Experimental Study On Effects Of PS Reinforcement For Silt In Moisture Circumstances

Preservation of the earthen sites with historical interests has become a worldwide hot topic, however, at present, there is no ideal reinforcement material to preserve the earthen sites in moisture circumstances. In recent years, a high modulus Potassium Silicate solvent (PS) which has been developed by Dunhuang Research Institute to reinforce the soil and rock relic sites in northwestern China, where the climate is dry. It has been found that the reinforcement effect of PS is good. However, there are no significant evidences to prove whether PS can equally reinforce the earthen sites in the moisture circumstances, moreover the effects of PS reinforcement has not yet been fully understood so far. This paper is focused on the effects of PS reinforcement on strength and deformation characteristics for unsaturated silt in humid climate by using laboratory test.The silt taken from the earthen site of Liangzhu is used to study the effects of PS reinforcement in terms of shear strength and deformation characteristics in unsaturated conditions by using direct shear tests and consolidation tests. Meanwhile, the mechanism of PS reinforcement on soil sites is investigated from the microcosmic view point by using the mercury injection testing technique. The main contents are as follows.First of all, the performance of the shear stress-shear displacement relationship curves is analyzed for the laboratory specimens with five different water contents both reinforced by 3% PS solvent or unreinforced by PS solvent. The analysis results show that the shear stress-shear displacement relationship curves can be classed into post peak-soften type and progressive hardening type. The relationship among the shear strength, vertical pressure and water content are also analyzed for the specimens with five different water contents both reinforced by 3% PS solvent or unreinforced by PS solvent. It has been found that the shear strength has been increased to some extent for all the specimens in the test, and the shear strength of the specimen with water content of 19% at the bottom has been largely increased by 50%.Secondly, the performance of compression curves is analyzed for the laboratory specimens with five different water contents reinforced by 3% PS solvent or unreinforced by PS solvent. It has been found that the water content in the specimen has significant effects on compression deformation. The pre-consolidation pressures, elastic compression index and elastic-plastic compression index are compared between the specimens reinforced by 3%PS solvent and the specimens unreinforced by PS solvent. It has been found that the ability to resist the compression deformation is improved to some extent for all the 3%PS reinforced specimens with different water content, and the elastic compression index of the specimen with water content 19% at the bottom has been largely decreased, by 50%.Thirdly, as the shear strength and the ability to resist compression deformation have been macroscopically improved for the specimens due to PS reinforcement, therefore the mechanism of the PS reinforcement is microscopically observed for the specimens both reinforced by 3% PS solvent and unreinforced by PS, by using the mercury injection testing technique. It has been found that the pore volume of the specimen has been increased by 16.2% after the specimens have been reinforced with PS solvent.These findings indicate that PS reinforcement technique is a promising method for the preservation of soil relic site in damp area.