Investigation of the seismic behavior of grouted sandy gravel foundations using shaking table tests

Sandy gravel foundations exhibit non-linear dynamic behavior when subjected to strong ground motions,which can have amplification effects on superstructures and can reveal insufficient lateral resistance of foundations.Grouting methods can be used to improve the seismic performance of natural sandy gravel foundations.The strength and stiffness of grouted sandy gravel foundations are different from those of natural foundations,which have unknown earthquake resistance.Few studies have investigated the seismic behavior of sandy gravel foundations before and after grouting.In this study,two shaking table tests were performed to evaluate the effect of grouting reinforcement on seismic performance.The natural frequency,acceleration amplification effect,lateral displacement,and vertical settlement of the non-grouted and grouted sandy gravel foundations were measured and compared.Additionally,the dynamic stress-strain relationships of the two foundations were obtained by a linear inversion method to evaluate the seismic energy dissipation.The test results indicated that the acceleration amplification,lateral displacement amplitude,and vertical settlement of the grouted sandy gravel foundation were lower than that of the non-grouted foundation under low-intensity earthquakes.However,a contrasting result was observed under high-intensity earthquakes.This demonstrated that different grouting reinforcement strategies are required for different sandy gravel foundations.In addition,the dynamic stress-strain relationship of the two foundations exhibited two different energy dissipation mechanisms.The results provide insights relating to the development of foundations for relevant engineering sites and to the dynamic behavior of grouted foundations prior to investigating soil-structure interaction problems.

APPLICATION OF TIME-VARYING VISCOUS GROUT IN GRAVEL-FOUNDATION ANTI-SEEPAGE TREATMENT

The time-varying viscosity of common grout and the controllable grout are measured with a rotation viscometer in experiments. The time-varying viscosity of grout is analyzed according to the characteristics in the process of anti-seepage treatment for gravel foundation. The principle of effective stress for porous medium is applied to analyzes the fluid-structure coupling in grouting. In the consideration of coupling physical variables, dynamic models of porosity, permeability and viscosity are constructed. The diffusion radius can thus be defined by the foundational porosity. The distribution of holes in field experiments is designed according to the diffusion radius of grout. Then, the permeability test is designed to verify the grout effect. The calculated diffusion radius coincides with experimental results, and the permeability meets the requirements of the project, which is valuable for the anti-seepage treatment in gravel foundation.