Evolution of the pore pressure due to vibratory installation of sheet piles in sand

Evolution of the pore pressure due to vibratory installation of sheet piles in sand

Arun Kumar, Anchal Bhaskar (TU Delft Civil Engineering & Geosciences)

Broere, W. (mentor)
de Nijs, R.E.P. (graduation committee)
Cicirello, A. (graduation committee)
Gkekas, Stefanos (graduation committee)

Delft University of Technology

2020-10-23

Vibratory installation of sheet piles is the most economic and suitable for the sandy soil because of its mechanism. However, the process induces excess pore pressure in saturated conditions leading to subsidence. This research focuses on the development of a tool-based solution to predict the excess pore pressure due to vibratory installation, which shall be verified by the postdiction of Kademuur Damrak measurements. This tool will help engineers quantify the impact of generated excess pore pressure on adjacent structures. The proposed work attempted to achieve its objective by answering the following main and sub research questions. How can the existing knowledge on generation and evolution of porewater pressure during vibratory installation be effectively integrated into a model/tool, which verified by the postdiction of Kademuur Damrak measurements, can practically estimate the porewater over-pressure during vibratory installations? • What are the parameters that influence the dissipation of the excess pore pressure? • How does the generation and dissipation of excess pore pressure vary in the liquefied zone from non-liquefied? • How can the vibration attenuation affect the generation of excess pore pressure in the sand? • What are the limitations and controlling parameters of this model or tool? The proposed work combines dynamic soil response and transient groundwater flow model to simulate the evolution of pore pressure due to vibratory loading. Based on the degree of modulus degradation due to the vibratory loading the soil, it is zoned into three. This is also termed as a multiscale computational framework. This allows for the formations liquefied and non-liquefied zone. The threshold acceleration of 0.1g - 0.3g must be available for the soil to liquefy [66]. The non- liquefied zone is fed by the groundwater flow from the liquefied zone. According to the Theis equation, head response due to constant pumping in an aquifer is influenced by the rate of discharge (V), storativity(S) and transmissivity(T), distance from the source. This inspired to model the driving of sheet pile with an analogous to the pumping of well. During the constant head loading due to the pumping, there is an increase in the head radially outward from the source. This resembles the phenomenon of pre-shearing in the field. The driving of the sheet pile was stimulated by the constant head loading. The application of time series analysis (PRIFICT method) [8] provides the first estimation of the pore pressure response from the first of three days of field piezometric data of Kademmur damrak. The semi-empirical model was formulated influenced by the head response of the slug test. The response of the time series analysis helped to calibrate the semi-empirical model. The relationship evolved between the physical and modelling parameters established that the hydraulic conductivity is the key parameter in both the generation and the dissipation of the excess pore pressure. The analysis of the field data establishes the conservative assumption of 1m for the width of the liquefaction zone. The analysis of accelerometer data from the Amsterdam noord zuid metro line tunnel helps to establish the dependency of liquefaction on acceleration amplitude. This bolstered the threshold acceleration for liquefaction to be 0.1 - 0.3g. The simple flow only Plaxis model helped to validate the proposed hypothesis. The hydraulic conductivity was established as the key parameter of the model. The integration of dynamic generation and transient groundwater flow model helped to analyse the evolution of excess pore pressure.

http://resolver.tudelft.nl/uuid:8cadcf06-3303-45d2-8247-d9a88c447558

2021-03-31

Student theses

master thesis

© 2020 Anchal Bhaskar Arun Kumar