单层采动诱发长壁开采水平岩层开裂、冒落过程模拟——基于连续-非连续方法

Modeling of Cracking and Caving of Horizontal Strata Induced by the Excavation of a Single Stratum in Long-wall Mining——Based on a Continuum-discontinuum Method

提出了一种适于模拟准脆性材料（岩石、混凝土等）变形、开裂、接触、摩擦及转动的连续-非连续方法。开展了单层采动诱发长壁开采水平岩层开裂、冒落过程的数值模拟研究。研究发现,在工作面推进过程中,顶板不断离层和开裂,开裂后岩块不断冒落,采空区和工作面上方的垂直应力低值区呈梯形,其尺寸不断增加,直至稳定;在垂直应力梯形低值区两个腰的位置及其顶部一定范围内,裂隙较为发育,垂直应力梯形低值区其余位置的裂隙被重新压实;在梯形低值区两个腰的位置,开裂后岩块倾斜排列,形如砌体;如果将每次工作面推进长度及每两次开采间隔的时步数目均翻番,则顶板冒落变晚,垂直应力梯形低值区的对称性变好,该差异根源于非线性动力学系统对于加/卸载历史的依赖性。在目前的模拟中,未考虑剪裂和液压支架的作用。

A continuum-discontinuum method is proposed to model a series of complex mechanical behaviors of quasi-brittle materials（rocks,concretes,etc.）,such as deformation,cracking,contact,friction and rotation.The method benefits from the Lagrange element method,the discrete element method and the fictitious crack model.Compared with the continuum method,the proposed method can model true cracking phenomena without remeshing.Compared with the discontinuum method,the proposed method can well treat the continuum medium before cracking.A numerical study is conducted to model the cracking and caving of horizontal strata induced by the excavation of a single stratum in long-wall mining.Results show that as the work face advances,the bed separation and cracking continuously occur in the roof.Rock blocks also continuously cave,and the region with lower vertical stresses in the roof is trapezoidal,whose size increases gradually until reaching a stable value.At two lateral sides and the top of the trapezoid,obvious cracks are observed;at other positions of the trapezoid,cracks are compacted.At two lateral sides of the trapezoid,rock blocks are obliquely arranged in the form of masonry structures.If the size of the ore body in an excavation and the number of timesteps between two adjacent excavations are increased,the caving of the roof arrives later,and the trapezoid tends to be more symmetric.These differences are related to the dependence on the loading/unloading history for a non-liner dynamic system.It has to be noted that shear fractures and the effects of hydraulic supports have not been considered in the present simulation.