Deformation characteristics and mechanism of deep subsize coal pillar of the tilted stratum

Energy Science & Engineering

Zheng

Shen

et al. 2019

The main entries in longwall coal mine frequently encounter large deformation, depending on the stress environment. Depressurizing boreholes are applicable to reduce the large deformation; however, it is difficult to determine the proper parameters (diameter and spacing) for an effective implementation. This study aims to propose feasible design criteria for the quantification of those parameters. We first developed a rigorous numerical model, for a roadway in Zhangshuanglou coal mine, using the rock mechanical properties determined from extensive laboratory measurements and analyses. We then investigated the dependency of the stress transfer and roadway deformation on the ratio of borehole diameter and spacing (D/R and D/I). The symbols of D, R, and I represented the diameter, row spacing, and interspacing of the boreholes, respectively. We found that (a) D/R has to be between 1:6 and 1:2; and (b) D/I has to be between 1:6 and 1:4, for sufficient depressurization in the surrounding rocks. The optimized borehole diameter and spacing parameters were applied in the field where the deformation of roadway was significantly reduced. Finally, we proposed a criterion to determine those parameters of depressurization boreholes for application in other geological and mining conditions.

Section: Discussionmentioning

confidence: 99%

Depressurizing boreholes for mitigating large deformation of the main entry

Energy Science & Engineering

Zheng

Shen

et al. 2019

“…e plastic area, radius of the fractured zone, and the surface displacement can effectively be reduced. e stability of the surrounding rock mass can be maintained [1,43]. Based on the deformational failure character of the anchorage body and the energy dissipating rule in section 4.2, this section explained the strength strengthening theory from the perspective of energy.…”

Section: Strengthening Of the High-performance Anchorage Bodymentioning

confidence: 99%

“…In recent years, the depth of coal mining has been increasing at an annual rate of 6-10 m [1]. Under the superposition of the high in situ stress and the strong mining stress in the surrounding rock of the deep roadway, the surrounding rock of the roadway is prone to unsteady failure characteristics, and it may cause disasters in severe cases.…”

Section: Introductionmentioning

confidence: 99%

A Study of the Anchorage Body Fracture Evolution and the Energy Dissipation Rule: Comparison between Tensioned Rock Bolts and Torqued Rock Bolts

Advances in Civil Engineering

Bai

et al. 2021

Rock bolt support is an effective technique for controlling surrounding rock of deep roadway. The stability of the anchorage body composed of rock bolts and surrounding rock mass is the core in keeping the stability of roadways. In this paper, the UDEC Trigon model was used in simulating uniaxial compressive test on the anchorage body under different pretension loads. The energy equilibrium criterion of the anchorage body under the uniaxial compressive state was proposed. Furthermore, the fracture evolution and the energy dissipation during the failure process of the anchorage body were analyzed. Results showed that before the peak strength, the external work was stored in the anchorage body in the form of the elastic strain energy (Ue). After the peak, energy dissipated through three ways, including the fracture developing friction (Wf), plastic deformation (Wp), and acoustic emission (Ur). Based on the simulation results, the high pretensioned rock bolts can eliminate the continuous tensile fractures in the anchorage body, decreasing the damaging extent of the anchorage body and the energy that was consumed by the following two main approaches: fracture developing friction (Wf) and plastic deformation (Wp). Moreover, the surplus of the elastic strain energy (Ue) and the strength of the anchorage body can be improved. The pretension load had a positive relationship with elastic strain energy and a negative relationship with the anchorage body damage degree. Based on the above research, the transport roadway of the working face 6208 in the Wangzhuang Coal Mine selected tensile rock bolts to establish the high-performance anchorage body. The monitoring data showed that this reinforcement method effectively managed the serious deformation issue of the roadway surrounding the rock masses.

“…The stress of surrounding rock is redistributed after the roadway is excavated. 22,23 When the surrounding rock stress exceeds the stress limit of the surrounding rock, plastic deformation occurs in the surrounding rock. According to the range characteristics of the plastic region, the plastic region is divided into three types: circular, oval, and butterfly.…”

Section: Deformation Mechanism Of the Surrounding Rock Of The Roadwaymentioning

confidence: 99%

Research on large deformation mechanism of deep roadway with dynamic pressure

Fan

Energy Science & Engineering

Che

et al. 2020

Self Cite

In this paper, the large deformation mechanism of deep dynamic pressure roadway is studied from the perspective of the formation and development of plastic zone, and creep and damage of rock mass. The results show that (a) the butterfly‐shaped plastic zone is a nonstable plastic zone, and its unique stress sensitivity and rock formation difference are important causes of disasters such as large deformation of deep roadway. (b) Established a creep model of anchored surrounding rock. Due to the existence of rock mass damage and creep, the range of the plastic zone of the surrounding rock is always dynamic. (c) Explain the mechanism of large deformation of surrounding rock in deep roadway. The source of large deformation of deep dynamic roadway lies in the formation of unstable plastic duct‐shaped zone, and the interference of external factors such as tectonic stress and mining disturbance is the main way to change the plastic zone from stable to unsteady. In addition, the increase in rock mass damage and creep promotes the continuous development of the plastic zone, which eventually leads to the large deformation of the surrounding rock of the roadway. (d) Guided by the deformation mechanism of the surrounding rock in the deep dynamic pressure roadway, the corresponding roadway support technology was proposed for the test roadway, and the better support effect was obtained through the test.