Method for determining similar material of composite support bearing structure for tunnel model test

Abstract

The present application belongs to the field of geotechnical similar material of geotechnical engineering geomechanics model test, and relates to a method for determining composite support bearing structure similar material for tunnel model test, comprising the following steps: 1) determining target parameters of support bearing structure similar material; 2) preliminarily screening support similar material to obtain tentative support similar material; 3) performing uniaxial compression test and pull-out test on the tentative support similar material obtained in step 2) to obtain uniaxial compression test results and pull-out test results, and comparing the uniaxial compression test results and the pull-out test results with the target parameters in step 1) respectively, screening a scheme similar to the target parameters as the determined support similar material. The present application provides a method for determining composite support bearing structure similar material for tunnel model test, which has high mechanical strength, convenient mechanical parameter adjustment, strong brittleness and stable mechanical performance.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of geotechnical similar materials for geotechnical engineering and geomechanics model test, and relates to a method for determining similar materials of supporting load-bearing structure, in particular to a method for determining similar materials of composite supporting load-bearing structure for tunnel model test. BACKGROUND

[0002] In tunnel engineering, the existing composite support is usually composed of primary support (hereinafter referred to as primary lining) and secondary support (hereinafter referred to as secondary lining). The primary support is usually shotcrete support, and anchor rods are added to reinforce the surrounding rock as necessary, becoming anchor-shotcrete support. When passing through fault fracture zones with extremely poor rock conditions, advanced anchor rods and grouting technology are often used to pre-reinforce the stratum. For large cross-section caverns, large buried depth, and poor tunneling conditions, prestressed anchor cables are often used to improve the deformation and stress state of the surrounding rock. The secondary lining is usually a monolithic cast-in-place concrete lining or a shotcrete lining, and steel reinforcement is added to the cross section as necessary. The thickness and reinforcement of the secondary lining mainly depend on the shape of the hole, the size of the clearance, the geological conditions of the surrounding rock, and the timing of construction.

[0003] The primary lining is mainly selected by engineering analogy method, and is calculated according to the stratum-structure method as necessary. The supporting parameters do not have a clear safety factor value, and the designer often has no choice, with a lot of randomness in the design and a lack of scientific nature. For the secondary lining, it can be used as a safety reserve under I, II, and III grade surrounding rock, and it can be used as a load-bearing structure together with the primary lining to bear the surrounding rock pressure and external load under IV, V, and VI grade surrounding rock. However, the proportion of the surrounding rock pressure shared by the secondary lining is not clear in the current academic circles, and the value of the "safety reserve" when the secondary lining is used as a "safety reserve" cannot be determined. Therefore, the tunnel composite support structure has limitations in parameter selection and load bearing, and many studies use tunnel model test to modify and improve the design method of the support structure.

[0004] Tunnel model test can directly reflect the overall mechanical properties, failure rules and characteristics of the structure. Under different working conditions, a physical model similar to the original lining is prepared according to certain similarity ratios based on the similarity theory, and the mechanical parameters such as internal force, bending moment, and hole displacement are obtained under different loading conditions by combining with working condition analysis. In order to make the physical and mechanical properties of the test model similar to those of the original structure, similar materials that meet certain similarity conditions should be used to make the model in the model test, and the selection and proportioning of similar materials are the core part of the model test. The material, geometric shape and boundary conditions of the model test must satisfy certain similarity relationship with the original engineering prototype, providing safe and effective guidance scheme for construction and engineering quality and technical support for later tunnel operation.

[0005] In the research on the similar material proportioning of the existing tunnel model test, the models used are mostly small-scale, and there are few large-scale model tests, and the physical and mechanical indexes of the models are low, which cannot meet the similar condition requirements of large-scale tunnel model tests. In order to more clearly observe the stress conditions and failure characteristics of the composite support structure such as sprayed concrete and anchor rod in the model test, it is necessary to research the large-scale tunnel similar material. SUMMARY

[0006] In order to solve the above technical problems in the background art, the application provides a method for determining a composite support load-bearing structure similar material for tunnel model test, which has high mechanical strength, convenient mechanical parameter adjustment, strong brittleness and stable mechanical properties.

