame 12 includes an outer frame 121, an upper frame 122 and a lower frame 123. The outer frame 121 is surrounded by an internal area, which is a rectangular body cavity. The upper frame 122 and the lower frame 123 are stacked in the internal area. Each mounting hole passes through the upper frame 122 and the lower frame 123 in sequence, and the distances between adjacent mounting holes are equal. Multiple mounting holes are arranged in an array.

[0034] In some embodiments, the outer frame 121, the upper frame 122 and the lower frame 123 can be integrally formed, a cavity area can be separated from the upper frame 122 and the lower frame 123, a countersunk 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 on the bottom end surface of the lower frame 123, one end of the unit pressure head 14 extends into the mounting hole and contacts the surface of the compression column 13, the compression column 13 is slidably connected to the mounting hole, and a pressure plate 11 is connected to the end of the compression column 13 away from the unit pressure head 14, and the pressure plate 11 is configured to uniformly transfer the stress loaded on the surface of the pressure plate 11 away from the compression column 13 from the outside to each compression column 13.

[0035] It should be noted that, combined with Figure 3As shown, the lower frame 123 is magnetically connected to 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. In this way, the lower frame 123 and the unit pressure head 14 are magnetically connected. The pressure plate 11 and the inner circumferential wall of the groove at the top of the upper frame 122 can be in contact with each other, or a certain space is reserved between the edges of the pressure plate 11 and the inner circumferential wall of the sunken groove at the top of the upper frame 122. When the load is applied to the outer surface of the pressure plate 11, the stress is evenly loaded on each compression column. In this way, fixed frames on both sides are provided inside the loading frame, which can realize the precise division and positioning of the non-uniform stress field. The lower fixed frame has a certain magnetic control device, which can absorb the iron pressure head and facilitate the installation of the entire loading device.

[0036] It should also be noted that during the load loading process, due to the different hardness of the different tunnel physical models 2 to be tested, and the strokes of the pressure plate 11, the compression column 13 and the unit pressure head 14 are actually small, the depth of the reserved countersunk grooves at the top of the upper frame 122 and the bottom of the lower frame 123 can be selected according to actual needs. Optionally, the mounting holes provided in the loading frame 12 may be as follows: Figure 4 The 9×9 array arrangement shown can, of course, also be 6×6 or 12×12, etc. The specific arrangement can be selected according to actual needs. Of course, it can be understood that the denser the mounting holes are, 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 complex geostress field tunnel model test is.

[0037] like Figures 5 to 10 As shown, the specific process of selecting the elastic modulus of the mounting holes and the compression column 13 on the surface of the loading frame 12 is as follows: by obtaining the corresponding real three-dimensional ground stress field and converting it into a physical model three-dimensional stress field according to the similarity ratio, a stress surface diagram is drawn for the stress in each direction, and it is divided into a finite number of units (such as Fig. 9 As shown in the figure, 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. According to the relative proportion of the stress value of each unit, the compression column with the corresponding elastic coefficient is selected, and the compression column is placed in the loading frame according to the stress distribution order according to the unit position.

[0038] It can be understood that the number of divided units represents the number of loading frames 12 opened and the number of compression columns set. 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 geostress field is: Where: The load imposed by the outside world, is the surface area of ​​the pressure plate, is the elastic modulus of the unit column, is the compression strain of the compression column, is the element stress value loaded on the model.

[0039] Optional, such as Figure 5 As shown, each compression column 13 is composed of micro-units of elastic modulus with different magnifications, and the micro-units of elastic modulus with different magnifications are determined by obtaining the three-dimensional stress field of the physical model based on the tunnel engineering prototype and the similarity theory, and by performing unit division and normalization calculation on the three-dimensional stress field of the physical model.

[0040] It should be noted that the micro-units can be made of plastic materials with different elastic moduli, or they can be made of elastic materials with different elastic moduli. The elastic moduli of the micro-units are set to increase in equal proportion or arithmetic difference, such as Figure 5 As shown, the micro-units with different elastic moduli can be =1E, =2E…… =bE, for compression columns 13 with different elastic moduli, they can be composed by selecting micro-units with different elastic moduli. However, 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-units.

[0041] It should also be noted that if Figure 6 As shown, Figure 6 A structure of a micro-unit body is shown. The two opposite surfaces of the micro-unit body are provided with grooves and pins. When assembled into a compression column 13, the pin of one micro-unit body cooperates with the groove of the next micro-unit body to realize connection and assembly into the compression column 13. Of course, the micro-unit bodies can also be assembled into compression columns 13 with other structures.

