CN102759337B - Method for monitoring dynamic fractures of underground mining working face - Google Patents

Abstract

The invention relates to a method for monitoring dynamic fractures in well mining working faces, which can accurately and completely obtain geometric information of mining fractures and their development process. The method includes: laying out the fissure monitoring datum line, establishing a mathematical model between the position of the front end of the working face and the position of the working face, finding the corresponding best observed crack through the mathematical model, conducting continuous dynamic observation, and obtaining the change of the width of the crack Data, draw the change trend diagram of the fracture width with respect to the position of the working face, so as to analyze the characteristics and time node information of all the typical stages experienced in the whole process from the generation of the front crack to the complete closure, and summarize and refine the complete dynamic fracture of the front of the working face. Life cycle, and then provide a time benchmark and technical support for the study of the impact mechanism of coal mining on the land ecological environment and its self-repair cycle in this area.

Description

A monitoring method for dynamic cracks in mining face

technical field

The invention relates to the technical field of environmental monitoring, in particular to a monitoring method for dynamic cracks at the front end of an underground mining working face in a sandstorm area.

Background technique

The main mining area in the wind-sand area has unique soil physical and chemical properties. For example, in the Shendong area of China, due to desertification and potential desertification, the soil particles in the wind-sand area are relatively coarse, loose and unstructured, and have poor water storage and fertilizer retention. The existing thin topsoil layer disintegrates quickly, and the soil particles are easily dispersed. In addition, the physical and chemical properties of the soil interact with harsh climatic factors such as heavy rain and strong wind, causing serious soil erosion. These conditions and factors ultimately lead to a very fragile ecological environment in the mining area.

Relevant studies have shown that coal mining has led to increased landscape fragmentation in some areas of this type, dry wells, lower groundwater levels, and a drop in the central water level of up to 2-3m, decreased soil water content, reduced vegetation coverage, and increased soil erosion. . The law and mechanism of the impact of high-intensity mining on the land in this area, the temporal and spatial variation of land damage (such as ground fissures) and the resulting changes in surface water, which of the land damage is temporary and which is permanent, and the nature of the land The key issues such as the restoration ability have not been systematically studied, which ultimately leads to the inability to provide a scientific decision-making basis for the selection of restoration measures for the disturbed ecological environment in the area.

The life cycle of surface cracks refers to the whole process of their existence on the surface from creation to complete closure. The monitoring of this process is the premise and basis for studying the spatio-temporal evolution of soil porosity, soil nutrients, and soil water content before and after coal mining disturbance in this area, and is an important part of studying the land damage mechanism in this area.

At present, relevant research is mainly aimed at the mechanism of ground fissures, the distribution of ground fissures, and the theoretical research on the geometric information of ground fissures. Some documents involve the content of ground fissure monitoring:

Using the theory of soil compression, Wang Jinzhuang qualitatively analyzed the function model of crack width, and pointed out that under the same conditions, there is a linear relationship between the ratio of crack d and spacing L and the horizontal deformation of the surface (please give the references corresponding to Wang Jinzhuang, thank you); Wu Kan proposed a calculation method for the dynamic strain component at any point on the surface caused by mining. Combining the deformation of the surface point with the mechanical properties of the surface soil, he proposed a dynamic calculation model for the distribution of cracks on the surface, and pointed out that the time for cracks to appear on the surface is approximately Equal to T=2B/v, wherein B is the width of the fracture zone above the mining face, and v is the average advancing speed of the working face (Wu Kan, Hu Zhenqi, Chang Jiang, Ge Jiaxin. The distribution law of surface fractures caused by mining, China University of Mining and Technology, 1997, 26(2): 56-59); Li Xiao et al. used the self-developed IGG-1 mechanical fracture observation meter to monitor the geometric information of more than 10 ground fissures in Jinchuan No. According to the analysis, the fractures have obvious three-dimensional characteristics, and their causes were analyzed accordingly (Li Xiao, Lu Shibao, Liao Qiulin, Du Guodong. Distribution characteristics and field monitoring analysis of ground fissures caused by filling mining[J]. Chinese Journal of Mechanics and Engineering, 2006, 25(7): 1361～1369); Yao Juan established a mathematical model for crack width and deformation calculation based on the change of spatial information between any two points, pointing out that crack width and deformation are reflections of An important indicator of fracture change (Yao Juan, Xu Gong, Research on the law of surface fractures caused by mining [J]. Journal of Shandong University of Technology (Natural Science Edition), 2009, 23(6): 105-108); Li Liang, Wu Kan et al. used three-dimensional laser scanning method to obtain cloud data of surface characteristics in the subsidence fissure area, and input the distance and subsidence value of each point from the starting point into MATLAB in the form of (x, y), and interpolated these discrete points to form a smooth The to-be-analyzed curve L is analyzed by four kinds of wavelets, which are consistent with the actual observation data, and can be used to extract the distribution of fractures (Li Liang, Wu Kan, Chen Ranli, Zhang Shu. Wavelet analysis in the extraction of surface fracture information in mining subsidence Application of [J]. Surveying and Mapping Science, 2010, 35(1): 165～167).

