现代黄河水下三角洲砂土液化模式

根据实际勘探资料及室内土工试验结果，按极限平衡理论和线性波动理论等，分析了现代黄河水下三角洲砂土在地震和波浪动力因素的作用下发生液化的可能性，并根据其液化过程实质是孔隙水压力产生、发展和消散的过程，总结出砂土液化模式应包括四个阶段；（１）压密阶段：孔隙水压力升高至砂土本身强度，使颗粒产生相对位移；（２）初始液化阶段：孔隙水压力升至土层所受侧向压力，产生较大应变；（３）完全液化阶段：孔隙水压力升至土层上覆有效应力，产生喷水冒沙现象；（４）塌陷形成阶段：孔隙水压力消散。     

浙江北部岛屿海域土体稳定性研究

本文探讨了浙江北部岛屿区水道岸坡土体滑动的成因机制与滑坡的形态特征，对在波浪与重力共同作用下的边坡稳定性以及波浪底压引起的砂土液化进行了定量分析。研究表明，岛屿区水道中部与岸坡间强烈的冲淤反差，是该海域岸坡土体滑动不稳定因素积累的主要环境条件。目前发现的多数为中到大型的牵引式滑坡，主要由重力作用所致。对于波浪较大、水深较浅海域的粉砂、细砂分布区，浅表砂层存在着发生液化的可能性。     

Analysis of soil–pile–structure interaction in a two‐layer ground during earthquakes considering liquefaction

This study is conducted with a numerical method to investigate the seismic behaviour among certain soils, single piles, and a structure. A series of numerical simulations of the seismic behaviour of a single‐pile foundation constructed in a two‐layer ground is carried out. Various sandy soils, namely, dense sand, medium dense sand, reclaimed soil, and loose sand, are employed for the upper layer, while one type of clayey soil is used for the lower layer. The results reveal that when a structure is built in a non‐liquefiable ground, an amplification of the seismic waves is seen on the ground surface and in the upper structure, and large bending moments are generated at the pile heads. When a structure is built in a liquefiable ground, a de‐amplification of the seismic waves is seen on the ground surface and in the upper structure, and large bending moments are generated firstly at the pile heads and then in the lower segment at the boundary between the soil layers when liquefaction takes place. Copyright © 2007 John Wiley & Sons, Ltd.     

Arias Intensity Assessment of Liquefaction Test Sites on the East Side of San Francisco Bay Affected by the Loma Prieta,California, Earthquake of 17 October 1989

Uncompacted artificial-fill deposits on the east side of San Francisco Bay suffered severe levels of soil liquefaction during the Loma Prieta earthquake of 17 October 1989. Damaged areas included maritime-port facilities, office buildings, and shoreline transportation arteries, ranging from 65 to 85 km from the north end of the Loma Prieta rupture zone. Typical of all these sites, which represent occurrences of liquefaction-induced damage farthest from the rupture zone, are low cone penetration test and Standard Penetration Test resistances in zones of cohesionless silty and sandy hydraulic fill, and underlying soft cohesive Holocene and Pleistocene sediment that strongly amplified ground motions. Postearthquake investigations at five study sites using standard penetration tests and cone penetration tests provide a basis for evaluation of the Arias intensity-based methodology for assessment of liquefaction susceptibility.     

甘孜-玉树断裂带的近代地震与未来地震趋势估计

通过对甘孜－玉树断裂带上近代地震的震级、震中位置和地震地表破裂的空间展布特征的研究，采用Ｎｉｓｈｅｎｋｏ和Ｂｕｌａｎｄ（１９８７）发展的“特征地震复发时间通用分布”概率模型，即“ＮＢ”模型，对甘孜－玉树断裂带各段落未来５０ａ内强震趋势进行了估计。根据研究结果识别出，未来５０ａ内本断裂带内马尼干戈断裂段具有强震复发的高危险性，当江断裂段强震复发的可能性也不能排除，这为地震中长期预报提供了重要依据     

地震触发砂土液化总应力判别法——以北京密云水库白河主坝震害为例

在二维应力状态下，地震在土体中不仅产生水平剪应力τvh，而且引起一般情况不可忽略的竖向动正应力σv及水平动正应力σh，在研究地震触发砂土液化的应力条件及液化判别方法时尖考虑这三种动应力的联合作用，本文基于莫尔－库伦强度准则，采用总应力方法，能够考虑地震动水平剪应力τvh，竖向动正应力σv及水平动正应力σh共同作用的砂土液化判别准则，并且经北京密云水库白河主坝震害为例，说明了这种液化判别准则的有效性及其使用方法。     

Evaluation of sheet pile-ring countermeasure against liquefaction for oil tank site

The evaluation of a countermeasure against liquefaction which uses a sheet pilering for oil tank sites is presented. The simulation of earthquake responses observed at tank sites with and without sheet pile-ring is first performed to validate the three-dimensional finite element numerical model. Using the numerical model, liquefaction analysis is performed and the excess pore water pressure generated in the soil and the settlement of tank are investigated. The comparison of two- and three-dimensional models is also conducted to assess the applicability of two-dimensional analysis. The results show that the numerical model could simulate the observed earthquake responses of tank-ring-soil system, and that the excess pore water pressure and the settlement of the tank could be significantly reduced using a sheet pile-ring. The two-dimensional analysis proves to be capable of representing the main features of the dynamic response of the three-dimensional tank-ring-soil system.     

Finite deformation analysis of liquefaction-induced flow failure in soil embankments

Summary A finite element formulation is proposed for finite deformation dynamic analysis of saturated soil systems. The formulation is based on an updated Lagrangian approach and specifically considers the finite deformation effects on the flow of water through a soil element which undergoes a large deformation or rotation. A two-surface plasticity model is used to model the stress-strain behaviour of the soil skeleton. The proposed formulation has been implemented and is applied to simulate the response of a centrifuge model embankment. The calculated response is in good agreement with the observed behaviour of the soil embankment in the centrifuge test.     

Evaluation of liquefaction potential of marine sandy soil with piles considering nonlinear seismic soil–pile interaction; A simple predictive model

Abstract

An elastoplastic, dynamic, finite-difference method was applied to study the effects of nonlinear seismic soil–pile interaction on the liquefaction potential of marine sand with piles. The developed model was well validated using the centrifuge test. The results showed that acceleration, bending moment, and excess pore water pressure complied well with centrifuge test results. The effect of different affecting parameters on liquefaction potential was investigated using parametric study. Using a sensitivity analysis, the pile embedment parameter was shown to be the most influential parameter. Finally, applying the evolutionary polynomial regression technique, a new model for predicting the liquefaction potential was presented.     

Numerical Simulation of Seabed Response and Liquefaction due to Nonlinear Waves

Based on Biot＇s consolidation theory, a two-dimensional model for computation of the seabed response to waves is presented with the finite element method. Numerical results for different wave conditions are obtained, and the effects of wave non-lineafity on the wave-induced seabed response are examined. Moreover, the wave-induced momentary liquefaction in uniform and inhomogeneous seabeds is investigated. It is shown that the wave non-linearity affects the distribution of the wave-induced pore pressure and effective stresses, while the influence of wave non-linearity on the seabed liquefaction potential is not so significant.