Model tests were conducted to analyse the sliding stability of a retaining wall constructed by soilbags. The aim was to obtain an equation calculating the active resultant earth pressure of sand acting on the wall in the ultimate state. Additionally, shear tests on multi-layers of vertically-stacked soilbags were designed to investigate how the interlayer friction resistance varied with the height of the wall. The results show that the active earth pressure acting on the soilbag-constructed retaining wall in the ultimate state is non-linear, but it can be calculated from force equilibrium of a differential element. The interlayer friction resistance of soilbags is found to be related to the shape of the sliding surface. Based on the obtained equation and the unique shear tests results, the sliding stability of the retaining wall constructed by soilbags could be appropriately analysed.

No abstract

This study explores the variability of tropical cyclone (TC) intensification rates (IRs) in the postmonsoon Bay of Bengal (BoB) for the satellite period of 1980–2015. It is found that both number of rapid intensification (RI) events and magnitude of IRs show a robust increase, with a northeastward shift of intensification events. Analyses show that the temporal variability of sea surface temperature dominated the IR variability during 1980–1997. However, the thick barrier layer in the northern BoB was considerably responsible for IR variability during 1998–2015, which significantly contributed to the IR increase. Due to more intensification events occurring over the northeastern region in two recent decades, the thick barrier layer with strong salinity stratification in the northern BoB limits TC-induced sea surface cooling and in turn favors TC intensification. This study has an important implication that air–sea coupled climate model need to realistically simulate upper ocean salinity variability on projecting TC intensity change over the BoB.

An experimental program was undertaken to investigate the effects of lignin fibers and freeze-thaw (FT) actions on the shear strength behavior of an expansive soil. Soil specimens were prepared at five lignin fiber contents. Consolidated undrained triaxial tests were carried out on as-compacted specimens and specimens subjected to 10 FT cycles. Scanning electron microscopy and nuclear magnetic resonance tests were performed to reveal the microstructural characteristics. Test results indicate that the inclusion of lignin fibers leads to a significant increase in the cohesion due to the reason that lignin fibers form spatial networks that increase the bonding among soil aggregates. The cohesion-fiber content relationships are linear and their slope is constant regardless of FT actions, which indicates that the contribution of lignin fibers to the cohesion is not impaired by FT cycles. Lignin fibers alleviate the development of FT-induced cracks and the associated reduction in cohesion. Meanwhile, lignin fibers have little impact on the arrangement and contact stress and roughness among soil particles. Therefore, they have little influence on the friction angle of the soil with or without FT histories.