阅读说明：本技术 一种复合煤层端帮开采煤柱参数设计方法 (Method for designing parameters of pillar mining at end slope of composite coal seam ) 是由 曹兰柱 周晶 丁春健 姜聚宇 于 2021-09-18 设计创作，主要内容包括：本发明公开了一种复合煤层端帮开采煤柱参数设计方法,步骤为：计算上层煤柱不同采宽下所受荷载、煤柱强度及安全系数,根据安全系数确定合理上层煤柱留设宽度；分析上层煤柱的竖向附加应力,得出所受荷载大小,判断下层煤柱开采可行性；应用FLAC3D对不同宽度的支撑煤柱进行数值模拟,确定下层煤柱合理支撑煤柱的宽度。本发明基于复合煤层的力学性质,分析上层煤柱应力向下传递规律及分布特征,结合数值模拟手段,提出一种新的复合煤层端帮开采支撑煤柱参数设计方法,为提高煤炭资源利用率、确保端帮开采安全生产提供科学手段。(The invention discloses a method for designing parameters of a composite coal seam end slope mining coal pillar, which comprises the following steps: calculating the load borne by the upper coal pillar under different mining widths, the strength of the upper coal pillar and a safety coefficient, and determining a reasonable reserved width of the upper coal pillar according to the safety coefficient; analyzing the vertical additional stress of the upper coal pillar to obtain the size of the load, and judging the exploitation feasibility of the lower coal pillar; and (4) carrying out numerical simulation on the support coal pillars with different widths by using FLAC3D to determine the width of the reasonable support coal pillars of the lower coal pillars. The invention provides a novel design method for parameters of an end slope mining supporting coal pillar of a composite coal seam by analyzing the downward transmission rule and distribution characteristics of the stress of the upper coal pillar based on the mechanical properties of the composite coal seam and combining a numerical simulation means, and provides a scientific means for improving the utilization rate of coal resources and ensuring the safe production of the end slope mining.)

1. A parameter design method for mining coal pillars at the end slope of a composite coal seam is characterized by comprising the following steps:

s1: calculating the load borne by the upper coal pillar under different mining widths, the strength of the upper coal pillar and a safety coefficient, and determining a reasonable reserved width of the upper coal pillar according to the safety coefficient;

s2: analyzing the vertical additional stress of the upper coal pillar to obtain the size of the load, and judging the exploitation feasibility of the lower coal pillar;

s3: and (4) carrying out numerical simulation on the support coal pillars with different widths by using FLAC3D to determine the width of the reasonable support coal pillars of the lower coal pillars.

2. The method for designing parameters of an end slope mining pillar of a composite coal seam as claimed in claim 1, wherein in step S1, the load applied to the upper pillar is:

wherein, P₀The load borne by the upper coal seam, and H is the buried depth; gamma is the average volume weight of the overburden; a is the width of the coal pillar; and b is the drift width.

3. The method for designing parameters of an end slope mining pillar of a composite coal seam as claimed in claim 2, wherein in step S1, the pillar strength is:

wherein σ_zlIs the intensity of the coal pillar, σ_cIs the strength of a cubic coal sample of 25mm, h is the height of a coal pillar, W_eEquivalent coal pillar width.

4. The method for designing parameters of an end slope mining pillar of a composite coal seam as claimed in claim 3, wherein in step S2, the vertical additional stress of the upper pillar is:

wherein σ_zThe vertical additional stress of the upper coal pillar is adopted, and Z is the distance value between the upper coal pillar and the lower coal pillar.

Technical Field

The invention belongs to the technical field of surface mining, and particularly relates to a parameter design method for mining a coal pillar at the end slope of a composite coal seam.

Background

Most of open-pit mines in China are multi-coal-bed coal fields, such as rubusstrip mines, Yimin open-pit mines, hollyn river open-pit mines and the like, and after large open-pit mines are mined, the problem that end slope pressing coal is difficult to recover is often faced. The end slope retained coal not only causes serious resource waste, but also can cause spontaneous combustion to generate the problems of environmental pollution and potential safety hazard, so that the problem of end slope coal pressing is increasingly prominent.

In the process of carrying out stoping on the coal seam pressed and covered under the end wall by adopting an end wall mining process, the reserved parameters of the support coal pillars are the key of the stoping operation, and once the support coal pillars are damaged in a destabilizing way, the domino effect can be caused to cause the instability of the side slope, so that the losses of casualties, mechanical pressing and the like are caused. The researchers of the open pit coal mine carry out active research and exploration on the parameter design problem of the end slope pressing coal extraction supporting coal pillar, and the existing coal seam mining supporting coal pillar size design theory is based on the underground mining experience and aims at single coal seam mining, so that the stress transfer mechanism between coal seam mining layers of the open pit mine cannot be well explained.

