Influence Of PS Consolidation On Permeability Of Unsaturated Soil From Earthen Sites

Recently, the anti-weathering consolidation of the earthen sites has been (a serious concern in geotechnical engineering. Potassium Silicate with modulus 3.8-4.0(PS) is widely utilized in consolidation projects of the earthen sites in northwest of China due to its favorable effect. However, some key technologies, such as infiltration properties of PS, permeability characteristics of unsaturated soil reinforced by PS and the effect of PS consolidation for the earthen sites, must be solved, which is important in popularizing the utilization of PS and increasing the effect of PS consolidation for the earthen sites.In this paper, through the combination of field tests and laboratory studies, the three key technologies mentioned above were systematically investigated with the soil obtained from the ancient ruins of Gaochang based on the theory and techniques of unsaturated soil. Three research contents are as follows:(1) The characteristics of PS infiltration were subjected to fundamental studies in the open environment under the similar soil condition with the earthen site of the ancient city of Jiaohe, the results of which indicated that low PS concentration (3%-7%) was similar with water in infiltration disciplinarian and infiltration velocity. And the infiltration experiments under unsaturated condition suggested that the permeability of PS was optimal when the water content of soil was 9%, and permeability of PS was very well until the water content was 15%. The soil sample reinforced by PS expressed higher shear strength than that without PS, and also expressed good water stability.(2) The soil-water characteristic curves (SWCC) of unsaturated soil reinforced with PS were studied by using pressure plate apparatus. It can be found seen from the curves that the saturated water content (θs) and residual water content (θr) decreased while the air entry value and the slope of the SWCC increased. It can be concluded that the main influencing factors of SWCC were mineral components, pore structure and shrinkage according to the reaction theory between PS and soil particles.The permeability experiments of PS were carried on in the lab and the coefficient of permeability of unsaturated clay was obtained according to SWCC and Mualem-Van Genuchten model. The results showed PS consolidation was advantageous to the permeability of the unsaturated clay and the permeability coefficient increased to some extent. The results of particle size analysis and XRD, SEM tests demonstrated that the original structures of clay, including laminated structure, the separation of particles, more edges and corners, changed to compact net structures, bigger particles, less edges and corners, lower degree of roughness and bending factor, higher effective porosity after consolidated by PS, which increased the permeability of soil samples.(3) Many tests including the disintegration test in water, simulation test of wind erosion and rain erosion, temperature fluctuation test, humidity variation test and freeze-thaw test were carried out, and these experimental results were conducted to evaluate the anti-environmental factors under simulation environment of real field environment variation and condition. The results indicated that the anti-environmental stability of soil consolidated by PS was several to several or ten times higher than that unconsolidated. It also demonstrated that it was feasible to consolidate the earthen sites with PS, which was useful to resist the adverse effect and to increase the consolidation effect of the earthen sites.