A method for measuring internal displacement of surrounding rock of tunnel vault

Abstract

The application discloses a kind of tunnel vault surrounding rock internal displacement measurement methods, including drilling in the surrounding rock of vault, single-point displacement meter is fixed on mounting bracket;Mounting bracket includes protective cover, connecting cylinder and measuring rod, the upper end of measuring rod is fixed in the interior of surrounding rock by resin anchoring agent;Connecting cylinder lower part is solidly connected with piston rod, so that anchor point, measuring rod and piston rod are coupled as a whole;Initial support shotcrete is made on the surface of surrounding rock, so that protective cover, solenoid coil and initial support shotcrete are solid as a whole;Solenoid coil is connected to external reading instrument by wire, and displacement parameter in the interior of vault surrounding rock is collected by reading instrument.The application solves the problem of anchor head anchoring difficulty and displacement meter solenoid coil difficult to fix when inductance frequency modulation type single-point displacement meter is used to measure the displacement in the interior of vault surrounding rock, and can ensure the reliability of inductance frequency modulation type single-point displacement meter installation and the accuracy of measurement data.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of tunnel and underground engineering testing technology, and particularly relates to a method for measuring internal displacement of surrounding rock at a tunnel vault. BACKGROUND

[0002] The internal displacement of surrounding rock is an important indicator for objectively reflecting the loose range of rock mass and the stability of surrounding rock, and is an important basis for optimizing support parameters such as anchor rods and anchor cables. Single-point displacement meters are widely used in the measurement of internal displacement of surrounding rock in tunnels and underground engineering, and have various types such as vibrating string, fiber grating, and inductance frequency modulation.

[0003] The inductance frequency modulation type single-point displacement meter is designed based on the inductance magnetic flux frequency modulation principle. The magnetically permeable piston rod fixed to the pull rod is inserted into the solenoid coil and can move back and forth. The inductance of the coil is related to the length of the magnetically permeable piston rod inserted into the coil. When displacement occurs, it will cause a change in the inductance of the coil. The inductance frequency modulation circuit converts the change in the inductance of the coil into a frequency signal, and the displacement value can be displayed through a reading instrument. Compared with other types of single-point displacement meters, the inductance frequency modulation type single-point displacement meter has higher stability, reliability and durability.

[0004] The inductance frequency modulation type single-point displacement meter is composed of a displacement meter body (including a magnetically permeable piston rod and a solenoid coil), a stainless steel reinforcement measuring rod, a PVC measuring rod protection tube, and an anchor head. The anchor head needs to be fixed by drilling and grouting, and the degree of fixation directly determines the reliability of the test data of the single-point displacement meter.

[0005] However, when installing the single-point displacement meter upward in the surrounding rock at the tunnel vault, it is difficult for the grouting slurry to collect and consolidate at the anchor head position, resulting in difficulties in fixing the anchor head and failure in installing the single-point displacement meter. Moreover, it is also difficult to effectively mix and anchor the resin anchoring agent using the stainless steel reinforcement measuring rod and the anchor head. In this regard, some methods have been tried to set an anchor claw at the anchor head position to fix the anchor head, but the actual fixing effect is often difficult to achieve satisfactory results. In addition, there is a problem that the solenoid coil in the single-point displacement meter body is difficult to reliably fix before the initial support shotcrete solidifies. The above problems seriously affect the reliability of the installation of the inductance frequency modulation type single-point displacement meter and the accuracy of the measurement data. SUMMARY

[0006] In view of the above technical problems, the present application provides a method for measuring internal displacement of surrounding rock at a tunnel vault, to solve the problems of difficulty in anchoring the anchor head and difficulty in fixing the solenoid coil of the single-point displacement meter when the inductance frequency modulation type single-point displacement meter is installed upward at the tunnel vault, and to ensure the reliability of the installation of the inductance frequency modulation type single-point displacement meter and the accuracy of the measurement data.

