A model test apparatus and test method for simulating tunnel construction with different clearances

Abstract

This invention discloses a model test device and method for simulating tunnel construction with different clearances. The device includes a housing with a first tunnel opening and a second tunnel adjustment opening. Each second tunnel adjustment opening has a second tunnel translation block, and two second tunnel translation blocks have corresponding second tunnel openings. A rack is located at the bottom of each second tunnel translation block, and a translation drive mechanism is located below the rack. Sliding grooves for shafts are located on the upper and lower sides of each second tunnel adjustment opening, with two sliding shafts located within each groove. This test device and method can obtain the optimal clearance between adjacent tunnels through experimental simulation, enabling long-term research during the construction or operation phases of adjacent tunnels. This invention can also test the mutual influence between the construction of the first and second tunnels, providing a basis for the design and construction of tunnels with small clearances.

Description

Technical Field

[0001] This invention relates to the field of tunnel engineering technology, specifically to a model test device and test method for simulating tunnel construction with different clearances. Background Technology

[0002] With the rapid development of highways and railways in China, tunnel alignment often employs small clearance tunnel schemes due to route constraints. Sometimes, existing tunnels exist nearby, making the construction of small clearance tunnels unavoidable. For small clearance tunnels in complex surrounding rock conditions, the poor mechanical properties of the surrounding rock, coupled with repeated disturbances to the interbedded rock walls during construction, further complicate the mechanical behavior of the surrounding rock and support structure. Therefore, similar model tests are conducted on tunnels with different clearances to study suitable construction methods, support structure forms, and reasonable clearances, providing an experimental basis for design scheme selection.

[0003] Previous model testing devices for studying tunnels with small clearances have mainly been tunnel model testing devices with a single clearance or single tunnel model testing devices considering the bias problem to simulate the construction of tunnels with small clearances. Tunnel model testing devices with a single clearance are limited to a fixed clearance. Although they can simulate the construction of tunnels with small clearances, their model box utilization rate is low, and studying only a single clearance cannot effectively guide design or analyze the optimal clearance. Model testing devices that equate the problem of tunnels with small clearances to the bias problem can reflect the changes in mechanical behavior caused by tunnel construction under different clearances, but their realism is not as good as those with a single clearance, and they cannot reflect the disturbance law of the rock wall between two adjacent tunnels, thus also having limitations. Summary of the Invention

[0004] In order to realistically simulate the mechanical behavior of the surrounding rock mass and lining structure during the construction and operation of adjacent tunnels, and to simulate the mutual interference of various excavation methods and support methods on tunnels during the construction period of tunnels with different clearances, and to obtain the optimal clearance of adjacent tunnels through experimental simulation, this invention provides a model test device and test method for simulating the construction of tunnels with different clearances.

[0005] To achieve the above-mentioned objectives, the technical solution of the model test device for simulating tunnel construction with different clearances of the present invention is as follows: it includes a box body, with a first tunnel hole and a second tunnel adjustment hole correspondingly arranged on the front and rear sides of the box body. A second tunnel translation block is arranged on each second tunnel adjustment hole, and a second tunnel hole is correspondingly arranged on the two second tunnel translation blocks. When the second tunnel translation block slides, it completely covers the second tunnel hole. A rack part is arranged at the bottom of the second tunnel translation block, and a translation drive mechanism is arranged below the rack part. A shaft sliding groove is arranged on both the upper and lower sides of the second tunnel adjustment hole. Two sliding shafts are arranged in each shaft sliding groove, and the two ends of each sliding shaft are respectively connected to the two second tunnel translation blocks.

[0006] Furthermore, the translation drive mechanism includes a transmission gear meshing with the rack and pinion section and a hand crank gear meshing with the transmission gear. The two transmission gears are fixed to the housing through a transmission shaft, and the hand crank gear is fixed to the housing through a rotating shaft. A rocker arm is also fixedly connected to the hand crank gear.

