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The effects of fibre (0–3 %) and cement (0–3 %) additives, on Toyoura sand were examined under consolidated drained compression and extension loading conditions. All samples were prepared to a target dry density value (e.g., ρ d = 1.489 g/cm 3 ) of Toyoura sand using under-compaction moist tamping technique. In compression, the unreinforced specimens exhibited a behavior of medium dense sand and reached a peak deviator stress ( q p ) at approximately 4 % axial strain ( ϵ a ) for the varying mean effective stresses, pʹ (i.e. 50–400 kPa). The peak drained strength increases in fibre reinforced cemented specimens were found to be up to 132 % (lower effective stresses) and 243 % (higher effective stresses), while, the drained strength increases at critical state for the fibre reinforced cemented specimens were found to be up to 105 % (lower effective stresses) and 245 % (higher effective stresses). Overall, the fibre and cement additives increased the stiffness, peak and strength at critical state of pure Toyoura sand but were found to be least effective in extension loading. Moreover, the stress ratio, peak and critical state stress ratios increase with the addition of fibres and cement. The secant modulus shows limited increases for the fibre reinforced specimens. However, a significant improvement in the secant modulus is observed for the fibre reinforced cemented specimens. For both unreinforced and reinforced specimens there is a decrease in volumetric strain with greater effective stresses or in other words, the rate of dilation decreases with increases in effective stresses. The fibre and cement additives also increased the strength parameters (frictional angle, cohesion), dilatancy angle, slope of the critical state line, and decreased the state parameter of pure Toyoura sand.

The disposal of 2011 Japan earthquake waste has become an important issue in Japan and it is not realistic or economical to send all of these wastes to landfill sites, due to limited space, high costs, and related environmental issues. In sustainable geotechnical applications, mixing of the separated soils from disaster wastes with additives (e.g., cement and fiber) is required to improve their strength and stiffness characteristics. In this study, monotonic triaxial drained compression tests are performed on medium dense specimens of Toyoura sand-cement-fiber mixtures with different percentages of fiber and cement (e.g., 0–3%) additives. The experimental results indicate that behavior of the mixtures is significantly affected by the concentration of fiber and cement additives. Based on a comprehensive set of test results, modifications to the series of equations were developed that can be used to evaluate the shear modulus and mobilized stress curves at small-strain levels. The experimental results and model comparison show that the elastic threshold strain (γe), reference strain (γr), increases with fiber and cement additives. In addition, the range of curvature parameter, from 0.88 to 1.0, provides a good comparison with the results of small-strain measurements. Overall, the comparison of the results and model shows that the small-strain measurements obtained using local strain transducers fall within the range of model upper and lower bound curves. The results of the unreinforced, fiber, and cemented sand shows a close agreement with the model mean curve, but fiber-reinforced cemented sand shows a good comparison with model upper bound.

The foundations of many large onshore and offshore structures are designed to be symmetrical polygons (e.g. octagons). However, the available analytical approaches for the ultimate limit state design of shallow foundations under combined loadings focus predominately on strip, rectangular and circular foundations. Although equivalent inscribed circular foundations have been recommended for foundation design by some guidelines, this simple approximation for octagonal foundations needs to be rigorously assessed due to the high dependence of the failure envelope on foundation shapes. The present study has investigated the general VHM (vertical, horizontal and moment) failure envelope of octagonal foundations under a zero-tension interface for undrained soil conditions using finite element analysis. The effects of soil strength heterogeneity and foundation embedment on the VHM failure envelope have been investigated. Analytical expressions have also been proposed to characterize the failure envelopes for use in design. The results show that octagonal foundations have larger bearing capacity than the corresponding circular foundations, and the difference (around 10%) between them is not negligible. A full 3-D analytical expression for the VHM failure envelope has also been proposed based on the calculated failure envelopes.

