Method and device for testing in-situ expansive force of expansive rock in tunnel

Abstract

The invention relates to the technical field of geotechnical engineering, and particularly discloses a method and device for testing the in-situ expansive force of expansive rock in a tunnel, and the method comprises the steps: selecting a test point, excavating a groove, and installing a force measuring system comprising at least three soil pressure gauges, two force measuring systems are used for testing the expansive force after water injection, and one force measuring system is not used for reference after water injection; a water injection system is arranged and comprises a water injection pipe, sponge, a water tank and a control valve, the water injection pipe is wound around the tested soil pressure gauge, fine sand is arranged in the water injection pipe, holes are formed in the surface for water injection, and a water outlet is reserved outside a groove; the groove is backfilled with cement mortar, and after the cement mortar is solidified into a whole, construction excavation of the counter-force system is completed; after installation is completed, the initial reading of the soil pressure gauge is firstly tested, surrounding rock is expanded through water injection of the water tank and the valve, and the reading is monitored and recorded; and finally, comparing the reading changes of the water injection point and the non-water injection point, and evaluating the surrounding rock expansive force. The test period is short, and the expansive force characteristic of the expansive rock under the in-situ condition is truly reflected.

Description

Technical Field

[0001] The invention belongs to the technical field of geotechnical engineering, and in particular relates to a method and a device for testing the in-situ expansion force of expansion rock in a tunnel. Background Art

[0002] Swelling rock is a geological body with significant expansion and contraction formed in the natural geological process. It has the characteristics of "swelling when absorbing water and shrinking when losing water". Its cyclic changes will cause the structural stress to become complicated, resulting in the stress and deformation of the support structure of the expansive soil tunnel being different from those of the general tunnel. Usually, the relationship between the water content and the volume expansion rate of the expansive soil is measured by indoor tests, and then the expansion force is calculated by the finite element method based on the volume expansion rate to obtain the relationship between the water content and the expansion force of the expansive soil. Then, according to the water content measured on site and its range of variation, the corresponding expansion force is calculated, so as to master the stress and deformation distribution law of the support structure of the expansive soil tunnel, and provide a basis for the design and construction of such tunnels. Therefore, expansion force testing is very necessary.

[0003] At present, the technology for testing the swelling force of swelling rocks under indoor experimental conditions has been relatively mature. However, the indoor test results are affected by factors such as sample size and test conditions, and cannot truly reflect the on-site situation. At the same time, the indoor test is affected by the sample quality and the test cycle is long. The in-situ test has a short test cycle and measures the swelling force in the actual environment. The test results are accurate and reliable and can better reflect the actual stress state. Therefore, the in-situ swelling force test of the swelling rock is particularly important.

[0004] Therefore, we propose a method and device for testing the in-situ expansion force of expansive rock in a tunnel to solve the above technical problems. Summary of the invention

[0005] In order to solve the technical problems existing in the above-mentioned prior art, the present invention provides a method and a device for testing the in-situ expansion force of expansion rock in a tunnel.

[0006] The technical solution adopted by the present invention is as follows:

[0007] A method for testing the in-situ expansion force of expansion rock in a tunnel comprises the following steps:

[0008] a. Select a test point on the tunnel lining, dig a groove and install a force measuring system. The force measuring system includes at least three earth pressure gauges, two of which are used as water injection earth pressure gauges for water injection expansion force testing, and the other is used as a non-water injection earth pressure gauge for reference to monitor the pressure change caused by the self-weight stress of the surrounding rock;

[0009] b. A water injection system is arranged around each water injection test point, including a water injection pipe, a water absorbing sponge, a water supply tank and a control valve. The water injection pipe is connected to the water supply tank through the control valve and is wrapped around the soil pressure gauge used for water injection expansion force test. Fine sand is filled in the water injection pipe, and water injection holes are punched on the surface of the water injection pipe to inject water into the surrounding rock. The lower part of the water injection pipe is reserved outside the groove as a water outlet, and the water outlet is connected to a faucet with a water outlet valve to facilitate the control of water outlet and exhaust;

[0010] c. Backfill the groove with cement mortar, and after solidification, form a whole with the surrounding lining. Use the interaction between the tunnel lining and the surrounding rock to form a reaction force system to support and stabilize the test device;

[0011] d. After installation, first test the initial reading of the earth pressure gauge, then inject water into the water injection pipe through the water supply tank and the control valve to make the surrounding rock expand and deform after absorbing water, and monitor and record the earth pressure gauge reading for the in-situ expansion force test;

[0012] e. Compare and analyze the changes in the readings of the earth pressure gauge at the water injection test point and the non-water injection test point to evaluate the surrounding rock expansion force.

