A test device for model testing of square tunnel excavation

Abstract

The present invention relates to a test device for model testing of square tunnel excavation, and relates to the technical field of underground engineering model testing. It includes a profile excavation cutting mechanism, a rotary propulsion mechanism, and a support and slag removal device; wherein the profile excavation cutting mechanism is located at the excavation end of the profile excavation device, and is used to achieve profile excavation; the rotary propulsion mechanism is located at the tail end of the profile excavation cutting mechanism, and is used to drive the profile excavation cutting mechanism; the support and slag removal device is used to provide support for the profile excavation cutting mechanism and the rotary propulsion mechanism, and to achieve slag extraction during excavation. The present invention adopts a profile excavation cutting mechanism to achieve profile excavation, and installs a tungsten alloy cutting head on the cross-shaped cutter head, so that it can achieve better impact and cutting effects during excavation, and ensure the progress of tunnel excavation, thereby effectively solving the problem of square cross-section forming.

Description

Technical Field

[0001] The invention relates to the technical field of underground engineering model tests, in particular to a test device for model testing of square tunnel excavation. Background Art

[0002] In recent years, with the increasing number of urban underground space developments, the use of giant-section underground structures (tunnels) has also increased. In order to study the impact of tunneling construction on the surrounding environment and building disturbances, domestic and foreign scholars commonly use research methods such as empirical formula method, analytical method, theoretical analysis method, model test method, numerical analysis method, etc. Since tunneling construction involves complex construction processes and management links, it is basically not repeatable, and it is difficult to obtain accurate research results under single variable conditions. Model tests can better reproduce the tunnel construction process, have strict theoretical basis and are simple and easy to operate, and the reliability of research results is relatively high. Therefore, model test methods are widely used in geotechnical and underground engineering fields.

[0003] From the perspective of the use function in the field of geotechnical and underground engineering, the cross-sectional form of highway tunnels, railway tunnels, subway tunnels, pedestrian tunnels, underground common trenches, etc. is most suitable in the form of rectangle or square. The construction equipment of square-section tunnels has always been a difficult point in the field of underground engineering technology, because the cutterhead of the shield tunneling machine is usually round and cannot adapt to the construction of special-shaped sections, such as square-section tunnels. Compared with the circular section, the effective use area of ​​the square section is usually more than 20%, and the rectangle is the most economical in municipal tunnel engineering. The shield method and the rectangular jacking method have little impact on the surrounding environment and low comprehensive cost. However, at this stage, during the excavation process of the large-section rectangular jacking machine, the clear cross-sectional area is large, the risk of full-section excavation is high, and it is difficult to achieve face pressure control, resulting in poor face stability and large stratum disturbance.

[0004] The selection of tunneling parameters (advance speed, shield diameter) during the construction process has a great influence on the degree of disturbance of the surrounding soil. In actual projects, the tunneling parameters are usually adjusted based on feedback from the construction site, which has a certain lag in risk control and poses a safety hazard. However, there are currently few square tunnel profiling tunneling devices used for model tests during tunneling construction, so it is impossible to know the evolution process of soil disturbance in the square tunnel before construction. Therefore, in view of the shortcomings of the existing technology, a square tunnel profiling tunneling device for model tests was designed.

[0005] According to the principle of similarity, the shape of the tunnel model in the geotechnical engineering similar physical model test should be similar to the prototype tunnel, but the size is generally only 1 / 10-1 / 200 of the prototype tunnel. Common shapes of geotechnical engineering tunnels include circular, straight wall arch, three-center arch, rectangular, etc. The better the similarity of the test model, the more similar the construction process such as tunnel excavation is to the prototype project, the more reliable the test results are, and the greater the reference value for engineering personnel.

[0006] At present, the following four methods are commonly used for tunnel excavation in model tests:

[0007] (1) When making the model, a column with the same shape as the excavated tunnel is embedded in the specified position. After the model is dry, the column is pulled out to form the tunnel in one step, and then loaded. This method, that is, prefabricate the tunnel and then load it, is not practical because the excavation construction of the tunnel on site is carried out in the original rock stress field.

[0008] (2) When making the model, a column with the same shape as the excavated hole is embedded in the specified position. The column can be composed of several small sections, and the mechanical properties (such as elastic modulus) are as consistent as possible with the model. After the model is dried, it is loaded to the initial stress, and then the embedded small sections of the column are taken out one by one to simulate segmented excavation. That is, the tunnel is embedded first, and then taken out after loading to simulate excavation. This method may encounter the situation where the tunnel deforms and shrinks under high pressure, and the front column is not easy to remove.

