CN117151348A - Method for distinguishing mining overburden high-level separation layer water burst type - Google Patents
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Abstract
The invention provides a method for distinguishing the water burst type of a mining overburden high-level separation layer, which relates to the technical field of underground safety production and specifically comprises the following steps: carrying out hydrogeological condition analysis and determining the spatial relationship between the water-bearing layer and the water-resisting layer of the coal seam roof; establishing a hydrographic engineering geological model of a coal seam roof; judging the conventional roof fracture type water damage by utilizing the development height of the water guide fracture zone; performing combination division of roof and rock strata of a coal bed, and establishing separation layer evolution of overlying strata of the coal bedA model; performing separation layer water formation analysis, describing a dynamic process of separation layer development, and analyzing water filling conditions of separation layer space; comparison of the firstjBreaking distance of rock stratuml j Judging the hydrostatic pressure water damage of the high-order separation layer according to the relation with the existing breaking distance; and calculating the maximum range of the impact damage zone, and judging the water damage of the high-order separation layer. The technical scheme of the invention solves the problem that the prior art lacks quantitative evaluation standards for different water damage types in separation layers.
Description
Technical Field
The invention relates to the technical field of underground safety production, in particular to a method for distinguishing the type of water burst of a mining overburden high-level separation layer.
Background
The water disaster of separation layer is the common water disaster type of deep mine in recent years, and the characteristics of large instantaneous water quantity, unobvious water burst symptom and the like seriously threaten the safe and efficient development of coal resources of the deep mine.
The formation of the separation layer space is mainly caused by uneven settlement among overlying strata after coal seam mining, and when the separation layer space is provided with a water supply source, a water guide channel and the like, water is easy to accumulate in the separation layer space to form separation layer water. Along with the continuous promotion of the working face, the separation layer space is continuously enlarged, the separation layer water quantity is increased, and when certain disaster conditions are met, the separation layer water breaks through the water-resisting layer below, and the working face is flushed, so that the mine safety production is threatened. How to scientifically and effectively judge different water disaster types of separation layers and provide guarantee for mine safety production and operation is a key problem faced by the existing mine safety technical field.
At present, a distinguishing method for water damage of a separation layer mainly judges a hard rock stratum based on a key layer theory and combines basic forming conditions of the water of the separation layer, and the distinguishing method comprises the following steps: the sustainable separation space, the supply channel and the stable supply water source are used for distinguishing separation water burst. On the other hand, the water burst (gushing) prediction of the overlying strata is carried out by adopting different comprehensive evaluation methods through selecting evaluation indexes such as water burst pressure of the separation layer, thickness of the unbroken protective layer, evaluation indexes of the closing degree of mudstone cracks in the broken protective layer, evaluation indexes of the closing degree of sandstone cracks in the broken protective layer and the like.
In recent years, many domestic and foreign scholars have conducted intensive researches on the problems of mechanism, recognition, prevention and the like of water burst from separation layers, and have obtained rich results, so that people's knowledge on the mechanism and phenomenon of water burst from separation layers is promoted. However, in the actual production process, along with the continuous promotion of the working surface, the development position of the separation layer continuously rises, and a new high-order separation layer burst (gushing) water hazard is formed. At present, quantitative evaluation standards for the type of delamination water damage are lacking, so that scientific and effective guidance is provided for underground safe production.
Therefore, a comprehensive and systematic mining overburden high-order separation layer water burst type distinguishing method is needed.
Disclosure of Invention
The invention mainly aims to provide a method for distinguishing the water burst type of a mining overburden high-order separation layer, so as to solve the problem that quantitative evaluation standards for different separation layer water hazard types are lacking in the prior art.
In order to achieve the above purpose, the invention provides a method for distinguishing the water burst type of a mining overburden high-level separation layer, which specifically comprises the following steps:
s1, carrying out hydrogeological condition analysis and determining the spatial relationship between the water-bearing layer and the water-resisting layer of the roof of the coal seam.
S2, establishing a seam roof hydrologic engineering geological model, namely defining the horizon sequence of each layer, and obtaining seam roof hydrologic and engineering geological parameters.
S3, judging a type of water damage, namely the traditional roof fracture type water damage by utilizing the development height of the water guide fracture zone.
S4, based on the coal seam roof hydrologic engineering geological model and the key layer discrimination method, carrying out the combination division of the coal seam roof strata, and establishing a coal seam overlying strata separation layer evolution model.
S5, performing separation layer water formation analysis, describing the dynamic process of separation layer development, and analyzing the water filling condition of separation layer space.
S6, calculating the first step according to the simple beam force theory and combined with Darcy lawBreaking distance->Comparison of->Breaking distance->And the relationship with the existing breaking distance is used for judging the second class of water damage, namely the hydrostatic pressure water damage of the high-order separation layer.
S7, calculating the maximum range of the impact fracture zoneAnd according toCalculate the firstBreaking distance of rock stratumComparison of the firstBreaking distance of rock stratumThree types of water damage, namely, the discrimination of the water damage of the high-order separation layer moving water, are carried out according to the relation with the existing breaking distance.
Further, in step S2, based on the hydrogeology and borehole data analysis, each stratum group is numbered 1 sequentially from bottom to top, 2....i.. I, defining lithology and thickness of each stratumWeight per unit>Osmotic coefficient->Tensile Strength->Modulus of elasticityAnd (5) determining the layer sequence, and obtaining the hydrological parameters and engineering geological parameters of the coal seam roof.
Further, the step S3 specifically includes the following steps:
s3.1, determining the development height of the water-guiding fracture zone of the roof of the main coal mining layer by adopting a method of actual measurement, analogy or empirical formulaComparison ofAnd，representing the distance between the roof of the coal seam and each water-bearing rock formation, calculated using equation (1)：
(1)；
Wherein the method comprises the steps ofRepresenting the thickness of each formation between the roof of the coal seam and the floor of the aquifer.