[0042] Optional, such as Figures 7 to 10 As shown, in the specific 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 mechanical parameters related to the physical model according to the similarity theory: In the elastic range, similarity relations are satisfied: ; ; ; In the plastic range, similarity relations are satisfied: ; ; Where: 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 the internal friction angle is , the similarity ratio of softening modulus is .

[0043] According to the boundary conditions of the physical model, the three-dimensional stress field of the physical model is divided into stresses in four or six directions, and the stress in each direction is divided into a finite number of units, and the stress value of each unit is calculated respectively, where the stress value expression is: According to the stress value of each unit, the stress proportionality coefficient of each unit stress value and the maximum stress unit is obtained based on normalization calculation, where the stress proportionality coefficient expression is: In the formula, is the stress value for each element, For relative proportions.

[0044] According to the stress proportionality factor And prefabricated micro-units with different elastic modulus ratios ,in, = , to determine the microunits assembled into compressed columns (e.g. Figure 5 Specifically, micro-units with different elastic moduli are produced by processing , thereby realizing compression columns 13 with different elastic simulations through free combination of micro units.

[0045] It can be understood that the complex geostress field tunnel model test loading device of the above-mentioned embodiment designs a similar physical model through similarity theory of the engineering prototype, converts the complex geostress field of the engineering prototype into a three-dimensional simulated stress field through similarity theory, divides the converted simulated geostress field into a finite number of units, calculates the average stress of each unit, and then normalizes each unit. By selecting different elastic modulus units to realize the loading of the corresponding unit stress, the non-uniform stress field can be quantitatively realized, and then by designing units without elastic modulus units and assembling compression columns with different compression moduli that can be quantitatively produced with high precision, the precise construction of the complex stress field can be realized.

[0046] In addition, the loading frame is provided with two fixed frames on both sides, which can realize the accurate division and positioning of the non-uniform stress field. The lower fixed frame has a certain magnetic control device, which can absorb the iron unit pressure head, facilitating the installation of the entire loading device. At the same time, the device can be combined with the physical model loading fixture, which is applicable to uniaxial presses, biaxial presses and triaxial presses. It can be used for multi-stress field physical simulation tests of uniaxial loading, bidirectional loading and triaxial loading in tunnel engineering with complex geostress fields. It has strong adaptability to scenarios. During the use of the device, the loading and transmission device can be completed by assembling the unit pressure head, compression columns with different elastic moduli, loading frames and pressure plates. The device has a simple structure, low manufacturing cost and can be reused.

[0047] See also Figures 7 to 11 This embodiment provides a method for testing a loading device for a tunnel model test in a complex geostress field, the method comprising: Step S1: obtaining a true three-dimensional geostress field of a tunnel engineering prototype based on an in-situ geostress test or a geostress inversion method; In this step, the real three-dimensional geostress field of the tunnel engineering prototype is obtained through in-situ geostress testing, geostress inversion and other methods; Figure 7 The engineering prototype geostress field shown is obtained by inversion in combination with the geostress test results. The in-situ geostress test, geostress inversion and other methods are prior arts and will not be elaborated here.

[0048] Step S2: simplifying the tunnel engineering prototype into an experimental physical model according to similarity theory, converting the real three-dimensional ground stress field into a three-dimensional stress field of the physical model based on a similarity ratio, wherein the three-dimensional stress field of the physical model includes stresses divided into six directions; In this step, the tunnel engineering prototype is simplified into an experimental physical model according to the similarity theory, and the real three-dimensional ground stress field is converted into a physical model three-dimensional stress field according to the similarity ratio, which can be divided into stress in six directions (the plane problem can be simplified to stress in four directions), that is, Figure 8 The similarity theoretical calculation shown above obtains the complex stress distribution diagram at the top of the tunnel physical model.

[0049] Step S3: Obtain a stress surface diagram according to the stress in each direction, divide the stress surface diagram into a finite number of units, calculate the corresponding stress value of each unit by volume integral, and calculate the relative ratio of the stress value of each unit to the maximum stress unit by normalization; In this step, a stress surface diagram is drawn for the stress in each direction, which is divided into a finite number of units. The stress value of each unit is calculated by volume integral, that is, Fig. 9 The calculation process of unit ground stress averaging is shown in Figure 2. The relative proportion of each unit stress value to the maximum stress unit is calculated by normalization, as shown in Figure 2. Fig.10Schematic diagram of complex stress averaging at the top of the tunnel physical model is shown.

