Device for measuring rock sample change under simulation of different supports of tunnel and use method

Abstract

The invention discloses a device and a method for measuring rock sample change coefficients by simulating different supports of a tunnel, the device comprises a support structure which is composed of a combinable hemisphere steel structure, a support anchor rod and a lock catch, the surface of the hemisphere is provided with uniform round holes for inserting the anchor rod to simulate various supports, and the lock catch is fixed to ensure stable constraint; simulating materials: mixing gypsum, barite powder, quartz sand, an expanding agent and a borax solution according to a ratio, and simulating high ground stress by utilizing chemical expansion of the expanding agent; layered molding: an acrylic mold is matched with a polarization motor for layered pouring and leveling, and uniform thickness of a rock sample ring layer is ensured; a waterproof stress piece and a strain piece collect data in real time, the internal structure is synchronously analyzed in combination with CT scanning, and a stress-structure development model is established. According to the invention, the limitation of single support and mechanical loading of a traditional device is broken through, efficient simulation of multiple support forms and high ground stress loading is realized through integrated design, the experiment complexity and cost are reduced, and an accurate laboratory means is provided for tunnel rock sample development prediction.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel excavation support, and particularly to a device for measuring the change of rock samples under different supports of a tunnel and a using method thereof. Background Art

[0002] Traditional tunnel support simulation devices mostly rely on mechanical and hydraulic loading systems, and have the following defects: 1. Comparative document CN110658064B discloses a device and method for simulating and obtaining the optimal support force of a fluid lining support for a tunnel. Its protected rights are: "Side plates are respectively arranged on the four side surfaces and the top of a rectangular pit body. Hydraulic jacks for applying pressure are arranged outside the side plates at the positions of the four side surfaces. The side plate located at the top is anchored below the ground of the rectangular pit body through anchor bolts; a pressure relief hole is processed at the center position of one side surface of the side plate, a hole is processed on the soft rock sample at the position of the pressure relief hole, and a pressure sensor and a strain gauge are arranged on the inner wall of the hole; the pressure sensor and the strain gauge are respectively connected to a acquisition system through wires; a partition support is arranged inside the hole, and oil sacs are arranged in different partitions of the partition support. It solves the problem of determining the magnitude of the optimal support force of the fluid lining of the tunnel, and this method is simple to operate, low in cost, short in measurement time and high in measurement accuracy." However, it cannot implement multiple forms of support such as anchor bolts and fluid filling; 2. Comparative document CN101344445B discloses a self-balanced true three-dimensional loading model test bench with a sliding wall. Its protected claims are "Its loading system is arranged outside the structural wall, including a gantry reaction frame, a structural wall and a sliding wall. The upper, lower, left and right surfaces of the model body can be loaded through the gantry reaction frame. In the front and back directions of the model body, a hydraulic loading device is only arranged outside the structural wall at the back. The front and back self-balanced symmetric loading can be realized through several reaction cross beams and side tie rods. A sliding wall is arranged between the model body and the structural wall, and several strip-shaped observation windows are arranged around the position of the cavity on the structural wall. The present invention can realize three-dimensional graded loading, is convenient for excavation and support operations, and can significantly reduce the surface friction of the model body during loading and other advantages." However, the operation of the sliding wall model is complex, and the external pressure causes large friction loss, affecting the loading accuracy.

[0003] Moreover, the structures of existing devices are fixed (such as square or barrel-shaped), and it is difficult to simulate different in-situ stress environments and the differences in rock sample layers. Therefore, a device for measuring the change of rock samples under different supports of a tunnel and a using method thereof are proposed to solve the above problems. Summary of the Invention

