scholarly journals Surrounding Rock Failure Characteristics and Water Inrush Mechanism of Roadway above the Aquifer in Nonuniform Stress Field

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Xiaofei Guo ◽  
Yongen Li ◽  
Jun Li ◽  
Hongyu Liu ◽  
Xianjie Ma ◽  
...  
Keyword(s):  
Stress Field ◽  
Plastic Zone ◽  
Water Inrush ◽  
Rock Failure ◽  
Surrounding Rock ◽  
Force Model ◽  
Confined Water ◽  
Nonuniform Stress ◽  
Maximum Radius ◽  
Nonuniform Stress Field

The expansion of the roadway surrounding rock failure zone may connect the floor aquifer and cause the roadway water inrush. In order to reveal the mechanism of the roadway water inrush above confined water, we established the force model of the roadway surrounding rock above confined water in nonuniform stress field and studied the shape characteristics and expansion law of the roadway surrounding rock plastic zone. The results show that the roadway surrounding rock will form three kinds of plastic zone under different lateral pressure coefficients: circular, elliptical, and butterfly; when the shape of plastic zone is circular or elliptic, the maximum radius increases linearly with the increase of regional stress; when the shape is butterfly, the maximum radius increases exponentially with the increase of stress. Under the condition of a larger bidirectional stress ratio, the surrounding rock of the roadway will show butterfly-shaped failure, and small stress change will cause malignant expansion of the plastic zone; when the plastic zone is connected with the underlying aquifer, confined water of floor will enter the rock mass from the water diversion point and eventually flood into the roadway, causing floor water inrush.

scholarly journals Elliptic Equation of Plastic Area Boundary around the Circular Laneway in Nonuniform Stress Field

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Xiaofei Guo ◽  
Linfeng Guo
Keyword(s):  
Stress Field ◽  
Elliptic Boundary ◽  
Pressure Ratio ◽  
Major Axis ◽  
Confining Pressure ◽  
Surrounding Rock ◽  
Minor Axis ◽  
Boundary Equation ◽  
Nonuniform Stress ◽  
Nonuniform Stress Field

In order to obtain the analytical solution of the plastic area boundary of circular laneway surrounding rock in nonuniform stress field, we studied the evolution of the plastic area shapes of the circular laneway surrounding rock from circular to elliptical and derived the analytical solutions of the boundary radii in the elliptical shape. The results show that (1) with the increase of the confining pressure ratio from 1, the major axis radius of the plastic area increases gradually, the minor axis radius decreases gradually, and the shape of the plastic area gradually evolves from circular to elliptical; (2) on the basis of the Mohr–Coulomb strength criterion, the analytical expressions of major axis and minor axis radii of the elliptical plastic area are derived, and the elliptic equation of the plastic area boundary of circular laneway in nonuniform stress field is established; and (3) the confining pressure ratio is the key factor affecting the shape of the plastic area. When the confining pressure ratio is less than 1.6, the plastic area of the circular laneway surrounding rock is elliptical, and the elliptic boundary equation is applicable. When the confining pressure ratio is greater than 1.6, the plastic area is butterfly shaped, and the elliptic boundary equation is no longer applicable.

scholarly journals Stability Analysis and Reasonable Layout of Floor Drainage Roadway above Confined Water and under Mining Influence

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Xiaofei Guo ◽  
Yongen Li ◽  
Guangdong Zhou ◽  
Zengji He ◽  
Haoran Yu ◽  
...  
Keyword(s):  
Plastic Zone ◽  
Water Inrush ◽  
Coal Pillar ◽  
Middle Part ◽  
Surrounding Rock ◽  
Confined Water ◽  
Working Face ◽  
Stress Environment ◽  
And Control ◽  
Sandy Mudstone

The surrounding rock failure range of floor drainage roadway under the mining influence and its effect on the aquiclude are the key to determine the aquiclude thickness of the floor. This paper studied the distribution characteristics of the surrounding rock plastic zone by the numerical simulation when the floor drainage roadway was located at different positions under the working face and determined the rational position. Results show that (1) when the floor drainage roadway is staggered inward, the floor surrounding rock is prone to appear the butterfly plastic zone under single work face mining. And the butterfly plastic zone increases sharply after being affected by secondary mining of adjacent working face. (2) When the floor drainage roadway is staggered outward, the floor surrounding rock plastic zone extends gently affected by a single working face. And the depth of the plastic zone has no obvious change after being affected by secondary mining of adjacent working face. (3) According to the risk of water inrush, the three layout schemes can be ranked as follows: stagger   inward   25   m > stagger   inward   80   m > stagger   outward   15   m . (4) Considering the floor stress environment, gas extraction efficiency, and water prevention and control, the reasonable location of floor drainage roadway below the No. 11060 working face of Zhaogu No. 2 Coal Mine was finally determined. It was arranged in the sandy mudstone layer on the upper part of L9 limestone under the middle part of coal pillar and was drived along the seam floor.

North China Lower Coal Surrounding Rock Failure Characteristics Study Based on FLAC3D and Fiber Bragg Grating

2013 ◽  
Vol 353-356 ◽  
pp. 1057-1062
Author(s):  
Zai Bin Liu
Keyword(s):  
Numerical Simulation ◽  
Fiber Bragg Grating ◽  
North China ◽  
Water Inrush ◽  
Rock Failure ◽  
Simulation Software ◽  
Surrounding Rock ◽  
Bragg Grating ◽  
Failure Characteristics ◽  
Test Face

In order to study north China type coal field lower coal surrounding rock failure characteristics, a numerical model was built based on the numerical simulation software FLAC3D. Water inrush information was monitored during mining process based on optical fiber Bragg grating sensor technology. Lower coal surrounding failure characteristics were studied according to numerical simulation and monitoring results. This study show that the first weighting distance of the test face is from 35m to 40m and the periodic weighting step distance is from 10m to 20m. Coal floor can be divided to three areas which are increased stress area, decreased stress area and recovery stress area. Coal roof failure scope is like a composition of two saddle-shaped zones along trend and tendency directions. Normal failure depth of the test face floor is from 10m to 12.5m, and it can reach 22.5m near open-off cut and stop line. The research can explain the reason of the test faces water inrush accident and can direct lower coal mine water control work.

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