A tunnel excavation indoor model system and its use method

Abstract

The present invention provides a tunnel excavation indoor model system and a method for using the same, and belongs to the technical field of tunnel engineering. The present invention uses a 3D printing process to prepare a geopolymer-based filler using geopolymer materials to simulate tunnel surrounding rocks; the geopolymer-based filler is provided with through holes in the front-to-back direction, the through holes simulate tunnel holes, and the through holes are filled with hot-melt fillers, and the tunnel excavation process is simulated by the hot melting process of the hot-melt fillers; different sections of the geopolymer-based filler are configured with geopolymer materials of different proportions to simulate tunnel surrounding rocks of different strengths; different sections of the geopolymer-based filler are filled with different hot-melt filler components to simulate tunnel construction processes with different support strengths under different surrounding rock conditions. The present invention can make the excavation conditions of the tunnel model as close to the actual situation as possible, improve the accuracy and credibility of the test results, and thus explore the influence of different influencing factors and various complex working conditions on tunnel excavation.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering, and in particular relates to a tunnel excavation indoor model system and a use method thereof. Background Art

[0002] Tunnel engineering has the characteristics of great concealment and many interference factors, so it is necessary to test the tunnel engineering in advance to verify the feasibility of the construction plan. Similarity model test is based on similarity theory. The prototype is scaled according to the rules through calculation, so as to complete the process of simulating the prototype in the laboratory. This is one of the important methods to study tunnel construction problems.

[0003] In the related technology, there are two methods of drilling holes in tunnel model tests: the first is to "dig holes first and then load", but it is difficult to correctly reflect the stress conditions of the tunnel surrounding rock; the second is to load first and then dig holes using tools such as knives according to pre-set geometric boundary conditions. However, using tools to dig the soil can easily disturb the soil outside the geometric boundary and cause collapse, which is different from the pre-set test conditions and ultimately affects the accuracy of the experimental results.

[0004] Therefore, it is necessary to provide a tunnel excavation indoor model system and a method of using the same to solve the above problems. Summary of the invention

[0005] The present invention provides a tunnel excavation indoor model system and a method for using the same. According to the actual stratum characteristics of the tunnel, fillers with different strength ratios are used to form surrounding rocks of different grades through 3D printing. According to the grade of the tunnel surrounding rock, the diameter and spacing of the heating rings are dynamically changed to simulate the initial support strength and construction progress of the tunnel excavation, so that the excavation conditions of the tunnel model are as close to the actual situation as possible, and the accuracy and credibility of the test results are improved, thereby exploring the influence of different influencing factors and various complex working conditions on tunnel excavation, and effectively solving at least one technical problem in the background technology.

[0006] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0007] A tunnel excavation indoor model system, comprising:

[0008] Model box, enclosing a receiving space;

[0009] A geopolymer-based filler is contained in the containing space, the geopolymer-based filler is made of geopolymer material by 3D printing process, and is used to simulate tunnel surrounding rock; the geopolymer-based filler is provided with through holes in the front-to-back direction, the through holes are used to simulate tunnel holes, the through holes are filled with hot-melt fillers, and the excavation process of the tunnel is simulated by the hot melting process of the hot-melt fillers;

[0010] Different sections of the geopolymer-based filler are configured with geopolymer materials of different proportions to simulate tunnel surrounding rocks of different strengths; different sections of the geopolymer-based filler are filled with hot-melt filler components of different compositions to simulate tunnel construction processes with different support strengths under different surrounding rock conditions.

[0011] As a preferred improvement, the model box is formed by splicing angle steels to form a frame body, the bottom surface is placed on the ground or other carriers, a first flexible layer is arranged between the bottom surface and the ground / carrier, and the first flexible layer is made of rubber or sponge material; the four sides are covered with transparent acrylic panels, and the top surface is empty.

[0012] As a preferred improvement, cracks and holes are formed inside the geopolymer-based filler to simulate the cracks and holes naturally existing in the tunnel surrounding rock.

[0013] As a preferred improvement, the geopolymer material is composed of the following ingredients in parts by weight: silica fume: 4 to 5 parts, fly ash: 3 to 3.6 parts, alkali-activated material: 0.33 to 0.5 parts, polypropylene fiber: 0.22 to 0.30 parts, copper tailings: 2 to 2.5 parts, blast furnace slag: 2 to 2.5 parts, thickener: 0.002 to 0.006 parts, water reducer: 0.009 to 0.011 parts, water: 4.4 to 6 parts, fine sand: 7.5 parts; coarse sand: 2.5 parts, wherein the alkali-activated material is compounded with NaOH and NaSiO3 in a weight ratio of 1:3.

