CN111859517A - Dam body deformation damage analysis method for deep coal seam mining under reservoir dam - Google Patents
Dam body deformation damage analysis method for deep coal seam mining under reservoir dam Download PDFInfo
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Abstract
The invention provides a dam body deformation damage analysis method for deep coal seam mining under a reservoir dam. Firstly, building a dam body moving deformation numerical model according to an actual excavation basin, simulating a dam body, building an integral simplified simulation model, then simulating a subsidence curve of the ground surface moving deformation according to a full-size numerical value, determining a subsidence basin of the ground surface moving deformation in the actual working face propelling process, carrying out simulated excavation on the integral simulation model, and observing the moving deformation damage condition of the dam body during excavation according to the built simulation model; by simplifying structural inversion, the invention solves the problems that the ratio of the height of the dam body to the coal seam burial depth is large, and the deformation and damage of the dam body are difficult to observe by conventional similar material simulation and numerical simulation, and has important guiding significance for the formulation of the safety protection and maintenance scheme of the reservoir dam.
Description
Technical Field
The invention relates to the technical field of mining, in particular to a dam body deformation damage analysis method for mining deep coal seams under reservoir dams.
Background
The problem of safe operation of the reservoir dam in the process of mining the deep coal seam under the reservoir dam always restricts the major problem of safe mining of deep coal resources under the reservoir dam in China. In order to realize the maximum reasonable development and utilization of coal resources under reservoir dams, the deformation failure mechanism of a dam body in the coal seam mining process must be mastered. However, the coal seam burial depth is large, the earth surface reservoir dam soil body structure is small, the ratio of the coal seam burial depth to the dam body height is large, and the conventional method is difficult to calculate the deformation damage size, form, damage degree and the like of the dam body, so that the problem of safety and stability of the dam body mined from the deep coal seam under the reservoir dam is always a hotspot and difficulty for research of engineering technicians and scientific researchers in the coal industry.
At present, a full-size model from a coal seam floor to a dam body is established according to the existing software and hardware conditions, and the solving time and the grid number are approximately N by using the existing computer4/3The proportional relationship of (a), the length of time required to complete the entire simulation is quite surprising; by utilizing the existing similar material simulation device, the cross section of the dam body is too small compared with a full-size model, so that the deformation and the damage of the dam body are difficult to observe in detail and cannot be accurately observed at all; and the moving deformation of the dam body is deduced according to the mine pressure display rule of the coal seam roof, and the accuracy of the calculation result is difficult to ensure due to the fact that the coal seam is too deep and the roof rock stratum structure is complex. Therefore, a research method capable of rapidly and accurately observing and deducing dam deformation damage needs to be explored, and theoretical guidance basis is provided for dam deformation damage mechanism analysis and dam safety evaluation under the reservoir dam.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a dam body deformation damage analysis method for deep coal seam mining under a reservoir dam, which comprises the following steps:
step 1: calculating a subsidence basin formed on the earth surface of the dam body after coal seam mining, and calculating the volume V of the subsidence basin by adopting earth surface movement deformation prediction software based on a probability integration method according to the earth surface after coal seam mining1Calculating by adopting full-size numerical simulation software to obtain the volume V of the sinking basin2，
Step 2: according to V1、V2Comparing the maximum sinking values of the two sinking basins, and selecting the sinking basin with the larger maximum sinking value as an actual excavation basin;
and step 3: constructing a dam body moving deformation numerical model after mining of the fully mechanized caving face under the dam;
and 4, step 4: scaling the actual dam size into the dam size during simulation according to the similarity ratio of the surface structure to the actual surface structure in the dam movement deformation numerical model to obtain a simulated dam;
and 5: according to the position of an actual dam body in the ground surface, arranging the simulation dam body on the upper surface of the rock-soil layer to obtain an integral simulation model;
step 6: simulating a subsidence curve of the ground surface moving deformation according to the full-size numerical value, determining a subsidence basin of the ground surface moving deformation in the actual working face propelling process, and performing simulated excavation on the whole simulation model; when the earth surface movement deformation of the excavation area does not reach the dam body and the dam body does not sink, the simulation excavation step distance is set to be SsDetermining the simulated excavation volume L according to the subsidence basin of the full-size numerical simulation ground surface movement deformations(ii) a When the earth surface movement deformation of the excavation area reaches the dam body or the dam body sinks, the simulated excavation step distance is set to be Sm＝λSsThe simulated excavation amount is set to λ Ls,0＜λ＜1；
And 7: and (3) observing the moving deformation damage condition of the dam body during excavation by simulating excavation of the whole simulation model.