[0007] The technical solution adopted by the present application is as follows:

[0008] A tunnel vault surrounding rock internal displacement measurement method, comprising the following steps:

[0009] 【1】Drill a hole in the surrounding rock of the vault, and fix a single-point displacement meter on a mounting bracket;

[0010] The single-point displacement meter comprises an upper and lower relative displacement solenoid coil and a piston rod;

[0011] The mounting bracket comprises a protective cover, a connecting cylinder and a measuring rod, the measuring rod is installed in the drill hole, and the upper end of the measuring rod is fixed in the interior of the surrounding rock by a resin anchoring agent; the upper end of the protective cover is fixed on the surface of the surrounding rock, and the lower end of the protective cover is fixedly connected with the solenoid coil of the displacement meter; the connecting cylinder comprises an upper connecting cylinder and a lower connecting cylinder which are movably connected; the upper connecting cylinder is fixedly connected with the lower end of the measuring rod, and the lower connecting cylinder is fixedly connected with the piston rod, so that the anchoring point, the measuring rod and the piston rod are integrated;

[0012] 【2】Spray concrete on the surface of the surrounding rock to form primary support, and cover the protective cover in the sprayed concrete, so that the protective cover, the solenoid coil and the primary support sprayed concrete are integrated;

[0013] 【3】Connect the solenoid coil to an external reading instrument by a wire, and collect the displacement parameters of the surrounding rock inside the vault by the reading instrument.

[0014] In the tunnel vault surrounding rock internal displacement measurement method, an anchor is arranged in the upper connecting cylinder, so as to realize the fixed connection of the lower end of the measuring rod and the upper connecting cylinder.

[0015] In the tunnel vault surrounding rock internal displacement measurement method, a wall protection steel pipe is arranged in the drill hole, and the measuring rod is a steel strand, so that the wall protection steel pipe is sleeved outside the measuring rod to avoid the extrusion constraint of the drill hole wall on the measuring rod.

[0016] In the tunnel vault surrounding rock internal displacement measurement method, the anchoring method of the measuring rod in the surrounding rock is that the resin anchoring agent is sent to the deepest part of the drill hole, then the steel strand measuring rod is inserted into the drill hole, the drill machine drives the steel strand measuring rod to stir the resin anchoring agent, and after the stirring is completed, the corresponding time is solidified to realize the anchoring of the steel strand measuring rod in the deep drill hole.

[0017] In the tunnel vault surrounding rock internal displacement measurement method, the installation method of the wall protection steel pipe is that the wall protection steel pipe (9) passes through the exposed section of the steel strand measuring rod, and then the wall protection steel pipe is pushed into the drill hole by the drill machine, and under the action of the drill hole diameter shrinkage deformation and the axial friction resistance, the wall protection steel pipe is left in the drill hole.

[0018] In the tunnel vault surrounding rock internal displacement measurement method, the exposed end length of the measuring rod is 10-20 cm.

[0019] The protective steel pipe is a whole steel pipe or a plurality of threaded steel pipes.

[0020] The upper part of the connecting cylinder and the lower part of the connecting cylinder are connected through threads.

[0021] The upper end of the protective cover is fixed on the surface of the surrounding rock through expansion screws, and the lower end of the protective cover is fixed on the surface of the surrounding rock through threads.

[0022] The beneficial technical effects of the present application are as follows:

[0023] I. When the inductance frequency modulation type single-point displacement meter is installed upward on the tunnel vault, the uppermost end of the steel strand measuring rod can be reliably anchored at a specified position in the surrounding rock, and the lowermost end of the steel strand measuring rod can be effectively connected with the piston rod in the body of the displacement meter, thereby ensuring that the anchoring part (the displacement point to be measured) in the surrounding rock, the steel strand measuring rod and the piston rod are integrated, and the solenoid coil is reliably fixed on the surface of the surrounding rock through the protective cover. The problems of difficult anchoring and installation failure of the single-point displacement meter when the single-point displacement meter is installed upward on the surrounding rock of the tunnel vault are overcome, and reliable and accurate measurement of the displacement of the anchoring point in the surrounding rock is achieved.

