Prediction of Pore Pressure Generation in Soil Foundations Using Data from Molikpaq I-65: II

本研究的目的是评估几种不同的预测饱和无粘性土在循环剪应力作用下孔压累积的方法。这种应力是由于大地震引起的强烈地面运动而产生的。孔隙水压力的积聚可能导致建筑物基础的破坏，以及地下生命线的破坏，如自来水、下水道、电力和电信生命线。当孔压达到临界值时，破坏是由土的液化引起的。因此，能够预测孔隙水压力的产生以及土的液化潜力是非常重要的。在预测方法的开发上已经付出了相当大的努力，但由于缺乏数据来检验这些方法，这些方法的验证还远未完成。1986年4月12日，位于波弗特海的油气勘探岛屿莫里帕克岛受到了意想不到的冰荷载，导致砂芯部分液化。这个沙岛的结构性能受到所有者加拿大海湾的密切监测，因此，存在一个极好的数据集，可以对照建议的孔压产生和液化计算方法进行验证。这一数据集正用于研究目的，加拿大政府以下机构已经启动了一项研究计划：地质调查局、国家研究理事会岩土研究副委员会海洋开发小组委员会和能源研究与开发小组。由国家科学基金会支持的一项类似研究与加拿大的倡议密切协调。伍德沃德-克莱德大学的Idriss博士、Moriwaki博士和Bekae博士以及加州大学伯克利分校的Seed教授和伦斯勒理工学院的Dobry教授共同努力是这项研究的一部分。它正在评估现有的预测液化发生的方法之一。在频域中采用三维和二维等效线性动力有限元分析来考虑三维效应。采用二维非线性有限差分方法对土体中的孔压增加进行了主要分析。加拿大和国家科学基金会的研究结果将在1988年8月在温哥华举行的研讨会上公布。

The objective of this research program is to evaluate several different methods for predicting pore water pressure buildup in saturated cohesionless soils when subjected to cyclic shear stresses. Such stresses are generated as a result of the strong ground motions resulting from a large earthquake. The buildup in pore water pressure can result in the failure of building foundations, as well as of underground lifelines such as water, sewer, power, and telecommunication lifelines. The damage results from the liquefaction of the soil when the pore pressure reaches a critical level. Thus, it is very important to be able to predict the generation of pore water pressure, and the potential for the soil to liquefy. Considerable effort has gone into the development of prediction methods, but the validation of these methods is far from complete due to a lack of data against which to check them. In April 12, 1986, the Molikpaq, a hydrocarbon exploration island in the Beaufort Sea, was subjected to ice loads which had not been predicted, and which caused the sand core to partially liquefy. The structural performance of this sand island was closely monitored by the owner, Gulf Canada, and as a result, an excellent data set exist against which to check the methods proposed for calculating pore pressure generation and liquefaction. This data set is being made available for research purposes, and a research program has been initiated by the following Canadian Government organizations: The Geological Survey, the Subcommittee on Marine Development of the National Research Council's Associate Committee on Geotechnical Research, and the Panel on Energy Research and Development. A similar study supported by the National Science Foundation is closely coordinated with the Canadian initiative. This joint effort between Drs. Idriss, Moriwaki, and Beikae at Woodward-Clyde and Professor Seed at the University of California at Berkeley, and Professor Dobry at Rensselaer Polytechnic Institute is part of this study. It is evaluating one of the existing methods for predicting the occurrence of liquefaction. Three-dimensional effects are considered using three-dimensional and two-dimensional equivalent-linear dynamic finite element analyses in the frequency domain. The main analysis for the pore pressure increase in soils is performed using a two-dimensional nonlinear finite difference method. The results from both the Canadian and NSF studies will be presented at a workshop to be held in Vancouver in August, 1988.