[0007] Furthermore, it also includes a first tunnel mounting plate, a first tunnel hole is provided on the first tunnel mounting plate, and the housing is provided with a first tunnel mounting hole for mounting the first tunnel mounting plate. The first tunnel mounting hole is a rectangular hole. The first tunnel mounting plate includes a limiting plate and a fixing plate that cooperate with the first tunnel mounting hole. The limiting plate is installed in the first tunnel mounting hole. The fixing plate is also provided with bolt holes at the four corners, and mounting plate bolts are provided in the bolt holes. The housing is provided with fixing threaded holes for the mounting plate bolts. The fixing plate is fixed to the housing by the mounting plate bolts.

[0008] Furthermore, both ends of the sliding shaft are provided with threaded portions, and shaft bolts are provided on the threaded portions. The second tunnel translation block is provided with shaft through holes that cooperate with the sliding shaft. The two second tunnel translation blocks are fixed to the outside of the second tunnel adjustment hole by the sliding shaft and shaft bolts.

[0009] Furthermore, a sliding bearing is provided between the sliding shaft and the shaft sliding groove, and a bearing rolling groove that mates with the sliding bearing is provided on the outside of the shaft sliding groove.

[0010] Furthermore, the box body is provided with external reinforcing grids around its perimeter and a bottom support partition at its bottom. Both the external reinforcing grids and the bottom support partition are grating plates. The bottom support partition is provided with several lifting holes, which are strip-shaped holes. Limiting blocks are provided on the inner side of the two second tunnel translation blocks. The limiting blocks are long and strip-shaped.

[0011] The test method for a model test device simulating tunnel construction with different clearances includes the following steps:

[0012] S1: Determine the geometric similarity ratio l based on the actual tunnel length and box girder width, and set several sets of simulated net distance values ​​L1, L2, ... L between the first and second tunnels.n n is the number of simulated net distance values; the unit weight similarity ratio K of the simulated soil of the construction tunnel is obtained by measuring the rock physical and mechanical parameters of the surrounding rock of the actual construction tunnel based on the original rock indoor triaxial test.

[0013] S2: Select a set of simulated net distance values ​​to conduct a tunnel construction simulation test. Before the test, adjust the second tunnel translation block to the simulated position according to the selected simulated net distance value L, and use baffles to block the first tunnel hole and the second tunnel hole on the outside.

[0014] S3: Based on the density ratio K, select the construction tunnel simulation soil and fill the box with the construction tunnel simulation soil. The construction tunnel simulation soil is added layer by layer and compacted. During the filling process of the construction tunnel simulation soil, several miniature earth pressure cells and several displacement sensors are buried at the arch and middle rock wall positions of the first and second tunnels.

[0015] S4: Remove the baffle plate on the second tunnel opening, excavate the second tunnel, carry out initial support for the second tunnel during the excavation process, and bury earth pressure cell sensors at the contact position between the initial support and the soil, and install strain gauges on the monitoring section.

[0016] S5: After the excavation of the second tunnel is completed, remove the external baffle of the first tunnel opening, and use the method in step S4 to excavate and install the detection equipment for the first tunnel; and conduct a set of tunnel construction simulation tests simulating the net distance value.

[0017] S6: After completing a set of simulated net distance values ​​for tunnel construction simulation test, excavate the simulated tunnel soil in the box; select a set of remaining simulated net distance values, adjust the position of the second tunnel translation block, return to step S2, and conduct the next set of simulated net distance values ​​for tunnel construction simulation test.

[0018] S7: Repeat steps S2-S6 to continue the test until the tunnel construction simulation test of all groups of tunnel net distance values ​​is completed;

[0019] S8: After simulating all groups of tunnel clearance values, obtain monitoring data under different simulated clearance groups, and complete the simulation test of tunnel construction with different clearances.

[0020] Furthermore, the simulated soil for the construction tunnel is a mixture of iron ore powder, barite powder, and quartz sand.