The step 3 comprises the following steps:
step 3.1: calculating by using formulas (1) to (3) according to the similarity ratio of the surface structure to the actual surface structure in the model to obtain the length, width and height of the simulated excavation basin to be constructed in the model;
am＝as(1)
bm＝bs(2)
hm＝hs(3)
wherein, amShowing the length of the simulated excavation basin, asLength of actual excavated basin, bmWidth of simulated excavation basin, bsWidth h representing actual excavated basinmHeight, h, of simulated excavated basinsRepresenting the height of the actual excavated basin;
step 3.2: according to the ground surface movement change of the working surface under different propelling distancesThe shape range is reserved with the length s on two sides of the simulated excavation basin along the length direction of the dam body1The boundary limiting condition of (1);
step 3.3: thickness s of overlying rock-soil layer on excavated basin2Thickness s of rock-soil layer covered and reserved on excavated basin2Greater than or equal to the height of the caving zone;
step 3.4: in order to ensure the slow continuity of the moving deformation of the rock-soil layer, a layer with the thickness of s is laid below the rock-soil layer3The transition material of (2), the transition material being required to have sufficient toughness and flexibility;
step 3.5: determining the length A, the width B and the height H of a dam body movement deformation numerical model to be constructed, wherein the length A is as follows:
A＝am+2s1(4)
width B is:
B＝bm(5)
the height H is:
H＝hm+s2+s3(6)。
the invention has the beneficial effects that:
the invention provides a dam body deformation damage analysis method for mining a deep coal seam under a reservoir dam, which can greatly reduce the size of a model, reduce the operation time and improve the analysis precision of small targets by simplifying structural inversion and mastering the deformation damage mechanism of a reservoir dam soil body structure according to the time-space sequence evolution rule of an overlying rock stratum of a goaf after the mining of the deep coal seam, solve the problems that the ratio of the height of the dam body to the buried depth of the coal seam is large, the conventional similar material simulation and numerical simulation are difficult to realize the observation of the dam body deformation damage, realize a rapid and accurate research method for observing the dam body deformation damage, and have important guiding significance for establishing a risk evaluation index system of the dam body after the mining of the deep coal seam under the reservoir dam and formulating a safety protection and maintenance scheme of the reservoir dam.
Drawings
Fig. 1 is a schematic diagram illustrating the movement and deformation of the overburden rock and the earth's surface under the dam and the process decomposition thereof, wherein (a) is a schematic diagram illustrating the movement and deformation of the overburden rock and the earth's surface under the dam, and (b) is a schematic diagram illustrating the movement and deformation of the overburden rock and the earth's surface under the dam;
FIG. 2 is a schematic diagram of an overall simulation model constructed in accordance with the present invention;
FIG. 3 is a schematic view of the excavation sequence of the integrated simulation model of the present invention;
FIG. 4 is a layout diagram of the excavated body in the simulation experiment of the present invention;
FIG. 5 is a diagram of a model structure constructed in a simulation experiment according to the present invention;
FIG. 6 is a schematic diagram of model excavation to be experimentally constructed in the present invention;
FIG. 7 is a graph showing a comparison of the moving deformation of a dam body when the present invention is simulated to excavate the dam body at different positions, wherein (a) shows a comparison of the moving deformation of the dam body when the dam foot 24m on the back side of the dam body is pushed, (b) shows a comparison of the moving deformation of the dam body when the dam foot 28m on the back side of the dam body is pushed, (c) shows a comparison of the moving deformation of the dam body when the dam foot 38m on the back side of the dam body is pushed, (d) shows a comparison of the moving deformation of the dam body when the dam foot 52m on the back side of the dam body is pushed, (e) shows a comparison of the moving deformation of the dam body when the dam foot 58m on the back side of the dam body is pushed, (f) shows a comparison of the moving deformation of the dam body when the dam foot 64m on the back side of the dam body is pushed, (g) shows a comparison of the moving deformation of the dam body when the dam foot 84m on the back side of the dam body is pushed, and (h) shows a comparison of the moving deformation of the dam body when the dam foot 104, FIG. (i) is a graph showing a comparison of the deformation of the dam when pushed over the dam butt 124m on the back side of the dam, and FIG. (j) is a graph showing a comparison of the deformation of the dam when pushed over the dam butt 144m on the back side of the dam;
FIG. 8 is a simulation model constructed in modeling software in accordance with the present invention;
FIG. 9 is a diagram of the positional relationship between the dam and the working surface constructed in modeling software according to the present invention;
FIG. 10 is a sinking curve diagram of a measuring point at the center line position of the dam body under different propulsion lengths in the invention;
FIG. 11 is a graph of the final sag value of the dam according to the present invention;
fig. 12 is a stress trend graph of the dam body under different push lengths in the invention, wherein (a) shows a stress graph before the working face is pushed to 600m, wherein (b) shows a stress graph when the working face is pushed to 800m, wherein (c) shows a stress graph when the working face is pushed to 900m, wherein (d) shows a stress graph when the working face is pushed to 920m, wherein (e) shows a stress graph when the working face is pushed to 930m, and wherein (f) shows a stress graph when the working face is pushed to 2000 m;
FIG. 13 is a dam body movement deformation measuring point layout diagram in actual under-dam mining according to the present invention;
FIG. 14 is a graph of the present invention showing the measured point sag versus time for numerical simulation based on the actual measured point sag during dam mining and the measured point sag versus time for the method of the present invention;
FIG. 15 is a graph showing the variation of subsidence at different advance lengths of No. 1, No. 2 and No. 3 measurement points during actual under-dam mining according to the present invention;
FIG. 16 is a comparative graph of a sinking curve of a dam body at the No. 1 measuring point under different propulsion lengths during actual under-dam mining and numerical simulation of the method of the present invention;
in the figure, 1, a dam body, 2, reservoir water, 3, a ground surface, 4, a coal bed, 5, a bottom rock stratum, 6, a overburden, 7 and a rock-soil layer.