S3.2 whenWhen the water-guiding fracture zone is in the water-bearing layer, the water-guiding fracture zone is advanced along with the working surface, the water-guiding fracture zone is developed to the water-bearing layer, groundwater is caused to flow into the working surface, and the traditional roof fracture type water damage, namely a type of water damage, is caused;
when (when)And when the water-bearing layer is not existed in the water-guiding crack zone, the water-bearing layer is not threatened by a class of water damage.
Further, the step S4 specifically includes the following steps:
s4.1, the generation of the separation layer firstly needs to meet the following rigidity and deflection conditions:
(2)；
in the method, in the process of the invention,、/>for the rock rigidity of the upper and lower layers of the delamination interface, < +.>、/>Is the rock mass deflection of the upper and lower layers of the separation layer interface.
S4.2, assuming that a first horizon formation in the rock formations is a first key layer, the first horizon formation can control the range of overburden formations to reach a first levelLayer formation, then->The rock layers of the horizon are required to satisfy if the rock layers are key layers:
(3)；
in the method, in the process of the invention,，/>calculated to be->Layer and->The first critical layer is subjected toLoad; />For the elastic modulus of the rock stratum>Is->Layer thickness->Is->Layer rock layer weight.
S4.3, the critical layer discrimination meets the requirement of the formula (3) and also meets the strength condition of the critical layer theory, namely, the breaking distance of the overlying hard rock layer is required to be larger than that of the underlying hard rock layer, and the overlying hard rock layer is provided with the following total componentsLayer hard rock formation:
(4)；
in the method, in the process of the invention,for a determined number of hard rock layers; />Is->Breaking distance of rock stratum; />For the thickness of the rock layer>For the tensile strength of the rock formation>Is the load born by the rock stratum.
If at firstThe hard rock layer does not satisfy the formula (4), the +.>The total stratum load controlled by the stratum durum acts on the +.>On the layer, recalculate->And (3) continuously judging after the breaking distance of the hard rock layer, judging the rock layer by layer from top to bottom, and finally determining the positions of all key layers of the overlying strata of the stope.
S4.4, the contact surface between the key layer and the underlying rock stratum group is the position of delamination development, the overlying rock stratum group is changed according to the positions of all the key layers, and the 1~m rock layers are divided into the same rock layer group with the number of No.1 assuming that the (m+1) th rock layer is the key layer.
S4.5, determining the delamination development condition at the horizon by combining the advancing distance of the working face and the breaking angle of the overburden according to the rock stratum group divided in the step S4.4, and establishing a coal seam overburden delamination evolution model, such as a formula (5):
(5)；
in the method, in the process of the invention,is the development height of the separation layer,and (3) withFor the fracture angle of the formation,advancing a distance for the work surface;the distance of the working surface is advanced when the overlying strata separation layer grows to the limit value.
Further, the step S5 specifically includes the following steps:
s5.1, determining the positions of the layers and the position relation with the working surface of the layers which are sequentially developed under the condition of different advancing distances according to the coal seam overlying strata delamination evolution model.
S5.2, analyzing the spatial position relation between the delamination development horizon and the aquifer by combining the hydroengineering geological model of the coal seam roof.
S5.3, when the key layer is an aquifer and the lower rock layer is a water-resisting layer, the water supply source exists around the separation layer, and separation layer ponding can be formed under the condition that separation layer water is easy to collect and develop; when the upper part of the separation layer space is a water-resisting layer or the lower rock stratum is an aquifer, the separation layer space does not have a ponding condition, and separation layer ponding is not formed.
Further, the step S6 specifically includes the following steps:
s6.1, determining the first according to the simple girder force theoryThe maximum bending moment of the layer rock beam is positioned at the middle position of the beam, and when the length of the rock beam is l, the maximum bending momentThe method comprises the following steps:
(6)；
in the method, in the process of the invention,for the bending moment of the rock stratum, namely the maximum development space of the delamination layer,in order to be able to carry the load in an overlying manner,is the rock beam length.
S6.2, generalizing the separation layer space into a semi-ellipsoid with the short axis radius of the second layerThe maximum bending moment of the bed rock beam can obtain the volume of water accumulated in the bed space according to the volume of the semi-ellipsoidThe method comprises the following steps:
（7）；
in the method, in the process of the invention,and (3) withThe major axis and the minor axis of the ellipsoid respectively.
Flow to spatial sink according to Darcy's lawThe expression is:
（8）；
wherein,is the permeability coefficient.
Thus, the time for the body of water to fill the delamination space：
（9）。
S6.3 is a separation layer spaceFilling water when filling waterWhen the separation layer water body is communicated with the upper aquifer, the hydrostatic pressure is formedAccording to the water level mark of the aquiferElevation of space floor of separation layerAnd (3) determining:
（10）；
represents the density of water;representing the acceleration of gravity.
S6.4, when the separation layer water body is communicated with the upper confined aquifer, the load born by the lower bending aquifer in the stratum is represented byBecomes as followsThe breaking distance is changed from formula (4):
（11）；
in the method, in the process of the invention,the fracture length of the key bed rock Liang Jixian;is the firstThe formation thickness of the layer,tensile strength of the j-th layer of rock stratum;is loaded by the j layer;is hydrostatic pressure.
S6.5 whenWhen the breaking distance is smaller than the existing breaking distance, the hydrostatic pressure of the water body in the separation layer space can cause the breaking of the rock stratum of the lower water-resisting layer, so that the water-bearing layer enters the space, and the second-class water damage is caused.
