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

本研究计划的目的是评估几种不同的方法来预测饱和无黏性土壤在循环剪切应力作用下孔隙水压力的累积。这种应力是由于大地震引起的强烈地面运动而产生的。孔隙水压力的积累会导致建筑物地基的破坏，以及地下生命线，如水、下水道、电力和电信生命线的破坏。当孔隙压力达到一定临界值时，土体发生液化破坏。因此，能够预测孔隙水压力的产生和土壤液化的潜力是非常重要的。在开发预测方法方面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，对这些方法的验证还远远没有完成。1986年4月12日，波弗特海的一个碳氢化合物勘探岛——莫利克帕克岛遭受了未曾预料到的冰荷载，导致砂芯部分液化。该砂岛的结构性能由业主Gulf Canada密切监测，因此，存在一个很好的数据集，用于检查所提出的计算孔隙压力产生和液化的方法。这些数据集正用于研究目的，下列加拿大政府组织发起了一项研究方案：地质调查局、国家研究委员会岩土技术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委员会。美国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。罗格斯大学和普林斯顿大学普雷沃斯特教授的共同努力，是这项研究的一部分。耦合动力场方程同时计算孔隙流体和土骨架响应，考虑了两相之间的动力相互作用。多屈服面塑性可以准确地模拟土骨架的非线性、滞回特性。数值计算是使用通用的三维非线性有限元程序进行的。加拿大和国家科学基金会的研究结果将在1988年8月在温哥华举行的一个讲习班上提出。

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 the Rutgers University and Prof. Prevost at Princeton University, is part of this study. Coupled dynamic field equations calculate pore fluid and soil skeleton response concurrently, accounting for dynamic interaction between the two phases. Multi-yield surface plasticity is used to accurately model the nonlinear, hysteretic behavior of the soil skeleton. The numerical calculations are performed using a general purpose, three-dimensional nonlinear finite element program. The results from both the Canadian and NSF studies will be presented at a workshop to be held in Vancouver in August, 1988.