CN111859712B - Ground advance pre-control method for rock burst of coal mine - Google Patents

Abstract

The invention relates to a method for advanced pre-control of coal mine impact ground pressure. First, the impact tendency of coal and rock masses is identified before coal seam mining, and then the impact hazard of the mine is predicted based on the comprehensive index method, and the dangerous area is demarcated, and ground fracturing technology is used to fracture the rock formations in the dangerous area. During the mining process of the working face, a microseismic monitoring system is used to monitor the energy release intensity of the overlying rock formation in real time. Based on the monitoring results, hydraulic fracturing technology is used on the ground to further fracture and weaken the rock formation to prevent and control rock bursts. This method is scientific and reliable, with comprehensive technical means. It controls the source of impact ground pressure from the source and has broad application prospects.

Description

A method for advanced pre-control of coal mine rock burst ground

Technical field

The invention relates to the technical field of coal mining, and in particular to a method for advanced pre-control of coal mine impact ground pressure.

Background technique

During the underground mining process of coal mines, rockbursts are a major disaster that threatens the safety of coal mining. They are also the most difficult to control and cause the highest casualty rate. The number of rockbursts is also increasing year by year.

Domestic and foreign scholars have done a lot of work on the occurrence mechanism of rock bursts. Studies have shown that stress accumulation and energy release caused by geodynamic environment, mining disturbance, etc. are the fundamental reasons for inducing rock bursts, and rock bursts mostly occur in hard rock formations. In roof mining areas, due to the high strength and thickness of the roof, the roof is not easily broken during the mining process, causing energy accumulation and easily inducing rock bursts. However, at present, there has been no breakthrough in the control of rock pressure at home and abroad. The control of this type of disaster is mostly limited to passive defense in the underground range, which cannot be treated from the source. The death of people and the loss of assets caused by the disaster have never been controlled. Seriously affect the safety production of mines.

Therefore, how to provide a method for ground fracturing to control impact pressure before mining has become an urgent problem in this field that needs to be solved.

Contents of the invention

The purpose of this invention is to provide a method for advanced ground pre-control of coal mine rock bursts. By predicting the occurrence tendency of rock bursts, reasonably selecting ground fracturing control means, and monitoring the overlying rock breaking impact strength in real time during the mining process, it is possible to achieve Conduct targeted control at fixed points to avoid the occurrence of rock bursts, prevent and control impact disasters from the source, and achieve safe mining in mines.

In order to achieve the above objects, the present invention provides the following solutions:

Before coal seam mining, drill holes in the coal seam and its roof and floor to take coal and rock mass cores, measure the impact tendency of the coal and rock mass core in real time, and obtain the measurement results; the measurement results are either no impact tendency or there is impact tendency;

If the measurement result shows that there is a tendency to impact, advanced fracturing control is performed. The advanced fracturing control specifically includes:

Use the comprehensive index method to determine the impact mine pressure hazard level assessment index W _t1 , and determine whether the mine has impact risk based on the impact mine pressure hazard level assessment index W _t1 ;

When there is a risk of impact in a mine, a numerical simulation model is established based on the mining geological conditions of the working face;

According to the numerical simulation model, the dangerous area of the mine is determined, and the dangerous area of the mine is the simulated fracturing position;

Use surface fracturing technology to fracturing the pre-fracturing position in the actual mine corresponding to the simulated fracturing position.

Optionally, the comprehensive index method is used to determine the calculation formula for the impact mine pressure hazard level assessment index W _t1 :

In the formula: _Wi is the actual evaluation index of the i-th influencing factor; _Wimax is the maximum evaluation index of the i-th influencing factor in the table; n _i is the number of influencing factors; the influencing factors are the same horizontal coal seam in the mining area The historical number of occurrences of impact mine pressure n, the mining depth h, the distance between the hard thick rock layer in the overlying fissure zone and the coal seam and the ratio of the coal seam thickness d, the ratio of the stress increment caused by the structure in the mining area to the normal stress value γ, the thickness of the roof rock layer One or more of the characteristic parameters L _st , coal uniaxial compressive strength R _c and coal elastic energy index W _ET .

