Tunnel outburst prevention rock mass crack extension continuous monitoring method based on micro-seismic infield positioning

Abstract

The invention discloses a tunnel outburst prevention rock mass fracture extension continuous monitoring method based on micro-seismic infield positioning, which comprises the following steps: S1, according to the distance L between a disaster-causing structure and a tunnel face, drilling an advanced drill hole in the tunnel face, acquiring lithology and water inflow information of surrounding rock, and preliminarily determining an outburst prevention rock mass hydraulic communication area range; s2, micro-seismic sensors are arranged on the arch crown, the left wall foot and the right wall foot within the range of L / 2-2 m to L / 2 + 2 m in front of the tunnel face in the drilled advance drill hole correspondingly; s3, recording seismic source microseismic signal frequency, duration and waveform of explosive blasting, mechanical vibration and vehicle traveling, and screening microseismic signals of crack extension in the rock mass; s4, performing rock mass internal fracture extension seismic source positioning by adopting a simplex method; and S5, drawing a micro-seismic event three-dimensional model, and determining the expansion and evolution characteristics and range of the fractures in the hydraulic communication area. According to the invention, the monitoring continuity of the outburst prevention rock mass fracture evolution process of the tunnel and the positioning precision of the water inrush channel can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of tunnel engineering construction monitoring, and in particular relates to a method for continuous monitoring of crack expansion in a tunnel anti-burst rock mass based on microseismic infield positioning. Background Art

[0002] In areas with extremely complex geological environments, tunnel projects inevitably cross deep faults, karst and other adverse geological structures. If water and mud bursts occur during construction, tunnel construction safety faces huge challenges. Tunnel water and mud bursts are sudden and highly destructive geological disasters, mainly manifested by a large amount of water, mud and gravel mixture suddenly pouring into the tunnel, causing surrounding rock collapse and serious damage to the supporting structure.

[0003] The essence of water and mud burst in tunnels is that the rock mass under the combined action of construction disturbance and high water pressure causes the expansion of rock cracks, hydraulic connection and eventually the formation of water burst channels. Therefore, monitoring the expansion of cracks in the rock mass of tunnel water and mud burst is a key prerequisite for the prevention and control of water and mud burst disasters. At present, the monitoring of cracks in the rock mass of tunnel water and mud burst mainly adopts TSP seismic wave reflection method, advanced horizontal drilling and microseismic detection. TSP seismic wave reflection method can detect surrounding rock fragmentation and surrounding rock with dense joints, but it cannot detect the expansion of microcracks inside the rock mass and lacks continuity. Although advanced horizontal drilling can directly detect the lithology and water inflow of the surrounding rock in front of the face, the results are accidental, it is difficult to predict small structures, and the drilling time is long, which affects the on-site construction of the tunnel. Traditional microseismic monitoring sensors are arranged behind the face, the rock mass of water burst is located in the microseismic detection field, and the microseismic source positioning accuracy is low. In tunnel engineering, the construction site environment is complex, and the expansion and evolution process of cracks in the rock mass of water burst is affected by multiple factors such as engineering disturbance and groundwater infiltration, making it difficult to achieve accurate and rapid positioning and continuous monitoring. Summary of the invention

[0004] In order to solve the deficiencies in the above-mentioned prior art, the present invention provides a method for continuous monitoring of crack expansion in tunnel rock mass for preventing water outbursts based on microseismic infield positioning, which improves the monitoring continuity of the evolution process of cracks in tunnel rock mass for preventing water outbursts and the positioning accuracy of water inrush channels, and solves the problem of dynamic and continuous monitoring of the evolution process of crack expansion in tunnel rock mass for preventing water outbursts.