[0007] In order to achieve the above purpose, the application adopts the following technical scheme:

[0008] A method for determining a composite support load-bearing structure similar material for tunnel model test, characterized in that the method comprises the following steps:

[0009] 1) determining target parameters of the support load-bearing structure similar material;

[0010] 2) preliminarily screening the support similar material to obtain a tentative support similar material;

[0011] 3) performing uniaxial compression test and pull-out test on the tentative support similar material obtained in step 2), obtaining uniaxial compression test results and pull-out test results, and comparing the uniaxial compression test results and the pull-out test results with the target parameters in step 1) respectively, screening a scheme similar to the target parameters as the determined support similar material.

[0012] Preferably, the target parameters in step 1) include target parameters of an initial lining similar material, target parameters of a secondary lining similar material, target parameters of an anchor rod similar material and target parameters of a bonding agent similar material; the target parameters of the initial lining similar material are the product of the property parameters of C35 concrete and the geometric similarity ratio; and the target parameters of the secondary lining similar material are the product of the property parameters of C30 concrete and the geometric similarity ratio.

[0013] Preferably, the geometric similarity ratio is 12.5; the property parameters of the C35 concrete include the elastic modulus of C35 concrete and the compressive strength of C35 concrete; and the property parameters of the C30 concrete include the elastic modulus of C30 concrete and the compressive strength of C30 concrete.

[0014] As preferred, the support similar material prepared in step 2) of the present application comprises a concrete similar material, an anchor rod similar material and a binder similar material.

[0015] As preferred, the specific implementation of step 3) of the present application is:

[0016] The uniaxial compression test is performed on the concrete similar material, and the uniaxial compression test result is compared with the target parameters of the primary lining similar material and the target parameters of the secondary lining similar material obtained in step 1), respectively. The concrete similar material similar to the target parameters of the primary lining similar material is selected as the determined concrete similar material for the primary lining; and the concrete similar material similar to the target parameters of the secondary lining similar material is selected as the determined concrete similar material for the secondary lining.

[0017] The pull-out test is performed on the anchor rod similar material, and the pull-out test result is compared with the target parameters of the anchor rod similar material obtained in step 1). The anchor rod similar material similar to the target parameters is selected as the determined anchor rod similar material.

[0018] The pull-out test is performed on the binder similar material, and the pull-out test result is compared with the target parameters of the binder similar material obtained in step 1). The binder similar material similar to the target parameters is selected as the determined binder similar material.

[0019] The determined concrete similar material for the primary lining, the determined concrete similar material for the secondary lining, the determined anchor rod similar material and the determined binder similar material constitute the determined support similar material of step 3).

[0020] As preferred, the specific implementation of the uniaxial compression test of the present application is:

[0021] a1) determining the composition of the concrete similar material; the concrete similar material comprises aggregate, binder, adjusting agent and additive;

[0022] a2) designing orthogonal experiment to determine the proportioning of the sample for uniaxial compression test;

[0023] a3) according to the result of the orthogonal experiment, accurately weighing the composition of the concrete similar material, mixing and stirring uniformly, filling into standard mold for layer compaction to form different test samples; and simultaneously measuring the height, diameter and mass of the test sample;

[0024] a4) using RMT pressure testing machine to perform uniaxial compression test on different test samples, with loading speed of 0.1mm / min, and stopping loading when the test sample appears large fracture or displacement-stress curve suddenly decreases;

[0025] a5) exporting the change of compressive stress and displacement by the test instrument software, drawing the stress-strain curve, obtaining the uniaxial compressive strength and elastic modulus of the test sample, comparing the uniaxial compressive strength and elastic modulus of the test sample with the target parameters of the primary lining similar material, and selecting the material similar to the target parameters of the primary lining similar material as the determined primary lining concrete similar material; comparing the uniaxial compressive strength and elastic modulus of the test sample with the target parameters of the secondary lining similar material, and selecting the material similar to the target parameters of the secondary lining similar material as the determined secondary lining concrete similar material.

