轴压水压耦合作用下裂隙砂岩蠕变特性

在水利水电、水底隧道等岩土工程建设中，伴有初始损伤的岩石材料长期处于轴压水压耦合环境下，严重影响岩土工程的长期稳定性。为了保证处于轴压水压耦合环境下岩土工程的长期稳定性，以预加载制备的裂隙砂岩岩样为研究对象，利用特制的流固耦合多通道岩石流变系统，开展轴压水压耦合作用下裂隙砂岩单级加载蠕变实验及其蠕变模型研究，主要分析压力水与初始荷载对裂隙岩样蠕变特性的影响变化规律，并讨论新建立蠕变模型的准确性与合理性。蠕变实验研究结果表明：裂隙砂岩的轴向蠕变量随水压增大而减小；蠕变加速阶段的最大蠕变应变率随着水压升高而增大；初始阶段和破坏阶段的最大轴向蠕变应变率随初始荷载增大而增大。基于损伤理论，建立了考虑初始损伤的蠕变模型基本元件的非线性方程；根据幂函数方程，提出了新加速蠕变黏塑性模型；根据轴压水压耦合作用下裂隙砂岩的蠕变变形特征，建立了考虑时效损伤的一维非线性蠕变模型；基于增量理论，构建了轴压水压下考虑时效损伤的三维非线性蠕变模型。新蠕变模型预测的理论蠕变曲线与轴压水压下裂隙砂岩蠕变实验结果吻合度较高，这表明所建立的蠕变模型能较好的描述轴压水压耦合作用下裂隙岩石的蠕变变化特征，新蠕变模型合理，该成果为评价地应力与压力水耦合作用下岩土工程的长期稳定性提供理论依据。

Creep Characteristics of Fractured Sandstone Under the Coupling Action of Axial Compression and Hydraulic Pressure

In the construction of water conservancy, hydropower, underwater tunnels and other geotechnical engineering, rock materials with initial damage are under the coupling of axial pressure and hydraulic pressure for a long time, which seriously affects the long-term stability of geotechnical engineering. The fractured sandstone specimens obtained by preloading were taken as the research object in order to ensure the long-term stability of geotechnical engineering under the coupling of axial pressure and hydraulic pressure. The single-stage loading creep tests on the fractured sandstone under the coupling action between axial compression and hydraulic pressure and its creep model were investigated by using a special rock rheological system with multi-channel. The effects of both the hydraulic pressure and the initial load on creep properties were mainly analyzed. The accuracy and rationality of the constructed creep model was discussed. The results showed that the axial creep of fractured sandstone decreased with the increase of hydraulic pressure. The maximum creep strain rate in the acceleration phase of creep increased with hydraulic pressure increasing. The maximum axial creep strain rate in the initial and the failure stage increased with the initial load increasing. Based on the damage theory, the nonlinear equation of the basic components of the creep model considering initial damage was established. According to the power function equation, a new accelerated creep viscoplastic model was proposed. According to the creep properties of fractured sandstone under the coupling of axial pressure and hydraulic pressure, a one-dimensional nonlinear creep model considering aging damage was established. Based on the increment theory, a 3d nonlinear creep model considering aging damage under axial pressure was constructed. The new theory of creep models to predict creep curves was highly correlated with creep experimental results, which indicated that the established creep model considering the aging damage can better describe creep change characteristics of fractured rock under the coupling of axial presume and hydraulic pressure. It can provide a theoretical basis for evaluating the long-term stability of geotechnical engineering under the coupling of the in-situ stress and hydraulic pressure.