高水平地应力下自然崩落法底部结构灾变机理

Mechanism of ground pressure disaster evolution of extraction level excavations in block caving with high horizontal in situ stress

摘要:

为研究高水平地应力下自然崩落法拉底推进过程中底部结构应力演化规律,揭示底部结构地压灾害特征产生的机理,从而指导高水平地应力下自然崩落法生产. 根据矿山实际工程参数和物理参数,采用有限差分软件FLAC3D建立了数值仿真模型,计算采用Mohr-Coulomb破坏准则.模拟过程按照后退式拉底方式,先形成底部结构,然后拉底分3步进行,分别监测并分析了每步拉底之后的底部结构应力状态,并与现场地压灾害发生实际情况进行了对比,研究结果与现场地压灾害演变规律具有一致性. 结果表明:随着拉底爆破的推进,推进线前方的底部结构逐渐产生压应力集中,当压应力增大到超过岩体剪切破坏条件,就会发生地压破坏现象；位于拉底层下方的底部结构呈现拉应力集中,当拉应力增大到超过岩体拉伸破坏条件,就会再次发生地压破坏现象；在高水平地应力下,自然崩落法底部结构会呈现“先受压,后受拉”应力规律,随着拉底面积的增加,压应力和拉应力集中程度越来越明显,在实际生产中呈现底部结构反复来压的现象.

Abstract:

In order to guide the production of block caving method with high horizontal in situ stress, the stress evolution law of the extraction level excavations during the process of undercutting with high horizontal in situ stress was studied, and the occurrence mechanism of specific characteristics of ground pressure disaster in the extraction level excavations was revealed. According to the actual engineering and physical parameters of the mine, a numerical simulation model was established by using finite difference software FLAC3D, and Mohr-Coulomb failure criterion was adopted in calculation. In the simulation process, the extraction level excavations were excavated firstly according to the backward undercutting method. The process of the undercutting was divided into three steps, and the stress states of extraction level excavations after each step were monitored and analyzed respectively, which were compared with the actual situation of ground pressure disaster on site. The results are consistent with the evolution law of ground pressure disaster on site, showing that with the development of undercut blasting, compressive stress concentration gradually occurred in the extraction level excavations in the vicinity of the undercut front. Ground pressure disasters occurred when the compressive stress increased beyond the shear failure condition of rock mass. Tensile stress concentration appeared in the extraction level excavations below the undercut layer, and ground pressure disasters occurred again when the tensile stress increased beyond the tensile failure condition of rock mass. Under high horizontal in situ stress, the extraction level excavations of block caving method presented the stress law of "compressive stress concentration followed by tensile stress concentration". With the increase of undercut area, the extent of compressive stress and tensile stress concentration became increasingly obvious, thus ground pressure disasters occurred repeatedly in the extraction level excavations in actual production.