CN111859517B - Dam deformation damage analysis method for deep coal seam exploitation under reservoir dam - Google Patents
Dam deformation damage analysis method for deep coal seam exploitation under reservoir dam Download PDFInfo
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Abstract
The invention provides a dam deformation damage analysis method for deep coal seam exploitation under a dam. Firstly, constructing a dam body movement deformation numerical model according to an actual excavation basin, simulating the dam body, constructing an integral simplified simulation model, then simulating a subsidence curve of the earth surface movement deformation according to full-size numerical values, determining the subsidence basin of the earth surface movement deformation in the actual working surface advancing process, simulating the integral simulation model, and observing the movement deformation damage condition of the dam body during excavation according to the constructed simulation model; the invention solves the problem that the conventional similar material simulation and numerical simulation are difficult to realize the deformation and damage of the observation dam body by simplifying the inversion of the structure, and has important guiding significance for the establishment of the safety protection and maintenance scheme of the dam.
Description
Technical Field
The invention relates to the technical field of mining, in particular to a dam deformation damage analysis method for deep coal seam mining under a reservoir dam.
Background
The problem of safe operation of the reservoir dam in the process of exploiting the deep coal seam below the reservoir dam always restricts the great difficulty of safe exploitation of the deep coal resources below the reservoir dam in China. To reasonably develop and utilize coal resources under the reservoir dam to the maximum extent, the deformation and damage mechanism of the dam body in the coal seam mining process must be mastered. However, the depth of the buried coal layer is large, the soil body structure of the earth surface reservoir dam is small, the ratio of the depth of the buried coal layer to the height of the dam body is large, the deformation damage size, the form, the damage degree and the like of the dam body are difficult to calculate by the conventional method, so that the problem of safety and stability of the deep coal layer under the reservoir dam for exploiting the dam body is always a hot spot and a difficult point for 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 existing computer is utilized to solve the problem that the time and the grid number are approximately N 4/3 Is in direct proportion to the whole simulationThe length of time required is very staggering; by using the existing similar material simulation device, the cross section of the dam body is too small compared with a full-size model, so that detailed observation on deformation damage of the dam body is difficult, and the deformation damage of the dam body cannot be accurately observed at all; and deducing the movement deformation of the dam body according to the mine pressure display rule of the roof of the coal bed, wherein the accuracy of the deduced result is difficult to ensure due to the complex roof stratum structure of the coal bed with overlarge burial depth. Therefore, a research method capable of rapidly and accurately observing and deducing deformation damage of the dam body is required to be explored, and theoretical guiding basis is provided for analysis of deformation damage mechanism of the under-reservoir mining dam body and evaluation of safety of the dam body.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a dam deformation damage analysis method for exploiting deep coal beds under a dam, which comprises the following steps:
step 1: calculating a sinking basin formed on the surface of a dam body after coal seam exploitation, and calculating the volume V of the sinking basin by adopting surface movement deformation prediction software based on a probability integration method according to the surface after coal seam exploitation 1 Calculating to obtain the volume V of the sinking basin by adopting full-size numerical simulation software 2 ,
Step 2: according to V 1 、V 2 Comparing the maximum sinking value in the two sinking basin, and selecting the sinking basin with the larger maximum sinking value as the actual excavation basin;
step 3: constructing a dam body movement deformation numerical model after the under-dam fully mechanized caving face is mined;
step 4: scaling the actual dam size into the simulated dam size according to the similarity ratio delta of the ground surface structure and the actual ground surface structure in the dam movement deformation numerical model to obtain a simulated dam;
step 5: according to the position of the actual dam body in the ground surface, arranging the simulated dam body on the upper surface of the rock-soil layer to obtain an integral simulation model;
step 6: determining a sinking basin of ground surface movement deformation in the actual working surface propelling process according to a sinking curve of ground surface movement deformation simulated by full-size numerical values, and integratingSimulating excavation by using a 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 simulated excavation step is set as S s Determining the simulated excavation amount L according to the sinking basin for simulating the movement deformation of the ground surface by full-size numerical values s The method comprises the steps of carrying out a first treatment on the surface of the When the earth surface movement deformation of the excavation area is spread to the dam body or the dam body is sunk, the simulated excavation step is set as S m =λS s The simulated excavation amount is set to be lambdaL s ,0<λ<1;
Step 7: and observing the movable deformation damage condition of the dam body during excavation through simulating excavation of the integral simulation model.