[0014] As a preferred improvement, according to the geological survey report, the actual surrounding rock grade is divided into 6 levels according to the compressive strength, from the best to the worst, divided into grades I to VI, and 6 geopolymer materials with different proportions are used to simulate 6 different surrounding rock grades; among which:

[0015] The hot-melt filler in the segment where the surrounding rock of grade V~VI is located is modified asphalt with a melting point of 100℃~120℃;

[0016] The hot melt filler filled in the segment where the III~IV grade surrounding rock is located is modified rosin with a melting point of 70℃~90℃;

[0017] The hot-melt filler filled in the section where the I~II grade surrounding rock is located is paraffin, with a melting point of 55℃~60℃.

[0018] As a preferred improvement, it also includes a loading device, which includes a second flexible layer, a steel plate, a slider, a reaction beam and a jack. The second flexible layer is laid on the top of the geopolymer-based filler and completely covers the geopolymer-based filler. The steel plate is laid on the top of the second flexible layer and completely covers the second flexible layer. The slider is installed on the angle steel on the top of the model box and can slide straight along the angle steel to adjust its position. The reaction beam is fixed on the slider and keeps consistent with the movement state of the slider. The jack is installed below the reaction beam and contacts the steel plate. The load is applied to the steel plate through the jack and the load is transmitted to the geopolymer-based filler to simulate the formation load.

[0019] As a preferred improvement, it also includes an excavation simulation device, which includes a heating ring and a wire, wherein the heating ring is embedded in the hot melt filler, and the wire is connected to the heating ring for electrical conduction between the heating ring and an external power supply, and the heating ring heats the hot melt filler after being energized, and the hot melt filler melts due to the heat, thereby simulating the excavation process of the tunnel; the diameter of the heating ring matches the surrounding rock grade of the current segment, and the distances between two adjacent heating rings in the hot melt fillers of different segments are different; for I ~II grade surrounding rock, the diameter of the heating ring is selected to be 90% of the diameter of the hot melt filler; for III~IV grade surrounding rock, the diameter of the heating ring is selected to be 80% of the diameter of the hot melt filler; for V~VI grade surrounding rock, the diameter of the heating ring is selected to be 70% of the diameter of the hot melt filler; in the modified asphalt segment, the distance between two adjacent heating rings is 10cm; in the modified rosin segment, the distance between two adjacent heating rings is 8cm; in the paraffin segment, the distance between two adjacent heating rings is 6cm.

[0020] As a preferred improvement, the heating circular ring includes multiple layers of heating single rings spaced from the inside to the outside and a junction box for fixing the heating single rings, each layer of the heating single ring includes an annular segment and a straight line segment, the annular segment is a non-closed annular structure with openings spaced at both ends, the number of the straight line segments is two, two of the straight line segments are fixed at both ends of the annular segment, the two straight line segments are spaced in parallel, and the straight line segments of multiple heating single rings are fixed side by side in the junction box.

[0021] As a preferred improvement, it also includes a measuring device, which includes a DIC measurement system and an optical fiber strain measurement system, wherein the DIC measurement system includes a DIC camera and a DIC data processing module, the DIC camera is arranged opposite to the through hole, and is used to measure the displacement field and strain field of the tunnel model holes and surrounding fillers during tunnel excavation, and the DIC data processing module is connected to the DIC camera, and is used to process the data measured by the DIC camera and output the results required for measurement; the optical fiber strain measurement system includes an optical fiber strain gauge and a stress data processing module, the optical fiber strain gauge is attached to the hole wall of the through hole, and is used to measure the stress changes of the tunnel model holes and surrounding fillers during tunnel excavation, and the stress data processing module is connected to the optical fiber strain gauge, and is used to process the data measured by the optical fiber strain gauge and output the results required for measurement.

[0022] A method for using the above-mentioned tunnel excavation indoor model system comprises the following steps:

[0023] Step S1, providing a 3D printed geopolymer-based filler, and arranging an excavation simulation device in a through hole of the geopolymer-based filler;

[0024] Step S2, injecting molten hot melt filler into the through hole of the geopolymer-based filler, and waiting for it to cool and harden;

[0025] Step S3, applying a load to the geopolymer-based filler, and then turning on the power of the excavation simulation device, the excavation simulation device heats the hot-melt filler, and simulates the tunnel excavation process through the thermal melting process of the hot-melt filler;

[0026] Step S4, using a measuring device to measure the displacement field, strain field and stress data of the through hole and the surrounding geopolymer-based filler during the tunnel excavation process, and evaluating the tunnel excavation process based on the measured data.