[0024] II. The solenoid coil in the body of the single-point displacement meter can be fixed on the surface of the surrounding rock before the initial support sprayed concrete solidifies, so that the solenoid coil in the body of the single-point displacement meter and the surface of the surrounding rock deform uniformly, and the measurement data read by the reading instrument is the accurate relative displacement between the anchoring part and the surface of the surrounding rock. In summary, the technical scheme of the present application can ensure the reliability of the installation of the inductance frequency modulation type single-point displacement meter and the accuracy of the measurement data, and achieve accurate measurement of the displacement of the tunnel vault. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 It is a schematic diagram of the installation support of the single-point displacement meter in the embodiment of the present application;

[0026] Figure 2 It is a schematic diagram of the anchorage device fixed on the steel strand in the embodiment of the present application;

[0027] Figure 3 It is a schematic diagram of the connection between the upper part of the connecting cylinder and the lower part of the connecting cylinder in the embodiment of the present application;

[0028] Figure 4 It is a schematic diagram of the connection between the lower part of the connecting cylinder and the piston rod of the displacement meter in the embodiment of the present application;

[0029] Figure 5A schematic diagram of the protective cover fixed on the surface of the surrounding rock in the embodiment of the present application;

[0030] Figure 6 A schematic diagram of the connection between the protective cover and the piston rod of the displacement meter in the embodiment of the present application;

[0031] Figure 7 A step diagram of the tunnel vault surrounding rock internal displacement measurement method based on the single-point displacement meter of the present application.

[0032] The reference signs: 1-solenoid coil; 2-piston rod; 3-protective cover; 4-connection cylinder upper part; 5-connection cylinder lower part; 6-anchor; 7-steel strand measuring rod; 8-resin anchoring agent; 9-steel pipe for wall protection; 10-surrounding rock; 11-expansion screw; 12-sprayed concrete; 13-reading instrument. DETAILED DESCRIPTION

[0033] As shown in the drawings, Figures 1-6 The following takes the installation of the inductance frequency modulation type single-point displacement meter at the tunnel vault and the surrounding rock internal displacement measurement as an example to introduce the specific technical solution of the present application. The single-point displacement meter comprises the solenoid coil 1 and the piston rod 2 for the relative displacement, and the reading instrument obtains the relative displacement parameters between the solenoid coil 1 and the piston rod 2 to realize the displacement measurement of the measured target.

[0034] The installation support of the inductance frequency modulation type single-point displacement meter provided by the present application comprises the protective cover 3, the connection cylinder and the measuring rod 7. The connection cylinder comprises the connection cylinder upper part 4 and the connection cylinder lower part 5 which are movably connected. The upper end of the protective cover 3 is fixed on the surrounding rock 10, and the lower end is fixedly connected with the solenoid coil 1 of the displacement meter. The connection cylinder upper part 4 is fixedly connected with the lower end of the measuring rod 7, and the connection cylinder lower part 5 is fixedly connected with the piston rod 2 of the displacement meter. The surrounding rock 10 to be measured is provided with a drill hole, the measuring rod 7 is installed in the drill hole, and the upper end of the measuring rod 7 is fixed in the interior of the surrounding rock 10 by the resin anchoring agent 8.

[0035] Figure 2 In the embodiment, the measuring rod 7 is preferably a whole steel strand, the upper end of which penetrates into the deep part of the surrounding rock 10 through the drill hole, and the resin anchoring agent 8 is used to realize the adhesive anchoring between the upper end of the steel strand measuring rod 7 and the surrounding rock 10. The lower end of the steel strand measuring rod 7 is located outside the drill hole, and the exposed end length of the measuring rod 7 is 12 cm. The steel pipe for wall protection 9 is penetrated through the steel strand measuring rod 7 from bottom to top and is then pushed into the drill hole, and finally is placed in the outer circle of the steel strand measuring rod 7 to play a supporting role for the drill hole wall, so as to avoid the influence of the frictional resistance of the external medium on the steel strand measuring rod 7 and affect the accuracy of the single-point displacement meter test results. The steel pipe for wall protection 9 can be a whole steel pipe or can be formed by threadedly connecting the steel pipes section by section.

