The Salt Damage Characteristics And Prevention Of Rammed Earthen Sites In The Northwest Of China

There are many earthen sites in northwest China,and the repeated dissolve and crystallization of salt in the earthen sites is a major deteriorated process,leading to the base erosion of the earthen sites,which eventually leads to the collapse of the earthen sites.At present,there are relatively few studies focus on salt damage in earthen sites,and there are even fewer studies on the characteristics of salt damage in earthen sites.The number of studies on the characteristics of salt damage determines the lack of prevention of salt damage in the consolidation of earthen sites,which seriously hinder the improvement of the conservation ability of earthen sites.Based on geology,soil mechanics,climate,hydrology and inorganic chemistry,used the thermal infrared imager,nondestructive testing equipment such as 3 d scanner,and the electron microscope,XRD,ion chromatography and other advanced equipment,with the DIY equipment and devices for indoor and field test,the salt damage characteristics of earthen sites were studied in the region of northwest China,salt damage prevention and control method is proposed.The earthen sites in northwest China located in extremely arid and arid regions.there are many kinds of soluble salts in the earthen sites,and earthen sites are susceptible to sulfate.During capillary rise,sodium chloride solution has a fast rate,and a relatively heavy salt crust is formed on the surface of the sample during evaporation and crystallization.At the time of capillary rise,the speed of sodium sulfate solution was the slowest,the crystal was cotton-like,and individual crystals grew like elongated cotton thread.The crystal grew from the inside to the outside,and the destruction was carried out from the lower part of the soil surface of the site.The height of the capillary rise is about 10cm in the earthen sites in northwest of China.Soluble salt destroys the site under the capillarity rising and evaporation,and the damaged soil falls on the base,then the capillarity rising repeatedly destroys the site base under the leaching effect of rain.Field simulation test shows the mechanism of base erosion of earthen sites in the northwest of China.Due to the sodium sulphate,exfoliation appeared on earthen sites wall,and base erosion came about at the root.The earthen sites contains a large amount of soluble salt,but the occurrence of salt damage in the soil site is not only related to salinity,but also related to the environment of the sites.By salt damage threshold test,this paper put the northwest arid area earthen sites of salt damage degree and rainfall and the salt content of different classified as severe,moderate,mild,weak four grades,and the reinforcement of earthen sites for the soluble salt content of the proposed value:the total salt content is less than 0.3%,u ~U?1300mg/kg,~U?900mg/kg,when these three items to meet at the same time,the salt damage degree is weak.By blocking water salt capillary rise test,compared the gravel,geotextile and rammed earth isolated layer,evaluated the blocking effect of the capillary water rise,because of its large pore distribution,good to prevent the effect of capillary rise,as well as good permeability and physical and mechanical properties.It is suggested that in the case of the need to cut off the water salt capillary rise in the protection and reinforcement of earthen sites,the gravel isolated layer is prior.In this paper,the salt damage characteristics of earthen sites in northwest China are studied.The threshold of soluble salt content in soil is presented.It is proposed for the first time that the gravel layer is used to block the rise of water salt capillarity in the protection and reinforcement of earthen sites,so as to prevent the salt damage.In addition,in this paper,a special device for the study on the rise of water and salt capillarity of soil cultural relics was developed,and the degradation of earthen sites was studied by three-dimensional scanning combined with weighing method,which provided a good research device and non-destructive testing method for the study on the protection of earthen sites.The research in this paper provides important scientific support and methods for the protection and reinforcement of earthen sites in northwest China's arid regions,which can also be well applied to the protection and reinforcement of many earthen sites along the silk road.