A device and method for measuring deformation of surrounding rock in extremely soft rock tunnel

Abstract

The present invention provides a device and method for measuring deformation of surrounding rock in extremely soft rock tunnels. The measuring device includes a protective tube, a multi-point displacement meter, an inner sealing ring, an outer sealing ring and an auxiliary device outside the hole. The protective tube is used to support the hole wall of the measuring hole during the hole measurement construction process. The multi-point displacement meter is installed inside the protective tube. The sensor base of the multi-point displacement meter is located at the interface between the tunnel surrounding rock and the tunnel structure. The inner sealing ring and the outer sealing ring are used to respectively block the slurry filled in the protective tube and the measuring hole after grouting in the protective tube. The protective tube adopts a plurality of small sections to be detachably connected in series. The auxiliary device outside the hole is used to take out the protective tube while ensuring that the slurry is filled in the measuring hole. During the hole measurement construction of the present invention, the protective tube is first used to support the hole wall to prevent the hole from collapsing. The measuring equipment is installed in the protective tube and grouting is performed. After the hole mouth is blocked and the protective tube is taken out, the surrounding rock deformation measurement can be carried out. The phenomenon of the drill rod being stuck due to the collapse of the hole wall surrounding rock during the drilling process can be avoided. The measurement results can also reflect the deformation of the surrounding rock at different depths of the tunnel.

Description

Technical Field

[0001] The invention relates to the technical field of tunnel engineering, and in particular to a device and method for measuring deformation of surrounding rock of an extremely soft rock tunnel. Background Art

[0002] With the development of water conservancy and hydropower projects in my country, in order to solve the problem of uneven distribution of water resources, large-scale inter-basin water diversion projects such as the Han-Wei Diversion Project and the Xinjiang ABH Water Diversion Tunnel Project have been built one after another. The construction of water diversion projects in extremely soft rock mass is also a special problem encountered in recent years. According to my country's national standard "Specifications for Geological Survey of Water Conservancy and Hydropower Projects", rocks with a uniaxial saturated compressive strength of less than 5MPa are extremely soft rocks, and the representative rock masses are sandstone and mudstone. For example, the surrounding rock of the Qin Pandaoling Tunnel of the Yangtze River Diversion Project is sandstone with a uniaxial compressive strength of only 0.2MPa to 0.8MPa, which brings great difficulties to the design and construction of the project.

[0003] The physical and mechanical properties of the surrounding rock of extremely soft rock tunnels are poor. Underground projects built in extremely soft rock formations are prone to landslides of varying degrees, causing casualties and equipment losses. Safety monitoring is a key measure to ensure safe construction and is of great significance to the design and construction of extremely soft rock tunnels. In traditional extremely soft rock tunnel surrounding rock deformation measurement, the measuring equipment is buried on the surface of the tunnel surrounding rock or in the tunnel lining structure to measure the deformation of the rock mass on the tunnel surface to the internal space of the tunnel. The measurement results cannot reflect the deformation of the surrounding rock at different depths of the tunnel.

[0004] Due to the poor properties of the surrounding rock in extremely soft rock tunnels, there are two difficulties in installing monitoring equipment in the surrounding rock: first, when constructing the measuring hole, the hole wall is prone to collapse and jam the drill, making it difficult to construct the measuring hole to the designed depth; second, after the measuring hole is constructed, the surrounding rock of the hole wall quickly deforms and blocks the measuring hole, making it impossible to install monitoring equipment and backfill grouting in the measuring hole. Summary of the invention

[0005] The technical problem to be solved by the present invention is to overcome the shortcomings of the prior art and provide a device and method for measuring the deformation of the surrounding rock of an extremely soft rock tunnel. During hole measurement construction, a protective pipe is first used to support the hole wall to prevent hole collapse. The measuring equipment is installed in the protective pipe and grouting is performed. After the hole opening is sealed and the protective pipe is removed, the surrounding rock deformation measurement can be carried out, which can avoid the phenomenon of the drill rod being stuck due to the collapse of the hole wall surrounding rock during the drilling process.

