An experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel

Abstract

The present invention discloses an experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel, comprising the following steps: conducting an experiment using an experimental device; starting a jack for preloading, and stopping the preloading after the first curved plate is in close contact with a transparent ribbed multi-arch tunnel model; starting the jack to pressurize to a preset load, and recording the values ​​displayed by the dial gauge and the strain gauge at this time; adjusting the launch angle of a rockfall-simulating impact system, and using a projectile of the rockfall-simulating impact system to impact the lining structure of the transparent ribbed multi-arch tunnel model, and recording the values ​​displayed by the dial gauge and the strain gauge at this time; and recording the initial velocity of the projectile when it is launched, the final velocity before contacting the transparent ribbed multi-arch tunnel model, and the motion trajectory of the projectile by a high-speed camera. The present invention has the advantages of: using a rockfall-simulating impact system to launch a small ball to simulate rockfall to impact a transparent ribbed multi-arch tunnel under a load state, and then obtaining the impact resistance of the transparent ribbed multi-arch tunnel lining structure.

Description

Technical Field

[0001] The invention relates to the technical field of a transparent rib-type multi-arch tunnel, in particular to an experimental method for studying the influence of rockfall impact on a transparent rib-type multi-arch tunnel. Background Art

[0002] The transparent ribbed arch tunnel that has emerged in recent years has contributed a new solution to the construction of arch tunnels with its unique design concept. The transparent ribbed arch tunnel is a shallow buried biased tunnel built next to the mountain. The structure adopts a double arch structure, and the outer tunnel is a rib beam structure. It has good ventilation and lighting performance, and effectively reduces the damage to the hillside vegetation; a rockfall retaining wall is set at the top of the outer tunnel arch to prevent the rocks sliding down the surface of the tunnel top slope from falling into the outer tunnel and affecting the normal operation of the tunnel. At present, most scholars have studied the stability of the top slope of the transparent ribbed arch tunnel, but there is a lack of research on the impact of rockfall on the transparent ribbed arch tunnel. It is unclear how large and how fast the rockfall retaining wall can withstand the impact of rockfall, and the ability of the lining structure at the arch position of the outer tunnel to resist the impact of rockfall. Once the rockfall breaks through the rockfall retaining wall or destroys the main structure of the tunnel, people's lives and property will be greatly threatened. Therefore, a model experiment is urgently needed to study the impact of rockfalls of different sizes and speeds on the transparent rib-type arch tunnel, and then reveal the ability of the lining structure of the transparent rib-type arch tunnel to resist rockfall impact. Summary of the invention

[0003] The purpose of the present invention is to provide an experimental method for studying the influence of rockfall impact on a transparent ribbed arch tunnel in accordance with the above-mentioned deficiencies of the prior art. By setting a reaction system, a loading system, a transparent ribbed arch tunnel model, a rockfall impact simulation system and a measurement system, the impact of rockfall on the transparent ribbed arch tunnel under load can be simulated. By analyzing the difference in strain and normal deformation of the lining structure before and after the rockfall impact, the deformation and damage and failure laws of the lining structure of the transparent ribbed arch tunnel under the rockfall impact are summarized, and the impact resistance of the lining structure of the transparent ribbed arch tunnel is obtained.

[0004] The purpose of the present invention is achieved by the following technical solutions:

[0005] An experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel, characterized in that the experimental method comprises the following steps:

[0006] (S1) Conducting an experiment using an experimental device; wherein the experimental device includes a reaction system, a loading system, a transparent rib-type arch tunnel model, a rockfall impact simulation system, and a measurement system; the reaction system is composed of a reaction wall and a reaction frame embedded in the reaction wall; the transparent rib-type arch tunnel model is installed in the space formed by the reaction frame through the loading system; the loading system includes a plurality of jacks installed on the inner surface of the reaction frame, the front end of the piston rod of the jack is connected to a pressure sensor, and the pressure sensor is connected to the first curved plate through a first spiral cylindrical spring. The curvature of the first curved plate is consistent with the curvature of the transparent rib-type multi-arch tunnel model; the rockfall impact simulation system is installed on the top of the inner surface of the reaction frame; the measurement system includes a micrometer, a strain gauge, a strain meter and a high-speed camera, the micrometer is arranged on the inner surface of the lining structure, the top of the middle wall and the bottom of the middle wall of the transparent rib-type multi-arch tunnel model, the strain gauge is attached to the inner and outer surfaces of the lining structure, the top of the middle wall and the bottom of the middle wall of the transparent rib-type multi-arch tunnel model, the high-speed camera is set up in front of the reaction system, and the strain meter is connected to the strain gauge for communication;