However, most of the above studies focus on the overall fracture as the research object, emphasizing on the distribution of fractures. In some monitoring studies on fractures, the initial monitoring time of fractures is seriously lagging behind the time of crack appearance, and the obtained data cannot fully contain the initial state of fractures. The monitoring frequency is not standardized, and it is not suitable for modern mining in the Shendong mining area, resulting in rapid changes in the characteristics of cracks on the surface.

Generally speaking, the monitoring of the stages and processes experienced by fractures from their initial state to their complete or basic disappearance on the surface, especially for the life cycle monitoring of fractures at the front of the working face in the thin bedrock sandstorm area, has not been carried out. Corresponding research, the study of the cracks on the land ecological environment in this process is out of the question.

The difficulty of monitoring the life cycle of the front cracks in the working face in the sandstorm area lies in:

1) The identification and selection of observation objects is very difficult: the surface of the wind-blown sand area with thin bedrock is covered by loose layers, and the soil above the scour layer is mainly composed of yellow sand with high mobility. The influence of plasticity is greater, and the representation of the initial stage of surface cracks on the surface is relatively weak. Compared with other types of areas, it is very difficult to distinguish and select its characteristics. Therefore, the data of the initial state of the ground cracks when they are generated and the final life cycle of the cracks are obtained. had a great impact;

2) It is difficult to obtain the geometric information of fractures: the presence of floating sand layers on the surface in the sandstorm area, the soil on both sides of the cracks is too sandy and loose in texture, and part of the soil on the crack wall is prone to collapse during the cracking and closing process of the cracks. phenomenon, which brings great difficulties to the acquisition of crack width data. Uncertain accidental errors introduce gross errors, and the expected effect cannot be achieved, and ultimately the life cycle of the front crack cannot be obtained.

Contents of the invention

In view of this, the object of the present invention is to propose a method for monitoring dynamic fractures in well mining working faces, to accurately and completely obtain dynamic fractures and geometric information in the development process thereof, and to study soil fractures caused by regional surface fractures. The spatio-temporal evolution of physical and chemical properties provides a basis, and ultimately provides a scientific basis for ecological restoration programs and measures in this area.

In order to realize the above-mentioned purpose of the invention, the present invention adopts the following technical solutions:

A method for monitoring dynamic fractures in an underground mining face, the method comprising the following steps:

(1) Lay out the fissure monitoring datum line: before the coal mining work, lay out the fissure monitoring datum line, the datum line is made up of several surface mobile observation stations, and the said observation station is from the rear of the cut hole along the working face. For center line layout, the two ends of the reference line should be guaranteed to be beyond the scope of influence of mining, and the spatial coordinate positions of each observation station should be measured after the layout;

(2) Find the frontmost crack: when the working face advances to the first position A, mark and observe the new suspected cracks in front of it, and find out the cracks that develop with the subsequent advancement of the working face among these suspected cracks. Among these developed cracks, the crack with the largest distance from the first position is the front end crack, and the second position of the front end crack is measured as B, and the distance C between the second position and the first position is obtained;

