Investigation on the Liquefaction of a Clayey-Sandy Soil During Changureh Earthquake

An intense earthquake (MW = 6.4) occurred in western Iran, about 225 km west of Tehran at 7:28 local time, June 22, 2002. Surface soil in this area is mostly clay; however, clear traces of sand boiling, softening of soil, and consequent deformations were observed particularly in Hessar village. Some soil samples were prepared throughout an excavated pit from a depth of 2 m, the depth of the liquefied layer. The preliminary tests showed that the soil has a liquid limit of 38, a plasticity index of 18, and a \u3c No. 200 fraction of 44%. These index characteristics would indicate a nonliquefiable soil according to the commonly used criteria. Analysis of cyclic triaxial test data suggests that the clayey sand deposit likely developed high residual excess pore pressures and significant shear strains during the earthquake and thus likely contributed to the observed lateral deformations. In this paper, different cases of observed liquefaction and consequent geotechnical phenomena are presented. Moreover, the results of laboratory tests on reconstituted samples are presented to prove how a soil with 44% of clay content could be liquefied

Nonlinear Time Domain Numerical Model for Pile Group Under Transient Dynamic Forces

A computational model of soil-pile interaction behavior in pile and pile group was developed in this paper. Particular attention was paid to making the model simple and capable of taking into account nonlinear soil behavior, such as gapping and slippage between soil and pile, and cyclic behavior of soil. The model was developed within the frame work of the Winkler model defined in plane strain conditions. In order to analyze transient dynamic response in a rigorous manner, the model was formulated in the time domain using a step-by-step method. A transfer matrix approach was also adopted in the response computation. The proposed nonlinear model was verified with rigorous solutions and the nonlinear behavior with gapping and slippage were discussed based on the computational results

Effect of surface layer freeze to soil-pile interaction

To assess earthquake resistance of new or existing structures and predict earthquake damage of structures, it is important to properly evaluate the response of the structure at the time of the earthquake. In cold regions however, where the ground can freeze in winter, the dynamic soil-foundation interaction can change with the change in the density and stiffness of the frozen side soil. This paper examines in a quantitative manner, the influence of freezing of ground on the dynamic soil grouped piles interaction., It is shown herein that the grouped piles in the frozen ground tend to follow the motion of the ground over a wider range of frequency. Furthermore, it is shown that even when the freezing depth is much thinner than the characteristic length of piles determined by the stiffness ratio of the ground and the group pile, the pile cap stiffness at the time of freezing becomes noticeably large. It is confirmed that the freezing of the ground can greatly affect the interaction between the ground and the piles

Assessment of earthquake-triggered landslide susceptibility considering coseismic ground deformation

The distance to the surface rupture zone has been commonly regarded as an important influencing factor in the evaluation of earthquake-triggered landslide susceptibility. However, the obvious surface rupture zones usually do not occur in some buried-fault earthquake cases, which means information about the distance to the surface rupture is lacking. In this study, a new influencing factor named coseismic ground deformation was added to remedy this shortcoming. The Mid-Niigata prefecture earthquake was regarded as the study case. To select a more suitable model for generating the landslide susceptibility map, three commonly used models named logistic regression (LR), artificial neural network (ANN), and support vector machine (SVM) were also conducted to assess landslide susceptibility. The performances of these three models were evaluated with the receiver operating characteristic curve. The calculated results showed that the ANN model has the highest area under the curve (AUC) value of 0.82. As the earthquake triggered more landslides in the epicenter area, which makes it more prone to landslides in further earthquakes, the susceptibility analysis at two different mapping scales (the whole study area and the epicenter area) was also applied

A Method and its Problems for Numerical Analysis of Rapid and Long-Traveling Soil Flows

特集2 耐震構造学研究グループ (ERS

2003年12月26日バム地震によって亀裂電柱に残留したひずみと家屋被害

The Bam earthquake of December 26, 2003 (Mw6.5) occurred around the city of Bam in southeast Iran. Because the earthquake happened early in the morning at 01: 56: 56 (GMT, 05: 26: 26 local time), most of the reported 43,100 victims were killed in their dwellings. In Iran, there are dense strong ground motion networks for describing the seismological features of earthquakes, but very sparse networks for damage distribution analysis. Actually, damage differed from street block to street block, and only one seismometer was available in the city. Measuring traces of intense shakes remaining in structures, which are seen everywhere and have common features, can be very effective. The authors used utility poles in Bam for this structure. This report provides a spatial distribution of strains induced in these poles, and compares them with damage distribution in the city