[0027] The beneficial effects of the present invention are:

[0028] According to the geological survey report and the actual geological characteristics of the tunnel, fillers with different strength ratios are used to form different grades of tunnel surrounding rocks through 3D printing. According to the grade of tunnel surrounding rock, the diameter and spacing of the heating rings change dynamically to simulate the initial support strength and construction progress of the tunnel excavation, so that the excavation conditions of the tunnel model are as close to the actual situation as possible, improving the accuracy and credibility of the test results, so as to explore the impact of different influencing factors and various complex working conditions on tunnel excavation. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

[0030] Figure 1 A three-dimensional structural diagram showing a tunnel excavation indoor model system provided in Example 1;

[0031] Figure 2 express Figure 1 Schematic diagram of the structure of the geopolymer-based filler;

[0032] Figure 3 A three-dimensional structural diagram showing an excavation simulation device. DETAILED DESCRIPTION

[0033] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Example 1

[0034] like Figure 1-Figure 3 As shown, this embodiment provides a tunnel excavation indoor model system, including a model box 10, a geopolymer-based filler 20, a loading device 30, an excavation simulation device 40 and a measuring device.

[0035] The model box 10 is a rectangular or cube frame structure, which encloses a receiving space for receiving the geopolymer-based filler 20. Specifically, the model box 10 is formed by splicing angle steels to form a frame body, the bottom surface is placed on the ground or other carriers, and a first flexible layer is arranged between the bottom surface and the ground / carrier, and the first flexible layer is made of rubber or sponge material; the four sides are covered with transparent acrylic plates, and the top surface is empty, through which the state of the geopolymer-based filler 20 inside can be clearly observed.

[0036] The geopolymer-based filler 20 is made of geopolymer material using a 3D printing process and is used to simulate tunnel surrounding rock. The geopolymer-based filler 20 uses more environmentally friendly geopolymer materials instead of traditional cement, which can effectively reduce carbon emissions. Among them, the geopolymer material is configured with the following components in parts by weight: silica fume: 4~5 parts, fly ash: 3~3.6 parts, alkali-activated material: 0.33~0.5 parts, polypropylene fiber: 0.22~0.30 parts, copper tailings: 2~2.5 parts, blast furnace slag: 2~2.5 parts, thickener: 0.002~0.006 parts, water reducer: 0.009~0.011 parts, water: 4.4~6 parts, fine sand: 7.5 parts, coarse sand: 2.5 parts, wherein the alkali-activated material is NaOH and NaS i O3 is compounded in a weight ratio of 1:3.

[0037] The geopolymer-based filler 20 is provided with a through hole 21 in the front-to-back direction, and the through hole 21 is used to simulate a tunnel hole. The through hole 21 is filled with a hot melt filler 22, and the tunnel excavation process is simulated by the thermal melting process of the hot melt filler 22. The geopolymer-based filler 20 is also formed with cracks and holes to simulate the cracks and holes naturally existing in the tunnel surrounding rock. The transparent acrylic plate needs to be provided with an avoidance hole at the position corresponding to the through hole 21, so that the through hole 21 is connected to the outside, and the melted hot melt filler 22 can be discharged from the through hole 21.

[0038] The geopolymer-based filler 20 is divided into a plurality of sections along the extension direction of the through hole 21, and each section is configured with geopolymer materials of different proportions to simulate tunnel surrounding rocks of different strengths. In this embodiment, the actual surrounding rock grade is divided into 6 levels according to the compressive strength according to the geological survey report, from the best to the worst, and is divided into grades I to VI. Six different surrounding rock grades are simulated using six different proportions of geopolymer materials. Compared with a single proportion, the simulation result of the surrounding rock is more realistic.

