Civil engineering assets and geo-structures continually deteriorate during their lifetime, particularly in harsh environments that may be contaminated with corrosive substances. However, efficient and constant structural health monitoring and accurate prediction of the service-life of these assets can help to ensure their safety, performance, and health conditions and enable proper maintenance and rehabilitation. Nowadays, many of the largest cities throughout the world are situated in coastal zones, leading to a dramatic increase in the construction of nearshore geo-structures/infrastructures which are vulnerable to corrosion attacks resulting from salinity contamination. Additionally, seawater intrusion can threaten the quality and the sustainability of fresh groundwater resources, which are a crucial resource in coastal areas. To address these issues, detection of salinity in soil utilizing a novel polymer optical fibre Bragg grating (POFBG) sensor was investigated in this research. Experiments were carried out at different soil water contents with different salinities to assess the sensor’s response in a representative soil environment. The sensitivity of the POFBG sensor to salinity concentrations in water and soil environment is estimated as 58 ± 2 pm/%. The average standard error value in salinity is calculated as 0.43% for the samples with different soil water contents. The results demonstrate that the sensor is a promising and practical tool for the measurement and monitoring with high precision of salinity contamination in soil.

Abstract. Vertical cuts are prone to several types of failure such as piping, ground heaving, and deep-seated or base failure. The latter is the subject of this study and probably attracts less attention in comparison to other types of failure. Although it is commonly believed that such a failure is rare in normal conditions; in presence of the seepage ow, deep-seated failure is much likely to initiate and advance prior to other types of failure. In this paper, the stability analysis of vertical cuts in granular soils in presence of the seepage ow is studied against the deep failure. To do so, the stability analysis is made by the use of the well-known method of stress characteristics with inclusion of the seepage ow force. This nonuniform ow eld renders the stability analysis quite complex. A semi-analytical approach, based on complex algebra, is presented to nd the ow eld, which is accurate and much faster for calculation of the seepage force at arbitrary points in the eld. The solution of the ow eld is a background solution for the stress eld which is to be found to assess the stability.

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