[0026] As preferred, the aggregate used in the application is barite and quartz sand; the binder is gypsum and cement; the adjusting agent is water; the additive is glass fiber; the barite is fine aggregate; and the quartz sand is coarse aggregate.

[0027] As preferred, the specific implementation mode of the pull-out test on the anchor rod similar material used in the application is as follows:

[0028] b1) selecting the anchor rod similar material;

[0029] b2) testing the anchor rod similar material selected in step b1) by using the universal testing machine, monitoring the stress-strain relationship curve of the anchor rod similar material by software, placing the test sample in the testing machine clamp, starting to stretch, and until all the anchor rod similar material stretching is completed;

[0030] b3) processing the stretching test data of step b2), selecting the slope of the straight line segment on the curve according to the stress-strain relationship curve, which is the elastic modulus of the anchor rod similar material, multiplying the elastic modulus of the anchor rod similar material by the cross-sectional area of the anchor rod similar material to obtain the tensile stiffness of the anchor rod similar material, and comparing the tensile stiffness of the anchor rod similar material with the target parameters of the anchor rod similar material, and selecting the material with an error within 8% as the determined anchor rod similar material.

[0031] As preferred, the specific implementation mode of the pull-out test on the binder similar material used in the application is as follows:

[0032] c1) after step b3) is completed, preparing and tamping the surrounding rock similar material;

[0033] c2) drilling holes on the surface of the surrounding rock similar material and cleaning the materials around the holes;

[0034] c3) placing the determined anchor rod similar material selected in step b3) in the hole of step c2), and injecting the binder similar material between the determined anchor rod similar material and the hole;

[0035] c4) standing still and waiting for the binder to solidify, and then performing the pull-out test on the determined anchor rod similar material;

[0036] c5) the binder similar material is finally determined according to the result of the pull test.

[0037] A composite support load-bearing structure similar material determined by the method for determining a composite support load-bearing structure similar material for a tunnel model test as described above.

[0038] Compared with the prior art, the present application has the following advantages:

[0039] The application discloses a method for determining a composite support load-bearing structure similar material, adopts a geometric similarity ratio of 12.5, is large in scale, and prepares the composite support load-bearing structure similar material capable of meeting large-scale model tests, the similar material formula adopted can be used for manufacturing the composite support load-bearing structure which is high in mechanical strength, convenient in mechanical parameter adjustment, strong in brittleness, and stable in mechanical performance. The similar material in the application is low in raw material type, is widely sourced, and is harmless to the environment. The method for determining the lining similar material and the anchor rod similar material is simple, is suitable for pouring of a large-scale tunnel lining model, is stable in working performance, and can be widely applied to the large-scale tunnel composite support structure similar material. The prepared material of the application is simple, is good in economy, is wide in material proportioning range, can obtain the similar material meeting various similarity ratios, and is high in deformation similarity of model tests. Specifically, the application has the following advantages:

[0040] 1) the existing tunnel model test is mostly small-scale test, and the stress and failure mode of various support components such as a lining and an anchor rod are difficult to monitor, the purpose of the application is to analyze the stress characteristics of the support structure of the tunnel, and is inclined to structural test, so that a large scale is adopted to facilitate monitoring of the support structure; 2) the main component of the glass fiber is silicon oxide, is high in deformation resistance, and has the ability to resist deformation under long-term load, a small amount of glass fiber can be added when the lining similar material is prepared to improve the compressive strength of the lining similar material; 3) the epoxy resin AB glue used in the adhesion test has a curing effect, is fast in curing speed, is high in bonding strength and good in hardness after curing, and has certain toughness; 4) the material used in the application is low in price, is convenient to obtain, and is easy to popularize. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a stress-strain change curve of a uniaxial compression test of a lining similar material sample Ee-2.

[0042] Figure 2 is a stress-strain change curve of a uniaxial compression test of a lining similar material sample Cc-1.

