Numerical Analysis of Pile installation
Kierownik projektu: Mohsen Misaghian
Wydział Inżynierii Lądowej i Środowiska
Data otwarcia: 2022-02-04
Screw (also known as helical) pile is a kind of displacement pile, consisting of a steel shaft and a number of helix-shaped plates welded to its toe. Helical piles are installed by applying a hydraulic torque unit at the top of the pile making them screw into the soil. Compared to the conventional piles, screw piles provide higher axial capacities and faster installation time. Additionally, low noise and ground vibrations are created during screw pile installation, making this method an environmentally-friendly process.
Similar to the other displacement piles, the installation of screw piles causes disturbances to the characteristics and state of the surrounding soil. Nevertheless, the majority of the theory developed for screw piles focuses on the bearing capacity of the configuration at its final embedment depth, without accounting for the physical mechanism occurring during pile installation and the interaction between soil and the pile.
Despite the recognized effects of the installation procedure on the behavior of helical piles, relatively few attempts have been made to numerically model the installation process, especially in cohesive soils. This can be attributed to the degree of difficulty, since the installation process involves large, predominantly plastic deformation, contact interaction at the soil-helix and soil-shaft interfaces, and material separation at the leading edge of the helical plates as they cut the soil.
The overall aim of this study is to numerically examine the mechanisms governing screw pile installation and the subsequent axial loading. To achieve the aim of research the following objectives are proposed:
1- To simulate the cone penetration test with pore water pressure measurement (CPTu) in normally consolidated (NC) soft soils in order to understand the capability of numerical approach to study the penetration of an object into a soil particulate system.
2- To validate the numerical tools and constitutive models by comparing the results of CPTu modelling with the corresponding field results in Jazowa, Poland.
3- To assess the effects of screw pile installation on the state and properties (with particular attention to the density and vertical stress) of cohesive soils.
4- To quantify related consequences of screw installation in terms of pile behavior under axial loading.
5- To develop engineering guidance for the design of screw piles in cohesive soils.
The new pile technologies bring not only environmental advantages (minimized vibration to nearby, limited noise, minimal soil spoil, limited traffic and using raw materials) but also efficient improvement of the soil characteristics (density, increase in lateral stress). This will benefit geotechnical engineers in more reliable and more economic design of such piles.