Method for determining length of anchoring and bonding section of anchor rod adapted to disturbance influence of roadway cyclic excavation

Abstract

A method for determining the length of the anchoring and bonding section of a rock bolt to adapt to the disturbance of cyclic tunneling, a test borehole is constructed on the roof; a fixed monitoring device is installed in the test borehole; during the tunneling operation, the fixed monitoring device is used to collect and store vibration signals; a portable acquisition terminal is used to receive and store the vibration signals; an industrial computer is used to receive the vibration signals and analyze and process them to obtain vibration excitation data; an anchoring test piece is made; a low-frequency vibration simulation test system is used to obtain vibration signal data according to the similarity ratio, and the anchoring test piece is subjected to vibration excitation according to the vibration signal data; then, an electro-hydraulic servo mechanics test system is used for pull-out testing; and finally, the loosening damage degree of the anchoring interface corresponding to different bonding lengths of the anchoring test piece is analyzed by comprehensively analyzing the pull-out stress, displacement data and acoustic emission monitoring data during the pull-out test. The method can effectively determine the length of the anchoring and bonding section of the rock bolt to adapt to the disturbance of cyclic tunneling.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of intelligent mine safety monitoring, and particularly relates to a method for determining the length of an anchoring and bonding section of an anchor rod suitable for the disturbance influence of cyclic heading in a roadway. BACKGROUND

[0002] Roadway deformation originates from excavation and disturbance, and the multiple disturbances caused by cyclic heading during excavation are the leading causes of initial damage and later instability of the anchoring system. The essence of cyclic heading disturbance is periodic loading and unloading of the adjacent anchoring body, which can easily cause the anchoring interface of the end anchor and lengthened anchor commonly used in the roadway to be damaged and loose, and the anchoring system to be micro-fractured and deformed, which can continuously evolve and adversely affect the long-term bearing performance of the roadway and become a major threat to mine safety production. Therefore, it is crucial to scientifically determine the length of the anchoring and bonding section of the anchor rod according to the anchoring interface loosening damage characteristics during cyclic heading in the roadway, to increase the threshold of anchoring and bonding interface damage weakening, and to strengthen the bearing performance of the anchoring system, which has important scientific significance and theoretical value.

[0003] According to the engineering site application and related theoretical research, there is still less research on the disturbance of cyclic heading in the roadway to the anchoring system, which is the leading cause of progressive fracture failure of the anchoring system and deformation instability of the surrounding rock. In the engineering site, the existing anchor support system generally uses the engineering experience method to determine the length of the anchoring and bonding section, which lacks adaptability to the influence of cyclic heading disturbance in high-stress roadways with increasing mining depth, and the anchoring interface is damaged and weakened, the support efficiency is reduced, and the rock mass fracture damage is caused in the early stage of excavation, which lays hidden dangers for later instability and affects the long-term bearing performance of the roadway. Therefore, it is urgent to provide a method for determining the length of the anchoring and bonding section of the anchor rod suitable for the disturbance influence of cyclic heading in the roadway to provide a more solid guarantee for mine safety production. SUMMARY

[0004] In view of the problems in the prior art, the application provides a method for determining the length of the anchoring and bonding section of the anchor rod suitable for the disturbance influence of cyclic heading in the roadway, which can effectively determine the length of the anchoring and bonding section of the anchor rod suitable for the disturbance influence of cyclic heading in the roadway, provide strong support for designing the length of the anchoring and bonding section of the anchor rod suitable for the disturbance influence of cyclic heading in the roadway in the engineering site, and provide a reliable technical means for overall comparison and analysis of different strata affected by the disturbance of cyclic heading, which has good application value.

[0005] In order to achieve the above object, the present application provides a kind of determination method of anchoring and bonding section length of anchor rod adapting to the disturbance influence of roadway cyclic excavation, adopt a vibration signal monitoring system, the vibration signal monitoring system includes fixed monitoring device and portable acquisition terminal, the fixed monitoring device includes hollow metal pole, intelligent sensing module and pick-up sensor;The hollow metal pole is sequentially divided into free section, sensing section and anchoring section from first end to end, multiple wire holes are sequentially and spaced apart in the length direction of the sensing section and are communicated to the inner cavity of hollow metal pole;The intelligent sensing module includes shell, microcontroller, storage module one, wireless transmission module one and power module one;The shell is box type structure, its top plate is fixedly installed at the first end of hollow metal pole, and the top plate of shell is provided with the communication hole communicated with the inner cavity of hollow metal pole;The wireless transmission module one, microcontroller, storage module one and power module one are all installed in the inside of shell;The microcontroller is connected with storage module one, wireless transmission module one and power module one respectively;The number of pick-up sensor is multiple, multiple pick-up sensors are sequentially and spaced apart fixedly installed on the pole of hollow metal pole along the length direction of sensing section, and the wires connected thereon are respectively threaded into the inside of hollow metal pole through multiple wire holes, and are connected with microcontroller after passing through communication hole;The portable acquisition terminal includes machine shell, wireless transmission module two, processor, storage module two and power module two;The wireless transmission module two, processor, storage module two and power module two are all installed in the inner cavity of machine shell, and wireless transmission module two is connected with wireless transmission module one by wireless communication mode;Processor is connected with wireless transmission module two, storage module two and power module two respectively;

[0006] The determination method of anchoring and bonding section length of anchor rod adapting to the disturbance influence of roadway cyclic excavation includes the following steps:

[0007] Step one: during the excavation operation of the excavation equipment in the roadway, a test borehole is constructed on the roof of the support area close to the excavation head behind the excavation head;