Optionally, the method of judging whether a mine has impact risk based on the impact mine pressure risk level assessment index specifically includes:

If W _t1 ≤0.25, it is deemed that there is no impact risk;

If 0.25＜W _t1 ≤0.5, it is considered to be a weak impact hazard;

If 0.5＜W _t1 ≤0.75, it is considered to be a medium impact hazard;

If W _t1 >0.75, it is determined to be a strong impact risk; the impact risk is a weak impact risk, a medium impact risk and/or a strong impact risk.

Optionally, the establishment of a numerical simulation model based on the mining geological conditions of the working face specifically includes:

Obtain the mining geological conditions of the working face;

Set the mining speed of the working face;

A numerical simulation model is established based on the mining geological conditions of the working face, the mining speed of the working face and the actual size of the mine at a ratio of 1:1.

Optionally, the dangerous area of the mine is determined based on the numerical simulation model, and the dangerous area of the mine is the simulated fracturing location, specifically including:

Use the numerical simulation model to simulate the mining process, and record the stress accumulation area of the overlying rock layer, the stress concentration coefficient of the overlying rock layer stress accumulation area and the energy release intensity of the overlying rock layer fracture during the simulated mining process;

According to the energy release intensity, the layer of the overlying rock layer and the location of the rock layer breakage that are greater than or equal to the lower limit of the simulated energy release intensity threshold range are determined, and recorded as the simulated fracturing position.

Optionally, the above-mentioned use of ground fracturing technology to fracturing the pre-fracturing position in the actual mine corresponding to the simulated fracturing position specifically includes:

It is determined that the layer of the overlying rock layer and the position of the rock layer break where the energy release intensity is within the simulated energy release intensity threshold range or the stress concentration coefficient is within the simulated stress concentration coefficient range are recorded as vertical fracturing layers respectively. and vertical fracturing locations;

Fracturing the vertical fracturing location using a vertical well drilled to the vertical fracturing layer;

Determine the layer of the overlying rock layer and the position of the rock layer break where the energy release intensity is greater than the upper limit of the simulated energy release intensity threshold range or the stress concentration coefficient is greater than the upper limit of the simulated stress concentration coefficient range, and record them as levels respectively. Fracturing horizons and horizontal fracturing locations;

Horizontal wells drilled to the horizontal fracturing layer are used to perform fracturing on the horizontal fracturing location.

Optionally, after the surface fracturing process is used to fracturing the pre-fracturing position in the actual mine corresponding to the simulated fracturing position, it also includes:

Before coal seam mining, a microseismic monitoring system is deployed in the advance tunnel to monitor the energy release intensity of the overlying rock formation in real time;

During the mining process, determine the layer of the overlying rock layer where the measured energy release intensity obtained by monitoring is greater than or equal to the measured energy release intensity threshold, and record it as the hydraulic fracturing layer;

At a location 40 to 100m ahead of the hydraulic fracturing layer, a hydraulic fracturing well is used to fracture the ground; until the measured energy release intensity is less than the measured energy release intensity threshold, the fracturing control operation is completed.

Optionally, the microseismic monitoring system is a plurality of microseismic monitoring equipment probes, and the several microseismic monitoring equipment probes are evenly installed within a range of 100m from the working face to the leading tunnel.

Optionally, the determination of the impact tendency of coal and rock mass is based on the national standard: GB/T25217.1-2010 "Method for determination of classification and index of impact tendency of roof rock layers".

According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

1) The comprehensive index method is used to predict the risk of rock bursts, fully considering all the key factors that affect the occurrence of rock bursts, and the prediction results are scientific and reliable;

2) The numerical simulation model parameters are all taken from the site, which is true and reliable. The numerical simulation model is established according to the on-site mining geological conditions at a ratio of 1:1, ensuring the accuracy of the prediction results; at the same time, the prediction model is easy to establish and has strong operability;

3) Ground fracturing technology is selectively applied based on predicted results, avoiding blindness in technology application and unnecessary engineering workload, and maximizing the advantages of each technology;

4) Surface fracturing technology is used to control the fracturing of the target layer. Compared with traditional downhole control technology, it has strong operability, a large control range, and good fracturing effects. It truly achieves active control of rock pressure shocks from the source. It has broad application prospects.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some of the drawings of the present invention. Embodiments, for those of ordinary skill in the art, other drawings can also be obtained based on these drawings without exerting creative efforts.

