基于单元重构的岩土工程复杂地质断层建模方法

 针对岩土工程数值分析中地质断层建模困难的问题，提出基于单元重构的岩土工程复杂地质断层建模方法。该方法首先对分析对象进行独立离散，建立不考虑地质断层的模型。再通过单元重构，可将地质断层嵌入已建模型，实现复杂地质断层的自动建模。所谓单元重构，是首先使用八节点六面体单元，建立不考虑断层的分析模型，再借助四节点四面体，五节点四棱锥和六节点三棱柱等单元形态，对地质断层穿过的网格进行处理，重构为由多种单元形态构成的模型。然后结合岩土工程断层建模实例，将该方法应用于复杂地下岔管、重力坝坝肩和坝基以及大型地下洞室群的断层建模，可证明其有效性。进一步以大型地下洞室群为例，将考虑地质断层的洞室群模型导入通用软件，采用实体单元模拟地质断层进行开挖计算，并与不考虑断层的情形对比分析发现，考虑地质断层后，围岩位移和应力分布都呈现出不连续性，被断层切割部位的围岩变形增大，应力出现松弛。这表明含有地质断层的重构模型可以用于数值计算，且能有效反映出地质断层对洞室围岩稳定的影响，从而可证明该建模方法的可靠性，为岩土工程的复杂地质断层建模提供便捷的实现途径。

METHODOLOGY FOR MODELING OF COMPLEX GEOLOGICAL FAULTS IN GEOTECHNICAL ENGINEERING BASED ON ELEMENT RECONSTRUCTION

The modeling of geological faults is a difficult issue in the numerical analysis of geotechnical engineering. The methodology for modeling of complex geological faults is proposed by using element reconstruction. This method firstly discretizes the analysis objects without taking geological faults into consideration. Then，by conducting element reconstruction，the geological faults can be constructed into the model. The element reconstruction is to establish fault-free models by using eight-node hexahedron element at first. Afterwards，by using four-node tetrahedron，five-node rectangular pyramid and six-node triangular prism，the meshes that are intersected by structural planes can be reconstructed and the fault-contained model is obtained. And the fault-contained model has multi-form elements. Then，the proposed method is illustrated with its applications to several geotechnical examples，including the modeling of geological faults in complex underground bifurcation pipe，abutment and foundation of gravity dam and large-scale underground caverns. These applications prove the effectiveness of proposed method. The numerical analysis is further conducted by taking underground caverns as an example. By using common software，the excavation simulation is performed on the fault-free model and fault-contained model of underground caverns，respectively. The elements of geological faults in fault-contained model are directly simulated by entity elements. By comparing the results of different models，it is discovered that the distributions of surrounding rock deformation and stress show a remarkable discontinuous feature in the fault-contained model. The surrounding rock intersected by geological faults observes an increase of displacement and a release of stress. This indicates that the meshes generated by the proposed modeling method can be used in numerical analysis and influences of geological faults on surrounding rock stability can be properly reflected as well. Thus，the reliability of proposed method is demonstrated，providing the modeling of complex geological faults in geotechnical engineering with a convenient way.