(3) Establish a mathematical model: Repeat step 2 to obtain the first position Ai of multiple working faces, the second position Bi of the corresponding front end crack and the distance Ci between the first position and the second position, and establish the mathematics of the three Model, Bi=Ai+C', where C' is the mathematical expectation of multiple Ci, i=1, 2..n;

(4) According to the mathematical model established in step 3, at the position C' from the working face, select the most adjacent multiple cracks on both sides of the position as observation cracks, and measure the multiple widths of the multiple cracks as the working face advances change, the measurement frequency is greater than 1 day/time, until the fracture no longer develops and is completely closed on the surface, and the most obvious fracture is selected as the best observation fracture;

(5) At different working face positions, repeat step 4 to obtain the width change data of multiple best observed cracks;

(6) According to the multiple width change data of the best observed cracks as the working face advances obtained in steps 4 and 5, draw the trend diagram of the crack width with respect to the position of the working face.

Preferably, according to the relevant theory of mining subsidence, the layout of the baseline follows the following principles: under the condition that the surface can be fully mined, the baseline can pass through the flat bottom of the mobile basin; Under these conditions, the baseline should be set on the main section of the mobile basin.

Preferably, in step 1, the observation stations are arranged at intervals of 10-40 meters.

Preferably, while observing the width of the crack, changes in the length, depth and drop of the crack are also observed.

Preferably, when observing the width of the crack in step 4, the observation rods are arranged perpendicular to the crack on both sides of the crack at a distance of 5-10 cm from the crack, and the initial width Lo of the crack is measured, as well as the distance Do between the observation rods at both ends, and the distance Di between the observation rods is measured later. , calculate the crack width Li by the formula Li=Lo+(Di-Do), where i=1, 2..n.

Preferably, multiple width measurement points are arranged on each crack, and the distance between the width measurement points is 3-5 meters.

Preferably, the observation period of each fracture is T>2B/V, where B is the bandwidth of the continuous fracture zone in the strike direction of the working face, and V is the daily advancing speed of the working face. So far, the unit of T is day, the unit of B is meter, and the unit of V is meter/day.

计算出最大下沉速度滞后距L，其中，Ho代表采煤工作面的平均采深，

为最大下沉速度滞后角，在工作面与观测裂缝之间的距离D＜2L时，加大观测频率，当D＞2L时，减小观测频率。Preferably, in steps 4 and 5, according to the formula

Calculate the maximum sinking velocity lag distance L, where Ho represents the average mining depth of the coal mining face,

is the lag angle of the maximum sinking velocity. When the distance between the working face and the observed fracture is D<2L, the observation frequency is increased, and when D>2L, the observation frequency is decreased.

It can be seen from the above technical solution that the dynamic crack monitoring method provided by the present invention constructs the spatial reference system of the working face and cracks; by establishing a mathematical model between the frontmost crack of the working face and the position of the working face, a measurement method of crack characteristics is provided (observation method, observation period and frequency), providing a scientific basis for the accurate selection of the best observation fracture (observation object) at any working face position, and by measuring the fracture geometry information including the initial stage of ground fissure generation and development, The change trend diagram of the fracture width with respect to the position of the working face is drawn to analyze the characteristics and time node information of all typical stages experienced in the whole process from the creation to the complete closure of the front fracture, and provide complete and reliable data for the acquisition of the fracture life cycle ; and then provide a time benchmark and technical support for the study of the impact mechanism of coal mining on the land ecological environment and its self-repair cycle in this area.

Description of drawings

Fig. 1 is the layout schematic diagram of datum line and monitoring point among the present invention;

Fig. 2 is the observation schematic diagram of crack width in the present invention;

Fig. 3 is a graph showing the variation trend of the crack width as the working face advances in one embodiment of the present invention.

Detailed ways

Hereinafter, the present invention will be described in detail by taking the practical application of the method of the present invention in the life cycle monitoring of front end cracks in the thin bedrock sandstorm area as an example. However, those skilled in the art should realize that the present invention is not limited thereby.

The method of the present invention comprises the following steps:

Step 1: Lay out crack monitoring baselines.

