Static and dynamic behavior of sands treated with chemical grouts and cementitious admixtures.

摘要

Soil cementation, in which all or part of the void space between solid particles is occupied by artificial additives through admixture or grouting, is an accepted ground modification method for reducing the liquefaction potential of and improving stability of soils under dynamic loads. Soil treatment methods using cementitious materials have been applied to new construction or existing structures to minimize damage during earthquakes. However, there has been little formal research on the behavior of the soil undergoing dynamic loading, such as dynamic soil properties and liquefaction potential.; A series of tests of treated soils under static load conditions were included to study the static-drained and -undrained behavior. The highly non-linear response of treated soils under earthquake loads was investigated using cyclic triaxial test techniques. Dynamic soil properties, i.e., shear modulus and damping characteristics of grouted soil were investigated to assess: (a) the potential of soil treatment as a viable option in mitigation of earthquake hazards, (b) the response of existing treated soil structure systems to earthquake loads, and (c) the optimum treatment scheme for both admixture and chemical grouting treatment techniques. To investigate the effect of cementation on the liquefaction potential of cohesionless soil, the strain levels and the number of cycles associated with initial liquefaction also determined and compared to those of untreated soils.; Test results show that the general static and dynamic behavior of soils is improved with treatment with chemical grouts and cementitious admixtures. Particularly, it is found that: (1) addition of cementing material significantly reduces the liquefaction potential and cyclic mobility of sand by increasing the number of cycles and the magnitude of cyclic strength needed to reach failure; (2) shearing strain amplitude, grout type, and grout concentration have significant effect on the stiffness and energy absorption capacity of test specimens; (3) addition of flexible chemical grout greatly reduces prestrain effects often observed in untreated loose condition sand; and (4) increasing grout content or cement ratio increases the peak and steady state strength, and reduces the potential for volume change.