[0004] The purpose of the present invention is to overcome the above deficiencies and provide a device for measuring the change of rock samples under different supports of a tunnel and a using method thereof to solve the problems raised in the background art.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is: a device for measuring the change coefficient of rock samples under different supports of a simulated tunnel, including: a support structure for simulating the constraint effect under different support conditions of the tunnel, including a combinable hemispherical spherical steel structure, support bolts and a tongue lock switch. Uniformly distributed round holes are provided on the arc surface of the spherical steel structure for inserting support bolts, and two hemispherical structures are fixed by the tongue lock switch; a similar filling material, which is composed of gypsum, barite powder, quartz sand, an expansive agent and a borax solution mixed in proportion, for simulating the physical properties of rock samples at different elevations; a molding device, including a detachable hemispherical mold, a bottom plate and a convex polarization motor, for pouring and leveling the similar material in layers; a measuring instrument, including a waterproof stress gauge, strain gauge, CT scanner and data acquisition system, for real-time monitoring of the stress-strain data and internal structure changes of the rock sample.

[0006] Preferably, silicone rubber material is installed in the round holes of the spherical steel structure, and a detachable track module and a wire groove are provided inside the hemispherical structure for connecting the terminal wires of the measuring instrument.

[0007] Preferably, the mixing ratio of the similar filling material is: 20% gypsum, 10% barite powder, 15% quartz sand, 30% expansive agent, 25% borax solution, and it is stirred and mixed evenly by a vibrating rod.

[0008] Preferably, the mold of the molding device is made of acrylic material, and a bottom plate track is provided on its side wall. The bottom plate is slidably connected to the inner wall of the mold through a lubricating fluid.

[0009] Preferably, the surfaces of the stress gauge and the strain gauge are coated with a silicone waterproof layer and are connected to a data collection box through a mother-daughter terminal wire. The data collection box communicates with a computer to process data.

[0010] Preferably, a protrusion is provided in the middle of the placement plane of the spherical steel structure for precise fitting with the insertion position of the support bolt.

[0011] In addition, the present invention also discloses a method for using a device for measuring the change coefficient of rock samples under different supports of a simulated tunnel, including the following steps: Step 1: Select a matching placement plane according to the support conditions, and insert support bolts to simulate different support forms; Step 2: After mixing and stirring the similar filling material according to the ratio, pour it into the molding device in layers and level it with a convex polarization motor; Step 3: Install the initial-set rock sample model into the spherical steel structure, and connect the stress gauge, strain gauge and data acquisition system; Step 4: Lock the tongue lock switch fixing device, perform CT scanning and real-time data acquisition, and analyze the stress-strain and internal structure changes of the rock sample.

[0012] Furthermore, the pouring sequence of the layered pouring is from outside to inside. After each layer is poured, it is left to stand until the initial setting, and the position of the model is ensured to be accurate through the track module.

[0013] Furthermore, the borax solution is added to the mixed materials in batches to avoid too fast reaction rate.

[0014] Furthermore, the CT scan is carried out synchronously with the data acquisition, and a rock sample development model is established by comparing the CT values with the stress-strain data.

[0015] The present invention has the following beneficial effects: 1. By using the spherical steel structure of the hemispherical structure in the present invention, the tunnel rock sample model simulated in the laboratory is more in line with the actual engineering application. Different from the previous barrel structure and square structure, such a spherical structure makes the development of the rock sample have no deviation on the surface layer, making up for the deficiencies. 2. By using the reserved circular holes and the placement plane with small protrusions on the concave surface shape in the present invention, the tunnel rock sample model in the laboratory can simulate the development changes of the rock sample under different support conditions, truly meeting the requirements of multiple uses of one device and reducing the requirements for laboratory funds. 3. By reserving the detachable track module in the present invention, such a detachable module can meet the requirements of different experiments and can simulate tunnel models under different elevations and different in-situ stress environments. 4. The present invention uses similar materials such as expansion agents to replace the stress field suffered by the rock sample under tunnel conditions, replacing most of the current mechanical hydraulic devices, and does not need to use the proportional pressure application method to replace. It can well complete the indoor loading process, lower the experimental threshold, meet the experimental requirements of laboratories under different conditions, and is more versatile. 5. By using the hemispherical mold in the present invention, when simulating the rock sample, the ratio can be completed according to the different divided circles, and the same thickness of different circles and the same position of the spherical rock samples on both sides can be ensured, without deviation. And reserving the track module on the spherical steel structure can ensure the stability and accurate position of the simulated layered rock sample placement. 6. The stress gauges and strain gauges treated with waterproof glue in the present invention can completely block the influence of the borax solution on the gauges, and there will be no sudden short-circuit problem of the gauges. Through the application of the data acquisition box and CT technology, a rock sample development model can be established through analysis. 7. The present invention can simulate the development of the interior of the rock mass of the tunnel rock sample under the action of the stress field under different support conditions, can better simulate the in-situ stress distribution of the primary stress field inside the rock mass, reduces the difference of the same surface layer, makes the stress evenly distributed inside the simulated rock mass, can truly meet the experimental requirements of multiple uses of the device, and lowers the threshold of the simulation experiment. Description of the Drawings

