Assessment of the loading waveform on the cyclic liquefaction resistance with Hostun 31 sand

Abstract

This paper was aimed at highlighting the impact of loading waveforms on the cyclic liquefaction resistance of sand. The test specimens were reclaimed by the dry tamping method with Hostun 31 sand, and the density of sand matrix was controlled to be 0.70. Three sets of undrained cyclic triaxial tests were performed by altering the loading waveforms as follows: triangular, sine and rectangular waves. The impact of the loading waveform was experimentally observed as axial cyclic stress was applied. Under the same amplitude of loading, it was found that the rectangular wave led to the most severe liquefaction as a result of greater imposed force acting for a longer duration. The triangular wave led to the lowest liquefaction softening, and the sine wave was the case in between. Consequently, in terms of the cyclic strength curves, diverse curves related to the imposed waveform were observed, and the curve for rectangular wave was located in the lowest part of the graph, thereby reconfirming its higher liquefaction potential. An in-depth analysis of the dynamic properties suggested that the development of the damping ratio with the progression of shearing is intrinsic for a given sand fabric under a certain initial confining stress. A unique relationship between the damping ratio and the amplitude of shear strain could be roughly established. However, the number of cycles required to trigger a certain level of shear strain remained a function of the amplitude and waveform. A novel parameter was proposed in this paper on the basis of the Arias intensity in order to unify the sand liquefaction response. Compared with the conventional method, one of its advantages is its ability to express the combined influence of the amplitude and waveform through a time-integral for a given imposed loading.