[0050] Step S4: According to the relative proportion of the stress values ​​of each unit, a compression column with a corresponding elastic coefficient is selected, and the compression column is placed 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 units with different elastic moduli, and the elastic modulus magnifications of the micro units are different. According to the complex stress averaging diagram, the micro units with different magnifications of elastic moduli are combined into a compression column to realize the construction of a complex geostress field; In this step, according to the relative proportion of the stress values ​​of each unit, the compression columns with corresponding elastic coefficients are selected, and the compression columns are placed in the loading frame according to the stress distribution order according to the unit position. Figure 5 As shown in the figure, the compression column can be composed of multiple micro-units with different elastic moduli. Each micro-unit can produce elastic moduli with different magnifications. According to the complex stress averaging diagram, the micro-units with different magnifications of elastic moduli are combined into compression columns to realize the construction of complex geostress fields, in which the maximum The compression column unit is composed of stainless steel micro-units with the maximum elastic modulus, and the other compression column units are based on the stress proportionality coefficient Select the elastic modulus micro-unit composition of the corresponding ratio.

[0051] Step S5: Assemble the loading device, place it on the loading surface of the tunnel physical model, and load it through a servo rigid press. Rigid loading evenly loads stress to each compression column through the load plate, and realizes loading of complex stress fields through different compression columns.

[0052] In this step, the loading device is assembled and placed on the loading surface of the tunnel physical model. The loading is performed by a servo rigid press. The rigid loading uniformly loads the stress to each compression column through the load plate, and the loading of the complex stress field is realized through different compression columns.

[0053] In the above method steps, loading test of tunnel physical model with complex geostress field can be realized, which mainly has the following advantages: (1) The device has a simple structure, low manufacturing cost, and is reusable. The loading and force transmission device can be completed by assembling a unit pressure head, compression columns with different elastic moduli, a loading frame, and a pressure plate.

[0054] (2) It can quantitatively realize non-uniform stress fields. A method for quantitatively constructing non-uniform stress fields is proposed. Microelements that do not require elastic modulus units are designed. By assembling, compression columns with different compression moduli can be quantitatively produced with high precision, thus realizing the precise construction of complex stress fields.

[0055] (3) There are two fixed frames on both sides inside the loading frame, which can realize the precise division and positioning of the non-uniform stress field. The lower fixed frame has a certain magnetic control device that can absorb the iron pressure head, facilitating the installation of the entire loading device.

[0056] (4) The device has strong adaptability to different scenarios. The device can be combined with a physical model loading fixture and is applicable to uniaxial presses, biaxial presses, and triaxial presses. It can be used for multi-stress field physical simulation tests of uniaxial loading, biaxial loading, and triaxial loading in tunnel engineering projects with complex geostress fields.

[0057] In the description of the present invention, it is to be understood that the terms “center”, “longitudinal”, “lateral”, “length”, “width”, “thickness”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside”, “outside”, “clockwise”, “counterclockwise”, “axial”, “radial”, “circumferential”, etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation to the invention.

[0058] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0059] Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Mentioning "embodiment" in this article means that the specific features, structures or characteristics described in conjunction with the embodiment may be included in at least one embodiment of the present embodiment application. The appearance of this phrase in various positions in the specification is not necessarily the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It can be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0060] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

[0061] Those skilled in the art will readily appreciate other embodiments of the present application after considering the specification and practicing the disclosure disclosed herein. The present application is intended to cover any modification, use or adaptation of the present application, which follows the general principles of the present application and includes common knowledge or customary techniques in the art that are not disclosed in the present application. The specification and examples are intended to be exemplary only, and the true scope and spirit of the present application are indicated by the following claims.

Claims

1. A loading device for a tunnel model test in a complex geostress field, characterized in that: include: A support plate (3), a physical model of the tunnel to be tested being placed on the surface of the support plate (3); A loading component (1), wherein the loading component (1) has a plurality of small units with different elastic moduli built therein, and the loading component (1) is used to apply loads of different stress values ​​to different locations on the surface corresponding to the physical model of the tunnel to be tested; wherein: The loading assembly (1) comprises a loading frame (12), a compression column (13) and a unit pressure head (14); a plurality of mounting holes are formed through 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 physical model of the tunnel to be tested is connected to the unit pressure head (14); each of the compression columns (13) is composed of micro-unit bodies with elastic moduli of different magnifications; the micro-unit bodies with elastic moduli of different magnifications are obtained according to a tunnel engineering prototype and based on similarity theory to obtain a three-dimensional stress field of the physical model; and the three-dimensional stress field of the physical model is determined by unit division and normalization calculation.

2. A loading device for complex geostress field tunnel model test according to claim 1, characterized in that: The loading frame (12) comprises: An outer frame (121), wherein the outer frame (121) surrounds and forms an inner area; An upper frame (122) and a lower frame (123), wherein the upper frame (122) and the lower frame (123) are stacked in the internal area, each of the mounting holes sequentially penetrates the upper frame (122) and the lower frame (123), and the distances between adjacent mounting holes are equal, and a plurality of the mounting holes are arranged in an array.

