| As a precious cultural heritage,earthen sites contain many historical,scientific,cultural and social values.The special particle gradation properties of silt lead to the poor engineering performance of silt sites such as strong water sensitivity and low soil strength.At the same time,most of the silt sites exist in the open air environment.Under the influence of nature and human,many silt sites are seriously damaged and need to be repaired urgently.This paper takes the silt soil in a site in Kaifeng as the research object,improves it by mixing reinforcement materials,and seeks the best proportion of modified soil for the restoration of the site.The main research results are as follows:(1)Three kinds of silicone waterproofing agents were selected to modify the silt by single mixing,and the waterproofing properties of these three materials were compared and analyzed through capillary water rise and water disintegration tests.The three kinds of silicone waterproofing agents could improve the waterproofing effect of soil,among which 0.5% sodium methylsilicate modified soil had the most significant waterproofing effect,and the capillary water absorption inhibition effect could reach 98.34%,and the soil samples soaked in water for 24 hours were basically the same.Does not change.(2)The silt was modified by adding sodium methylsilicate and lignin fiber,and the mechanical properties of the modified soil were improved by unconfined compression and direct shear tests.Sodium methylsilicate can improve the cohesion and internal friction angle of the site soil,while the lignin fiber can significantly improve the cohesion of the soil,and has little effect on the internal friction angle of the soil.Comprehensive analysis determined that 0.5% sodium methylsilicate and 2%lignin fiber were the optimal ratio of composite materials,and the modified soil had good waterproof and mechanical properties.(3)Through the dry-wetting cycle and anti-scour test of soil samples,the durability performance of soil before and after modification with optimal dosage was studied.Compared with plain soil,the surface damage,mass loss and reduction of compressive strength of the modified soil samples are effectively controlled after drying and wetting cycles and scouring,and the stability of the overall structure can be maintained.The addition of it effectively enhances the durability of the soil in the natural environment.(4)The modification mechanism of the reinforcement material was analyzed by X-ray diffraction(XRD),scanning electron microscopy(SEM),energy dispersive analysis(EDS)and mercury intrusion(MIP)tests on the soil samples before and after modification.After adding sodium methyl silicate,the generated polymethyl siloxane film is attached to the surface of soil particles,making it hydrophobic,changing the contact mode of soil particles,reducing the pore size of pores,making soil particles more hydrophobic.The surface of the sample is denser,which improves the integrity of the soil structure;after adding lignin fibers,the lignin fibers are closely connected with the surrounding soil particles,thus forming a spatial network structure composed of the fibers and the surrounding soil,so that the fibers can share the soil.The external force to bear effectively increases the strength of the soil. |
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