Abstract
The stability of large section open-off cut in deep mines (LODM) is the key factor affecting the normal equipment installation and safe mining in fully mechanized top-coal caving face. The mechanical model shows that the deflection of the roof of the LODM is proportional to the cubic of span. In this paper, UDEC Trigon model is established, and the parameters of different coal measures strata are modified in detail. The evolution law, failure mode, and damage degree of roof cracks in secondary tunneling are studied, and the roof support effect is analyzed. The numerical simulation results show that the process of roof crack evolution after the primary excavation section and the second excavation section can be divided into three stages according to microseismic activities, and the reasonable supporting time can control the propagation of roof microcracks and reduce the development height of macrocracks. The rock bridge existing in the roof rock stratum after the combined support of long and short anchor cables can effectively limit the formation of macrocracks and their interaction; especially the key support in the interface area can reduce the development height of roof cracks in secondary tunneling and weaken the damage degree of roof rock stratum in the LODM. The field test shows that the moved volume of rib-to-rib and roof-to-floor of the LODM is stable at about 350 mm and 550 mm, respectively. The numerical simulation in this paper is helpful to understand the failure mode of roof in LODM with large mining height and provides a method for the design of its control technologies.
Highlights
Open-off cut is the place for equipment installation and mining initiation in coal mining face
After adopting the above optimized support scheme of the large section open-off cut in deep mines (LODM), the roof deformation of the two excavation sections of the roof of 5202 open-off cut is shown in Figure 14. e monitoring results show that the deformation of the roof strata of the 5202 open-off cut is effectively controlled, the deformation of the roof of the two excavation sections is stable for a period of time, and the convergence deformation of the roof-to-floor and the rib-to-rib of the LODM is 550 mm and 350 mm, respectively. e field application shows that the surrounding rock of roof has been effectively improved under the action of support of high-strength long and short anchor cable and bearing structure of high working resistance hydraulic prop
In order to solve the stability control problem of surrounding rock in the LODM, this paper systematically studies the evolution law of roof crack evolution, failure mode, and damage degree in secondary tunneling of the LODM by means of field investigation, theoretical calculation, numerical simulation, and engineering practice, compares and analyzes the control effect of roof crack and damage under three supporting conditions, and determines the reasonable support timing and control technical parameters. e main conclusions are as follows
Summary
Open-off cut is the place for equipment installation and mining initiation in coal mining face. Discrete element model is used to study the failure process of roof in the LODM, to determine the reasonable support timing of two excavation sections, and to systematically study the laws of crack propagation, failure mode, and damage degree of roof in the LODM. On this basis, the control effects of three support schemes on roof in open-off cut are put forward. Xin’an coal mine are determined, and the effect of supporting is monitored and evaluated on site. e research provides reference and referential significance for open-off cut stability research and supporting design under similar engineering geological conditions
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