[0021] Furthermore, the simulated soil for the construction tunnel is a mixture of iron ore powder, barite powder, quartz sand, alcohol rosin solution, and hydraulic oil.

[0022] Furthermore, the simulated steel arch frame uses copper strips, and the sprayed concrete uses a mixture of gypsum and water in a ratio of 1:1.06.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention simulates the construction process of tunnels with different clearances. The translatable function of the second tunnel block enables the simulation of tunnel construction with different clearances within the same model test device. This allows for monitoring of soil pressure and displacement, simulating different excavation methods and support structures, and verifying the feasibility of the design scheme by comparing it with the actual site design. This device reduces the errors caused by using different model boxes to study the construction of tunnels with different clearances in the past, and can be used for indoor research on the mechanics of small-clearance tunnels.

[0025] This invention utilizes a box with a first tunnel opening and a second tunnel translation block with a second tunnel opening to form a model test device simulating different clearances. The device contains simulated construction tunnel soil material, and the second tunnel translation block is responsible for sealing the model test device and realizing the horizontal movement of the second tunnel. The purpose is to simulate construction or operation scenarios of tunnels with different clearances. Earth pressure cells, displacement gauges, and strain gauges are set inside the model box to monitor the support structure and surrounding soil pressure of the first and second tunnels, and to study the stress characteristics of the interlocking rock wall under different clearances of the first and second tunnels.

[0026] This invention uses the same model box to simulate tunnels with different clearances, solving the problem that the model box can only simulate a single clearance, improving the efficiency of the model box, reducing experimental costs, and increasing the possibility of interlocking rock walls in the research.

[0027] This invention utilizes a hand-cranked gear to drive the horizontal movement of the second tunnel translation block. Four sliding shafts and one transmission shaft ensure the mechanization of the model test box, guaranteeing the alignment of the two second tunnel translation blocks and the parallel construction of the first and second tunnels. This further improves the test accuracy, making the simulation results more realistic, accurate, and reliable, and providing a more reasonable theoretical basis and technical support for actual engineering.

[0028] The first and second tunnel holes of the present invention can be replaced, thereby facilitating the replacement of tunnel holes with different cross-sections and enabling simulation tests of tunnel construction between different tunnel holes.

[0029] The experimental apparatus and method of this invention can obtain the optimal clearance between adjacent tunnels through experimental simulation, enabling long-term research during the construction or operation period of adjacent tunnels. It can also test the mutual influence between the construction of the first and second tunnels, providing a basis for the design and construction of tunnels with small clearances.

[0030] Based on the simulation test method of optimal clearance for adjacent tunnels, this invention can simulate the mutual interference of various excavation methods and support methods on tunnels under different clearances during the construction period, study the sensitivity of the excavation disturbance law of the first and second tunnels to construction parameters under different clearances, and obtain the optimal construction method and optimal clearance for adjacent tunnels.

[0031] The experimental method of this invention can also simulate the operation of adjacent tunnels with different clearances under rock creep, study the influence of the first and second tunnel clearances on the mechanical behavior of the tunnel lining structure, realistically simulate the mechanical behavior of the surrounding rock mass and lining structure during the construction and operation of adjacent tunnels, and analyze the experimental data to study the mechanical properties of the surrounding rock of tunnels with different clearances and the mechanical behavior of the structure during the operation period.

[0032] This invention can monitor the stress of the surrounding rock after the excavation of two tunnels, analyze the stress variation law of the interlocking rock wall and the surrounding rock, conduct research on the construction of tunnels with different clearances, explore a more reasonable clearance between the two tunnels and the construction technology, and provide certain theoretical support for the construction and operation safety of tunnels with small clearances in the future. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of the model test device of the present invention;

[0034] Figure 2 This is a front view of the model testing device of the present invention;

[0035] Figure 3 This is a front view of the model test device of the present invention after the second tunnel translation block has been removed;

[0036] Figure 4 This is a schematic diagram of the overall structure of the second tunnel translation block;

[0037] Figure 5 This is a schematic diagram of the sliding shaft structure;

[0038] Figure 6 This is a schematic diagram of the transmission shaft and hand-cranked gear.

