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Traditional in-place inclinometers are widely used for monitoring displacements inside a slope. However, these traditional inclinometers have several disadvantages such as electromagnetic interference, signal loss for long distance transmission, gravity dependence and poor durability. Scholars have proposed fibre Bragg grating (FBG)-based in-place inclinometers which can overcome these limitations. However, all such in-place inclinometers are based on the relative displacement between two tips of the rigid segment, but the deformation of the segment is not considered in the calculation, which is not consistent with the actual condition. The error of measurement is due to linear superposition. According to classical indeterminate beam theory, the authors developed a new type of FBG-based in-place inclinometers where the deformation of the segment is coordinated with the casings installed in boreholes. This type of FBG-based in-place inclinometer has been fabricated and calibrated in the laboratory. The measured displacement data are in good agreement with theoretical results obtained using equations derived by the authors based on classical beam theory. After the laboratory calibration, a series of FBG-based in-place inclinometers have been installed in one vertical borehole in a slope in China. Monitoring data of all FBG wavelengths have been collected in rainy and dry seasons, and have been analysed in this paper. It has been found that the slope moves quickly in the rainy season and remains stable in the dry season.

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A novel approach is presented to describe the dynamic interaction system of a large-diameter floating pipe pile and surrounding soils, taking the three-dimensional wave effects into account. The corresponding analytical solutions for longitudinal complex impedance are obtained and subsequently validated via comparisons with existing solutions. Comparative analyses are also performed to illustrate the difference between the present and previous solutions, concerning the wave propagation effect in the radial direction on the longitudinal dynamic vibration of pile shaft. Furthermore, the effects of Poisson's ratio and visco-elastic support beneath the pile toe, on the longitudinal dynamic vibration of pile shaft, are investigated. It is indicated that the presented approach and corresponding solutions provide a more wideranging application for longitudinal vibration analysis of a largediameter floating pipe pile, which can also be reduced to analyze the longitudinal vibration problems of large-diameter floating solid pile and fixed-end pipe pile.

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Sodium aluminosilicate hydrate (NASH) gel is the primary adhesive constituent in environmentally friendly geopolymer. In this study, to understand the thermal behavior of the material, molecular dynamics was utilized to investigate the molecular structure, dynamic property, and mechanical behavior of NASH gel subjected to temperature elevation from 300 K to 1500 K. The aluminosilicate skeleton in NASH gel provides plenty of oxygen sites to accept H-bond from the invading water molecules. Upon heating, around 18.2% of water molecules are decomposed and produce silicate and aluminate hydroxyls. About 87% of hydroxyls are associated with the aluminate skeleton, which weakens the Al-O bonds and disturbs the O-Al-O angle and the local structure, transforming it from an aluminate tetrahedron to a pentahedron and octahedron. With increasing temperature, both Al-O-Si and Si-O-Si bonds are stretched to be broken and the network structure of the NASH gel is gradually transformed into a branch and chain structure. Furthermore, the self-diffusivity of water molecules and sodium dramatically increases with the elevation of temperature, because the decrease in connectivity of the aluminosilicate network reduces the chemical and geometric restriction on the water and ions in NASH gel under higher temperatures. The high temperature also contributes to around 63% of the water molecules further dissociating and hydroxyl groups forming; meanwhile proton exchange between the water molecules and aluminosilicate network frequently takes place. In addition, a uniaxial tensile test was utilized to study the mechanical behavior of the NASH gel at different temperatures. During the tensile test, the aluminosilicate network was found to depolymerize into a branch or chain structure which plays a critical role in resisting the tensile loading. In this process, the breakage of the aluminosilicate skeleton is accompanied with hydrolytic reactions that further deteriorate the structure. Due to the reduction of the chemical bond stability at elevated temperature, both the tensile strength and stiffness of the NASH gel are weakened significantly. However, the ductility of the NASH gel is improved because of the higher extent of structural arrangement at the yield stage and partly due to the lower water attack. Hopefully, the present study can provide valuable molecular insights on the design of alkali-activated materials with high sustainability and durability.