Abstract
The soil beneath a wind turbine withstands not only environmental impacts but also continuous vibrations transmitted from the superstructure. This paper presents an experimental study of the deterioration characteristics of shear strengths of residual soils affected by drying-wetting cycles and continuous vibrations. A series of triaxial tests were performed on compacted residual soil specimens after various drying-wetting cycles and vibrations. The influences of drying-wetting cycles and vibrations on the shear strengths of residual soils with different compaction degrees were analyzed. The results demonstrate that the shear strength and cohesion of compacted residual soils decreased as the number of drying-wetting cycles increased, and they tended to be stable after three drying-wetting cycles. The angle of internal friction decreased linearly with the reduction of compaction degree but was generally not affected by drying-wetting cycles. The shear strength of compacted residual soils also decreased because of continuous vibrations. After 10000 vibrations, the strength was stabilized gradually. Both the cohesion and angle of internal friction showed dynamic attenuation phenomenon. Finally, a modified Mohr–Coulomb strength equation considering the effects of drying-wetting cycles and vibrations was established. This equation could be used to predict the shear strength of compacted residual soils and further estimate the embedded depth of wind turbine foundations.
Highlights
Wind power generation technology has been developed rapidly in recent decades, making wind power the third largest power source after coal-fired power and hydropower
Dynamic triaxial tests were performed to determine the shear strength of residual soils under cyclic drying-wetting and vibrating conditions. e instrument used in the tests was the GDS cyclic triaxial testing system (Figure 4). e tests could be divided into the cyclic dryingwetting phase, consolidation phase, and triaxial shearing phase when examining the influence of drying-wetting cycles on the shear strength
It shows that the influence of drying-wetting cycles on the mechanical behavior of residual soil varies at different compaction degrees
Summary
Wind power generation technology has been developed rapidly in recent decades, making wind power the third largest power source after coal-fired power and hydropower. China has built 42,000 MW wind turbines in several provinces in the south, where hilly, plateau, and mountainous terrains exist, from 2016 to 2020 [2, 3]. Wind turbines in these regions are installed at the top of hills in order to gain sufficient wind energy (Figure 1). E mechanical properties of these materials are relatively weak and can be reduced under cyclic drying-wetting conditions [4, 5]. The combined effect of cyclic drying-wetting environment and continuous vibrations will greatly reduce the strength of the subsoil and cause instability of the wind turbine foundation
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