STRESS ANALYSIS AND SEGMENT REINFORCEMENT OF OVERLAPPING SHIELD TUNNELS

In the construction of modern urban rail transit, more and more overlapping subway shield tunnels are used. The overlapping shield tunnels are interacted with each other. The collapse arch of overlapping tunnels is multiple superposed during digging. The traditional analytical method is difficult to calculate the pressure of tunnel surrounding rock. At present, there is no effective way to calculate the stress of overlapping tunnel surrounding rock. In order to study the stress and the segments reinforcement of overlapping shield tunnels, this paper takes the overlapping shield tunnels in Nanluoguxiang station to Dongsi station of Beijing Metro Line 6 as an example. The arch collapse multiple superposed is calculated by simulation of tunnels excavation process using the elastic-plastic theory. The plastic zone area of the tunnels is calculated using the strength reduction method. Then the collapse arch height and surrounding rock pressure are calculated from the plastic zone area. According to the theory of thick wall cylinder, the additional stress of the lower tunnel by shell in construction and by train in running is calculated. From above analysis, the internal force of overlapping shield tunnels is calculated and the segments reinforcement of lower shield tunnel segment is designed.