[0006] A device for measuring deformation of surrounding rock of an extremely soft rock tunnel comprises a protective pipe, a multi-point displacement meter, an inner sealing ring, an outer sealing ring and an auxiliary device outside the hole, wherein the protective pipe is used to support the hole wall of a measuring hole during the measuring hole construction process, the multi-point displacement meter is installed inside the protective pipe, a sensor base of the multi-point displacement meter is located at the interface between the tunnel surrounding rock and the tunnel structure, the inner sealing ring and the outer sealing ring are used to respectively block the slurry filled in the protective pipe and the measuring hole after grouting in the protective pipe, the protective pipe is detachably connected in series with a plurality of small sections, and the auxiliary device outside the hole is used to take out the protective pipe while ensuring that the measuring hole is filled with slurry.

[0007] Furthermore, the out-of-hole auxiliary device includes a base, a hydraulic jack, a force transmission plate, and a portal frame. The hydraulic jack and the portal frame are installed and fixed on the base. The portal frame is provided with a force transmission plate. The hydraulic jack is located between the force transmission plate and the base. The end of the protective pipe can pass through the base and the force transmission plate in turn and be fixed to the force transmission plate.

[0008] Furthermore, a fastening nut is provided on the upper portion of the force transmission pad for connecting with the external thread of the protective tube, thereby achieving fixation of the protective tube and the force transmission pad.

[0009] Furthermore, the outside-hole auxiliary device also includes a stop rod, which includes an upper disk and a round rod located at the lower part connected to the disk, the disk is in contact with the sensor base of the multi-point displacement meter, and the other end of the round rod can pass through the frame beam on the portal frame and be limited by a stop pin.

[0010] Furthermore, a circular hole is provided between the lower portion of the round rod and the frame beam of the portal frame, and a stop pin is correspondingly provided in the circular hole. The stop pin is used to limit the round rod to prevent the multi-point displacement meter from being pulled out of the measuring hole together with the protective tube.

[0011] Furthermore, the multi-point displacement meter is provided with a slurry inlet pipe and an exhaust pipe, one end of the slurry inlet pipe is located outside the hole and the other end is located at the measuring hole mouth, and one end of the exhaust pipe is located outside the hole and the other end is located at the bottom of the measuring hole.

[0012] Furthermore, the cross-section of the force transmission pad is designed to be rectangular, with a circular hole in the center of the force transmission pad serving as a passage for the protective tube, and two square holes on both sides serving as passages for the frame columns on both sides of the portal frame; a circular hole is provided on the frame beam serving as a passage for the round rod of the stop rod.

[0013] A method for measuring deformation of surrounding rock in an extremely soft rock tunnel, which is performed using the above-mentioned measuring device, comprises the following steps:

[0014] Step 1: Hole measurement construction and protective pipe installation: Use a geological drill or down-the-hole drilling rig to drill holes and install protective pipes alternately at the point to be measured, and construct the hole measurement to the designed depth;

[0015] Step 2: Installation of the in-hole measuring device: Assemble the multi-point displacement meter on a flat site inside the tunnel, and then put it into the protective pipe. The sensor base of the multi-point displacement meter is located at the hole mouth, and the measuring points are located at different depths in the protective pipe. One end of the slurry inlet pipe of the multi-point displacement meter is located outside the hole and the other end is located at the hole mouth. One end of the exhaust pipe is located outside the hole and the other end is located at the bottom of the hole.

[0016] Step 3: Installation of the orifice plugging device: The slurry inlet pipe and the exhaust pipe are respectively passed through the two circular holes in the inner sealing ring, and then the inner sealing ring is inserted into the gap between the protective tube and the multi-point displacement meter, and the outer sealing ring is inserted from the outer port of the protective tube and moved to the orifice of the measuring hole;

[0017] Step 4: Installation of auxiliary devices outside the hole;

[0018] Step 5: Grouting in the protective pipe: Inject cement slurry from the grout inlet pipe of the multi-point displacement meter and exhaust the gas in the hole through the exhaust pipe. Continue grouting until the exhaust pipe discharges cement slurry. At this time, the protective pipe is filled with cement slurry, blocking the grout inlet pipe and the exhaust pipe.

[0019] Step 6: Remove the protective tube and seal the hole.

