考虑高地应力下围岩劣化的硬岩本构模型研究

STUDY ON CONSTITUTIVE MODEL OF HARD ROCK CONSIDERING SURROUNDING ROCK DETERIORATION UNDER HIGH GEOSTRESSES

鉴于高地应力环境下洞室开挖过程中围岩脆性破损行为和破损区内岩体力学性质发生改变的工程事实,并认为岩体破损劣化过程是岩体力学参数降低的过程,提出考虑高地应力硬岩地层中开挖扰动下围岩劣化的硬岩本构模型。该模型的应力–应变关系具有明显的线弹性段、应力跌落段和塑性流动段,其后继屈服面具有随等效塑性应变发生形状和面积改变的特点,可以实现岩体累积损伤过程中力学参数(弹性模量E、黏聚力c、内摩擦角?)动态劣化,并可以与目前较广泛使用的岩土工程软件FLAC3D相结合。室内花岗岩三轴压缩试验曲线的拟合和锦屏二级水电站厂房探洞开挖破损区的模拟验证,都说明该模型的正确性和可推广性。

In the practice of tunneling in hard rock stratum under high geostress,mostly,two phenomena can be observed：（1） the rock has the activity of brittle breakage induced by the unloading;and（2） the parameters of surrounding rock in the excavation damage zone（EDZ） have changed,including elastic modulus E,cohesion c and friction angle φ.Therefore,a rock mass deterioration model（RDM） is presented.The RDM takes the damage of rock as a process of propagation of microcracks.It means that the microcracks lead to the reduction in deformation modulus and cohesion and the increase of friction angle in the EDZ.The relationship between mechanical parameters and damage degree represented by general plastic strain of EDZ is established.Then,the model defines an equation which is the function of general plastic strain to rule the change trend of parameters.It is implemented by integrating with the FLAC^3D.The model has three basic characters,i.e.the stress-strain curve is composed of linear elastic part,stress falling part and plastic flow part;the subsequent yield surface can change its shape and area along with accumulation of general plastic strain;and the mechanical parameters are updated with the deteriorating of surrounding rock in EDZ.This model is verified by fitting stress-strain curve of granite in triaxial compression test and modeling experimental tunnel at Jinping II Hydropower Station in China.The results indicated that the RDM is reasonable.