[0008] Step two: prepare a fixed monitoring device that is suitable for the size of the test borehole, place the resin anchoring agent at the bottom of the test borehole, and then insert the anchoring section of the hollow metal pole into the bottom of the test borehole, so as to firmly fix the anchoring section of the hollow metal pole at the bottom of the test borehole by using the resin anchoring agent, and simultaneously, the multiple pick-up sensors are distributed in the anchoring and bonding section height L2 range of the anchor rod anchored in the roof, and the shell is exposed outside the orifice;

[0009] Step three: after the fixed monitoring device is installed, the tunneling operation is started, and during the tunneling operation, the distance L from the fixed monitoring device to the tunneling head gradually increases. During the period when the tunneling head is within the tunneling disturbance sensing range of the fixed monitoring device, each tunneling will cause a cyclic loading and unloading, and the cyclic vibration signal generated during the cyclic loading and unloading process propagates through the coal rock mass to the rod of the hollow metal rod. A plurality of seismic sensors are used to synchronously collect the cyclic vibration signal in real time and send it to the microcontroller. After receiving the cyclic vibration signal, the microcontroller adds a time stamp to the cyclic vibration signal to form a time-stamped time sequence cyclic vibration signal, and sends the time sequence cyclic vibration signal to the storage module one for storage;

[0010] The above cyclic vibration signal acquisition process continues until the distance L from the fixed monitoring device to the tunneling head exceeds the sensing critical distance value, and the tunneling head is no longer within the sensing range of the fixed monitoring device. The cyclic vibration signal acquisition operation is completed;

[0011] Step four: the portable acquisition terminal is manually held to the position of the fixed monitoring device for underground signal acquisition operation. Within the effective transmission distance range of the wireless signal, a wireless communication link is established between the wireless transmission module two and the wireless transmission module one. After the wireless communication link is established, the microcontroller reads the cyclic vibration signal in the storage module one and sends it to the processor through the wireless communication link. After receiving the cyclic vibration signal, the processor stores it in the storage module two;

[0012] Step five: after the underground signal acquisition operation is completed, the portable acquisition terminal is transferred to the ground, and a communication link between the portable acquisition terminal and the industrial computer is established through wireless communication. After the communication link is established, the portable acquisition terminal reads the cyclic vibration signal in the storage module two and sends it to the industrial computer through the communication link. The industrial computer analyzes and processes the cyclic vibration signal to obtain vibration frequency and amplitude data, and uses the data as vibration excitation data. At the same time, the vibration excitation data is stored in the vibration signal database;

[0013] Step six: under laboratory conditions, n different bonding lengths s 1、 s 2、 s 3··· s n of anchor specimens are made by using seamless steel pipes, ordinary steel pipes, vaseline, mortar concrete, left-handed threaded steel anchor rods commonly used in coal mines, and resin anchoring agents, wherein n≤10;

[0014] S61: prepare a seamless steel pipe with an opening at one end and a closed end at the other end, a length of 200-400 mm, an outer diameter of 50-55 mm, and an inner diameter of 40-45 mm; prepare a common steel pipe with an outer diameter of 30 mm and a length of 300-550 mm, and coat vaseline on the outer wall of the common steel pipe, then insert the common steel pipe into the seamless steel pipe, and expose the outer end of the common steel pipe to the outside of the opening end of the seamless steel pipe;

[0015] S62: according to the lithology of the rock mass within the anchoring and bonding height L2 of the roof anchor, prepare a mortar concrete using similar material simulation to simulate the lithology of the rock mass within L2, and fill the mortar concrete into the annular gap between the common steel pipe and the seamless steel pipe, the end face of the injected mortar concrete is flush with the opening end of the seamless steel pipe, and the mortar concrete is cured for 28 days;

[0016] S63: pull out the common steel pipe to form a mortar ring with a thickness of 10-15 mm and a test hole with a diameter of 30 mm in the inner cavity of the seamless steel pipe;

[0017] S64: according to the three-diameter matching principle of the anchor rod diameter, the borehole diameter, and the resin anchoring agent diameter, respectively calculate the required resin anchoring agent amount for forming a bonding length of s 1、 s 2、 s 3··· s n , and sequentially place n portions of resin anchoring agent and n left-handed threaded steel anchors with a length of 300-550 mm and a diameter of 22 mm into the n test holes, respectively, to complete the preparation of anchoring test pieces with different bonding lengths s 1、 s 2、 s 3··· s n , and obtain n anchoring test pieces;

[0018] Step seven: use a low-frequency vibration simulation test system, convert the vibration excitation data to obtain the required vibration signal data in the laboratory experiment according to the similarity ratio of the similar simulation experiment, and then excite the prepared anchoring test piece according to the vibration signal data, and then use an electro-hydraulic servo mechanics test system to test the anchoring test piece, and comprehensively analyze the anchoring force change, the relative displacement of the rod wall, and the rupture information of the anchoring test piece by using the displacement data, the stress data in the pulling experiment, and the acoustic emission monitoring data obtained by using the acoustic emission monitoring system, complete the test of the n anchoring test pieces, and then compare and analyze the weakening law of the anchoring interface bonding strength of the anchoring test pieces with different bonding lengths corresponding to the amplitude and vibration frequency, and then determine the loosening damage characteristics of the inner and outer ring bonding interfaces of the anchoring test pieces with different bonding lengths, and according to the test results, analyze the loosening damage degree w 1、 w 2、 w 3··· wn and according to the anchoring interface failure critical value w 临 The corresponding anchoring specimen bonding length is obtained when the anchoring interface failure occurs 临 ;

[0019] Step eight: 30% to 50% s 临 According to the similar ratio conversion of the similar simulation experiment, the critical anchoring bonding length S of the roof anchor in the actual engineering site is obtained 临锚 This length is the anchoring bonding length of the anchor that adapts to the disturbance influence of the roadway cyclic tunneling.

