Study On Physical And Mechanical Properties Of The Interface Between Sacrificial Layer With SH As Admixture And Rammed Earthen Sites

The earthen sites are carriers of long history and splendid culture,and they are important basis for studying the origin and development of Chinese civilization.However,due to the characteristics of building materials and the influence of the surrounding environment,the earthen sites have suffered from weathering for a long time and are in urgent need of protection.As a new method to prevent weathering of earthen sites,sacrificial layer can replace the destruction of the site itself,so as to play a protective effect.SH can significantly improve the physical and mechanical properties and durability of soil and meet the relevant requirements for the protection of earthen sites.It can be used as an anti-weathering material for earthen sites,but there is relatively little research on the interface between sacrificial layers and the earthen site itself.In this paper,SH was used as admixture to study the physical and mechanical properties of the interface between sacrificial layer and rammed earthen site.Firstly,the shrinkage characteristics of sacrificial layer with SH as admixture were studied,and the changes in water content and porosity ratio of saturated specimens during the drying process are explored to investigate the water migration and shrinkage process.Then,the physical and mechanical properties of the sacrificial layer and earthen site interface were studied through color difference evaluation,surface hardness,water vapor penetration test,direct shear test and organic carbon detection.Finally,wet-dry cycle and freeze-thaw cycle tests were carried out to study the durability of the interface between sacrificial layer and earthen site.The following conclusions are drawn:(1)The initial moisture content and SH significantly affect the shrinkage performance of the sacrificial layer.Radial shrinkage is primarily determined by the initial moisture content,while axial shrinkage is mainly influenced by SH.An increase in the initial moisture content results in greater radial shrinkage of the specimens,while the SH suppresses the axial shrinkage of the soil.The volume shrinkage of the specimens is a comprehensive performance of radial and axial shrinkage.(2)SH has an impact on the chromaticity and surface hardness of the sacrificial layer.When the content of SH exceeds 0.6%,the color difference does not meet the requirements for the protection of earthen site,but the hardness remains above 92 HA.The presence of SH and the dry density of the soil in the sacrificial layer influence the transmission of water vapor in the soil,and they have opposite effects on water vapor permeation.The vapor permeability coefficient of the dual-layer medium consisting of the sacrificial layer and the remodeled soil is influenced by the two layers.Utilizing the calculation formula for the equivalent permeability coefficient of layered soil provides relatively reliable results.SH has a dual effect on the interface between sacrificial layer and earthen site.On one hand,it weakens the occlusal effect between particles at the interface,while on the other hand,it can play a cementation effect.The changes of cohesion and internal friction angle are the combined result of their mutual interaction.(3)During the freeze-thaw cycle,due to low initial moisture content,the samples show freeze-shrinkage and thawing expansion phenomenon.This affects the interfacial durability through the occlusal forces between soil particles,the interaction between SH and soil particles,as well as the propagation of microcracks.During the wet-dry cycle,the interfacial durability is influenced by factors such as matrix suction,aging effects,capillary condensation,and soil microstructure.The dry-wet cycle experienced by the soil is actually a fatigue process of soil particles under the continuous change of matrix suction.The aging effect in the process of moisture absorption can enhance the strength of the soil,while the capillary condensation can increase internal friction angle of the specimen.Compared with the sacrificial layer without SH,the samples with0.6%SH content in the sacrificial layer still have higher freeze-melt resistance and drywet resistance after the cycle.(4)The higher the wetting degree of the surface of the remodeled soil,the better bonding effect between the sacrificial layer and earthen site.Based on a comprehensive evaluation of various indicators,the optimal wetting degree for the surface of earthen site is slightly below the plastic limit,and 1.3 times liquid limit water content and 0.6%SH are considered to be the best ratio for the sacrificial layer.