When (when)When the water barrier is larger than the existing breaking distance, the water barrier between the separation layer and the underlying water guiding fracture zone cannot be broken, and second-class water damage cannot occur.
Further, the step S7 specifically includes the following steps:
s7.1, calculating a coal seam mining range corresponding to the breaking of the hard rock stratum according to the hydraulic engineering geological model of the coal seam roof and the rock breaking angle.
S7.2, when the hard rock stratum is broken, the broken part mainly comprises a compression fracture zone and a fracture zone, and specifically comprises the following two parts:
calculating energy released upon fracture of an upper formationEqual to the strain energy accumulated when the formation reaches a limit span:
（12）；
in the middle of，Load of unit length of additional load of the upper thick layer hard rock stratum and the overlying rock stratum of the separation layer, MN/m;elastic modulus of a thick layer of hard rock stratum is expressed in MPa;is the moment of inertia of the end face of a thick layer of hard rock,；is the thickness of the hard rock layer, and the unit is m;is the ultimate breaking distance of the hard rock formation.
When the shock wave propagates to the water-rock interface, the peak pressure attenuation is thatThe size of the material is as follows:
（13）；
in the method, in the process of the invention,in order to blast-hole radius the hole diameter,，is the radius of the equivalent explosive,；is an attenuation index;is energy, and the unit is MJ/m;is the detonation heat of the TNT explosive,。
when the tensile stress and exceeding the tensile strength of the rock occur in the rock, the fracture is considered to occur in the rock, so that the fracture zone range is compressedThis can be expressed as:
（14）；
in the method, in the process of the invention,representing the initial percussion pressure at the water-rock interface,representing the impact pressure developed at the location of the shock wave from the center of the explosion,in order to blast-hole radius the hole diameter,is the formation standoff.
Compression failure out-of-band stress wave peak pressure with propagation distanceAttenuation relation of (2)The method comprises the following steps:
（15）；
wherein lambda is the attenuation index of stress wave, and the calculation formula is，Is the poisson's ratio of the rock.
Tangential stress peaks according to poisson effectThe method comprises the following steps:
（16）；
for initial impact pressure propagation to the formation interface below the ionosphere water;is the propagation distance.
The tensile strength of the bed strata of the separation layer is brought into a formula (16) to replace the formula (16)Can obtain the fracture zone range：
（17）。
To propagate the initial impact pressure at the formation interface below the ionosphere water,is tensile strength.
Calculating the maximum range of the impact fracture zoneThe method comprises the following steps:
（18）；
judging the width of the coal mining range and the depth of the impact damage zone corresponding to the breaking of the hard rock stratum, and judging the water damage caused by the water movement of three types of high-order separation layers.
Calculating to obtain the impact fracture zone thickness, according to (11), the rock stratum thickness is calculated fromBecomes as followsCalculation using equation (19)Judging whether water damage caused by high-order separation layer water movement occurs according to the step S6.5;
（19）。
the invention has the following beneficial effects:
in the invention, firstly, judging a hard rock stratum based on a key layer theory, establishing a hydroengineering geological model, and searching the possible development position and size of a separation layer; then, calculating the water filling time and the water head pressure of the separation layer according to the development position and the size of the separation layer, judging the key water-resisting layer instability condition according to the breaking distance of the bottom water-resisting layer, and judging the hydrostatic pressure water damage of the high-order separation layer; and finally, analyzing the damage and fracture of the rock stratum below due to the energy release by considering the energy release caused by the fracture of the key layer, and further judging the water damage of the high-order separation layer. The invention starts from a separation layer water bursting mechanism, establishes a traditional roof water disaster, high-level separation layer hydrostatic pressure water disaster and dynamic water pressure water disaster multi-type water disaster identification model, provides a corresponding discrimination method and an evaluation flow, and has certain theoretical significance and application value.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art. In the drawings:
FIG. 1 shows a flow chart of a method of discriminating the type of water burst in a high-level ionosphere of a mining overburden in accordance with the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made apparent and fully in view of the accompanying drawings, in which some, but not all embodiments of the invention are shown. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The working surface of a western coal mine 2101 is the first mining working surface of the mining area. The working surface length of the mining 2101 is 2077m, the working surface width is 300m, the total coal thickness is 5.20-7.10 m, the average coal thickness is 6.32m, the coal seam dip angle is 0-7 degrees, and the average coal seam dip angle is 3 degrees. The coal-bearing stratum is dwarf Yanan group, an overlying dwarf Zhuang group, a diazepam group, a chalk-like volunteer group and a fourth line. In this embodiment, the determination of the water burst type of the high-level separation layer of the overlying strata is taken as an example.
The method for distinguishing the water burst type of the mining overburden high-level separation layer shown in fig. 1 specifically comprises the following steps:
s1, carrying out hydrogeological condition analysis and determining the spatial relationship between the water-bearing layer and the water-resisting layer of the roof of the coal seam.
S2, establishing a seam roof hydrologic engineering geological model, namely defining the horizon sequence of each layer, and obtaining seam roof hydrologic and engineering geological parameters.
S3, judging a type of water damage, namely the traditional roof fracture type water damage by utilizing a first judging method, namely utilizing the development height of the water guide fracture zone.
S4, based on the coal seam roof hydrologic engineering geological model and the key layer discrimination method, carrying out the combination division of the coal seam roof strata, and establishing a coal seam overlying strata separation layer evolution model.
S5, performing separation layer water formation analysis, further describing a dynamic process of separation layer development, and analyzing water filling conditions of separation layer space.