The step 3 comprises the following steps:
step 3.1: calculating by using the formulas (1) to (3) according to the similarity ratio delta of the ground surface structure and the actual ground surface structure in the model to obtain the length, width and height of the simulated excavation basin to be constructed in the model;
a m =δa s (1)
b m =δb s (2)
h m =δh s (3)
wherein a is m Representing the length of a simulated excavated basin, a s Representing the length of the actual excavated basin b m Representing the width of the simulated excavation basin b s Representing the width of the actual excavated basin, h m Representing the height of the simulated excavation basin, h s Representing the height of the actual excavated basin;
step 3.2: according to the movement deformation range of the ground surface under different propelling distances of the working surface, reserving lengths s at two sides of the simulated excavation basin along the length direction of the dam body 1 Boundary constraints of (2);
step 3.3: setting the thickness s of the overlying strata of the excavation basin 2 Excavating a reserved rock-soil layer thickness s on the basin 2 The height of the falling belt is larger than or equal to that of the falling belt;
step 3.4: in order to ensure the slow continuity of the moving deformation of the rock and soil layer, the rock and soil layer is formedA layer with the thickness s is laid below 3 The transition material needs 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=a m +2s 1 (4)
the width B is:
B=b m (5)
the height H is as follows:
H=h m +s 2 +s 3 (6)。
the beneficial effects of the invention are as follows:
the invention provides a dam deformation damage analysis method for deep coal seam exploitation under a dam, which is based on the time-space sequence evolution rule of overlying strata in a goaf after deep coal seam exploitation, and has the advantages of greatly reducing model size, reducing operation time and improving analysis precision of small targets by simplifying structural inversion and grasping deformation damage mechanism of a soil body structure of the dam, solving the problems that the deformation damage of the dam is difficult to realize by conventional similar material simulation and numerical simulation and the establishment of a dangerous evaluation index system of the dam after deep coal seam exploitation under the dam is important guiding significance for establishing a safety protection and maintenance scheme of the dam.
Drawings
FIG. 1 is a schematic diagram of the under-dam mining overburden and the surface movement deformation and the process decomposition schematic diagram thereof, wherein FIG. (a) shows the schematic diagram of the under-dam mining overburden and the surface movement deformation and FIG. (b) shows the schematic diagram of the under-dam mining overburden and the surface movement deformation process decomposition;
FIG. 2 is a schematic diagram of an overall simulation model constructed in accordance with the present invention;
FIG. 3 is a schematic diagram of the excavation sequence of the overall simulation model of the present invention;
FIG. 4 is a schematic diagram of an excavation paving design in a simulation of the present invention;
FIG. 5 is a diagram of a model structure constructed by the simulation experiment of the present invention;
FIG. 6 is a schematic diagram of model excavation to be experimentally constructed in accordance with the present invention;
FIG. 7 is a graph showing the comparison of the movement deformation of the dam when the excavation is simulated to different positions, wherein graph (a) shows the comparison of the movement deformation of the dam when the back water side dam foot 24m of the dam is pushed through, graph (b) shows the comparison of the movement deformation of the dam when the back water side dam foot 28m of the dam is pushed through, graph (c) shows the comparison of the movement deformation of the dam when the back water side dam foot 38m of the dam is pushed through, graph (d) shows the comparison of the movement deformation of the dam when the back water side dam foot 52m of the dam is pushed through, graph (e) shows the comparison of the movement deformation of the dam when the back water side dam foot 58m of the dam is pushed through, graph (f) shows the comparison of the movement deformation of the dam when the back water side dam foot 64m of the dam is pushed through, graph (g) shows the comparison of the movement deformation of the dam when the back water side dam foot 84m of the dam is pushed through, graph (i) shows the comparison of the movement deformation of the dam foot 124m of the back water side dam against the comparison of the dam foot;
FIG. 8 is a simulation model constructed in modeling software in accordance with the present invention;
FIG. 9 is a graph of the positional relationship between a dam and a working surface constructed in modeling software according to the present invention;
FIG. 10 is a graph of dip for points at centerline positions of a dam of varying advancing lengths in accordance with the present invention;
FIG. 11 is a graph of the final dip value of the dam according to the present invention;
FIG. 12 is a graph showing the stress variation trend of a dam body with different advancing lengths according to the present invention, wherein a graph (a) shows a stress graph before a working surface is advanced to 600m, wherein a graph (b) shows a stress graph when a working surface is advanced to 800m, wherein a graph (c) shows a stress graph when a working surface is advanced to 900m, wherein a graph (d) shows a stress graph when a working surface is advanced to 920m, wherein a graph (e) shows a stress graph when a working surface is advanced to 930m, and wherein a graph (f) shows a stress graph when a working surface is advanced to 2000 m;
FIG. 13 is a diagram of a dam movement deformation measuring point arrangement during actual under-dam mining;
FIG. 14 is a graph showing the comparison of measured point dip values during numerical simulation according to the method of the present invention with measured point dip values during actual under-dam mining;
FIG. 15 is a graph showing the variation of subsidence at different advancing lengths of measuring points No. 1, no. 2 and No. 3 in actual under-dam mining according to the present invention;
FIG. 16 is a graph showing the comparison of dip curves of measuring points 1 of the dam body under different advancing lengths in the actual under-dam exploitation and numerical simulation of the method of the invention;
in the figure, 1, a dam body, 2, reservoir water, 3, ground surface, 4, a coal bed, 5, a bottom plate rock stratum, 6, overlying strata, 7 and a rock stratum.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples of specific embodiments.
