Under the condition of bad undercutting, ore pillars are easily left in undercut level in block caving method. In order to reveal the evolution mechanism of ground pressure damage induced by bad undercutting, according to the actual engineering and physical parameters of the mine, a numerical simulation model was established by finite difference software FLAC3D. In the simulation process, the extraction level excavations were excavated first according to the post-undercutting method, and the process of the undercutting were divided into three steps. In the first step, a pillar of 15 m × 5 m was formed. The stress state of extraction level excavations and overlying ore body after each step was monitored and analyzed separately, and it was compared with the actual situation of ground pressure disaster on site. The results show that: Under the influence of high horizontal in situ stress, with the development of undercutting, the special stress state in the extraction level excavations are gradually formed, which is that the compressive stress concentrates on the upper part and the tensile stress concentrates on the lower part. With the development of undercutting, the remaining ore pillar form a certain range of tension stress release area above the undercut level, which makes it difficult for overlying ore and rock to cave in, thus causing the phenomenon of “less ore and no ore” in the draw bells.

methods

Influence of irregular boundary weakening on the block caving process

Ground Pressure Damage Evolution Mechanism of Extraction Level Excavations Induced by Poor Undercutting in Block Caving Method

The jointed rock-mass for the reheloogic fracture criterion under the inducing condition is a key to the success of the natural caving. And the rheologic fracture of jointed rock mass under induced condition was studied in this paper. Three kinds of different failure mechanisms of jointed rock mass for the rheologic fracture were induced. And a uniform failure criteria based on these failure mechanisms was obtained, which was judged according to the length of wing crack in the jointed rock mass. In this foundation, three necessary conditions such as the failure condition, the free face condition and the equilibrium condition were proposed firstly for the jointed rock mass to block caving under the action of gravity. And the criterion mathematical expression of rheologic fracture and block caving of the rock mass was deduced and established. Finally, the research results had been transformed to the computer program, which can provide a new and effectual way for us to study and predict the rule of block caving of rheologic fracture ore-rock.

Influence of irregular boundary weakening on the block caving process

Citations

Ground Pressure Damage Evolution Mechanism of Extraction Level Excavations Induced by Poor Undercutting in Block Caving Method

Study on the block-caving criterion of rheologic fracture of jointed rockmass under inducing condition

References

Influence of block boundary weakening on the caving process

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