Abstract
In underground mining engineering, rocks around the entry are always subjected to large plastic deformation disasters, such as supporting body failure, roof rock collapse, and even rock burst under abutment stress and dynamic stress. To improve the stability of these rocks, the entry layout under abutment stress and dynamic stress (ELAD) method was put forward to protect the entry from high abutment stress and dynamic stress. Dynamic disturbance intensity (DDI) was determined as the key evaluation index in ELAD, which was divided into “Slightly Disturbed Type,” “Moderately Disturbed Type,” and “Violent Impact Type” by the dynamic disturbance threshold (DDT) and dynamic large-deformation threshold (DLT). The established servo calculation algorithm was applied into a dynamic and static numerical analysis model with FLAC3D500 software for the solving of DDT and DLT by the method of zero growth DDI of plastic failure zone and the engineering-permitted limitation deformation. This model was validated by comparing the displacement of entry with the measured results in the field. The model results validated that the entry should keep away from the dynamic stress of Violent Impact Type firstly and then be arranged in the zone where the dynamic stress belongs to Slightly Disturbed Type. DDT increases linearly and DLT decreases with a power function as the increasing of the abutment stress. ELAD method is reliable to protect this kind of underground entry and its applicability will be improved by the support resistance by comparing the results from ELAD with those from the widely used methods for field investigation discussion. The analysis procedure can be repeatable and necessary since the rock and coal materials may be different in geological and engineering conditions.
Highlights
Underground space has become one of the widely used resources during social development in recent years, and it will provide security for human civilization for a long time in the future [1,2,3]
Dynamic disturbance threshold (DDT) was proposed to prevent the rock from additional plastic deformation (APD), which can be calculated by the method of zero growth Dynamic disturbance intensity (DDI) of plastic failure zone. is method has the advantage of limiting the expansion of the plastic zone of the rock around the entry under the stress wave, which makes DDI of the plastic failure zone equal one
DDI is the key technology parameter in ELAD, which is divided into three grades, “Slightly Disturbed Type,” “Moderately Disturbed Type,” and “Violent Impact Type.” e entry should keep away from the dynamic stress of Violent Impact Type firstly and be arranged in the zone where the dynamic stress belongs to Slightly Disturbed Type
Summary
Underground space has become one of the widely used resources during social development in recent years, and it will provide security for human civilization for a long time in the future [1,2,3]. Influenced by the dynamic disturbance and the abutment stress, the stress will change into another state in the rock around the entry [4]. Is entry will suffer from large deformation disasters, such as supporting body failure, roof rock collapse, and even rock burst when the disturbance and stress is large enough, which threatens the normal operation of mining engineering [5]. For a specific geological condition, reduction of the loading stress has been a popular way to protect this entry from large deformation disasters in longwall coal mining engineering [6]. E loading stress mainly consists of original stress, abutment stress, and dynamic stress [7,8,9]. e abutment stress is the loading effect of the overburden rocks’ weight
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