A Study on Characteristics of Ground Motion in Permafrost Sites along the Qinghai-Tibet Railway

Abstract eng:
Based on field geological investigation at permafrost regions, geological description and test of waves velocities of the 14 typical drilling holes distributing permafrost areas along the Qinghai-Tibet railway, elementary characteristics of soil wave velocities at the permafrost regions are presented. And then, combining results of dynamic triaxiality test, using 3 time histories of ground motion acceleration with the exceedance probabilities (62.5%, 10% and 2%) related to this research area, characteristics of ground motion are analyzed for the 10 permafrost profiles by an equivalent linearization method to estimate the seismic response of frozen soil ground. Moreover, influence of earth temperature on seismic acceleration respond spectrum for permafrost sites is studied. Consequently, there are 4 results could be revealed as follows: 1) at the similar conditions, waves velocities of frozen soils along the Qinghai-Tibet railway are greater than other non-frozen soils areas, and velocity ratio between shear wave and compression wave does the same also; 2) earthquake strength is a critical factor to influence the acceleration amplitude of ground motion at permafrost regions, e.g. with the depressing of earthquake strength, acceleration amplitude of ground motion reduces gradually; 3) proportions of moderate and short period of seismic acceleration respond spectrum in permafrost regions are evidently greater than other non-frozen areas; and 4) amplitude of acceleration response spectrum of ground motion decreases distinctly while earth temperature of frozen soils reduces. As an expectation of authors, this paper should contribute to earthquake disaster prevention of the engineering structures in permafrost areas at Qinghai-Tibet Plateau.

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