[0020] Further, in order to ensure the reliable connection between the shell and the hollow metal rod, the shell is connected with the first end of the hollow metal rod by welding.

[0021] As a preferred, the distance between two adjacent vibration sensors is 50-200mm.

[0022] As a preferred, in step three, the inductive critical distance value is 60-100m.

[0023] As a preferred, in step two, the length of the hollow metal rod is 300-600mm longer than the anchor anchored in the roof, and the diameter of the hollow metal rod is 30-60mm; the length of the vibration sensor is 30-60mm, and the width is 20-40mm.

[0024] Further, in order to facilitate the smooth installation of the fixed monitoring device in the test drill hole, in step two, the length of the test drill hole is matched with the length of the hollow metal rod, and the hole diameter is 6-10mm larger than the sum of the diameter of the hollow metal rod and the width of the vibration sensor.

[0025] As a preferred, in step seven, the anchoring interface failure critical value w 临 of the anchoring specimen is determined as follows: the critical loosening damage degree of the anchoring interface of the anchoring specimen from the loosening damage to the debonding failure is defined as w 临 .

[0026] The hollow metal rod is fixedly installed in the bottom of the drill hole through the anchor agent in the installation process, and vibration signals can be stably obtained during continuous monitoring. A plurality of pick-up sensors are installed in the length direction of the sensing section of the hollow metal rod at intervals, which can effectively adapt to the sensing and picking-up requirements of different layers of rock strata in the length range of the anchor rod anchoring and bonding section for head-on cyclic excavation vibration signals, so that vibration signals of multiple different layers of rock strata can be obtained at the same time by only setting one fixed monitoring device. A plurality of wire holes are sequentially arranged in the length direction of the sensing section of the hollow metal rod, which can facilitate the wires connected to the plurality of pick-up sensors to smoothly enter the inside of the rod body and extend to the first end of the rod body, thereby facilitating connection with the intelligent sensing module at the first end of the rod body. Meanwhile, this arrangement is conducive to protecting the wires, thereby preventing damage to the wires due to external scratching and ensuring reliable reception of vibration signals. The power module one can stably supply power for the fixed monitoring device, so that the fixed monitoring device has the ability to work offline, thereby eliminating the need to lay power supply lines for the fixed monitoring device. The shell is fixedly installed at the first end of the hollow metal rod, which can be conveniently exposed outside the hole after the hollow metal rod is installed in the drill hole, thereby ensuring reliable transmission of wireless signals. The microcontroller in the intelligent sensing module can provide the intelligent sensing module with certain data processing capabilities, so that when receiving the vibration signals transmitted by the pick-up sensors, the microcontroller can add a timestamp to the vibration signals, thereby forming a time sequence cyclic vibration signal with a timestamp, which facilitates obtaining corresponding time information when processing the vibration signals. The storage module one can facilitate data storage and reading, so that the microcontroller can not only conveniently store the processed data in the storage module one, but also read the data from the storage module one and send it to the portable acquisition terminal through the wireless communication link after the wireless communication link is established. The wireless transmission module one in the intelligent sensing module and the wireless transmission module two in the portable acquisition terminal can form a wireless communication link between the fixed monitoring device and the portable acquisition terminal through wireless connection between the wireless transmission module one and the wireless transmission module two, thereby ensuring reliable data transmission between the two. The power module two can supply power for the portable acquisition terminal, thereby enabling the portable acquisition terminal to work offline and improving portability. The processor can facilitate data processing and facilitate interaction with the industrial computer, thereby enabling the received data to be sent to the industrial computer.The vibration signal monitoring system has high integration degree and automation degree, and accurate monitoring result; through cooperation of the fixed monitoring device and the portable acquisition terminal, the vibration signals of different layer positions of rock mass in the height range of the anchoring and bonding section of the anchor rod in the tunneling operation process can be monitored and collected simultaneously, thereby providing reliable technical support for the subsequent test process under laboratory conditions.

[0027] The anchoring and bonding section length of the anchor rod adapting to the disturbance influence of the cyclic tunneling is determined in the application, and is suitable for the fields of geotechnical engineering or well and tunnel engineering. Firstly, in the process of tunneling, a fixed monitoring device is installed at the roof drilling hole following the tunneling head, and with the tunneling head continuing to cyclically tunnel forward, the fixed monitoring device will receive the vibration signals of each cyclic tunneling disturbance until the distance between the fixed monitoring device and the tunneling head exceeds a certain critical value, that is, the fixed monitoring device is no longer within the cyclic tunneling disturbance range of the tunneling head. Then, the vibration signal data sensed and stored by the fixed monitoring device is collected by a portable acquisition terminal, and the vibration signal data is sent to an industrial computer on the ground, so that the industrial computer obtains vibration excitation data required for subsequent low-frequency vibration simulation test according to the vibration signal data. The vibration excitation data is derived from the real working environment, and thus the accuracy of the simulation effect in the subsequent simulation test can be effectively ensured. In the laboratory, the anchoring test piece is made of seamless steel pipe, ordinary steel pipe, vaseline, mortar concrete, left-handed threaded steel anchor rod commonly used in coal mines and resin anchoring agent, which can effectively reduce the test cost, and at the same time, the anchor rod anchoring interface in the real environment can be effectively simulated, thereby facilitating the simulation process of the loosening damage degree of the anchoring interface corresponding to the anchoring test piece with different bonding lengths in a low-cost and safer manner under laboratory conditions. For the anchoring test piece, a low-frequency vibration simulation test system is adopted, and vibration excitation is obtained according to the vibration excitation data collected on site in a similar ratio, and then a pull-out test is performed by using an electro-hydraulic servo mechanics test system, and further comprehensive experimental data such as stress, displacement and acoustic emission monitoring can be used to analyze the anchoring interface damage critical value and the corresponding critical bonding length of the anchoring test piece, and then the corresponding anchor rod critical anchoring and bonding section length in the field is obtained through conversion, that is, the anchoring and bonding section length of the anchor rod adapting to the disturbance influence of the cyclic tunneling.

