Model test study on effective ratio of segment transverse bending rigidity of shield tunnel

Abstract

The effective ratio of the transverse bending rigidity has an important influence on internal force of segmental ring, and that is an important parameter in shield segment design with average uniform rigidity ring. Based on tensile tests and similarity theory (at the joint area, similarity relation is achieved from the model tunnel which has the same rigidity ratios with the prototype tunnel), three kinds of segmental ring test models made of PMMA (to simulate segment) and aluminum welding wire (to simulate bolt) are used to carry out the model test, which include straight-jointed ring, stagger-jointed ring and uniform ring. Through changing the number of spring gaskets, the different bolt pre-tightening forces of straight-jointed and stagger-jointed ring are obtained. The multi-stage loading test on straight-jointed ring, stagger-jointed ring and uniform ring under different bolt pre-tightening forces are carried out with a homemade loading device. The variation values of horizontal and vertical diameter of straight-jointed and stagger-jointed ring are compared respectively, and then it is concluded that the range of the effective ratio of the transverse bending rigidity value is between 0.09 and 0.23 under straight-jointed condition, 0.30 and 0.80 under stagger-jointed condition. The contrast analysis on the effective ratio of the transverse bending rigidity values under different load levels with different bolt pre-tightening forces and different assembly modes shows that value of the stagger-jointed segmental ring is obviously lager than that of the straight-jointed segmental ring, and that difference decrease gradually with the load increasing.