Research On Highway Engineering Geological Division In Collapsible Loess Areas

Gansu, located west of the Loess Plateau,is an important accumulation of loess ground in China. Loess, distributed widely and big thickness,collapsible loess in different regions, different times and different causes,have a large difference in collapsible, compressibility and carrying capacity, etc.Especially the unique loess collapsible cause many diseases highway to Seriously affect the development of traffic safety and highway construction.At present, our province is still in the stage of rapid development of the construction of highway,by combing summary preliminary and other highway survey, design and construction of data and related outcomes,relying on the current highway projects beening completed in loess area.There are important practical significance to study loess engineering geological characteristics of different regions,such as guiding the subsequent construction of highway project,improving the quality of the project,extending the life of the highway.The main ideas and contents are as follows:(1)Summarize and analyze the research results of subarea loess in geoscience circle and construction industry. Make statistical analysis on highway engineering indoor physical mechanics parameters, collapsibility variation law in different geomorphy and depth, collapsibility grade and various fields’ collapse settlements.(2) According to the analysis of the loess physical and mechanical index, make a comparative analysis of each area by adopting moisture content index,specific gravity, plasticity index, void ratio, compressibility, coefficient of collapsibility. At the same time, according to the engineering characteristics of every index, make variation rules analysis of Gansu loess distribution area on loess material composition, structural features and compression properties, as well as the collapsible sensitivity by using plasticity index, void ratio, compressibility, coefficient of collapsibility respectively.(3) In order to preferably show soil’s collapsibility relation with other physical mechanics indexes, dry density, void ratio and moisture content are taken as analysis index to obtain different index and coefficient of collapsibility’s univariate linear regression equation, then find out linear degree of close relationship among each index, and set up regression equations that linear degree is above middle level.(4)Make loess engineering geological zoning principles and rules. Make primary subarea in Gansu loess area from the aspect of geologic structure, stratigraphic distribution and large size physiognomy characteristics; make secondary subarea in loess area from the aspect of material composition and geologic structure by using plasticity index, void ratio and middle-sized physiognomy;make third one in a respective from small size physiognomy degree and depth of loess collapsible sensitivity.(5)As per partition results, provide each partition soil’s detailed physical mechanics parameters in different depth and physiognomy and set up regression equations that linear degree is above middle level, which are taken as corresponding collapsibility evaluation equation.By collapsible geological zoning of highway engineering in Gansu loess area, work out "Map of highway engineering geological zoning of Gansu collapsible loess area", " evaluation table of collapsibility of each subarea’s collapsible loess highway engineering", "statistical table of physical mechanics parameter of each` subarea’s collapsible loess", which enrich and perfect research results of Gansu collapsible oess area and make reference for other industry’s construction.