Detailed Description
The invention is further described with reference to the following figures and specific examples.
After the coal seam under the dam is mined, the movement deformation of overlying strata in the goaf is firstly propagated to the ground surface and the dam foundation around the dam body from bottom to top, and then the dam body is driven to move and deform together. In the process, the order and the magnitude of the moving deformation of each part of the dam are different according to the position relation of the dam and the sinking basin.
Decomposing the transmission process of deformation and damage of the overburden rock into two parts, wherein firstly, the movement deformation of the overburden rock and the earth surface caused by the mining of the working face is obtained, and sinking basins with different sizes are formed along with the advancing of the working face; and secondly, the dam body driven by the gradually expanded sinking basin moves and deforms to obtain the moving deformation of different parts of the dam body continuously expanded along with the sinking basin.
If the process of face mining and sinking basin formation can be omitted, the basin is directly excavated according to the process of sinking basin formation, so that the moving deformation and damage of the dam body are observed and analyzed, the model size is greatly reduced, the operation time is reduced, and the analysis precision of a small target is improved, as shown in a diagram (a) in fig. 1, a schematic diagram of mining overburden rock and ground surface moving deformation under the dam is shown, and a schematic diagram of separating the coal bed overburden bedrock in the diagram (a) from the water body and the dam body is shown in a diagram (b) in fig. 1.
The key to achieving this assumption is: firstly, a numerical model capable of accurately reproducing earth surface and dam body movement deformation is constructed; and secondly, decomposing the process of forming the sinking basin to form the basin digging amount corresponding to the advancing step length of the working face.
The sinking basin corresponding to the advancing step length of the working surface can be obtained by surface movement deformation prediction and full-scale numerical simulation of a probability integration method, and the deformation damage of the dam body is calculated by performing space-time sequence inversion according to the movement deformation of each point on the surface.
As can be seen in fig. 1 (b): if the dam is directly excavated on the earth surface, namely the bottom interface of the dam body, the deformation and the damage of the dam body can be correspondingly moved and deformed or even damaged immediately along with the excavation mode and the excavation amount. The deformation is inconsistent with slow and continuous deformation caused by deep working face mining, and cannot reflect the difference of the actual deformation and damage processes of the dam body, so that the deformation and damage of the dam body are seriously deviated from the real moving deformation process, and the result is not advisable. In order to solve the problem, the simulation can reproduce dam body deformation and damage caused by coal seam mining, a buffer rock-soil layer with certain thickness is reserved below the earth surface, and a series of problems caused by direct excavation of the earth surface are avoided.
Therefore, the invention provides a dam body deformation damage analysis method for deep coal seam mining under a reservoir dam, which comprises the following steps:
step 1: calculating a subsidence basin formed on the earth surface of the dam body after coal seam mining, and calculating the volume V of the subsidence basin by adopting earth surface movement deformation prediction software based on a probability integration method according to the earth surface after coal seam mining1Calculating by adopting full-size numerical simulation software to obtain the volume V of the sinking basin2，
Step 2: root of herbaceous plantAccording to V1、V2Comparing the maximum sinking values of the two sinking basins, and selecting the sinking basin with the larger maximum sinking value as an actual excavation basin;
and step 3: the dam body moving deformation numerical model after the mining of the fully mechanized caving face under the dam is constructed, as shown in fig. 2, includes:
step 3.1: calculating by using formulas (1) to (3) according to the similarity ratio of the surface structure to the actual surface structure in the model to obtain the length, width and height of the simulated excavation basin to be constructed in the model;
am＝as(1)
bm＝bs(2)
hm＝hs(3)
wherein, amShowing the length of the simulated excavation basin, asLength of actual excavated basin, bmWidth of simulated excavation basin, bsWidth h representing actual excavated basinmHeight, h, of simulated excavated basinsRepresenting the height of the actual excavated basin;
step 3.2: according to the ground surface moving deformation range of the working surface under different propelling distances, the reserved lengths on the two sides of the simulated excavation basin are s along the length direction of the dam body1The boundary limiting condition of (1);
the determination of the thickness of the rock-soil layer needs to be kept, and two problems need to be considered, namely if the thickness is too large, excavation cannot be carried out according to a basin formed by the earth surface, and the total excavation amount and the shape of the depth are difficult to determine; if the thickness is too small, the shallow coal seam characteristic will appear in the degeneration destruction of the earth surface and the dam body, and the condition of slow continuous deformation cannot be reproduced.
