Experimental Study On The Effect Of Salinity On The Degradation Mechanism And Properties Of Rammed Earth Materials

Fujian tulou is located in the southeast coastal area of China,which has a long history of rammed earth structure after long-term environmental changes,leading to soil development of various diseases.The fundamental reason is that the deterioration of soil rammed earth lead to a decrease in damage of the outside world.Abundant rainfall and sunshine,such as the alternation of wetting and drying,exacerbated the salinization of soil,salinization of soil is one of the typical engineering geological problems.Therefore,strengthening the research of salt effect on tulou’s rammed earth materials,with scientific guidance for the prevention of the occurrence of greater deformation and damage of earth structure.After the field investigation on multiple tulou groups in Fujian Yongding,we observed the damage of the rammed earth wall,and collected the dismantled rammed earth wall back to start the salt determination,on the basis of this determination,to selected the reasonable salt content and categories for the desalting soil and then make experiment blocks to carry out rammed earth blocks of the saline degradation experiment.Not only provides certain reference value for the study of earth protection,but also provides the effective theoretical basis for the protection of cultural relics in similar soil sites.Through the determination of anion and cation content of soluble salt from original rammed earth blocks,and determine the type and content of salt,can determine the status and dynamics of soil salinization salt.It is regarded as the utilization of saline alkali soil classification as the basis for amelioration,prepared blocks which is similar to the original soil salinity content with NaCl,Na₂SO₄,CaCl₂ and compound salt（Na₂SO₄+CaCl₂）,and according to gradient to increase the content of soil.The compressive strength experiment and shear strength experiment after the alternation of drying and wetting,recognize different categories and salt content cause the degree of saline degradation of rammed earth materials.Tested the physical properties of rammed earth materials and analysis of characteristics of soil by soil experiment.Salt experiment results show that the soluble salt content distribution in theoriginal earthen blocks between 0-2%,salt content of the bottom walls and at the doors and windows higher significantly than the top of the wall,Ca²⁺,Na⁺,Cl^-and SO₄^2-as the main ion content.Strength experiment results show that after the soil degradation in saline,with the increase of salt content,cohesive strength and compressive strength of samples decreases,the angle of internal friction shows the changing pattern of growth and then decreases;samples containing Na₂SO₄ salt is more serious in degradation than the sample degree of NaCl salt content,the same on the mechanical properties;samples with Na₂SO₄ obtained cohesion compared to CaCl₂ containing salt of samples,but the angle of internal friction is the opposite;adding salt complex（Na₂SO₄+CaCl₂）of the soil samples,the compressive strength is stronger than the first two kinds of salt at the first,with the increase of salt content,the strength to decrease below the two single salt,also the cohesion,and the surface with crystal precipitation.Regression analysis was used to analyze the correlation between the strength parameters of soil and the content of salt,the types of salt,finally,conclude a valuable model.