Comparisons of the prediction methods for ground failure and construction of the DATA-BASE of those methods.

在本研究中，采用多种失效预测方法进行了一系列的稳定性分析和变形分析。从这些分析中得出的主要结论总结如下：采用有限元方法对一种速率敏感饱和黏土的承载力和塑性流动进行了一系列的应力-流动耦合分析。黏土地基不排水承载力随加载速率的增加而增大，与土体抗剪强度的增加相一致。实际上，无论加载速率如何，承载系数<N_c>几乎保持恒定值。在恒定荷载作用下，土体发生蠕变，应力分布显著。与在蠕变过程中土体剪应力保持恒定的假想情况相比，这种现象大大延长了地基粘土的可能破坏时刻。通过在粘塑性流动规律中引入新的材料函数和内部变量，可以建立正常固结粘土的粘塑性本构模型。该模型可以描述随时间变化的行为，如应变率对应力-应变行为和蠕变破裂（包括加速蠕变）的影响。结合有限元预测方法，对复合防波堤的监测性能进行了讨论。最大侧向位移与沉箱沉降之比较低，是施工阶段所保证的稳定性的最明显体现。海底沉降测量提供了一套有用的信息，通过沉降剖面可以清楚地识别地面变形的二维性质。

In this study, a series of stability analyses and deformation analyses were carried out by using several kinds of failure prediction methods. The main conclusions drawn from these analyses are summarized as follows.1. A series of coupled stress-flow analyses for the bearing capacity and plastic flow of a rate-sensitive, saturated clay have been made using the method of finite elements. The undrained bearing capacity of the clay foundation increases with increasing loading rate, in accordance with the associated increase in the shear strength of the clay element. Indeed, the bearing capacity factor, <N_c> , remains at a practically constant value irrespective of the loading rate. The remarkable redistribution of stress occurs within the foundation clay undergoing creep under constant loads. This phenomenon prolongs the moment of possible failure of the foundation clay much more, as compared with the fictitious case where the shear stress in the soil mass would have been maintained constant during the creep process.2. By introducing new material functions and internal variables into the viscoplastic flow rule, we could establish a viscoplastic constitutive model for normally consolidated clays. This model can describe time-dependent behavior such as the strain-rate effect on the stress-strain behavior and creep rupture including acceleration creep.3. The monitored performance of a composite breakwater has been discussed, in the light of the during-event predictions using the method of finite elements. The stability ensured during the construction stage is most clearly reflected in the low value of the ratio between maximum lateral displacement and caisson settlement. The undersea measurements of settlements have provided a set of useful information, whereby two-dimensional nature of the ground deformation can clearly be identified through the settlement profile.