[0028] The method combines on-site vibration signal collection, laboratory condition prepared anchoring test piece, low-frequency vibration simulation test system vibration excitation, electro-hydraulic servo mechanics test system for pulling test, acoustic emission monitoring system for acoustic emission monitoring, the whole implementation process has high automation degree, effectively reduces the dependence on artificial, and reduces the labor intensity of artificial, the monitoring and analysis result of the method is accurate, can accurately determine the length of the anchoring and bonding section of the anchor rod adapting to the disturbance influence of the roadway cyclic tunneling, can provide strong support for designing the length of the anchoring and bonding section of the anchor rod adapting to the disturbance influence of the roadway cyclic tunneling in engineering field, provides a reliable technical means for overall comparison and analysis of different layer position rock mass affected by the disturbance of cyclic tunneling, and has good application value. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The schematic diagram for determining the length of the anchoring and bonding section of the anchor rod adapting to the disturbance influence of the roadway cyclic tunneling of the present application;

[0030] Figure 2 The structural schematic diagram of the fixed monitoring device in the present application;

[0031] Figure 3 The structural schematic diagram of the portable collection terminal in the present application;

[0032] Figure 4 The principle block diagram of the vibration signal monitoring system in the present application.

[0033] In the figure: 1, roadway; 2, tunneling equipment; 3, head-on; 4, roof; 5, anchor rod; 6, test borehole; 7, resin anchoring agent; 8, fixed monitoring device; 8-1, hollow metal rod; 8-2, vibration sensor; 8-3, wire; 8-4, intelligent sensing module; 8-5, shell; 9, portable collection terminal; 9-1, processor; 9-2, storage module two; 9-3, wireless transmission module two; 9-4, machine shell. DETAILED DESCRIPTION

[0034] The present application will be further described below in combination with the drawings.

[0035] As Figures 1 to 4As shown, the present application provides a method for determining the length of the anchoring and bonding section of the anchor rod which is suitable for the disturbance influence of the cycle tunneling, adopts a vibration signal monitoring system, the vibration signal monitoring system comprises a fixed monitoring device 8 and a portable acquisition terminal 9, the fixed monitoring device 8 comprises a hollow metal rod 8-1, an intelligent sensing module 8-4 and a vibration sensor 8-2; the hollow metal rod 8-1 is sequentially divided into a free section, a sensing section and an anchoring section from the first end to the last end, a plurality of wire holes which are communicated to the inner cavity of the hollow metal rod 8-1 are sequentially and spaced apart in the length direction of the sensing section; the intelligent sensing module 8-4 comprises a shell 8-5, a microcontroller, a storage module one, a wireless transmission module one and a power module one; the shell 8-5 is a box structure, the top plate of the shell 8-5 is fixedly installed at the first end of the hollow metal rod 8-1, and a communication hole which is communicated to the inner cavity of the hollow metal rod 8-1 is formed in the top plate of the shell 8-5; the wireless transmission module one, the microcontroller, the storage module one and the power module one are all installed in the inner part of the shell 8-5; the microcontroller is connected with the storage module one, the wireless transmission module one and the power module one respectively; the number of the vibration sensors 8-2 is multiple, the multiple vibration sensors 8-2 are sequentially and spaced apart fixedly installed on the rod body of the hollow metal rod 8-1 along the length direction of the sensing section, the wires 8-3 connected thereto are respectively inserted into the inner part of the hollow metal rod 8-1 through the multiple wire holes, and are connected with the microcontroller after passing through the communication hole; the portable acquisition terminal 9 comprises a machine shell 9-4, a wireless transmission module two 9-3, a processor 9-1, a storage module two 9-2 and a power module two; the wireless transmission module two 9-3, the processor 9-1, the storage module two 9-2 and the power module two are all installed in the inner cavity of the machine shell 9-4, and the wireless transmission module two 9-3 is connected with the wireless transmission module one in a wireless communication mode; the processor 9-1 is connected with the wireless transmission module two 9-3, the storage module two 9-2 and the power module two respectively;

[0036] The method for determining the length of the anchoring and bonding section of the anchor rod which is suitable for the disturbance influence of the cycle tunneling comprises the following steps:

[0037] Step one: during the tunneling operation of the tunneling equipment 2 in the tunnel 1, a test drill hole 6 is constructed on the roof 4 of the support area close to the tunneling head 3 behind the tunneling head 3;

[0038] Step two: a fixed monitoring device 8 which is suitable for the size of the test drill hole 6 is prepared, the resin anchoring agent 7 is placed at the bottom of the test drill hole 6, and the anchoring section of the hollow metal rod 8-1 is inserted into the bottom of the test drill hole 6, so that the anchoring section of the hollow metal rod 8-1 is firmly fixed to the bottom of the test drill hole 6 by the resin anchoring agent 7, and meanwhile, the multiple vibration sensors 8-2 are correspondingly distributed in the anchoring and bonding section height L2 range of the anchor rod 5 anchored in the roof 4, as Figure 1As shown, the height L1 is the height of the unbonded section, leaving the shell 8-5 exposed to the outside of the borehole;

[0039] Step three: after the fixed monitoring device 8 is installed, the tunneling operation is started. During the tunneling operation, the distance L between the fixed monitoring device 8 and the tunneling head 3 gradually increases. During the period when the tunneling head 3 is within the tunneling disturbance sensing range of the fixed monitoring device 8, each tunneling operation will cause cyclic loading and unloading, and the cyclic vibration signals generated during the cyclic loading and unloading process will propagate through the coal and rock mass to the rod of the hollow metal rod 8-1. A plurality of seismic sensors 8-2 are used to synchronously collect the cyclic vibration signals in real time and send them to the microcontroller. After receiving the cyclic vibration signals, the microcontroller adds a time stamp to the cyclic vibration signals to form time-sequenced cyclic vibration signals with time stamps, and sends the time-sequenced cyclic vibration signals to the storage module one for storage. As a preferred embodiment, the number of seismic sensors 8-2 can be two, three, four, five or more to meet the needs of different layer rock bodies in the height L2 range for sensing and picking up the head cyclic tunneling vibration signals.