[0036] As shown in the drawings, Figures 3 to 5As shown, the lower part 5 of the connecting cylinder is connected with the piston rod 2 in the body of the displacement meter by screw thread; the upper part 4 of the connecting cylinder is connected with the lower part 5 by screw thread; the anchor 6 is arranged in the upper part 4 of the connecting cylinder to realize the fixed connection of the lower end of the steel strand measuring rod 7 and the upper part 4 of the connecting cylinder. The lower end of the steel strand measuring rod 9 is effectively connected with the piston rod 2 of the displacement meter by means of the anchor 6, the upper part 4 and the lower part 5 of the connecting cylinder; wherein the anchor 6 adopts a single-hole anchor available in the market, and the anchor 6 is fixed to the lower end of the steel strand measuring rod 7 by the wedge-shaped clamping piece internally provided.

[0037] The upper end of the protective cover 3 is fixed to the surface of the surrounding rock 10 by means of the expansion screw 11, and the lower end of the protective cover 3 is connected with the solenoid coil 1 in the body of the displacement meter by screw thread. The single-point displacement meter and the protective cover 3 are covered by the sprayed concrete 12 after installation, and are connected with the external reading instrument 13 through the lead wire. The piston rod 2 in the body of the displacement meter is free relative to the solenoid coil 1 in the body of the displacement meter and can move back and forth, and the relative displacement between the two is the measurement result of the single-point displacement meter, which is read and displayed by the reading instrument 13.

[0038] As shown in the figure, Figure 7 The tunnel vault surrounding rock internal displacement measurement method based on the inductance frequency modulation type single-point displacement meter of the present application comprises the following steps:

[0039] (1) Vault drilling: drilling a hole for anchoring the steel strand measuring rod in the surrounding rock 10 of the vault;

[0040] (2) Installation of the steel strand measuring rod 7: the resin anchoring agent 8 is sent to the deepest part of the hole, and then the steel strand measuring rod 7 is inserted into the hole, and the drill is used to stir the resin anchoring agent 8 to realize the anchoring of the steel strand measuring rod 7 at the deep part of the hole;

[0041] (3) Installation of the wall protection steel pipe 9: the wall protection steel pipe 9 is passed through the exposed section of the steel strand measuring rod 7, and then the wall protection steel pipe 9 is pushed into the hole by the drill, and under the action of the hole diameter shrinkage deformation and the axial friction resistance, the wall protection steel pipe 9 is permanently left in the hole;

[0042] (4) Installation of the upper part 4 of the connecting cylinder and the anchor 6: the upper part 4 of the connecting cylinder and the anchor 6 are installed in sequence through the exposed end of the steel strand measuring rod 7 to fix the anchor to the exposed end of the steel strand measuring rod;

[0043] (5) Installation of the lower part 5 of the connecting cylinder: the lower part 5 of the connecting cylinder is connected with the upper part 4 of the connecting cylinder by screw thread;

[0044] (6) Installation of the piston rod 2 in the body of the displacement meter: the connection between the piston rod 2 and the lower part 5 of the connecting cylinder is realized by screw thread;

[0045] (7) Install protective cover 3: install and fix protective cover 3 on the surface of surrounding rock 10 by means of expansion screws;

[0046] (8) Install solenoid coil 1 in single-point displacement meter body: solenoid coil 1 in single-point displacement meter body is connected with the lower part of protective cover 3 by means of threads;

[0047] (9) Perform initial support shotcrete 12: perform initial support shotcrete 12 construction, completely cover and fix protective cover 3 on the surface of surrounding rock 10, at this time, protective cover 3, solenoid coil 1 in single-point displacement meter body and initial support shotcrete 12 are an integral whole.

[0048] (10) Collect readings: connect solenoid coil 1 to external reading instrument 13 through wires, and collect displacement parameters inside the vault surrounding rock by reading instrument 13.

[0049] When inductance frequency modulation type single-point displacement meter is installed on the top of the tunnel, the uppermost end of steel strand measuring rod 7 can be reliably anchored at a specified position in the deep part of surrounding rock 10, and the lowermost end of steel strand measuring rod 7 can be effectively connected with piston rod 2 in the displacement meter body, so as to ensure that the anchoring part, steel strand measuring rod 7 and piston rod 2 are an integral whole. In addition, it can also ensure that solenoid coil 1 in single-point displacement meter body can be fixed on the surface of surrounding rock 10 before initial support shotcrete 12 solidifies, so that solenoid coil 1 in single-point displacement meter body and the surface of surrounding rock 10 are consistent deformation, and the measurement data read by reading instrument 13 is the accurate relative displacement between the anchoring part and the surface of surrounding rock 10. By using the technical scheme of the present application, the reliability of the installation of inductance frequency modulation type single-point displacement meter and the accuracy of the measurement data can be ensured.

