Application of Novel Fibre Optic Sensors to Monitor Geostructures

The ground as supporting structure to our infrastructure can be a major geohazards and its complex behaviour (still relatively poorly understood), often associated with changes in water contents, temperature and porewater pressure under the various environmental condition, can result in huge risk to urban physical infrastructure, through damage to building, failure of transportation networks or significant loss of utility such as water leakage or power outings. The change in soil water content, temperature, porewater pressure and consequently the soil strain can be due to global climate change (extreme wet and dry weather cycles), seasonal variations, or local site changes such as leakage from utility pipes. Occasional devastating failures result directly from collapse of the supporting ground and consequently the associated infrastructures; a matter that not only concerns civil engineers but also the service users, wider society and owners of the nation's infrastructure. The problem imposes significant financial, environmental and social costs to nations across the world. In the Britain alone in the past 15 years this problem has imposed over £3 billion costs to the economy becoming the most damaging geo-hazard. Soil suction and soil water content play a key role in mechanical properties of the soils such as development of strength and changes in volumes of soil that lie above the natural water table. This project is a multidisciplinary research that brings together the precise measuring of physical parameters using state-of-the-art polymer optic fibre (POF) sensors and advanced numerical modelling of the ground in order to enhance our understanding of the ground condition and its symbiotic relationship with both surface and buried urban infrastructure. In the first stage of this research the PhD will focus on packaging, calibration and investigating the application of novel POF sensors that can accurately measure soil moisture contents, suction pressure, temperature and strain in the ground. The novel sensors can outperform current leading sensors in the market as they are more cost effective and provide higher accuracy. In the second stage, the aim is to develop accurate numerical models of the ground with a specific attention to the role of the above physical parameters measured with POFs (i.e. moisture contents, temperature, strain and suction) and taking cognisance of its partly-saturated nature as well as the role of other major physical, mechanical and environmental conditions. The numerical models (to be validated against available laboratory experiments and/or field data) will be extended to explore various scenarios and capture inter-relationship between contributing parameters of geotechnical engineering problems such as slope sliding, embankment stability and ground collapse. The numerical models will have extensive applications in several key areas of civil engineering and can serve as a tool to analyse geo-structures, and accurately predict the actual condition of the system. The numerical models can be used as an assessment tool to eliminate conditions that lead to fatal failures of both ground and infrastructure.