[0040] The above process of collecting cyclic vibration signals continues until the distance L between the fixed monitoring device 8 and the tunneling head 3 exceeds the sensing critical distance value, and the tunneling head 3 is no longer within the sensing range of the fixed monitoring device 8, and the cyclic vibration signal collection operation is completed.

[0041] Step four: the portable collection terminal 9 is manually carried to the location of the fixed monitoring device 8 for underground signal collection. Within the effective transmission distance of the wireless signal, a wireless communication link is established between the wireless transmission module two 9-3 and the wireless transmission module one. After the wireless communication link is established, the microcontroller reads the cyclic vibration signals in the storage module one and sends them to the processor 9-1 through the wireless communication link. After receiving the cyclic vibration signals, the processor 9-1 stores them in the storage module two 9-2.

[0042] Step five: after the underground signal collection operation is completed, the portable collection terminal 9 is transferred to the ground, and a communication link is established between the portable collection terminal 9 and the industrial computer through wireless communication. After the communication link is established, the portable collection terminal 9 reads the cyclic vibration signals in the storage module two 9-2 and sends them to the industrial computer through the communication link. The industrial computer analyzes and processes the cyclic vibration signals to obtain vibration frequency and amplitude data, and uses the data as vibration excitation data. At the same time, the vibration excitation data is stored in the vibration signal database.

[0043] Step six: under laboratory conditions, n different bond lengths s 1、 s 2、 s3··· s n n≤10;

[0044] S61:Prepare a seamless steel pipe with a length of 200-400 mm, an outer diameter of 50-55 mm, an inner diameter of 40-45 mm, and one open end and the other closed end; prepare a common steel pipe with an outer diameter of 30 mm and a length of 300-550 mm, and coat vaseline on the outer wall of the common steel pipe, then insert the common steel pipe into the seamless steel pipe and expose the outer end of the common steel pipe to the outside of the open end of the seamless steel pipe; the length of the common steel pipe is 300-550 mm, which can ensure that the length of the exposed section is 100-150 mm, which can facilitate subsequent pulling out operation.

[0045] S62:According to the lithology of the rock mass within the anchoring and bonding height L2 of the anchor rod 5 in the roof 4, a mortar concrete is prepared by simulating the lithology of the rock mass within the L2 range, and the mortar concrete is filled in the annular gap between the common steel pipe and the seamless steel pipe, the end face of the mortar concrete after injection is flush with the open end of the seamless steel pipe, and the mortar concrete is cured for 28 days;

[0046] S63:Pull out the common steel pipe to form a mortar ring with a thickness of 10-15 mm and a test hole with a diameter of 30 mm in the inner cavity of the seamless steel pipe; wherein the mortar ring is used to simulate the rock mass within the anchoring and bonding height L2

[0047] S64:According to the three-diameter matching principle of anchor rod diameter, drilling diameter and resin anchoring agent diameter, the required amount of resin anchoring agent for forming bonding length s 1、 s 2、 s 3··· s n is calculated, and n parts of resin anchoring agent and n left-handed threaded steel anchor rods with a length of 300-550 mm and a diameter of 22 mm are placed in the n test holes in turn, respectively, to complete the preparation of the anchoring test pieces with different bonding lengths s 1、 s 2、 s 3··· s n , and n anchoring test pieces are obtained; the length of the left-handed threaded steel anchor rod is 300-550, which can ensure that the length of the exposed section is about 100-150 mm, so that subsequent pull-out test can be facilitated;

[0048] Step seven: the low-frequency vibration simulation test system is used, and vibration excitation data are converted into vibration signal data required in the indoor experiment according to a similarity ratio of the similar simulation experiment; the prepared anchoring test piece is vibrated according to the vibration signal data, then the anchoring test piece is pulled by using the electro-hydraulic servo mechanics test system, the anchoring force change of the anchoring test piece, the relative displacement of the rod wall and the rupture information are obtained by comprehensively analyzing the pulling stress, displacement data and acoustic emission monitoring data obtained by using the acoustic emission monitoring system during the pulling experiment, the test of the n anchoring test pieces is completed, the weakening law of the anchoring interface bonding strength of the anchoring test piece corresponding to different bonding lengths is compared and analyzed according to the amplitude and vibration frequency, and then the loosening damage characteristics of the anchoring inner ring and outer ring bonding interfaces of the anchoring test piece with different bonding lengths are determined; according to the test results, the loosening damage degree w of the anchoring interface corresponding to the anchoring test piece with different bonding lengths is analyzed 1、 w 2、 w 3··· w n , and the critical bonding length s of the anchoring test piece corresponding to the anchoring interface damage is obtained 临 ; 临 ;

[0049] Step eight: the 30% to 50% s 临 is converted into the critical anchoring bonding length S of the anchor rod 5 in the roof 4 in the actual engineering site according to the similarity ratio of the similar simulation experiment 临锚 , and the critical anchoring bonding length S 临锚 is the critical value of the anchoring segment length L2 of the anchoring interface of the anchor rod anchoring system when the anchoring interface is damaged under the disturbance of the engineering site roadway cyclic excavation, and the length is the anchoring bonding length of the anchor rod which adapts to the disturbance of the roadway cyclic excavation.