[0043] Figure 3 is a stress-strain curve of a zinc rod (5mm) tensile test. DETAILED DESCRIPTION

[0044] The application provides a method for determining a composite support bearing structure similar material for a tunnel model test, and the method comprises the following steps:

[0045] 1) determining target parameters of the support bearing structure similar material, wherein the target parameters comprise target parameters of the primary lining similar material and target parameters of the secondary lining similar material; the target parameters of the primary lining similar material are the product of the property parameters of C35 concrete and a geometric similarity ratio; the target parameters of the secondary lining similar material are the product of the property parameters of C30 concrete and the geometric similarity ratio; the geometric similarity ratio adopted by the application is 12.5; the property parameters of C35 concrete comprise the elastic modulus of C35 concrete and the compressive strength of C35 concrete; the property parameters of C30 concrete comprise the elastic modulus of C30 concrete and the compressive strength of C30 concrete.

[0046] 2) preliminarily screening the support similar material to obtain a tentative support similar material, and the tentative support similar material comprises a concrete similar material, an anchor rod similar material and a bonding agent similar material.

[0047] 3) performing uniaxial compression tests and pull-out tests on the tentative support similar material obtained in step 2) to obtain uniaxial compression test results and pull-out test results, and comparing the uniaxial compression test results and the pull-out test results with the target parameters in step 1) respectively, screening a scheme similar to the target parameters as the determined support similar material, specifically:

[0048] when performing uniaxial compression tests on the concrete similar material, comparing the uniaxial compression test results with the target parameters of the primary lining similar material and the target parameters of the secondary lining similar material obtained in step 1) respectively, selecting a concrete similar material similar to the target parameters of the primary lining similar material as the determined concrete similar material for the primary lining; and selecting a concrete similar material similar to the target parameters of the secondary lining similar material as the determined concrete similar material for the secondary lining;

[0049] when performing pull-out tests on the anchor rod similar material, comparing the pull-out test results with the target parameters obtained in step 1), and selecting an anchor rod similar material similar to the target parameters as the determined anchor rod similar material, specifically:

[0050] a1) determining the composition of the concrete similar material; the concrete similar material comprises aggregate, bonding agent, adjusting agent and additive;

[0051] a2) designing an orthogonal experiment to determine the proportioning of the sample for the uniaxial compression test; the aggregate is barite and quartz sand; the bonding agent is gypsum and cement; the adjusting agent is water; the additive is glass fiber; the barite is fine aggregate; and the quartz sand is coarse aggregate.

[0052] a3) According to the results of the orthogonal experiment, accurately weigh the composition of the concrete similar material, mix and stir uniformly, and load into a standard mold to form different test samples by layer compaction; meanwhile, measure the height, diameter and mass of the test sample;

[0053] a4) Using the RMT pressure testing machine, respectively, uniaxial compression test is performed on different test samples, the loading speed is 0.1mm / min, and the loading is stopped when the test sample appears large fracture or the displacement-stress curve suddenly decreases;

[0054] a5) The change of compressive stress and displacement is exported through the test instrument software, the stress-strain curve is drawn, the uniaxial compressive strength and elastic modulus of the test sample are obtained, and the uniaxial compressive strength and elastic modulus of the test sample are compared with the target parameters of the primary lining similar material, and the primary lining similar material with similar target parameters of the primary lining similar material is selected as the determined primary lining concrete similar material; the uniaxial compressive strength and elastic modulus of the test sample are compared with the target parameters of the secondary lining similar material, and the secondary lining similar material with similar target parameters of the secondary lining similar material is selected as the determined secondary lining concrete similar material.

[0055] When the binder similar material is subjected to a pull-out test, the pull-out test results are compared with the target parameters obtained in step 1), and the binder similar material with similar target parameters is selected as the determined binder similar material, and the specific way is:

[0056] b1) Select the anchor rod similar material;

[0057] b2) The universal testing machine is used to test the anchor rod similar material selected in step b1), and the stress-strain relationship curve of the anchor rod similar material is monitored through the software, the test machine clamp is placed, the stretching is started, and all the anchor rod similar material stretching is completed;

[0058] b3) The stretching test data of step b2) is processed, the slope of the straight line segment on the curve is selected according to the stress-strain relationship curve, which is the elastic modulus of the anchor rod similar material, the elastic modulus of the anchor rod similar material is multiplied by the cross-sectional area of the anchor rod similar material to obtain the tensile stiffness of the anchor rod similar material, and the tensile stiffness of the anchor rod similar material is compared with the target parameters of the anchor rod similar material (such as Table 3, the target parameters include elastic modulus, tensile stiffness and tensile strength), and the material with an error within 8% is selected as the determined anchor rod similar material.