[0007] (S2) starting the jack for preloading until the first curved plate is in close contact with the transparent rib-type multi-arch tunnel model and then stopping the preloading; starting the jack to pressurize to a preset load, and recording the values ​​displayed by the dial gauge and the strain gauge at this time, so as to study the normal displacement and strain value generated on the surface of the lining structure of the transparent rib-type multi-arch tunnel model when the preset load is applied;

[0008] (S3) adjusting the launching angle of the simulated rockfall impact system, using the projectile of the simulated rockfall impact system to impact the lining structure of the transparent rib-type arch tunnel model, recording the values ​​displayed by the micrometer and the strain gauge at this time, so as to study the normal displacement and strain value generated on the surface of the lining structure when the transparent rib-type arch tunnel model is impacted under a loaded state; recording the initial velocity of the projectile when it is fired, the final velocity before contacting the transparent rib-type arch tunnel model, and the movement trajectory of the projectile by the high-speed camera.

[0009] The simulated rockfall impact system includes a launching device and a hollow iron ball. The launching device includes a launching tube, an electromagnet fixed at the rear end of the launching tube, and a second helical cylindrical spring installed in the launching tube. The two ends of the second helical cylindrical spring are respectively connected to the electromagnet and the hollow iron ball, and the rear end of the electromagnet is connected to the reaction frame through a ball joint.

[0010] The ball joint includes a spherical hole opened on the reaction frame and an iron ball matched with the spherical hole. The iron ball is installed in the spherical hole and can move in the spherical hole. A bolt is provided on the outside of the spherical hole, and the position of the iron ball in the spherical hole is fixed by tightening the bolt.

[0011] The bottom of the inner surface of the reaction frame is connected to the second curved plate through a third spiral cylindrical spring, and the curvature of the second curved plate is consistent with the curvature of the transparent rib-type multi-arch tunnel model.

[0012] The reaction frame is provided with aluminum alloy pads on the left and bottom of the enlarged foundation of the transparent rib type arch tunnel model, respectively. The aluminum alloy pads are connected to the third curved plate through the fourth spiral cylindrical spring. The curvature of the third curved plate is consistent with the curvature of the enlarged foundation of the transparent rib type arch tunnel model.

[0013] The jacks are respectively arranged on the left side, the top and the right side of the inner surface of the reaction frame.

[0014] The advantages of the present invention are: easy operation and convenient observation. The rockfall impact system can be used to simulate the impact of rockfall on a transparent ribbed arch tunnel under load by launching small balls. The strain and normal deformation of the lining structure before and after the rockfall impact are analyzed, and the deformation and damage and failure laws of the lining structure of the transparent ribbed arch tunnel under the rockfall impact are summarized, and the impact resistance of the lining structure of the transparent ribbed arch tunnel is obtained. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of the overall structure of the experimental device of the present invention;

[0016] Figure 2 for Figure 1 The enlarged schematic diagram of point A in the middle;

[0017] Figure 3 It is a schematic diagram of a transparent rib-type multi-arch tunnel model of the present invention;

[0018] Figure 4 It is the arrangement diagram of the micrometer of the present invention;

[0019] Figure 5 is a layout diagram of the strain gauge of the present invention;

[0020] Figure 6 is a front view of the reaction force system of the present invention;

[0021] Figure 7 for Figure 6 The enlarged schematic diagram of point B in the middle;

[0022] Figure 8It is a schematic diagram of the rockfall impact simulation system of the present invention. DETAILED DESCRIPTION

[0023] The features of the present invention and other related features are further described in detail below through embodiments in conjunction with the accompanying drawings to facilitate understanding by those skilled in the art:

[0024] like Figure 1-8 As shown in the figure, the marks are respectively represented as: reaction frame 1, reaction wall 2, aluminum alloy pad 3, jack 4, pressure sensor 5, first spiral cylindrical spring 6, first curved plate 7, transparent rib-type arch tunnel model 8, micrometer 9, strain gauge 10, second curved plate 11, launching tube 12, second spiral cylindrical spring 13, hollow iron ball 14, electromagnet 15, iron ball 16, spherical small hole 17, bolt 18, third spiral cylindrical spring 19, fourth spiral cylindrical spring 20, third curved plate 21, jack loading force F1-F8, gear position g1-g5.

