Abstract
The width design of protective pillars is an important factor affecting the stability of high-stress roadways. In this study, a novel numerical modeling approach was developed to investigate the relationship between protective pillar width and roadway stability. With the 20 m protective pillar width adopted in the field test, large deformation of roadways and serious damage to surrounding rocks occurred. According to the case study at the Wangzhuang coal mine in China, the stress changes and energy density distribution characteristics in protective pillars with various widths were analysed by numerical simulation. The modeling results indicate that, with a 20 m wide protective pillar, the peak vertical stress and energy density in the pillar are 18.5 MPa and 563.7 kJ/m3, respectively. The phenomena of stress concentration and energy accumulation were clearly observed in the simulation results, and the roadway is in a state of high stress. Under the condition of a 10 m wide protective pillar, the peak vertical stress and energy density are shifted from the pillar to roadway virgin coal region, with peak values of 9.5 MPa and 208.3 kJ/m3, respectively. The decrease in vertical stress and energy density improves the stability of the protective pillar, resulting in the roadway being in a state of low stress. Field monitoring suggested that the proposed 10 m protective pillar width can effectively control the large deformation of the surrounding rock and reduce coal bump risk. The novel numerical modeling approach and design principle of protective pillars presented in this paper can provide useful references for application in similar coal mines.
Highlights
With increased mining depth, the failure of protective pillars in deep high-stress roadways has received much attention [1]. e influence of the protective pillar design on the stability of roadways has a bearing on worker safety and the effective mining of coal resources
E original balanced state of the main roof above the roadway is strongly disturbed during the panel retreat period. e main roof is broken [37,38,39], as shown in fracture position and rotating speed are closely related to the pillar width
According to the ultimate balance theory, the geometry size l of rock B can be derived from the panel dip length S and periodic breakage length L of the main roof, as in the following formula [40, 41]:
Summary
The failure of protective pillars in deep high-stress roadways has received much attention [1]. e influence of the protective pillar design on the stability of roadways has a bearing on worker safety and the effective mining of coal resources. Various numerical simulations have been adopted to analyse the effect of the protective pillar width on the roadway stability because of their low cost and high efficiency [9]. Us, the evolution laws of energy stored in a rock mass can be inferred by the change in stress, decreasing or avoiding the deformation failure of the surrounding rock and the occurrence of coal bump In view of these limitations in current simulations and considering the supporting feature of gob caving materials and the relationship between the stress and energy of the rock mass, a numerical modeling is developed to analyse failure mechanism for protective pillars. The effect of the optimal protective pillar on controlling the deformation of the surrounding rock is evaluated by a field test. e modeling approach and design principle presented in this paper can be used to analyse the protective pillar design of high-stress roadways at other similar sites
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
