单桩基础在非饱和砂与饱和砂中的水平加载响应对比OA

Large-diameter monopiles are prevalent foundations for offshore wind turbines.Most experimental studies on the lateral bearing behavior of monopile foundations are currently conducted in unsaturated sand,whereas the seabed soil is saturated.Therefore,it is necessary to investigate whether the response of monopile foundations in unsaturated sand can reflect their true characteristics in saturated sand.To this end,two series of comparative lateral loading model tests on monopile foun-dations were conducted in unsaturated and saturated sands,with each series including one monotonic loading and two cyclic loading conditions.The lateral load was applied to the extended upper section through a servo motor and transferred to the monopile foundations.The test results indicate that the monotonic lateral response of monopile foundations in unsaturated and saturated sands is relatively similar,but considerable differences are observed under cyclic loading conditions.In unsaturated sand,the presence of matric suction causes the soil around the pile to gradually form gaps under cyclic loading conditions,resulting in a pronounced degradation of pile-soil stiffness.Meanwhile,in satu-rated sand,soil fissure development is not pronounced,and the cyclic degradation effect of pile-soil stiffness is insignificant.The findings reveal the causes of the cyclic degradation effect in sand,which can reduce the design cost of offshore wind turbine foundations in saturated sand and hold paramount implications for practical engineering.