According to the 'three-zone' structure of the overlying strata degeneration damage of the goaf, the thickness of the reserved rock-soil layer is at least larger than the height of the caving zone, and the earth surface can not be cut and caved.
Step 3.3: thickness s of overlying rock-soil layer on excavated basin2Thickness s of rock-soil layer covered and reserved on excavated basin2Greater than or equal to the height of the caving zone;
in order to excavate according to the shape of the surface subsidence basin, a rock-soil layer with small thickness is reserved, a layer of material with enough toughness and flexibility is arranged below the rock-soil layer, the moving deformation of the rock-soil layer is ensured to be slow and continuous, and the purpose of simulating the actual deformation damage process of the dam body is realized.
Step 3.4: in order to ensure the slow continuity of the moving deformation of the rock-soil layer, a layer with the thickness of s is laid below the rock-soil layer3The transition material of (2), the transition material being required to have sufficient toughness and flexibility;
step 3.5: determining the length A, the width B and the height H of a dam body movement deformation numerical model to be constructed, wherein the length A is as follows:
A＝am+2s1(4)
width B is:
B＝bm(5)
the height H is:
H＝hm+s2+s3(6)
and 4, step 4: scaling the actual dam size into the dam size during simulation according to the similarity ratio of the surface structure to the actual surface structure in the dam movement deformation numerical model to obtain a simulated dam;
and 5: according to the position of an actual dam body in the ground surface, arranging the simulation dam body on the upper surface of the rock-soil layer to obtain an integral simulation model;
the basin for excavation can be a sinking basin obtained by full-size numerical simulation or a sinking basin obtained by prediction of ground surface movement deformation, the excavation step pitch can be divided into two parts, one part is that a larger step pitch is set before the dam body sinks, a smaller step pitch is set at a certain distance before the dam body sinks, and each excavation is carried out according to a curved surface body formed by the thick edge at the middle upper part between two adjacent excavation curved surfaces.
Step 6: simulating the subsidence curve of the ground surface moving deformation according to the full-size numerical value, determining the subsidence basin of the ground surface moving deformation in the actual working face propelling process, and aligningCarrying out simulated excavation on the simulation model of the body; when the earth surface movement deformation of the excavation area does not reach the dam body and the dam body does not sink, the simulation excavation step distance is set to be SsDetermining the simulated excavation volume L according to the subsidence basin of the full-size numerical simulation ground surface movement deformations(ii) a When the earth surface movement deformation of the excavation area reaches the dam body or the dam body sinks, the simulated excavation step distance is set to be Sm＝λSsThe simulated excavation amount is set to λ L s0 < λ < 1, wherein the excavation sequence is schematically shown in FIG. 3, where 1,2, …, n denotes the excavation sequence.
And 7: through simulation excavation of an integral simulation model, the moving deformation damage condition of the dam body during excavation is observed, the work such as the internal deformation damage characteristic and the excavation size of the dam body is recorded until the dam body is stable in moving deformation, and the deformation damage rule and the characteristic of the internal part of the dam body along with the advancing of a working face and the subsidence change of the earth surface are summarized and analyzed according to the deformation damage state of the internal part of the dam body at each stage, so that the dam body is used for guiding the mining work of the deep coal seam under the reservoir dam in actual production.
In order to verify that the dam body movement deformation damage condition obtained by the analysis method is consistent with the dam body movement deformation damage condition generated in actual excavation, verification is performed through simulation experiments and numerical simulation respectively.
The simulation experiment verification process comprises the following steps:
and (3) converting various physical and mechanical indexes of the coal rock into similar indexes of the model according to geological mining conditions of a first mining face, and establishing a similar material simulation experiment model. According to the connotation of the dam deformation and damage simplification analysis method adopted under the dam, simulation analysis is carried out on the dam deformation and damage, the dam deformation and damage state is observed, the real deformation and damage rule and characteristics of the dam are analyzed by using the obtained result, and a basis is provided for the dam maintenance scheme design.