S6, calculating the first step according to the simple beam force theory and combined with Darcy lawBreaking distance->Comparison of->Breaking distance->And the relationship with the existing breaking distance is used for judging the second class of water damage, namely the hydrostatic pressure water damage of the high-order separation layer.
S7, calculating the maximum range of the impact fracture zoneAnd according toCalculate the firstBreaking distance of rock stratumComparison of the firstBreaking distance of rock stratumThree types of water damage, namely, the discrimination of the water damage of the high-order separation layer moving water, are carried out according to the relation with the existing breaking distance.
Specifically, in step S1, based on the hydrogeological conditions of the mine, the lithology and thickness of each stratum are analyzed, the spatial distribution and the burial depth of each water-bearing layer and each water-resisting layer are spatially spread, and the spatial position relationship between different water-bearing layers and different water-resisting layers is clarified.
Specifically, in step S2, based on hydrogeology and borehole data analysis, each stratum group is numbered 1 sequentially from bottom to top, 2....i.. I, defining lithology and thickness of each stratumWeight per unit>Osmotic coefficient->Tensile Strength->Elastic modulus->Namely, a coal seam overlying strata hydroengineering geological model is established, as shown in table 1:
table 1: hydrographic engineering geological model for coal seam overlying strata
。
Specifically, the step S3 specifically includes the following steps:
s3.1, determining the development height of the water-guiding fracture zone of the roof of the main coal mining layer by adopting a method of actual measurement, analogy or empirical formulaComparison ofAnd，representing the distance between the roof of the coal seam and each water-bearing rock formation, calculated using equation (1)：
(1)；
Wherein the method comprises the steps ofRepresenting the thickness of each formation between the roof of the coal seam and the floor of the aquifer.
S3.2 whenWhen the water-guiding fracture zone is in the water-bearing layer, the water-guiding fracture zone is advanced along with the working surface, the water-guiding fracture zone is developed to the water-bearing layer, groundwater is caused to flow into the working surface, and the traditional roof fracture type water damage, namely a type of water damage, is caused.
When (when)And when the water-bearing layer is not existed in the water-guiding crack zone, the water-bearing layer is not threatened by a class of water damage.
The measured fracture-recovery ratio of the research area is 21.0, and the calculated height of the water guide fracture zone is 126m. As can be seen from Table 1, the water-bearing layers are respectively arranged in the water-guiding fracture zones, the numbers are respectively 1,3,5 and 8, the distances from the coal seam roof are respectively 0m,34m,58m and 106m, which indicates that the groundwater in the rock layers can flow into the water-bearing fracture zone along with the advancing of the working face and the rising of the development height of the water-guiding fracture zone, and the water inflow of the working face is increased; the water in the water-bearing layer above the water-guiding fracture zone will not pass through the water-guiding fracture zone water-flushing working face, and cause class I water damage.
Specifically, step S4 specifically includes the following steps:
s4.1, when rock mechanical properties of adjacent boundary layers are different, the rigidity of the aviation horizon rock stratum is larger than that of the lower horizon rock stratum, and under the influence of self-weight stress, a separation layer space is formed at an interface between an upper rock stratum layer and a lower rock stratum layer, and the separation layer is generated under the condition that the rigidity and the deflection are required to be met at first:
(2)；
in the method, in the process of the invention,、/>for the rock rigidity of the upper and lower layers of the delamination interface, < +.>、/>Is the rock mass deflection of the upper and lower layers of the separation layer interface.
S4.2, assuming that a first horizon formation in the rock formations is a first key layer, the first horizon formation can control the range of overburden formations to reach a first levelLayer formation, then->The rock layers of the horizon are required to satisfy if the rock layers are key layers:
(3)；
in the method, in the process of the invention,，/>separate meterCalculate to->Layer and->The load of the first key layer in the layer process; />For the elastic modulus of the rock stratum>Is->Layer thickness->Is->Layer rock layer weight.
S4.3, the critical layer discrimination meets the requirement of the formula (3) and also meets the strength condition of the critical layer theory, namely, the breaking distance of the overlying hard rock layer is required to be larger than that of the underlying hard rock layer, and the overlying hard rock layer is provided with the following total componentsLayer hard rock formation:
(4)；
in the method, in the process of the invention,for a determined number of hard rock layers; />Is->Breaking distance of rock stratum; />For the thickness of the rock layer>For the tensile strength of the rock formation>Is the load born by the rock stratum.
If at firstThe hard rock layer does not satisfy the formula (4), the +.>The total stratum load controlled by the stratum durum acts on the +.>On the layer, recalculate->And continuing to judge after the breaking distance of the hard rock layer, judging the rock layer by layer from top to bottom, and finally determining the positions of all key layers of the overlying rock of the stope, as shown in table 2.
TABLE 2 determination of overburden key layer
。
S4.4, the contact surface between the key layer and the underlying rock stratum group is the position of delamination development, the overlying rock stratum group is changed according to the positions of all the key layers, and the 1~m rock layers are divided into the same rock layer group with the number of No.1 assuming that the (m+1) th rock layer is the key layer.
S4.5, determining the delamination development condition at the horizon by combining the advancing distance of the working face and the breaking angle of the overburden according to the rock stratum group divided in the step S4.4, and establishing a coal seam overburden delamination evolution model, such as a formula (5):
(5)；
in the method, in the process of the invention,is the development height of the separation layer,and (3) withFor the fracture angle of the formation,advancing a distance for the work surface;the distance of the working surface is advanced when the overlying strata separation layer grows to the limit value.
