有限元极限分析法探讨裂隙拱形成机理

Analysis on Formation of Roof Fissure Arch by Limited FEM

以平面应变条件下Drucker-Prager为屈服准则,并给出强度增加系数的适用范围;采用有限元极限分析法,不断增加煤层、上覆岩层强度以至上覆岩层处于极限平衡状态,上覆岩层出现连续、贯通的塑性区,说明上覆岩层存在"塑性体"拱状结构;裂隙拱结构水平应力高于垂直应力、拱脚应力高于拱顶,符合拱结构受力特征。开采跨度增加,煤壁支撑压力不断增加,采空区底板支撑应力非常有限;裂隙拱跨度增加,拱高不断增加,拱跨比逐渐降低,说明采动对裂隙拱拱高的影响是有一定范围的。

The yield criterion of Drucker-Prager has been used at the plain strain state,and the compatibility of the increased strength factor has been analyzed.The limit balanced condition of the roof stratum has been achieved by strength increasing and the method of limit analysis of FEM was used.Continuous penetrating plastic zone has been appeared on the roof stratum in the test,which proves the hypothesis about existence of arch structure of plastic body.The horizontal stress is larger than the vertical stress and the stress on the arch roof larger than that on the arch apex,which agrees with the characteristics of arch stress.The supporting pressure on the coal rib increases with mine span and the supporting pressure is quite limited on the floor.The arch rise increases with fissure arch span,the ratio of arch rise to arch span reduces gradually which states that the influence of mining on arch rise is limited in some range.