[0039] Figure 7 Schematic diagram of the structure of the mounting plate for the first tunnel Figure 1 ;

[0040] Figure 8 Schematic diagram of the structure of the mounting plate for the first tunnel Figure 2 ;

[0041] The symbols for each component are as follows:

[0042] 1. Housing; 2. External reinforcing grating; 3. First tunnel hole; 4. Second tunnel hole; 5. Rack section; 6. Second tunnel translation block; 7. Drive shaft; 8. Drive gear; 9. Rocker arm; 10. Hand crank gear; 11. Sliding shaft; 12. Shaft bolt; 13. Bottom support partition; 14. Lifting hole; 15. Limiting block; 16. Sliding bearing; 17. Shaft sliding groove; 18. Bearing rolling groove; 19. First tunnel mounting plate; 20. Second tunnel adjustment hole; 21. Threaded section; 22. Connecting block; 23. Mounting plate bolt. Detailed Implementation

[0043] The specific embodiments of the present invention are described below to enable those skilled in the art to understand the present invention. However, it should be understood that the present invention is not limited to the scope of the specific embodiments. For those skilled in the art, various changes are obvious as long as they are within the spirit and scope of the present invention as defined and determined by the appended claims. All inventions utilizing the concept of the present invention are protected.

[0044] like Figure 1 , 2 As shown in Figure 3, this invention provides a model test device for simulating tunnel construction with different clearances. This system is mainly used to simulate the construction of parallel pilot tunnels and main tunnels in mountainous areas, and the construction of tunnels with small clearances in urban or mountainous areas. It is used to study the mutual influence between two tunnels under different clearances and their long-term mutual influence during operation. The model test device for simulating tunnel construction with different clearances includes a box body 1. A first tunnel hole 3 and a second tunnel adjustment hole 20 are correspondingly arranged on the front and rear sides of the box body 1. A second tunnel translation block 6 is arranged on each of the second tunnel adjustment holes 20, and a second tunnel hole 4 is correspondingly arranged on each of the two second tunnel translation blocks 6. When the second tunnel translation block 6 slides, it completely covers the second tunnel hole 4. The box body 1 and the second tunnel translation block 6 are in close contact with each other. After the second tunnel translation block 6 moves to the simulated position, the bolts at both ends of the sliding shaft 11 are used to tighten the second tunnel translation blocks 6 at the front and rear of the box body 1, ensuring a tight fit with the box body 1 and preventing soil leakage inside the box body for testing.

[0045] like Figure 4 and 5As shown, the bottom of the second tunnel translation block 6 is provided with a rack portion 5, and a translation drive mechanism is provided below the rack portion 5. The upper and lower sides of the second tunnel adjustment hole 20 are provided with shaft sliding grooves 17, and each shaft sliding groove 17 contains two sliding shafts 11. Each sliding shaft 11 is connected to two second tunnel translation blocks 6 at its two ends. Both ends of the sliding shaft 11 are provided with threaded portions 21, and shaft bolts 12 are provided on the threaded portions 21. The second tunnel translation block 6 is provided with shaft through holes that mate with the sliding shafts 11. The two second tunnel translation blocks 6 are fixed to the outside of the second tunnel adjustment hole 20 by the sliding shafts 11 and shaft bolts 12. A sliding bearing 16 is provided between the sliding shaft 11 and the shaft sliding groove, and a bearing rolling groove 18 that mates with the sliding bearing 16 is provided outside the shaft sliding groove. The second tunnel adjustment hole 20 is a rectangular hole, and the length of the bearing rolling groove 18 is the same as the length of the rectangular hole. A shaft sliding groove 17 is provided on the bearing rolling groove 18, extending through the surface of the housing to provide sliding space for the sliding shaft 7. The height of the shaft sliding groove 17 is slightly larger than the diameter of the sliding shaft 7, and the front and rear sides of the housing 1 are uniform. The length of the sliding shaft 11, excluding the thread 21, should be slightly larger than the vertical distance between the outer surfaces of the second tunnel translation block 6, and the length of the thread 21 should be greater than the thickness of the second tunnel translation block 6 to ensure that the bolt 12 can lock the two second tunnel translation blocks 6.