[0025] Example: Figure 1-8 As shown, this embodiment relates to an experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel, and the construction method thereof comprises the following steps:

[0026] (S1) Conducting experiments using an experimental device. The experimental device includes a reaction force system, a loading system, a transparent ribbed arch tunnel model 8, a rockfall impact simulation system, and a measurement system, such as Figure 1 and Figure 6 As shown, the reaction system consists of a reaction wall 2 and a reaction frame 1 embedded in the reaction wall 2. The reaction wall 2 is cast by concrete, and the reaction frame 1 is welded by bending aluminum alloy plates. When bending the aluminum alloy plates, the curvature is ensured to be the same as the curvature of the tunnel lining structure. Since there are angles at the top and bottom of the wall of the reaction frame 1, in order to avoid stress concentration and damage during the loading process of the reaction frame 1, these two parts are locally thickened. Figure 1 , Figure 3 and Figure 6 As shown, the transparent ribbed arch tunnel model 8 is installed in the space formed by the reaction frame 1 through the loading system. In this embodiment, the ribbed beam section lining of the prototype tunnel is scaled down at a ratio of 1:20 to obtain the transparent ribbed arch tunnel model 8.

[0027] like Figure 1As shown, the loading system includes a plurality of jacks 4 installed on the inner surface of the reaction frame 1. The jacks 4 are respectively arranged on the left side, the top and the right side of the inner surface of the reaction frame 1. The front end of the piston rod of the jack 4 is connected with a pressure sensor 5. The pressure sensor 5 is connected to the first curved plate 7 through a first spiral cylindrical spring 6. The curvature of the first curved plate 7 is consistent with the curvature of the transparent rib-type arch tunnel model 8. In this embodiment, the number of the jacks 4, the pressure sensors 5, the first helical cylindrical springs 6 and the first curved plates 7 are all 8, wherein one first curved plate 7 is respectively provided at the lower left part and the upper right part of the left lining structure of the transparent rib type arch tunnel model 8, one first curved plate 7 is provided at the upper part of the middle wall of the transparent rib type arch tunnel model 8, and one, one, one and two first curved plates 7 are respectively provided at the upper left part, the upper part, the upper right part and the right part of the right lining structure of the transparent rib type arch tunnel model 8. The jacks 4 work independently and can apply 8 loading forces F1-F8 to the transparent rib type arch tunnel model 8. The bottom of the inner surface of the reaction frame 1 is connected to the second curved plate 11 through the third helical cylindrical spring 19. The curvature of the second curved plate 11 is consistent with the curvature of the transparent rib type arch tunnel model 8. In this embodiment, the second curved plate 11 is closely connected to the bottom of the transparent rib type arch tunnel model 8 through the third helical cylindrical spring 19 to support the bottom of the transparent rib type arch tunnel model 8. In addition, the number of second curved plates 11 is 11, and the left lining structure, right lining structure and middle wall bottom of the transparent rib type arch tunnel model 8 are respectively provided with 5, 5 and 1. In order to ensure that the active pressurizing direction of the jack 4 and the direction of the spring simulating the stratum resistance are consistent with the actual situation, an aluminum alloy pad 3 is arranged on the left and bottom of the reaction frame 1 at the enlarged foundation of the transparent rib type arch tunnel model 8. The aluminum alloy pad 3 is connected to the third curved plate 21 through the fourth helical cylindrical spring 20. The curvature of the third curved plate 21 is consistent with the curvature of the enlarged foundation of the transparent rib type arch tunnel model 8. In this embodiment, the fourth helical cylindrical spring 20 can make the third curved plate 21 close to the enlarged foundation of the transparent rib type arch tunnel model 8.