[0059] The determined primary lining concrete similar material, the determined secondary lining concrete similar material, the determined anchor rod similar material and the determined binder similar material constitute the determined support similar material of step 3), and the specific operation way is:

[0060] c1) after step b3) is completed, the surrounding rock similar material is prepared and tamped;

[0061] c2) drilling holes on the surface of the surrounding rock similar material, cleaning the material around the holes;

[0062] c3) placing the determined anchor rod similar material selected in step b3) in the hole in step c2), and injecting the binder similar material between the determined anchor rod similar material and the hole;

[0063] c4) standing still and waiting for the binder to solidify, and testing the determined anchor rod similar material by pulling test;

[0064] c5) finally obtaining the determined binder similar material according to the pulling test results.

[0065] The present application provides a method for determining a composite support load-bearing structure similar material for tunnel model test, and also provides management of the composite support load-bearing structure similar material for tunnel model test determined based on the method.

[0066] The present application is a preferred embodiment of the present application, and is further described by means of the drawings and examples in order to better achieve the purposes and technical solutions of the present application.

[0067] In order to more accurately and conveniently determine the composite support load-bearing structure similar material for tunnel model test, the present application carries out two tests, i.e. uniaxial compression test and tensile test, wherein the uniaxial compression test can obtain the target parameters of the similar material according to the geometric similarity ratio and the properties of C30 and C35 concrete. The target parameters are as follows: the elastic modulus and compressive strength of C35 are used as the target parameters of the primary lining similar material, and the elastic modulus and compressive strength of C30 are used as the target parameters of the secondary lining similar material. The target parameters of the lining similar material are shown in Tables 1 and 2.

[0068] Before determining the test scheme, the uniaxial compression test is carried out to study the influence of the proportions of gypsum and water, the proportions of cement and gypsum, the proportion of aggregate, and the content of additives on the uniaxial compressive strength of the similar material, and then the implementation of the preferred test scheme is as follows: under the premise that the total mass of the aggregate, the binder and the adjusting agent remains unchanged, the proportions of the similar material that best match the test required parameters are analyzed by adjusting the proportions of gypsum and cement in the binder. The specific test steps are as follows:

[0069] Step one, design test: under the premise of the total mass of aggregate, binder and regulator unchanged, adjust the proportion of gypsum and cement in the binder, and conduct orthogonal test. The total mass of aggregate is 675g, of which 540g is barite and 135g is quartz sand. The total mass of binder is 740g. The mass of regulator is 650g. The mass of additive is 5g. By adjusting the mass ratio of gypsum to cement (gypsum: cement), five test schemes are designed, i.e. 1:1, 2:1, 1:2, 1:2.5 and 1:3. Each scheme is divided into two groups according to whether glass fiber is added, i.e. the first scheme is gypsum: cement = 1:1, and two control groups are designed, i.e. Aa-1 (without adding glass fiber) and Aa-2 (with adding glass fiber). Similarly, there are Aa-1, Aa-2, Bb-1, Bb-2, Cc-1, Cc-2, Dd-1, Dd-2, Ee-1 and Ee-2 in total ten groups of test. Each group of test is loaded for three times (three samples). The similar material formula of each group is shown in Table 4.

[0070] Step two, prepare similar material: the similar material is weighed by an electronic scale, mixed and stirred uniformly, and then layered and compacted in a standard mold with a diameter of 50mm and a height of 100mm. A layer of vaseline is filled in the mold to facilitate the demolding of the sample. After demolding, the sample is placed in a ventilated place or dried by a drying machine. The height, diameter and mass of the sample are measured by a vernier caliper and an electronic scale.

[0071] Step three, loading test: uniaxial compression test is carried out by using RMT pressure testing machine, and the loading speed is 0.1mm / min. The loading is stopped when the sample appears large fracture or the displacement-stress curve decreases suddenly. After all the samples are loaded, the next group of formula test is carried out.

