CN-121803291-B - Key parameter design method for water retention and coal mining of targeted grouting filling pier column

CN121803291BCN 121803291 BCN121803291 BCN 121803291BCN-121803291-B

Abstract

The invention belongs to the technical field of coal mining, and particularly relates to a key parameter design method for water retention and coal mining of a targeted grouting filling pier column. The method comprises the steps of collecting mine hydrogeology and mining geology data, obtaining burial depth, thickness, physical mechanical parameters and gangue breaking expansion coefficients of a coal stratum, adopting discrete element numerical simulation to determine the height of a collapse zone under the critical advancing length of insufficient mining, calculating the drilling depth of grouting drilling holes and the void ratio of the collapse zone, preparing and testing the mechanical strength and the diffusion stacking angle of grouting materials in a laboratory, combining the critical coefficient of insufficient mining, adopting a stratum subsidence probability integration method, scientifically designing the spacing, radius and grouting quantity of filling pier columns, finally forming cementing pier columns on the collapse zone through ground drilling grouting, stably supporting an overlying stratum, and controlling the structural deformation of an aquifer. The method has the advantages of simple parameter design and high accuracy, and avoids space-time interference of the traditional filling process.

Inventors

SUN QIANG
ZHAO RUI
ZHANG JIXIONG
ZHANG JIAQI
MA DAN
MENG GUOHAO
NIE HONGZHEN
CHENG XIAOMING

Assignees

中国矿业大学

Dates

Publication Date: 20260508
Application Date: 20260305

Claims (8)

1. The key parameter design method for water retention and coal mining of the targeted grouting filling pier column is characterized by comprising the following steps of: Step 1, collecting mine hydrogeology and mining geology data, and acquiring burial depth H 1 , thickness M, physical and mechanical parameters, working surface size and crushing expansion coefficient K p of a goaf caving belt gangue of a coal stratum, wherein the physical and mechanical parameters in the step 1 comprise at least one of density, compressive strength, elastic modulus and Poisson's ratio of the coal stratum, the working surface size comprises working surface trend length and trend length, and the crushing expansion coefficient K p is acquired through field actual measurement or laboratory compaction test; Step 2, based on the data obtained in the step 1, establishing a goaf caving zone model through discrete element numerical simulation software, simulating the rock stratum caving behavior of a working surface under the condition of insufficient mining critical propulsion length, and determining the caving zone height H d of the working surface under the condition of the insufficient mining critical propulsion length L t , wherein the insufficient mining critical propulsion length L t is dynamically determined through simulating the rock stratum caving process so as to represent the critical state when the working surface is propelled to the rock stratum caving stability; Step 3, calculating the drilling depth H ks, of the grouting drilling holes according to the height H d of the caving belt, wherein H ks is used for ensuring that the drilling holes penetrate through the caving belt and leave a safety margin; step 4, calculating the void ratio of the caving belt based on the crushing expansion coefficient K p of the caving belt in the goaf The void fraction Characterizing the void ratio in the collapse zone that can be filled by grouting; Step 5, preparing grouting materials with different mechanical strength and flow characteristics, and testing the mechanical strength F and slurry diffusion stacking angle of the grouting materials in a laboratory Selecting grouting materials meeting the supporting requirement according to the test result; Step6, according to the insufficient mining critical coefficient Determining a filling pier column interval D, wherein the interval D is used for ensuring that the pier columns are spaced to support an overlying strata and controlling the strata to sink; step 7, calculating a maximum subsidence value W of a target protection aquifer under the condition of different filling pier bottom surface radiuses R by using a probability integration method of stratum subsidence prediction, and determining the filling pier radius R and grouting quantity Q by iteratively calculating to enable W to be smaller than a water-retaining coal mining aquifer subsidence threshold W max ; and 8, grouting in the caving zone by adopting a ground drilling grouting mode based on the key parameters obtained in the step to form a filling pier column so as to realize water-retaining coal mining, wherein the grouting process ensures that the slurry and the caving zone gangue are cemented to form a stable supporting structure.
2. The method for designing the key parameters of the water-retaining coal mining of the targeted grouting filling pier column according to claim 1, wherein the calculation formula of the drilling depth H ks of the grouting drilling hole in the step 3 is as follows: ; Wherein H 1 is the burial depth of the coal stratum, and the unit is m; H d is the height of the collapse zone, the unit is m, K 1 is a set drilling depth margin coefficient, and the value range of K 1 is 0.8-0.95.
3. The key parameter design method for water retention and coal mining of the targeted grouting filling pier column according to claim 2, wherein the caving zone void ratio in the step 4 is as follows The calculation formula is as follows: ; wherein K p is the expansion coefficient of the caving zone gangue, the value range of K p is 1.2-1.8, and the void ratio And the available space for quantifying grouting filling.
4. The key parameter design method for water retention and coal mining of the targeted grouting filling pier column is characterized in that the grouting material in the step 5 is prepared from ordinary Portland cement, gangue, fly ash and water, and the mechanical strength F and the flow characteristic of grouting consolidation are regulated and controlled by adjusting the water-cement ratio, the aggregate addition amount and the ratio of adding a water reducing agent and an accelerator, wherein the mechanical strength F of the grouting consolidation is required to meet the following conditions: ; The coal stratum is buried in the coal stratum, the unit of H 1 is m, the K 2 is the safety coefficient, and the value range is 1.1-1.5.
5. The method for designing key parameters of water retention and coal mining of the targeted grouting filling pier according to claim 1, wherein the calculation formula of the filling pier spacing D in the step 6 is as follows: ; wherein L t is the critical pushing length of insufficient mining, the unit is m, H 1 is the burial depth of the coal stratum, and the unit is m; In order to not fully exploit the critical coefficients, The value range of (2) is 1/3-1/2.
6. The key parameter design method for water retention and coal mining of the targeted grouting filling pier column is characterized in that the filling pier column in the step 7 is approximately in a truncated cone shape, the pier column height is determined based on the collapse zone height H d , and the calculation formula of the grouting quantity Q of the single pier column is as follows: ; wherein R is the radius of the bottom surface of the filling pier column, the unit is m, K 1 is the surplus coefficient of the drilling depth, and the value range is 0.8-0.95; the unit is the diffusion stacking angle of the slurry; The void fraction of the collapse zone.
7. The key parameter design method for water retention and coal mining of the targeted grouting filling pier column according to claim 6, wherein the probability integration method for predicting the subsidence of the rock stratum in the step 7 comprises the following steps: a) Setting a plurality of candidate values of the bottom surface radius R of the filling pier column; b) Aiming at each R candidate value, obtaining a corresponding maximum subsidence value W of a target protection aquifer through rock stratum movement prediction analysis; c) Drawing a relation curve of the maximum sinking value W along with the change of the radius R of the bottom surface of the filling pier column; d) Determining a critical value of the bottom radius R of the filling pier column meeting W≤W max from the relation curve according to a water-bearing stratum subsidence threshold W max required by water retention coal mining, thereby determining a designed R value; e) Substituting the determined R critical value into a calculation formula of the pier column grouting quantity Q, and calculating to obtain the grouting quantity Q.
8. The method for designing the key parameters of the water retention coal mining of the targeted grouting filling pier column is characterized in that in the step 8, drilling construction is carried out by adopting a casing drilling technology, grouting drilling holes are arranged at intervals along the advancing direction of a working face, the interval distance is the distance D between the filling pier columns, slurry is injected into a collapse zone through the drilling holes in the grouting process, and grouting filling pier columns are formed by utilizing the self-weight diffusion and cementing effect of the slurry and gangue, wherein the grouting filling pier columns are used for supporting an overlying stratum so as to control the structural stability of an aquifer.