[0028] like Figure 1 , Figure 2 , Figure 6 , Figure 7 as well as Figure 8As shown, the simulated rockfall impact system is installed on the top of the inner surface of the reaction frame 1. The simulated rockfall impact system consists of a launching device and a hollow iron ball 14. The launching device can adjust the angle and initial velocity of the hollow iron ball 14 when it is shot out. The hollow iron ball 14 is used to simulate rockfall. The launch device includes a launch tube 12 (a transparent acrylic hollow tube in this embodiment), an electromagnet 15 fixed at the rear end of the launch tube 12, and a second helical cylindrical spring 13 installed in the launch tube 12. The two ends of the second helical cylindrical spring 13 are respectively connected to the electromagnet 15 and the hollow iron ball 14. The outer diameter of the second helical cylindrical spring 13 is slightly smaller than the inner diameter of the launch tube 12 and the length is slightly shorter than the launch tube 12. The rear end of the electromagnet 15 is connected to the reaction frame 1 through a ball joint. The ball joint includes a spherical hole 17 opened on the reaction frame 1 and an iron ball 16 adapted to the spherical hole 17. The iron ball 16 is installed in the spherical hole 17 and can move in the spherical hole 17. A bolt 18 is provided on the outside of the spherical hole 17. By tightening the bolt 18, the position of the iron ball 16 in the spherical hole 17 is fixed. The side of the launch tube 12 is provided with scale lines corresponding to different gears. In this embodiment, a total of 5 gears g1-g5 are provided. When the electromagnet 15 is powered on, the hollow iron ball 14 will move toward the closed end (tail end) of the launch tube 12 due to the attraction of magnetic force, thereby compressing the second spiral cylindrical spring 13. The magnitude of the magnetic force of the electromagnet 15 is related to the magnitude of the input current, and the compression amount of the second spiral cylindrical spring 13 also changes accordingly. When the power supply of the electromagnet 15 is cut off, the elastic potential energy generated by the compression of the second spiral cylindrical spring 13 is converted into the kinetic energy of the hollow iron ball 14, thereby ejecting the hollow iron ball 14 out of the launch tube 12. The hollow iron ball 14 stops at 5 gears corresponding to different scale lines due to the magnetic attraction generated by the electromagnet 15 when the input current is different. The speed of the hollow iron ball 14 leaving the tube mouth of the launch tube 12 corresponding to the g1 gear is the smallest, and the speed of the hollow iron ball 14 leaving the tube mouth of the launch tube 12 corresponding to the g5 gear is the largest. An iron ball 16 is fixed to the rear side of the electromagnet 15, and a layer of vaseline is applied to the outer surface of the iron ball 16 to reduce the friction between the iron ball 16 and the spherical hole 17. Then the entire rockfall impact simulation system is installed on the reaction frame 1 with a preset spherical hole 17 to form a ball joint. When the bolt 18 outside the spherical hole 17 is tightened, the launching device cannot rotate. When the bolt 18 outside the spherical hole 17 is loosened, the launching device can adjust the launching angle at will.

[0029] like Figure 1 , Figure 4 and Figure 5As shown, the measurement system includes a micrometer 9, a strain gauge 10 (a resistance strain gauge in this embodiment), a strain meter and a high-speed camera. The micrometer 9 is arranged on the inner surface of the lining structure, the top of the middle wall and the bottom of the middle wall of the transparent rib-type multi-arch tunnel model 8. The strain gauge 10 is attached to the inner and outer surfaces of the lining structure, the top of the middle wall and the bottom of the middle wall of the transparent rib-type multi-arch tunnel model 8. The high-speed camera is set up in front of the reaction system, and the strain meter is connected to the strain gauge 10 for communication. In this embodiment, the number of micrometers 9 and strain gauges 10 is 25 and 76 respectively, and the specific arrangement is as follows: Figure 4 and Figure 5 shown.

[0030] (S2) starting the jack 4 for preloading, and stopping the preloading after the first curved plate 7 is in close contact with the transparent rib-type multi-arch tunnel model 8; starting the jack 4 to pressurize to a preset load, and recording the values ​​displayed by the dial gauge 9 and the strain gauge at this time, so as to study the normal displacement and strain value generated on the surface of the lining structure of the transparent rib-type multi-arch tunnel model 8 when the preset load is applied.

[0031] (S3) Loosen the bolt 18 so that the launch device can adjust the launch angle. After selecting the launch angle of the launch device, tighten the bolt 18 to fix the launch angle. Then, energize the electromagnet 15, and then put the hollow iron ball 14 into the launch tube 12 from the open end of the launch tube 12. The hollow iron ball 14 is attracted by the magnetic force generated by the electromagnet 15, thereby compressing the second spiral cylindrical spring 13. By adjusting the magnitude of the input current of the electromagnet 15, the initial velocity of the hollow iron ball 14 leaving the launch tube 12 is changed. After the power supply of the electromagnet is cut off, the magnetic force of the electromagnet 15 disappears, and the hollow iron ball 14 is ejected from the launch tube 12 under the action of the elastic force of the second spiral cylindrical spring 13. When the hollow iron ball 14 is ejected from the launch tube 12 and falls onto the lining structure of the transparent ribbed multiple-arch tunnel model 8, the values ​​displayed by the micrometer 9 and the strain gauge are recorded at this moment to study the normal displacement and strain value generated on the surface of the lining structure when the transparent ribbed multiple-arch tunnel model 8 is impacted by the hollow iron ball 14 under load; and the initial velocity of the hollow iron ball 14 when it leaves the launch tube 12, the final velocity before contacting the transparent ribbed multiple-arch tunnel model 8, and the movement trajectory of the hollow iron ball 14 in this impact experiment are recorded by a high-speed camera.

