The Research On The Loess Collapsibility Of The First Subway In Xi'An

Loess is the mother material of agricultural soils, and is the main geological basis for various engineering and construction activities in the loess area, which has a very close relationship between the people's daily lives and national economic construction. Due to the special nature of the loess, Soil erosion, Foundation collapsibility, reservoirs slope, road cutting and the Loess Plateau edge collapses, landslides and other catastrophic geological activities occurred frequently in the loess area,therefore, study on the engineering properties of loess is an important topic in loess region.Loess in nature is special because it was formed in a special natural environment, water has a special sensitivity-collapsibility, many engineering problems are resulted of which directly or indirectly. Thus the collapsibility of loess study appears to be particularly prominent and important. Xi'an built subway in the loess area firstly, so it is very important to conduct a study along the collapsibility of loess,in this paper, Author use Xi'an Metro Line of geotextile materials for the study of collapsibility,by which,we could gain a theoretical basis and guiding significance for the city subway tunnel construction and the construction of surrounding and buildings.In this paper, conducted four-part study as follow:The first part:the impact of loess collapsibility of the factors were analyzed and summarized, in a number of factors, the greatest impact on the collapsibility of loess is the natural moisture content, void ratio and plasticity index, the three physical indicators selected in this paper to describe the Loess The coefficient of collapsibility.The second part:the application of Xi'an Metro Line of geotextile materials, its along the loess, to analyze the relationship between the coefficient of collapsibility and physical indicators in different landscape units, and among them are given a mathematical expression, on this basis is given to predict loess collapsibility coefficient mathematical model.The third part:firstly discussed the three parameters of the first model,and described their represently significance and the relationship between each others. a1+3i,a2+3i, a3+3i representing the water content, void ratio, plasticity index of the coefficient of collapsibility affect weight. the relationship between the three is a1+3i+a2+3i+a3+3i=1. secondly, under a different landscape units, based on void ratio range of different loess, spreadsheet on the first prediction coefficient of collapsibility of the model,and presents a1+3i, a2+3i, a3+3i the specific values when the range of void ratio differently at the same time, And to draw on the same kind of landscape units, a3+3i is a constant, and thus can draw the specific expression on a variety of landscape units of loess collapsibility coefficient.The fourth part:using the application of this model calculated coefficient of collapsibility and presented in this paper determine the method, the types of venues and foundation collapsibility level of seven stations along the subway line has been divided, and concluded that the new method in this paper is reasonable compared with the results which were conducted by the traditional method Venue collapsible type and the wet ground subsidence levels.This prediction model has been further improved and more rationalization on the basis of our predecessors, and supports more in-depth research help on the loess subsidence prediction model, accordingly, has important theoretical and practical significance.