[0020] Further, the steps of step 4, installation of the auxiliary device outside the hole are as follows:

[0021] First, assemble the auxiliary device outside the hole. The assembly process is as follows:

[0022] Four hydraulic jacks are placed in the four circular concave holes of the base respectively, and the hydraulic jacks are fixed with stop bolts;

[0023] The end of the round rod of the stop rod with the round hole is inserted into the round hole of the portal frame until the disc contacts the frame beam of the portal frame;

[0024] The two square holes of the force transmission pad pass through the two frame columns of the portal frame until the fastening nuts on the force transmission pad contact the disc of the stop rod;

[0025] The two frame columns of the portal frame are inserted into the two square recessed holes of the base, and the portal frame is fixed with stop bolts;

[0026] Secondly, install the auxiliary device outside the hole: the circular hole in the base is inserted from the outer end of the protective tube, and the base is moved until the outer sealing ring fills the gap between the protective tube and the circular hole of the base.

[0027] Further, the specific steps of step six, taking out the protective tube and sealing the hole are as follows:

[0028] Step 601, connecting the outermost segmented protective tube:

[0029] Use the two frame columns of the portal frame as tracks, slide the force transmission pad until the outermost protective tube passes through the circular hole of the force transmission pad, and then put the fastening nut on the external thread of the outermost protective tube;

[0030] Push the round rod of the stop rod until the disc contacts the sensor base of the multi-point displacement meter, and insert the stop pin into the round hole to fix the stop rod;

[0031] Step 602: Take out the outermost segmented protective tube:

[0032] Add oil to the jack, push the force transmission pad to move out of the measuring hole and pull out the protective tube in the measuring hole. Stop adding oil after the outermost segmented protective tube moves out of the measuring hole. Take out the stop pin in the circular hole of the stop rod, move the stop rod out of the measuring hole until the disc moves out of the protective tube, and unscrew the fastening nut and the outermost segmented protective tube in turn.

[0033] Step 603, repeat steps 601 and 602 for multiple times until all the protective tubes are taken out, immediately close the measuring hole, and pull the monitoring cable to a nearby observation station to realize automated observation.

[0034] The present invention has the following beneficial effects:

[0035] (1) When constructing a borehole in the surrounding rock of an extremely soft rock tunnel, the present invention adopts a method of alternating drilling and installing protective pipes. During the drilling process, the drill rod will not be stuck due to the collapse of the surrounding rock of the borehole wall. After the borehole construction is completed, the surrounding rock of the borehole wall can also maintain long-term stability. The multi-point displacement meter measuring points can be installed at different depths of the surrounding rock. Compared with the traditional method of only measuring the deformation of the surface of the tunnel surrounding rock, the measurement results can reflect the deformation of the surrounding rock at different depths of the tunnel, and have stronger reliability and safety.

[0036] (2) The out-of-hole auxiliary device of the present invention uses a hydraulic jack to output power, and uses the frame column of the portal frame as a track to push the force transmission pad to slide out of the hole. The protective tube in the measuring hole can be stably removed without impact vibration, which can effectively avoid damage or loosening of the plugging device of the measuring hole opening. The hole opening has good sealing performance and does not leak slurry, which effectively improves the effectiveness and accuracy of the measuring device;

[0037] (3) The out-of-hole auxiliary device of the present invention adopts a slidable stop rod, one end of which abuts against the sensor base of the multi-point displacement meter in the protective tube, and the other end passes through the middle of the frame beam of the portal frame. When the protective tube is taken out, the stop pin is used to fix the stop rod to prevent the multi-point displacement meter in the hole from being pulled out together with the protective tube. After the protective tube is pulled out, the stop pin is released, and the protective tube can be unscrewed after the stop rod is pulled out from the middle of the frame beam of the portal frame. The present invention has a simple and reasonable structure and is highly practical.

[0038] (4) The in-hole multi-point displacement meter of the present invention adopts a high-precision vibrating-string sensor and can automatically observe. The measurement results are highly continuous and accurate, and early warning is given to large deformation of the surrounding rock of extremely soft rock tunnels in a timely manner, thereby avoiding casualties and equipment losses caused by landslide accidents, which is beneficial to saving project costs and construction period. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a cross-sectional schematic diagram of the device for measuring deformation of surrounding rock in an extremely soft rock tunnel according to the present invention;

[0040] Figure 2 It is a schematic diagram of the three-dimensional structure of the out-of-hole auxiliary device of the present invention;

[0041] Figure 3 A bottom view of the base of the out-of-hole auxiliary device of the present invention;

[0042] Figure 4 for Figure 3 Middle AA section view;

[0043] Figure 5 It is a bottom view of the force transmission pad in the out-of-hole auxiliary device of the present invention;

[0044] Figure 6 It is a schematic cross-sectional view of a portal frame in the out-of-hole auxiliary device of the present invention;

[0045] Figure 7 It is a cross-sectional schematic diagram of a stop rod in the out-of-hole auxiliary device of the present invention;

[0046] Figure 8 It is a bottom view of the outer sealing ring in the present invention.

