scholarly journals Mechanism and Prevention of Rockburst in Steeply Inclined and Extremely Thick Coal Seams for Fully Mechanized Top-Coal Caving Mining and Under Gob Filling Conditions

Energies ◽  
2020 ◽  
Vol 13 (6) ◽  
pp. 1362 ◽  
Author(s):  
Shengquan He ◽  
Dazhao Song ◽  
Zhenlei Li ◽  
Xueqiu He ◽  
Jianqiang Chen ◽  
...  
Keyword(s):  
Pressure Coefficient ◽  
Influence Factors ◽  
Deformation Energy ◽  
Coal Seams ◽  
Force Coefficient ◽  
Pressure Relief ◽  
Roof Structure ◽  
Damage Degree ◽  
Dip Angle ◽  
Suspended Roof

The steeply inclined and extremely thick coal seams (SIETCS) under the condition of gob filling frequently suffer from the occurrence of rockbursts. Figuring out the mechanisms of rockbursts under this condition for taking targeted measures to mitigate rockburst hazards in SIETCS is of great significance. Using the typical SIETCS with an average dip angle of 87° at Wudong Coal Mine (WCM) as a case study, a mechanical model and elastic deformation energy (EDE) function of a “steeply inclined suspended roof structure” was developed, and the influence factors were analyzed by theoretical analysis. Simultaneously, the rockburst risk assessment was carried out based on the theory of a rockburst start-up. The pressure relief measures are optimized by comparing the pressure relief effects of three kinds of destress blasting schemes. The results indicate that the damage characteristics of rockburst are mainly floor heave, the sidewall’s inward deformation and roof subsidence. The damage degree of headentry on the roof side is more severe than that of tailentry, and the resultant impacts showed the directionality from the roof side to the coal side. The steeply inclined and suspended roof breakage is one of the main causes for the occurrence of rockbursts. The EDE of the roof increases with an increasing dip angle of the coal seam from 0° to 72.6° and then decreases as the dip angle increases. Furthermore, that increase is accompanied by the decrease of the lateral pressure coefficient and the supporting force coefficient. The EDE stored in the roof is sufficient to cause roof breakage and induce rockburst after the complete roof exceeds a certain length. The mechanism of rockburst in SIETCS for fully mechanized top-coal caving mining under gob filling conditions was proposed, i.e., “high compressive stress concentration plus breakage of the suspended roof-induced stress” rockburst, and this is further verified by ground destruction, microseismic (MS) monitoring and numerical modeling. The results also indicate that alternate deep and shallow hole-blasting modes are more suitable for pressure relief in SIETCS.

scholarly journals Research on the Transmission of Stresses by Roof Cutting near Gob Rocks

Energies ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1237
Author(s):  
Zhibiao Guo ◽  
Haohao Wang ◽  
Zimin Ma ◽  
Pengfei Wang ◽  
Xiaohui Kuai ◽  
...  
Keyword(s):  
Early Stage ◽  
Pressure Coefficient ◽  
Influence Factors ◽  
Stress Transfer ◽  
Main Roof ◽  
Surrounding Rock ◽  
Pressure Relief ◽  
Rock Structure ◽  
Immediate Roof ◽  
The Stability

Pressure relief for roadways retained by roof cutting is essentially caused by stress transfer. In this paper, the stress transfer mechanism of 16011 tail entry with roof cutting in Zhaogu No.1 coal mine is studied from the following two aspects: the change of the tail entry surrounding the rock structure and the interaction between the roadway surrounding rock and supporting structures. It is found by numerical simulation that roof cutting can significantly reduce the magnitude of roadway roof stress, transferring the concentrated stress induced by excavation and mining away from the roadway, and forming an obvious triangle pressure relief area in front of the working face. In the early stage after mining, most of the overburden load is transferred downward through the immediate roof of the roadway. With the movement of overlying strata, the stress, initially transferred to the immediate roof strata, is gradually transferred to the gob, and the calculation formula and influence factors of the transferred stress are derived. In addition, through the establishment of the mechanical model and theoretical calculation of the key rock block of the main roof, the roadside support resistance required to ensure the stability of the main roof block is determined. The field monitoring shows that the lateral pressure coefficient of the roadside caved rocks is 0.36 and the constant resistance and large deformation anchor cable (CRLDAC) and the roadway temporary support play roles of conduction and control in the process of stress transfer, and effectively ensure the stability of surrounding rock during the service life of the retained gob-side entry by roof cutting (RGERC).

Study on Influence Factors of Underground Joint Rock Cavern Displacement

2013 ◽  
Vol 353-356 ◽  
pp. 1515-1518
Author(s):  
Zhen Wang ◽  
Chun Han
Keyword(s):  
Lateral Pressure ◽  
Pressure Coefficient ◽  
Influence Factors ◽  
Two Dimensional ◽  
Tunnel Excavation ◽  
Lateral Pressure Coefficient ◽  
Rock Cavern ◽  
The Many ◽  
Rock Tunnel ◽  
Joint Rock

The safety response of joint rock underground tunnels is one of the many problems that draw the attention of geology specialists and scholars. Adopting two dimensional discrete element method, a numerical model of joint rock underground cavern is established to study its stability. The buried depth and the lateral pressure coefficient are considered respectively. The result shows: when the lateral pressure coefficient is identical, the depth is bigger the displacement is more bigger, and the displacement is strong influenced by the buried depth when the lateral pressure coefficient is big; In the same depth the tunnel is buried, the tunnel rocks displacement is slightly influenced by the lateral pressure coefficient when it is small, but the influence is seriously as the lateral pressure coefficient is big. The simulation in the context can be used to provide guide for joint rock tunnel excavation and supporting.