Therefore, an end slope mining coal pillar parameter design method is urgently needed to overcome the defects in the design and stability research aspect of the composite coal seam supporting coal pillars.

Disclosure of Invention

Based on the defects of the prior art, the technical problem to be solved by the invention is to provide a method for designing parameters of an end slope mining coal pillar of a composite coal seam, which is used for analyzing the downward transfer rule and distribution characteristics of the stress of the upper coal pillar, and combining a numerical simulation means, improving the utilization rate of coal resources and ensuring the safe production of end slope mining.

In order to solve the technical problems, the invention is realized by the following technical scheme:

the invention provides a method for designing parameters of a composite coal seam end slope mining coal pillar, which comprises the following steps:

s1: calculating the load borne by the upper coal pillar under different mining widths, the strength of the upper coal pillar and a safety coefficient, and determining a reasonable reserved width of the upper coal pillar according to the safety coefficient;

s2: analyzing the vertical additional stress of the upper coal pillar to obtain the size of the load, and judging the exploitation feasibility of the lower coal pillar;

s3: and (4) carrying out numerical simulation on the support coal pillars with different widths by using FLAC3D to determine the width of the reasonable support coal pillars of the lower coal pillars.

Further, in step S1, the load applied to the upper coal pillar is:

wherein, P₀The load borne by the upper coal seam, and H is the buried depth; gamma is the average volume weight of the overburden; a is the width of the coal pillar; and b is the drift width.

Further, in step S1, the pillar strength is:

wherein σ_zlIs the intensity of the coal pillar, σ_cIs the strength of a cubic coal sample of 25mm, h is the height of a coal pillar, W_eEquivalent coal pillar width.

Further, in step S2, the vertical additional stress of the upper coal pillar is:

wherein σ_zThe vertical additional stress of the upper coal pillar is adopted, and Z is the distance value between the upper coal pillar and the lower coal pillar.

In the invention, based on the Bossinesq supporting coal pillar stress model, the magnitude of the additional stress and the transmission rule of the upper coal pillar of the composite coal seam mined at the end slope of the strip mine are obtained, the FLAC3D is used for carrying out numerical simulation on the supporting coal pillar, and the method for designing the reasonable size of the supporting coal pillar of the lower coal seam under the condition of meeting the stability of the coal pillar is provided. Based on the mechanical properties of the composite coal seam, the downward transfer rule and the distribution characteristics of the upper coal pillar stress are analyzed, and a numerical simulation means is combined, so that a novel design method for the parameters of the support coal pillar for the end slope mining of the composite coal seam is provided, and a scientific means is provided for improving the utilization rate of coal resources and ensuring the safe production of the end slope mining.

The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical means of the present invention more clearly understood, the present invention may be implemented in accordance with the content of the description, and in order to make the above and other objects, features, and advantages of the present invention more clearly understood, the following detailed description is given in conjunction with the preferred embodiments, together with the accompanying drawings.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings of the embodiments will be briefly described below.

FIG. 1 is a flow chart of a composite coal seam end slope mining pillar parameter design method of the present invention;

FIG. 2 is a schematic view of supporting a coal pillar load;

FIG. 3 is a numerical simulation of a lower coal pillar of different widths using FLAC3D (a) for a lower coal pillar having a mining width of 6.5 m; (b) the mining width of the lower coal pillar is 7.0 m; (c) the width of the lower coal pillar is 7.5 m.

Detailed Description

Other aspects, features and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, which form a part of this specification, and which illustrate, by way of example, the principles of the invention. In the referenced drawings, the same or similar components in different drawings are denoted by the same reference numerals.

Different from single coal seam mining, after the upper coal seam is mined, due to the influence of the original rock stress and mining, the supporting pressure of the coal pillar is transmitted to the bottom plate, and the stress distribution form of the bottom plate rock stratum is finally formed after stress concentration and transmission on the bottom plate. When the distance between the upper coal layer and the lower coal layer is small to a certain degree, the mutual influence between the coal layers is very obvious, and the mechanical mechanism is more complex.

As shown in fig. 1 to 3, the method for designing parameters of an end slope mining pillar of a composite coal seam of the invention comprises the following steps:

the first step is as follows: calculating the load P0 borne by the upper coal pillar under different mining widths, the coal pillar strength sigma zl and a safety coefficient, and determining the reasonable upper coal pillar reserved width according to the safety coefficient;

the second step is that: analyzing the vertical additional stress of the upper coal pillar to obtain the size of the load, and judging the exploitation feasibility of the lower coal pillar;

the third step: and (4) carrying out numerical simulation on the support coal pillars with different widths by using FLAC3D to determine the width of the reasonable support coal pillars of the lower coal pillars.