And (3) sequentially calculating loads according to a formula (3) in the step (4.2), judging hard rock layers in the overburden rock, and calculating the span load of each hard rock layer according to the formula (4), so as to judge 4 hard rock layers and 4 key layers in the development of the overburden rock. 4 layers of hard rock, including hard rock 4 being fine sandstone having a depth of burial of 375 m and a thickness of 23.87 m, hard rock 3 being medium sandstone having a depth of burial of 511.92 m and a thickness of 13.32 m, hard rock 2 being siltstone having a depth of burial of 540.37 m and a thickness of 12.67 m, and hard rock 1 being coarse sandstone having a depth of burial of 558.09 m and a thickness of 7.99 m. Among the 4 key layers, 1 main key layer and 3 sub-key layers are arranged, wherein fine sandstone with the depth of burial 196m being 49.89 m is used as the main key layer, fine sandstone with the depth of burial 326.6 m being 37.6 m is used as the sub-key layer 3, sandstone with the depth of burial 418 m being 20.81 m is used as the sub-key layer 2, and sandy mudstone with the depth of burial 458.3 m being 20.7m is used as the sub-key layer 1.
And judging the positions of 7 possible development separation layers by utilizing the key layer theoretical calculation result, wherein the positions are respectively near the burial depth 560m, near the burial depth 540m, near the burial depth 510m, near the burial depth 456m, near the burial depth 412m, near the burial depth 373m, near the burial depth 326m and near the burial depth 196 m.
Specifically, step S5 specifically includes the steps of:
s5.1, determining the positions of the layers and the position relation with the working surface of the layers which are sequentially developed under the condition of different advancing distances according to the coal seam overlying strata delamination evolution model.
S5.2, analyzing the spatial position relation between the delamination development horizon and the aquifer by combining the hydroengineering geological model of the coal seam roof.
S5.3, when the key layer is an aquifer and the lower rock layer is a water-resisting layer, the water supply source exists around the separation layer, and separation layer ponding can be formed under the condition that separation layer water is easy to collect and develop; when the upper part of the separation layer space is a water-resisting layer and the permeability coefficient is smaller, or the lower rock stratum is an aquifer, the separation layer space does not have a ponding condition, and separation layer ponding is not formed.
Combining the water accumulation condition of the separation layer: (1) there is a water-ionogenic space; (2) a replenishing water source exists around the separation layer; (3) the delamination space duration is sufficiently long; and (4) the permeability of the rock mass around the separation layer is strong. The lithology thickness below the buried depth of 460m is smaller, so that the separation layer development time is shorter, and according to lithology and position, the separation layer between the buried depths of 520 m-460 m mainly develops in the stable group of water-resisting layers, the lithology is mainly composed of mudstone and sandy mudstone, so that the permeability coefficient of the rock layer is smaller, or no water source is used for supplying, and the separation layer ponding is not easy to form. Therefore, the location of the formation of water accumulation in the delamination layer is mainly located in the aspiration group. And the three high-order delamination ponding near the burial depth 412m, the burial depth 373m and the burial depth 326m are the most dangerous.
Specifically, along with coal seam exploitation, the overlying strata separation layer gradually develops, the water layer is continuously supplied to the separation layer, the separation layer space is filled, the separation layer water head is raised to form certain hydrostatic pressure, at the moment, the separation layer water body exerts certain pore water pressure and load action on the lower strata group, cracks in the lower complete strata are promoted to expand, and finally, the water-resisting layer is invalid, so that hydrostatic water burst is generated.
The step S6 specifically comprises the following steps:
s6.1, determining the first according to the simple girder force theoryThe maximum bending moment of the layer rock beam is positioned at the middle position of the beam, and when the length of the rock beam is l, the maximum bending momentThe method comprises the following steps:
(6)；
in the method, in the process of the invention,for the bending moment of the rock stratum, namely the maximum development space of the delamination layer,in order to be able to carry the load in an overlying manner,is the rock beam length.
S6.2, generalizing the separation layer space into a semi-ellipsoid with the short axis radius of the second layerThe maximum bending moment of the bed rock beam can obtain the volume of water accumulated in the bed space according to the volume of the semi-ellipsoidThe method comprises the following steps:
（7）；
in the method, in the process of the invention,and (3) withThe major axis and the minor axis of the ellipsoid respectively.
TABLE 3 calculation of the separation layer space correlation parameters
。
Flow to spatial sink according to Darcy's lawThe expression is:
（8）；
wherein,is the permeability coefficient.
Thus, the time for the body of water to fill the delamination space：
（9）。
S6.3, filling water for the separation layer space, and when the water is filledWhen the separation layer water body is communicated with the upper aquifer, the hydrostatic pressure is formedAccording to the water level mark of the aquiferElevation of space floor of separation layerAnd (3) determining:
（10）；
represents the density of water;representing the acceleration of gravity.
S6.4, takingThe maximum water level elevation +1270 m of the water level long-term observation hole of the water-bearing layer of the well Tian Zhidan group is taken as a reference, and calculated 2101 working surface burial depths 326m,373m and 412m are respectively: 2.23MPa, 3.50MPa and 4.02MPa. The hydrostatic pressure in the separation layer space mainly acts on the water-resisting layer between the separation layer and the top of the underlying water-guiding fracture zone, and when the water-resisting rock stratum cannot resist the pressure of the separation layer water, water burst disasters are caused. When the separation layer water body is communicated with the upper confined aquifer, the load born by the lower bending aquifer is calculated byBecomes as followsThe breaking distance is changed from formula (4):
（11）；
in the method, in the process of the invention,the fracture length of the key bed rock Liang Jixian;is the firstThe formation thickness of the layer,tensile strength of the j-th layer of rock stratum;is loaded by the j layer;is hydrostatic pressure.
Calculated, the water-resisting layer below each delamination layerCan not be generated when the breaking distance is still larger than the existing breaking distanceGenerating water hazard of the second kind.
