Dynamic Response Analysis Of The Soil-metro Tunnels Interactions In Ground Fissures Area Under Vibration Loads Of Train

At present, with the faster speed of Metro construction in Xi’an, subway lines1&2have been running successively. Subway line3has been in construction and is scheduled toopen to traffic in2015. What’s more, subway line4is under preparation. For these, a seriesof new issues on ground fissure study come out, such as: What are some ofthe characteristics of dynamic response between surrounding rock nearby the groundfissures and Metro Tunnels under vibration loads of train? Will continuous cyclic dynamicload cause the ground fissure to be active again? Then does it affect the safety of metrotunnel? What role ground fissures play in the train dynamic load transmission? All thesetopics are the problems to be settled urgently in the construction of urban subway in the bigcity with the development of ground fissures and also one of the key scientific problems ofurban underground engineering research.Based on the national natural science foundation of China called Study on the soil-metro tunnels interactions in ground fissures area under dynamic load of metro, taking thesubway crossing ground fissure in Xi’an as the research background, with the researchobject of dynamic response of the soil-metro tunnels interactions in ground fissures areaunder vibration loads of train, using many methods including model test, numericalsimulation and theoretical analysis, dynamic characteristics on the soil-metro tunnelsinteractions in ground fissures area under vibration loads of train are studiedsystematically in this thesis..According to similar principle, model test on dynamic response of the soil-metrotunnels interactions in ground fissures area under vibration loads of train has been done forthe first time. The experimental results show that the strength in the joint of segmentedtunnel is less with weaker constraint function and the length of each tunnel section is smaller.Under the effect of the vibration excitation, vibration responses at the bottom and on the topof segmented tunnel are stronger than integral tunnel. There is not dropping for segmentedtunnel on the hanging wall of the ground fissure, namely no gap at the bottom of the tunnel.And soil pressure of surrounding rock is similar as the integral tunnel. However, with the movement of the ground fissure and the decrease of hanging wall, the gap came. The addedvalue of the earth pressure of the segmented tunnel is large different from that of integraltunnel. For integral tunnel, soil pressure is lower after the decline of the stratum; forsegmented tunnel, especially tunnel with three segments, soil pressure is larger. After thedescend of the hanging wall of the stratum, relatively static soil pressure belonging to soilpressure in the hanging wall and footwall is reduced, with less decline of soil pressure onthe footwall and larger decline on the hanging wall. At the same time, the change near theground fissure on the hanging wall is smaller while the decline of soil pressure far awayfrom ground fissure is largest. Compared with axial strain of segmented tunnel, the strainlaw of integral tunnel is better with flat curve. The curve of sectional tunnel fluctuated larger,and the strain value of sectional tunnel is bigger than integral tunnel. Therefore segmentcause the more the vibration response area. And under the activity of ground fissure, boththe vibration response of tunnel lining and soil pressure increased. In this thesis the advicefor tunnel across ground fissures is that segmented design use as less as possible.