The experiment platform adopts the length-width ratio of 10:1, adopts the experiment platform of Qingdao Qiankun XingO trades GmbH, and a set of similar material experiment platform is designed and manufactured according to the proportion of 10: 1. According to the size of a dam body, the depth and the range of a ground surface subsidence basin and the requirement of model construction in the method provided by the invention, the size of a self-made experiment platform is determined to be 200cm in length, 20cm in width and 60cm in height, the whole frame of the experiment platform is formed by welding steel structures, a Freund board is adhered to the inner side filling plane to maintain the smoothness of the platform, toughened glass with the thickness of 10mm is installed on the observation front side of the experiment platform, and grid dimension lines of 0.5cm, 0.5cm and 0.5cm are adhered on the glass, so that paste filling and observation of each deformation value in the experiment process are facilitated.
And according to the specific conditions of the simulation object, the size of the surface subsidence basin and the model building method, building a similar material simulation model along the direction vertical to the trend of the dam body. Determining the length ratio of the model simulated by the actual geological model and the similar material as alpha according to the similarity criteria of the geometric similarity ratio of the appearance shape, the motion similarity ratio of the moving deformation process and the dynamic similarity ratio of the field actual environmentLIntensity ratio α of 200σ270, time ratio αt14.1. In order to ensure the quality of the model effect, a rock-soil layer (20 m of surface soil layer and 10m of lower sandstone section) with the thickness of 30m is reserved on the upper surface of the excavated body. The model packing consists of a rock-soil layer and an excavated body, wherein the packing size of the rock-soil layer is 200cm in length, 20cm in width and 22.145cm in height; the filling size of the excavated body is 20cm in length, 2cm in width and 3.645cm in height. The widths of the dam crest and the dam foundation are respectively 2.5cm and 18.04cm, and the angles of the slopes of the dam bodies of the upstream slope and the downstream slope are respectively 22 degrees and 27 degrees.
As shown in fig. 4, the excavated body simulated in the experiment is replaced by rectangular wood strips, the dimensions of the wood strips are determined according to the similarity ratio, and the wood strips are respectively 20cm long, 2cm wide, 0.405cm high (right-side wood strip in fig. 4) and 20cm long, 1cm wide, and 0.405cm high (left-side wood strip in fig. 4).
In the experimental model, the density and tensile strength of rock-soil layers are used as main comparison indexes in conversion of various rock-soil body indexes, and the elastic modulus and Poisson's ratio are used as secondary indexes. And comparing physical and mechanical indexes of the dam body and the rock-soil mass under the dam according to the strength similarity, and searching out the conversion indexes of the soil-rock mass and a material proportion table corresponding to each index from 'comprehensive laboratory book for mining at mining institute of Liaoning engineering university' according to the calculation result, wherein the conversion indexes and the material proportion table are shown in a table 2, and the material proportion numbers are shown in a table 3.
TABLE 2 conversion index and ratio number of rock-soil layer
TABLE 3 similar materials proportioning Table
In order to improve the experiment precision and ensure that the experiment effect is better, the model is filled in a layered mode, and the excavation body is placed layer by adopting battens, so that the flatness and the tightness are ensured. And covering each layer of the excavated body with the thickness of 0.5cm, and performing layer-by-layer independent proportioning filling and compaction according to the proportioning number of each rock-soil layer. After the model is made, the time is required to wait for about 2 days, and excavation is carried out when the model is dried and the simulation strength reaches the expected strength. The filled model is shown in fig. 5.
According to the ground surface movement deformation range and the self length of the model under different advancing distances of the working surface, 20m is reserved at two ends of the designed model as boundary limiting conditions, the model is excavated for 35 times in total, the maximum single excavation length is 10cm, the minimum excavation length is 2cm, the single excavation is based on the stable state of the subsidence of the ground surface, the excavation mode is excavated according to the advancing direction of the working surface (excavation is carried out from left to right), the simulation excavation schematic diagram is shown in figure 6, the backwater slope of the dam body is 116.53cm away from the boundary of the model, the other side of the dam body is 65.44cm away from the boundary of the model, the total width of the excavation body is 3.645cm, wherein the step distance of the first simulation excavation is 11.77cm, the step distance of the second simulation excavation is 3.13cm, the step distance of the third simulation excavation is 4.87cm, the step distance of the fourth simulation excavation is 6.76cm, the step distance of the fifth simulation excavation is 10cm, and then the simulation excavation is continued, when the simulated excavation is performed to the position under the dam, the excavation is reduced to 2cm, and when the simulated excavation is performed to the other side of the dam body, the step distances of the simulated excavation are set to be 10 cm.