[0072] Step four, data analysis: after all test schemes are completed, the change of compressive stress and displacement is exported by test instrument software, the stress-strain curve is drawn, and the similar material formula scheme similar to the target parameters is selected as the similar material formula scheme according to the uniaxial compressive strength and elastic modulus of the similar material.

[0073] Referring to Figure 1 For the formula Ee-2, the elastic modulus of the similar material is 2.49MPa, and the compressive strength is 2.53MPa. The target parameters of the initial lining similar material are elastic modulus 2.60MPa and compressive strength 2.08MPa. The physical and mechanical parameters are similar, so the formula Ee-2 is used as the similar material formula scheme of the initial lining.

[0074] Referring to Figure 2For the ratio of scheme Cc-1, the similar material elastic modulus is 2.23 MPa, the compressive strength is 1.76 MPa, the target parameters of the similar material of the secondary lining are elastic modulus 2.52 MPa and compressive strength 1.80 MPa, the physical and mechanical parameters of the two are similar, so the scheme Cc-1 is adopted as the similar material ratio scheme of the secondary lining.

[0075] In the process of selecting the anchor rod similar material, considering that the mechanical parameters and geometric parameters of the anchor rod are numerous, but most of the time cannot guarantee that all the target parameters are completely similar, after consulting the data, the anchor rod similar material related properties should refer to the tensile stiffness, tensile strength, elastic modulus and other mechanical parameters, so in the present application, the tensile stiffness is specified as the main parameter, the stress-strain relationship curve of the anchor rod similar material is monitored through the test instrument, the elastic modulus of the anchor rod similar material is obtained, and then the tensile stiffness is obtained, and the mechanical and geometric target parameters of the anchor rod similar material are shown in Table 3. Some materials roughly meeting the similar proportion are preliminarily screened out through the tensile test, such as common copper, iron and aluminum metal materials and PVC pipe, ABS pipe and other organic synthetic materials, and the screened materials are further subjected to the tensile test.

[0076] The tensile test test scheme is to select the anchor rod similar material, after completing the tensile test, the anchor rod similar material most matched with the test target parameters is analyzed, and is placed in the prepared surrounding rock similar material material box for the tensile test, so as to judge the bonding performance of the bonding material. The structure of the anchor rod is made into a threaded metal rod, a matching nut and a tray.

[0077] The specific implementation steps of the tensile test are as follows:

[0078] Step one, design test: select anchor rod similar material, and perform contrast test according to the material diameter size and whether it is hollow. The present application adopts a plurality of materials for test, as a preferred embodiment, the anchor rod similar material includes aluminum, zinc, iron metal material and PVC, ABS organic synthetic material. The test specifies that the length of the anchor rod is 360 mm, for metal samples, solid materials (rods) with diameters of 3 mm, 4 mm and 5 mm, and hollow materials (pipes) with outer diameters of 5 mm and wall thicknesses of 1 mm are used; for PVC and ABS materials, only hollow materials (pipes) with outer diameters of 5 mm and wall thicknesses of 1 mm are used. Each group of test is subjected to three tensile tests (three samples), and there are a total of 14 groups of test. For the bonding test, the present application adopts the anchor rod glue and the epoxy resin AB glue, the anchoring effect of the two bonding agents is judged through the tensile test.

[0079] Step two, pull-out test: the test is performed by using a universal testing machine, the stress-strain relationship curve of the anchor rod similar material is monitored by software, the test is placed in the test machine chuck, whether each part of the test instrument is normal is checked, and the tensile test is started, after all the samples are tensiled, the next group of formula test is performed.

[0080] Step three, data analysis: process the tensile test data, according to the stress-strain relationship curve, select the slope of the straight line segment on the curve, which is the elastic modulus of the anchor rod similar material, and multiply it by the cross-sectional area of the sample to obtain the tensile stiffness, and compare it with the target parameter, select the material closest to the error within about 8% as the anchor rod similar material.