[0013] In a further technical solution, in step a, the specific installation process includes:

[0014] a1. Use an impact drill to dig a groove of 30×30 cm at the predetermined position of the tunnel lining, until the fresh surface of the surrounding rock is exposed;

[0015] a2. Use an impact drill to flatten the surface of the fresh rock, drill two water injection holes below the flattened part of the groove window, drive in two expansion screws to support the earth pressure gauge, and then use the same cement mortar as the tunnel lining to level the surface of the fresh rock;

[0016] a3. Drive two hook expansion screws on both sides of the middle position of the groove window, connect and tighten with 2mm iron wire, use a round wooden stick with a diameter of 5cm and a length slightly larger than the distance between the iron wire and the earth pressure gauge as a pressure rod, press the earth pressure gauge vertically on the leveled cement mortar, and support the earth pressure gauge and the tightened iron wire at both ends of the pressure rod respectively to ensure that the earth pressure gauge will not move during the installation process until the mortar solidifies and fixes the earth pressure gauge.

[0017] In a further technical solution, in step b, the number of the absorbent sponges is 8, which have the same thickness as the earth pressure gauge and are evenly arranged around the earth pressure gauge to provide support, fix the water injection pipe and maintain moisture around the earth pressure gauge.

[0018] In a further technical solution, in step b, the water injection pipe is ф10 mm, and 4 2 mm water injection holes are evenly drilled on the surface, and the water injection holes are located close to the upper half of the earth pressure gauge to facilitate uniform water seepage.

[0019] In a further technical solution, step b also includes: using cardboard of the same size as the groove to open a circular hole matching the soil pressure gauge, and sleeve it around the soil pressure gauge to fix the water-absorbing sponge and the water injection pipe.

[0020] In a further technical solution, step b also includes: laying a waterproof cloth slightly larger than the groove in front of the soil pressure gauge, and clamping the waterproof cloth with a 15×10mm PVC wire trough to prevent sliding, and then applying cement slurry mixed with a quick-setting agent around the groove window to enhance the waterproof effect.

[0021] In a further technical solution, in step c, the pressure rod fixing the earth pressure gauge is removed, a layer plate slightly larger than the groove window is prepared, the layer plate is fixed with the existing iron wire on the outside of the groove, and cement mortar with the same grade as the lining is poured into the groove. When pouring the cement mortar, an iron rod is used to tamp it, and the layer plate is vibrated in an impact hammer mode until slurry overflow occurs. When the groove is filled with mortar, the surface is smoothed and waited to solidify.

[0022] A device for testing the in-situ expansion force of expansion rock in a tunnel, used in the above-mentioned method for testing the in-situ expansion force of expansion rock in a tunnel, comprising:

[0023] The force measuring system includes at least three earth pressure gauges, two of which are used for water injection expansion force testing, and the other is used as a non-water injection earth pressure gauge for reference to monitor the pressure changes caused by the deadweight stress of the surrounding rock. All earth pressure gauges are connected to external reading devices through cables to record data in real time;

[0024] The water injection system includes a water injection pipe, a water absorbing sponge, a water supply tank and a control valve. The water injection pipe is connected to the water supply tank through the control valve. The water injection pipe is arranged around the soil pressure gauge used for water injection expansion force testing. The surface of the water injection pipe is provided with water injection holes so as to evenly inject water into the surrounding rock. The lower part of the water injection pipe is reserved outside the groove as a water outlet. The water outlet is connected to a faucet with a water outlet valve to facilitate the control of water outlet and exhaust.

