The University of Southampton
University of Southampton Institutional Repository

Numerical modelling of rows of discrete piles used to stabilise landslides under long-term conditions in clays

Numerical modelling of rows of discrete piles used to stabilise landslides under long-term conditions in clays
Numerical modelling of rows of discrete piles used to stabilise landslides under long-term conditions in clays
A literature review found no rigorous solution for the ultimate lateral pile-soil pressure ( ) in a soil characterised by a frictional failure criterion, and that the popular empirical methods to estimate give profiles with depth that differ significantly. Most existing solutions for the lateral pile capacity in a group are for soil characterised by an undrained shear strength failure condition. Plane strain and constant overburden finite difference analyses (in FLAC3D) were used to model flow of soil around a pile but did not appear to give sensible solutions for a frictional soil. The ultimate pile-soil line load from three-dimensional analysis in FLAC3D behaved as physically expected; passive wedges formed close to the surface giving lower normalised resistance than at greater depths. A number of parametric analyses were carried out using the three-dimensional model to investigate the variation in the ultimate pile-soil line load with the soil strength and pile-soil interface strength. Larger values of initial earth pressure coefficient K0 led to enhanced values of and the mechanisms for this was further investigated by analysing the soil stresses mobilised around the pile as the soil was pushed with the pile. Limit equilibrium pile failure mechanisms were developed from conditions of force and moment equilibrium for the pile based on failure in the soil. Pile limit equilibrium conditions were determined for three failure modes to understand the relationships between pile shear force, bending moment and pile embedment length ratio. Three-dimensional numerical (FLAC3D) models were used to verify the limit equilibrium failure mechanisms. The limit equilibrium equations were found to provide unconservative predictions for the force that the pile can provide to stabilise a slope, compared with the FLAC3D analysis. The program Alp (which models the pile as a beam on springs) gave results that were close to the limit equilibrium calculations. Three-dimensional FLAC3D models were modified to investigate the conditions over which the derived limit equilibrium pile failure mechanisms could reasonably be applied. The centre-to-centre pile spacing was varied from 1 d to 10 d, where d is the diameter of the pile, to understand the pile-soil interaction for a row of piles using the FLAC3D model. When the pile spacing was less than 2 d, the pile stabilising force was the same as for a solid retaining wall. Beyond about 4 d, the piles were found to act individually.
Pan, D.
3ae950b4-ff71-4bca-afd9-e873f51ebc05
Pan, D.
3ae950b4-ff71-4bca-afd9-e873f51ebc05
Smethurst, Joel
8f30880b-af07-4cc5-a0fe-a73f3dc30ab5

Pan, D. (2013) Numerical modelling of rows of discrete piles used to stabilise landslides under long-term conditions in clays. University of Southampton, Faculty of Engineering and the Environment, Doctoral Thesis, 341pp.

Record type: Thesis (Doctoral)

Abstract

A literature review found no rigorous solution for the ultimate lateral pile-soil pressure ( ) in a soil characterised by a frictional failure criterion, and that the popular empirical methods to estimate give profiles with depth that differ significantly. Most existing solutions for the lateral pile capacity in a group are for soil characterised by an undrained shear strength failure condition. Plane strain and constant overburden finite difference analyses (in FLAC3D) were used to model flow of soil around a pile but did not appear to give sensible solutions for a frictional soil. The ultimate pile-soil line load from three-dimensional analysis in FLAC3D behaved as physically expected; passive wedges formed close to the surface giving lower normalised resistance than at greater depths. A number of parametric analyses were carried out using the three-dimensional model to investigate the variation in the ultimate pile-soil line load with the soil strength and pile-soil interface strength. Larger values of initial earth pressure coefficient K0 led to enhanced values of and the mechanisms for this was further investigated by analysing the soil stresses mobilised around the pile as the soil was pushed with the pile. Limit equilibrium pile failure mechanisms were developed from conditions of force and moment equilibrium for the pile based on failure in the soil. Pile limit equilibrium conditions were determined for three failure modes to understand the relationships between pile shear force, bending moment and pile embedment length ratio. Three-dimensional numerical (FLAC3D) models were used to verify the limit equilibrium failure mechanisms. The limit equilibrium equations were found to provide unconservative predictions for the force that the pile can provide to stabilise a slope, compared with the FLAC3D analysis. The program Alp (which models the pile as a beam on springs) gave results that were close to the limit equilibrium calculations. Three-dimensional FLAC3D models were modified to investigate the conditions over which the derived limit equilibrium pile failure mechanisms could reasonably be applied. The centre-to-centre pile spacing was varied from 1 d to 10 d, where d is the diameter of the pile, to understand the pile-soil interaction for a row of piles using the FLAC3D model. When the pile spacing was less than 2 d, the pile stabilising force was the same as for a solid retaining wall. Beyond about 4 d, the piles were found to act individually.

PDF
PHD THESIS-DENG PAN .pdf - Other
Download (29MB)

More information

Published date: 1 October 2013
Organisations: University of Southampton, Infrastructure Group

Identifiers

Local EPrints ID: 359749
URI: https://eprints.soton.ac.uk/id/eprint/359749
PURE UUID: beb56e91-f011-4e2c-b00c-f21c1e0b489b

Catalogue record

Date deposited: 20 Dec 2013 16:17
Last modified: 18 Jul 2017 03:18

Export record

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of https://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×