After exploiting the coal seam under the dam, the moving deformation of the goaf overlying strata is from bottom to top, and the moving deformation firstly reaches the ground surface around the dam body and the dam foundation, and then drives the dam body to move together. In the process, the sequence and the size of the movement deformation of each part of the dam body are different according to the position relation between the dam body and the sinking basin.
Decomposing the transmission process of the deformation damage of the overlying strata, namely dividing the transmission process into two parts, wherein the moving deformation of the overlying strata and the ground surface caused by the mining of the working surface is utilized to obtain sinking basin bodies with different sizes which are formed along with the propulsion of the working surface; and secondly, the dam body driven by the gradually enlarged sinking basin moves and deforms to obtain the movement and deformation of different parts of the dam body which continuously expands along with the sinking basin.
It is assumed that if the process of working face mining and sinking basin forming can be omitted, the basin is directly excavated according to the process of sinking basin forming, 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 shortened, the analysis precision of small targets is improved, a diagram of under-dam mining overburden and ground surface moving deformation is shown in a diagram (a) in fig. 1, and a diagram of the coal seam overburden in the diagram (a) after the separation of the water body and the dam body is shown in a diagram (b) in fig. 1.
The key to achieving this assumption is: firstly, constructing a numerical model capable of accurately reproducing the movement deformation of the earth surface and the dam body; and secondly, decomposing the sinking basin forming process to form the basin digging amount corresponding to the step length of the pushing of the working face.
The subsidence basin corresponding to the working face propulsion step length can be obtained by ground surface movement deformation prediction and full-size numerical simulation by a probability integration method, space-time sequence inversion is carried out by the movement deformation size of each point of the ground surface, and deformation damage of a dam body is calculated.
As can be seen from fig. 1 (b): if excavation is directly carried out on the earth surface, namely the dam bottom interface, the deformation and damage of the dam body also immediately generate corresponding movement and deformation and even damage along with the excavation mode and the excavation amount. This is not consistent with the slow and continuous deformation caused by deep working face mining, and cannot reflect the variation of the actual deformation and damage process of the dam body, at this time, the deformation and damage of the dam body deviates seriously from the actual moving deformation process, and the result is not preferable. In order to solve the problem, the simulation can reproduce the deformation and damage of the dam body caused by coal seam exploitation, and a buffer rock layer with a certain thickness is reserved below the ground surface, so that a series of problems caused by direct excavation of the ground surface are avoided.
Therefore, the invention provides a dam deformation damage analysis method for deep coal seam exploitation under a dam, which comprises the following steps:
step 1: calculating a sinking basin formed on the surface of a dam body after coal seam exploitation, and calculating the volume V of the sinking basin by adopting surface movement deformation prediction software based on a probability integration method according to the surface after coal seam exploitation 1 Calculating to obtain the volume V of the sinking basin by adopting full-size numerical simulation software 2 ,
Step 2: according to V 1 、V 2 Comparing the maximum sinking value in the two sinking basin, and selecting the sinking basin with the larger maximum sinking value as the actual excavation basin;
step 3: constructing a dam body movement deformation numerical model after the under-dam fully mechanized caving face mining, as shown in fig. 2, comprising:
step 3.1: calculating by using the formulas (1) to (3) according to the similarity ratio delta of the ground surface structure and the actual ground surface structure in the model to obtain the length, width and height of the simulated excavation basin to be constructed in the model;
a m =δa s (1)
b m =δb s (2)
h m =δh s (3)
wherein a is m Representing the length of a simulated excavated basin, a s Representing the length of the actual excavated basin b m Representing the width of the simulated excavation basin b s Representing the width of the actual excavated basin, h m Representing the height of the simulated excavation basin, h s Representing the height of the actual excavated basin;
step 3.2: according to the movement deformation range of the ground surface under different propelling distances of the working surface, reserving lengths s at two sides of the simulated excavation basin along the length direction of the dam body 1 Boundary constraints of (2);
the determination of the thickness of the reserved rock and soil layer needs to consider two problems, namely, if the thickness is too large, excavation cannot be carried out according to a basin formed by the earth surface, and the overall excavation amount and the shape of the depth are difficult to determine; if the thickness is too small, the surface and dam degeneration damage will occur as a result of shallow coal seam characteristics, and slow continuous deformation will not be reproduced.