[0025] The reaction force system is formed by the interaction between the tunnel lining and the surrounding rock. Grooves are excavated at the selected test points of the tunnel lining, and the force measuring system and water injection system are installed. The grooves are filled with cement mortar, which forms an integral structure with the tunnel lining after solidification, providing sufficient reaction force support for the earth pressure gauge to resist the expansion and deformation of the surrounding rock due to water absorption.

[0026] In a further technical solution, a cable protection box is also included to protect the reading connector of the earth pressure gauge cable to prevent it from being damaged and to ensure the continuity and accuracy of data reading.

[0027] In a further technical solution, it also includes cardboard and waterproof cloth. A circular hole matching the earth pressure gauge is opened on the cardboard, and the cardboard is arranged around the earth pressure gauge to fix the water-absorbing sponge and the water injection pipe. The waterproof cloth is slightly larger than the groove and is laid in front of the earth pressure gauge. The waterproof cloth is clamped with a 15×10mm PVC wire trough, and then cement slurry mixed with a quick-setting agent is applied around the groove window to enhance the waterproof effect.

[0028] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0029] True reflection of on-site conditions: By testing in the actual tunnel environment, the impact of multiple on-site factors on the expansion force, including geological structure, groundwater level, tunnel shape, etc., can be fully captured. This on-site testing method effectively avoids test errors caused by reduced sample size and simplified boundary conditions, thereby more truly reflecting the expansion force characteristics of the expansive rock under in-situ conditions, and the test cycle is short, providing reliable data support for the design and construction of tunnel projects.

[0030] Improve test accuracy: By directly installing a force measurement system in the tunnel lining and using an earth pressure gauge to monitor the expansion force changes of the surrounding rock in real time, the accuracy and reliability of the test can be greatly improved. In particular, by installing three earth pressure gauges at one test point, two of which are used for water injection expansion force testing and the other as a non-water injection earth pressure gauge for reference, the expansion force of the surrounding rock can be more accurately evaluated by comparing the reading changes of the water injection test earth pressure gauge and the non-water injection test earth pressure gauge.

[0031] Improve engineering quality and economic benefits: By accurately evaluating the expansion force of the surrounding rock, the expansion potential of the surrounding rock and its impact on the tunnel structure can be more accurately evaluated. This not only helps to optimize the size and strength design of the support structure, ensuring that the support system is neither excessive nor insufficient, thereby achieving a balance between the safety and economy of the tunnel project. In addition, accurate data support can also help the project team better predict and control potential risks during the construction process, reduce project costs, and improve overall economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The present invention will now be described by way of example with reference to the accompanying drawings, in which:

[0033] Figure 1 It is a schematic diagram of the plane layout of the test point soil pressure gauge of the present invention;

[0034] Figure 2It is a schematic diagram of the planar layout of a single water injection soil pressure gauge of the present invention;

[0035] Figure 3 It is a schematic cross-sectional diagram of the installation of a single water injection soil pressure gauge of the present invention.

[0036] Figure numerals: 1-tunnel lining, 2-non-water-injected soil pressure gauge, 3-water-injected soil pressure gauge, 4-cable, 5-water injection pipe, 6-cable protection box, 7-water supply tank, 8-water injection hole, 9-water-absorbing sponge, 10-water outlet valve, 11-surrounding rock, 12-cardboard, 13-waterproof cloth, 14-cement mortar. DETAILED DESCRIPTION

[0037] The following will be combined with the drawings in 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 only 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.

[0038] See also Figure 1-Figure 3 The present invention provides a method for testing the in-situ expansion force of expansion rock in a tunnel, comprising the following steps:

[0039] a. Select a test point on the tunnel lining 1, dig a groove and install a force measuring system, which includes three earth pressure gauges, two of which are used as water-injected earth pressure gauges 3 for water-injected expansion force testing, and the other is used as a non-water-injected earth pressure gauge 2 as a reference to monitor the pressure change caused by the self-weight stress of the surrounding rock 11;

[0040] The specific installation process includes:

[0041] a1. Use an impact drill to dig a groove of 30×30 cm at a predetermined position of the tunnel lining 1, until the fresh surface of the surrounding rock 11 is exposed;