The reference line is composed of several mobile observation stations on the surface. The observation stations are arranged from the rear of the cutout along the center line of the working face. Ahead of coal mining work. Preferably, the reference line is based on the relevant theory of mining subsidence, and the layout of the reference line follows the following principles: under the condition that the surface can be fully mined, the reference line can pass through the flat bottom of the mobile basin; Under the condition of full mining, the baseline shall be set on the main section of the mobile basin.

As shown in Figure 1, 1 is the position of the incision, 2 is the baseline, and 3 is the observation station arranged on the baseline. The observation stations are laid out at intervals of 10-40 meters, and the spatial coordinates of the observation stations are determined by methods such as theodolite wire and leveling survey after the arrangement.

Step 2: Find the frontmost crack.

The fracture at the front end of the working face is the best monitoring object for the whole process of fracture development, but in the windy and sandy area, the surface may be covered by loose layers, resulting in very weak indications on the surface at the initial stage of the fracture at the front end of the working face. In addition, the root growth of some psammophytes may also lead to cracks on the ground surface, so the identification of the front cracks brings a lot of interference information. Therefore, it is necessary to take measures to find out the most frontal cracks in combination with the mining position of the working face.

Specifically, when the working face advances to the first position A (the distance between the working face and the incision hole), the new suspected cracks in front of it are marked and observed, and the surrounding surface mobile observation stations are used as control points , set up a total station or other measuring equipment, observe the development of these suspected cracks within a suitable period of time (such as 4-10 days) according to the site conditions, and find out the development of these suspected cracks with the subsequent advancement of the working face. cracks (that is, cracks whose length or width can change), among these developed cracks, the crack with the largest distance from the first position A is the frontmost crack, and the second position B of the frontmost crack is measured, and the second position B and the first position A are obtained. A distance C between locations A.

The third step: establish a mathematical model. Repeat the method of the second step to obtain the first positions Ai of multiple working faces, as well as the second positions Bi of the corresponding front-end cracks and the distance Ci between the first positions Ai and the second positions Bi (i=1, 2 ..n), using the least square method to establish the mathematical model of the three, Bi=Ai+C', where C' is the mathematical expectation of multiple Ci, so as to provide the next step for the selection of the observation object and the geometric information of the initial state Get laid.

Step 4: According to the mathematical model established in the third step, at a position with a distance of C' from the current working face, select the most adjacent cracks (for example, 4 cracks) on both sides of the position as observation cracks, which can be used The total station and the adjacent surface mobile observation station calibrate the spatial position of its initial state, and simultaneously measure the multiple width changes of the multiple fractures as the working face advances. Until the surface is completely closed, the most obvious fracture is selected as the best observed fracture.

As shown in Figure 2, 4 is a body surface crack, 5 is an observation rod, and 6 is a steel ruler. The change in crack width can be measured by the following methods:

Arrange observation rods perpendicular to the crack at a distance of 5-10cm on both sides of the crack, measure the initial width Lo of the crack at this place (can be directly measured with a steel ruler), and the distance Do between the observation rods at both ends, and only need to measure the distance of the observation rod in the later stage For the distance Di (i=1, 2..n, the number of measurements), the crack width Li for each measurement is calculated by the formula Li=Lo+(Di-Do). In addition, because the cracks are long, multiple groups of observation rods can be installed on each crack, with an interval of 3-5 meters. In actual operation, observation rods can also be added in time according to the development of cracks. In addition, the observation rod should be as vertical as possible to the ground, embedded in the soil, and the buried depth should not be less than 20cm.

Among them, in order to minimize the workload in the field, empirical formulas can be further used to determine the observation period and frequency.

As the working face advances, continuous observation of fractures is carried out. According to the width B of the continuous fracture zone in the strike direction in the basin, and the daily advancing speed V of the working face, preferably, the observation period T>2B/V for each fracture, the observation work Until the surface representation of ground fissures disappears and remains unchanged, the unit of T is day, the unit of B is meter, and the unit of V is meter/day.