In the present invention, the upper coal seam is analyzed for stress and additional stress transmitted downward. The method comprises the steps of firstly calculating the overlying load (shown in figure 2) and the strength of an upper coal pillar, determining the reasonable width of the upper coal pillar, analyzing and calculating the additional stress of any point M (X, Y, Z) below the upper coal pillar by using Boussinesq theory of elasticity mechanics, wherein the load borne by a lower coal pillar is the sum of the original rock stress above the top plate of the coal pillar and the additional stress of the upper coal pillar, and when the strength of the coal pillar is enough to support the overlying load, performing numerical simulation on the double-layer coal pillar to determine the size of the lower coal pillar. In the end slope mining engineering, the mining depth length of the coal pillars on the slope inclination is far larger than the reserved width, so that plane strain analysis is carried out on the supporting coal pillars, the vertical additional stress of the supporting coal pillars is superposed, and the stress transfer size and depth of the load of the upper coal pillar to the bottom plate rock stratum are obtained. The invention sequentially determines the reserved widths of the upper and lower coal seam support coal pillars in a downward mining mode, thereby ensuring safe recovery.

The load borne by the upper coal pillar is as follows:

the coal pillar strength is:

the number of the reserved supporting coal pillars is n when the end slope is set, and the vertical additional stress of a plurality of concentrated loads is as follows:

the method comprises the steps of bringing the distance value between an upper layer of coal and a lower layer of coal into an upper formula z to obtain the load borne by a lower layer of coal pillar, calculating the strength of the coal pillar, obtaining the maximum vertical uniform load in the inclination direction of the supporting coal pillar at the deepest part of the supporting coal pillar when the strength of the coal pillar is greater than the vertical load transmitted by an upper coal seam, carrying out lower coal seam mining on the coal pillar, obtaining the maximum vertical uniform load in the inclination direction of the supporting coal pillar, carrying out numerical simulation on the deepest engineering position section, analyzing the distribution characteristics of plastic zones, wherein the instability damage modes of the supporting coal pillar under different widths are shearing damage, gradually reducing the plastic zone ranges at two sides of the coal pillar along with the increase of the width of the coal pillar, obtaining the width of the coal pillar under the state as a design coal pillar width parameter when a certain proportion of an elastic core zone exists in the middle position of the coal pillar, wherein the plastic zones are not communicated, and the coal pillar is in a stable state.

In the formula (I), the compound is shown in the specification,

P₀upper coal layer upper load (kN/m)²)；

Gamma-overburden average volume weight (kN/m)³)；

a, the width of the coal pillar;

b-the width of the chamber;

σ_zl-pillar strength, (MPa);

σ_c-strength of 25mm cubic coal samples, (MPa);

h-pillar height, (m);

W_eequivalent pillar width, W_e＝2a，(m)；

H — depth of burial, (m);

σ_z-additional positive stress (MPa) in the vertical direction;

r_idistance of point M (X, Y, Z) from the concentrated load in the XOY plane.

Examples

The main lithology of each stratum from bottom to top in a certain opencast mine area is bedrock, a mudstone interbed, 9 coal, a mudstone interbed, 4 coal, fine sandstone and surface soil, the No. 4 coal seam and the No. 9 coal seam are mainly mined, and the distance between the coal seams is about 36 m. The thickness of 4 coals and 9 coals in the south side is larger, the coal bed is nearly horizontal, the occurrence is stable, and simultaneously, because the side wall is large in covering resource amount, the side wall is suitable for adopting the side wall detained coal mining process. The mining width of the mining equipment is 3.3m, the mining height is 4m, and the designed mining depth is 150 m. The formation base parameters are shown in table 1.

TABLE 1 coal and rock formation mechanical parameters

Composite coal seam support pillar parameter determination

(1) And calculating the safety factors of different coal pillar widths of the upper coal seam, wherein the safety factor of the supporting coal pillar is required to be more than 1.3 according to the actual mining condition and geological condition of end slope mining, and the width of the upper coal pillar is determined to be 5.5 m.

TABLE 2 empirical formula calculation

The vertical load of the upper coal pillar is calculated by applying a concentrated load superposition formula of a Boussinesq solution theory, and the load borne by the lower coal pillar is determined to be

And calculating results show that the lower-layer mining is feasible, numerical simulation is carried out on the lower-layer coal pillars with different widths by adopting FLAC3D, and the reasonable width of the lower-layer coal pillars is determined to be 7.0m through plastic zone distribution.

While the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.