And (4) excavating the battens at the lower part of the simulated rock stratum according to the excavation steps and the excavation range, and observing the moving deformation characteristics of the dam body. According to the positions of all characteristic points influencing the moving deformation of the dam body in the simulation process of the similar materials, 10 sections which are pushed through the dam feet at the back water side of the dam body and are 24m, 28m, 38m, 52m, 58m, 64m, 84m, 104m, 124m and 144m are selected to analyze the deformation damage law and the characteristics of the dam body, and a moving deformation comparison graph of 10 times of excavation is shown in FIG. 7.
The above mining effect process simulated by fig. 7 can be seen: the dam body undergoes a change process from tensile deformation damage to compression-reduction, only time nodes of tensile-compression transition processes of all parts are different, and the dam foot on the side of the backwater slope at the beginning stage affected by mining firstly undergoes tensile deformation damage, then is the dam body on the side of the oncoming water slope, and finally is the middle position of the dam body. The process of changing from tension to compression also starts from the dam body at the side of the backwater slope, then the dam body at the side of the upstream slope and finally the middle position of the dam body.
The final subsidence value of the dam body is 7m, the height of the excavated body of the excavated part is 7.29m, and due to the fact that a rock-soil layer with the height of 30m is covered on the dam body, the final subsidence value of the dam body can be 6.99m according to the minimum residual crushing expansion coefficient of the damaged rock-soil layer, the difference of the final subsidence value and the actual observed subsidence quantity of the dam body is only 0.01m, the error is small, and the fact that the simplified simulation of similar materials is feasible and reasonable for the subsidence simulation of the dam body is verified.
The deformation damage process of the dam body is subject to each position of the ground surface subsidence curve after mining of the working surface, the ground surface movement deformation characteristic is met, and the fact that the simplified model analysis method has certain scientificity and rationality is also proved.
The second numerical simulation verification process is as follows:
the method still adopts FLAC3D numerical simulation software for simulating the deformation and damage of the dam under the dam, and the design of a simulation scheme is divided into 4 parts of model establishment, model setting, excavation scheme and measuring point arrangement.
And predicting the subsidence value of any point of the ground surface after the working surface under the mining dam is mined by using a probability integration method, importing the three-dimensional space coordinate corresponding to the subsidence value of any point into Midas modeling software, and drawing the subsidence basin of the ground surface moving deformation of the working surface under the mining dam by using the point-surface coupling calculation of the software. The established model is shown in fig. 8.
Gradient stress is applied in the horizontal direction, and the vertical stress of 0.0341MPa is applied to the deep water body of 3.41m on the upstream slope side of the dam body as the water body load.
114 observation points are arranged on the center line of the dam body in the direction of the dam, the distance between the measurement points is 5m, and the length of the measurement line is 570 m. Arranging dam body observation cross sections at each measuring point for analyzing displacement, deformation, stress and failure rules and characteristics of each section of the dam body, wherein the position relation between the dam body and the working surface is shown in figure 9, the working surface of S2S9 in the figure represents a fully-mechanized working surface, the width of the built model is 600m, the width of the working surface of S2S9 is 277m, and the width from two gate channels of the working surface to the boundary of the model is 160.7 cm;
according to simulation calculation results of different advancing lengths of the working face, monitoring data of the midpoint of the dam body measuring line along with the working face mining are extracted, a sinking curve of the dam body under the dam along with mining changes is drawn, surface sinking curves of the working face under different advancing lengths are summarized, and rules and characteristics of dam body movement deformation caused by mining are analyzed. FIG. 10 is a sinking curve diagram of the measuring point of the middle line position of the dam body when the working surface has different propelling lengths. As can be seen in fig. 10: when the working face is pushed to 470m (630 m from the middle point of the dam body measuring line), the dam body starts to be influenced by mining, and the maximum sinking value of the center position of the dam body is 0.092 m; when the distance is pushed to 1800m (pushing the middle point of the dam body measuring line to 700m), the center position of the dam body measuring line reaches the maximum sinking value of 7.17m under the condition. Therefore, the starting point of the sinking of the midpoint of the survey line is located 470m away from the open-cut eye, the ending point is located 1800m away from the open-cut eye, and the distance affected by mining is 1170 m. The sinking deformation rate of the dam body is the maximum (inflection point-slope magnitude dividing point) when the working face is pushed to 1100 m. And (3) drawing a dam body sinking curve by using the sinking value of the middle point of the measuring line when the working face mining is finished, namely when the sinking is stable, wherein the measuring point interval in the drawing is 20m and the measuring points are numbered from left to right in sequence as shown in FIG. 11.