计算出最大下沉速度滞后距L，其中，Ho代表采煤工作面的平均采深。根据先前布设的裂缝观测基准线上地表移动观测站在采动过程中高程的变化数据，即可计算出最大下沉速度以及

进而得到L的大小。在工作面与观测对象二者之间的距离D＜2L时，观测频率相对较大，尤其是在0.5L＜D＜1.5L时，应进行加密观测，当D＞2L时，观测频率应相应减小。The change of fracture width is related to the intensity of surface activity, which can be reflected by the subsidence velocity of the surface and the distance L from the working face when the surface reaches the maximum subsidence velocity (usually expressed as the lag distance of the maximum subsidence velocity). Therefore, preferably, it should be compared with Adjust the observation frequency according to the closeness of the distance d and L between the position of the observed crack and the position of the working face. When the crack width changes greatly, the observation frequency needs to be increased; when the crack width changes small, the observation frequency should be reduced. . Normally, the maximum sinking velocity lag angle can be used According to the formula

Calculate the maximum sinking velocity lag distance L, where Ho represents the average mining depth of the coal face. The maximum subsidence velocity and

Then get the size of L. When the distance between the working face and the observation object is D<2L, the observation frequency is relatively high, especially when 0.5L<D<1.5L, intensive observation should be carried out; when D>2L, the observation frequency should be corresponding decrease.

In order to better obtain the change of the crack, preferably, while measuring the change of the crack width, the length of the crack and the change of the drop can also be measured simultaneously. For example, through the nearest observation station, use the total station to determine the coordinates of the two ends of the fracture by wire measurement, and draw the up-and-down comparison map of the working face, and use the two-point coordinates to calculate the fracture length.

Step 5: In order to more comprehensively observe the growth and development of fractures with the advancement of the working face, repeat the method of the fourth step, so as to obtain the development of multiple best observed fractures at different positions of the working face.

Step 6: Use the obtained fracture width information to draw a trend chart of the width information of a single fracture, analyze the duration of each main typical stage and the advance amount of the working face, and summarize the surface fractures in this area through the statistical information of multiple fractures. complete life cycle.

代表4#和

代表5#。Embodiment: For the monitoring of mining cracks in a certain mining area, the crack width information obtained by the above method is used to draw a trend diagram of the crack width advancing with the working face. As shown in Figure 3, there are 5 observation points on the crack, of which Represents 1#, ● represents 2#, ▲ represents 3#,

Represents 4# and

Represents 5#.

When the front working face is 454m away from the cutting hole, the crack appears first, 7m ahead of the working face; when the working face advances 19m, the crack shows the largest sign, and the 5# information collection point increases from 3.3mm to about 25mm, The change speed is about 1.158mm/m. This area corresponds to the A1 stage. In this stage, the fracture widths of the four information collection points #1, #2, #3, and #4 are all increasing, which belongs to the fracture development stage.

When the working face continued to move forward for 42m, the width of the five information collection points decreased as a whole, and the width value of the information collection point tended to 0 at 515m. Judging from the ground representation, the cracks were also in a healing state as a whole. When the working face continues to advance to 565m, there is basically no fracture development, and the corresponding area is the A2 stage on the map; in the first half cycle of fracture development, from appearance-development-closure and stability, the working face has advanced about 111m, at this time the position of the leading crack in the working face is 104m.

When the working face continued to advance to 577m, the fractures re-opened at the previous positions, and the widths of the fractures at the five information collection points were all smaller than the maximum value in the first stage. The A3 area corresponding to this stage belongs to the surface In the loosening stage, the working face is 116m ahead of the crack at this time.

From 577m to 613m, the change of the fracture width is very weak. This stage corresponds to the A4 area, which is defined as the gradually stable stage. At this time, the working face is ahead of the fracture by 152m; in the later stage, the fracture gradually tends to close, and this stage corresponds to the A5 area. , which is defined as the complete healing stage. Follow-up observation results show that the cracks do not continue to crack. At this time, the working face is ahead of the cracks by 219m. At each stage, the positions of the cracks and the working face are: A1 (-7m ~ 12m); A2 ( 12m ~ 104m); A3 (104m ~ 116m); A4 (116m ~ 152m); A5 (152m ~ 219m), where "-" means that the working face lags behind the position where the crack appears.

