Thermo-hydro-mechanical characterisation of London clay
File(s)
Author(s)
Chen, Sihua
Type
Thesis or dissertation
Abstract
Geothermal energy has been increasingly utilised in recent years to meet the sustainability targets of civil engineering structures. Ground Source Energy Systems (GSESs) that make use of low enthalpy geothermal energy have been shown to be efficient in providing low carbon heating and cooling to structures. To better understand the impact of the Ground Source Energy Systems on the surrounding ground, it is important to obtain high-quality laboratory testing data regarding the thermo-hydro-mechanical (THM) behaviour of soils.
Three pieces of temperature-controlled testing equipment designed at the Imperial College Geotechnical Laboratory were used in this research. i) The existing isotropic apparatus was enhanced with the installation of a mid-height pore pressure probe, to enable accurate monitoring of pore water pressure changes at different locations of the soil specimen during multiple cycles of heating and cooling. ii) A new thermal triaxial apparatus with a double load-cell measuring system was developed to enable the shearing of soil specimens at both ambient and elevated temperatures. iii) A new oedometer apparatus with a thermal bath was developed for the measurement of compression properties of London clay under different temperature levels.
Thermal and mechanical calibrations have been performed on the instrumentation and are presented in this thesis. Procedures of how the measured and calculated values are obtained and how the calibration curves are determined are explained. Trail tests with dummy samples and real soil tests have been performed to validate the calibration and to assess the calibration errors. Consistent protocols for thermal testing of clays are developed and documented here. Corrections are applied to the data where appropriate. The assumptions and expressions used for corrections are presented. The design of the equipment, thermal and mechanical calibrations, testing procedures and corrections for data processing presented in this thesis can be used as a reference to perform thermal testing on soils in the future.
The effect of temperature on the behaviour of London clay has been investigated and presented. Some key aspects of the soil behaviour, including compression characteristics, preconsolidation pressure, volume change, strength, stiffness and pore water pressure, have been evaluated. Soil behaviour observed in this research have been compared with that from the same or other clays in published work. Results obtained in this research could be used to calibrate appropriate constitutive models, for example, the fully coupled thermal model in the Imperial College Finite Element Program (ICFEP).
Three pieces of temperature-controlled testing equipment designed at the Imperial College Geotechnical Laboratory were used in this research. i) The existing isotropic apparatus was enhanced with the installation of a mid-height pore pressure probe, to enable accurate monitoring of pore water pressure changes at different locations of the soil specimen during multiple cycles of heating and cooling. ii) A new thermal triaxial apparatus with a double load-cell measuring system was developed to enable the shearing of soil specimens at both ambient and elevated temperatures. iii) A new oedometer apparatus with a thermal bath was developed for the measurement of compression properties of London clay under different temperature levels.
Thermal and mechanical calibrations have been performed on the instrumentation and are presented in this thesis. Procedures of how the measured and calculated values are obtained and how the calibration curves are determined are explained. Trail tests with dummy samples and real soil tests have been performed to validate the calibration and to assess the calibration errors. Consistent protocols for thermal testing of clays are developed and documented here. Corrections are applied to the data where appropriate. The assumptions and expressions used for corrections are presented. The design of the equipment, thermal and mechanical calibrations, testing procedures and corrections for data processing presented in this thesis can be used as a reference to perform thermal testing on soils in the future.
The effect of temperature on the behaviour of London clay has been investigated and presented. Some key aspects of the soil behaviour, including compression characteristics, preconsolidation pressure, volume change, strength, stiffness and pore water pressure, have been evaluated. Soil behaviour observed in this research have been compared with that from the same or other clays in published work. Results obtained in this research could be used to calibrate appropriate constitutive models, for example, the fully coupled thermal model in the Imperial College Finite Element Program (ICFEP).
Version
Open Access
Date Issued
2022-03
Online Publication Date
2023-05-31T23:01:13Z
2023-08-22T12:35:06Z
Date Awarded
2022-06
Copyright Statement
Creative Commons Attribution NonCommercial NoDerivatives Licence
Advisor
Zdravković, Lidija
Carraro, Joao
Publisher Department
Civil and Environmental Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)