Figure 1 is a flow chart of advanced pre-control of coal mine rock burst ground provided by the embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts fall within the scope of protection of the present invention.

The purpose of the present invention is to provide a method for advanced ground pre-control of coal mine rockbursts, by predicting the occurrence tendency and dangerous areas of rockbursts in advance, and using ground fracturing technology to control fracturing in advance; during the mining process, the microseismic monitoring system is used in real time The energy release intensity of the overlying rock formation is monitored, and based on the monitoring results, hydraulic fracturing technology is used on the ground to further weaken the overlying rock formation and prevent and control the impact of ground pressure from the source.

In order to make the above objects, features and advantages of the present invention more obvious and understandable, the present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments.

Example 1:

As shown in Figure 1, the coal mine rock burst ground advanced pre-control method provided by this embodiment includes the following steps:

Step 1: Before coal seam mining, drill holes in the coal seam and its roof and floor to take the coal rock core, measure the impact tendency of the coal rock core, and obtain the measurement result; the measurement result is no impact tendency or impact tendency.

Specifically, according to the measurement results, the impact tendency is divided into three grades: no impact tendency, weak impact tendency and strong impact tendency; the impact tendency is weak impact tendency or strong impact tendency.

The determination of the impact tendency of coal and rock mass is based on the national standard: GB/T25217.1-2010 "Method for determination of classification and index of impact tendency of roof rock layers".

If the measurement result is no impact tendency, no control is required; if the measurement result is weak impact tendency or strong impact tendency, then control is performed according to the following steps.

Step 2: If the measurement result shows a weak impact tendency or a strong impact tendency, perform advanced fracturing control. The advanced fracturing control specifically includes:

The comprehensive index method is used to determine the impact mine pressure hazard level assessment index W _t1 , and determine whether the mine has impact risk based on the impact mine pressure hazard level assessment index W _t1 .

The calculation formula of the impact mine pressure hazard level assessment index W _t1 is:

In the formula: _Wi is the actual evaluation index of the i-th influencing factor; _Wimax is the maximum evaluation index of the i-th influencing factor in the table; n _i is the number of influencing factors; the influencing factors are the same horizontal coal seam in the mining area The historical number of occurrences of impact mine pressure n, the mining depth h, the distance between the hard thick rock layer in the overlying fissure zone and the coal seam and the ratio of the coal seam thickness d, the ratio of the stress increment caused by the structure in the mining area to the normal stress value γ, the thickness of the roof rock layer One or more of the characteristic parameters L _st , coal uniaxial compressive strength R _c and coal elastic energy index W _ET .

Specifically, if W _t1 ≤0.25, it is deemed to have no impact risk;

If 0.25＜W _t1 ≤0.5, it is considered to be a weak impact hazard;

If 0.5＜W _t1 ≤0.75, it is considered to be a medium impact hazard;

If W _t1 >0.75, it is considered to be a strong impact hazard;

The impact risk is a weak impact risk, a medium impact risk and/or a strong impact risk.

Among them, when the comprehensive index method is used to determine the risk level of impact mine pressure, the evaluation index of each influencing factor is selected according to the following table.

Dangerous state factors and indexes of impact mine pressure

For example, there are four factors that influence the mining of a certain coal mine, namely the historical number of occurrences of coal seam impact pressure n at the same level, the mining depth h, the distance between the hard thick rock layer in the overlying fissure zone and the coal seam and the ratio of the coal seam thickness d and the mining area. The ratio γ between the stress increment caused by the structure and the normal stress value. Among them, the actual evaluation index of the historical number of occurrences of coal seam impact pressure n at the same level is 2; the actual evaluation index of the mining depth h is 3; the actual evaluation index of the distance between the hard thick rock layer in the overlying fissure zone and the coal seam and the ratio of the coal seam thickness d is 3; the actual evaluation index of the normal stress value ratio γ is 1. The maximum evaluation index of these four factors is 3. Then, by substituting each value into the formula, we can get the impact mine pressure risk level assessment index W _t1 = 0.75, which is considered to be a medium impact risk. The present invention fully considers all the key factors affecting the occurrence of rock burst through the comprehensive index method, so that the risk of rock burst in the mine can be accurately predicted.