Damage and Springback Analysis of Two Typical Dented Pipelines With Different Parameters

2019 ◽  
Vol 141 (4) ◽  
Author(s):  
Ying Wu ◽  
Jiacheng Li ◽  
Linya Li
Keyword(s):  
Internal Pressure ◽  
Influence Factors ◽  
Influential Factors ◽  
Orthogonal Experimental Design ◽  
Damage Degree ◽  
Gray Correlation Degree ◽  
Correlation Degree ◽  
Gray Correlation ◽  
Nonlinear Regression Method ◽  
Dent Depth

During pipeline construction, the pipeline may be impacted by sharp rocks or excavators. To study the failure mechanism of the pipeline, the damage degree and springback rate of the pipelines with two typical dents (transverse and longitudinal) were analyzed in terms of various factors (indenter size, pipeline size and internal pressure, and dent depth). The results reveal the following: (1) when pipeline size and internal pressure are unchanged and indenter size is changed, the integral value I used to measure the damage degree of the dented pipeline increases with increasing dent depth. When the dent depth reaches a certain value, at the same dent depth, the smaller the indenter size, the larger the damage integral value; (2) when other parameters remain unchanged, the larger the pipeline size is, the larger is the damage integral value, and the larger the internal pressure is, the smaller is the damage integral value. (3) The curves for damage and springback for the two kinds of dents are basically similar. Generally, the maximum damage of the longitudinal dent is larger than that of the transverse dent. (4) By a combination of an orthogonal experimental design and a gray correlation degree calculation, for the damage integral value of the two typical dented pipelines, the order of importance of the influential factors was obtained. (5) Formulas for the damage integral value and influence factors were fit using a nonlinear regression method, which provides a reference for calculation of pipeline damage.

scholarly journals Investigation of Hydraulic Fracturing Crack Propagation Behavior in Multi-Layered Coal Seams

2020 ◽  
Vol 10 (3) ◽  
pp. 1153 ◽  
Author(s):  
Shirong Cao ◽  
Xiyuan Li ◽  
Zhe Zhou ◽  
Yingwei Wang ◽  
Hong Ding
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Crack Propagation ◽  
Principal Stress ◽  
Fracture Propagation ◽  
Clean Energy ◽  
Burial Depth ◽  
Coal Seams ◽  
Initiation Pressure ◽  
Dip Angle

Coalbed methane is not only a clean energy source, but also a major problem affecting the efficient production of coal mines. Hydraulic fracturing is an effective technology for enhancing the coal seam permeability to achieve the efficient extraction of methane. This study investigated the effect of a coal seam reservoir’s geological factors on the initiation pressure and fracture propagation. Through theoretical analysis, a multi-layered coal seam initiation pressure calculation model was established based on the broken failure criterion of maximum tensile stress theory. Laboratory experiments were carried out to investigate the effects of the coal seam stress and coal seam dip angle on the crack initiation pressure and fracture propagation. The results reveal that the multi-layered coal seam hydraulic fracturing initiation pressure did not change with the coal seam inclination when the burial depth was the same. When the dip angle was the same, the initiation pressure linearly increased with the reservoir depth. A three-dimensional model was established to simulate the actual hydraulic fracturing crack propagation in multi-layered coal seams. The results reveal that the hydraulic crack propagated along the direction of the maximum principal stress and opened in the direction of the minimum principal stress. As the burial depth of the reservoir increased, the width of the hydraulic crack also increased. This study can provide the theoretical foundation for the effective implementation of hydraulic fracturing in multi-layered coal seams.

Preliminary Investigation of Influence Factors of Sideway Force Coefficient Using SCRIM

2015 ◽  
Vol 744-746 ◽  
pp. 1344-1348
Author(s):  
Chun Hua Hu ◽  
Fang Yu
Keyword(s):  
Test Temperature ◽  
Environmental Conditions ◽  
Preliminary Investigation ◽  
Influence Factors ◽  
Force Coefficient ◽  
Speed Test ◽  
Routine Investigation ◽  
Test Speed

In this paper, advantages of the Sideway Force Coefficient Routine Investigation Machine (SCRIM) are analyzed for testing the Sideway Force Coefficient (SFC). Then influence factors are explored such as environmental conditions (test speed, test temperature, bumps degree) on the SFC test value. Furthermore some suggestion are put forward for SCRIM testing SFC value, and the safety precautions are emphasized on what drivers should pay more attention.