[0046] like Figure 6 As shown, the translation drive mechanism includes a transmission gear 8 meshing with the rack section 5 and a hand-cranked gear 10 meshing with the transmission gear 8. The two transmission gears 8 are fixed to the housing 1 through a transmission shaft 7. The hand-cranked gear 10 is fixed to the housing 1 through a rotating shaft, and a rocker arm 9 is also fixedly connected to the hand-cranked gear 10. The hand-cranked gear 10 meshes with the transmission gear 8 and is connected to the rocker arm 9 by a connecting key. The rotation of the hand-cranked gear 10 drives the transmission gears 8 on both sides to rotate.

[0047] like Figure 7 and 8 As shown, it also includes a first tunnel mounting plate 19, a first tunnel hole 3 is provided on the first tunnel mounting plate 19, and a first tunnel mounting hole for mounting the first tunnel mounting plate 19 is provided on the housing 1. The first tunnel mounting hole is a rectangular hole. The first tunnel mounting plate 19 includes a limiting plate and a fixing plate that cooperate with the first tunnel mounting hole 19. The limiting plate is installed in the first tunnel mounting hole 19. Bolt holes are also provided at the four corners of the fixing plate. Mounting plate bolts 23 are provided in the bolt holes. The housing 1 is provided with fixing threaded holes for mounting plate bolts 23. The fixing plate is fixed to the housing 1 by mounting plate bolts 23.

[0048] In this embodiment, the box body 1 is surrounded by external reinforcing grid plates 2, and the bottom of the box body 1 is provided with a bottom support partition 13. Both the external reinforcing grid plates 2 and the bottom support partition 13 are grating plates. The dimensions of the external reinforcing grid plates 2 and the platform are not fixed, with the main purpose of facilitating climbing of the model box 1 and placing the experimental device. The bottom support partition 13 is provided with several lifting holes 14, which are strip-shaped holes. The height of the bottom support partition 13 is also mainly for convenient testing. The size of the lifting holes 14 is larger than the size of the forklift rack or crane rope, and is determined according to the laboratory conditions. Limiting blocks 15 are provided on the inner side of the two second tunnel translation blocks 6. The limiting blocks 15 are long and strip-shaped. The box body 1, the external reinforcing grid plates 2, and the bottom support partition 13 are designed as a single unit.

[0049] In this embodiment, a limiting block 15 is provided inside the second tunnel translation block 6. The length of the limiting block 15 along the direction perpendicular to the second tunnel translation block 6 should be greater than the thickness of the rectangular elongated hole, and the horizontal position of the limiting block 15 should be determined according to the distance from the left side of the rectangular elongated hole to the second tunnel translation block 6, so as to ensure that the second tunnel translation block 6 always blocks the rectangular elongated hole during the translation process.

[0050] The experimental method for simulating tunnel construction with different clearances using a model testing device includes the following steps:

[0051] S1: Determine the geometric similarity ratio l based on the actual tunnel length and the width of box 1, and set several sets of simulated net distance values ​​L1, L2, ... L between the first tunnel and the second tunnel. n n is the number of simulated net distance values; the unit weight similarity ratio K of the simulated soil of the construction tunnel is obtained by measuring the rock physical and mechanical parameters of the surrounding rock of the actual construction tunnel based on the original rock indoor triaxial test; the surrounding rock physical and mechanical parameters include elastic modulus, cohesion, and internal friction angle;

[0052] The method for obtaining the bulk density similarity ratio K based on the physical and mechanical parameters of the surrounding rock is as follows:

[0053] S11: Determine the tunnel geometric similarity ratio l based on the tunnel cross-sectional dimensions, and set the unit weight similarity ratio K to 1;

