Experimental Study On Deformation Of Saturated Sand Under Cycle Pore Water Pressure

Wave load is one of the important loads in ocean engineering, which is the most frequent load in the sand foundation of offing. And also it is periodical and dynamic load. Acting on the submarine soils, wave load can induce the change of pore water press. With the raising of the pore water pressure, the soil effective stress will be decreasing, which may lead to the damage of soil mass. Therefore, it's very important to study the mechanical behavior of sand soils under the action of cycle pore water pressure for coast and offing engineering.Based on the result of consolidated undrained triaxial test of Fujian Standard sand, the parameters of ratio of consolidation stress, relative density and frequency obviously effect on deformation of saturated sand under cycle pore water pressure produced by water pressure controlling instrument, which are studied respectively. The experimental result indicates that the specimen has a large deformation when the parameters of ratio of consolidation stress, frequency are higher and the specimen has a small deformation when the parameter of relative density is higher.The concept of dynamic pore water pressure coefficient is defined. Based on lots of test data, the curves of strain and dynamic pore water pressure coefficient are figured and analyzed. By analyzing the characteristics of the curves, three variation processes and two critical constants could be found. In the condition of the certain ratio of consolidation stress and cell pressure, the specimen has a visible deformation when the cycle pore water pressure comes to some a critical constant; the specimen has a invisible deformation when the cycle pore water pressure is less than some a critical constant; and the specimen has a faster deformation when the cycle pore water pressure is greater than some a critical constant.Finally, effective stress principle is applied for analyzing the specimen deformation under cycle pore water pressure. Curves of total stress and time, of cycle pore water pressure and time, of effective stress and time, of effective stress and axial strain are respectively studied.