[0039] Specifically, the geological survey report shows that the tunnel passes through various surrounding rock levels, and the compressive strength of these levels is mostly between 10MPa and 60MPa. Therefore, in this embodiment, the geopolymer-based filler 20 is divided into 6 sections, namely: VI level surrounding rock, V level surrounding rock, IV level surrounding rock, III level surrounding rock, II level surrounding rock and I level surrounding rock. The proportions used for different surrounding rock levels are as follows:

[0040] Ratio a: silica fume: 5 parts, fly ash: 3.6 parts, alkali-activated material: 0.50 parts, polypropylene fiber: 0.30 parts, copper tailings: 2 parts, blast furnace slag: 2 parts, thickener: 0.002 parts, water reducer: 0.011 parts, water: 4.4 parts, fine sand: 7.5 parts, coarse sand: 2.5 parts. The compressive strength of the geopolymer-based filler obtained under this ratio is close to 60MPa, which is used to simulate Class I surrounding rock.

[0041] Proportion b: silica fume: 4.8 parts, fly ash: 3.5 parts, alkali-activated material: 0.47 parts, polypropylene fiber: 0.28 parts, copper tailings: 2.1 parts, blast furnace slag: 2.1 parts, thickener: 0.003 parts, water reducer: 0.011 parts, water: 4.7 parts, fine sand: 7.5 parts, coarse sand: 2.5 parts. The compressive strength of the geopolymer-based filler obtained under this ratio is close to 50MPa, which is used to simulate Class II surrounding rock.

[0042] Ratio c: silica fume: 4.6 parts, fly ash: 3.4 parts, alkali activated material: 0.43 parts, polypropylene fiber: 0.27 parts, copper tailings: 2.2 parts, blast furnace slag: 2.2 parts, thickener: 0.004 parts, water reducer: 0.01 parts, water: 5.0 parts, fine sand: 7.5 parts, coarse sand: 2.5 parts. The compressive strength of the geopolymer-based filler obtained under this ratio is close to 40MPa, which is used to simulate Class III surrounding rock.

[0043] Ratio d: silica fume: 4.4 parts, fly ash: 3.3 parts, alkali activated material: 0.4 parts, polypropylene fiber: 0.25 parts, copper tailings: 2.3 parts, blast furnace slag: 2.3 parts, thickener: 0.004 parts, water reducer: 0.01 parts, water: 5.4 parts, fine sand: 7.5 parts, coarse sand: 2.5 parts. The compressive strength of the geopolymer-based filler obtained under this ratio is close to 30MPa, which is used to simulate Class IV surrounding rock.

[0044] Proportion e: silica fume: 4.2 parts, fly ash: 3.2 parts, alkali-activated material: 0.36 parts, polypropylene fiber: 0.24 parts, copper tailings: 2.4 parts, blast furnace slag: 2.4 parts, thickener: 0.005 parts, water reducer: 0.009 parts, water: 5.7 parts, fine sand: 7.5 parts, coarse sand: 2.5 parts. The compressive strength of the geopolymer-based filler obtained under this ratio is close to 20MPa, which is used to simulate Class V surrounding rock.

[0045] Ratio f: silica fume: 4 parts, fly ash: 3 parts, alkali activated material: 0.33 parts, polypropylene fiber: 0.22 parts, copper tailings: 2.5 parts, blast furnace slag: 2.5 parts, thickener: 0.006 parts, water reducer: 0.009 parts, water: 6 parts, fine sand: 7.5 parts, coarse sand: 2.5 parts. The compressive strength of the geopolymer-based filler obtained under this ratio is close to 10MPa, which is used to simulate Class VI surrounding rock.

[0046] The 3D printing process of the geopolymer-based filler 20 can be carried out by using conventional techniques in the art. This embodiment specifically provides a 3D printing step:

[0047] (1) Six geopolymer materials are prepared according to the above-mentioned ratios a, b, c, d, e, and f;

[0048] (2) Send the geopolymer material with ratio a to the print head of the 3D printer and set the print head outlet cross-sectional area to 115mm 2 , horizontal printing speed is 170cm / min, vertical printing speed is 0.6m / h, extrusion speed is 0.04m 3 / h to print and obtain the geopolymer-based filler of the first segment;

[0049] (3) Clean the residual material in the print head, and then send the geopolymer materials with the ratios of b, c, d, e, and f into the print head of the 3D printer in sequence, keep the same printing parameters in step (2) for printing, and obtain the second to sixth segments of geopolymer-based fillers in sequence, with a thickness of 190 mm for each segment.

[0050] In the 3D printing process, after printing a certain length, a subtractive rod is used to randomly scratch the surface to form cracks and holes. Finally, a geopolymer-based filler with a size of about 820*820*1140mm is formed, and the model similarity ratio is 1:80.

