Study On The Influence Factor And Formation Mechanism Of Binary Structure On Scaling Off Surface Of Rammed Earth Ruins In Arid Area

Scaling off is one of the most widespread and typical deterioration types existing in the earthen sites distributed in arid regions,which is an important slow extinction model for a close relationship between earthen sites and precipitation.According to the investigation and counting of morphological characteristics of scaling off existed in 18 different climatic zones,the largest linear earthen sites of Ming Great Wall in Chinese arid region,it initially puts forward that the scaling off of earthen sites has binary structure and determines the eigenvalues of scaling off by combining with experimental results of laboratory experiment from each place and layer.Extracting the main influencing factors of scaling off by regression analyze and grey correlation entropy between eigenvalues of scaling off and the factors of environments and rammed earth.It have been initially elucidated salt differentiation and uneven shrink,which are two significant mechanism of the formation and development of binary structure characteristics of scaling off of earthen sites made of rammed earth.What is more,the factors of environments and rammed earth have been proved to affect the formation and development of scaling off in control.This research provides meaningful references for the in-depth study and scientific prevention of development mechanism of scaling off existing in earthen sites.The results of the study are as follows:(1)It was found that the scaling off showed an increasing trend from the top to the bottom of wall and the scaling off of sorthern slop is more serious than the northern slop by studying the scaling off characteristics about 18 Ming Great Walls in Northwest China’s arid area.It also found that scaling off has layer phenomenon by observing profile characteristics of scaling off.(2)It initially puts forward that the scaling off of earthen sites has binary structure by combining with experimental results of particle size analysis,porosity,and soluble salt content of samples from each place and layer.In this paper,the first layer of soil with a high content of clay particles and colloidal particles,a low porosity and easily soluble salts is defined as a shell layer;the second layer of soil with higher particles,porosity and soluble salt is defined as a silty layer.The third layer of soil is defined as bauxite layer,in which,shell layer and silty layer together constitute a peeling layer.(3)The factors of environments and rammed earth are determined about scaling off by reviewing the relevant literature and research on the habitats in the study area.In this paper,the dominant peeling area,the thickness of shell and peeling layer were defined as thepeeling eigenvalues.The regression analysis between the factors of environments and rammed earth and peeling eigenvalues found that there are certain correlations between the influencing factors and peeling eigenvalue.(4)Based on the grey relational entropy analysis mathematical model,the correlation between the factors of environments and rammed earth and peeling eigenvalues was discussed.It was concluded that the response of rammed earth factors to peelings eigenvalues was greater than the environmental factors,indicating the internal influence factors play a major role in the development of scaling off.(5)It has been confirmed salt differentiation and uneven shrink,which are two significant mechanism of the formation and development of binary structure characteristics of scaling off of earthen sites made of rammed earth,it has been initially elucidated through experiments of particle size analysis,shrinkage limit of water content of rammed earth from each place and layer under different conditions,and conjoint analysis between the morphology,granulometric composition,salt eigenvalue and characteristics of environmental and rammed earth factors.