[0081] Step four, bonding test: after selection, indoor pull-out test is carried out on the anchor rod material sample, similar material of surrounding rock is prepared and rammed, after filling, drill holes on the surface of the surrounding rock similar material, clean the material around the hole, place the anchor rod material and inject the bonding agent, respectively, stand for 12, 24 and 30 hours, until the bonding agent solidifies to reach the strength, and then carry out the pull-out test. According to the pull-out test results, the appropriate anchor rod similar material and bonding agent can be finally obtained.

[0082] Reference Figure 3 For zinc bar (solid) with a diameter of 5mm, the tensile stiffness is 47825N, the tensile strength is 60MPa, the target parameter of the anchor rod similar material is the tensile stiffness 40857N, and the tensile strength is 24MPa, both of which meet the similarity condition. Therefore, the zinc bar with a diameter of 5mm is used as the anchor rod similar material.

[0083] Through the bonding test, the overall effect of the anchoring glue is weaker than that of the epoxy resin glue, and the epoxy resin glue has reached the strength within 24 hours, but it can also achieve the anchoring effect after placing for 12 hours. Therefore, the epoxy resin AB glue is used as the bonding agent of the anchor rod similar material.

[0084] Table 1 Comparison of physical and mechanical properties of similar materials in group Ee-2 with target parameters of primary lining

[0085]

[0086]

[0087] Table 2 Comparison of physical and mechanical properties of similar materials in group Cc-1 with target parameters of secondary lining

[0088]

[0089] Table 3 Comparison of physical and mechanical properties of zinc bar (5mm) with target parameters

[0090]

[0091] Table 4 Formulation table of lining similar material

[0092]

[0093] In conclusion, the similar material in the application has less kinds of raw materials, wide sources and no harm to the environment. The determination method of the lining similar material and the anchor rod similar material is simple, and is suitable for pouring of large-scale tunnel lining model, and has stable working performance, and can be widely applied to large-scale tunnel composite support structure similar material. The configuration material of the application is simple, economical and has wide material proportioning range, and can obtain similar material meeting various similar ratios, and has high deformation similarity for model test.

[0094] In addition, the preparation and analysis of the material of the application, the screened similar material has good physical and mechanical properties, and overcomes the defects of unsuitable for large-scale lining model segmented pouring and poor anchoring property of the anchor rod adhesive.

[0095] The similar material prepared by the method of the application has large variation range of mechanical strength parameters, and the application is mainly designed for composite support bearing structure similar material in the field of tunnel engineering. The above examples are only used to help understand the method and core idea of the application. Meanwhile, for the general technical personnel in the field, the specific implementation and application range will be changed according to the idea of the application. In conclusion, the content of the specification should not be understood as the limitation of the application.

