Liquefaction potential of sand deposits under low levels of excitation
Many researchers currently believe that liquefaction will not occur at a site unless the ground surface accelerations exceed some value between about 0.05g and 0.1g. It seems probable however, that levels of earthquake shaking significantly less than this value have induced liquefaction in the past. In addition, it also seems likely that non-seismic sources of low level vibration such as trains have caused several large scale liquefaction failures over the last forty years. Therefore, the aims of this investigation were as follows: (1) to determine whether train induced ground vibrations might be capable of inducing liquefaction, and (2) to determine the minimum level of earthquake shaking required to liquefy sand deposits in-situ. Train-induced ground motions were recorded at 4 different sites. These records show that trains appear to be capable of generating peak ground surface accelerations significantly in excess of 0.10g at distances closer than about 6 meters from the tracks. The liquefaction potential of sand sites shaken by trains is evaluated by following both the shear strain and the shear stress approaches. It is found that while trains are probably incapable of liquefying the sands underlying level sites, they appear to be capable of triggering liquefaction in sloping deposits under some conditions. On the basis of available data and analytical techniques, the minimum level of earthquake shaking required to cause liquefaction is shown to be heavily dependent on the magnitudes of both the initial static shear stresses, and any artesian pore pressures, present within the deposit. As the magnitudes of the initial shear stress/normal stress ratios increase, the level of shaking required to liquefy loose sand sites becomes extremely low.
- Research Organization:
- California Univ., Berkeley, CA (USA)
- OSTI ID:
- 6324270
- Resource Relation:
- Other Information: Thesis (Ph.D)
- Country of Publication:
- United States
- Language:
- English
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