[0042] a2. Use an impact drill to flatten the surface of the fresh rock, drill two water injection holes 8 below the flattened part of the groove window, drive in two expansion screws to support the earth pressure gauge, and then use the same cement mortar 14 as the tunnel lining 1 to level the surface of the fresh rock;

[0043] a3. Drive two hook expansion screws on both sides of the middle position of the groove window, and connect and tighten them with 2mm iron wire. Use a round wooden stick with a diameter of 5cm and a length slightly larger than the distance between the iron wire and the earth pressure gauge as a pressure rod, and press the earth pressure gauge vertically on the leveled cement mortar 14. The two ends of the pressure rod respectively support the earth pressure gauge and the tightened iron wire to ensure that the earth pressure gauge will not move during the installation process until the mortar solidifies and fixes the earth pressure gauge;

[0044] b. A water injection system is arranged around each water injection test point, including a water injection pipe 5, a water absorbing sponge 9, a water supply tank 7 and a control valve. The water injection pipe 5 is connected to the water supply tank 7 through the control valve and is wound around the soil pressure gauge used for water injection expansion force test. Fine sand is filled in the water injection pipe 5, and water injection holes 8 are punched on the surface of the water injection pipe 5 to inject water into the surrounding rock 11. The lower part of the water injection pipe 5 is reserved outside the groove as a water outlet, and the water outlet is connected to a faucet with a water outlet valve 10 to facilitate the control of water outlet and exhaust;

[0045] c. Backfill cement mortar 14 into the groove, and after solidification, form a whole with the surrounding lining, and use the interaction between the tunnel lining 1 and the surrounding rock 11 to form a reaction force system to support and stabilize the test device;

[0046] d. After installation, first test the initial reading of the earth pressure gauge, then inject water into the water injection pipe 5 through the water supply tank 7 and the control valve, so that the surrounding rock 11 will expand and deform after absorbing water, and monitor and record the earth pressure gauge reading for the in-situ expansion force test;

[0047] e. Compare and analyze the changes in the readings of the earth pressure gauge at the water injection test point and the non-water injection test point to evaluate the expansion force of the surrounding rock.

[0048] The present invention aims to accurately monitor the changes in the expansion force of expansive rock in situ by constructing a field testing system that is close to the actual tunnel construction and operation environment. This testing method combines a force measuring system with a water injection system, and the two work together to achieve dynamic and real-time measurement of the expansion force of the surrounding rock 11. Specifically, the force measuring system accurately captures the pressure response of the surrounding rock 11 during the water injection expansion process through an earth pressure gauge, while the water injection system simulates groundwater level changes or water seepage conditions to induce expansion deformation of the surrounding rock 11. This combined testing method ensures the authenticity and representativeness of the data, and provides strong data support for the design and construction of tunnel projects. Through this method, the following beneficial effects can be obtained:

[0049] True reflection of on-site conditions: By testing in the actual tunnel environment, the impact of multiple on-site factors on the expansion force, including geological structure, groundwater level, tunnel shape, etc., can be fully captured. This on-site testing method effectively avoids test errors caused by reduced sample size and simplified boundary conditions, thereby more truly reflecting the expansion force characteristics of the expansive rock under in-situ conditions, and the test cycle is short, providing reliable data support for the design and construction of tunnel projects.

[0050] Improve test accuracy: By directly installing a force measurement system in the tunnel lining 1 and using an earth pressure gauge to monitor the change in the expansion force of the surrounding rock 11 in real time, the accuracy and reliability of the test can be greatly improved. In particular, by installing three earth pressure gauges at one test point, two of which are used for water injection expansion force testing and the other as a non-water injection earth pressure gauge 2 for reference, the expansion force of the surrounding rock 11 can be more accurately evaluated by comparing the reading changes of the water injection test earth pressure gauge and the non-water injection test earth pressure gauge.

[0051] Improve engineering quality and economic benefits: By accurately evaluating the expansion force of the surrounding rock 11, the expansion potential of the surrounding rock 11 and its impact on the tunnel structure can be more accurately evaluated. This not only helps to optimize the size and strength design of the support structure, but also ensures that the support system is neither excessive nor insufficient, thereby achieving a balance between the safety and economy of the tunnel project. In addition, accurate data support can also help the project team better predict and control potential risks during the construction process, reduce project costs, and improve overall economic benefits.