[0005] In order to achieve the above technical purpose, the technical solution adopted by the present invention is:

[0006] The method for continuous monitoring of crack expansion in rock mass of tunnel outburst prevention based on microseismic infield positioning includes the following steps:

[0007] Step S1: according to the distance L between the disaster-causing structure and the tunnel face, advance drilling is performed on the tunnel face to obtain information on the lithology of the surrounding rock and the amount of water inflow, and the hydraulic connection area and saturated softening area of ​​the anti-burst rock mass are preliminarily determined;

[0008] Step S2: In the advanced borehole that has been drilled, microseismic sensors are arranged on the arch and the left and right wall footings within the range of L / 2-2m to L / 2+2m in front of the face;

[0009] Step S3: Record the frequency, duration and waveform of microseismic signals of earthquake sources such as explosive blasting, mechanical vibration and vehicle movement, and select microseismic signals of crack expansion inside the rock mass;

[0010] Step S4: using the simplex method to locate the earthquake source of the internal fracture extension of the rock mass;

[0011] Step S5: Using the temporal and spatial distribution laws of microseismic signals of crack expansion inside the rock mass, a three-dimensional model of microseismic events is drawn to determine the evolutionary characteristics and range of crack expansion in the hydraulically connected area.

[0012] Furthermore, in step S1, three advance drilling holes are arranged, which are respectively set directly above, below left and below right in the tunnel excavation direction of the heading face, defined as the arch crown advance drilling hole, the left wall foot advance drilling hole and the right wall foot advance drilling hole. The advance drilling hole is 1m away from the excavation contour line.

[0013] Preferably, the advance drilling hole of the arch crown is located directly above the tunnel excavation direction, in the 0° direction; the advance drilling hole of the right wall foot is located at the lower right corner of the tunnel excavation direction, in the 135° direction; and the advance drilling hole of the left wall foot is located at the lower left of the tunnel excavation direction, in the 225° direction.

[0014] Preferably, the length l of the advance drilling hole is greater than the distance L / 2 between the disaster-causing structure and the tunnel face, and the angle of the advance drilling hole is greater than arctan(h+1) / L, where h is the thickness of the loose zone.

[0015] Preferably, the angle of the advance drilling is 2° to 5° outward longitudinally and 5° to 10° outward horizontally.

[0016] Furthermore, in step S2, the arrangement method of the microseismic sensors is as follows:

[0017] Insert a steel bar of L / 2 to 1 m in length into the pre-drilled hole of the arch, bury the first microseismic sensor to the end of the steel bar, ensure that the first microseismic sensor is located at the arch at L / 2 m, and reinforce it with grouting;

[0018] Insert a steel bar of (L / 2~l)+2m in length into the pre-drilled hole at the right foot of the wall, bury the second microseismic sensor at the end of the steel bar, ensure that the second microseismic sensor is located at the right foot of the wall at L / 2+2m, and reinforce it with grouting;

[0019] Insert a (L / 2~l)-2m long steel bar into the pre-drilled hole at the left wall footing, bury the third microseismic sensor to the end of the steel bar, ensure that the third microseismic sensor is located at the left wall footing at L / 2-2m, and reinforce it with grouting.

[0020] Further, in step S4, the method of using the simplex method to locate the earthquake source of the internal fracture extension of the rock mass is:

[0021] The arrival time difference of the signals obtained by the three microseismic sensors and the coordinates of the microseismic sensors are calculated. The two groups of three sensors are used as three vertices to construct the initial simplex. The objective function is shown in the following formula:

[0022]

[0023] Among them, γ i represents the residual error of the first arrival wave corresponding to the i-th microseismic sensor, (x i ,y i ,z i ) is the three-dimensional coordinate of the i-th microseismic sensor, (x0′, y0′, z0′) is the three-dimensional coordinate of the earthquake source after iteration, t0′ is the earthquake onset time, t i is the arrival time of the first arrival wave received by the microseismic sensor, v i is the propagation velocity from the microseismic source to the microseismic sensor;

[0024] The microseismic source location is the coordinate point corresponding to the minimum value of the objective function.