The whole process from emergence to complete closure, this periodic change is called the life cycle of cracks.

Other observation objects also have similar rules, so the life cycle of dynamic fractures above the working face in the wind-sand area can be divided into five stages: A1 developmental stage (initial appearance, from small to large); A2 healing stage (from large to small, initial healing); A3 surface loosening stage (cracks re-open, but to a lesser extent than the development stage); A4 gradual stabilization stage (cracks hardly change, in a stable stage); A5 complete closure stage (cracks heal again, no longer open).

Claims (8)

1. the monitoring method of a pit mining workplace dynamic crack, is characterized in that, said method comprising the steps of:

(1) lay the Crack Monitoring datum line: before coal work, lay the Crack Monitoring datum line, described datum line is comprised of several observation station of ground movement, described research station is laid along the center line of workplace trend from the rear of open-off cut, the two ends of datum line should guarantee to exceed Affected areas by mining, and measure afterwards the volume coordinate position of each research station in laying;

(2) find out crack foremost: when the advance of the face is A to primary importance, mark observation is carried out in emerging doubtful crack, its place ahead, find out the crack of growing with the follow-up propelling of workplace in these doubtful cracks, be crack foremost with primary importance apart from the crack of maximum in the crack of these growths, measure foremost that the second place in crack is B, obtain the distance C between the second place and primary importance;

(3) set up mathematical model: repeating step 2 obtains a plurality of primary importance Ai of the advance of the face, and the distance C i of the second place Bi in its corresponding crack foremost and primary importance and the second place, set up three's mathematical model, Bi=Ai+C ', wherein C ' is the mathematical expectation of a plurality of Ci, i=1,2..n;

(4) mathematical model of setting up according to step 3, with the work at present identity distance from the position that is C ', select the most adjacent many cracks in these both sides, position as the observation crack, two 5-10cm places, lateral extent crack, crack lay the observation rod perpendicular to the crack in observation, measure this many cracks with a plurality of wide variety of the advance of the face, measure frequency greater than 1 day/time, until no longer grow in the crack, till complete closure on the earth's surface, therefrom select the most obvious crack of growth and observe the crack as the best;

(5) in different workplace positions, repeating step 4 obtains a plurality of best wide variety data of observing the crack;

(6) the best that obtains according to step 4 and 5 observes the crack with a plurality of wide variety data of the advance of the face, draws fracture width about the changing trend diagram of workplace position, sums up the complete life cycle of this zone surface cracks.

2. the method for claim 1, is characterized in that, learns correlation theory according to mining subsidence, and following principle is followed in the laying of described datum line: can reach on the earth's surface under the condition of fully adopting, datum line gets final product by the flat of bottom of moving basin; Can not reach on the earth's surface under the condition of fully adopting, datum line need be located on the principal section of moving basin.

3. the method for claim 1, is characterized in that, interval, described research station 10-40 rice is laid.

4. the method for claim 1, is characterized in that, in the observation fracture width, further observes the length in crack and the variation of drop.

5. the method for claim 1, is characterized in that, when measuring fracture width in step 4, measure crack original width Lo, and the distance B o of two ends observation rod, the later stage is measured the distance B i of observation rod, by formula Li=Lo+ (Di-Do) calculating fracture width Li, i=1 wherein, 2..n.

6. method as claimed in claim 5, is characterized in that, lays a plurality of width measure points on every crack, and the spacing between width measure is selected is 3-5 rice.

7. method as described in claim 1 or 5, it is characterized in that, the observation cycle T of every crack〉2B/V, wherein B is the bandwidth that workplace moves towards the continuous slit band of direction, V is workplace day fltting speed, observation work until the ground of ground fissure characterize disappear and continue unchanged till, wherein the unit of T be the sky, the unit of B is rice, and the unit of V is rice/sky.

8. the method for claim 1, is characterized in that, in step 4 and 5, according to formula

Calculate maximum rate of sinking and lag behind apart from L, wherein, Ho represents that on average adopting of coal-face is dark,

Be maximum rate of sinking drag angle, during the distance B in workplace and observation between the crack＜2L, strengthen observing frequency, as D during 2L, reduce observing frequency.

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