Abstract: Pile foundations are widely used in geotechnical engineering. Meanwhile, the calculation method and reliability of the pile vertical bearing capacity attract more attention from geotechnical engineers. The pile capacity is affected by the uncertainty of properties of the layered soil. To solve this problem, we present herein a robust geotechnical design (RGD) as a new geotechnical design concept based on the reliability design (RBD). The mean and standard deviation of the soil properties are considered as the uncertainty of soil parameters in RGD method. and the scope of the RGD method is expanded in the pile vertical bearing capacity from sand to clay by introducing more soil properties. The pile side friction(Qside), calculated layer by layer by RGD method, is used as one of the uncertain parameters in the change of applicability of the pile vertical bearing capacity by layered soil. Both of ultimate limit state (ULS) and serviceability limit state (SLS) are used as performance function in pile design. In this paper, as a safety evaluation standard, robustness is used to evaluate the feasibility of the design scheme in pile design with the RGD method. With the RGD approach, the focus is to satisfy two design objectives, namely cost-efficiency and robustness. As with multi-objective engineering optimization, it is possible to provide a best solution set to accomplish the goal both in cost-efficiency and robustness. Meanwhile, the pile vertical bearing capacity of the design is guaranteed.

Key words: pile foundation, layered soil, uncertainty, robustness