[0054] S12: Determine whether the test needs to consider the long-term creep of the surrounding rock of the tunnel. If the creep of the weak surrounding rock is not considered, the simulated soil for the construction tunnel is a mixture of iron ore powder, barite powder and quartz sand. If the long-term effect of rock mass creep on the structure is considered, the simulated soil for the construction tunnel is a mixture of iron ore powder, barite powder, quartz sand, alcohol rosin solution and hydraulic oil. This is necessary to simulate the long-term effect of creep of the weak rock mass on the structure.

[0055] Without considering creep in weak surrounding rock, the following experimental parameters are obtained based on the unit weight similarity ratio:

[0056]

[0057]

[0058] In the formula C x This represents the similarity ratio between the prototype and the model, where x represents each parameter; μ is the Poisson ratio, ... Let ε be the internal friction angle, σ be the strain, σ be the stress, E be the elastic modulus, c be the cohesion, and σ be the stress. c γ is the shear strength, γ is the unit weight, and l is the length similarity ratio, i.e., the geometric similarity ratio.

[0059] When considering the long-term rheological effects of creep in weak surrounding rocks, a time similarity ratio C is added. t Based on the viscosity coefficient η, the time similarity ratio C of the Burgers creep model is further determined. t Time similarity ratio C t The formula is as follows:

[0060]

[0061] In the formula, t represents time;

[0062] When conducting long-term mechanical effect tests on the creep effect of proximity tunnels, prefabricated first and second tunnel lining structures are embedded in predetermined positions, and monitoring sensors are placed on strain gauges in the lining structures. When conducting long-term performance studies of proximity tunnels considering the creep effect, the simulated linings of the first and second tunnels need to be prefabricated. When the backfill reaches the horizontal position of the arch bottom of the first and second tunnels, the simulated linings of the first and second tunnels are embedded in the predetermined positions, and earth pressure cells and displacement gauges are pre-embedded. Similarly, the backfill is carried out in layers and compacted in layers. Strain gauges are pre-attached to the prefabricated tunnel lining structures to monitor the stress and strain of the first and second tunnel lining structures, thereby realizing the long-term mechanical effect test of the creep effect of proximity tunnels.

[0063] S2: Select a set of simulated net distance values ​​for tunnel construction simulation test. Before the test, adjust the second tunnel translation block 6 to the simulated position according to the selected simulated net distance value L, and use baffles to seal the first tunnel hole 3 and the second tunnel hole 4 on the outside. Before filling, insert baffles tightly against the front and back of the box 1 to ensure that the filling does not leak out from the tunnel hole. After filling, remove the front and back baffles. The front and back baffles should have a certain strength to resist the initial pressure of the soil, and the thickness of the baffles should be as small as possible.

[0064] S3: Based on the density ratio K, select the construction tunnel simulation soil and fill the construction tunnel simulation soil in box 1. The construction tunnel simulation soil is added layer by layer and compacted. During the filling process of the construction tunnel simulation soil, several miniature earth pressure cells and several displacement sensors are buried at the arch and middle rock wall positions of the first and second tunnels. The burial positions are determined according to the research content.

[0065] S4: Remove the baffle on the second tunnel hole 4, excavate the second tunnel, provide initial support for the second tunnel during the excavation process, and bury earth pressure cell sensors at the contact position between the initial support and the soil, and install strain gauges on the monitoring section. The strain gauges on the steel arch are used to calculate the internal force of the simulated steel arch.

