Experimental investigation on mechanical behavior of segmental joint under combined loading of compression-bending-shear

Abstract

The non-circular tunnels, for example the quasi-rectangular tunnel, may generate a considerable shear force at their shoulder joints owing to the geometry effect. To investigate the shear force effect on the mechanical behavior (e.g., capacity, deformation and duality) of the segment joint, a series of full-scale mechanical loading tests were conducted and reported in this paper. The loading scenarios include the combined axis force and moment scenario (N-M), and the combined axis force, moment and shear force (N-M-Q) scenario. Both the positive bending moment and negative bending moment are considered. DIC technique is also adopted to capture the detailed cracking process in the N-M-Q loading test. The test results reveal that the mechanical response of the segmental joint under both N-M and N-M-Q loading scenarios can be divided into three stages, which are separated by the initial joint opening and the initiation of cracks. The shear force would lead to a larger deformation (e.g., deflection, joint opening and rotational angle) before the failure but result in a brittle failure of the segment joint. Moreover, the shear force could reduce the moment bearing capacity under the positive moment loading condition while has little effect under the negative moment loading condition. These shear force effects are thought to be caused by the shear induced dislocation and inclined cracks.