[0047] The reference numerals in the figures are described as follows:

[0048] 1—protective pipe, 2—multi-point displacement meter, 2a—slurry inlet pipe, 2b—exhaust pipe, 3—inner sealing ring, 4—outer sealing ring, 4a—upper ring, 4b—lower ring, 5—base, 5a—circular concave hole, 5b—square concave hole, 5c—circular hole, 5d—stop bolt, 5e—stop bolt, 6—hydraulic jack, 7—force transmission pad, 7a—circular hole, 7b—square hole, 8—gantry frame, 8a—frame column, 8b—circular hole, 9—stop rod, 9a—disc, 9b—round rod, 9c—circular hole, 9d—stop pin, 10—tunnel surrounding rock, 11—tunnel structure. DETAILED DESCRIPTION

[0049] The technical solution of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the present invention.

[0050] See also Figure 1One embodiment of the extremely soft rock tunnel surrounding rock deformation measurement device of the present invention comprises a protective tube 1, a multi-point displacement meter 2, an inner sealing ring 3, an outer sealing ring 4 and an auxiliary device outside the hole. The protective tube 1 is used to support the hole wall of the measuring hole during the hole measurement construction process and serves as a container for the multi-point displacement meter 2 to be installed; the inner sealing ring 3 and the outer sealing ring 4 respectively block the protective tube 1 and the slurry filled in the measuring hole; the auxiliary device outside the hole is used to take out the protective tube 1 while ensuring that the measuring hole is filled with slurry.

[0051] Specifically during construction, the measuring hole drilling and the installation of the protective pipe 1 are first carried out alternately, and the measuring hole is constructed to the designed depth. Secondly, the multi-point displacement meter 2 is installed in the protective pipe 1 and grouting is performed. Then, the inner sealing ring 3 and the outer sealing ring 4 are used to respectively seal the protective pipe 1 and the slurry filled in the measuring hole. Finally, the protective pipe 1 is taken out while the slurry is filled in the measuring hole by an auxiliary device outside the hole, and the installation is completed. The measuring points can be installed at different depths of the surrounding rock. The measurement results can reflect the deformation of the surrounding rock at different depths of the tunnel, and have stronger accuracy, effectiveness and reliability.

[0052] The protective pipe 1 can be connected by upper and lower threads in small segments of the same length. The upper end of each segment is an internal thread and the lower end is an external thread. The protective pipe 1 is made of alloy steel. During hole measurement construction, it supports the hole wall and surrounding rock to prevent collapse. It is also a container for installing a multi-point displacement meter 2.

[0053] The multi-point displacement meter 2 is installed in the protective tube 1, the sensor base is located at the interface between the tunnel surrounding rock 10 and the tunnel structure 11, a vibrating wire sensor is arranged in the sensor base, and the measuring points are arranged at different depths in the protective tube 1. A slurry inlet pipe 2a and an exhaust pipe 2b are arranged on the multi-point displacement meter 2. One end of the slurry inlet pipe 2a is located outside the hole and the other end is located at the hole mouth of the measuring hole, and one end of the exhaust pipe 2b is located outside the hole and the other end is located at the bottom of the measuring hole.

[0054] The inner sealing ring 3 is used to seal the gap between the protective tube 1 and the multi-point displacement meter 2 to prevent the slurry filled in the protective tube 1 from leaking out. The inner sealing ring 3 is designed to be annular and made of rubber material, with two circular small holes symmetrically distributed on the left and right sides as the passage for the slurry inlet pipe 2a and the exhaust pipe 2b to enter the protective tube 1.

[0055] like Figure 8 As shown, the outer sealing ring 4 is designed to be annular and made of rubber material. It is divided into two upper and lower annular structures (i.e., an upper ring 4a and a lower ring 4b). The inner ring diameters of the upper ring 4a and the lower ring 4b are the same, and the outer ring diameter of the lower ring 4b is larger. The upper ring 4a is used to seal the gap between the protective tube 1 and the tunnel surrounding rock 10, and the lower ring 4b is used to seal the gap between the protective tube 1 and the base 5 of the auxiliary device outside the hole to prevent the slurry filled in the measuring hole from leaking out.