[0050] The above content is only for illustrating the technical idea of the present application, and cannot limit the protection scope of the present application. Any modification made according to the technical idea of the present application on the basis of the technical scheme falls within the protection scope of the claims of the present application.

Claims

1. A method for measuring displacement of the inner surrounding rock of a tunnel vault, characterized in that, It comprises the following steps: 【1】Drilling a hole in the surrounding rock (10) of the vault, fixing a single-point displacement meter on a mounting bracket; The single-point displacement meter comprises a solenoid coil (1) and a piston rod (2) for up-down relative displacement; The mounting bracket comprises a protective outer cover (3), a connecting cylinder and a measuring rod (7), the measuring rod (7) is installed in the drilling hole, the upper end of the measuring rod (7) is fixed in the surrounding rock (10) by a resin anchoring agent; the upper end of the protective outer cover (3) is fixed on the surface of the surrounding rock (10), and the lower end of the protective outer cover (3) is fixedly connected with the solenoid coil (1) of the displacement meter; the connecting cylinder comprises an upper connecting cylinder (4) and a lower connecting cylinder (5) which are movably connected; the upper connecting cylinder (4) is fixedly connected with the lower end of the measuring rod (7), and the lower connecting cylinder (5) is fixedly connected with the piston rod (2), so that the anchoring point, the measuring rod (7) and the piston rod (2) are integrated; The solenoid coil (1) in the single-point displacement meter body is deformed in accordance with the surface of the surrounding rock (10); 【2】Spraying concrete (12) on the surface of the surrounding rock for initial support, covering the protective outer cover (3) in the sprayed concrete (12) to integrate the protective outer cover (3), the solenoid coil (1) and the sprayed concrete (12) for initial support; 【3】Connecting the solenoid coil (1) to an external reading instrument (13) through a wire, and collecting displacement parameters inside the surrounding rock of the vault by the reading instrument (13); An anchor (6) is arranged in the upper connecting cylinder (4) to realize the fixed connection of the lower end of the measuring rod (7) and the upper connecting cylinder (4); A wall protection steel pipe (9) is installed in the drilling hole, and the measuring rod (7) is a steel strand, and the wall protection steel pipe (9) is sleeved outside the measuring rod (7); The anchoring method of the measuring rod (7) in the surrounding rock is that the resin anchoring agent (8) is sent to the deepest part of the drilling hole, then the steel strand measuring rod (7) is inserted into the drilling hole, the drilling machine drives the steel strand measuring rod (7) to stir the resin anchoring agent (8), and after the stirring is completed, the corresponding time is solidified to realize the anchoring of the steel strand measuring rod (7) at the deep part of the drilling hole; The installation method of the wall protection steel pipe (9) is that the wall protection steel pipe (9) passes through the exposed section of the steel strand measuring rod (7), then the wall protection steel pipe (9) is pushed into the drilling hole by the drilling machine, and under the action of the diameter shrinkage deformation and the axial friction resistance of the drilling hole, the wall protection steel pipe (9) is left in the drilling hole.

2. The method of measuring internal displacement of the surrounding rock above a tunnel vault according to claim 1, characterized in that: The exposed end length of the measuring rod (7) is 10-20 cm.

3. The method of measuring the internal displacement of the surrounding rock above a tunnel vault according to claim 1, characterized in that: The wall protection steel pipe (9) is a whole steel pipe or a plurality of threadedly connected steel pipes.

4. The method of measuring the displacement of the inner surrounding rock of a tunnel arch according to claim 1, characterized in that: The upper connecting cylinder (4) and the lower connecting cylinder (5) are movably connected through threads.

5. The method of measuring the displacement of the inner surrounding rock of a tunnel arch according to claim 1, characterized in that: The upper end of the protective outer cover (3) is fixed on the surface of the surrounding rock (10) by expansion screws, and the lower end of the protective outer cover (3) is fixedly connected with the solenoid coil (1) through threads.

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