富含孔隙/裂隙岩体的非线性变形对于工程的安全评价具有重要意义.在多物理场耦合分析求解器TOUGHFLAC3D中实现双应变胡克模型(two-part Hooke's model,简称TPHM)的数值解法,并界定TPHM的适用条件.TPHM假设:对于岩体中可承受较大变形的软体(如孔隙、裂隙等),用基于自然应变(或真应变,即岩体变形与当前应力状态下的岩体体积之比)的胡克定律来描述；而对于只承受较小变形的硬体部分用基于工程应变(岩体变形与原始应力状态下的岩体体积之比)的胡克定律来描述.通过对室内岩样的应力-应变特征计算分析,表明TPHM在本质上反映了加卸载过程中低应力阶段的非线性变形行为,该力学响应完全取决于孔隙/裂隙的自然应变(真应变)；通过对瑞士Mont Terri岩石实验室的深部ED-B巷道围岩的变形场计算分析,显示出TPHM较为准确地反映了开挖卸载诱发的围岩变形特征.因为TPHM本质上是考虑了低应力状态下孔隙/裂隙对岩石力学性质的影响,因此,在具有卸荷扰动特征的岩石工程中应用TPHM模型进行设计分析更符合实际.%The nonlinear behavior plays an important role in the stability of rock engineering. As an attempt to more accurately model the elastic response of porous or fractured rocks, a recently developed stress-strain relationship, called two-part Hooke's model(TPHM), is incorporated into a coupled reservoir-geomechanical simulator, TOUGH-FLAC3D code. TPHM is based on a macroscopic approximation that the natural strain (volume change divided by rock volume at the current stress state), rather than the engineering strain(volume change divided by the unstressed rock volume), should be used in Hooke's law for accurate modeling of the elastic deformation except when mechanical deformation is very small. We first implement TPHM into a modified Mohr-Coulomb model providing by FLAC3D to demonstrate the numerical algorithm of TPHM in a geomechanical simulator. Then the nonlinear deformation behavior characterized by a shallow sloping stress-strain curve at low stress levels is numerically obtained with rock specimens under loading and unloading processes. Finally, based on the numerical simulation on the deformation of rock mass around an underground tunnel ED-B in Mont Terri laboratory, we show the usefulness of TPHM in light of its applicability to practical problems, and the importance of incorporating more accurate constitutive models for modeling mechanical response for field-scale problems related to rock engineering with unloading process.
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