[0056] Please also read Figure 2-4The auxiliary device outside the hole includes a base 5, a hydraulic jack 6, a force transmission pad 7, a portal frame 8 and a stop rod 9. The axial section of the base 5 is designed to be concave. Four circular concave holes 5a and four stop bolts 5d are provided at the four top corners of the left and right walls of the concave structure for installing and fixing the hydraulic jack 6. Two square concave holes 5b and two stop bolts 5e are provided in the middle of the left and right walls of the concave structure for installing and fixing the portal frame 8. The fixed portal frame 8 is provided with a force transmission pad 7. The end of the protective tube 1 passes through the force transmission pad 7 and is fixed to the force transmission pad 7. The hydraulic jack 6 is located between the force transmission pad 7 and the base 5; a circular hole 5c is provided in the center of the base 5 as a passage for the protective tube 1.

[0057] The hydraulic jack 6 is installed in the circular recessed hole 5a of the base 5. After the oil cylinder is filled with oil, the top bracket of the hydraulic jack 6 pushes the force transmission pad 7 to move. Since the protective tube 1 passes through the force transmission pad 7 and is fixed to the force transmission pad 7, the force transmission pad 7 pulls the protective tube 1 out of the measuring hole with the frame columns 8a on both sides of the portal frame 8 as tracks.

[0058] like Figure 5 As shown, the cross-section of the force transmission pad 7 is designed to be rectangular, and the center of the force transmission pad 7 is a circular hole 7a, which serves as a passage for the protective tube 1. Two square holes 7b are provided on both sides, which serve as passages for the frame columns 8a on both sides of the portal frame 8. A fastening nut is provided on the upper part of the force transmission pad 7, which is connected to the external thread of the protective tube 1.

[0059] like Figure 6 As shown, the frame columns 8a on both sides of the portal frame 8 are tracks for the force transmission pad 7 to move up and down, and a circular hole 8b is provided on the frame beam as a passage for the round rod 9b of the stop rod 9.

[0060] like Figure 7 As shown, the stop rod 9 includes an upper disc 9a and a lower round rod 9b connected to the disc 9a. The round rod 9b is used to support the disc 9a. The other end of the round rod 9b passes through the circular hole 8b of the frame beam of the portal frame 8 (as shown in FIG. Figure 6 As shown). Three circular holes 9c are provided between the lower part of the round rod 9b and the frame beam of the portal frame 8, and stop pins 9d are provided in the circular holes 9c. The stop pins 9d are used to fix the round rod 9b to prevent the round rod 9b from slipping out of the frame beam of the portal frame 8. The stop pins 9d pass through the circular holes 9c on the round rod 9a, and the two ends are close to the frame beam of the portal frame 8. The disc 9a abuts against the sensor base and the inner sealing ring 3 of the multi-point displacement meter 2. At the same time, since the round rod 9b is limited by the stop pins 9d, the multi-point displacement meter 2 can be prevented from being pulled out of the measuring hole together with the protective tube 1.

[0061] The embodiment of the present invention further provides a method for measuring deformation of surrounding rock in an extremely soft rock tunnel, which is performed using the above-mentioned measuring device. The method comprises the following steps:

[0062] Step 1: Hole measurement construction and protective pipe installation: Use a geological drill or down-the-hole drilling rig to drill holes and install protective pipe 1 alternately at the point to be measured, and construct the hole measurement to the designed depth; the specific steps are as follows:

[0063] When drilling a hole, drill 0.5m first, then remove the drill rod and drill bit, and put the uppermost protective pipe 1 into the measuring hole;

[0064] Insert the drill rod and drill bit and continue drilling. When the drilling depth reaches the length of one segmented protective pipe 1, stop drilling and remove the drill rod and drill bit.

[0065] Screw the internal thread of the upper end of the next segmented protective pipe 1 into the external thread of the uppermost segment protective pipe 1, place a pad on the outer end of the protective pipe 1, and then use the drill pipe to press the protective pipe 1 into the measuring hole;

[0066] Insert the drill rod and drill bit and continue drilling, reciprocating in sequence, until the measured hole reaches the designed depth;

[0067] At this time, the surrounding rock of the inner wall of the measuring hole is supported by the protective pipe 1 and the hole will not collapse. A high-pressure water pump is used to flush the inner wall of the protective pipe 1. After flushing, a compressed air machine is used to blow out the accumulated water in the measuring hole.

