Processed tire wastes mixed with soils are applicable as lightweight fillers for slopes, subbases of pavements and retaining walls that may be subjected to seismic loads, e.g., earthquake or traffic loads. The dynamic response of granulated rubber-soil mixtures, such as the dynamic shear modulus, damping factors and liquefaction resistance, is essential in the design of such a system. This report presents the results of the dynamic behavior of granulated rubber-sand mixtures using resonant column tests and cyclic triaxial tests to assess the potential use of recycled rubber crumb in improving the performance of granular materials by mixing with different tire crumb sizes and fractions. Two contact types are identified that could explain the evolutionary behavior of the shear modulus and the damping ratio. The results of the rubber-sand mixtures are compared with the results from the literature. The mix ratio is shown to significantly influence the dynamic shear modulus and the liquefaction suscept...

Liquefaction of sand is the main cause of failure for earth structures during earthquakes. Some past research showed that the fabric anisotropy of soils in the ground can cause different responses to both static and dynamic loading. The inherent fabric anisotropy of sand due to the deposition history and pattern may also affect the liquefaction potential of the ground. In this study, a group of earthquake centrifuge tests was performed on models of a level ground to investigate its seismic response with the soil deposited by different angles. A special rigid container was designed and used to prepare the models. It was found that the fabric anisotropy greatly influenced the response of the ground in displacement, acceleration, and excess pore pressure. The models with larger deposition angles had higher liquefaction potential. The results show that liquefaction evaluation of a sand layer should take into account the influence of fabric anisotropy caused by its deposition history and pattern.

Suction bucket foundations are promising foundation options for offshore wind turbines, which are usually subjected to a relative high lateral-moment loading. To investigate the lateral-moment loading capacity of bucket foundations, a group of three-dimensional finite-element simulations with different bucket dimensions in both loose and dense saturated sand was carried out based on centrifuge tests. The numerical methods were validated by comparisons with the results of centrifuge tests and assessed by sensitivity analyses regarding the influences of soil properties and soil–foundation interface parameters. The interaction between the bucket and surrounding soil was illustrated in order to investigate the bearing behavior and failure mechanism of the bucket foundation. It was shown that in the ultimate state, the maximum passive earth pressure acting on the external skirt in the loading direction is approximately four times larger than that on the internal skirt. Furthermore, parametric studies on the L:D ratios (L is the skirt length and D is the bucket diameter) and loading eccentricity were conducted and discussed. Consequently, a modified calculation method was proposed to predict the ultimate lateral-moment loading capacity of bucket foundations and the method was validated by field and laboratory data.

Failure of foundations induced by earthquakes occurred many times in the past. There is a general lack of data recorded during earthquakes in the field about seismic response of such foundations. According to the results of some previous laboratory tests and numerical analyses, anisotropy of fabric of soil grains has significant influence on dynamic soil response. However, there is hardly any realistic physical data available to analyze the influence of fabric anisotropy on the response of foundations during earthquakes. Centrifuge tests are small scaled model tests which have been widely used to study the mechanism of response and to verify and validate design methods and numerical simulations. In this study, 12 centrifuge tests were carried out to study the effect of fabric anisotropy on seismic response of foundations. Important parameters in the response are evaluated and implications for design are discussed.

This paper evaluates the lateral performance of a monopile reinforced by a gravel wheel for offshore structures via centrifuge tests and three-dimensional finite-element (FE) modelings. The gravel wheel comprises a ring frame placed on the pile head and filled with large particles to potentially utilize gravel or crushed stone in offshore areas. The results of centrifuge tests and FE analyses demonstrate that the lateral loading capacity of the monopile increases when combined with a gravel wheel, and the improvement depends on the diameter and thickness of the wheel. By means of FE methods, the interaction between the pile and surrounding soils and gravel fill are illustrated to explain how the gravel wheel contributes to the lateral resistance of the hybrid system. Furthermore, an equivalent layer method adopting the conventional p-y curves is suggested to predict the lateral response of the hybrid foundation. This method is validated by comparisons with the centrifuge tests results. Finally, a case study of the monopile-gravel wheel foundation indicates that the gravel wheel is less efficient in configurations where the ultimate capacity of the hybrid system is dictated by the bending capacity of structures rather than the strengths of soils.

Offshore wind energy plays a major role in the long-term goal of relying on renewable energy. The demand for offshore wind energy is increasing rapidly in the world. However, the construction of offshore wind farm in seismic active areas has strict requirements for foundation selection and design. In this study, a group of earthquake centrifuge tests was performed on the wind turbine models with suction caisson foundation to evaluate the resistance to earthquake loading. The results showed that the seismic-induced lateral displacement and settlement of offshore wind turbine foundation can be mitigated by increasing the caisson diameter, skirt length, and weight of the foundation.