Innovative methods of ground improvement for railway embankment Peat Fens foundation soil

The aim of this research was to assess the feasibility of biocementing a problematic foundation soil of railway embankments from Peat Fens in East Anglia, UK. Biocementation of soil is an emerging, novel ground improvement technique. It has recently attracted the interest of researchers worldwide because it has been proposed as potentially environmentally superior to chemical grouts and other common soil stabilisers e.g. cement or lime (linked to high CO2 11 emissions). In this study we screened and isolated non-pathogenic indigenous ureolytic microbial candidates with potential for biocementation from samples originating from Peat Fens in East Anglia, UK. Four strains were selected as the most suitable candidates, based on their growth rate and their viability in a wide range of temperatures, pH and soil moisture contents corresponding to typical seasonal field conditions. After a number of Unconfined Compressive Strength (UCS) tests, one strain (Bacillus licheniformis) was selected as the most promising for this soil treatment and used for further study. Two different methods of implementation of the treatments were considered, namely pressure flow soil column and electrokinetic injection. The UCS results supported by CaCO3 measurements as well as microstructural SEM-EDS analysis proved that biocementation did occur for both implementation methods and for a number of treatment combinations. Ongoing work on optimisation of treatments and implementation methods is carried out towards the upscaling of the techniques for in situ implementation which is planned for the next stage of the research