Analysis Of Surrounding Rock Stress In The Of Construction Of Highway Tunnels With Small Spacing

China is a country with vast area and complex geological conditions, constructions of high-grade highway unavoidably meet with lots of runnel works. small spacing and special double-arch tunnel structure is often be used because of the tunnel spacing is generally difficult to meet the general requirements of technical in order to meet the needs of comfort and safety. Small spacing tunnel are highly accepted in recent years by civil engineers in present.This paper has done some research on the stress variations of surrounding rocks and the security of supporting system of JiuLing tunnel at the following aspects, of which the finite element method and field monitoring is adopted.(1) This paper has analyzed the analysis method of surround rock stress, included the ground initial stress, secondary stress after excavated, stress after supports as well as the stress analysis in bias condition.(2)Adjacent rocks, shotconcrete, bolt and second lining are simulated by plane42, beam3, link1 and beam3. Utilizing the DP (Drucker-Prager) surrender criterion, tunnel model in different adjacent rocks, constructing method and stage of construction procedure are built. And the same time, simply introduce method of excavate and unload. In carries on to the tunnel excavates and supports and protects the process in the simulation ANSYS simulates the material elimination and increases through kills and activation with the unit.(3) Simulation for different excavation methods in YK195 cross-section which is under the conditions of shallow and bias in JiuLing tunnel exit. Comparison and selection different process step of CRD method of the single-hole under the condition of shallow and bias, to simulate two different excavation process step of shallow tunnels with small spacing in bias conditions, to find the law of stress field changes in the excavation by the method of monitoring the key point; compared and analyzed the measured data and numerical simulation results.(4)The concept of NATM and the method of tunnel construction monitoring is discussed. Combination of Jiuling tunnel monitoring and controlling projects, analysised the actual monitoring data of two cross-section in grade IV and V surrounding, and compared and analysised with the numerical solution, has made the conclusions of been steel string sensor can be applied to measure the changes in the tunnel surrounding rock stress.Through above research, may obtain conclusion:(1) Arch foot, arch crown, rock pile is the most important part to be care in construction.(2)The behind tunnel excavation can effect the surrounding rock stress of the front tunnel. The effect degree is related with the rock grade and excavation method and Other Factors.(3) The different processes of bias tunnel with small spacing can impact the of stress distribution of surrounding, the final stress field is not symmetric, the stress in deep side is slightly larger than the stress in shallow side; the stress and displacement of first excavated tunnel is influenced by the later one.(4)By using bench excavation, the larger changes of the surrounding stress have taken place before and after the excavation and support of lower bench. moving away from the monitoring sections, the stress of surrounding rock are becoming more and more smooth.(5)The larger changes of the surrounding rock stress have taken place after secondary support has done.