According to the three-belt structure of goaf overlying strata modification damage, the thickness of the reserved rock soil layer is at least larger than the height of the falling belt, and the earth surface can be ensured not to be cut or fall.
Step 3.3: setting the thickness s of the overlying strata of the excavation basin 2 Excavating a reserved rock-soil layer thickness s on the basin 2 The height of the falling belt is larger than or equal to that of the falling belt;
in order to excavate according to the shape of the subsurface subsidence basin, a layer of material with enough toughness and flexibility is arranged under the rock layer, so that the moving deformation of the rock layer is ensured to be slow and continuous, the purpose of simulating the actual deformation and damage process of the dam body is realized, the selection of the layer of material can ensure the tight contact with the new surface formed by excavation, and the rock layer on the layer of material moves and deforms along with the new surface.
Step 3.4: in order to ensure the slow continuity of the moving deformation of the rock and soil layer, a layer of thickness s is paved below the rock and soil layer 3 The transition material needs 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=a m +2s 1 (4)
the width B is:
B=b m (5)
the height H is as follows:
H=h m +s 2 +s 3 (6)
step 4: scaling the actual dam size into the simulated dam size according to the similarity ratio delta of the ground surface structure and the actual ground surface structure in the dam movement deformation numerical model to obtain a simulated dam;
step 5: according to the position of the actual dam body in the ground surface, arranging the simulated dam body on the upper surface of the rock-soil layer to obtain an integral simulation model;
the basin used for excavating can be selected from a sinking basin obtained by full-size numerical simulation or a sinking basin obtained by ground surface movement deformation prediction, the excavating step distance can be divided into two parts, wherein one part is that a larger step distance is arranged before a dam body sinks, a smaller step distance is arranged a certain distance before the dam body sinks, and each excavating is carried out according to a curved surface body formed by a middle-upper thick edge and a thin edge between two adjacent excavating curved surfaces.
Step 6: according to the full-size numerical simulation of the subsidence curve of the ground surface movement deformation, determining the subsidence basin of the ground surface movement deformation in the actual working surface propelling process, and carrying out simulation excavation on the whole simulation model; when the earth surface movement deformation of the excavated area does not reach the dam bodyWhen the dam body does not sink, the simulated excavation step is set as S s Determining the simulated excavation amount L according to the sinking basin for simulating the movement deformation of the ground surface by full-size numerical values s The method comprises the steps of carrying out a first treatment on the surface of the When the earth surface movement deformation of the excavation area is spread to the dam body or the dam body is sunk, the simulated excavation step is set as S m =λS s The simulated excavation amount is set to be lambdaL s A schematic diagram of the excavation sequence is shown in FIG. 3, wherein 1,2, … and n represent the excavation sequence.
Step 7: by simulating excavation of the integral simulation model, the movable deformation damage condition of the dam body during excavation is observed, the deformation damage characteristics, excavation size and other works of the inner part of the dam body are recorded until the movable deformation of the dam body is stable, and the deformation damage rules and characteristics of the inner part of the dam body along with the advancing and sinking change of the working surface are summarized and analyzed according to the deformation damage states of the inner part of the dam body in each stage and are used for guiding the mining work of deep coal beds under the reservoir dam in actual production.
In order to verify that the dam movement deformation damage condition obtained by the analysis method is consistent with the dam movement deformation damage condition generated during actual excavation, the dam movement deformation damage condition is verified through simulation experiments and numerical simulation respectively.
The simulation experiment verification process is as follows:
and converting various physical and mechanical indexes of the coal rock into similar indexes of the model according to geological mining conditions of the first mining surface, and establishing a similar material simulation experiment model. According to connotation of a simplified analysis method for deformation damage of the under-dam mining dam body, simulation analysis is carried out on the deformation damage of the dam body, the deformation damage state of the dam body is observed, and the obtained result is utilized to analyze the real deformation damage rule and characteristics of the dam body, so that a basis is provided for the design of a maintenance scheme of the dam body.