[0025] The beneficial effects of the present invention are:

[0026] The method for continuous monitoring of crack expansion in a tunnel outburst prevention rock mass based on microseismic infield positioning of the present invention arranges a total of three microseismic sensors around the outburst prevention rock mass in front of the heading face, so that the crack expansion inside the outburst prevention rock mass is located in the microseismic infield positioning area, which is convenient for capturing more microseismic signals and is beneficial to improving the accuracy of earthquake source positioning.

[0027] In the present invention, the microseismic sensors are arranged in a staggered manner in a plum blossom shape in the transverse direction and staggered front to back in the longitudinal direction, thereby avoiding mutual interference between the microseismic sensors.

[0028] The present invention uses the pre-drilled holes as the burying channels for burying microseismic sensors, thus avoiding repeated drilling, improving the layout efficiency, and saving the cost of monitoring layout. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1It is an implementation flow chart of the method for continuous monitoring of crack expansion in rock mass for preventing tunnel outburst based on microseismic infield positioning of the present invention;

[0031] Figure 2 This is a schematic diagram of the hydraulic connection area of ​​the tunnel rock mass to prevent outbursts;

[0032] Figure 3 This is the right view of the advance drilling;

[0033] Figure 4 Right view of the microseismic sensor arrangement;

[0034] Figure 5 Front view of the microseismic sensor arrangement;

[0035] In the figure: 101 is a first microseismic sensor; 102 is a second microseismic sensor; 103 is a third microseismic sensor. DETAILED DESCRIPTION

[0036] To make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The components of the embodiments of the present application generally described and shown in the drawings here can be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present application provided in the drawings is not intended to limit the scope of the application claimed for protection, but merely represents the selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians of the art without making creative work are within the scope of protection of the present application.

[0037] A method for continuous monitoring of crack expansion in rock mass for preventing tunnel outburst based on microseismic in-field positioning, such as Figure 1 As shown, the following steps are included:

[0038] Step S1: According to the distance L between the disaster-causing structure and the tunnel face, advance boreholes are drilled at the tunnel face to obtain information such as the lithology of the surrounding rock and the amount of water inflow. By observing the changes in the core and water volume, it is determined whether the amount of water inflow changes suddenly. If not, the borehole is deepened. If so, the hydraulic connection area and saturated softening area of ​​the anti-burst rock mass are preliminarily determined. The continuous monitoring of the expansion of cracks in the tunnel anti-burst rock mass is mainly aimed at the hydraulic connection area.

[0039] Tunnel anti-outburst rock mass hydraulic connection area Figure 2 As shown in the figure, it refers to the area where the internal cracks of the anti-burst rock mass gradually expand under the combined action of groundwater infiltration and excavation disturbance. With the further excavation of the tunnel, the cracks are connected to form water gushing channels, the tunnel face becomes unstable, and water and mud burst disasters occur.

[0040] Specifically, advance drilling holes are set at the top (0° direction), the lower left (225° direction) and the lower right (135° direction) of the tunnel excavation direction, 1 m away from the excavation contour line, and recorded as the arch advance drilling hole, the left wall foot advance drilling hole and the right wall foot advance drilling hole, respectively. Rock sampling is carried out, and the drilling time, drill sticking and water gushing during the horizontal drilling process are recorded; Figure 3 , Figure 4 , Figure 5 As shown in the figure, the length of the advance drilling hole l should be greater than the distance between the disaster-causing structure and the tunnel face L / 2, the angle of the advance drilling hole should be greater than arctan(h+1) / L, h is the thickness of the loose zone, and the angle of the advance drilling hole is usually 2°~5° longitudinally outward and 5°~10° horizontally outward.

[0041] Step S2: In the advanced borehole that has been drilled, microseismic sensors are arranged on the arch and the left and right wall footings within the range of L / 2-2m to L / 2+2m in front of the face, so that the internal crack expansion of the anti-burst rock mass is located in the microseismic inner field positioning area, such as Figure 4 , Figure 5 As shown in the figure, the microseismic infield positioning area refers to the interior of the sensor combination space. Since the arrival time difference of the infield microseismic signal is small, the positioning accuracy and stability are relatively high.