[0016] Figure 1 is the overall structure diagram of the simulated tunnel support device of the present invention; Figure 2 is the support structure device diagram in the present invention; Figure 3 is the simulated rock similar material diagram of the present invention; Figure 4 is the film-making system device diagram of the present invention; Figure 5 is the measurement system device diagram of the present invention. Specific embodiments

[0017] The present invention will be further described below in conjunction with the accompanying drawings and embodiments: See Figures 1 to 5 , this embodiment provides a device for measuring the change coefficient of rock samples under different supports of a simulated tunnel, including: Support structure 1: The spherical steel structure 11 is composed of two hemispherical steel materials with a thickness ≥ 1 cm and a diameter of 20 cm. When combined, it is mechanically locked through a tongue switch 13. The diameter of the round hole on the arc surface matches the support bolt 12. After inserting the bolt, it is sealed with silicone rubber material 15 to ensure uniform transmission of the binding force; Similar filling material 2: After being mixed according to the ratio, it is stirred into a uniform slurry by a vibrating rod 26 to simulate the mechanical properties of rock masses at different elevations. The expansion agent 24 is used to replace traditional hydraulic loading to generate internal stress through chemical reactions; Molding device 3: The inner wall of the hemispherical acrylic mold 31 is coated with a lubricating fluid 33. The bottom plate 32 slides along the side wall track 16. During pouring, it is vibrated and leveled by a convex surface polarization motor 34 to ensure that the thickness of each layer is consistent; Measuring instrument 4: The stress gauge 41 and the strain gauge 42 are coated with a silicone waterproof layer on the surface, with a thickness ≥ 0.5 mm. They are connected to the data collection box 44 through a mother and son terminal wire to collect data in real time and transmit it to the computer 45. The CT scanner 43 scans the internal structure of the rock sample regularly and compares and analyzes it with the stress data.

[0018] Preferably, a silicone rubber material 15 is installed in the round hole of the spherical steel structure 11. A detachable track module 16 and a wire groove 17 are provided inside the hemispherical structure for connecting the terminal wires of the measuring instrument. Silicone rubber material 15: Filled in the gap between the round hole and the support bolt 12, with a thickness of about 3 - 5 mm, which plays a role in sealing and buffering, preventing the leakage of the filling material and stress concentration. Track module 16: Made of aluminum alloy, fixed inside the hemisphere by bolts, used to accurately position the bottom plate 32 of the molding device 3 to ensure the alignment of the positions of rock samples in different circles. Wire groove 17: Located at the hemisphere interface, with a width of 5 - 8 mm, used to lay the terminal wires of the stress gauge 41 and the strain gauge 42 to avoid wire entanglement or damage due to stress.

[0019] Preferably, the proportion of the similar filling material 2 is as follows: 20% gypsum, 10% barite powder, 15% quartz sand, 30% expansion agent, and 25% borax solution, and they are stirred and mixed evenly by a vibrating rod 26. Weigh each component according to the mass ratio. For example, if the total mass is 100 kg, then 20 kg of gypsum, 10 kg of barite powder, etc. First, mix the gypsum, barite powder, quartz sand, and expansion agent evenly, and then add 25 of the borax solution in portions, with the addition amount each time not exceeding 10% of the total amount. The stirring time is ≥5 minutes to avoid uneven hardening of the material caused by too fast reaction.