[0050] In order to ensure the reliable connection between the shell and the hollow metal rod, the shell 8-5 is connected with the first end of the hollow metal rod 8-1 by welding.

[0051] As a preferred, the distance between two adjacent vibration sensors 8-2 is 50-200mm.

[0052] As a preferred, in step three, the inductive critical distance value is 60-100m.

[0053] As a preferred, in step two, the length of the hollow metal rod 8-1 is 300-600mm longer than the anchor rod 5 anchored in the roof 4, and the diameter of the hollow metal rod 8-1 is 30-60mm; the length of the vibration sensor 8-2 is 30-60mm, and the width is 20-40mm.

[0054] In order to facilitate the installation of the fixed monitoring device in the test borehole, in step two, the length of the test borehole 6 is adapted to the length of the hollow metal rod 8-1, and the diameter of the test borehole 6 is 6-10 mm larger than the sum of the diameter of the hollow metal rod 8-1 and the width of the seismic sensor 8-2.

[0055] As a preferred, in step seven, the anchorage specimen anchorage interface failure critical value w 临 is determined as follows: the critical debonding damage degree of the anchorage specimen anchorage interface from the loose damage to the debonding failure is defined as w 临 .

[0056] The hollow metal rod is fixedly installed in the bottom of the drill hole through the anchor agent in the installation process, and vibration signals can be stably obtained during continuous monitoring. A plurality of pick-up sensors are installed in the length direction of the sensing section of the hollow metal rod at intervals, which can effectively adapt to the sensing and picking-up requirements of different layers of rock strata in the length range of the anchor rod anchoring and bonding section for head-on cyclic excavation vibration signals, so that vibration signals of multiple different layers of rock strata can be obtained at the same time by only setting one fixed monitoring device. A plurality of wire holes are sequentially arranged in the length direction of the sensing section of the hollow metal rod, which can facilitate the wires connected to the plurality of pick-up sensors to smoothly enter the inside of the rod body and extend to the first end of the rod body, thereby facilitating connection with the intelligent sensing module at the first end of the rod body. Meanwhile, this arrangement is conducive to protecting the wires, thereby preventing damage to the wires due to external scratching and ensuring reliable reception of vibration signals. The power module one can stably supply power for the fixed monitoring device, so that the fixed monitoring device has the ability to work offline, thereby eliminating the need to lay power supply lines for the fixed monitoring device. The shell is fixedly installed at the first end of the hollow metal rod, which can be conveniently exposed outside the hole after the hollow metal rod is installed in the drill hole, thereby ensuring reliable transmission of wireless signals. The microcontroller in the intelligent sensing module can provide the intelligent sensing module with certain data processing capabilities, so that when receiving the vibration signals transmitted by the pick-up sensors, the microcontroller can add a timestamp to the vibration signals, thereby forming a time sequence cyclic vibration signal with a timestamp, which facilitates obtaining corresponding time information when processing the vibration signals. The storage module one can facilitate data storage and reading, so that the microcontroller can not only conveniently store the processed data in the storage module one, but also read the data from the storage module one and send it to the portable acquisition terminal through the wireless communication link after the wireless communication link is established. The wireless transmission module one in the intelligent sensing module and the wireless transmission module two in the portable acquisition terminal can form a wireless communication link between the fixed monitoring device and the portable acquisition terminal through wireless connection between the wireless transmission module one and the wireless transmission module two, thereby ensuring reliable data transmission between the two. The power module two can supply power for the portable acquisition terminal, thereby enabling the portable acquisition terminal to work offline and improving portability. The processor can facilitate data processing and facilitate interaction with the industrial computer, thereby enabling the received data to be sent to the industrial computer.The vibration signal monitoring system has high integration degree and automation degree, and accurate monitoring result; through cooperation of the fixed monitoring device and the portable acquisition terminal, the vibration signals of different layer positions of rock mass in the height range of the anchoring and bonding section of the anchor rod in the tunneling operation process can be monitored and collected simultaneously, and reliable technical support is provided for the subsequent test process under laboratory conditions.

[0057] The anchoring and bonding section length of the anchor rod adapting to the disturbance influence of the cyclic tunneling in the roadway in the application is suitable for the fields of geotechnical engineering or well and roadway engineering. Firstly, in the process of tunneling, the fixed monitoring device is installed at the roof drilling hole following the tunneling head in the roadway, and with the tunneling head continuing to cyclically tunnel forward, the fixed monitoring device will receive the vibration signals of each cyclic tunneling disturbance until the distance between the fixed monitoring device and the tunneling head exceeds a certain critical value, that is, the fixed monitoring device is no longer within the cyclic tunneling disturbance range of the tunneling head. Then, the vibration signal data sensed and stored by the fixed monitoring device is collected by the portable acquisition terminal, and the vibration signal data is sent to the industrial computer on the ground, so that the industrial computer obtains the vibration excitation data required for subsequent low-frequency vibration simulation test according to the vibration signal data. The vibration excitation data is derived from the real working environment, which can effectively ensure the accuracy of the simulation effect in the subsequent simulation test. In the laboratory, the anchoring test piece is made of seamless steel pipe, ordinary steel pipe, vaseline, mortar concrete, left-handed threaded steel anchor rod commonly used in coal mines and resin anchoring agent, which can effectively reduce the test cost, and at the same time, the anchor rod anchoring interface in the real environment can be effectively simulated, which is beneficial to the simulation process of the loosening damage degree of the anchoring interface corresponding to the anchoring test piece with different bonding lengths in the laboratory under the condition of low cost and safer way. For the anchoring test piece, the low-frequency vibration simulation test system is adopted, and the vibration excitation is obtained according to the vibration excitation data collected on site by using the similar ratio method, and then the pull-out test is carried out by using the electro-hydraulic servo mechanics test system. Further comprehensive analysis of the experimental data such as stress, displacement and acoustic emission monitoring can obtain the anchoring interface damage critical value and the corresponding critical bonding length of the anchoring test piece, and then the corresponding anchor rod critical anchoring and bonding section length in the field is obtained through conversion, that is, the anchoring and bonding section length of the anchor rod adapting to the disturbance influence of the cyclic tunneling in the roadway.