As can be seen in fig. 11: when the working face is pushed, the maximum sinking position of the dam body is located at the center of the dam body, a flat basin is basically formed, and the maximum sinking value is 7.17 m. Wherein the sinking rate of the dam body within the range of 140 m-180 m and 380 m-420 m (100 m-140 m on both sides of the center of the working face) is greatly changed (characteristic point-inflection point), and the slope of the sinking curve of the dam body within the range of 180 m-260 m and 300 m-380 m (20 m-100 m on both sides of the center of the working face) is the largest. The maximum sinking value of two ends of the dam body is 0.14m, the influence of mining is minimum, and the influence range of the mining of the available working face on one side of the dam body is about 280 m.
According to the displacement change analysis result, the dam body is influenced by mining, the dam body starts from a position 630m away from the center of the dam body (the maximum sinking value of the center of the dam body is 0.092m), in order to explain the deformation damage process of the dam body in detail, the plastic damage area of the dam body cannot be recovered to the original state after the soil body is deformed and damaged, in order to better explain the deformation damage process of the dam body, a stress change cloud picture of which the working face is pushed to 500m, 600m, 700m, 800m, 850m, 900m, 910m, 920m, m and 2000m is selected as a key analysis object when the dam body reaches all plastic damage for the first time, the deformation damage rule and characteristics of the dam body are analyzed according to the simulation result, the stress change cloud picture of the dam body is shown in figure 12, the left side in the figure is a water-facing slope 930, the right side is a water-backing slope, the working face is pushed from the water-backing slope side to the water-facing slope side, an, the downward arrow indicates the compressive stress.
According to the stress change characteristics of the dam body at each position, the dam body undergoes a change process from tensile deformation damage to compression-reduction, only time nodes of the tensile-compression change process of each part are different, and the dam foot on the side of the backwater slope at the initial stage influenced by mining firstly undergoes tensile deformation damage, then the dam body on the side of the upstream slope and finally the middle position of the dam body. The process of changing from tension to compression also starts from the dam body at the side of the backwater slope, then the dam body at the side of the upstream slope and finally the middle position of the dam body.
And finally, observing the moving deformation of the dam body of the reinforced section and the non-reinforced section in the working face mining process by using a topcon GPS level gauge and a total station, arranging an observation line from the central position of the mining-influenced section of the dam body to the direction of the reservoir area at the top of the dam, setting 20 measuring points, wherein the distance between the measuring points is 30m, and the total length of the measuring line is 600 m. Designing the heightening and reinforcing length 290m of one side of the dam body according to the dam body maintenance scheme, wherein the arranged measuring point sections 1-11 are the dam bodies of the heightening, widening and reinforcing sections, the dam bodies of the non-heightening, widening and reinforcing sections are arranged outside the measuring point section 11, as shown in fig. 13, and the reference numerals 1-20 in the drawing represent the upper measuring points of the dam bodies.
According to the moving deformation characteristics of the dam body, the following steps are obtained: when the initial point influencing the moving deformation of the dam body is the moving deformation process of the whole dam body influenced by mining, in order to test the moving deformation process of the whole dam body influenced by mining, the moving deformation value of the dam body is observed every 50m of the working surface before the working surface is pushed to 600 m; in the process of propelling the working face by 600m to 1800m, observing once every 10 m; during the course of 1800m to 2000m of working face advance, every 50m of advance is observed. Taking the final sinking curve of each measuring point on the dam body as an example, the moving deformation characteristics of the dam body are analyzed, and the observed data are shown in table 4.
TABLE 4 Final sag values of dam body at each measurement point
According to the final subsidence value of each measuring point of the dam body measured in the table 4, the feasibility and the rationality of the dam body deformation damage analysis by the analysis method are verified, and a comparative analysis chart is shown in fig. 14. The final sinking curve of each measuring point of the dam body obtained in the figure 14 can be known as follows: the influence range of working face mining on the dam body is between 1 and 11 measuring points (reinforced section dam body), wherein the maximum sinking value of the No. 11 measuring point is 0.015m, the dam body reaches maximum sinking at the No. 1 and No. 2 measuring points, the sinking inflection points of the reinforced section dam body are positioned near the No. 8 and No. 9 measuring points and near the No. 3 measuring point, the slope of the sinking value of the dam body changes, increases and decreases, the sinking change of the dam body at the 12 to 20 measuring points is small (non-reinforced section dam body), the deformation damage of the dam body is small, the maximum sinking value is positioned at the No. 12 measuring point, and the maximum sinking value is 0.001 m. The length of the dam body affected by mining on one side is 270-300 m, and the length of the dam body affected by mining on one side is 280m by verifying the simplified analysis result. And selecting the observation results of the No. 1, No. 2 and No. 3 measuring points in the middle of the dam body, wherein the observed sinking values of the 3 measuring points are shown as 5.
