Load Sharing mechanism of Piled-Raft-Foundations

在实践中，深基础是由一组桩连接在一起的混凝土筏。筏板的作用是将柱荷载均匀地传递给桩。然而，它并不与桩分担建筑负荷。而工程师往往设计筏板基础单独承担整个建筑物的荷载。因此，桩基设计被认为是高度保守的，实际上是不经济的。桩筏基础的概念在世界范围内得到越来越多的认可。虽然工程师认识到筏板对基础荷载的贡献，但该领域的研究一直滞后于估算筏板份额。这是由于桩/土/筏之间的相互作用本质上是复杂的，现场测试充其量是困难的。在文献中，可以找到几份关于桩筏基础荷载-沉降关系的报告。然而，这些报告是基于有限的模型，并没有认识到一些重要的控制参数的影响和三维应力变形机制，这发生在桩筏基础。在本建议中，将进行桩筏基础的试验和数值研究。将开发一个三维数值模型来模拟桩筏基础的情况，并在原型实验装置上进行实验室测试。在用实验结果和文献中可用的数据验证数值模型之后，将使用该模型来检查参数，这些参数被认为支配该基础的性能。本文的研究成果对高层建筑桩筏基础的施工具有重要的经济意义，同时又不影响其安全性。预计所制定的设计理论、准则和建议将纳入加拿大基础工程手册和美国土木工程师学会实践手册。同样重要的是要注意到，该项目将为高素质人员和科学家提供培训。

In practice, deep foundations are made of a set of piles connected together with a concrete raft. The role of the raft is to transfer the column load to the piles uniformly. It does not however share the building load with the piles. While engineers often design raft foundation alone to carry the entire building load. Accordingly the design of pile foundations is regarded as highly conservative, in fact uneconomical. The concept of Piled-Raft-Foundation has been increasingly receiving recognition around the world. While engineers recognize the contribution of the raft to the foundation loads, research in this field has been lagging to estimate the raft share. This is due to the fact that interaction among the piles/soil/raft is complex in nature and field testing is difficult at best. In the literature, several reports can be found dealing with the load-settlement relationship of piled-raft foundations. Nevertheless, these reports are based on limited modeling, and failed to recognize the effect of some vital governing parameters and the three-dimensional stressdeformation mechanism, which take place within the piled-raft foundation. In this proposal; experimental and numerical investigations on piles-raft foundation will be performed. A three-dimensional numerical model will be developed to simulate the case of piled-raft foundation and laboratory tests will be conducted on prototype experimental set-up. After validating the numerical model with the experimental results and the data available in the literature, the model will be used examine the parameters, believed to govern the performance of this foundation. The results of this study will have significant economic impact on the construction of piled-raft foundations for high-rise buildings without compromising on the safety. It is expecting that the design theories, guidelines and recommendations developed will be incorporated in the Canadian Foundation Engineering manual and American Society of Civil Engineers manual of practice. It is equally important to take note that this project will provide training to the Highly Qualified Personnel and scientists.