饱和过程中黏土岩变形和水化膨胀特性研究

Deformation and hydration swelling characteristics of clay rock during saturation

在原位状态下,黏土岩呈现饱和状态,而在实际实验室研究中,由于钻孔取芯、运输、储存和加工等因素的影响,黏土岩已经失水并呈现非饱和状态。因此,在试验测试前将黏土岩尽量恢复至原位饱和状态是进一步试验测试的重要前提。本文以黏土岩为研究对象,通过无外力作用的黏土岩饱水试验及原位应力下的饱和试验,重点研究饱和过程中黏土岩的变形规律及水化膨胀特性。试验研究表明:无外力作用下,含中心圆孔黏土岩由于饱水过程中黏土矿物的水化膨胀、崩解、混和堆积逐步充填原有的孔洞;在原位应力作用下,水溶液作用仍使黏土岩内部黏土矿物快速水化膨胀,宏观上表现为试样体积迅速膨胀的同时孔隙度显著增大,且膨胀变形量与试样初始饱和度呈现负相关;在试验研究基础上,基于Comsol Multiphysics多场耦合有限元软件中的流体流动模块,建立黏土岩渗流-应力耦合数学模型,进行原位应力下黏土岩饱和过程的数值仿真,重点分析饱和过程中黏土岩试样内部孔隙水压力及饱和度随时间的演化规律;探讨饱和过程中黏土岩的孔压系数B值,并进一步分析加载步骤对黏土岩饱和过程的影响。研究结果将对黏土岩等岩石物理力学特性的相关研究提供试验指导及理论依据。

In the in-situ state,the clay rock is saturated,but in the actual laboratory study,the clay rock has lost water and is unsaturated due to the influence of drilling core,transportation,storage,and processing.Therefore,restoring the clay rock to the in-situ saturation state as far as possible before the further experimental test is an important prerequisite for further experimental tests.This paper takes clay rock as the research object,through the clay rock saturation test without external force and the saturation test under in-situ stress,the focus is on the hydration expansion properties of clay rock and the deformation law in the process of saturation from a macro and mesoscopic perspective.The research shows that with different water saturation time,under the action of no external force,the claystone with central circular pores gradually fills the original pores due to the expansion,disintegration and mixed accumulation of clay minerals.Under the in-situ stress,the action of brine still causes the rapid hydration and expansion of the clay minerals in the clay rock,and the macroscopic appearance of the sample volume increases rapidly while the porosity increases significantly.The expansion deformation is negatively correlated with the initial saturation of the sample.Further,based on the Comsol Multiphysics multi-field coupled finite element,the fluid flow module in the software establishes the geometric model of the clay rock sample and carries out the numerical simulation of the saturation process of the clay rock.Finally,pore pressure coefficient B during saturation and the effect of loading steps on the clay rock saturation process are discussed.The research results will provide experimental guidance and theoretical basis for the related research on the physio-mechanical properties of clay rocks and other rocks.