When analyzing the dynamics of wind turbines under the action of wind and ground motion, mass-point models cannot accurately predict the dynamic response of the structure. Additionally, the coupling effect between the pile foundation and the soil affects the vibration characteristics of the wind turbine. In this paper, the dynamic response of a DTU 10 MW wind turbine under the coupling effect of wind and an earthquake is numerically studied through the combined simulation of finite-element software ABAQUS 6.14-4 and OpenFAST v3.0.0. A multi-pile foundation is used as the foundation of the wind turbine structure, and the interaction between the soil and the structure is simulated by using p-y curves in the numerical model. Considering the coupling effect between the blade and the tower as well as the soil-structure coupling effect, this paper systematically investigates the vibration response of the blade-tower coupled structure under dynamic loads. The study shows that: (1) the blade vibration has a significant impact on the tower's vibration characteristics; (2) the ground motion has varying effects on blades in different positions and will increase the out-of-plane vibration of the blades; (3) the SSI effect has a substantial impact on the out-of-plane vibration of the blade, which may cause the blade to collide with the tower, thus resulting in the failure and damage of the wind turbine structure.

Soft clay is extensively distributed in the Yangtze River Delta of China. Many seismic events indicate that underground structures buried in soft soil may suffer severe damage from earthquakes. In this study, a series of bidirectional dynamic cyclic triaxial tests were conducted to investigate the dynamic behavior of soft clay, considering different confining pressures and consolidation stress ratios. A simplified equivalent seismic loading method based on the strain failure criterion was proposed. The obtained equivalent amplitude of soft clay calculating by the critical cyclic stress ratio is averagely 1.58 times that of the sand liquefaction method. Under equivalent seismic cyclic loading, the dynamic shear strain and excess pore pressure of soft clay increases with the increase of confining pressure. The relationship between the maximum excess pore pressure and the corresponding shear strain can be expressed by a hyperbolic function. Due to the weakening effect of seismic loading, the shear modulus decreases as the shear strain increases, with a sudden reduction of up to 45 %. The shear modulus and damping ratio increase with the increase of confining pressure and consolidation stress ratio. The research results may provide some valuable insights into the seismic design practices in soft clay areas.

The present research study aims to create accurate and comprehensive inventory mapping while investigating the geomorphological and geotechnical characteristics of the large, deep-seated, and damaging El Kherba landslide triggered by the August 7, 2020 (Mw 4.9) Mila earthquake. The methodology relies on the analysis of results obtained through detailed field investigations, satellite image interpretation, deep boreholes equipped with piezometers, laboratory tests, in situ tests, and numerical simulations. The resulting landslide inventory map reveals a significant earth slide with an active zone covering a surface area of 1.565 km2, extending approximately 2,166 km in length, with a width ranging from 40 m to 1.80 km, and a volume of 25,784,909 m3. Geomorphological field mapping results revealed a large and deep-seated morphological deformation related to: (i) the weak mechanical resistance and low stability slopes that the seismic strengths caused a reduction in the shear strength of the soil; (ii) Miocene clays, highly altered and potentially subject to shrinkage and swelling; (iii) a partial reactivation of a previously existing large landslide; (iv) human activity such as slope excavation and unplanned urbanization; and (v) topographical and lithological site effects. The results of geological and hydrogeological investigations indicated the presence of: (i) thin and thick weak-resistance interlayers of altered and plastic clays with weak resistance, which may constitute shear surfaces; (ii) a shallow aquifer that impacted the mechanical resistance characteristics. Laboratory tests revealed that the fine clay in the soil was highly weathered, with a low dry density and a high moisture content, along with a high saturation and plasticity, making it very sensitive to the presence of water. Undrained triaxial cyclic loading tests indicated a high potential for the generation of excess pore-water pressures in the material during seismic loading. The direct shear test showed that the disturbed soils had an average cohesion of 33.4 kPa/m2 and an internal friction angle of 18.21 degrees, indicating poor structural and shearing strength. The results of the oedometer test indicated that the soils are compressible to highly compressible, overconsolidated, and have the potential for swelling. According to the Manard pressuremeter test (MPT) and available empirical relationships, the landslide exhibited a deep-seated nature, with sliding surfaces located along weak geotechnical characteristics interlayers at a depth ranging between 10 and 40 m. The depths of failure obtained from the MPT were consistent with those determined by the empirical relationships available in the literature and numerical simulations. This comprehensive research provides valuable data on earthquake-induced landslide and can serve as a guide for the prevention and mitigation of landslide risks.

Rubble mound breakwater is a coastal structure, which is constructed to provide tranquil conditions in and around the port areas. Generally, the rubble mound structures are subjected to vigilant waves throughout the year. After the earthquakes of Kobe (1995), Kocaeli (1999), Tohoku (2011) etc. it is observed that the breakwaters can collapse due to failure of foundation and by seismic activity. Hence, in order to assess this problem, the current investigation deals with the study of rubble mound breakwaters and it is behavior against the seismic forces using numerical analysis. A finite element software PLAXIS is used for the numerical simulations. For study, a prototype has been selected and numerical model developed is a conventional rubble mound breakwater. In countermeasure model, the sheet piles in the foundation soil on extreme side of mound were considered. The numerical analyses have been done for constant seismic loading and soil properties. The parameters like vertical settlement and horizontal displacement were determined at different nodes. The vertical settlement was observed to be predominant in the crest region and it was reduced by 38% in countermeasure model. The displacement contours were significantly seen in core and armor units. The horizontal displacement of mound was seen by lateral movement of outer layers and it was 23% lesser for sheet pile reinforced model.