The design of shallow foundations for wind turbines is typically governed by serviceability and fatigue limit states. To estimate the deformations of shallow foundations under working loads, existing design standards generally employ analytical uncoupled isotropic elastic solutions based on idealized soil conditions. However, many natural soil deposits exhibit some degree of stiffness anisotropy due to their deposition and complex stress history. This study has investigated coupled elastic stiffness coefficients for circular shallow foundations founded on cross-anisotropic soils under combined VHMT loadings (vertical, horizontal, moment and torsional) using finite element analysis. A three-parameter anisotropic soil model was applied to the problem. The study extensively explores the effects of soil stiffness non-homogeneity (i.e. linear increase of elastic modulus with depth) and foundation embedment on the foundation stiffness coefficients. Fitted expressions of these stiffness coefficients were also derived. In addition, a practical application using the proposed stiffness coefficients was presented to demonstrate the effects of soil stiffness anisotropy on the responses of a typical large wind turbine shallow foundation.

Interactions between wind and trees control energy exchanges between the atmosphere and forest canopies. This energy exchange can lead to the widespread damage of trees, and wind is a key disturbance agent in many of the world's forests. However, most research on this topic has focused on conifer plantations, where risk management is economically important, rather than broadleaf forests, which dominate the forest carbon cycle. This study brings together tree motion time-series data to systematically evaluate the factors influencing tree responses to wind loading, including data from both broadleaf and coniferous trees in forests and open environments. We found that the two most descriptive features of tree motion were (a) the fundamental frequency, which is a measure of the speed at which a tree sways and is strongly related to tree height, and (b) the slope of the power spectrum, which is related to the efficiency of energy transfer from wind to trees. Intriguingly, the slope of the power spectrum was found to remain constant from medium to high wind speeds for all trees in this study. This suggests that, contrary to some predictions, damping or amplification mechanisms do not change dramatically at high wind speeds, and therefore wind damage risk is related, relatively simply, to wind speed. Conifers from forests were distinct from broadleaves in terms of their response to wind loading. Specifically, the fundamental frequency of forest conifers was related to their size according to the cantilever beam model (i.e. vertically distributed mass), whereas broadleaves were better approximated by the simple pendulum model (i.e. dominated by the crown). Forest conifers also had a steeper slope of the power spectrum. We interpret these finding as being strongly related to tree architecture; i.e. conifers generally have a simple shape due to their apical dominance, whereas broadleaves exhibit a much wider range of architectures with more dominant crowns.

A series of consolidated drained and undrained tests are conducted on unreinforced, fibre, cement, and fibre reinforced cemented Toyoura sand specimens with varying relative densities. Three different types of materials e.g., Toyoura sand, polyvinyl alcohol (PVA) fibres, and ordinary Portland cement (OPC) are employed in this study. Specimens in dimensions of 50 mm in diameter and height of 100 mm are prepared in a polyvinyl chloride (PVC) mold to a target dry density value,$ {\\rho }_{d} $= 1.40 g/cm 3 (Dr = 20%) and$ {\\rho }_{d} $= 1.489 g/cm 3 (Dr = 60%) of Toyoura sand using under-compaction moist tamping technique. Fibre reinforced cemented Toyoura sand samples were prepared with 10% moisture content by weight of sand-fibre-cement mixtures. The results on density variation shows that due to a better contact between sand-fibre interaction or sand-cement-fibre bonding and interaction for the denser specimens, a greater increase in shear strength is observed. However, the general effectiveness of fibre and cement additives alone and when mixed together also enhances the strength of unreinforced specimens for loose conditions based on the variation of fibre and cement contents. The results and findings in the current study can be used for the construction of economical and sustainable geotechnical infrastructures.

Increases in forced curtailments at commercial wind farms have triggered a need to investigate turbine behaviour during stopping events. A 2.3 MW commercial horizontal axis wind turbine instrumented with a fiber Bragg grating strain array was subjected to the three most common types of stopping sequences performed by the turbine to measure the supporting tower's structural response. An overview of each considered stop type is included identifying their individual mechanical processes as well as their specific triggers. The along-wind and transverse strain measurements at varying elevations of the tower are presented and discussed. Distinguishable response characteristics for each stop type are identified at stop initiation, during rotor deceleration, and following event completion. Results obtained are subsequently compared to the tower strain reactions as a result of typical power production as well as pure yawing of the nacelle. Furthermore, the strain signal has been subjected to a discrete wavelet transform identifying variations in the signal frequency content, triggered by the stopping events.