Predicting Model of Safe Distance between Tunnel and Karst Cave

2013 ◽  
Vol 470 ◽  
pp. 862-865
Author(s):  
Yong Biao Lai ◽  
Meng Shu Wang ◽  
Cheng Uang Bai
Keyword(s):  
Poisson Ratio ◽  
Pressure Coefficient ◽  
Influence Factors ◽  
Friction Angle ◽  
Support Vector ◽  
Karst Cave ◽  
Safe Distance ◽  
Predicting Model ◽  
Rock Density ◽  
Concealed Karst Cave

A method of predicting safe distance between tunnel and karst cave based on support vector machine was proposed, 10 parameters (rock density,elasticity modulusE, poisson ratio, friction angle, cohesionC, lateral pressure coefficient , the karst cave spanL,rate between height and span of the Karst caveR, tunnel deepH,cave position) were chosen for safe distance influence factors, then an intelligent predicting model of safe distance between tunnel and karst cave was built, this predicting model can predict 7 kinds position of safe distance between tunnel and concealed karst cave and was feasible and high prediction precision, which was verified by engineering example.

The controlling effect of thick-hard igneous rock on pressure relief gas drainage and dynamic disasters in outburst coal seams

2013 ◽  
Vol 66 (2) ◽  
pp. 1221-1241 ◽  
Author(s):  
Liang Wang ◽  
Yuan-ping Cheng ◽  
Chao Xu ◽  
Feng-hua An ◽  
Kan Jin ◽  
...  
Keyword(s):  
Igneous Rock ◽  
Coal Seams ◽  
Pressure Relief ◽  
Gas Drainage ◽  
Controlling Effect

scholarly journals Investigation on Surrounding Rock Stability Control Technology of High Stress Roadway in Steeply Dipping Coal Seam

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Honglin Liu ◽  
Chen Xu ◽  
Hongzhi Wang ◽  
Guodong Li ◽  
Sanyang Fan
Keyword(s):  
Distinct Element ◽  
High Stress ◽  
Horizontal Stress ◽  
Stability Control ◽  
Surrounding Rock ◽  
Coal Seams ◽  
Practical Applications ◽  
Rock Stability ◽  
Distinct Element Code ◽  
Dip Angle

There are a large amount of steeply dipping coal seams deposited in China, the safe and effective extraction of which are the challenge for coal operators due to the complicated geological characteristics, in particular, when the underground roadway is excavated in the steeply dipping coal seams with limited seam distance. The Universal Distinct Element Code (UDEC) was adopted in the present research to explore the stress distribution of surrounding rock of the roadway. Based on the numerical simulation, the damage coefficient was proposed and then used to classify the roof conditions into four groups. After that, the asymmetric support technique was proposed and put into practical applications. It is indicated that the stress concentration on the floor is the main feature of the extraction of steeply dipping coal seams. Moreover, the distributions of the maximum vertical stress and horizontal stress which are much different from each other mainly attributed to the effect of the large dip angle. This research also verified the feasibility of using the asymmetric and partition support technique to maintain the integrity of the surrounding rock, as from the case study conducted at the 12032 longwall coal face of Zhongwei coal mine.

scholarly journals Mechanisms and Applications of Pressure Relief by Roof Cutting of a Deep-Buried Roadway near Goafs

Energies ◽  
2020 ◽  
Vol 13 (21) ◽  
pp. 5732
Author(s):  
Peng Li ◽  
Xingping Lai ◽  
Peilin Gong ◽  
Chao Su ◽  
Yonglu Suo
Keyword(s):  
Physical Simulation ◽  
Coal Mines ◽  
Coal Pillar ◽  
Pressure Relief ◽  
Roof Structure ◽  
Key Block ◽  
Ground Stress ◽  
Surrounding Rock Control ◽  
The Stability ◽  
Superposition Effect

Affected by high ground stress, the surrounding rock control of a roadway is one of the most important factors restricting the utilization of deep resources. Therefore, it is necessary to propose a method to improve the stress environment of the deep-buried roadway and reduce its deformation. The article focuses on the 121,302 machine roadway in Kouzidong coal mine to analyze the large deformations of roadways near goafs (RNGs) in deep coal mines and reveal the mechanisms related to pressure relief via roof cutting. Through physical simulation, overburdened structures and the migration laws of RNGs in deep coal mines are studied, and the overburdened RNGs will eventually have a double short-arm “F”-type suspended roof structure. The superposition movement of the structure is the prime cause for the large deformation of the RNGs considered here. Artificial roof cutting can weaken the superposition effect of the double “F” structure and induce the roof to produce a new fracture. Meanwhile, sliding deformation along the fault line releases greater stress, and the cut roof can better fill the goaf. The stress distribution ratio between goafs and the coal pillar is improved. Here, a mechanical model of key block B’ (KBB’) is considered and the stability criterion of KBB’ is obtained. According to the theoretical calculation here, the stress of a coal pillar could be reduced by 19.14% when KBB’ is cut along the edge of the coal pillar in the 121,302 machine roadway. After engineering verification, the field observation result shows that the deformation of the 121,302 machine roadway is reduced by more than 50% after roof cutting.

Sign in / Sign up

Export Citation Format

Share Document