[0020] Preferably, the mold 31 of the mold-making device 3 is made of acrylic material, and its side wall is provided with a bottom plate track 16. The bottom plate 32 is slidably connected to the inner wall of the mold through a lubricating fluid 33. The inner wall of the acrylic mold is evenly coated with a silicone-based lubricating fluid 33 with a thickness of about 0.1 mm to reduce the adhesion force between the material and the mold and facilitate demolding. The bottom plate 32 moves along the track 16 through rollers, and the moving speed is controlled at 2 - 3 cm / s to ensure a stable pouring process.

[0021] Preferably, the surfaces of the stress gauge 41 and the strain gauge 42 are coated with a silicone waterproof layer and are connected to the data collection box 44 through a mother-daughter terminal wire. The data collection box 44 communicates with the computer 45 to process data. After the silicone layer is coated, it is left to cure for 24 hours to ensure complete coverage of the surface of the stress gauge including the edges, and the waterproof grade reaches IP67. The mother-daughter terminal wire uses a copper core shielded wire, and the interface is sealed with a heat shrinkable tube to prevent the borax solution 25 from seeping in and causing a short circuit.

[0022] Preferably, a protrusion is provided in the middle of the placement plane 14 of the spherical steel structure 11 for precise fitting with the insertion position of the support bolt 12. The height of the protrusion is 5 mm, and the shape is hemispherical, which matches the groove at the end of the support bolt 12 to ensure that the bolt is closely fitted with the spherical structure after insertion and prevent the support system from loosening.

[0023] In addition, the present invention also discloses a method for using a device for measuring the change coefficient of a rock sample under different supports of a simulated tunnel, including the following steps: Step 1: Select a matching placement plane 14 according to the support conditions and insert the support bolt 12 to simulate different support forms; Step 2: After mixing and stirring the similar filling material 2 according to the proportion, pour it into the mold-making device 3 in layers and level it through a convex surface polarization motor 34; Step 3: Install the initially set rock sample model into the spherical steel structure 11 and connect the stress gauge 41 and the strain gauge 42 to the data acquisition system; Step 4: Lock the tongue switch 13 to fix the device, perform a CT scan 43 and real-time data acquisition, and analyze the stress and strain of the rock sample and the change of the internal structure.

[0024] Furthermore, the pouring sequence of the layered pouring is from the outside to the inside. After each layer is poured, it is left to stand until the initial setting, and the position of the model is ensured to be accurate through the track module 16. Pour layer by layer from the outermost layer to the inside, and the standing time for each layer is ≥ 30 minutes to avoid interlayer displacement.

[0025] Furthermore, the borax solution 25 is added to the mixed materials in portions to avoid too fast reaction rate. It can be added in 3 portions, with an interval of 2 minutes each time, and the stirring speed ≤ 200 rpm to prevent the increase of material pores caused by violent reaction.

[0026] Furthermore, the CT scan 43 is carried out synchronously with the data acquisition, and a rock sample development model is established by comparing the CT values with the stress-strain data. The CT scan data and the stress-strain data are aligned by time stamps, and a three-dimensional stress distribution model is generated by using the built-in software of the computer 45, and the development trend of rock sample fractures is analyzed by comparing the CT value differences.

[0027] The above embodiments are only the preferred technical solutions of the present invention and should not be regarded as limitations on the present invention. The protection scope of the present invention should be the technical solutions recorded in the claims, including the equivalent replacement solutions of the technical features in the technical solutions recorded in the claims. That is, the equivalent replacement improvements within this scope are also within the protection scope of the present invention.