[0052] In a specific embodiment, in step b, the number of the absorbent sponges 9 is 8, which have the same thickness as the earth pressure gauge and are evenly arranged around the earth pressure gauge to provide support, fix the water injection pipe 5 and maintain moisture around the earth pressure gauge.

[0053] The water-absorbing sponge 9 can not only efficiently absorb and retain the moisture around the earth pressure gauge, but also ensure that the surrounding rock 11 can continuously and evenly absorb moisture during the water injection process by evenly arranging the water-absorbing sponge 9 around the earth pressure gauge, thereby more accurately simulating the impact of actual groundwater level changes or water seepage conditions on the expansion force of the surrounding rock 11, and reducing measurement errors caused by uneven water distribution or differences in support conditions. This helps to improve the accuracy and reliability of the test results and provide more accurate data support for the design and construction of tunnel projects.

[0054] In a specific embodiment, in step b, the water injection pipe 5 is ф10 mm, and four 2 mm water injection holes 8 are evenly drilled on the surface, and the water injection holes 8 are located close to the upper part of the earth pressure gauge to facilitate uniform water seepage.

[0055] Through the injection holes 8 evenly distributed on the surface of the injection pipe 5, water can slowly and evenly penetrate into the surrounding rock 11, avoiding measurement errors caused by uneven water distribution. This uniform water seepage method is closer to the actual groundwater level changes or water seepage conditions, thereby improving the accuracy and reliability of the test. In addition, the position of the injection holes 8 is specially designed to be close to the upper half of the earth pressure gauge. Such a layout not only promotes the effective penetration of water into the vicinity of the earth pressure gauge, but also enables the earth pressure gauge to more directly and sensitively capture the pressure changes generated by the surrounding rock 11 during the water absorption and expansion process, thereby more accurately reflecting the pressure changes of the surrounding rock 11 during the water absorption and expansion process, ensuring that the test results can more truly reflect the behavioral characteristics of the surrounding rock 11 under specific conditions.

[0056] In a specific embodiment, step b further includes: using a cardboard 12 of the same size as the groove to open a circular hole matching the soil pressure gauge, and sleeved around the soil pressure gauge to fix the water-absorbing sponge 9 and the water injection pipe 5.

[0057] The cardboard 12 matches the size of the groove and can fit tightly in the groove. By opening a circular hole that matches the soil pressure gauge, the cardboard 12 can ensure the stability of the position of the soil pressure gauge during installation and facilitate installation. At the same time, it can effectively fix the surrounding absorbent sponge 9 and water injection pipe 5 to prevent them from shifting or deforming during the test, thereby providing a strong guarantee for the accuracy of the test results.

[0058] In a specific embodiment, step b also includes: laying a waterproof cloth 13 slightly larger than the groove in front of the soil pressure gauge, and clamping the waterproof cloth 13 with a 15×10mm PVC wire trough to prevent sliding, and then applying cement slurry mixed with a quick-setting agent around the groove window to enhance the waterproof effect.

[0059] A waterproof cloth 13 slightly larger than the groove is laid in front of the earth pressure gauge and clamped with a PVC wire trough to prevent sliding. This measure effectively constructs a waterproof barrier to prevent external moisture from infiltrating the test area without control, thereby ensuring the accuracy and controllability of the source of moisture during the test. In addition, cement paste mixed with a quick-setting agent is applied around the groove window, which not only enhances the sealing of the structure, but also accelerates the hardening process of cement through the action of the quick-setting agent, so that the waterproof layer can be formed faster and achieve the expected waterproof effect, thereby reducing the time spent waiting for the waterproof layer to dry during the test and improving the overall efficiency of the test.

[0060] In a specific implementation, in step c, the pressure rod for fixing the earth pressure gauge is removed, a layer plate slightly larger than the groove window is prepared, the layer plate is fixed by using the existing iron wire on the outside of the groove, and cement mortar 14 of the same grade as the lining is poured into the groove. When pouring the cement mortar 14, an iron rod is used to tamp it, and the layer plate is vibrated in an impact hammer mode until slurry overflow occurs. When the groove is filled with mortar, the surface is smoothed and waited to solidify.

