PhD thesis examiner: Experimental investigation on the impact of temperature during creep and stress relaxation behaviour of London clay

Activity: Examination


The ever-growing climate problem has created a drive to ensure a sustainable future can be achieved within the coming years. In this regard, it is crucial to fully understand the thermal mechanical behaviour of clays under varying temperature fluctuations, especially temperature variations surrounding energy geo-structures. The study aims to assess the impact of temperature, ranging between 20 and 55 Β°C, on the time- and rate-dependent behaviour of clays.
The thesis reports an extensive experimental program on the primary and secondary consolidation, stress relaxation, and rate-dependency. A series of conventional multi-staged loading (MSL) oedometer tests, and temperature-controlled constant rate of strain (CRS) oedometer tests were carried out on saturated and unsaturated reconstituted London clay specimens, collected from the Bank Station project upgrade in London, UK.
The results demonstrate that temperature and suction play a pivotal role in the time- and rate-dependent behaviour of the reconstituted Bank Station London clay specimens. The main findings from the experimental program are as follows;
β€’ An increase in temperature results in a linear decrease in πœŽπ‘ values and in an increase in 𝐢𝛼𝑒 and 𝐢𝛼𝑒/𝐢𝑐 values, especially at higher stresses (> 100 kPa). The 𝐢𝑐 and 𝐢𝑠 parameters are less sensitive to temperature variations.
β€’ A coupled effect of temperature and strain rate on 1D compression response was identified. At a constant temperature, the higher the strain rate, the higher the πœŽπ‘. Similarly, at a constant strain rate, the higher the temperature, the lower the πœŽπ‘.
β€’ The dependence on stress, temperature and suction observed in the Bank Station London clay specimens rejects the hypothesis of a constant 𝛼 assumed by Mesri et al. (1994).
β€’ The coefficient of stress relaxation (𝑅𝛼) values appears to be temperature- and strain rate-dependent. Furthermore, the study demonstrates that the 𝑅𝛼= 𝛼 relationship can be validly applied to the set of vertical stress and temperature appraised in the present work.
Examination held at
  • University of Warwick