[0058] The method combines on-site collection of vibration signals, preparation of anchoring test pieces in a laboratory, vibration excitation by a low-frequency vibration simulation test system, pull-out testing by an electro-hydraulic servo mechanics test system, and acoustic emission monitoring by an acoustic emission monitoring system. The entire implementation process has a high degree of automation, effectively reduces the dependence on manual work, and reduces the labor intensity of manual work. The monitoring and analysis results are accurate, can accurately determine the length of the anchoring and bonding section of the anchor rod that adapts to the disturbance influence of roadway cyclic excavation, and can provide strong support for designing the length of the anchoring and bonding section of the anchor rod that adapts to the disturbance influence of roadway cyclic excavation in the engineering site. It provides a reliable technical means for overall comparison and analysis of the influence of cyclic excavation disturbance on different layer rock masses, and has good application value.

Claims

1. A method for determining the length of an anchoring and bonding section of a rock bolt adapted to the disturbance influence of a roadway cyclic tunneling, using a vibration signal monitoring system, the vibration signal monitoring system comprising a fixed monitoring device (8) and a portable acquisition terminal (9), the fixed monitoring device (8) comprising a hollow metal rod (8-1), an intelligent sensing module (8-4) and a vibration pickup sensor (8-2); the hollow metal rod (8-1) is sequentially divided into a free section, a sensing section and an anchoring section from the first end to the last end, and a plurality of wire passing holes are sequentially and spaced apart in the length direction of the sensing section and are communicated to the inner cavity of the hollow metal rod (8-1); the intelligent sensing module (8-4) comprises a shell (8-5), a microcontroller, a storage module one, a wireless transmission module one and a power module one; the shell (8-5) is a box structure, the top plate of which is fixedly installed at the first end of the hollow metal rod (8-1), and a communication hole is formed in the top plate of the shell (8-5) and is communicated to the inner cavity of the hollow metal rod (8-1); the wireless transmission module one, the microcontroller, the storage module one and the power module one are all installed inside the shell (8-5); the microcontroller is connected with the storage module one, the wireless transmission module one and the power module one respectively; the number of the vibration pickup sensors (8-2) is multiple, and the multiple vibration pickup sensors (8-2) are sequentially and spaced apart in the length direction of the sensing section and are fixedly installed on the rod body of the hollow metal rod (8-1), and the wires (8-3) connected thereto pass into the interior of the hollow metal rod (8-1) through the plurality of wire passing holes and are connected with the microcontroller after passing through the communication hole; the portable acquisition terminal (9) comprises a casing (9-4), a wireless transmission module two (9-3), a processor (9-1), a storage module two (9-2) and a power module two; the wireless transmission module two (9-3), the processor (9-1), the storage module two (9-2) and the power module two are all installed in the inner cavity of the casing (9-4), and the wireless transmission module two (9-3) is connected with the wireless transmission module one by a wireless communication mode; the processor (9-1) is connected with the wireless transmission module two (9-3), the storage module two (9-2) and the power module two respectively; characterized in that The method for determining the length of the anchoring and bonding section of the rock bolt adapted to the disturbance influence of the roadway cyclic tunneling comprises the following steps: Step one: during the tunneling operation of the tunneling equipment (2) in the roadway (1), a test borehole (6) is constructed on the roof (4) of the support area close to the tunneling head (3) behind the tunneling head (3); Step two: a fixed monitoring device (8) with a size suitable for the test borehole (6) is prepared, a resin anchoring agent (7) is placed at the bottom of the test borehole (6), and the anchoring section of the hollow metal rod (8-1) is inserted into the bottom of the test borehole (6) to firmly fix the anchoring section of the hollow metal rod (8-1) to the bottom of the test borehole (6) by using the resin anchoring agent (7), and meanwhile, the multiple vibration pickup sensors (8-2) are correspondingly distributed in the anchoring and bonding section height L2 range of the rock bolt (5) anchored in the roof (4), and the shell (8-5) is exposed outside the borehole mouth. Step three: after the installation of the fixed monitoring device (8) is completed, the tunneling operation is started, and during the tunneling operation, the distance L from the fixed monitoring device (8) to the tunneling head (3) gradually increases. During the period when the tunneling head (3) is within the tunneling disturbance sensing range of the fixed monitoring device (8), each tunneling will cause cyclic loading and unloading. The cyclic vibration signals generated during the cyclic loading and unloading process propagate through the coal and rock mass to the rod of the hollow metal rod (8-1). Simultaneously, the cyclic vibration signals are collected in real time by multiple seismic sensors (8-2) and sent to the microcontroller. After receiving the cyclic vibration signals, the microcontroller adds a timestamp to the cyclic vibration signals to form time-series cyclic vibration signals with timestamps, and sends the time-series cyclic vibration signals to the storage module one for storage. The above process of collecting cyclic vibration signals continues until the distance L from the fixed monitoring device (8) to the tunneling head (3) exceeds the sensing critical distance value, and the tunneling head (3) is no longer within the sensing range of the fixed monitoring device (8). The collection of cyclic vibration signals is completed. Step four: the portable acquisition terminal (9) is used to collect signals in the underground mine. Within the effective transmission distance of the wireless signal, a wireless communication link is established between the wireless transmission module two (9-3) and the