摘要
将岩体看成不含原生宏观裂隙而仅含原生微裂纹的颗粒材料。在开挖卸荷过程中,原生微裂纹启裂、扩展并穿过岩石基质,产生次生裂纹。此时,岩体出现非连续和非协调变形,经典的弹塑性力学理论不再适用于研究岩体的非连续和非协调变形情况。基于自由能密度、平衡方程和变形非协调条件,提出一种新的非欧模型,确定微裂纹半长度和密度对标量曲率和自平衡应力的影响,获得深部圆形洞室围岩应力场,它包括弹性应力和自平衡应力。由于自平衡应力的影响,当微裂纹的密度和半长度较大时,深部圆形洞室围岩的应力场具有明显的振荡特性。但是,当微裂纹的密度和半长度较小时,深部圆形洞室围岩的应力场振荡特性不明显。对于位于波峰附近的微裂纹,其尖端的应力集中将导致次生裂纹的失稳扩展、连接、合并成宏观裂隙,形成破裂区;而对于位于波谷附近的微裂纹,其尖端应力集中不足以导致次生裂纹发生失稳扩展,因此出现非破裂区。深部圆形洞室围岩应力场交替出现波峰和波谷现象导致破裂区和非破裂区的交替出现,即分区破裂化现象。通过数值模拟,详细研究微裂纹半长度和密度对深部岩体分区破裂化现象的影响。
Rock masses without pre-existing macrocracks are considered as granular materials with only microcracks.During excavation of tunnels,microcracks may nucleate,grow and propagate through rock matrix;secondary micrcracks may appear,and discontinuous and incompatible deformation of rock masses may occur.The classical continuum elastoplastic theory is not suitable for analyzing discontinuous and incompatible deformation of rock masses any more.A new non-Euclidean model is established based on free energy density,the equilibrium equation and the deformation incompatibility condition,where effects of the half length and density of microcracks on scalar curvature and the self-equilibrated stresses in deep rock mass are investigated.Stress fields in the surrounding rock masses around a deep circular tunnel are determined,which are the sum of elastic stresses and the self-equilibrated stresses determined by the scalar curvature.Due to the self-equilibrated stresses,the distribution of stresses in the surrounding rock masses around deep tunnels is obviously fluctuant or wave-like when the half length and density of microcracks are large,while the distribution of stresses in the surrounding rock masses around deep tunnels is not obviously fluctuant or wave-like when the half length and density of microcracks are small.The stress concentration at the tips of microcracks located in vicinity of stress wave crest is comparatively large,which may lead to the unstable growth and coalescence of secondary microcracks,and consequently the occurrence of fractured zones.On the other hand,the stress concentration at the tips of microcracks located around stress wave trough is relatively small,which may lead to arrest of microcracks,and thus to the non-fractured zones.The alternative appearance of stress wave crest and stress trough thus may induce the alternative occurrence of fractured and non-fractured zones in deep rock masses.The influences of the density and half length of microcracks on zonal disintegration and self-equilibrated s
出处
《岩石力学与工程学报》
EI
CAS
CSCD
北大核心
2013年第4期767-774,共8页
Chinese Journal of Rock Mechanics and Engineering
基金
国家自然科学基金资助项目(51078371
51279218
51021001)
重庆大学煤矿灾害动力学与控制国家重点实验室课题(2011DA105287-MS201204)
关键词
岩石力学
自平衡应力
分区破裂化现象
非欧模型
rock mechanics
self-equilibrated stresses
zonal disintegration phenomenon
non-Euclidean model
