Experiment Study On Salinized Deterioration Of The Saline Ancient Relics Soil Under Dry-wet Cycles

A large amount of precious relics of ancient earthen architecture sites have been saved under arid and semi-arid climatic conditions in Northwest, such as the Great Wall and the Jiaohe Ruins. These precious cultural heritages which are of extremely important, not only representative the achievement of wisdom, but also the historical evidence of the development process in political, military, scientific, cultural and economic. The reduction of the capacity to resist external damage is the root cause of the development of various diseases in soil site, which at the long-term adverse climate change in extreme environment. Evaporation of rainfall and a strong focus on climate change increased the wet and day cycles and salinization of soil, the latter becomes the typical engineering problems of soil sites in Northwest. Above all, concentrating on the research of wet and dry cycles of soil salinity on the soil site to prevent more damage to the heritage has a great significance, what' more, the research can provide effective theoretical basis on the protection of cultural relic.Choosing a reasonable salt content, the purpose is to do research on salt saline soil degradation test site by wet and day cycles under a premise of qualitative understanding to the soil salinity of sites in Northwest region. First, we may have a more intuitive understanding of influence about different types and contents of salt on soil saline by direct shear test, unconfined compression test and tensile test on various salt types and contents test blocks after three wet and dry cycles; Second, the process of soil salinization deterioration may display from a macro point by doing acoustic experiment to test changes in the structure of soil sites contained with salts under wet and dry cycles; Third, we could establish relationship with micro-structure changes and carry out intensive study on effect of wet and dry cycles on the site of degradation of soil salinization in micro point by reveal the mechanical properties of soil salinity sites and the intrinsic link between the micro-structure of the various parameters.The follows are positive results:1. The mechanics performance testing of the test sample after salinized deterioration shows:With the increase of salt content, the cohesion of the sample, compressive and tensile strength decreases, the internal friction angle of the show is decreases after increase; The sample mixed with Na2SO4 salt deterioration far more serious, compared to the sample adding NaCl salt, its mechanical properties is reduced; Because the existence of NaCl salt, causing the solubility of Na2SO4 reduced significantly, and crystallized early, make the surface strength of the samples mixed with complex salts between incorporation of a single salt while the strength of entire sample is the lowest.2. Acoustic test results show that:Compared with one Dry-Wet cycle, the longitudinal wave of samples decreased by 10% after three cycles, and reduction is increased gradually with the increase of the salt content, from the side confirmed to the salinized deterioration of the ancient relics soil by dry-wet cycle; After regression analysis found that power exponent relationship between longitudinal wave and compressive, tensile strength, the relationship between the longitudinal wave and shear strength is discreteness.3. By microstructure observation, granular Na2SO4 and needle like NaCl are exist in the pores. The type of microstructure change from the matrix to the skeleton-like as the increase of salt content, what is more, the highlight of the surface of soil particles increased and the particle size tends to homogenization, whereas the overall structure is loose. Using multiple regression analysis, we will get certain reference value obtained regression equations and models after analysis of soil salinity deterioration of mechanics strength and the correlation between parameters.