考虑主应力偏转的采动诱发断层活化机理研究

Fault reactive induced by the principal stress rotation for the underground coal mining

为探讨采动诱发应力场偏转活化断层机理,采用库仑破裂应力增量为断层单元活化判据,引入损伤因子评价断层面活化滑移破坏程度,模拟分析了主应力偏转对不同倾角断层面上应力分布及断层滑移量的影响.研究表明:采动诱发主应力偏转使得沿断层面剪应力增加,而垂直于断层的正应力又受开采卸压和应力偏转影响而减小;断层倾角越大,断层面上剪应力增量对主应力偏转响应越明显;逆断层下盘工作面向断层方向回采时,断层面附近区域底板主应力最先发生偏转,顶板处主应力偏转滞后于煤层和底板,然而顶板中主应力偏转量最大.不同断层倾角断层损伤因子随主应力偏转角变化呈倒"S"型变化.对于倾角分别为15°,30°,45°和60°断层,当最大主应力偏转至垂直断层时,断层面库仑破裂应力和损伤因子均最小;而偏转至平行断层时,断层库仑破裂应力和损伤因子最大,损伤因子最大值约为最小值的8.5~9.2倍.

In order to investigate the fault slip mechanism under the rotation of principle stress induced by coal excavation,the Coulomb failure stress increment was used as the fault activation criterion,and the damage factor was introduced to evaluate the degree of fault slip failure.The influences of principal stress rotation on stress distribution and fault slip along the fault plane with different dip angles were analyzed with numerical simulation method.The results show that the principal stress deflection induced by mining activities makes the shear stress increase along the fault plane,while the normal stress perpendicular to the fault is reduced by the pressure relief and stress deflection.The larger the fault angle,the more obvious the shear stress increment on the fault plane.When the footwall of reverse fault works in the direction of fault,the principal stress of the bottom plate near the fault plane is deflected first,and theprincipal stress deflection at the roof is lagging behind the coal seam and the bottom plate.The principal stress deflection at the roof lags behind the coal seam and floor.The damage factor of different fault dips changes with deflection angle of principal stress in an inverted ＂ S＂ shape change.For the dip angle is 15°,30°,45°and 60°of fault,the Coulomb failure stress and damage factor are the smallest when the maximum principal stress is deflected to the vertical fault.When the deflection is parallel to the fault,the Coulomb failure stress and damage factor are the largest,the maximum value of the damage factor is about 8.5 to 9.2 times the minimum.