[0051] The hot melt filler 22 is also divided into different sections, and different sections are made of different hot melt materials. Specifically, the section made of modified asphalt has a melting point of 100°C~120°C and is filled in the section where the V~VI grade surrounding rock is located; the section made of modified rosin has a melting point of 70°C~90°C and is filled in the section where the III~IV grade surrounding rock is located; the section made of paraffin has a melting point of 55°C~60°C and is filled in the section where the I~II grade surrounding rock is located. The hot melt fillers of different sections are made of hot melt materials with different melting points and matched with surrounding rocks of different strengths, which are used to simulate the tunnel construction process in which the better the surrounding rock conditions, the smaller the support strength, and the worse the surrounding rock conditions, the higher the support strength.

[0052] The loading device 30 includes a second flexible layer 31, a steel plate 32, a slider 33, a reaction beam 34 and a jack 35. The second flexible layer 31 is laid on the top of the geopolymer-based filler 20 and completely covers the geopolymer-based filler 20. The steel plate 32 is laid on the top of the second flexible layer 31 and completely covers the second flexible layer 31. The slider 33 is installed on the angle steel on the top of the model box 10 and can slide along the angle steel straight line to adjust the position. The slider 33 can be an inverted L-shaped angle steel block. The two ends of the reaction beam 34 are fixed on the slider 33 and are consistent with the movement state of the slider 33. The jack 35 is installed below the reaction beam 34 and contacts the steel plate 32. The jack 35 applies a load to the steel plate 32 and transmits the load to the geopolymer-based filler 20 to simulate the stratum load. The slider 33 is set to adjust the position of the jack 35 and change the loading position. In this embodiment, the second flexible layer 31 is made of rubber or sponge material and has a thickness of 20 mm; the thickness of the steel plate 32 is 10 mm, and the pressure applied by the jack is 50-100 kPa.

[0053] The excavation simulation device 40 includes a heating ring 41 and a wire 42. The heating ring 41 is embedded in the hot melt filler 22, and the wire 42 is connected to the heating ring 41 for electrical conduction between the heating ring 41 and an external power source.

[0054] The heating ring 41 heats the hot melt filler 22 after being powered on, and the hot melt filler 22 melts under the heat, simulating the tunnel excavation process. The melted hot melt filler 22 is in liquid state and can flow out of the through hole 21, simulating the discharge process of tunnel excavation.

[0055] The diameter of the heating ring 41 matches the surrounding rock grade of the current segment. For the surrounding rock of grade I to II, the diameter of the heating ring 41 is selected to be 90% of the diameter of the hot melt filler 22; for the surrounding rock of grade III to IV, the diameter of the heating ring 41 is selected to be 80% of the diameter of the hot melt filler 22; for the surrounding rock of grade V to VI, the diameter of the heating ring 41 is selected to be 70% of the diameter of the hot melt filler 22. The diameter of the heating ring 41 is different, and the residue of the hot melt filler 22 after heating is also different: the smaller the diameter, the more residue of the hot melt filler 22. The residual hot melt filler 22 is used to simulate the early strength concrete of the spraying. The higher the surrounding rock grade, the weaker the surrounding rock, and more early strength concrete needs to be sprayed.

[0056] In the hot melt filler 22 of different sections, the distance between two adjacent heating rings 41 is different, which is used to simulate the construction characteristics of actual tunnel construction, that is, the worse the surrounding rock grade, the slower the construction progress, and the better the surrounding rock grade, the faster the construction progress. In the modified asphalt section, the distance between two adjacent heating rings 41 is 10 cm; in the modified rosin section, the distance between two adjacent heating rings 41 is 8 cm; in the paraffin section, the distance between two adjacent heating rings 41 is 6 cm.

[0057] The heating circular ring 41 includes multiple layers of heating single rings 411 spaced from the inside to the outside and a junction box 412 for fixing the heating single rings 411. Each layer of the heating single ring 411 includes a ring segment 4111 and a straight line segment 4112. The ring segment 4111 is a non-closed circular ring structure with openings spaced at both ends. There are two straight line segments 4112, which are fixed at both ends of the ring segment 4111. The two straight line segments 4112 are spaced in parallel, and the straight line segments 4112 of multiple heating single rings 4111 are fixed side by side in the junction box 412.

[0058] The multiple layers of the heating single rings 411 are arranged at intervals along the radial direction of the hot-melt filler 22 , and different radial positions of the hot-melt filler 22 can be heated at the same time, so that the hot-melt filler 22 can be melted evenly.

