GEOL1028 Advanced Geotechnical Engineering - University of Greenwich

Topic: Computational Geotechnics; Elastic and Elastic-plastic deformation of piles in vertical and horizontal loading.

Coursework brief:

A bridge pier is built on a 3-by-3 pile group foundation, which needs to carry a vertical load and overturning moment, as shown in Figure 1. The data to use are given in Table 1, apart from the soil properties, which you can freely select from the literature, for a typical soil type. Assume that the soil conditions are homogeneous and that the soil behaviour remains always elastic.

The analysis requires the following steps:

Question 1) Run a theoretical calculation of the various Winkler spring stiffnesses needed for the analysis and calculate the overall vertical pile group stiffness, considering interaction effects by using the Dobry & Gazetas interaction factors.

Question 2) Calculate the expected settlement and rotation of the pile group, considering pile group interaction effects.

Question 3) Create a valid model in Plaxis 2D, using a very stiff "plate" element for the pile cap and "Embedded Beam Row" elements for modelling the middle row of the pile group. To avoid contact stresses between the pile cap and the soil, you place the top of your piles 0.5m above the soil surface. Soil material can be model with a linear elastic model. Compare your Plaxis results to your theoretical elastic analysis in (1) and (2).

Your understanding, analytical capabilities, engineering judgement, as well as your personal reflections, need to be evident in your final report.