The experimental platform adopts an aspect ratio of 10:1, and adopts an experimental platform of Qiankun Xingjingmao industry and trade limited company in Qingdao, and a set of similar material experimental platform is designed and manufactured according to the ratio of 10:1. According to the size of a dam body, the depth and the range of a subsurface 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 long by 20cm wide by 60cm high, the whole frame of the experiment platform is formed by welding steel structures, the smoothness of the platform is maintained by pasting a snow plate on the inner side filling plane, the observation front side of the experiment platform is provided with 10mm thick toughened glass, and grid scale lines of 0.5cm by 0.5cm are pasted on the glass, so that paste filling and observation of various deformation values in the experiment process are facilitated.
According to the specific conditions of the simulation object, the size of the subsurface basin and the model construction method establish a similar material simulation model along the direction vertical to the trend of the dam body. Determining that the model length ratio of the actual geological model to the simulation of the similar material is alpha by referring to the similarity criteria of three aspects of geometric similarity ratio of the appearance shape, motion similarity ratio of the moving deformation process and dynamic similarity ratio of the field actual environment L =200, intensity ratio α σ Time ratio of α=270 t =14.1. In order to ensure the quality of the model effect, a rock soil layer (surface soil layer 20m and lower sandstone section 10 m) of 30m is reserved on the excavated body. The filling of the model consists of a rock soil layer and an excavation body, wherein the filling size of the rock soil layer is 200cm long by 20cm wide by 22.145cm high; the filling size of the excavation body is 20cm long by 2cm wide by 3.645cm high. The widths of the dam crest and the dam foundation are respectively 2.5cm and 18.04cm, and the angles of the slope of the water facing slope and the slope of the back water slope are respectively 22 degrees and 27 degrees.
As shown in fig. 4, the simulated excavation body in the experiment is replaced by rectangular solid wood strips, and the dimensions of the wood strips are determined according to the similarity ratio, namely 20cm long by 2cm wide by 0.405cm high (right wood strip in fig. 4) and 20cm wide by 1cm high by 0.405cm long (left wood strip in fig. 4), so that the subsidence curves of the ground surface movement deformation can be reproduced, and the overlapping between the wood strips is staggered, so that the excavation body forms a subsidence basin.
And in the experimental model, the rock-soil body indexes are converted by taking the density and the tensile strength of the rock-soil layer as main control indexes, and then the elastic modulus and the poisson ratio are adopted. And converting physical and mechanical indexes of the dam body and the rock-soil body under the dam according to the strength similarity ratio, and searching the conversion indexes of the rock-soil bodies and the material proportion table corresponding to the indexes from the comprehensive experimental book of mining of the university of Liaoning engineering technology, wherein the conversion indexes and the material proportion table are shown in table 2, and the material proportion number is shown in table 3.
Table 2 conversion index and ratio number of each rock and soil layer
Table 3 similar materials proportioning table
In order to improve experimental precision and ensure better experimental effect, the model is filled in layers, the excavated body is placed layer by adopting battens, and smoothness and compactness are ensured. Each layer of the excavated body is covered with the thickness of 0.5cm, and is filled and compacted in a layer-by-layer independent proportion according to the proportion number of each rock-soil layer. After the model is manufactured, the model needs 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 completed model is shown in fig. 5.
According to the ground surface movement deformation range and the length of the model per se under different advancing distances of a working face, 20m is reserved at two ends of the design model as boundary limiting conditions, the model is excavated 35 times in total, the maximum excavating length is 10cm, the minimum excavating length is 2cm, the single excavating is based on the ground surface subsidence reaching a stable state, the excavating mode is used for excavating according to the advancing direction of the working face (excavating from left to right), the simulated excavating schematic diagram is shown in fig. 6, the boundary of a back water slope of a dam body is 116.53cm, the distance between the other side of the dam body and the model boundary is 65.44cm, the total width of the excavated body is 3.645cm, wherein the first excavating simulating step distance is 11.77cm, the second excavating simulating step distance is 3.13cm, the third excavating simulating step distance is 4.87cm, the fourth excavating step distance is 6.76cm, the fifth excavating simulating step distance is 10cm, then the excavating is continuously simulated with the step distance of 10cm, the excavating is reduced to 2cm when the simulated excavating is performed under the dam, and the other side of the dam body is simulated excavating step distance is 10cm.