[0059] The measuring device is used to measure the state data of the geopolymer-based filler 20, and includes a DIC measuring system and an optical fiber strain measuring system, wherein the DIC measuring system includes a DIC camera and a DIC data processing module, the DIC camera is arranged opposite to the through hole 21, and is used to measure the displacement field and strain field of the tunnel model hole and the surrounding filler during tunnel excavation, and the DIC data processing module is connected to the DIC camera, and is used to process the data measured by the DIC camera and output the results required for measurement; the optical fiber strain measuring system includes an optical fiber strain gauge and a stress data processing module, the optical fiber strain gauge is attached to the hole wall of the through hole 21, and is used to measure the stress change of the tunnel model hole and the surrounding filler during tunnel excavation, and the stress data processing module is connected to the optical fiber strain gauge, and is used to process the data measured by the optical fiber strain gauge and output the results required for measurement. The combination of the two methods can improve the accuracy of measurement.

[0060] It can be understood that since the optical fiber strain gauge and the heating ring 41 are both arranged inside the geopolymer-based filler 20, wiring holes need to be provided on the geopolymer-based filler 20 and the model box 10 to extend the signal line of the optical fiber strain gauge and the wire 42 to the outside, which can be done by conventional techniques in the field. Example 2

[0061] This embodiment also provides a method for using the above-mentioned tunnel excavation indoor model system, comprising the following steps:

[0062] Step S1, providing a 3D printed geopolymer-based filler, and arranging an excavation simulation device in a through hole of the geopolymer-based filler;

[0063] Step S2, injecting molten hot melt filler into the through hole of the geopolymer-based filler, and waiting for it to cool and harden;

[0064] Step S3, applying a load to the geopolymer-based filler, and then turning on the power of the excavation simulation device, the excavation simulation device heats the hot-melt filler, and simulates the tunnel excavation process through the thermal melting process of the hot-melt filler;

[0065] Step S4, using a measuring device to measure the displacement field, strain field and stress data of the through hole and the surrounding geopolymer-based filler during the tunnel excavation process, and evaluating the tunnel excavation process based on the measured data.

[0066] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A tunnel excavation indoor model system, characterized in that: include: Model box, enclosing a receiving space; A geopolymer-based filler is contained in the containing space, the geopolymer-based filler is made of geopolymer material by 3D printing process, and is used to simulate tunnel surrounding rock; the geopolymer-based filler is provided with through holes in the front-to-back direction, the through holes are used to simulate tunnel holes, the through holes are filled with hot-melt fillers, and the excavation process of the tunnel is simulated by the hot melting process of the hot-melt fillers; The excavation simulation device comprises a heating ring and a wire, wherein the heating ring is embedded in the hot melt filler, the wire is connected to the heating ring and is used for electrical conduction between the heating ring and an external power source, and the heating ring heats the hot melt filler after being energized, and the hot melt filler melts due to the heat, so as to simulate the excavation process of the tunnel, wherein the heating ring comprises a plurality of heating single rings spaced from the inside to the outside; the diameter of the heating ring matches the surrounding rock grade of the current segment, and the spacing between two adjacent heating rings in the hot melt fillers of different segments is different; For the surrounding rock of grade I~II, the diameter of the heating ring is selected as 90% of the diameter of the hot melt filler; for the surrounding rock of grade III~IV, the diameter of the heating ring is selected as 80% of the diameter of the hot melt filler; for the surrounding rock of grade V~VI, the diameter of the heating ring is selected as 70% of the diameter of the hot melt filler; in the modified asphalt segment, the distance between two adjacent heating rings is 10cm; in the modified rosin segment, the distance between two adjacent heating rings is 8cm; in the paraffin segment, the distance between two adjacent heating rings is 6cm; Different sections of the geopolymer-based filler are configured with geopolymer materials of different proportions to simulate tunnel surrounding rocks of different strengths; different sections of the geopolymer-based filler are filled with hot-melt fillers of different compositions to simulate tunnel construction processes with different support strengths under different surrounding rock conditions; According to the geological survey report, the actual surrounding rock grade is divided into 6 levels according to the compressive strength, from the best to the worst, divided into grades I to VI. Six different geopolymer materials with different proportions are used to simulate six different surrounding rock grades; among them: The hot-melt filler in the segment where the surrounding rock of grade V~VI is located is modified asphalt with a melting point of 100℃~120℃; The hot melt filler filled in the segment where the III~IV grade surrounding rock is located is modified rosin with a melting point of 70℃~90℃; The hot-melt filler filled in the section where the I~II grade surrounding rock is located is paraffin, with a melting point of 55℃~60℃.