S6.5 whenWhen the breaking distance is smaller than the existing breaking distance, the hydrostatic pressure of the water body in the separation layer space can cause the breaking of the rock stratum of the lower water-resisting layer, so that the water-bearing layer enters the space, and the second-class water damage is caused.
When (when)When the water barrier is larger than the existing breaking distance, the water barrier between the separation layer and the underlying water guiding fracture zone cannot be broken, and second-class water damage cannot occur.
Specifically, the step S7 specifically includes the following steps:
s7.1, calculating a coal seam mining range corresponding to the breaking of the hard rock stratum according to the hydraulic engineering geological model of the coal seam roof and the rock breaking angle.
S7.2, when the hard rock stratum is broken, the broken part mainly comprises a compression fracture zone and a fracture zone, and specifically comprises the following two parts:
calculating energy released upon fracture of an upper formationEqual to the strain energy accumulated when the formation reaches a limit span:
（12）；
in the method, in the process of the invention,load of unit length of additional load of the upper thick layer hard rock stratum and the overlying rock stratum of the separation layer, MN/m;elastic modulus of a thick layer of hard rock stratum is expressed in MPa;is the moment of inertia of the end face of a thick layer of hard rock,；is the thickness of the hard rock layer, and the unit is m;is the ultimate breaking distance of the hard rock formation.
When the shock wave propagates to the water-rock interface, the peak pressure attenuation is thatThe size of the material is as follows:
（13）；
in the method, in the process of the invention,in order to blast-hole radius the hole diameter,，is the radius of the equivalent explosive,；is an attenuation index;is energy, and the unit is MJ/m;is the detonation heat of the TNT explosive,。
when the tensile stress occurs in the rock and exceeds the tensile strength thereofIt is believed that tension cracks will occur in the rock to fail and thus compress the zone of failureThis can be expressed as:
（14）；
in the method, in the process of the invention,representing the initial percussion pressure at the water-rock interface,representing the impact pressure developed at the location of the shock wave from the center of the explosion,in order to blast-hole radius the hole diameter,is the formation standoff.
Compression failure out-of-band stress wave peak pressure with propagation distanceAttenuation relation of (2)The method comprises the following steps:
（15）；
wherein lambda is the attenuation index of stress wave, and the calculation formula is，Is the poisson's ratio of the rock.
Tangential stress peaks according to poisson effectThe method comprises the following steps:
（16）；
for initial impact pressure propagation to the formation interface below the ionosphere water;is the propagation distance.
The tensile strength of the bed strata of the separation layer is brought into a formula (16) to replace the formula (16)Can obtain the fracture zone range：
（17）。
To propagate the initial impact pressure at the formation interface below the ionosphere water,is tensile strength.
Calculating the maximum range of the impact fracture zoneThe method comprises the following steps:
（18）；
judging the width of the coal mining range and the depth of the impact damage zone corresponding to the breaking of the hard rock stratum, and judging the water damage caused by the water movement of three types of high-order separation layers.
Calculating to obtain the impact fracture zone thickness, according to (11), the rock stratum thickness is calculated fromBecomes as followsCalculation using equation (19)Judging whether water damage caused by high-order separation layer water movement occurs according to the step S6.5;
（19）。
namely: when (when)When the distance is smaller than the existing breaking distance, the water in the separation layer space under the action of power can cause the breaking of the rock stratum of the lower water-resisting layer, so that the water-bearing layer enters the space to cause the water damage of the high-level separation layer moving water; when l j When being greater than current breaking distance, then the water barrier between separation layer and the water guiding crack area of following can not break, then can not take place high-order separation layer and move water damage.
Along with coal seam stoping, the separation layer space gradually increases and reaches a relatively stable state; in the process, the hard rock stratum with better delamination integrity can generate accumulated elastic strain energy, when the elastic energy is accumulated to a certain extent, the hard rock stratum can not resist the weight of the hard rock stratum and the overlying rock stratum to generate dynamic instability fracture, the accumulated huge strain energy is released instantaneously, and the closed delamination water is slapped to generate ultrahigh water pressure; and finally, the energy acts on the bed-separation floor rock stratum in a form of impact load to cause instantaneous fracture, and if the fracture zone is directly communicated with the stope roof water guide fracture zone, the high-level bed-separation hydrodynamic water bursting disaster is initiated.
The surface overlying strata fracture angle theta of the well field 2101 is 69 degrees, corresponding parameters of the main key layer, the sub key layer 3, the sub key layer 2 and the sub key layer 1 in the table 2 are substituted into formulas (12) to (18), and the depth of an impact bottom plate fracture zone caused by fracture of each key layer is calculated to be 17.32m, 144.01m, 189.36m and 6.67m respectively. The thicknesses of the remaining water-resistant layers are 411.13m,153.84m,17.09m and 159.48m (see Table 4) respectively, so that the probability of hydrodynamic water burst of the high-order separation layer is small.
Table 4: high-level separation layer hydrodynamic force protrusion analysis meter for coal mine
。
In addition, the widths of the coal seam exploitation ranges corresponding to the limit breaking distances of the sub-critical layer 1 and the sub-critical layer 2 are 173 m and 153 m in sequence. Because the inclined length of the working face of the well field is 300m, when the working face of 2101 is mined, the sub-critical layer 1 and the sub-critical layer 2 are broken, but the power water bursting disaster is not caused, and the feasibility of predicting the present score providing method is verified.
It should be understood that the above description is not intended to limit the invention to the particular embodiments disclosed, but to limit the invention to the particular embodiments disclosed, and that the invention is not limited to the particular embodiments disclosed, but is intended to cover modifications, adaptations, additions and alternatives falling within the spirit and scope of the invention.
