Influence of plastic fines content on the liquefaction susceptibility of sands: monotonic loading

The paper presents an experimental study on the effect of plastic fines content on the undrained behavior and liquefaction susceptibility of sand–fines mixtures under monotonic loading. The results of undrained monotonic triaxial compression tests conducted on mixtures of Hostun sand with varying amount (0–20%) and type (kaolin and calcigel bentonite) of plastic fines are presented. The specimens were prepared with different initial densities using the moist tamping method and consolidated at two different isotropic effective stresses. The results demonstrate that for both types of plastic fines, an increase in the fines content leads to a more contractive response and lower values of mobilized deviatoric stress. Despite similar relative density and fines content, the sand–kaolin mixtures showed a more contractive behavior than the sand–calcigel specimens. The steady-state lines (SSLs) in e–p´ space generally move downwards with increasing clay content. While the slopes of the SSLs for the clean Hostun sand and the mixtures with 10 and 20% kaolin are quite similar, the SSL lines for the specimens containing 10% or 20% calcigel run steeper or flatter, respectively. The inclination of the SSL in the q–p′ plane was found independent of clay type and content. The sand–kaolin mixtures were observed to be more susceptible to instability and flow liquefaction than the sand–calcigel mixtures.

Seismic Liquefaction Risk Assessment of Critical Facilities in Kathmandu Valley, Nepal

Kathmandu Valley lies in an active tectonic zone, meaning that earthquakes are common in the region. The most recent was the Gorkha Nepal earthquake, measuring 7.8 Mw. Past earthquakes caused soil liquefaction in the valley with severe damages and destruction of existing critical infrastructures. As for such infrastructures, the road network, health facilities, schools and airports are considered. This paper presents a liquefaction susceptibility map. This map was obtained by computing the liquefaction potential index (LPI) for several boreholes with SPT measurements and clustering the areas with similar values of LPI. Moreover, the locations of existing critical infrastructures were reported on this risk map. Therefore, we noted that 42% of the road network and 16% of the airport area are in zones of very high liquefaction susceptibility, while 60%, 54%, and 64% of health facilities, schools and colleges are in very high liquefaction zones, respectively. This indicates that most of the critical facilities in the valley are at serious risk of liquefaction during a major earthquake and therefore should be retrofitted for their proper functioning during such disasters.

Predicting Probability of Liquefaction Susceptibility based on a wide range of CPT data

In the present study, three efficient soft computing techniques i.e. GP, RVM, and MARS are utilized to predict the probabilistic liquefaction susceptibility of soils based on reliability analysis. For this, a sum of 253 Cone Penetration Test (CPT) data of nineteen major earthquakes occurred between 1964 and 2011 has been collected from the literature. Six liquefaction parameters such as corrected cone penetration resistance, total vertical stress, total effective stress, maximum horizontal acceleration, magnitude moment, and depth of penetration. To evaluate the overall performance of the proposed models, rank analysis has been carried out. Based on the values of performance indices, the GP model outperforms the other two models in terms of RMSE=0.15, R2 =0.77, and VAF=76.86 in the training stage while the same has been found 0.14, 0.81, and 80.46 in the testing phase. Also, the Rank Analysis confirms the superiority of the GP model in predicting the probability of liquefaction susceptibility of soils at all stages.