[0061] During the pouring process of cement mortar 14, iron rods are used to tamp and the layer plate is vibrated by impact hammer mode until slurry overflow occurs. This step ensures that the cement mortar 14 can fully fill every corner of the groove and improves the density and uniformity of the filling. In addition, by pouring cement mortar 14 with the same grade as the lining, it is ensured that the performance of the filling material matches the surrounding structure, which helps to maintain the strength and stability of the overall structure.

[0062] The present invention also provides a device for testing the in-situ expansion force of expansion rock in a tunnel, which is used in the above-mentioned method for testing the in-situ expansion force of expansion rock in a tunnel, comprising:

[0063] The force measuring system includes three earth pressure gauges, two of which are used for water injection expansion force testing, and the other one is used as a non-water injection earth pressure gauge 2, which is used as a reference to monitor the pressure changes caused by the self-weight stress of the surrounding rock 11. All earth pressure gauges are connected to external reading equipment through cables 4 to record data in real time;

[0064] The water injection system includes a water injection pipe 5, a water absorbing sponge 9, a water supply tank 7 and a control valve. The water injection pipe 5 is connected to the water supply tank 7 through the control valve. The water injection pipe 5 is arranged around the soil pressure gauge used for water injection expansion force testing. The surface of the water injection pipe 5 is provided with water injection holes 8 so as to evenly inject water into the surrounding rock 11. The lower part of the water injection pipe 5 is reserved outside the groove as a water outlet. The water outlet is connected to a faucet with a water outlet valve 10 to facilitate the control of water outlet and exhaust;

[0065] The reaction force system is formed by the interaction between the tunnel lining 1 and the surrounding rock 11. A groove is excavated at the selected test point of the tunnel lining 1, and a force measuring system and a water injection system are installed. The groove is filled with cement mortar 14, which forms an integral structure with the tunnel lining 1 after solidification, providing sufficient reaction force support for the earth pressure gauge to resist the expansion deformation of the surrounding rock 11 caused by water absorption.

[0066] By installing the device in the actual tunnel environment according to the above method, the accuracy and reliability of the test process are ensured. In actual operation, in order to ensure that the device can work stably and accurately record the changes in the expansion force of the swelling rock under in-situ conditions, the following measures can also be taken:

[0067] Careful groove excavation: When excavating grooves on the tunnel lining 1, strictly control the size and shape of the grooves to ensure that they meet the design requirements. At the same time, pay attention to protecting the surrounding rock 11 from damage, so as not to affect the accuracy of the test results.

[0068] Securely mount the system: When installing the force measurement system and water injection system, take additional fixing measures, such as using a more solid support structure or adding fixing points, to enhance the stability and safety of the system, thereby reducing measurement errors caused by system shaking or displacement.

[0069] Strengthen monitoring and recording: After the installation is completed, strengthen the monitoring and recording of the test area. In addition to real-time recording of the earth pressure gauge data, regularly check the stability and safety of the device to promptly identify and deal with potential problems. At the same time, establish a detailed test record file to provide strong support for subsequent data analysis and engineering applications.

[0070] In a specific embodiment, a cable protection box 6 is also included to protect the reading connector of the earth pressure gauge cable 4 to prevent it from being damaged and to ensure the continuity and accuracy of data reading.

[0071] The main function of the cable protection box 6 is to provide a solid protective layer for the reading connector of the earth pressure gauge cable 4, reducing the equipment damage and replacement requirements caused by environmental factors, effectively preventing it from being damaged in the harsh tunnel environment, and extending the service life of the cable 4. It not only ensures the continuity and accuracy of data reading, but also improves the stability and reliability of the entire test system.

[0072] In a specific embodiment, it also includes cardboard 12 and waterproof cloth 13. The cardboard 12 is provided with a circular hole matching the soil pressure gauge and is sleeved around the soil pressure gauge to fix the water-absorbing sponge 9 and the water injection pipe 5. The waterproof cloth 13 is slightly larger than the groove and is laid in front of the soil pressure gauge. The waterproof cloth 13 is clamped with a 15×10mm PVC wire trough, and then cement slurry mixed with a quick-setting agent is applied around the groove window to enhance the waterproof effect.