Claims (7)
1. The method for distinguishing the water burst type of the mining overburden high-level separation layer is characterized by comprising the following steps of:
s1, carrying out hydrogeological condition analysis and determining the spatial relationship between a water-bearing layer and a water-resisting layer of a roof of a coal seam;
s2, establishing a seam roof hydrologic engineering geological model, namely defining the horizon sequence of each layer, and acquiring seam roof hydrologic and engineering geological parameters;
s3, judging a type of water damage, namely the traditional roof fracture type water damage by utilizing the development height of the water guide fracture zone;
s4, based on the coal seam roof hydrologic engineering geological model and the key layer discrimination method, carrying out the combination division of the coal seam roof strata, and establishing a coal seam overlying strata separation layer evolution model;
s5, performing separation layer water formation analysis, describing a dynamic process of separation layer development, and analyzing water filling conditions of separation layer space;
s6, calculating the first step according to the simple beam force theory and combined with Darcy lawBreaking distance->Comparison of->Breaking distance->The relationship with the existing breaking distance is used for judging the second class of water damage, namely the hydrostatic pressure water damage of the high-order separation layer;
s7, calculating the maximum range of the impact fracture zoneAnd according to->Calculate->Breaking distance->Comparison of->Breaking distance->Three types of water damage, namely, the discrimination of the water damage of the high-order separation layer moving water, are carried out according to the relation with the existing breaking distance.
2. The method according to claim 1, wherein in step S2, based on hydrogeology, drilling data analysis, each rock stratum group is numbered 1 from bottom to top in proper order, 2Weight per unit>Osmotic coefficient->Tensile Strength->Elastic modulus->And (5) determining the layer sequence, and obtaining the hydrological parameters and engineering geological parameters of the coal seam roof.
3. The method for distinguishing the water burst type of the high-level separation layer of the mining overburden according to claim 1, wherein the step S3 specifically includes the following steps:
s3.1, determining the development height of the water-guiding fracture zone of the roof of the main coal mining layer by adopting a method of actual measurement, analogy or empirical formulaComparison->And->，/>Representing the roof of the coal seam and the various water bearing strataThe distance between them is calculated by using formula (1)>：
(1)；
Wherein the method comprises the steps ofRepresenting the thickness of each rock stratum between the coal seam roof and the aquifer floor;
s3.2 whenWhen the water-guiding fracture zone is in the water-bearing layer, the water-guiding fracture zone is advanced along with the working surface, the water-guiding fracture zone is developed to the water-bearing layer, groundwater is caused to flow into the working surface, and the traditional roof fracture type water damage, namely a type of water damage, is caused;
when (when)And when the water-bearing layer is not existed in the water-guiding crack zone, the water-bearing layer is not threatened by a class of water damage.
4. The method for distinguishing the water burst type of the high-level separation layer of the mining overburden according to claim 1, wherein the step S4 specifically includes the following steps:
s4.1, the generation of the separation layer firstly needs to meet the following rigidity and deflection conditions:
(2)；
in the method, in the process of the invention,、/>for the rock rigidity of the upper and lower layers of the delamination interface, < +.>、/>Rock mass deflection of upper and lower layers of a separation layer interface;
s4.2, assuming that a first horizon formation in the rock formations is a first key layer, the first horizon formation can control the range of overburden formations to reach a first levelLayer formation, then->The rock layers of the horizon are required to satisfy if the rock layers are key layers:
(3)；
in the method, in the process of the invention,，/>calculated to be->Layer and->The load of the first key layer in the layer process; />For the elastic modulus of the rock stratum>Is->Layer thickness->Is->The layer weight of the layer rock;
s4.3, the critical layer discrimination meets the requirement of the formula (3) and also meets the strength condition of the critical layer theory, namely, the breaking distance of the overlying hard rock layer is required to be larger than that of the underlying hard rock layer, and the overlying hard rock layer is provided with the following total componentsLayer hard rock formation:
(4)；
in the method, in the process of the invention,for a determined number of hard rock layers; />Is->Breaking distance of rock stratum; />For the thickness of the rock layer>For the tensile strength of the rock formation>Load bearing for the formation;
if at firstThe hard rock layer does not satisfy the formula (4), the +.>The total stratum load controlled by the stratum durum acts on the +.>On the layer, recalculate->Continuing to judge after the breaking distance of the hard rock layer, judging the rock layer by layer from top to bottom, and finally determining the positions of all key layers of the overlying strata of the stope;
s4.4, the contact surface between the key layer and the underlying rock stratum group is the position of delamination development, the overlying rock stratum group is changed according to the positions of all the key layers, and the 1~m rock layers are divided into the same rock layer group with the number of No.1 assuming that the (m+1) th rock layer is the key layer;
s4.5, determining the delamination development condition at the horizon by combining the advancing distance of the working face and the breaking angle of the overburden according to the rock stratum group divided in the step S4.4, and establishing a coal seam overburden delamination evolution model, such as a formula (5):
(5)；
in the method, in the process of the invention,is the development level of the abscission layer, the%>And->For the fracture angle of the rock formation>Advancing a distance for the work surface; />The distance of the working surface is advanced when the overlying strata separation layer grows to the limit value.
5. The method for distinguishing the water burst type of the high-level separation layer of the mining overburden according to claim 1, wherein the step S5 specifically includes the following steps:
s5.1, determining the positions of layers and the position relation with a working surface of the layers which are sequentially developed under the condition of different advancing distances according to a coal seam overlying strata delamination evolution model;
s5.2, analyzing the spatial position relation between the delamination development horizon and the aquifer by combining the hydroengineering geological model of the coal seam roof;
s5.3, when the key layer is an aquifer and the lower rock layer is a water-resisting layer, the water supply source exists around the separation layer, and separation layer ponding can be formed under the condition that separation layer water is easy to collect and develop; when the upper part of the separation layer space is a water-resisting layer or the lower rock stratum is an aquifer, the separation layer space does not have a ponding condition, and separation layer ponding is not formed.