[0009] (3) The manufactured model is dried and loaded to the initial stress, and a tunnel of a certain shape is manually excavated at a predetermined position. This is the manual excavation method. The tunnel excavated by this method has an irregular shape and a rough shape. The size, shape and excavation progress of the tunnel cannot be accurately controlled. Especially when the excavated tunnel is long and there is hidden excavation, manual excavation in a small space is very difficult.

[0010] (4) The manufactured model is dried and loaded to an initial stress, and a tunnel of a specified shape is mechanically excavated at a predetermined position using a drilling rig or a small excavation device, i.e., a mechanical automatic excavation method. The tunnel excavated by this method has a regular shape.

[0011] At present, high-precision excavation has been achieved for circular tunnels in physical simulation tests. For example:

[0012] The "quantitative simulation test system and method for inducing coal and gas outburst during excavation of Shimen tunnel" invented by Chinese patent CN201711463818.7 realizes the quantitative control of excavation and capture of outburst process of circular tunnel in coal and gas outburst model test; the "a circular tunnel full cutting excavation experimental device" invented by Chinese patent CN201620279733.8 is suitable for full-section cutting and excavation of circular tunnels in similar simulation tests; the "supporting three-dimensional physical model test robot system simulation mining method" invented by Chinese patent CN201610278246.4 can realize the automatic excavation and working face recovery of simulated circular tunnels through robots. However, for non-circular tunnels commonly used in engineering projects such as straight wall arches, three-center arches, and rectangles, one-time full-section mechanical automatic excavation has not been realized in model tests.

[0013] In addition, a large number of tunneling devices used in rectangular cross-section tunnel construction have also been developed in the prior art, such as:

[0014] Chinese patent 201910791075.9 discloses a profiling system and method for model test of tunnel excavation of arbitrary shapes, which is composed of a profiling mechanism, a rotating forward mechanism, a support frame and a slag discharge device. The profiling mechanism includes a positioning cutter head, a front cutter disc, a rear cutter disc and a profiling frame for excavating tunnels. The positioning cutter head, the front cutter disc and the rear cutter disc rotate coaxially, wherein the positioning cutter head is used for positioning, the front cutter disc is used for excavating circular tunnels, and the rear cutter disc drives the cutter head to rotate along the profiling frame to expand and repair the circular tunnel into the shape of the profiling frame; only the profiling frame needs to be replaced according to the shape and size of the tunnel to realize the mechanized excavation of the full section of any tunnel shape. It solves the problem that only circular tunnels can be excavated in the existing geotechnical similarity model test, and provides detailed principles and technical support for the excavation of straight wall arch tunnels. However, for the profiling excavation of square tunnels, the device only provides a solution for changing the profiling frame, which cannot be scientifically and effectively implemented under the conditions of existing theories and technologies.

[0015] Chinese patent CN202211268313.6 relates to a shield all-terrain excavation simulation test method, a hydraulic loading intelligent control model test bench based on the shield all-terrain excavation simulation, which is mainly used for indoor model tests simulating shield construction and belongs to the field of tunnel construction engineering technology. Indoor model tests of shield construction can be carried out to conduct research on shield diameter, burial depth, excavation parameters, construction conditions, etc. The patent includes the following steps: Step 1: Acquisition of soil sample parameters, pre-set to the host computer; Step 2: Determination of the test plan, pre-set to the host computer, forming a system test task; Step 3: Installation of baffles; Step 4: Preparation of soil samples; Step 5: Positioning of soil samples; Step 6: Pressurization; Step 7: Shield excavation; Step 8: Data collection; Step 9: End of test; Step 10: Decompression and sample removal. It has the advantages of being able to simulate the entire process of shield tunneling, to study different shield tunneling parameters, to simulate shield construction at any buried depth, and to simulate the shield crossing over and under existing structures. However, it is relatively inconvenient to discharge soil and slag during cross-section cutting, and the stability of the excavation process cannot be guaranteed. In addition, the excavation accuracy is not high, the test accuracy is poor, and the structure is relatively complex.