TABLE 5 sinking values of test points No. 1,2, 3 in the working face Propulsion Process
And (3) according to the subsidence values of the measuring points No. 1, No. 2 and No. 3 of the dam body under different advancing lengths of the working surface in the table 5, drawing a subsidence change curve of the measuring points on the dam body under the influence of mining, as shown in fig. 15. From the measured point dip profile in fig. 15, it can be seen that: the sinking change trends of the measuring points No. 1, No. 2 and No. 3 under the mining influence are basically the same, which shows that the moving deformation characteristics of the measuring points of the dam body in the mining influence range of the working face are basically the same.
According to the influence range and the influence degree of the dam body affected by mining at the No. 1 measuring point, the sinking change rule of the measuring point at the center position of the dam body is simulated by combining numerical values, the moving deformation rule and the deformation damage characteristic of the dam body affected by mining are analyzed, and a comparative analysis chart is shown in FIG. 16. As can be seen in fig. 16: the sinking change trends of the center position of the dam obtained by the methods are basically the same, and the positions of the initial point, the inflection point and the end point of the moving deformation of the dam are basically the same, so that the moving deformation rule of the dam obtained by simplifying the numerical simulation method is further verified to be correct.
Claims (2)
1. A dam body deformation damage analysis method for mining deep coal seams under reservoir dams is characterized by comprising the following steps:
step 1: calculating a subsidence basin formed on the earth surface of the dam body after coal seam mining, and calculating the volume V of the subsidence basin by adopting earth surface movement deformation prediction software based on a probability integration method according to the earth surface after coal seam mining1Calculating by adopting full-size numerical simulation software to obtain the volume V of the sinking basin2，
Step 2: according to V1、V2Comparing the maximum sinking values of the two sinking basins, and selecting the sinking basin with the larger maximum sinking value as the sinking basinExcavating a basin for actual use;
and step 3: constructing a dam body moving deformation numerical model after mining of the fully mechanized caving face under the dam;
and 4, step 4: scaling the actual dam size into the dam size during simulation according to the similarity ratio of the surface structure to the actual surface structure in the dam movement deformation numerical model to obtain a simulated dam;
and 5: according to the position of an actual dam body in the ground surface, arranging the simulation dam body on the upper surface of the rock-soil layer to obtain an integral simulation model;
step 6: simulating a subsidence curve of the ground surface moving deformation according to the full-size numerical value, determining a subsidence basin of the ground surface moving deformation in the actual working face propelling process, and performing simulated excavation on the whole simulation model; when the earth surface movement deformation of the excavation area does not reach the dam body and the dam body does not sink, the simulation excavation step distance is set to be SsDetermining the simulated excavation volume L according to the subsidence basin of the full-size numerical simulation ground surface movement deformations(ii) a When the earth surface movement deformation of the excavation area reaches the dam body or the dam body sinks, the simulated excavation step distance is set to be Sm＝λSsThe simulated excavation amount is set to λ Ls,0＜λ＜1；
And 7: and (3) observing the moving deformation damage condition of the dam body during excavation by simulating excavation of the whole simulation model.
2. The method for analyzing the deformation and damage of the dam body of the deep coal seam mining under the reservoir dam as claimed in claim 1, wherein the step 3 comprises the following steps:
step 3.1: calculating by using formulas (1) to (3) according to the similarity ratio of the surface structure to the actual surface structure in the model to obtain the length, width and height of the simulated excavation basin to be constructed in the model;
am＝as(1)
bm＝bs(2)
hm＝hs(3)
wherein, amShowing the length of the simulated excavation basin, asLength of actual excavated basin, bmWidth of simulated excavation basin, bsWidth h representing actual excavated basinmHeight, h, of simulated excavated basinsRepresenting the height of the actual excavated basin;
step 3.2: according to the ground surface moving deformation range of the working surface under different propelling distances, the reserved lengths on the two sides of the simulated excavation basin are s along the length direction of the dam body1The boundary limiting condition of (1);
step 3.3: thickness s of overlying rock-soil layer on excavated basin2Thickness s of rock-soil layer covered and reserved on excavated basin2Greater than or equal to the height of the caving zone;
step 3.4: in order to ensure the slow continuity of the moving deformation of the rock-soil layer, a layer with the thickness of s is laid below the rock-soil layer3The transition material of (2), the transition material being required to have sufficient toughness and flexibility;
step 3.5: determining the length A, the width B and the height H of a dam body movement deformation numerical model to be constructed, wherein the length A is as follows:
A＝am+2s1(4)
width B is:
B＝bm(5)
the height H is:
H＝hm+s2+s3(6)。
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