[0066] The installation positions of strain gauges on several monitoring sections were determined. When the second tunnel was excavated to the predetermined monitoring section position, a simulated steel arch frame with strain gauges was installed, and shotcrete was sprayed to form a combined support structure with the simulated surrounding rock, steel arch frame, and shotcrete. Earth pressure cell sensors were also installed at the contact points between the initial support and the soil, located at the tunnel arch crown, arch waist, arch foot, and arch bottom. The shotcrete used was a mixture of gypsum and water. The strength of the shotcrete was adjusted by changing the ratio of water to gypsum to achieve a similar shotcrete mix, with the preferred ratio being 1:1.06. The simulated steel arch frame used copper strips. The parameters of the copper strips included the elastic modulus, moment of inertia, spacing between steel arch frames, and dimensions of the copper strips. The spacing between steel arch frames was determined based on the geometric similarity ratio l. The parameters of the copper strips in the simulated steel arch frame were calculated using the following formula:

[0067]

[0068] In the formula, p and m represent the prototype and the model, respectively; E is the elastic modulus; I is the moment of inertia; l represents the unit length; and g is the acceleration due to gravity.

[0069] S5: After the excavation of the second tunnel is completed, remove the external baffle of the first tunnel opening 3, and use the method in step S4 to excavate and install the detection equipment for the first tunnel; and conduct a set of tunnel construction simulation tests simulating the net distance value.

[0070] S6: After completing a set of simulated net distance values ​​for tunnel construction simulation test, excavate the simulated tunnel soil in box 1; select a set of remaining simulated net distance values, adjust the position of the second tunnel translation block 6, return to step S2, and conduct the next set of simulated net distance values ​​for tunnel construction simulation test.

[0071] S7: Repeat steps S2-S6 to continue the test until the tunnel construction simulation test of all groups of tunnel net distance values ​​is completed;

[0072] S8: After simulating the tunnel clearance values ​​for all groups, the monitoring data under different simulated clearance groups are obtained, and the simulation test of tunnel construction with different clearances is completed.

Claims

1. A model test device for simulating tunnel construction at different clear distances, characterized in that The utility model provides a box (1), the box (1) front and back side correspondingly is provided with first tunnel hole (3) and second tunnel adjusting hole (20), every second tunnel adjusting hole (20) is provided with second tunnel translation block (6), two second tunnel translation block (6) correspondingly is provided with second tunnel hole (4) on, second tunnel translation block (6) is completely shielded when sliding second tunnel hole (4); Second tunnel translation block (6) bottom is provided with rack portion (5), and rack portion (5) below is provided with translation drive mechanism, and the upper and lower sides of second tunnel adjusting hole (20) are provided with shaft rod sliding groove (17), and every shaft rod sliding groove (17) is provided with two sliding shafts (11), and every sliding shaft (11) both ends are connected with two second tunnel translation block (6) respectively; Translation drive mechanism includes the transmission gear (8) of engagement with rack portion (5) and the hand wheel (10) of engagement with transmission gear (8), and two transmission gears (8) are fixed on the box (1) through transmission shaft (7), and the hand wheel (10) is fixed on the box (1) through the rotating shaft, and the hand wheel (10) is also fixedly connected with the rocker (9); It also includes a first tunnel mounting plate (19), the first tunnel hole (3) is arranged on the first tunnel mounting plate (19), and the box (1) is provided with a first tunnel mounting hole for mounting the first tunnel mounting plate (19), and the first tunnel mounting hole is a rectangular hole; the first tunnel mounting plate (19) includes a limiting plate and a fixed plate matched with the first tunnel mounting hole, the limiting plate is installed in the first tunnel mounting hole, and the fixed plate is further provided with a bolt hole at the four corners, the bolt hole is provided with a mounting plate bolt (23), the box (1) is provided with a fixed thread hole matched with the mounting plate bolt (23), and the fixed plate is fixed on the box (1) through the mounting plate bolt (23); The periphery of the box (1) is provided with an external reinforcing lattice plate (2), and the bottom of the box (1) is provided with a bottom support partition plate (13), and the external reinforcing lattice plate (2) and the bottom support partition plate (13) are both lattice plates; the bottom support partition plate (13) is provided with a plurality of lifting holes (14), and the lifting holes (14) are strip-shaped holes; the inner sides of the two second tunnel translation blocks (6) are both provided with a limiting block (15), and the limiting block (15) is long strip-shaped.