And excavating wood strips at the lower part of the simulated rock stratum according to the excavation steps and the excavation range, and observing the movement deformation characteristics of the dam body. And selecting the movement deformation comparison chart of 10 excavation processes for analyzing the deformation damage rule and characteristics of the dam body by 10 sections of the dam foot 24m, 28m, 38m, 52m, 58m, 64m, 84m, 104m, 124m and 144m pushed through the dam back water side of the dam body according to each characteristic point affecting the movement deformation of the dam body in the similar material simulation process, wherein the movement deformation comparison chart is shown in fig. 7.
The mining effect process described above, simulated by fig. 7, can be seen: the dam body is subjected to a change process from tensile deformation damage to compression-reduction, only the time nodes of the tensile-compression conversion process of each part are different, the back water slope side dam foot is subjected to tensile deformation damage at the beginning stage under the influence of mining, the back water slope side dam body is the water slope side dam body, and the middle position of the dam body is the middle position. The process of converting from stretching to compression is also started from the back water slope side dam, then the front water slope side dam and finally the middle part of the dam.
The final sinking value of the dam body is 7m, the excavation height of the excavation part is 7.29m, and as 30m high rock-soil layers are covered on the excavation part, the final sinking value of the dam body is 6.99m according to the minimum residual broken expansion coefficient of 0.01 after the rock-soil layers are damaged, the final sinking value is only 0.01m different from the actual observed sinking value of the dam body, the error is small, and the fact that the simplified similar material simulation is feasible and reasonable for the sinking simulation of the dam body is verified.
The deformation and damage process of the dam body is in accordance with the movement deformation characteristics of the earth surface after the working surface is adopted at each position of the earth surface subsidence curve, and the simplified model analysis method is proved to have certain scientificity and rationality.
The numerical simulation verification process is as follows:
FLAC3D numerical simulation software is still selected for the numerical simulation of deformation damage of the under-dam mining dam body, and the simulation scheme design is divided into 4 parts of model establishment, model setting, excavation scheme and measuring point arrangement.
And predicting subsidence values of any points on the ground surface after the mining of the working surface under the dam by utilizing a probability integration method, importing three-dimensional space coordinates corresponding to the subsidence values of any points into Midas modeling software, and drawing a subsidence basin for the movement deformation of the ground surface of the working surface under the mining dam by utilizing point-surface coupling calculation of the software. The built model is shown in fig. 8.
Gradient stress is applied in the horizontal direction, and vertical stress of 0.0341MPa is applied to a 3.41m deep water body on the upstream slope side of the dam body as a water body load.
114 observation points are arranged on the central line of the dam body in the trend direction of the dam, the distance between the observation points is 5m, and the length of the measurement line is 570m. Setting up dam observation cross sections at each measuring point for analyzing displacement, deformation, stress, damage rules and characteristics of each cross section of the dam, wherein the position relation between the dam and the working surface is shown as figure 9, in the figure, the S2S9 working surface represents a fully-mechanized caving working surface, the width of a built model is 600m, the width of the S2S9 working surface is 277m, and the width from two smooth grooves of the working surface to the boundary of the model is 160.7cm;
according to simulation calculation results of working faces under different propelling lengths, monitoring data of points of a dam body survey line along with working face exploitation are extracted, sinking curves of under-dam exploitation dam bodies along with exploitation changes are drawn, the ground surface sinking curves of the working faces under different propelling lengths are summarized, and rules and characteristics of dam body movement deformation caused by exploitation are analyzed. FIG. 10 is a graph of dip at points at the centerline of the dam for different running lengths of the working surface. As can be seen from fig. 10: when the working face advances 470m (630 m from the midpoint of the dam body survey line), the dam body starts to be influenced by mining, and the maximum sinking value of the center position of the dam body is 0.092m; when the dam line is pushed to 1800m (pushed by 700m at the midpoint of the dam line), the center position of the dam line reaches the maximum sinking value of 7.17m under the condition. From this, the line midpoint dip starting point is located at 470m from the cut hole, the end point is located at 1800m from the cut hole, and the distance affected by production is 1170m. The rate of deflection of the dam is greatest (inflection point-slope magnitude demarcation point) when the working surface is pushed to 1100 m. And drawing a dam body sinking curve by using the sinking value of the midpoint of the measuring line when the working face mining is finished, namely sinking stability, wherein the distance between the measuring points is 20m in the drawing, and the measuring points are numbered from left to right in sequence as shown in fig. 11.