[0068] Step 2. Installation of the in-hole measuring device: Assemble the multi-point displacement meter 2 on a flat site inside the tunnel, and then put it into the protective pipe 1. The sensor base of the multi-point displacement meter 2 is located at the hole mouth, and the measuring points are located at different depths in the protective pipe 1. One end of the slurry inlet pipe 2a of the multi-point displacement meter 2 is located outside the hole and the other end is located at the hole mouth, and one end of the exhaust pipe 2b is located outside the hole and the other end is located at the bottom of the hole.

[0069] Step 3: Installation of the orifice plugging device: The slurry inlet pipe 2a and the exhaust pipe 2b are respectively passed through the two circular holes in the inner sealing ring 3, and then the inner sealing ring 3 is inserted into the gap between the protective tube 1 and the multi-point displacement meter 2, and the outer sealing ring 4 is inserted from the outer port of the protective tube 1 and moved to the measuring hole orifice.

[0070] Step 4: Installation of auxiliary devices outside the hole:

[0071] First, assemble the auxiliary device outside the hole. The assembly process is as follows:

[0072] Four hydraulic jacks 6 are placed in the four circular recessed holes 5a of the base 5, respectively, and the hydraulic jacks 6 are fixed by stop bolts 5d;

[0073] The end of the round rod 9a of the stop rod 9 with the round hole 9c is inserted into the round hole 8b of the portal frame 8 until the disc 9a contacts the frame beam of the portal frame 8;

[0074] The two square holes 7b of the force transmission pad 7 pass through the two frame columns 8a of the portal frame 8 until the fastening nut on the force transmission pad 7 contacts the disc 9a of the stop rod 9;

[0075] The two frame columns 8a of the portal frame 8 are inserted into the two square recessed holes 5b of the base 5, and the portal frame 8 is fixed by using the stop bolts 5e;

[0076] Next, install the auxiliary device outside the hole: insert the circular hole 5c in the base 5 from the outer end of the protective tube 1, and move the base 5 until the outer sealing ring 4 fills the gap between the protective tube 1 and the circular hole 5c of the base 5;

[0077] Step 5: Grouting in the protective pipe: Inject cement slurry from the slurry inlet pipe 2a of the multi-point displacement meter 2 and exhaust the gas in the hole through the exhaust pipe 2b. Continue grouting until the cement slurry is discharged from the exhaust pipe 2b. At this time, the protective pipe 1 is filled with cement slurry, blocking the slurry inlet pipe 2a and the exhaust pipe 2b.

[0078] Step 6: Remove the protective tube and seal the hole:

[0079] Step 601, connecting the outermost segmented protective tube 1:

[0080] Using the two frame columns 8a of the portal frame 8 as tracks, slide the force transmission pad 7 until the outermost protective tube 1 passes through the circular hole 7a of the force transmission pad 7, and then put the fastening nut on the external thread of the outermost protective tube 1;

[0081] Push the round rod 9b of the stop rod 9 until the disc 9a contacts the sensor base of the multi-point displacement meter 2, and insert the stop pin 9d into the round hole 9c to fix the stop rod 9;

[0082] Step 602: Take out the outermost segmented protective tube 1:

[0083] Add oil to the jack, push the force transmission pad 7 to move out of the measuring hole and pull out the protective tube 1 in the measuring hole. Stop adding oil after the outermost segmented protective tube 1 moves out of the measuring hole. Take out the stop pin 9d in the circular hole 9c of the stop rod 9, move the stop rod 9 out of the measuring hole until the disc 9a moves out of the protective tube 1, and unscrew the fastening nut and the outermost segmented protective tube 1 in turn.

[0084] Step 603, repeat steps 601 and 602 for multiple times until all the protective tubes 1 are taken out, and the measuring hole is immediately closed, and the monitoring cable is pulled to a nearby observation station to realize automated observation.

[0085] After the out-of-hole auxiliary device is assembled, it can be fixed by a steel pipe scaffold or fixed on a rock drilling trolley to have stronger fluidity and operability.

