Numerical Simulation and Comparison of Geostress Distribution under the Influence of Complex Geological Conditions in a Deep Buried Tunnel in Tianshan
The burial depth,lithology,and geological structure affect the spatial distribution characteristics of geostress.Under complex geological conditions,in-situ stress does not always increase linearly with depth and is affected by changes in lithology and ge-ological structure.Taking a tunnel with a maximum depth of 2 268 m in the Tianshan Mountains as an example,based on site surveys and measurement data,the finite difference software FLAC3D was used for three-dimensional numerical simulation in an area of about 460 km2.Results show a clear impact on abnormal varations of in-situ stress due to geological structures.There is a 5~10 MPa differ-ence in the fluctuation of in-situ stress caused by sudden changes as folds on both sides of the fault,especially the local concentration of in-situ stress near the hanging wall of the fault.Such kind of concentration mostly contributes to the occurrence of rockburst once ex-cavating at sections of hard rocks.Compared with the measured in-situ stress results at nearby locations,the numerical calculation re-sults are 20~30 MPa larger,indicating a significant change in in-situ stress values due to the development of geological structures,which is also a location that the in-situ stress measurement points are trying to avoid in practice.The research results connecting simu-lation with measurement are expected to provide reference for similar projects in this area.