基于应力降的非连续支承压力强扰动特征研究

Strong disturbance of discontinuous abutment pressure

深部扰动定义及科学量化是重新理解地下工程灾害发生原因与强弱的前提。针对平顶山矿区千米埋深煤岩,基于三轴压缩试验获得Hoek-Brown与Mohr-Coulomb准则力学参数。基于Airey解,在弹塑性边界引入非连续应力降,突出体现为支承压力的非连续应力降与脆性指数评估,用于研究破坏后引起的连续–非连续过渡现象。引入基于内摩擦角或黏聚力的损伤到塑性区域以考虑非连续性,并应用于无煤柱开采、放顶煤开采与保护层开采下非连续支承压力分布求解。联合峰值应力、应力降、峰前峰后模量改变与残余塑性应变,定义了新的脆性指数,明确了脆性的三重内涵:外部应力扰动、变形特征与力学参量的综合影响。利用新指数定性解构了深部开挖扰动区,包括破碎区、峰后卸荷损伤区、应力跌落塑性区、峰前损伤区与内部原岩弹性升压区。最后提出基于不同开采方式α、脆性指数R、应力降Δσ_(drop)与原位应力场p_o定义的扰动指数Ф,明确Ф≥1时为强扰动。

The quantification of disturbances in deep engineering is a prerequisite to re-understand the causes of disasters. The mechanical parameters of Hoek-Brown and Mohr-Coulomb criteria according to the conventional triaxial compression tests are obtained for the coal at a depth of one thousand meter. Based on the Airey￠s solution,a discontinuous stress drop is introduced on the elasto-plastic boundary for the study of continuousdiscontinuous transition caused by the plastic failure,highlighting the stress drop and the brittleness index assessment of the abutment pressure. The damage based on the internal friction angle or cohesion degradation is defined to illustrate the discontinuities in plastic zones,and is applied to the discontinuous stress distribution in three various mining layouts including the non-pillar mining,top coal mining and protective coal mining. A new brittleness index is proposed considering the coupled influence of the peak stress,the stress drop,the post-peak modulus and the residual plastic strain,corresponding to the combined effect of external stress disturbances,deformation and mechanical parameters. The qualitative analysis of the strong disturbed zone based on the new definition mainly includes the fracture zone,the post-stress unloading zone,the stress drop zone,the damage zone and the elastic zone. Finally,we proposed a new disturbance index Ф based on the various mining layouts of α,the brittleness index R,the stress drop Δσdrop and the in-situ stress field po,and Ф≥1 is strong disturbance.