[0073] The cardboard 12 fixes the water-absorbing sponge 9 and the water injection pipe 5, ensuring that the water can act evenly on the surrounding rock 11 in a predetermined manner, thereby improving the accuracy of the in-situ expansion force test of the swelling rock. The waterproof cloth 13 is laid in front of the soil pressure gauge to form an effective waterproof barrier. The waterproof cloth 13 is clamped by a 15×10mm PVC wire groove, which not only enhances its stability, but also ensures that the waterproof cloth 13 can fit tightly to the edge of the groove, preventing external moisture from infiltrating the test area uncontrolled. This measure ensures the accuracy and controllability of the source of moisture during the test and improves the reliability of the test data.

[0074] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made using the contents of the present invention specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A method for testing the in-situ expansion force of expansive rock in a tunnel, characterized in that: The following steps are involved: a. selecting a test point on the tunnel lining (1), excavating a groove and installing a force measuring system, wherein the force measuring system comprises at least three soil pressure gauges, two of which are used as water injection soil pressure gauges (3) for water injection expansion force testing, and the other is used as a non-water injection soil pressure gauge (2) for reference, for monitoring the pressure change caused by the self-weight stress of the surrounding rock (11); b. Arrange a water injection system around each water injection test point, including a water injection pipe (5), a water absorbing sponge (9), a water supply tank (7) and a control valve. The water injection pipe (5) is connected to the water supply tank (7) through the control valve and is wound around the soil pressure gauge used for water injection expansion force testing. Fine sand is filled in the water injection pipe (5), and a water injection hole (8) is punched on the surface of the water injection pipe (5) to inject water into the surrounding rock (11). The lower part of the water injection pipe (5) is reserved outside the groove as a water outlet, and the water outlet is connected to a faucet with a water outlet valve (10) to facilitate the control of water outlet and exhaust; c. Backfill cement mortar (14) into the groove, and after solidification, form a whole with the surrounding lining, and utilize the interaction between the tunnel lining (1) and the surrounding rock (11) to form a reaction force system to support and stabilize the test device; d. After the installation is completed, the initial reading of the earth pressure gauge is tested first, and then water is injected into the water injection pipe (5) through the water supply tank (7) and the control valve to cause the surrounding rock (11) to expand and deform after absorbing water, and the earth pressure gauge reading for the in-situ expansion force test is monitored and recorded; e. Compare and analyze the changes in the readings of the earth pressure gauge at the water injection test point and the non-water injection test point to evaluate the expansion force of the surrounding rock (11).

2. A method for testing the in-situ expansion force of swelling rock in a tunnel according to claim 1, characterized in that: In step a, the specific installation process includes: a1. Use an impact drill to dig a groove of 30×30 cm at a predetermined position of the tunnel lining (1), until the fresh surface of the surrounding rock (11) is exposed; a2. Use an impact drill to flatten the surface of the fresh rock, drill two water injection holes (8) below the flattened part of the groove window, drive in two expansion screws to support the earth pressure gauge, and then use the same cement mortar (14) as the tunnel lining (1) to level the surface of the fresh rock; a3. Drive two hook expansion screws into the middle of the groove window on both sides and connect them with 2mm iron wire to tighten them. Use a round wooden stick with a diameter of 5cm and a length slightly larger than the distance between the iron wire and the earth pressure gauge as a pressure rod to vertically press the earth pressure gauge onto the leveled cement mortar (14). The two ends of the pressure rod respectively support the earth pressure gauge and the tightened iron wire to ensure that the earth pressure gauge will not move during the installation process until the mortar solidifies and fixes the earth pressure gauge.

3. A method for testing the in-situ expansion force of swelling rock in a tunnel according to claim 1, characterized in that: In step b, the number of the water-absorbing sponges (9) is 8, which have the same thickness as the earth pressure gauge and are evenly arranged around the earth pressure gauge to provide support, fix the water injection pipe (5) and maintain moisture around the earth pressure gauge.