If the mine has no impact risk, no control is required; if the mine has weak impact risk, medium impact risk, and/or strong impact risk, control shall be carried out according to the following steps.

Step 3: When the mine has impact risk, establish a numerical simulation model based on the mining geological conditions of the working face.

The establishment process of the numerical simulation model may specifically include:

Obtain the mining geological conditions of the working face;

Set the mining speed of the working face;

A numerical simulation model is established based on the mining geological conditions of the working face, the mining speed of the working face and the actual size of the mine at a ratio of 1:1. The simulated working face mining speed in the numerical simulation model is set based on the actual mining speed on site.

Since the parameters of the numerical simulation model of the present invention are all taken from the site, the data is true and reliable, which not only ensures the accuracy of the simulation data but also ensures the accuracy of the prediction results, and provides a favorable basis for subsequent mine mining.

Step 4: Determine the dangerous area of the mine based on the numerical simulation model, and the dangerous area of the mine is the simulated fracturing location.

In this embodiment, step 4 may specifically include:

Step 4.1: Use the numerical simulation model to simulate the mining process, and record the stress accumulation area of the overlying rock layer, the stress concentration coefficient of the overlying rock layer stress accumulation area and the energy release intensity of the overlying rock layer fracture during the simulated mining process;

Step 4.2: Determine the layer of the overlying rock layer and the location of the rock layer breakage that are greater than or equal to the lower limit of the simulated energy release intensity threshold range based on the energy release intensity, and record them as the simulated fracturing positions.

In practical applications, the lower limit of the simulated energy release intensity threshold range can be set to 1*10 ⁶ J. When the breaking energy of the overlying rock layer reaches more than 1*10 ⁶ J, the layer of the overlying rock layer and the rock layer breaking are recorded. s position.

Step 5: Use surface fracturing technology to fracturing the pre-fracturing position in the actual mine corresponding to the simulated fracturing position.

In this embodiment, step 5 may specifically include:

Step 5.1: Determine the layer of the overlying rock layer and the location of the rock layer break where the energy release intensity is within the simulated energy release intensity threshold range or the stress concentration coefficient is within the simulated stress concentration coefficient range, and record them as vertical pressures respectively. fracture layer and vertical fracturing position.

Step 5.2: Use the vertical well drilled to the vertical fracturing layer to fracturing the vertical fracturing location.

Among them, the simulated energy release intensity threshold range can be set to 10 ⁶ ~ 10 ⁷ J, and the simulated stress concentration coefficient range can be set to 1 ~ 2. Then the upper limit determined based on the simulated energy release intensity threshold range or the simulated stress concentration coefficient range Vertical wells can be used for fracturing at the layers of overlying rock strata and at locations where rock strata are broken to adapt to the fracturing conditions in the area and reduce unnecessary engineering workload.

In this embodiment, step 5 may also include:

Step 5.3: Determine the layer of the overlying rock layer and the location of the rock layer break where the energy release intensity is greater than the upper limit of the simulated energy release intensity threshold range or the stress concentration coefficient is greater than the upper limit of the simulated stress concentration coefficient range, respectively. It is recorded as horizontal fracturing layer and horizontal fracturing position.

Step 5.4: Use the horizontal well drilled to the horizontal fracturing layer to fracturing the horizontal fracturing location.

In practical applications, for the overlying rock strata where the stress concentration coefficient is greater than 2 in the stress accumulation area, or where the energy release intensity of the overlying rock stratum rupture is above 10 ⁷ J, and where the rock stratum is broken, ground compression is required. When fracturing, horizontal wells can be used for fracturing, and the extension direction of the horizontal section of the horizontal well is parallel to the mining direction of the working face. This fracturing technology is more suitable for the stress accumulation area of the overlying rock strata. It makes full use of horizontal fracturing technology, reduces unnecessary engineering volume, and also ensures effective control of the impact ground pressure in this area.