Claims

1. A method for determining a composite support load-bearing structure similar material for a tunnel model test, characterized by, The method comprises the following steps: 1) determining target parameters of supporting bearing structure similar materials, the target parameters comprising target parameters of primary lining similar materials, target parameters of secondary lining similar materials, target parameters of anchor rod similar materials and target parameters of adhesive similar materials; the target parameters of the primary lining similar materials are the product of the property parameters of C35 concrete and the geometric similarity ratio; the target parameters of the secondary lining similar materials are the product of the property parameters of C30 concrete and the geometric similarity ratio; the structure of the anchor rod is a threaded metal rod, a matched nut and a tray, the anchor rod similar materials comprising aluminum, zinc, iron, PVC or ABS; the adhesive similar materials comprising anchoring glue or epoxy resin AB glue; 2) preliminarily screening the supporting similar materials to obtain tentative supporting similar materials; the tentative supporting similar materials comprising concrete similar materials, anchor rod similar materials and adhesive similar materials; 3) performing uniaxial compression test and pull-out test on the tentative supporting similar materials screened in step 2) to obtain uniaxial compression test results and pull-out test results, comparing the uniaxial compression test results and the pull-out test results with the target parameters in step 1) respectively, screening the schemes similar to the target parameters as the determined supporting similar materials; the specific implementation manner is: performing uniaxial compression test on the concrete similar materials, comparing the uniaxial compression test results with the target parameters of the primary lining similar materials and the target parameters of the secondary lining similar materials obtained in step 1) respectively, selecting the concrete similar materials similar to the target parameters of the primary lining similar materials as the determined concrete similar materials for the primary lining, and selecting the concrete similar materials similar to the target parameters of the secondary lining similar materials as the determined concrete similar materials for the secondary lining; the specific implementation manner of the uniaxial compression test is: a1) determining the composition of the concrete similar materials; the concrete similar materials comprising barite and quartz sand, gypsum and cement, water and glass fiber; a2) designing orthogonal experiment to determine the proportioning of the test samples for uniaxial compression test; a3) accurately weighing the composition of the concrete similar materials according to the results of the orthogonal experiment, mixing and stirring uniformly, layering and compacting in a standard mold to form different test samples; meanwhile, measuring the height, diameter and mass of the test samples; a4) using an RMT pressure testing machine to perform uniaxial compression test on different test samples respectively, the loading speed being 0.1 mm / min, and stopping loading when a large fracture occurs in the test sample or the displacement-stress curve suddenly decreases downward; a5) exporting the change of compressive stress and displacement through the test instrument software, drawing a stress-strain curve, obtaining the uniaxial compressive strength and elastic modulus of the test sample, comparing the uniaxial compressive strength and elastic modulus of the test sample with the target parameters of the primary lining similar materials, and selecting the concrete similar materials similar to the target parameters of the primary lining similar materials as the determined concrete similar materials for the primary lining; comparing the uniaxial compressive strength and elastic modulus of the test sample with the target parameters of the secondary lining similar materials, and selecting the concrete similar materials similar to the target parameters of the secondary lining similar materials as the determined concrete similar materials for the secondary lining. The pulling test is performed on the anchor rod similar material, the pulling test result is compared with the target parameter of the anchor rod similar material obtained in step 1), and the anchor rod similar material similar to the target parameter is selected as the determined anchor rod similar material; and the specific implementation mode of the pulling test on the anchor rod similar material is: b1) selecting the anchor rod similar material; b2) performing the test on the anchor rod similar material selected in step b1) by using the universal testing machine, monitoring the stress-strain relationship curve of the anchor rod similar material by software, placing the test in the testing machine clamp, starting to stretch, and completing all the anchor rod similar material stretching; b3) processing the stretching test data of step b2), selecting the slope of the straight line segment on the curve according to the stress-strain relationship curve, obtaining the elastic modulus of the anchor rod similar material, multiplying the elastic modulus of the anchor rod similar material by the cross-sectional area of the anchor rod similar material to obtain the tensile stiffness of the anchor rod similar material, comparing the tensile stiffness of the anchor rod similar material with the target parameter of the anchor rod similar material, and selecting the material with an error within 8% as the determined anchor rod similar material; The pulling test is performed on the anchor rod similar material, the pulling test result is compared with the target parameter of the anchor rod similar material obtained in step 1), and the anchor rod similar material similar to the target parameter is selected as the determined anchor rod similar material; and the specific implementation mode of the pulling test on the anchor rod similar material is: c1) after step b3) is completed, the surrounding rock similar material is prepared and tamped; c2) drilling a hole on the surface of the surrounding rock similar material and cleaning the material around the hole; c3) placing the determined anchor rod similar material selected in step b3) in the hole in step c2), and injecting the adhesive similar material between the determined anchor rod similar material and the hole; c4) standing still and waiting for the adhesive to solidify, and performing the pulling test on the determined anchor rod similar material; c5) finally obtaining the determined adhesive similar material according to the pulling test result; The determined primary lining concrete similar material, the determined secondary lining concrete similar material, the determined anchor rod similar material, and the determined adhesive similar material constitute the determined support similar material in step 3); The geometric similarity ratio is 12.5; the property parameters of the C35 concrete include the elastic modulus of the C35 concrete and the compressive strength of the C35 concrete; and the property parameters of the C30 concrete include the elastic modulus of the C30 concrete and the compressive strength of the C30 concrete.

2. The method of claim 1, wherein the method is characterized by: The barite is fine aggregate; and the quartz sand is coarse aggregate.

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