INFLUENCE OF LATERAL PRESSURE LOSS ON THE FORCE AND DEFORMATION OF SHIELD TUNNEL IN SOFT SOIL AREA

To study the problem that construction activities adjacent to metro tunnels in soft soil area could lead to increasement of segment deformation, a combination approach of model test and finite element simulation is adopted to study the force and deformation of shield tunnel structure at both elastic stage and plastic stage induced by lateral pressure loss. The results showed that:when the lateral pressure loss of shield tunnel is small, the segment deformation increases linearly, shield tunnel structure is still at elastic stage; when the lateral pressure loss becomes large, the segment deformation increases exponentially, and the shield tunnel structure changes into the range of plasticity. Increasing the thickness of segment can effectively improve the anti-deformation capacity of shield tunnel, but the improvement will become less effective with the increasement of segment thickness. From the perspective of structural eccentric loading state, increasing the thickness of segment will change the stress state from small eccentric compressive state into large eccentric compressive state. However, from the perspective of structural stress and strain, the maximum strain of segment will decrease, which makes the shield tunnel structure a more secure state of stress.