Guidelines for Field Assessment of Liquefaction Hazard in Urban Areas Through Geophysical Methods

Abstract eng:
Liquefaction phenomena as an earthquake-induced effect in loose saturated soils is considered very dangerous for structures founded over such materials. Peru’s capital and its surrounding districts are located over alluvial deposits with a shallow water table, so it can be inferred that liquefaction potential is high. In addition, Peru’s capital is currently in a process of fast urban expansion which makes lots of people to settle in zones that are prone to liquefaction posing a risk to housing and infrastructure projects. The common practice for liquefaction potential assessment recommends field testing such as SPTbased and CPT-based methods although a more cost-effective method is the use of geophysical methods which are not destructive and faster. The latter suits the need of a developing country which lacks of enough funding for soil exploration using SPT or CPT. In recent years there have developed several methodologies to include geophysical parameters in liquefaction potential assessment. However, the reliability of such methodologies in places far from where they were developed must be tested in order to properly apply them. Therefore, this paper reviews geophysical-based correlations for liquefaction assessment aiming to perform a comparative analysis among them and SPT-based methods. Furthermore, the paper aims to establish guidelines for liquefaction hazard assessment in three levels of analysis starting from the qualitative one which shows the importance of geomorphological and geologic conditions, then it is important to evaluate past behavior of soils during earthquakes to finally estimate the factor of safety. Findings indicate that geophysical-based methods for assessing liquefaction potential have similar results to those obtained following SPT-based methods except in the range of soils with moderately stiffness (i.e. shear wave velocity is between 185 m/sec to 250 m/sec) whose liquefaction potential is difficult to predict.

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