[0016] Based on the above analysis, the tunneling system in the square section tunnel construction of the above units has the following shortcomings:

[0017] 1. The common excavation device used in rectangular section tunnel construction is generally composed of several circular section cutter heads. This excavation method has a slow tunnel contour forming process and is time-consuming and labor-intensive.

[0018] 2. The existing square-shaped tunneling devices used in model tests have problems such as low accuracy and complex structure.

[0019] 3. At present, when the excavation device of the square section construction machinery is cutting a square tunnel, there are many places that the blade cannot cut, which makes tunnel construction difficult. Summary of the invention

[0020] The purpose of the present invention is to make up for the deficiencies of the above-mentioned prior art and provide a square tunnel profiling system for model testing that can cut the entire section, which can generally adapt to the construction of square-section tunnels, thereby greatly improving the construction adaptability of the tunnel boring machine and increasing the function of the tunnel boring machine. The present invention improves the efficiency and accuracy of the model test, controls the shape of the tunnel section to become a square section completely and accurately, solves the problem of forming a square tunnel, and greatly increases the function and adaptability of the tunnel boring machine.

[0021] To achieve the above-mentioned purpose, the present invention provides a test device for model testing of square tunnel excavation, comprising a contour excavation cutting mechanism, a rotary propulsion mechanism, and a support and slag discharge device; wherein:

[0022] The profiling excavation cutting mechanism is located at the excavation end of the profiling excavation device and is used to realize profiling excavation;

[0023] The rotary propulsion mechanism is located at the rear end of the profiling excavation and cutting mechanism and is used to drive the profiling excavation and cutting mechanism;

[0024] The support and slag discharge device is used to provide support for the contour excavation cutting mechanism and the rotary propulsion mechanism, and to realize the extraction and discharge of slag during the excavation process.

[0025] The contour excavation cutting mechanism includes: a central cutter, a disc plus wheel, a square chain and a first step-stage scraper; the central cutter is connected to the output end of the rotary propulsion mechanism, a plurality of disc plus wheels are provided, which are evenly distributed on the circumference of the central cutter in a square shape, a first gear is provided on the disc plus wheel, the square chain surrounds the outer sides of the plurality of disc plus wheels and meshes with the first gear, and a step-stage scraper is installed at the head end of the square chain. The disc plus wheel and the first step-stage scraper are driven by the rotation of the square chain to achieve the leveling of the surrounding soil, so that the rough outline of the square tunnel is formed.

[0026] Furthermore, the central tool includes a central shaft and a cross-shaped cutter disc, the central shaft is installed at the output end of the rotary propulsion mechanism, the cross-shaped cutter disc is installed at the head end of the central shaft, and a plurality of tungsten alloy cutting bits are installed on the cross-shaped cutter disc.

[0027] Furthermore, a positioning cutter head is installed at the center of the cross-shaped cutter disc, and a second step scraper is installed on the positioning cutter head.

[0028] The rotary propulsion mechanism includes a movable bearing seat, a trimming shaft, a propulsion motor and a triangular chain. One end of the movable bearing seat is connected to the disc plus wheel bearing on one side, and the other end is installed with a second gear. The third gear is installed on the central shaft. The triangular chain surrounds the outer side of the second gear and the third gear and meshes with the second gear and the third gear respectively. The disc plus wheel tail end on the other side is installed with a trimming shaft, and the trimming shaft is connected to the bearing of the support and slag discharge device. The propulsion motor drives the central shaft to rotate, realizes the forward and backward movement of the device, and provides power for the contour excavation device.

[0029] Furthermore, the support and slag removal device includes a support frame and a negative pressure slag removal device, the support frame is used to provide installation support for the contour excavation cutting mechanism and the rotary propulsion mechanism, and the negative pressure slag removal device is installed at the rear end of the support frame.

[0030] Furthermore, the support and slag discharge device also includes a vibration base, which is installed at the rear end of the support frame, and the negative pressure slag discharge device passes through the vibration base.

[0031] Furthermore, the support frame includes an outer frame, an outer frame base, a connecting plate cover and a cover plate, the head end of the outer frame base is connected to the outer frame, the tail end is connected to the connecting plate cover, and the cover plate is installed in the gap between the outer frame base and the outer shell.

[0032] Furthermore, the negative pressure slag discharge device includes a slag suction port, a negative pressure vacuum pump, a dustproof net and a slag storage box. The slag suction port is installed at the tail end of the support frame, and a dustproof net is provided at the top of the slag storage box. The slag suction port is connected to the slag storage box through a pipeline, and the pipeline passes through the dustproof net and extends into the interior of the slag storage box. The negative pressure vacuum pump is installed on the pipeline outside the slag storage box.