As can be seen from fig. 11: when the working face is pushed out, the maximum sinking position of the dam body is positioned at the center of the dam body, a flat basin is basically formed, and the maximum sinking value is 7.17m. The dam sinking rate in the ranges of 140 m-180 m and 380 m-420 m (100 m-140 m on both sides of the center position of the working face) is larger in transition (characteristic point-inflection point), and the slope of the dam sinking curve in the ranges of 180 m-260 m and 300 m-380 m (20 m-100 m on both sides of the center position of the working face) is the largest. The maximum sinking value of the two ends of the dam body is 0.14m, the influence of mining is minimum, and the influence range of working face mining on one side of the dam body is about 280m.
According to the displacement change analysis result, the influence of the mining on the dam body starts from the position 630m (the maximum sinking value of the center position of the dam body is 0.092 m) away from the center position of the dam body, in order to be able to describe the deformation and damage process of the dam body in detail, the plastic damage area of the dam body cannot be restored to the original state after the soil body is deformed and damaged, in order to better describe the deformation and damage process of the dam body, when the dam body reaches all plastic damage for the first time, the working face is selected as an important analysis object, the working face is selected to be pushed to a stress change cloud chart of 500m, 600m, 700m, 800m, 850m, 900m, 910m, 920m, 930m and 2000m according to the simulation result, the deformation and damage rule and characteristics of the dam body are analyzed, the dam body stress change cloud chart is shown in fig. 12, the left side of the figure is a water facing slope, the right side of the working face is pushed by the water facing the slope side, the upward arrow in the figure indicates the tensile stress, and the downward arrow indicates the compressive stress.
According to the stress change characteristics of each position of the dam body, the dam body is subjected to a change process from tensile deformation damage to compression-reduction, only the time nodes of the tensile-compression conversion process of each position are different, the back water slope side dam feet are subjected to tensile deformation damage at the beginning stage under the influence of mining, the back water slope side dam body is the water slope side dam body, and the middle position of the dam body is the middle position. The process of converting from stretching to compression is also started from the back water slope side dam, then the front water slope side dam and finally the middle part of the dam.
Finally, observing the movement deformation of the dam body of the reinforcing section and the dam body of the non-reinforcing section in the working face mining process by utilizing a topcon GPS level gauge and a total station, distributing an observation line on the dam top from the central position of the mining-affected section of the dam body to the direction of a reservoir area, setting 20 measuring points, wherein the distance between the measuring points is 30m, and the total length of the measuring lines is 600m. The method is characterized in that the heightening and reinforcing length 290m of a single side of the dam body is designed according to the maintenance scheme of the dam body, wherein the arranged 1-11 measuring point sections are the dam body of the heightening, widening and reinforcing sections, and the other than the 11 measuring points are the dam body of the non-heightening, widening and reinforcing sections, as shown in fig. 13, and the reference numerals 1-20 in the drawing represent measuring points on the dam body.
According to the movement deformation characteristics of the dam body, the following steps are known: when the starting point of the movable deformation affecting the dam body is that the working surface is pushed to 600m, in order to check the movable deformation process of the whole dam body affected by mining, before the working surface is pushed to 600m, the movable deformation value of the dam body is observed every 50m of the working surface; in the process of pushing the working surface for 600m to 1800m, observing every 10m pushing; during the advancing process of the working surface from 1800m to 2000m, observation is performed once every 50m advancing process. Taking the final sinking curve of each measuring point on the dam body as an example, the movement deformation characteristics of the dam body are analyzed, and the observation data are shown in table 4.
