Study On Treatment Technology For Soft Foundation In The Loess Ravine Regions

The soft ground in the loess ravine regions has special engineering properties which are different from the soft clay in littoral and the slumping loess. In the past, some researches were carried out to find out its characteristics based on the engineering practice in the Guanzhong alluvial plain. Its system info has not been built so far yet, the results were only located in idiographic project, which is hard to put them into generalization. In this paper, on the basis of plentiful productive practice in Huangling-Yan'an expressway, and the research results from Guanzhong alluvial plain regions as well as those from domestic and foreign, the treatment technology of soft ground in the loess ravine regions were analyzed and generalized.The physical and mechanical property of soft ground in the loess ravine regions has been analyzed deeply and systematically. On the basis of many aspects such as distributing, geological structure, cause of formation, grain size and its composition, the definition of the soft ground in the loess ravine regions was set up, its engineering property was described, and variety range of its familiar parameter was also presented. According to the statistical relationship between its familiar parameter and the admitted canying capacity, the empirical formula between the admitted carrying capacity of this kind of soil and liquidity index,the coefficient of compressibility, or and the modulus of compressibility were established.The common treatment methods to the soft ground in the loess ravine regions have been analyzed based on a great dead of in-situ soil test, settlement measurement and numerical simulation. The overall principle of soft ground in the loess ravine regions was also summarized. Because of the long and narrow terrain and the characteristic of highway engineering, the camion was used as counterforce device in load test. The compared analysis between it and other test data showed that this method is suit for the loess ravine regions. Its flaw presented in the test was analyzed and improved.The settlement of soft ground in loess ravine regions has many effect factors. So the method which based on case-based reasoning integrated with neural network was use to predict its settlement, which take the randomness and uncertainty of effective factors into account, as well as the successful experience in similar project. A new similarity calculation method was defined, through a new kind of utility function to let this method to show the distance and difference between the target case and the base case better. Finally with the simulation of neural network the prediction will approach the actual more. The calculation results showed the errors between the calculated and the measured was no more than±10%.After analyzing deeply the factors considered when select soft ground treatment scheme, some extension sets theory was introduced in the old AHP method, which make the judgment matrix fit the consistency condition automatically, so as to avoid a great deal of calculation work effectively. The extent AHP method take fuzziness of people's judgment and engineering experience of more than one experts into account. The application in the Huangling-Yan'an expressway shows that this method is clear in conception and easy to put into practice.The basic principle of soft ground treatment in loess ravine regions was presented. The suitability of common treatment method of soft loess was generalized, as well as their requirement of quality control. At the same time the basic considered factors and the compositive treatment technology of this kind of soil were presented. The diseases after construction and their causes of this kind of soil were studied widely, their prevention measures were put forward.