| A large amount of rammed earth sites have been saved in arid and semi-arid climatic conditions in Northwest,and these rammed earth sites reflect the development level of productivity in different periods and are important part of Chinese civilization.However,extreme environment in arid and semi-arid climatic conditions make open rammed sites undergo a process of disease development until disappear,so,how to protect scientificly immovable rammed sites has become a hot issue.Therefore,this paper starts with the environmental factors and carry out continuous real-time monitoring of 24 h for temperature,volumetric water content,dielectric constant and temperature and humidity of temperature of three rammed sites during precipitation in arid and semi-arid area.Based on the analysis of monitoring data during precipitation,the law of temporal and spatial response of the rammed site on rainfall process is interpreted preliminarily,Then,the sample curing condition is set up based on the above analysis results,and the strength test of cured samples is carried out,and finally the conclusions are as follows:(1)There are difference in response to precipitation of three typical rammed sites,the response rate from high to low is Shandan,Huangzhong,Yongjing.(2)Temperature from the different depth on the surface of rammed site s before and after the rain and snow has shown to the law of increasing,decreasing and increasing.The effect on the surface temperature for two kinds of precipitation was significantly higher than that of the internal,the response of the top of rammed sites to the environmental temperature changes in precipitation process was greater than that in other parts,secondly,the erosion area,the axis and the foundation.(3)Volumetric water content of each monitoring point of three rammed sites during the rain has shown to decrease gradually,but it has shown to the law increasing,decreasing and decreasing during the snow.In the process of precipitation,the response rate of volumetric water content to the environmental humidity decreases gradually from the surface to the core,the response rate of each monitoring point to the change of environmental humidity decreases gradually from both ends to the core.(4)Dielectric constant of each monitoring point of three rammed sites during the rain has shown to the law of increasingd and decreasing,but it has shown to the law of increasing,decreasing and decreasing during the snow.In the process of precipitation,dielectric constant decreases gradually from the surface to the core,the change rate of dielectric constant of each monitoring decreases gradually from both ends to the core.(5)Compressive strength,tensile strength and cohesion of remolded sample for same dry and wet,freeze-thaw cycle maintenance period,shows an overall decreasing trend with increasing salinity,while the internal friction angle increases first and then decreases;For the samples with the same content of Na Cl and Na2SO4 for the same period of time of curing,the strength of the former is higher than the latter,and the former was significantly lower than the latter for changes.(6)Tensile strength,cohesion and angle of internal friction of the remolded samples for same type and number of salt shows an overall trend of gradual decay with dry wet alternate freezing and thawing cycles increasing.When the cycle time is small,the tensile strength,cohesion and internal friction angle decreased greatly,the above strength index attenuation decrease with increasing c ycle times,the compressive strength and intensity attenuation is just opposite to the former.The above results fully explain the alternate coupling of dry-wet and saline,saline and freeze-thaw often caused by the interannual precipitation process is one of the main reasons for deterioration of strength of rammed earth sites in arid and semi arid area. |
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