Reply to the two discussions on my paper "An alternative mechanism of pile failure in liquefiable deposits during earthquakes"
This paper proposes an alternative mechanism of pile failure in liquefiable deposits during earthquakes. This failure mechanism, based on pile buckling, is formulated by back-analysing 14 case histories of pile foundation performance during earthquakes and verified using dynamic centrifuge tests. A new parameter, the slenderness ratio of a pile, is introduced to classify pile performance in liquefiable soils. This parameter fits very well both the reported case histories and the centrifuge test results.
INFLUENCE OF LIQUEFACTION ON PILE-SOIL INTERACTION IN VERTICAL VIBRATION
During strong earthquake shaking, loose cohesionless soils below the water table develop high pore water pressures and liquefy leading to significant degradation of strength and stiffness. In such soil stratum, pile foundations may undergo substantial shaking while the soil is in a fully liquefied state and soil stiffness is at its minimum. In this paper, an available numerical model formulating the pore pressure response directly from observed data on undrained tests has been used to study the liquefaction phenomenon. The Winkler soil model has been used to model the pile-soil interaction. Combining these two models, a formulation to predict the response of a pile in liquefiable soils in axial vibration is developed. It is observed that the response of a single pile due to axial vibration in liquefiable soil is significantly greater than that in non-liquefiable soil, particularly at higher frequencies.
Centrifuge modelling of effects of shield tunnels on existing tunnels in soft clay
With the rapid development of the subway network,the phenomena of shield tunnels going across the adjacent tunnels are becoming more and more common.The interaction between shield tunneling and nearby tunnels is more complicated than the ordinary shield tunneling in intact soil strata.Based on the project of Shanghai Bund Passage crossing Metro Line 2,the method of centrifuge modeling together with the field measurement is employed to study the effects shield tunneling on nearby strata and existing tunnels.In centrifugal model tests,the effects simulation techniques considering the unloading of excavation,ground loss and grouting are developed to analyze the longitudinal settlement of the shield tunnel and the existing tunnel induced by the shield tunneling.Besides,the deformation distribution and settlement curves of the existing tunnels during shield construction are studied by using the monitoring data.