[0032] This embodiment also has the following beneficial effects: it is easy to operate and observe, and can simulate the impact of falling rocks on a transparent ribbed arch tunnel under load by launching small balls through the imitation rockfall impact system. By analyzing the strain and normal deformation differences of the lining structure before and after the rockfall impact, the deformation and damage laws of the lining structure of the transparent ribbed arch tunnel when it is hit by falling rocks are summarized, and the impact resistance of the lining structure of the transparent ribbed arch tunnel is obtained.

[0033] Although the above embodiments have described in detail the concepts and embodiments of the present invention with reference to the accompanying drawings, ordinary technicians in this field can recognize that various improvements and changes can still be made to the present invention without departing from the scope of the claims, so they are not described one by one here.

Claims

1. An experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel, characterized in that: The experimental method comprises the following steps: (S1) Conducting an experiment using an experimental device; wherein the experimental device includes a reaction system, a loading system, a transparent rib-type arch tunnel model, a rockfall impact simulation system, and a measurement system; the reaction system is composed of a reaction wall and a reaction frame embedded in the reaction wall; the transparent rib-type arch tunnel model is installed in the space formed by the reaction frame through the loading system; the loading system includes a plurality of jacks installed on the inner surface of the reaction frame, the front end of the piston rod of the jack is connected to a pressure sensor, and the pressure sensor is connected to the first curved plate through a first spiral cylindrical spring. The curvature of the first curved plate is consistent with the curvature of the transparent rib-type multi-arch tunnel model; the rockfall impact simulation system is installed on the top of the inner surface of the reaction frame; the measurement system includes a micrometer, a strain gauge, a strain meter and a high-speed camera, the micrometer is arranged on the inner surface of the lining structure, the top of the middle wall and the bottom of the middle wall of the transparent rib-type multi-arch tunnel model, the strain gauge is attached to the inner and outer surfaces of the lining structure, the top of the middle wall and the bottom of the middle wall of the transparent rib-type multi-arch tunnel model, the high-speed camera is set up in front of the reaction system, and the strain meter is connected to the strain gauge for communication; (S2) starting the jack for preloading until the first curved plate is in close contact with the transparent rib-type multi-arch tunnel model and then stopping the preloading; starting the jack to pressurize to a preset load, and recording the values ​​displayed by the dial gauge and the strain gauge at this time, so as to study the normal displacement and strain value generated on the surface of the lining structure of the transparent rib-type multi-arch tunnel model when the preset load is applied; (S3) adjusting the launching angle of the simulated rockfall impact system, using the projectile of the simulated rockfall impact system to impact the lining structure of the transparent rib-type arch tunnel model, recording the values ​​displayed by the micrometer and the strain gauge at this time, so as to study the normal displacement and strain value generated on the surface of the lining structure when the transparent rib-type arch tunnel model is impacted under a loaded state; recording the initial velocity of the projectile when it is fired, the final velocity before contacting the transparent rib-type arch tunnel model, and the movement trajectory of the projectile by the high-speed camera.

2. The experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel as claimed in claim 1, characterized in that: The simulated rockfall impact system includes a launching device and a hollow iron ball. The launching device includes a launching tube, an electromagnet fixed at the rear end of the launching tube, and a second helical cylindrical spring installed in the launching tube. The two ends of the second helical cylindrical spring are respectively connected to the electromagnet and the hollow iron ball, and the rear end of the electromagnet is connected to the reaction frame through a ball joint.

3. The experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel as claimed in claim 2, characterized in that: The ball joint includes a spherical hole opened on the reaction frame and an iron ball matched with the spherical hole. The iron ball is installed in the spherical hole and can move in the spherical hole. A bolt is provided on the outside of the spherical hole, and the position of the iron ball in the spherical hole is fixed by tightening the bolt.

4. The experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel as claimed in claim 1, characterized in that: The bottom of the inner surface of the reaction frame is connected to the second curved plate through a third spiral cylindrical spring, and the curvature of the second curved plate is consistent with the curvature of the transparent rib-type multi-arch tunnel model.

5. The experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel as claimed in claim 1, characterized in that: The reaction frame is provided with aluminum alloy pads on the left and bottom of the enlarged foundation of the transparent rib type arch tunnel model, respectively. The aluminum alloy pads are connected to the third curved plate through the fourth spiral cylindrical spring. The curvature of the third curved plate is consistent with the curvature of the enlarged foundation of the transparent rib type arch tunnel model.

6. The experimental method for studying the impact of rockfall on a transparent ribbed multi-arch tunnel as claimed in claim 1, characterized in that: The jacks are respectively arranged on the left side, the top and the right side of the inner surface of the reaction frame.

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