2. The tunnel excavation indoor model system according to claim 1, characterized in that: The model box is formed by splicing angle steels to form a frame body, the bottom surface is placed on the ground or a carrier, a first flexible layer is arranged between the bottom surface and the ground / carrier, and the first flexible layer is made of rubber or sponge material; the four sides are covered with transparent acrylic plates, and the top surface is empty.

3. The tunnel excavation indoor model system according to claim 1, characterized in that: The geopolymer-based filler also has cracks and holes formed inside, which are used to simulate the cracks and holes naturally existing in the tunnel surrounding rock.

4. The tunnel excavation indoor model system according to claim 1, characterized in that: The geopolymer material is composed of the following ingredients in parts by weight: silica fume: 4-5 parts, fly ash: 3-3.6 parts, alkali-activated material: 0.33-0.5 parts, polypropylene fiber: 0.22-0.30 parts, copper tailings: 2-2.5 parts, blast furnace slag: 2-2.5 parts, thickener: 0.002-0.006 parts, water reducer: 0.009-0.011 parts, water: 4.4-6 parts, fine sand: 7.5 parts, coarse sand: 2.5 parts, wherein the alkali-activated material is compounded with NaOH and NaSiO3 in a weight ratio of 1:

3.

5. The tunnel excavation indoor model system according to claim 2, characterized in that: It also includes a loading device, which includes a second flexible layer, a steel plate, a slider, a reaction beam and a jack. The second flexible layer is laid on the top of the geopolymer-based filler and completely covers the geopolymer-based filler. The steel plate is laid on the top of the second flexible layer and completely covers the second flexible layer. The slider is installed on the angle steel on the top of the model box and can slide straightly along the angle steel to adjust its position. The reaction beam is fixed on the slider and keeps consistent with the movement state of the slider. The jack is installed below the reaction beam and contacts the steel plate. The load is applied to the steel plate through the jack, and the load is transmitted to the geopolymer-based filler to simulate the formation load.

6. The tunnel excavation indoor model system according to claim 1, characterized in that: The heating circular ring also includes a wiring collection box for fixing the heating single ring. Each layer of the heating single ring includes a ring segment and a straight line segment. The ring segment is a non-closed ring structure with openings formed at both ends. There are two straight line segments, which are fixed at both ends of the ring segment. The two straight line segments are arranged in parallel and spaced apart. The straight line segments of multiple heating single rings are fixed side by side in the wiring collection box.

7. The tunnel excavation indoor model system according to claim 1, characterized in that: It also includes a measuring device, which includes a DIC measuring system and an optical fiber strain measuring system, wherein the DIC measuring system includes a DIC camera and a DIC data processing module, the DIC camera is arranged opposite to the through hole, and is used to measure the displacement field and strain field of the tunnel model hole and the surrounding filler during the tunnel excavation process, and the DIC data processing module is connected to the DIC camera, and is used to process the data measured by the DIC camera and output the results required for the measurement; the optical fiber strain measurement system includes an optical fiber strain gauge and a stress data processing module, the optical fiber strain gauge is attached to the hole wall of the through hole, and is used to measure the stress change of the tunnel model hole and the surrounding filler during the tunnel excavation process, and the stress data processing module is connected to the optical fiber strain gauge, and is used to process the data measured by the optical fiber strain gauge and output the results required for the measurement.

8. A method for using the tunnel excavation indoor model system according to any one of claims 1 to 7, characterized in that: The steps include: Step S1, providing a 3D printed geopolymer-based filler, and arranging an excavation simulation device in a through hole of the geopolymer-based filler; Step S2, injecting molten hot melt filler into the through hole of the geopolymer-based filler, and waiting for it to cool and harden; Step S3, applying a load to the geopolymer-based filler, and then turning on the power of the excavation simulation device, the excavation simulation device heats the hot-melt filler, and simulates the tunnel excavation process through the thermal melting process of the hot-melt filler; Step S4, using a measuring device to measure the displacement field, strain field and stress data of the through hole and the surrounding geopolymer-based filler during the tunnel excavation process, and evaluating the tunnel excavation process based on the measured data.

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