Electrokinetic stabilisation as a subsidence remediation technique

Clinton, Thomas (2017). Electrokinetic stabilisation as a subsidence remediation technique. University of Birmingham. Ph.D.

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Abstract

This study comprises a three part investigation into electrokinetic stabilisation (EKS): numerical modelling, laboratory trials and site trials. The numerical modelling was introduced to identify issues in the physical trials and assess proposed site trial solutions and associated configurations. The laboratory trials concentrated on electrode development and chemical stabiliser combinations in conjunction with known practical issues such as electrode polarisation and current intermittence effects. English China Clay batches combined with predetermined chemical stabiliser mixes were cured for up to 540 days and tested for standard engineering indexes and electrodes were tested for durability in liquids and under electrolysis. Optimum electrodes, determined through current transfer and durability results, along with optimum chemical combinations, determined through increase in undrained shear strength and reduction is linear shrinkage, were then combined to determine the effects on English China Clay under a mock strip footing for 30 days. It was shown that EKS has a negligible effect on the footing itself through either damage or level changes.

The methodology was developed from the laboratory trials where the optimum electrode type, chemical combination and current intermittence times were developed, and applied to a site trial near Watford, UK. Four trials were conducted consisting of: a control; a vertical electrode set‐up, a vertical electrode set‐up using current intermittence and a raked electrode set‐up. All trials consisted of a 0.3x0.3x1.0m strip footing with treatment targeted at beneath the concrete. EKS was conducted for 56 days on a predominantly London Clay based made ground material with apparent resistivity measurements taken pre‐, peri‐ and posttreatment where apparent resistivity measurements showed the movement of the stabilising fluids over time. Site monitoring included voltage, current, air temperature and footing underside temperatures. Post treatment testing included standard engineering index testing, chemical analysis and SEM photography to determine the effects of the treatment regime. It was determined that the vertical electrode system showed most beneficial clay improvements through the laboratory testing and apparent resistivity results and as in the laboratory trials, negligible effect on the strip footings.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

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