4. A method for testing the in-situ expansion force of swelling rock in a tunnel according to claim 1, characterized in that: In step b, the water injection pipe (5) is ф10 mm, and four 2 mm water injection holes (8) are evenly drilled on the surface, and the water injection holes (8) are located close to the upper part of the soil pressure gauge to facilitate uniform water seepage.

5. A method for testing the in-situ expansion force of swelling rock in a tunnel according to claim 1, characterized in that: Step b also includes: using a cardboard (12) of the same size as the groove to open a circular hole matching the soil pressure gauge, and sleeve it around the soil pressure gauge to fix the water-absorbing sponge (9) and the water injection pipe (5).

6. A method for testing the in-situ expansion force of swelling rock in a tunnel according to claim 1, characterized in that: Step b also includes: laying a waterproof cloth (13) slightly larger than the groove in front of the soil pressure gauge, and clamping the waterproof cloth (13) with a 15×10mm PVC wire trough to prevent sliding, and then applying cement slurry mixed with a quick-setting agent around the groove window to enhance the waterproof effect.

7. A method for testing the in-situ expansion force of swelling rock in a tunnel according to claim 2, characterized in that: In step c, the pressure rod for fixing the earth pressure gauge is removed, and a layer plate slightly larger than the groove window is prepared. The layer plate is fixed by using the iron wire on the outside of the groove, and cement mortar (14) of the same grade as the lining is poured into the groove. When pouring the cement mortar (14), an iron rod is used to tamp it, and the layer plate is vibrated in an impact hammer mode until slurry overflow occurs. When the groove is filled with mortar, the surface is smoothed and waited for it to solidify.

8. A device for testing the in-situ expansion force of expansion rock in a tunnel, used in the method for testing the in-situ expansion force of expansion rock in a tunnel as claimed in any one of claims 1 to 7, characterized in that: include: A force measuring system, comprising at least three earth pressure gauges, two of which are used for water injection expansion force testing, and the other is used as a non-water injection earth pressure gauge (2) for reference, and is used to monitor the pressure change caused by the deadweight stress of the surrounding rock (11). All earth pressure gauges are connected to an external reading device through a cable (4) so ​​as to record data in real time; The water injection system comprises a water injection pipe (5), a water absorbing sponge (9), a water supply tank (7) and a control valve. The water injection pipe (5) is connected to the water supply tank (7) through the control valve. The water injection pipe (5) is arranged around a soil pressure gauge for water injection expansion force testing. The surface of the water injection pipe (5) is provided with water injection holes (8) so as to uniformly inject water into the surrounding rock (11). The lower part of the water injection pipe (5) is reserved outside the groove as a water outlet. The water outlet is connected to a faucet with a water outlet valve (10) to facilitate the control of water outlet and exhaust. The reaction force system is formed by the interaction between the tunnel lining (1) and the surrounding rock (11). A groove is excavated at a selected test point of the tunnel lining (1), and a force measuring system and a water injection system are installed. The groove is filled with cement mortar (14), which forms an integral structure with the tunnel lining (1) after solidification, providing sufficient reaction force support for the earth pressure gauge to resist the expansion deformation of the surrounding rock (11) caused by water absorption.

9. The device for testing the in-situ expansion force of expansion rock in a tunnel according to claim 8, characterized in that: It also includes a cable protection box (6) for protecting the reading connector of the earth pressure gauge cable (4) to prevent it from being damaged and to ensure the continuity and accuracy of data reading.

10. The device for testing the in-situ expansion force of expansion rock in a tunnel according to claim 8, characterized in that: It also includes cardboard (12) and waterproof cloth (13). The cardboard (12) is provided with a circular hole matching the earth pressure gauge and is sleeved around the earth pressure gauge to fix the water-absorbing sponge (9) and the water injection pipe (5). The waterproof cloth (13) is slightly larger than the groove and is laid in front of the earth pressure gauge. The waterproof cloth (13) is clamped with a 15×10mm PVC wire trough. Then, cement slurry mixed with a quick-setting agent is applied around the groove window to enhance the waterproof effect.

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