[0033] The beneficial effects of the present invention are:

[0034] (1) The present invention adopts a contour excavation cutting mechanism to achieve contour excavation. A tungsten alloy cutting head is installed on the cross-shaped cutter head, so that it can achieve better impact and cutting effects during the excavation process and ensure the progress of tunnel excavation, thereby effectively solving the problem of square cross-section forming.

[0035] (2) The present invention designs structures such as a disc plus wheel and a first step scraper, which greatly improves the efficiency and accuracy of the model test, can control the shape of the tunnel section to become a regular square section with complete accuracy, solves the problem of forming a square tunnel, and greatly increases the function and adaptability of the tunnel boring machine.

[0036] (3) The present invention has the advantages of simple structure and strong applicability, and is capable of constructing square cross-section tunnels. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0038] Figure 2 It is a top view of the overall structure of the present invention;

[0039] Figure 3 It is a front view of the central tool part of the present invention;

[0040] Figure 4 It is a schematic diagram of the installation structure of the rotary propulsion structure of the present invention;

[0041] Figure 5 This is a schematic diagram of the installation structure of the first step scraper and the square chain of the present invention;

[0042] Figure 6 It is a schematic structural diagram of the negative pressure slag discharge device of the present invention.

[0043] Among them, in the figure:

[0044] 1-1 positioning cutter head, 1-2 cross-shaped cutter disc, 1-3 tungsten alloy cutting cutter head, 1-4 disc plus wheel, 1-5 first step scraper, 1-6 square chain, 2-1 propulsion motor, 2-2 movable bearing seat, 2-3 trimming shaft, 2-4 center shaft, 2-5 triangular chain, 3-1 vibration base, 3-2 negative pressure slag discharge device, 3-3 connecting plate cover, 3-4 cover plate, 3-5 outer frame base, 3-6 outer frame, 4-1 slag suction port, 4-2 negative pressure vacuum pump, 4-3 dustproof net, 4-4 slag storage box. DETAILED DESCRIPTION

[0045] In order to achieve the above-mentioned purpose and effect, the technical means and structures adopted by the present invention are described in detail with reference to the accompanying drawings for the features and functions of the preferred embodiments of the present invention.

[0046] like Figure 1-5 As shown, the present invention provides a test device for model testing of square tunnel excavation, including a contour excavation cutting mechanism, a rotary propulsion mechanism, and a support and slag discharge device; wherein,

[0047] The profiling excavation cutting mechanism is located at the excavation end of the profiling excavation device and is used to realize profiling excavation;

[0048] The rotary propulsion mechanism is located at the rear end of the profiling excavation and cutting mechanism and is used to drive the profiling excavation and cutting mechanism;

[0049] The support and slag discharge device is used to provide support for the contour excavation cutting mechanism and the rotary propulsion mechanism, and to realize the extraction and discharge of slag during the excavation process.

[0050] The contour excavation cutting mechanism includes: a center cutter, a disc plus wheel 1-4, a square chain 1-6 and a first step scraper 1-5; the center cutter is connected to the output end of the rotary propulsion mechanism, the disc plus wheel 1-4 is provided with a plurality of discs and wheels 1-4, which are evenly distributed on the circumference of the center cutter in a square shape, the disc plus wheel 1-4 is provided with a first gear, the square chain 1-6 surrounds the outer side of the plurality of disc plus wheels 1-4 and meshes with the first gear, and a step scraper is installed at the head end of the square chain 1-6. In this embodiment, four disc plus wheels 1-4 are provided, which are distributed at the four corners in a square frame. The four disc plus wheels 1-4 are rotated to flatten the surrounding soil to form the general outline of a square tunnel, and the first step scraper 1-5 is distributed on the entire circle of square chains 1-6.

[0051] The center tool includes a center shaft 2-4 and a cross-shaped cutter disc 1-2. The center shaft 2-4 is installed at the output end of the rotating propulsion mechanism, and the cross-shaped cutter disc 1-2 is installed at the head end of the center shaft 2-4. A plurality of tungsten alloy cutting bits 1-3 are installed on the cross-shaped cutter disc 1-2. The tungsten alloy cutting bits 1-3 are 16mm triangular cone-shaped tungsten alloy cutting bits 1-3, and a total of twenty are arranged.