The above steps in this embodiment are a process of simulating fracturing, which can be used alone or in combination with the rockburst pre-control method in the actual mining process. Of course, the rockburst pre-control method in the actual mining process can also be used. The technical solutions of the permutations and combinations of the pre-control methods for impact rock pressure before mining and during mining are all within the protection scope of the present invention when used alone. The following is a detailed introduction to the rockburst pre-control method during mining (here, the description is based on the above-mentioned rockburst pre-control method before mining):

Step 6: Before coal seam mining, a microseismic monitoring system is deployed in the advance tunnel to monitor the energy release intensity of the overlying rock layer in real time;

Among them, the microseismic monitoring system is a number of microseismic monitoring equipment probes, and the several microseismic monitoring equipment probes are evenly installed within a range of 100m from the working face to the leading tunnel. Specifically, a microseismic monitoring equipment probe can be deployed every 10m. In this way, advanced tunnels at different locations can be monitored to ensure real-time and comprehensive monitoring.

Step 7: During the mining process, determine the layer of the overlying rock layer where the measured energy release intensity obtained by monitoring is greater than or equal to the measured energy release intensity threshold, and record it as the hydraulic fracturing layer.

Step 8: Use a hydraulic fracturing well to fracturing the ground at a location 40 to 100m ahead of the hydraulic fracturing layer; until the measured energy release intensity is less than the measured energy release intensity threshold, fracturing control is completed. Operation.

It should be noted that based on mining experience, the measured energy release intensity threshold in this embodiment can be set to 1*10 ⁵ J. Of course, with changes in geology, the measured energy release intensity threshold can also change accordingly. Here No specific restrictions are made.

In summary, compared with traditional underground control technology, the present invention predicts the occurrence tendency and dangerous areas of rock pressure in advance, and uses surface fracturing technology to control fracturing in advance; during the mining process, the overlying rock formation breakage is monitored in real time through the microseismic monitoring system According to the monitoring results, hydraulic fracturing technology is used on the ground to further weaken the overlying rock formations and truly achieve active control of the impact of ground pressure from the source. This method is scientific and reliable, has comprehensive technical means, and has broad application prospects.

This article uses specific examples to illustrate the principles and implementation methods of the present invention. The description of the above embodiments is only used to help understand the method and the core idea of the present invention; at the same time, for those of ordinary skill in the art, according to the present invention There will be changes in the specific implementation methods and application scope of the ideas. In summary, the contents of this description should not be construed as limitations of the present invention.

Claims (7)