3. A loading device for complex geostress field tunnel model test according to claim 2, characterized in that: The unit pressure head (14) is arranged on the bottom end surface of the lower frame (123), the lower frame (123) is magnetically connected to the unit pressure head (14), and one end of the unit pressure head (14) extends into the mounting hole to contact the surface of the compression column (13), and the compression column (13) is slidably connected to the mounting hole.

4. A loading device for complex geostress field tunnel model test according to claim 2 or 3, characterized in that: One end of the compression column (13) away from the unit pressure head (14) is connected to a pressure plate (11), and the pressure plate (11) evenly transfers the concentrated load of the pressure head of the loading device to one end of the compression column (13).

5. A loading device for complex geostress field tunnel model test according to claim 4, characterized in that: 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 geostress field is: Where: The load imposed by the outside world, is the surface area of ​​the pressure plate, is the elastic modulus of the unit column, is the compression strain of the compression column, is the element stress value loaded on the model.

6. The complex geostress field tunnel model test loading device according to claim 1 is characterized in that: Each of the compression columns (13) is composed of micro-units of elastic modulus with different magnifications, wherein the micro-units of elastic modulus with different magnifications are used to obtain a three-dimensional stress field of a physical model based on a tunnel engineering prototype and similarity theory, and the three-dimensional stress field of the physical model is divided into units and normalized and calculated, including: The three-dimensional stress field of the physical model can be calculated according to the tunnel engineering prototype and the relevant mechanical parameters of the physical model according to the similarity theory: In the elastic range, similarity relations are satisfied: ; ; ; In the plastic range, similarity relations are satisfied: ; ; Where: 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 the internal friction angle is , the similarity ratio of softening modulus is .

7. The complex geostress field tunnel model test loading device according to claim 4 is characterized in that: Each of the compression columns (13) is composed of micro-units of elastic modulus with different magnifications, wherein the micro-units of elastic modulus with different magnifications are determined by obtaining a three-dimensional stress field of a physical model based on a tunnel engineering prototype and similarity theory, and performing unit division and normalization calculation on the three-dimensional stress field of the physical model, and further comprising: According to the boundary conditions of the physical model, the three-dimensional stress field of the physical model is divided into stresses in four or six directions, the stress in each direction is divided into a finite number of units, and the stress value of each unit is calculated respectively, wherein the stress value expression is: According to the stress value of each unit, the stress proportionality coefficient between the stress value of each unit and the maximum stress unit is obtained based on normalization calculation, wherein the stress proportionality coefficient expression is: In the formula, is the stress value for each element, For relative proportions.

8. The complex geostress field tunnel model test loading device according to claim 5 is characterized in that: According to the stress proportionality coefficient And prefabricated micro-units with different elastic modulus ratios ,in, = to determine the micro-units assembled into the compressed column (13).

9. A method for testing a loading device for a complex geostress field tunnel model test according to any one of claims 1 to 8, the method comprising: Step S1: obtaining a true three-dimensional geostress field of a tunnel engineering prototype based on an in-situ geostress test or a geostress inversion method; Step S2: Simplify the tunnel engineering prototype into an experimental physical model according to similarity theory, and convert the real three-dimensional ground stress field into a three-dimensional stress field of the physical model based on the similarity ratio. The three-dimensional stress field of the physical model is divided into stresses in six directions, or simplified into a plane problem, considering the non-uniform stress fields in four directions. Step S3: obtaining a stress surface diagram according to the stress in each direction, dividing the stress surface diagram into a finite number of units, calculating the corresponding stress value of each unit by volume integral, and calculating the relative ratio of the stress value of each unit to the maximum stress unit by normalization; Step S4: According to the relative proportion of the stress values ​​of each unit, a compression column with a corresponding elastic coefficient is selected, and the selected compression column is placed 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-units with different elastic moduli, and the elastic modulus magnifications of the micro-units are different. According to the complex stress averaging diagram, the micro-units with different magnifications of elastic moduli are combined into the compression column to realize the construction of a complex geostress field; Step S5: Assemble the loading device, place it on the loading surface of the tunnel physical model, and load it through a servo rigid press. Rigid loading evenly loads stress to each compression column through the load plate, and realizes loading of complex stress fields through different compression columns.

10. The method for testing a loading device for a tunnel model test of a complex geostress field according to claim 9, wherein in step S4, if the corresponding unit stress value is the maximum , then the corresponding compression column is composed of the micro-unit with the maximum elastic modulus, and the other compression column units are based on the stress proportionality coefficient Select the elastic modulus microunit composition of the corresponding ratio.

Images