Design and Commissioning of Continuous Soil Box Supported on Shake Tables Array for Testing Long Geostructures

Abstract

The seismic soil response and soil-buried infrastructure interaction are of immense importance for the resilience of urban centres. Shake table testing offers an efficient tool for modeling the seismic soil-structure interaction. This paper presents the design and commissioning of a suspended continuum soil box supported on an array of shake tables to enable simulating homogeneity and inhomogeneity of soil and non-uniform seismic excitation of extended buried structures such as pipelines and tunnels. The large-scale shaking table model involves a steel box 7.3 m × 1.4 m × 1.2 m supported by 3 shake tables. It comprises 3 active rigid boxes (2 end boxes and one middle box) supported on 3 shaking tables and 2 passive (suspended) soft joint boxes to provide continuous soil medium. The continuous box design is modular and allows its expansion to be supported by the available 9 shaking tables for even much longer soil continuum model. The developed test setup was used to investigate the seismic response of free-field soil to verify the performance of the soil continuum box. The sand test model was instrumented with arrays of accelerometers embedded along its height within both rigid and suspended boxes to evaluate the effect of the test setup on the ground motion characteristics in both segments. Dynamic performance of the continuum box is examined by comparing the results of shaking table tests on the box empty and box containing a sand model. The results demonstrat that the soil box did not experience resonance with the sand model, hence it did not affect its response to the shaking. A quantitative analysis is conducted to evaluate the box boundary effects on the soil seismic response in terms of the L2-norm, μ, the acceleration time history waveform and Fourier spectrum characteristics at soil surface and 0.7m below surface. The consistency of surface peak acceleration under different seismic excitations and intensity levels are compared in terms of standard deviation, β. The results demonstrat that the developed suspended continuum model box performed well and can simulate the continuity and boundary conditions of free-field.