TABLE 4 final dip values for each station of the dam
The feasibility and rationality of analyzing the deformation damage of the dam body by the analysis method are verified according to the final sinking value of each measuring point of the actual measured dam body in table 4, and a comparison analysis chart is shown in fig. 14. The final dip curve of each measuring point of the dam body obtained in fig. 14 can be seen as follows: the influence range of working face mining on the dam body is between 1-11 measuring points (reinforced section dam body), wherein the maximum sinking value of the 11-measuring point is 0.015m, the dam body at the 1-2 measuring point reaches the maximum sinking, the sinking inflection point positions of the reinforced section dam body are near the 8-9 measuring point and near the 3-measuring point, the slope of the sinking value of the dam body changes, the sinking change of the dam body is increased and reduced, the sinking change of the dam body of the 12-20 measuring points is smaller (non-reinforced section dam body), the deformation damage of the dam body is also smaller, the maximum sinking value is at the 12-measuring point position, and the maximum sinking value is 0.001m. The length of one side of the dam body affected by mining is 270-300 m, and the result of simplified analysis is verified to obtain that the length of one side of the dam body affected by mining on the working face is 280m. And selecting observation results of 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 dip values for points 1,2, 3 during face advancement
According to the sinking values of the measuring points 1,2 and 3 of the dam body under different advancing lengths of the working surface in table 5, a sinking change curve of the 3 measuring points on the dam body under the influence of mining is drawn, as shown in fig. 15. From the plot of the dip change at the station in fig. 15, it can be seen that: the sinking change trend of the No. 1, no. 2 and No. 3 measuring points affected by mining is basically the same, which indicates that the movement deformation characteristics of each measuring point 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 mining of the dam body at the point 1, the sinking change rule of the point at the center of the dam body is simulated by combining the numerical values, the movement deformation rule and the deformation damage characteristic of the influence of the mining of the dam body are analyzed, and a comparison analysis chart is shown in fig. 16. As can be seen from fig. 16: the sinking change trend of the center position of the dam body obtained by the method is basically the same, and the positions of the starting point, the inflection point and the ending point of the movement deformation of the dam body are basically the same, so that the accuracy of the movement deformation rule of the dam body obtained by simplifying the numerical simulation method is further verified.
Claims (2)
1. A dam deformation damage analysis method for deep coal seam exploitation under a dam is characterized by comprising the following steps:
step 1: calculating a sinking basin formed on the surface of a dam body after coal seam exploitation, and calculating the volume V of the sinking basin by adopting surface movement deformation prediction software based on a probability integration method according to the surface after coal seam exploitation 1 Calculating to obtain the volume V of the sinking basin by adopting full-size numerical simulation software 2 ,
Step 2: according to V 1 、V 2 Comparing the maximum sinking values in the two sinking basins, and selecting the maximum sinking value to be comparedThe large sinking basin is used as the actual excavation basin;
step 3: constructing a dam body movement deformation numerical model after the under-dam fully mechanized caving face is mined;
step 4: scaling the actual dam size into the simulated dam size according to the similarity ratio delta of the ground surface structure and the actual ground surface structure in the dam movement deformation numerical model to obtain a simulated dam;
step 5: according to the position of the actual dam body in the ground surface, arranging the simulated dam body on the upper surface of the rock-soil layer to obtain an integral simulation model;
step 6: according to the full-size numerical simulation of the subsidence curve of the ground surface movement deformation, determining the subsidence basin of the ground surface movement deformation in the actual working surface propelling process, and carrying out simulation 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 simulated excavation step is set as S s Determining the simulated excavation amount L according to the sinking basin for simulating the movement deformation of the ground surface by full-size numerical values s The method comprises the steps of carrying out a first treatment on the surface of the When the earth surface movement deformation of the excavation area is spread to the dam body or the dam body is sunk, the simulated excavation step is set as S m =λS s The simulated excavation amount is set to be lambdaL s ,0<λ<1;
Step 7: and observing the movable deformation damage condition of the dam body during excavation through simulating excavation of the integral simulation model.
2. The method for analyzing deformation damage of a dam for mining deep coal beds under a dam according to claim 1, wherein the step 3 includes:
step 3.1: calculating by using the formulas (1) to (3) according to the similarity ratio delta of the ground surface structure and the actual ground surface structure in the model to obtain the length, width and height of the simulated excavation basin to be constructed in the model;
a m =δa s (1)
b m =δb s (2)
h m =δh s (3)
wherein a is m Representing the length of a simulated excavated basin, a s Representing the length of the actual excavated basin b m Representing the width of the simulated excavation basin b s Representing the width of the actual excavated basin, h m Representing the height of the simulated excavation basin, h s Representing the height of the actual excavated basin;
step 3.2: according to the movement deformation range of the ground surface under different propelling distances of the working surface, reserving lengths s at two sides of the simulated excavation basin along the length direction of the dam body 1 Boundary constraints of (2);
step 3.3: setting the thickness s of the overlying strata of the excavation basin 2 Excavating a reserved rock-soil layer thickness s on the basin 2 The height of the falling belt is larger than or equal to that of the falling belt;
step 3.4: in order to ensure the slow continuity of the moving deformation of the rock and soil layer, a layer of thickness s is paved below the rock and soil layer 3 The transition material needs 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=a m +2s 1 (4)
the width B is:
B=b m (5)
the height H is as follows:
H=h m +s 2 +s 3 (6)。
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