[0052] In this embodiment, a positioning cutter head 1-1 is installed at the center of the cross-shaped cutter disc 1-2, and a second step-stage scraper is installed on the positioning cutter head 1-1. Six second step-stage scrapers are arranged on the positioning cutter head 1-1, which are mainly used for positioning the contour excavation cutting mechanism.

[0053] The rotary propulsion mechanism includes a movable bearing seat 2-2, a trimming shaft 2-3, a propulsion motor 2-1 and a triangular chain 2-5. One end of the movable bearing seat 2-2 is connected to the bearing of the disc plus wheel 1-4 on one side, and the other end is installed with a second gear. The central shaft 2-4 is installed with a third gear. The triangular chain 2-5 surrounds the outer side of the second gear and the third gear, and meshes with the second gear and the third gear respectively. The tail end of the disc plus wheel 1-4 on the other side is installed with a trimming shaft 2-3, and the trimming shaft 2-3 is connected with the bearing of the support and slag discharge device. Gears are installed on both sides of the bottom of the central shaft 2-4 and the movable bearing seat 2-2. The three gears are connected by the triangular chain 2-5, so that they rotate synchronously with the central shaft 2-4, driving the top first gear and the square chain 1-6 to rotate, thereby driving the first step scraper 1-5 to rotate, and realizing the formation of a square tunnel.

[0054] The support and slag removal device includes a support frame and a negative pressure slag removal device 3-2. The support frame is used to provide installation support for the contour excavation cutting mechanism and the rotary propulsion mechanism. The negative pressure slag removal device 3-2 is installed at the tail end of the support frame. The support and slag removal device also includes a vibration base 3-1. The vibration base 3-1 is installed at the tail end of the support frame. The negative pressure slag removal device 3-2 runs through the vibration base 3-1. The negative pressure slag removal device 3-2 and the vibration base 3-1 are installed on the support frame, and can be used for excavation exhaust and slag removal as well as to prevent vibration of the contour excavation cutting device during operation. The vibration base 3-1, the negative pressure slag removal device 3-2 and the connecting cover plate 3-4 surround the propulsion motor 2-1. In addition to supporting it, it also plays a certain protective role for the propulsion motor 2-1.

[0055] The support frame includes an outer frame 3-6, an outer frame base 3-5, a connecting plate cover 3-3 and a cover plate 3-4, the head end of the outer frame base 3-5 is connected to the outer frame 3-6, the tail end is connected to the connecting plate cover 3-3, and the cover plate 3-4 is installed in the gap between the outer frame base 3-5 and the outer shell. The support frame can support the soil, is in a square shape, and protects the rotating propulsion mechanism.

[0056] The negative pressure slag discharge device includes a slag suction port 4-1, a negative pressure vacuum pump 4-2, a dustproof net 4-3 and a slag storage box 4-4. The slag suction port 4-1 is installed at the tail end of the support frame. A dustproof net 4-3 is provided at the top of the slag storage box 4-4. The slag suction port 4-1 is connected to the slag storage box 4-4 through a pipeline. The pipeline passes through the dustproof net 4-3 and extends into the interior of the slag storage box 4-4. The negative pressure vacuum pump 4-2 is installed on the pipeline outside the slag storage box 4-4 to facilitate the extraction of slag during excavation.

[0057] The present invention adopts a contouring excavation cutting mechanism to realize contouring excavation, and installs a tungsten alloy cutting head on the cross-shaped cutter disc, so that it can achieve better impact and cutting effects during the excavation process, and ensure the progress of tunnel excavation, thereby effectively solving the problem of forming square sections. The present invention designs structures such as a disc plus wheel and a first step scraper, which greatly improves the efficiency and accuracy of the model test, and can control the shape of the tunnel section to become a regular square section completely and accurately, solves the problem of forming square tunnels, and greatly increases the function and adaptability of the tunnel boring machine. The present invention has the advantages of simple structure and strong applicability, and can be competent for the construction of square section tunnels. The present invention can realize the one-time forming of the full-section mechanical excavation of the square tunnel in the geotechnical model test, and the debris cleaning during the excavation of the present invention is convenient, and can be discharged through a negative pressure slag discharge device, and has the characteristics of strong adaptability, convenient operation, compact structure, and diverse functions.

