Shaking table test of utility tunnel under non-uniform earthquake wave excitation

Abstract

A series of shaking table tests were conducted on scaled utility tunnel models with and without construction joints under non-uniform input earthquake wave excitation. Details of experimental setup are first presented with particular focuses on: design and fabrication of double-axis laminar shear box with a rectangular hole opened on its side walls; design of two devices for measuring the slippage between the interface of test soil and the structure, and the relative deformation and rotation between joints of the structure model; and procedure for construction of input earthquake wave. The experiments were conducted in three phases. Phase 1 is free-field test. A 2-norm index is suggested to quantify the boundary effect and it is found that the designed laminar box does not impose significant boundary effect. Phases 2 and 3 are model tests in longitudinal and transversal directions, respectively. Test results are discussed in items of shear force–slip relationship at the soil–model structure interaction surface, movement and rotation of the construction joint, and effect of non-uniform earthquake input. The comparison shows that structural response under non-uniform earthquake excitation is larger than that under uniform excitation. The effect of spatial distribution of earthquake excitation should be considered in the seismic design of utility tunnel.