不同开挖方式对近距离交叠隧道影响模拟研究

NUMERICAL SIMULATION FOR INFLUENCE LAW OF DIFFERENT EXCAVATION METHODS ON ADJACENT OVERLAPPING TUNNELS

研究不同开挖方式对近距离交叠隧道的地层和围岩的影响,揭示不同开挖方式下交叠区围岩及既有隧道衬砌的变形及应力–应变变化规律,为近距离交叠地下工程的变形控制、支护设计和开挖优化设计提供理论依据。通过FLAC3D数值模拟,研究在台阶法、眼镜法、CRD法3种不同开挖方式下交叠区围岩及既有隧道衬砌的变形及应力–应变发展规律、交叠区围岩塑性破坏规律,研究结果如下:(1)不同开挖方式对交叠隧道施工过程中不同位置的影响程度不同,揭示既有隧道衬砌变形机制演变过程和衬砌破坏的危险点;(2)根据围岩塑性区发展和隧道衬砌变形量,开挖下部新线隧道时CRD法优于眼镜法和台阶法,CRD法开挖下部隧道时对变形控制效果最好;(3)新建隧道穿越既有隧道时,比较理想的施工方案为台阶法→CRD法→台阶法;(4)任何开挖施工方法都会使已建隧道衬砌的4个部位(拱顶、拱脚、直墙边及拱底)承受拉应力,且拱脚处的最大、最小主应力最大,最易发生破坏。

The influence of different excavation methods on strata and surrounding rocks of adjacent overlapping tunnels is studied;and the stress-strain laws and deformations of overlapping surrounding rocks and current tunnel linings are revealed,which provides a theoretical basis for the deformation control,support design and excavation optimization design of adjacent overlapping underground projects. Through the FLAC3D numerical simulation,the stress-strain laws and deformations of overlapping surrounding rocks and current tunnel linings and the plastic failure law of overlapping surrounding rocks under the bench method,CRD method and glass method are studied. The research results are as follows：（1） Different excavation methods have different effect degrees on excavation positions during the construction of overlapping tunnels,which reveals the deformation mechanism of current tunnel linings and the dangerous points of lining destruction. （2） According to the development of plastic zone of surrounding rock and tunnel lining deformation,we can obtain that the CRD method is better than glass method and bench method when new line tunnels are excavated;and the deformation control effect of tunnel bottom excavated with CRD method is the best. （3） The bench-CRD-bench method is the ideal scheme when new tunnels cross current tunnels. （4） With any excavation method,the tensile stress will be caused in vaults,skewbacks, straight sides and bottoms of current tunnel linings. Both the maximum and minimum principal stresses in the skewback are the maximum;and the skewback is most easily damaged.