1. A method for advanced pre-control of coal mine rock burst ground, which is characterized by including the following steps: Before coal seam mining, drill holes in the coal seam and its roof and floor to take coal and rock mass cores, measure the impact tendency of the coal and rock mass core in real time, and obtain the measurement results; the measurement results are either no impact tendency or there is impact tendency; If the measurement result shows that there is a tendency to impact, advanced fracturing control is performed. The advanced fracturing control specifically includes: Use the comprehensive index method to determine the impact mine pressure hazard level assessment index W _t1 , and determine whether the mine has impact risk based on the impact mine pressure hazard level assessment index W _t1 ; When there is a risk of impact in a mine, a numerical simulation model is established based on the mining geological conditions of the working face; According to the numerical simulation model, the dangerous area of the mine is determined, and the dangerous area of the mine is the simulated fracturing position; Use surface fracturing technology to fracturing the pre-fracturing position in the actual mine corresponding to the simulated fracturing position; The establishment of a numerical simulation model based on the mining geological conditions of the working face specifically includes: Obtain the mining geological conditions of the working face; Set the mining speed of the working face; Establish a numerical simulation model based on the mining geological conditions of the working face, the mining speed of the working face and the actual size of the mine at a ratio of 1:1; According to the numerical simulation model, the dangerous area of the mine is determined, and the dangerous area of the mine is the simulated fracturing position, specifically including: Use the numerical simulation model to simulate the mining process, and record the stress accumulation area of the overlying rock layer, the stress concentration coefficient of the overlying rock layer stress accumulation area and the energy release intensity of the overlying rock layer fracture during the simulated mining process; According to the energy release intensity, the layer of the overlying rock layer and the location of the rock layer breakage that are greater than or equal to the lower limit of the simulated energy release intensity threshold range are determined, and recorded as the simulated fracturing position. 2. A coal mine rock burst ground advanced pre-control method according to claim 1, characterized in that the comprehensive index method is used to determine the calculation formula for the rock burst hazard level assessment index W _t1 : In the formula: _Wi is the actual evaluation index of the i-th influencing factor; _Wimax is the maximum evaluation index of the i-th influencing factor in the table; n _i is the number of influencing factors; the influencing factors are the same horizontal coal seam in the mining area The historical number of occurrences of impact mine pressure n, the mining depth h, the distance between the hard thick rock layer in the overlying fissure zone and the coal seam and the ratio of the coal seam thickness d, the ratio of the stress increment caused by the structure in the mining area to the normal stress value γ, the thickness of the roof rock layer One or more of the characteristic parameters L _st , coal uniaxial compressive strength R _c and coal elastic energy index W _ET . 3. A coal mine rock burst ground advanced pre-control method according to claim 1, characterized in that the judgment of whether the mine has a rock burst hazard according to the rock burst hazard grade assessment index specifically includes: If W _t1 ≤0.25, it is deemed that there is no impact risk; If 0.25＜W _t1 ≤0.5, it is considered to be a weak impact hazard; If 0.5＜W _t1 ≤0.75, it is considered to be a medium impact hazard; If W _t1 >0.75, it is determined to be a strong impact risk; the impact risk is a weak impact risk, a medium impact risk and/or a strong impact risk. 4. A method for ground advance pre-control of coal mine rock bursting according to claim 1, characterized in that the ground fracturing process is used to fracturing the pre-fracturing position in the actual mine corresponding to the simulated fracturing position, Specifically include: It is determined that the layer of the overlying rock layer and the position of the rock layer break where the energy release intensity is within the simulated energy release intensity threshold range or the stress concentration coefficient is within the simulated stress concentration coefficient range are recorded as vertical fracturing layers respectively. and vertical fracturing locations; Fracturing the vertical fracturing location using a vertical well drilled to the vertical fracturing layer; Determine the layer of the overlying rock layer and the position of the rock layer break where the energy release intensity is greater than the upper limit of the simulated energy release intensity threshold range or the stress concentration coefficient is greater than the upper limit of the simulated stress concentration coefficient range, and record them as levels respectively. Fracturing horizons and horizontal fracturing locations; Horizontal wells drilled to the horizontal fracturing layer are used to perform fracturing on the horizontal fracturing location. 5. A coal mine rock burst ground advanced pre-control method according to claim 4, characterized in that the pre-fracturing position in the actual mine corresponding to the simulated fracturing position is carried out using the ground fracturing process. After fracturing, it also includes: Before coal seam mining, a microseismic monitoring system is deployed in the advance tunnel to monitor the energy release intensity of the overlying rock formation in real time; During the mining process, determine the layer of the overlying rock layer where the measured energy release intensity obtained by monitoring is greater than or equal to the measured energy release intensity threshold, and record it as the hydraulic fracturing layer; At a location 40 to 100m ahead of the hydraulic fracturing layer, a hydraulic fracturing well is used to fracture the ground; until the measured energy release intensity is less than the measured energy release intensity threshold, the fracturing control operation is completed. 6. A method for advanced pre-control of coal mine rock burst ground according to claim 5, characterized in that the microseismic monitoring system is a plurality of microseismic monitoring equipment probes, and the several microseismic monitoring equipment probes are evenly installed on the ground. Within 100m from the working face to the leading tunnel. 7. A coal mine rock burst ground advanced pre-control method according to claim 1, characterized in that the measurement of the impact tendency of the real-time coal and rock mass core is based on the national standard: GB/T25217.1-2010 "Roof Plate" "Method for determination of classification and index of rock formation impact tendency" determination.