Description

Key parameter design method for water retention and coal mining of targeted grouting filling pier column Technical Field The invention belongs to the technical field of coal mining, and particularly relates to a key parameter design method for water retention and coal mining of a targeted grouting filling pier column. Background With the development of coal resources, underground mining activities inevitably disturb the overlying strata, so that water guide fracture zones develop, and the aquifer structure is destroyed, and a series of ecological environment problems such as underground water level drop, dead earth surface vegetation, water and soil loss and the like are caused. In the traditional water-retention coal mining technology, the filling mining method is one of effective ways for protecting the aquifer by controlling the rock stratum movement through the filling body. However, the methods such as the back filling of the bracket, continuous mining and continuous filling and the like in the prior art have obvious limitations that the methods often interfere with the coal mining process in time and space, the filling operation needs to be carried out in a coal mining gap, the working face extraction efficiency is reduced, and the requirements of high strength and continuous mining are difficult to adapt. In addition, the parameter design of the traditional filling method depends on experience estimation, and lacks scientific quantitative basis, so that the supporting effect is unstable and the economical efficiency is poor. Disclosure of Invention In order to solve the technical problems of the background technology, the invention provides a key parameter design method for water retention and coal mining of a targeted grouting filling pier column, which is characterized in that grouting filling is carried out at intervals on a caving zone of a goaf behind a working face, slurry and gangue in the caving zone are cemented to form a filling pier column so as to stably support an overlying rock layer and control the rock layer to sink, thereby keeping the structure of a water-bearing layer with water supply significance and ecological value stable and realizing water retention and coal mining, and the method comprises the following steps: Step 1, collecting mine hydrogeology and mining geological data, and acquiring burial depth H 1, thickness M, physical and mechanical parameters, working face size and crushing expansion coefficient K p of the caving zone gangue of a goaf of a coal stratum; Step 2, based on the data obtained in the step 1, a goaf caving zone model is built through discrete element numerical simulation software UDEC, rock stratum caving behavior of a working surface under the condition of insufficient mining critical propulsion length is simulated, and caving zone height H d of the working surface under the condition of insufficient mining critical propulsion length L t is determined, wherein the insufficient mining critical propulsion length L t is dynamically determined through simulating a rock stratum caving process, so that a critical state when the working surface is propelled to a rock stratum caving stability is represented; Step 3, calculating the drilling depth H ks, of the grouting drilling holes according to the height H d of the caving belt, wherein H ks is used for ensuring that the drilling holes penetrate through the caving belt and leave a safety margin; step 4, calculating the void ratio of the caving belt based on the crushing expansion coefficient K p of the caving belt in the goaf The void fractionCharacterizing the void ratio in the collapse zone for grouting filling; Step 5, preparing grouting materials with different mechanical strength and flow characteristics, and testing the mechanical strength F and slurry diffusion stacking angle of the grouting materials in a laboratory Selecting grouting materials meeting the supporting requirement according to the test result; Step6, according to the insufficient mining critical coefficient Determining a filling pier column interval D, wherein the interval D is used for ensuring that the pier columns are spaced to support an overlying strata and controlling the strata to sink; step 7, calculating a maximum subsidence value W of a target protection aquifer under the condition of different filling pier bottom surface radiuses R by using a probability integration method of stratum subsidence prediction, and determining the filling pier radius R and grouting quantity Q by iteratively calculating to enable W to be smaller than a water-retaining coal mining aquifer subsidence threshold W max; and 8, grouting in the caving zone by adopting a ground drilling grouting mode based on the key parameters obtained in the step to form a filling pier column so as to realize water-retaining coal mining, wherein the grouting process ensures that the slurry and the caving zone gangue are cemented to form a stable supporting structure. In an