Stress evolution of deep surrounding rock under characteristics of bi-modulus and strength drop

Abstract

Aiming at the circular chamber under uniform stress field in deep energy storage and mining, analytical solutions of stress and plastic zone of the surrounding rock under different far-field stress and internal pressure were derived based on bi-modulus theory and the elastic-brittle-ideal plastic constitutive model. Evolution trend of the elastic-plastic stress and plastic region with different elastic constant ratios and residual strength coefficients were analyzed in details. Results revealed that when the internal pressure was small, the three-direction principal stress was compressive stress and the stress field distribution of the surrounding rock was not affected by the moduli difference. The obtained solution was consistent with the solution from the elastic-brittle plastic drop model under the equal modulus theory. On the other hand, when the internal pressure was large, the tangential stress was changed. The surrounding rock can be divided into three zones, i.e., tensile plastic zone (TPZ), tensile elastic zone (TEZ) and compressive elastic zone (CEZ). The tensile and compressive dual modulus had significant influence on the demarcation point between TEZ and CEZ. In addition, the strength drop and the dual modulus characteristic had a coupling effect on the stress distribution in the surrounding rock. The related achievements further enrich the theory of deep rock mechanics.

摘要

深部地下空间开发在深地能源贮存与开采、生态圈与地下生态城市等领域都有着巨大的潜在价 值。针对深部均匀应力场作用下圆形硐室开挖, 采用拉压双模量理论和弹性-脆性-理想塑性本构模型, 推演了不同远场应力和内压力下围岩的应力解析解及塑性区边界方程, 详细分析了围岩弹塑性应力场 和塑性区随弹性常数比及残余**度系数的变化规律。结果表明:内压力较小时, 三向主应力均为压应 力, 围岩的应力场分布不受双模量影响, 与等模量理论下基于弹脆塑性跌落模型的求解结果相同; 内 压力较大时, 切向应力变号, 围岩可划分为切向拉应力塑性区(TPZ), 切向拉应力弹性区(TEZ)以及切 向压应力弹性区(CEZ)三个区, 拉压双模量对TEZ和CEZ两个区的分界线影响较大, **度跌落和双模 量特性对围岩的应力分布具有耦合作用。相关成果进一步丰富了深部岩石力学理论。