wireless transmission module one. After the wireless communication link is established, the microcontroller reads the cyclic vibration signals in the storage module one and sends them to the processor (9-1) through the wireless communication link. After receiving the cyclic vibration signals, the processor (9-1) stores them in the storage module two (9-2). Step five: after the underground signal acquisition operation is completed, the portable acquisition terminal (9) is transferred to the ground. A communication link is established between the portable acquisition terminal (9) and the industrial computer through wireless communication. After the communication link is established, the portable acquisition terminal (9) reads the cyclic vibration signals in the storage module two (9-2) and sends them to the industrial computer through the communication link. The industrial computer analyzes and processes the cyclic vibration signals to obtain vibration frequency and amplitude data, which are used as vibration excitation data. The vibration excitation data is stored in the vibration signal database. Step six: under laboratory conditions, n pieces of anchoring test pieces with different bonding lengths s are made by using seamless steel pipe, ordinary steel pipe, vaseline, mortar concrete, left-handed threaded steel anchor rod commonly used in coal mines, and resin anchoring agent, wherein n≤10; 1、 s 2、 s 3··· s n ; S61: prepare a seamless steel pipe with a length of 200-400 mm, an outer diameter of 50-55 mm, an inner diameter of 40-45 mm, and one open end and the other closed end. Prepare a common steel pipe with an outer diameter of 30 mm and a length of 300-550 mm, and coat vaseline on the outer wall of the common steel pipe. Then, insert the common steel pipe into the seamless steel pipe in the center, and make the outer end of the common steel pipe exposed outside the open end of the seamless steel pipe. S62: according to the lithology of the rock mass within the anchoring and bonding height L2 range of the anchor rod (5) in the roof (4), prepare a mortar concrete by simulating the lithology of the rock mass within the L2 range, and fill the mortar concrete in the annular gap between the common steel pipe and the seamless steel pipe. The end face of the mortar concrete after injection is flush with the open end of the seamless steel pipe, and the mortar concrete is cured for 28 days. S63: the common steel pipe is pulled out, and a mortar ring with a thickness of 10-15 mm and a test hole with a diameter of 30 mm are formed in the inner cavity of the seamless steel pipe; S64: According to the three-diameter matching principle of anchor rod diameter, drilling diameter and resin anchor diameter, the resin anchor amount required for forming the bonding length s 1、 s 2、 s 3··· s n is calculated respectively, and n parts of resin anchor and n left-handed threaded steel anchor rods with a length of 300-550 mm and a diameter of 22 mm are placed in n test holes in turn to complete the preparation of anchor test pieces with different bonding lengths s 1、 s 2、 s 3··· s n . Step seven: The low-frequency vibration simulation test system is used, and the vibration excitation data is converted to obtain the vibration signal data required in the indoor experiment according to the similarity ratio of the similar simulation experiment. Then, the prepared anchoring test piece is vibrated according to the vibration signal data. After that, the anchoring test piece is pulled by using the electro-hydraulic servo mechanics test system. The anchoring force change of the anchoring test piece, the relative displacement of the rod wall and the rupture information are obtained by comprehensively analyzing the pulling stress, displacement data and acoustic emission monitoring data obtained by using the acoustic emission monitoring system during the pulling experiment. After the test of n anchoring test pieces is completed, the weakening law of the anchoring interface bonding strength of the anchoring test pieces corresponding to different bonding lengths is compared and analyzed according to the amplitude and vibration frequency. Then, the loosening damage characteristics of the anchoring inner ring and outer ring bonding interfaces of the anchoring test pieces with different bonding lengths are determined. According to the experimental test results, the loosening damage degree w of the anchoring interface of the anchoring test piece corresponding to different bonding lengths is analyzed 1、 w 2、 w 3··· w n According to the anchoring interface damage critical value w of the anchoring test piece 临 The corresponding critical bonding length s of the anchoring interface of the anchoring test piece corresponding to different bonding lengths is obtained 临 ; Step eight: 30% to 50% s 临 According to the similarity simulation experiment, the length of the critical anchoring and bonding section of the anchor rod (5) in the actual engineering site roof (4) is obtained 临锚 This length is the length of the anchor rod anchoring and bonding section that adapts to the disturbance influence of the roadway cyclic excavation.

2. The method according to claim 1, characterized in that, The shell (8-5) is connected with the first end of the hollow metal rod (8-1) by welding.

3. The method according to claim 2, characterized in that, The distance between two adjacent vibration sensors (8-2) is 50-200 mm.

4. The method according to claim 3, characterized in that, In step three, the inductive critical distance value is 60-100 m.

5. The method according to claim 4, characterized in that, In step two, the length of the hollow metal rod (8-1) is 300-600 mm longer than the anchor rod (5) anchored in the roof (4), and the diameter of the hollow metal rod (8-1) is 30-60 mm; the length of the vibration sensor (8-2) is 30-60 mm, and the width is 20-40 mm.

6. The method according to claim 5, characterized in that, In step two, the length of the test borehole (6) is matched with the length of the hollow metal rod (8-1), and the hole diameter is 6-10 mm larger than the sum of the diameter of the hollow metal rod (8-1) and the width of the vibration sensor (8-2).

7. The method according to claim 6, characterized in that, In step seven, the anchorage specimen anchorage interface failure critical value w 临 is determined as follows: the critical debonding damage degree of the anchorage specimen anchorage interface from the loose damage to the debonding failure is defined as w 临 .

Images