高围压下高孔隙水压对岩石蠕变特性的影响

为研究高应力作用下深部岩体开挖过程中孔隙水压对围岩时效变形特性的影响,选取重庆某深部细砂岩为研究对象,对其进行不同水压下分级加载蠕变试验,试验表明:孔隙水压增强了砂岩的变形能力,但随着水压的升高,加载初期的一段时间内,水压在一定程度上会延缓轴向变形;蠕变过程中黏弹性模量随时间呈指数函数变化,通过分析不同水压作用下指数函数中参数的变化规律,得到黏弹性模量随时间和水压变化的表达式,进而提出修正的广义Kelvin模型,该模型能较好的描述不同水压作用下岩石的非线性黏弹性蠕变特性。基于不同水压下加速蠕变试验曲线特征,采用拟合、类比的方法引入一个能反映不同水压作用时加速蠕变特征的二元件黏塑性模型,将该模型与修正的广义Kelvin模型串联组成一个新的非线性黏弹塑性蠕变模型。基于试验结果,利用优化分析软件1stOpt,对模型参数进行辨识,效果比较理想;对比试验曲线和理论曲线,二者吻合较好,验证了模型的正确性。

Influence of high pore water pressure on creep properties of rock under high confining pressure

In order to study the influence of water pore pressure on time-dependent deformation of surrounding rock in the process of deep rock mass excavation under high stress，step loading triaxial creep test was carried out for deep sandstone from Chongqing under different pore water pressure.The results show that water pressure can enhance the performance of rock creep deformation，but with the increase of water pressure，the deformation of rock is restrained in some extent at the initial loading phase.During rock creep，viscoelastic modulus changes exponentially with time.By analysing the variation of exponential expression parameter at different water pressure，expression of viscoelastic modulus varid with time and water pressure was obtained，then，a revised modified Kelvin was proposed which is much better to discribe the nonlinear viscoelastic creep characteristic in different water pressure.Based on the action of fine sandstone accelerating creep curves at the level of different water pressure，a two component viscoplactic model was acquired by the method of fitting and anology，which is connected with the revised modified Kelvin model in series，then a new nonlinear viscoelastic-plastic constitutive model was gotten.According to test result，the optimize anglysis software 1stOpt was choosed to identify the model parameters，which has a quite ideal effect.The test curves are coincident well with the theoretic cruves，which verified the correctness of the model.