蠕变粘性土固结沉降计算新简化方法的推广和验证

How to calculate the consolidation settlements of clayey soils is an issue with a long research history,certain difficulty,and controversial arguments. Existing methods can be divided into two types: methods based on Hypothesis A and methods based on Hypothesis B. Now, the international geotechnical communities have a common view that methods based on Hypothesis A does not consider the creep compression in the primary consolidation period, resulting in significant underestimation of the total settlements so that this type of methods shall not be used. On the other hand, methods based on Hypothesis B is logically correct. But this type of methods needs to solve a system of coupled nonlinear consolidation equations numerically. This type of analysis is difficult (convergence problem), existing computer programs are limit and are not suitable for engineers to use. Yin Jianhua (2011)[1] presented a new simplified method based on Hypothesis B for calculation of consolidation settlements of clayey soils in any stress-strain (or void ratio) state in one-dimensional (1D) straining. However, this new method has not been verified. In this project, Yin and his team will extend the new method by Yin (2011) to more complicated problems of multi-layers and with (or without) a vertical drain. The completed equations of the extended method will be presented. More important is that the previous method (Yin 2011) and the newly extended method will be verified in 3 approaches:.(a) The new method (the previous one) will be used to calculate the settlement of published physical model tests. The results will be compared with test results and results from 1-D consolidation modeling with an elastic visco-plastic model(Yin and Graham (1989)[2]. In this way, the approximation errors of the new method will be examined. .(b) A new physical consolidation model with a vertical drain in a soft soil will be designed, built and instrumented. Tests will be carried out. The data can be used to study the mechanism of the consolidation and creep compression of a clayey soil with vertical drain. Then the newly extended method will be used to calculate the settlement of the model tests. The results will be compared with measured data and also values from the method based on Hypothesis A. In this way, the validation of the new method will be verified. At the same time, the problem of Hypothesis A method will be indentified..(c) Data from four soft soil projects will be collected, the first one from Tianjin, the second one from Wenzhou Airport of Zhejiang Province, the third one from Qianhai, Shenzhen City, and the 4th one from a new artificial island project next to Hong Kong Airport. The newly extended method will be used to calculate the settlements of the four sites and will be compared with the measured data. In this way, the new method will be verified. In addition, this task will demonstrate how to apply the new method for settlement calculation of real projects.

如何计算蠕变粘性土固结沉降是有很长研究历史、一定难度和带有争议性的国际性问题。计算方法有假设A方法和假设B方法。现在的共识是假设A方法没考虑主固结期的蠕变，低估了沉降，因此不能用。假设B方法是对的，但要作非线性固结耦合数值计算，其计算难度大，软件少，不适工程师使用。本文在殷建华2011年[1]初提出的基于假设B新简化方法上，将其推广到适合多层土和有排水板的固结沉降计算，并做多方面验证：（1）与采用弹黏塑性本构方程的耦合固结分析结果对比捡查简化误差，（2）与室内带排水板的固结物理模型实验结果比较，（3）与内地与香港4个典型软土填海（地基）工程实测沉降比较。通过这些研究工作，期望可以验证新简化方法及其推广方法的精度和使用方便，从而解决如何计算蠕变粘性土固结沉降的国际性难题，为中国在这个课题的研究上作出供献。

如何计算蠕变粘性土固结沉降是有很长研究历史、一定难度和带有争议性的国际性问题。计算方法有假设A方法和假设B方法。现在的共识是假设A方法没考虑主固结期的蠕变，低估了沉降，因此不能用。假设B方法是对的，但要作非线性固结耦合数值计算，其计算难度大，软件少，不适工程师使用。本文在殷建华2011年黄文熙讲座文章提出的基于假设B新简化方法上，将其推广到适合单层和多层土和有排水板的固结沉降计算，推导出新方法的公式，并做多方面验证。 研究内容有：（1）对殷建华2011年黄文熙讲座文章提出的基于假设B简化方法( 叫老假设B简化方法)作了很大的改进， 使新的简化方法适合个中应力状态（正常固结，超固结，加载和卸载）， 单层和多层土和有排水板的固结沉降计算； （2）做了大量的验证：（i）与采用弹黏塑性本构方程的耦合固结分析结果对比捡查简化误差，（ii）与室内固结物理模型实验结果比较，（iii）与内地与香港4个典型软土填海（地基）工程实测沉降比较。重要结果和关键数是：通过这些研究工作，已经验证了新的简化方法的精度和使用范围； 新的简化方法简单和容易计算； 关键数据已在SCI论文内发表。科学意义是：新的基于假设B简化方法解决如何计算蠕变粘性土固结沉降的国际性难题，为中国在这个课题的研究上作出供献。