Claims

1. An apparatus for measuring the variation coefficient of rock samples under different supports in a simulated tunnel, characterized in that, Including: A support structure (1) for simulating the restraint effect under different support conditions of a tunnel, including a combinable hemispherical spherical steel structure (11), support bolts (12) and a tongue lock switch (13). Uniformly distributed round holes are provided on the arc surface of the spherical steel structure (11) for inserting the support bolts (12), and the two hemispherical structures are fixed by the tongue lock switch (13); A similar filling material (2) is composed of gypsum (21), barite powder (22), quartz sand (23), an expansion agent (24) and a borax solution (25) mixed in proportion, and is used to simulate the physical properties of rock samples at different elevations; A molding device (3) includes a detachable hemispherical mold (31), a bottom plate (32) and a convex surface polarization motor (34), and is used for layered pouring and leveling of the similar material; A measuring instrument (4) includes a waterproof stress gauge (41), a strain gauge (42), a CT scanner (43) and a data acquisition system, and is used for real-time monitoring of the stress and strain data of the rock sample and the change of the internal structure.

2. The device for measuring the change coefficient of rock samples under different supports in a simulated tunnel according to claim 1, characterized in that, A silicone rubber material (15) is installed in the round hole of the spherical steel structure (11), and a detachable track module (16) and a wire groove (17) are arranged inside the hemispherical structure for connecting the terminal wires of the measuring instrument.

3. The device for measuring the change coefficient of rock samples under different supports in a simulated tunnel according to claim 1, wherein The mixing ratio of the similar filling material (2) is: 20% gypsum, 10% barite powder, 15% quartz sand, 30% expansion agent, 25% borax solution, and it is stirred and mixed evenly by a vibrating rod (26).

4. The device for measuring the change coefficient of rock samples under different supports in a simulated tunnel according to claim 1, characterized in that, The mold (31) of the molding device (3) is made of acrylic material, and a bottom plate track (16) is provided on its side wall. The bottom plate (32) is slidably connected to the inner wall of the mold through a lubricating fluid (33).

5. An apparatus for measuring the variation coefficient of a rock sample under different supports in a simulated tunnel according to claim 1, characterized in that, The surfaces of the stress gauge (41) and the strain gauge (42) are coated with a silicone waterproof layer and are connected to a data collection box (44) through a mother-daughter terminal wire. The data collection box (44) communicates with a computer (45) to process data.

6. The device for measuring the variation coefficient of rock samples under different supports in a simulated tunnel according to claim 1, wherein, A protrusion is provided in the middle of the placement plane (14) of the spherical steel structure (11) for precise fitting with the insertion position of the support bolt (12).

7. A method for using a device for measuring the change coefficient of rock samples under different supports in a simulated tunnel according to any one of claims 1-6, characterized in that, Including the following steps: Step 1: Select a matching placement plane (14) according to the support condition, and insert the support bolt (12) to simulate different support forms; Step 2: After mixing and stirring the similar filling material (2) according to the mixing ratio, pour it into the molding device (3) in layers and level it by the convex surface polarization motor (34); Step 3: Install the initially set rock sample model into the spherical steel structure (11), and connect the stress gauge (41), the strain gauge (42) and the data acquisition system; Step 4: Lock the tongue lock switch (13) to fix the device, perform a CT scan (43) and real-time data acquisition, and analyze the stress and strain of the rock sample and the change of the internal structure.

8. The usage method of a device for measuring the change coefficient of rock samples under different supports in a simulated tunnel according to claim 7, characterized in that, The order of the layered pouring is from the outside to the inside. After each layer is poured, it is left to stand until initial setting, and the position of the model is ensured to be accurate through the track module (16).

9. The method of using a device for measuring the change coefficient of a rock sample under different support conditions in a simulated tunnel according to claim 7, characterized in that, The borax solution (25) is added to the mixed material in portions to avoid too fast reaction rate.

10. The usage method of a device for measuring the change coefficient of a rock sample under different supports in a simulated tunnel according to claim 7, characterized in that, The CT scan (43) is carried out synchronously with the data acquisition, and a rock sample development model is established by comparing the CT values with the stress and strain data.

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