2. The model test apparatus for simulating tunnel construction with different net distances according to claim 1, wherein, The two ends of the sliding shaft (11) are both provided with a threaded portion (21), the threaded portion (21) is provided with a shaft bolt (12), the second tunnel translation block (6) is provided with a shaft hole matched with the sliding shaft (11), and the two second tunnel translation blocks (6) are fixed outside the second tunnel adjusting hole (20) through the sliding shaft (11) and the shaft bolt (12).

3. The model test apparatus for simulating tunnel construction with different net distances according to claim 1, wherein, The sliding shaft (11) and the shaft rod sliding groove are provided with a sliding bearing (16), and the outside of the shaft rod sliding groove is provided with a bearing rolling groove (18) matched with the sliding bearing (16).

4. A test method for the model test device for simulating tunnel construction of different net distances according to any one of claims 1 to 3, characterized in that, Comprising the following steps: S1: Determine the geometric similarity ratio according to the actual construction tunnel length and the width of the box (1) , set a plurality of groups of first tunnel and second tunnel simulation net distance values , , … , n is the number of groups of simulation net distance values; the construction tunnel simulation soil bulk density similarity ratio is obtained according to the physical and mechanical parameters of the surrounding rock of the actual construction tunnel measured by the original rock indoor triaxial test ; S2: Select a group of simulated net distance values for tunnel construction simulation test, before the experiment, according to the selected simulated net distance value L, adjust the second tunnel translation block (6) to the simulation position, and block the first tunnel hole (3) and the second tunnel hole (4) with the baffle on the outside; S3: according to the volume-weight ratio , select the construction tunnel simulation soil, fill the construction tunnel simulation soil in the box (1), add and tamp the construction tunnel simulation soil layer by layer; during the filling process of the construction tunnel simulation soil, a plurality of miniature soil pressure boxes and a plurality of displacement sensors are buried at the crown of the first tunnel and the second tunnel and the position of the middle rock wall. S4: Remove the baffle on the second tunnel hole (4), excavate the second tunnel, and perform initial support during excavation, and bury soil pressure box sensors at the contact position of initial support and soil, and install strain gauges on the monitoring section; Specifically: Determine the installation position of the strain gauge on the monitoring section, when the second tunnel is excavated to the predetermined monitoring section position, lay the simulated steel arch with strain gauges, and perform shotcrete spraying to form a combined support body of simulated surrounding rock, steel arch and shotcrete; S5: After the excavation of the second tunnel is completed, remove the external baffle of the first tunnel hole (3), use the method of step S4 to excavate and install the detection equipment of the first tunnel; And a group of simulated net distance values for tunnel construction simulation test; S6: After a group of simulated net distance values for tunnel construction simulation test is completed, excavate the construction tunnel simulation soil in the box (1); Select a group of remaining simulated net distance values, adjust the position of the second tunnel translation block (6), return to step S2, and perform tunnel construction simulation test for the next group of simulated net distance values; S7: Repeat steps S2-S6 to continue the test until all groups of tunnel net distance values for tunnel construction simulation test are completed; S8: After all groups of tunnel net distance values for simulation test are completed, the monitoring data under different simulated net distance groups are obtained, and the entire simulation test of different net distance tunnel construction is completed.

5. The test method for testing the model test apparatus simulating different net clearance tunnel construction according to claim 4, wherein The construction tunnel simulation soil is a mixture of iron ore powder, barite powder and quartz sand.

6. The test method for testing the model test apparatus simulating different net clearance tunnel construction according to claim 4, wherein The construction tunnel simulation soil is a mixture of iron ore powder, barite powder, quartz sand, alcohol turpentine solution and hydraulic oil.

7. The test method for testing the model test apparatus simulating different net clearance tunnel construction according to claim 4, wherein The simulated steel arch adopts copper strip; The shotcrete adopts a mixture of gypsum and water, and the ratio of gypsum to water is 1:1.06.

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