[0086] When constructing a measuring hole in the surrounding rock of an extremely soft rock tunnel, the present invention adopts a method of alternating drilling and installing a protective pipe. During the drilling process, the drill rod will not be stuck due to the collapse of the hole wall surrounding rock. After the measuring hole construction is completed, the hole wall surrounding rock can also maintain long-term stability. The multi-point displacement meter measuring points can be installed at different depths of the surrounding rock. Compared with the traditional method of only measuring the surface deformation of the tunnel surrounding rock, its measurement results can reflect the deformation of the surrounding rock at different depths of the tunnel, and have stronger reliability and safety. In addition, the out-of-hole auxiliary device adopts a hydraulic jack output, with the frame column of the portal frame as the track, to push the force transmission pad to slide out of the hole, and the protective pipe in the measuring hole can be stably taken out without impact vibration, which can effectively avoid damage or loosening of the sealing device of the measuring hole mouth. The hole mouth has good sealing performance and does not leak slurry, which effectively improves the effectiveness and accuracy of the measuring device.

[0087] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A device for measuring deformation of surrounding rock in extremely soft rock tunnels, characterized in that: The invention comprises a protective pipe (1), a multi-point displacement meter (2), an inner sealing ring (3), an outer sealing ring (4) and an auxiliary device outside the hole, wherein the protective pipe (1) is used to support the hole wall of the measuring hole during the hole measurement construction process, the multi-point displacement meter (2) is installed inside the protective pipe (1), the sensor base of the multi-point displacement meter (2) is located at the interface between the tunnel surrounding rock (10) and the tunnel structure (11), the inner sealing ring (3) and the outer sealing ring (4) are used to respectively block the slurry filled in the protective pipe (1) and the measuring hole after grouting in the protective pipe (1), the protective pipe (1) is detachably connected in series with a plurality of small sections, and the auxiliary device outside the hole is used to remove the protective pipe (1) while ensuring that the measuring hole is filled with slurry; The out-of-hole auxiliary device comprises a base (5), a hydraulic jack (6), a force transmission pad (7), and a portal frame (8); the hydraulic jack (6) and the portal frame (8) are installed and fixed on the base (5); a force transmission pad (7) is slidably provided on the portal frame (8); the hydraulic jack (6) is located between the force transmission pad (7) and the base (5); and the end of the protective pipe (1) can pass through the base (5) and the force transmission pad (7) in sequence and be fixed to the force transmission pad (7); A fastening nut is provided on the upper part of the force transmission pad (7) for connecting with the external thread of the protective tube (1), thereby fixing the protective tube (1) and the force transmission pad (7); The out-of-hole auxiliary device also includes a stop rod (9), which includes an upper disk (9a) and a lower round rod (9b) connected to the disk (9a), the disk (9a) contacts the sensor base of the multi-point displacement meter (2), and the other end of the round rod (9b) can pass through the frame beam on the portal frame (8) and be limited by a stop pin (9d).

2. The extremely soft rock tunnel surrounding rock deformation measurement device according to claim 1, characterized in that: A circular hole (9c) is provided between the lower part of the round rod (9b) and the frame beam of the portal frame (8), and a stop pin (9d) is correspondingly provided in the circular hole (9c). The stop pin (9d) is used to limit the round rod (9b) to prevent the multi-point displacement meter (2) from being pulled out of the measuring hole together with the protective tube (1).

3. The extremely soft rock tunnel surrounding rock deformation measurement device according to claim 1, characterized in that: The multi-point displacement meter (2) is provided with a slurry inlet pipe (2a) and an exhaust pipe (2b), one end of the slurry inlet pipe (2a) is located outside the hole and the other end is located at the hole mouth of the measuring hole, and one end of the exhaust pipe (2b) is located outside the hole and the other end is located at the bottom of the measuring hole.

4. The extremely soft rock tunnel surrounding rock deformation measurement device according to claim 1, characterized in that: The cross section of the force transmission pad (7) is designed to be rectangular. The center of the force transmission pad (7) is a circular hole (7a) serving as a passage for the protective tube (1). Two square holes (7b) are provided on both sides as passages for the frame columns (8a) on both sides of the portal frame (8). A circular hole (8b) is provided on the frame beam as a passage for the round rod (9b) of the stop rod (9).

