Development Characteristics And Influences Of Rammed Earthen Sites Basal Sapping Diseases

There remain a large number of earthen ruins in northwest China, and rammed earthen site is one of the most typical representatives. Owing to various types of land cover in northwest China, the development types and degree of basal sapping diseases in different regions are also different, which providing rich data for comparing and summarizing the influences of the formation and development of basal sapping diseases. Therefore, taking seven typical Ming Great Wall and Han Great Wall in Gansu and Qinghai provinces as investigation objects, basing on the investigation and statistics of basal sapping disease and the results of salinity field observations, combing laboratory tests, synthetically analyzing the existing environment of rammed earthen sites, the engineering characteristic and the building system of earthen sites, studying developmental characteristics of,basal sapping diseases, summarizing the influences of basal sapping diseases, broadly comparing the differences among different areas, hoping to offer a theoretical basis for the protection and rehabilitation works of rammed earthen sites in northwest China.The research results showed that:(1) Among all the basal sapping diseases across four continents climates, basal sapping disruption-induced and freeze thawing-induced basal sapping diseases mainly occur in semi-arid area and semi-arid and semi-humid area, wind-induced and collapse-induced basal sapping diseases mainly occur in extremely arid area and arid area, the development of running water-induced basal sapping diseases has particularity;(2)The method of simplifying undercutting areas forms to types to two kinds cylinder graphics rules--arched cylinder and half-arched cylinder makes for quantitative calculation and computational accuracy;(3) The main seven climatic factors affecting the developing of basal sapping diseases from large to small are, by weight, mean annual temperature, elevation, annual rainfall, annual potential evaporation, annual solar radiation amount, monthly mean wind speed, daily temperature range;(4) parameters closely related to the growth and development of basal sapping diseases such as drought index is very sensitive to the amount of basal sapping, basal sapping rate, soluble salt content in undercutting area and vertical migration rate of the soluble salt;(5) The influences of building system on basal sapping diseases are the wall with relatively thin ram layer and short spacing among adjacent walls are more likely to generate basal sapping;(6) The influences of engineering geology characteristics on basal sapping diseases are the more the fine silt content is, the more severe the wind-induced basal sapping diseases are, and the fast the disintegrating speed is, the worse the mechanical property(shear strength, compressive strength and tensile strength) is, the more severe the basal sapping diseases are;(7) Among the three categories factors affecting the development of basal sapping diseases, climatic factor is in the dominant position.