[0058] The test method of the square tunnel profiling device used for model testing includes the following contents:

[0059] A profile excavation device for excavating a tunnel of any shape in a model test is arranged in front of the model to be excavated;

[0060] The positioning cutter head, the cross-shaped cutter disc, the disc plus wheel and the first step scraper are driven to rotate by the propulsion motor, and the contour excavation cutting mechanism and the propulsion motor are driven by the propulsion motor, so that the excavation process is promoted while rotating the excavation until the excavation reaches the designated position and the construction of the tunnel is completed, so as to realize one-time full-section excavation of any shape tunnel;

[0061] During the excavation process, the generated gangue is discharged through the vacuum cleaner and the support and slag discharge device to ensure smooth excavation.

[0062] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A test device for model testing of square tunnel excavation, characterized in that: It includes a profile excavation cutting mechanism, a rotary propulsion mechanism, and a support and slag removal device; among which, The profile excavation cutting mechanism is located at the excavation end of the test device and is used to achieve profile excavation; The rotary propulsion mechanism is located at the rear end of the profiling excavation and cutting mechanism and is used to drive the profiling excavation and cutting mechanism; The support and slag removal device is used to provide support for the contour excavation cutting mechanism and the rotary propulsion mechanism, and to realize the extraction and removal of slag during the excavation process; The contour excavation cutting mechanism includes: a center cutter, a disc plus wheel, a square chain and a first step scraper; the center cutter is connected to the output end of the rotary propulsion mechanism, a plurality of disc plus wheels are provided, which are evenly distributed in a square shape on the circumference of the center cutter, a first gear is provided on the disc plus wheel, the square chain surrounds the outer sides of the plurality of disc plus wheels and meshes with the first gear, and a first step scraper is installed at the head end of the square chain.

2. A test device for model testing of square tunnel excavation as claimed in claim 1, characterized in that: The central tool comprises a central shaft and a cross-shaped cutter disc. The central shaft is mounted on the output end of the rotary propulsion mechanism, and the cross-shaped cutter disc is mounted on the head end of the central shaft. A plurality of tungsten alloy cutting bits are mounted on the cross-shaped cutter disc.

3. A test device for model testing of square tunnel excavation as claimed in claim 2, characterized in that: A positioning cutter head is installed at the center of the cross-shaped cutter disc, and a second step scraper is installed on the positioning cutter head.

4. A test device for model testing of square tunnel excavation as claimed in claim 3, characterized in that: The rotary propulsion mechanism includes a movable bearing seat, a trimming shaft, a propulsion motor and a triangular chain. One end of the movable bearing seat is connected to the disc plus wheel bearing on one side, and the other end is equipped with a second gear. The third gear is installed on the central shaft. The triangular chain surrounds the outer sides of the second gear and the third gear and meshes with the second gear and the third gear respectively. The tail end of the disc plus wheel on the other side is equipped with a trimming shaft, and the trimming shaft is connected to the bearing of the support and slag discharge device.

5. A test device for model testing of square tunnel excavation as claimed in claim 1 or 4, characterized in that: The support and slag removal device includes a support frame and a negative pressure slag removal device. The support frame is used to provide installation support for the contour excavation cutting mechanism and the rotary propulsion mechanism. The negative pressure slag removal device is installed at the rear end of the support frame.

6. A test device for model testing of square tunnel excavation as claimed in claim 5, characterized in that: The support and slag discharge device also includes a vibration base, which is installed at the rear end of the support frame, and the negative pressure slag discharge device passes through the vibration base.

7. A test device for model testing of square tunnel excavation as claimed in claim 6, characterized in that: The support frame includes an outer frame, an outer frame base, a connecting plate cover and a cover plate. The head end of the outer frame base is connected to the outer frame, and the tail end is connected to the connecting plate cover. The cover plate is installed in the gap between the outer frame base and the outer frame.

8. A test device for model testing of square tunnel excavation as claimed in claim 5, characterized in that: The negative pressure slag discharge device includes a slag suction port, a negative pressure vacuum pump, a dustproof net and a slag storage box. The slag suction port is installed at the tail end of the support frame. A dustproof net is provided at the top of the slag storage box. The slag suction port is connected to the slag storage box through a pipeline. The pipeline passes through the dustproof net and extends into the interior of the slag storage box. The negative pressure vacuum pump is installed on the pipeline outside the slag storage box.

Images