Surabaya earthquake hazard soil assessment

The vulnerability of land in an area to earthquake ground motions is one of the factors causing damage caused by the earthquakes. The city of Surabaya, which is crossed by two active fault segments, needs an assessment to reduce the risk of being affected by an earthquake that might occur. The aims of this study are (1) to find out the distribution of Seismic Site Classes, (20 to know the distribution of the value of Seismic Amplification, and (3) to know the potential of liquefaction in the city of Surabaya. Surabaya city, which is geologically dominated by alluvium deposits, consists of soft soil (SE) and medium (SD) sites based on N-SPT30 and Vs30 data. The level of soil amplification against earthquakes ranging from 1 to 4. This occurs because the physical properties of the Surabaya City soil layer are dominated by alluvium deposits. Regions with more than 2 amplification values are located around the coastline on the North and East coasts of Surabaya City. Based on the potential liquefaction index value, Surabaya City is included in the region with a high potential for liquefaction with a potential liquefaction index value of more than 5.

Evaluation of Soil Liquefaction in Harbor District in Tianjin City

The liquefaction of soils in the harbor district in Tianjin City near Tangshan, where a great earthquake occurred is a very important issue related to the soil’s compaction, grain composition and content of clay particle. This problem has not been fully considered due to the complexity and uncertainty of the soil properties data, since none of the previous investigations has been concerned about the liquefaction characteristics of this new harbor district. The evaluation of soil liquefaction has been made based on related data of the standard penetration test (SPT) from 26 investigation bore holes and 105 sieving tests. The results show that the liquefaction index of silt sand gradually decreases with the increase of the buried depth; soils less than 10.6 m in depth are of bad gradation identically. Soil less than 10.6 m in depth can be defined as liquefied soil which is further verified by sieving tests. Both the buried depth and particle grading have primarily significant influences on silt sands’ liquefaction. The results from sieve tests based on liquefied soils were found to fit well with the Tsuchida curves. It is believed that even without the in-suit SPT tests, Tsuchida boundary curves can be directly utilized to judge the liquefaction of soils in the harbor district.

Resist Liquefaction of Subsoil of Metro and Improvement of Segments of Shield Tunneling

Nanjing’s metro is studied as a example to introduce resist liquefaction method in this paper. Dynamic diffuse theory of structure is supposed to evaluate the width and depth of foundation treatment to resist the seismic liquefaction to think of metro structure, liquefied soil layers and different liquefaction-index. High pressure jet grouting method is researched as shield machine construction through foundations of buildings or ancient wall. An improved segments of shield tunneling method is suggest to ensure the resist liquefaction method to success.

A genetic-algorithm approach for assessing the liquefaction potential of sandy soils

The determination of liquefaction potential is required to take into account a large number of parameters, which creates a complex nonlinear structure of the liquefaction phenomenon. The conventional methods rely on simple statistical and empirical relations or charts. However, they cannot characterise these complexities. Genetic algorithms are suited to solve these types of problems. A genetic algorithm-based model has been developed to determine the liquefaction potential by confirming Cone Penetration Test datasets derived from case studies of sandy soils. Software has been developed that uses genetic algorithms for the parameter selection and assessment of liquefaction potential. Then several estimation functions for the assessment of a Liquefaction Index have been generated from the dataset. The generated Liquefaction Index estimation functions were evaluated by assessing the training and test data. The suggested formulation estimates the liquefaction occurrence with significant accuracy. Besides, the parametric study on the liquefaction index curves shows a good relation with the physical behaviour. The total number of misestimated cases was only 7.8% for the proposed method, which is quite low when compared to another commonly used method.