5. A method for measuring deformation of surrounding rock in extremely soft rock tunnel, characterized in that The method is carried out using the measuring device according to any one of claims 1 to 4, and comprises the following steps: Step 1: Hole drilling and protection pipe installation: Use a geological drill or down-the-hole drilling machine to drill holes and install protection pipes (1) alternately at the point to be measured to construct the hole to the designed depth; Step 2, installation of the in-hole measuring device: assemble a multi-point displacement meter (2) on a flat site inside the tunnel, and then put it into the protective pipe (1), the base of the multi-point displacement meter (2) is located at the hole mouth, the measuring points are located at different depths in the protective pipe (1), one end of the slurry inlet pipe (2a) of the multi-point displacement meter (2) is located outside the hole and the other end is located at the hole mouth, and one end of the exhaust pipe (2b) is located outside the hole and the other end is located at the bottom of the hole; Step 3: Installation of the orifice plugging device: The slurry inlet pipe (2a) and the exhaust pipe (2b) are respectively passed through the two circular holes in the inner sealing ring (3), and then the inner sealing ring (3) is inserted into the gap between the protective tube (1) and the multi-point displacement meter (2), and the outer sealing ring (4) is inserted from the outer end of the protective tube (1) and moved to the orifice of the measuring hole; Step 4: Installation of auxiliary devices outside the hole; Step 5: Grouting in the protective pipe: inject cement slurry from the slurry inlet pipe (2a) of the multi-point displacement meter (2) and exhaust the gas in the hole through the exhaust pipe (2b), and continue grouting until the exhaust pipe (2b) exhausts the cement slurry. At this time, the protective pipe (1) is filled with cement slurry, and the slurry inlet pipe (2a) and the exhaust pipe (2b) are blocked; Step 6: Remove the protective tube and seal the hole.

6. The method for measuring deformation of surrounding rock in an extremely soft rock tunnel according to claim 5, characterized in that: Step 4: The specific steps for installing the auxiliary device outside the hole are as follows: First, assemble the auxiliary device outside the hole. The assembly process is as follows: Four hydraulic jacks (6) are respectively placed in the four circular recessed holes (5a) of the base (5), and the hydraulic jacks (6) are fixed by using stop bolts (5d); The end of the round rod (9a) of the stop rod (9) with the round hole (9c) is inserted into the round hole (8b) of the portal frame (8) until the disc (9a) contacts the frame beam of the portal frame (8); The two square holes (7b) of the force transmission pad (7) pass through the two frame columns (8a) of the portal frame (8) until the fastening nut on the force transmission pad (7) contacts the disc (9a) of the stop rod (9); The two frame columns (8a) of the portal frame (8) are inserted into the two square recessed holes (5b) of the base (5), and the portal frame (8) is fixed by using stop bolts (5e); Next, the external auxiliary device is installed: the circular hole (5c) in the base (5) is inserted from the outer end of the protective tube (1), and the base (5) is moved until the outer sealing ring (4) fills the gap between the protective tube (1) and the circular hole (5c) of the base (5).

7. The method for measuring deformation of surrounding rock in an extremely soft rock tunnel according to claim 6, characterized in that: Step 6: Remove the protective tube and seal the hole. The specific steps are as follows: Step 601, connecting the outermost segmented protective tube (1): Using the two frame columns (8a) of the portal frame (8) as tracks, slide the force transmission pad (7) until the outermost protective tube (1) passes through the circular hole (7a) of the force transmission pad (7), and sleeve the fastening nut on the external thread of the outermost protective tube (1); Push the round rod (9b) of the stop rod (9) until the disc (9a) contacts the sensor base of the multi-point displacement meter (2), and insert the stop pin (9d) into the round hole (9c) to fix the stop rod (9); Step 602: Take out the outermost segmented protective tube (1). Add oil to the jack, push the force transmission pad (7) to move out of the measuring hole and pull out the protective tube (1) in the measuring hole. Stop adding oil after the outermost segmented protective tube (1) moves out of the measuring hole. Take out the stop pin (9d) in the circular hole (9c) of the stop rod (9). Move the stop rod (9) out of the measuring hole until the disc (9a) moves out of the protective tube (1). Unscrew the fastening nut and the outermost segmented protective tube (1) in turn. Step 603, repeat steps 601 and 602 for multiple times until all the protective tubes (1) are taken out, immediately close the measuring hole, and pull the monitoring cable to a nearby observation station to realize automated observation.

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