Experiment Research On The Destroyed Mechanism Of The Saline Soil In The Great Wall In Shandan County

As a fairly common form of diseases in many earthen ruin sites of the Great Wall in the arid regions of Northwestern China, the backoff of wall bases can lead to serious collapse in the ruin. Therefore, correctly understanding the internal and external cause of this disease, and mastering the mechanism which leads to this disease have a scientific guidance to the prevention of these architectural heritages which may trigger more damages. Also, it could provide an effective and targeted theoretical basis for the site protection.It was found that the bases of the wall are salt Abundance Zones. After part of salts dissolves in water and the crystal volume contract, the salt crystals volume expands when the salts lose water. This process recurring regularly would undermine the framework of soil mess and, eventually, cohesion force and the strength decreased. Meanwhile, such soil damaged by salts crystallization in the Great Wall exposed in dreadful conditions in the arid regions of northwestern China, can easily be eroded and transported by wind notably by sediment-carrying wind. Presently, domestic and international scholars hardly analyze the backoff of wall bases of earthen sites systematically. Based on the recognition of above view, this thesis investigates the ecological environment character about the Great Wall in Shandan County. After adopting the original samples on the basis of choosing the typical study section and testing it in laboratory, Engineering Geological Properties of saline soil and non-saline soil was analyzed.After understanding the geological environment and physical and mechanics character about saline soil of Great Wall in Shandan County, this thesis carried on a test in laboratory aiming at testing the degeneration of these special soils by wind erosion. Firstly, acoustic test was carried out on the soil samples with salt of different content and types. After that, these soil samples were eroded by wind in blowing test under different type of winds, different wind speed and different deflation time. Finally, the rules of wind erosion of these soil samples were revealed by combining the microstructure by SEM. The results indicated that the test piece blended by sodium sulfate is harder than that blended by sodium chloride. Meanwhile, the test piece blended by sodium chlorid is easily deflated by wind than that blended by sodium sulfate. The resistance to wind erosion of the test piece blended by sodium sulfate rose with salt content increasing. Conversely, the resistance to wind erosion of the test piece blended by sodium chlorid declined with the increasing. Moreover, different type of wind affected soil samples in various ways. The wind without sediment-carrying hardly cause damage to soil samples, but the sediment-carrying wind, a leading external factor in erosion, can cause great damage to the earthen ruin.