[0042] Specifically, a steel bar of L / 2 to 1m in length is inserted into the pre-drilled hole of the arch, and the first microseismic sensor 101 is buried to the end of the steel bar to ensure that the first microseismic sensor is located at the arch at L / 2m, and grouting is performed for reinforcement; a steel bar of (L / 2 to 1)+2m in length is inserted into the pre-drilled hole of the arch, and the second microseismic sensor 102 is buried to the end of the steel bar to ensure that the second microseismic sensor is located at the right wall foot at L / 2+2m, and grouting is performed for reinforcement; a steel bar of (L / 2 to 1)-2m in length is inserted into the pre-drilled hole of the arch, and the third microseismic sensor 103 is buried to the end of the steel bar to ensure that the third microseismic sensor is located at the left wall foot at L / 2-2m, and grouting is performed for reinforcement.

[0043] The first microseismic sensor 101 is arranged at the arch at L / 2m (directly above the tunnel excavation direction, 0° direction), the second microseismic sensor 102 is arranged at the left wall foot at L / 2-2m (lower left in the tunnel excavation direction, 225° direction), and the third microseismic sensor 103 is arranged at the right wall foot at L / 2+2m (lower right in the tunnel excavation direction, 135° direction); the three microseismic sensors are staggered in a plum blossom shape in the horizontal direction and staggered by 2m front and back in the longitudinal direction to prevent mutual interference between the microseismic sensors.

[0044] Step S3: respectively record the frequency, duration and waveform of the microseismic signals of the earthquake sources of explosive blasting, mechanical vibration and vehicle movement, and select the microseismic signals of the expansion of cracks inside the rock mass.

[0045] In addition to the microseismic signals of the expansion of cracks inside the rock, the microseismic signals that can be monitored during tunnel construction also include noise such as explosive blasting, mechanical vibration and vehicle movement, which need to be eliminated.

[0046] Step S4: Use the simplex method to locate the earthquake source of the internal crack expansion of the rock mass. The specific method is: calculate the arrival time difference of the signals obtained between the sensors and the coordinates of the sensors. Two groups of 3 sensors in total are used as 3 vertices to construct the initial simplex. The objective function is shown in the following formula:

[0047]

[0048] Among them, γ i represents the residual error of the first arrival wave corresponding to the i-th microseismic sensor, (x i ,y i ,z i ) is the three-dimensional coordinate of the i-th microseismic sensor, (x0′, y0′, z0′) is the three-dimensional coordinate of the earthquake source after iteration, t0′ is the earthquake onset time, t i is the arrival time of the first arrival wave received by the microseismic sensor, v i is the propagation velocity from the microseismic source to the microseismic sensor.

[0049] The microseismic source location is the coordinate point corresponding to the minimum value of the objective function.

[0050] Step S5: Using the temporal and spatial distribution laws of microseismic signals of fracture extension inside the rock mass, a three-dimensional model of microseismic events is drawn to determine the evolutionary characteristics and range of fracture extension in the hydraulically connected area.

[0051] Of course, the present invention may have many other embodiments. Without departing from the spirit and essence of the present invention, technicians familiar with the field may make various corresponding changes and deformations based on the present invention, but these corresponding changes and deformations should all fall within the scope of protection of the claims attached to the present invention.

Claims

1. A method for continuous monitoring of crack expansion in rock mass for preventing tunnel outburst based on microseismic infield positioning, characterized by: The following steps are involved: Step S1: according to the distance L between the disaster-causing structure and the tunnel face, advance drilling is performed on the tunnel face to obtain information on the lithology of the surrounding rock and the amount of water inflow, and the hydraulic connection area and saturated softening area of ​​the anti-burst rock mass are preliminarily determined; Step S2: In the advanced borehole that has been drilled, microseismic sensors are arranged on the arch and the left and right wall footings within the range of L / 2-2m to L / 2+2m in front of the face; Step S3: Record the frequency, duration and waveform of microseismic signals of earthquake sources such as explosive blasting, mechanical vibration and vehicle movement, and select microseismic signals of crack expansion inside the rock mass; Step S4: using the simplex method to locate the earthquake source of the internal fracture extension of the rock mass; Step S5: Using the temporal and spatial distribution laws of microseismic signals of crack expansion inside the rock mass, a three-dimensional model of microseismic events is drawn to determine the evolutionary characteristics and range of crack expansion in the hydraulically connected area.

