Mechanism of Overlying Crack-Stress Evolution When Mining on the Dual Fault Zone

Abstract

To study the fissure-stress evolution law of overburden rock in the process of working face advancing in the dual fault area. This paper took the geological occurrence condition and actual mining situation of working face 21,129 of Tucheng mine as the engineering background. The method of similarity simulation combined with field measurement was adopted. The evolution law of the stope fissure field, the stress variation trend of roof fault, and migration characteristics of overlying strata in the process of stope mining through dual faults were studied. The results showed that: Dual faults had a large effective area on the surrounding rock of the stope, the surrounding rock movement in the affected area was intense. When the working face advanced to the fault F2 area, the energy generated during the surrounding rock movement of the fault F2 was transferred to the fault F1, which intensified the activity of the rock in the fault F1 area. The activation of the fault F2 caused the fissures in the surrounding rocks of the fault F1 to expand further. The surrounding rock of the stope changed from a single-fault action mode to a double-fault joint action mode. According to the degree of development of cracks in the roof of the overlying strata, the stope’s different positions were sorted from large to small as follows: fault activated fracture zone > central dual fault zone > open-off cut zone > middle of the non-fault affected zone. The field measured data showed that the area affected by the dual fault was composed of “high-pressure area” and “low-pressure area.” The working resistance value of hydraulic support was higher than that of the non-fault affected area. The law of fracture development and distribution in overlying strata of stope in similarity simulation experiments were consistent with the law of roof pressure measured in the field.