6. The method for distinguishing the water burst type of the high-level separation layer of the mining overburden according to claim 1, wherein the step S6 specifically includes the following steps:
s6.1, determining the first according to the simple girder force theoryThe maximum bending moment of the layer rock beam is positioned at the middle position of the beam, when the length of the rock beam is l, the maximum bending moment is +.>The method comprises the following steps:
(6)；
in the method, in the process of the invention,for the bending moment of the rock stratum, i.e. the maximum development space of the delamination +.>For upper load->Is the rock beam length;
s6.2, generalizing the separation layer space into a semi-ellipsoid with the short axis radius of the second layerThe maximum bending moment of the bed rock beam can obtain the water accumulation volume of the bed space according to the semi-ellipsoidal volume>The method comprises the following steps:
（7）；
in the method, in the process of the invention,and->The major axis and the minor axis of the ellipsoid are respectively;
flow to spatial sink according to Darcy's lawThe expression is:
（8）；
wherein,is the permeability coefficient;
thus, the time for the body of water to fill the delamination space：
（9）；
S6.3, filling water for the separation layer space, and when the water is filledWhen in use, the separation layer water body is communicated with the upper water-bearing layer to form hydrostatic pressure +.>According to the water level mark of the aquifer->And the elevation of the separation layer space bottom plate->And (3) determining:
（10）；
represents the density of water; />Representing gravitational acceleration;
s6.4, when the separation layer water body is communicated with the upper confined aquifer, the load born by the lower bending aquifer in the stratum is represented byBecome->The breaking distance is changed from formula (4):
（11）；
in the method, in the process of the invention,the fracture length of the key bed rock Liang Jixian; />Is->Layer formation thickness>Tensile strength of the j-th layer of rock stratum; />Is loaded by the j layer; />Is hydrostatic pressure;
s6.5 whenWhen the breaking distance is smaller than the existing breaking distance, the hydrostatic pressure of the water body in the separation layer space can cause the breaking of the rock stratum of the lower water-resisting layer, so that the water-bearing layer enters the space to cause second-class water damage;
when (when)When the distance is larger than the existing breaking distance, the separation layer and the underlying layerThe water-resisting layer between the water-guiding crack strips can not be broken, and the second kind of water damage can not occur.
7. The method for distinguishing the water burst type of the high-level separation layer of the mining overburden according to claim 1, wherein the step S7 specifically includes the following steps:
s7.1, calculating a coal seam mining range corresponding to the breaking of the hard rock stratum according to the hydraulic engineering geological model of the coal seam roof and the rock breaking angle;
s7.2, when the hard rock stratum is broken, the broken part mainly comprises a compression fracture zone and a fracture zone, and specifically comprises the following two parts:
calculating energy released upon fracture of an upper formationEqual to the strain energy accumulated when the formation reaches a limit span:
（12）；
in the method, in the process of the invention,load of unit length of additional load of the upper thick layer hard rock stratum and the overlying rock stratum of the separation layer, MN/m; />Elastic modulus of a thick layer of hard rock stratum is expressed in MPa; />End moment of inertia for thick layers of hard rock formations +.>；/>For the thickness of hard rock formations, singlyThe bit is m; />A limit fracture distance for a hard formation;
when the shock wave propagates to the water-rock interface, the peak pressure attenuation is thatThe size of the material is as follows:
（13）；
in the method, in the process of the invention,for the blast hole radius>，/>Is equivalent to the radius of explosive>；/>Is an attenuation index;is energy, and the unit is MJ/m; />Is the explosion heat of TNT explosive +.>；
When the tensile stress and the tensile strength are exceeded in the rock, the tensile fracture is considered to be damaged and failedThus compressing the fracture zone rangeThis can be expressed as:
（14）；
in the method, in the process of the invention,representing the initial percussion pressure at the water-rock interface, < >>Representing the impact pressure developed at the location of the shock wave from the centre of the explosion,/->For the blast hole radius>A suspension distance for the rock formation;
compression failure out-of-band stress wave peak pressure with propagation distanceAttenuation relation of->The method comprises the following steps:
（15）；
wherein lambda is the attenuation index of stress wave, and the calculation formula is，/>Poisson's ratio for rock;
tangential stress peaks according to poisson effectThe method comprises the following steps:
（16）；
for initial impact pressure propagation to the formation interface below the ionosphere water; />Is the propagation distance;
the tensile strength of the bed strata of the separation layer is brought into a formula (16) to replace the formula (16)The range of fracture zone can be obtained>：
（17）；
For propagation to the initial impact pressure at the formation interface below the ionosphere water, +.>Is tensile strength;
calculating the maximum range of the impact fracture zoneThe method comprises the following steps:
（18）；
judging the width of the coal mining range and the depth of the impact damage zone corresponding to the breaking of the hard rock stratum, and judging the water damage caused by the water movement of three types of high-order separation layers;
calculating to obtain the impact fracture zone thickness, according to (11), the rock stratum thickness is calculated fromBecome->Calculation using equation (19)Judging whether water damage caused by high-order separation layer water movement occurs according to the step S6.5;
（19）。
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| 张文忠;: "离层水突水模式与离层破断距", 湖南科技大学学报(自然科学版), no. 02, pages 20 - 23 * |
| 曹海东，靳德武著: "《煤层开采覆岩离层水体致灾机理与防控技术研究》", 北京：地质出版社, pages: 100 - 120 * |
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