2. The method for continuous monitoring of rock mass crack expansion in tunnel outburst prevention based on microseismic infield positioning according to claim 1 is characterized by: In step S1, three advance drilling holes are arranged, which are respectively set above, below left and below right of the tunnel excavation direction of the heading face, and are respectively recorded as the arch advance drilling hole, the left wall foot advance drilling hole and the right wall foot advance drilling hole. The advance drilling hole is 1m away from the excavation contour line.

3. The method for continuous monitoring of crack expansion in rock mass for preventing tunnel outburst based on microseismic infield positioning according to claim 2 is characterized by: The advance drilling hole of the arch crown is located directly above the tunnel excavation direction, in the 0° direction; the advance drilling hole of the right wall foot is located at the lower right corner of the tunnel excavation direction, in the 135° direction; the advance drilling hole of the left wall foot is located at the lower left corner of the tunnel excavation direction, in the 225° direction.

4. The method for continuous monitoring of crack expansion in rock mass for preventing tunnel outburst based on microseismic infield positioning according to claim 2 is characterized by: The length l of the advance drilling hole is greater than the distance L / 2 between the disaster-causing structure and the tunnel face, and the angle of the advance drilling hole is greater than arctan(h+1) / L, where h is the thickness of the loose zone.

5. The method for continuous monitoring of crack expansion in rock mass for preventing tunnel outburst based on microseismic infield positioning according to claim 4 is characterized by: The angle of the advance drilling is 2° to 5° outward longitudinally and 5° to 10° outward horizontally.

6. The method for continuous monitoring of crack expansion in rock mass for preventing tunnel outburst based on microseismic infield positioning according to claim 2 is characterized by: In step S2, the arrangement method of the microseismic sensors is as follows: Insert a steel bar of L / 2 to 1 m in length into the pre-drilled hole of the arch, bury the first microseismic sensor to the end of the steel bar, ensure that the first microseismic sensor is located at the arch at L / 2 m, and reinforce it with grouting; Insert a steel bar of (L / 2~l)+2m in length into the pre-drilled hole at the right foot of the wall, bury the second microseismic sensor at the end of the steel bar, ensure that the second microseismic sensor is located at the right foot of the wall at L / 2+2m, and reinforce it with grouting; Insert a (L / 2~l)-2m long steel bar into the pre-drilled hole at the left wall footing, bury the third microseismic sensor to the end of the steel bar, ensure that the third microseismic sensor is located at the left wall footing at L / 2-2m, and reinforce it with grouting.

7. The method for continuous monitoring of crack expansion in rock mass for preventing tunnel outburst based on microseismic infield positioning according to claim 1 is characterized by: In step S4, the method of using the simplex method to locate the earthquake source of the internal fracture extension of the rock mass is: The arrival time difference of the signals obtained by the three microseismic sensors and the coordinates of the microseismic sensors are calculated. The two groups of three sensors are used as three vertices to construct the initial simplex. The objective function is shown in the following formula: Among them, γ i represents the residual error of the first arrival wave corresponding to the i-th microseismic sensor, (xi,yi,zi) is the three-dimensional coordinate of the i-th microseismic sensor, (x0′,y0′,z0′) is the three-dimensional coordinate of the earthquake source after iteration, t0′ is the earthquake source onset time, t i is the arrival time of the first arrival wave received by the microseismic sensor, v i is the propagation velocity from the microseismic source to the microseismic sensor; The microseismic source location is the coordinate point corresponding to the minimum value of the objective function.

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