The Study On The Engineering Properties Of Q₂ Loess In The Case Of The Moistening And Demoistening In Yan’an New District

The engineering program in Yan’an New District is a land reclamation project,which levels the hilly and gully terrains in Yan’an New District. Infrastructures are to be constructed after the reclamation process. And Q₂ loess will be the main foundation soil layer of the construction project. Thus the study on the engineering properties of the project has great significance. This topic comes from ‘Key technology research and demonstration of engineering construction in Loess Hilly and Gully Region（Yan’an New District）’ of the ‘12th Five Year’ National Science and technology support plan. It is based on the high fill project of Yan’an New District, and the research object is the original Q₂ loess of the reclamation area. This paper intends to study the change of engineering properties of Q₂ loess in the case of the moistening and demoistening. It is to provide technical support for the construction of Yan’an New District.Q₂ loess has the properties of deformation and strength. In order to study the variation trends of it in the case of the moistening and demoistening, this paper summarizes the previous research results and status, and analyses it in both theory and experiment. By using the method of pre-wetting to realize the moistening and demoistening condition of the original Q₂ loess, the experiments of High Pressure Consolidation Test and Triaxial Shear Test were carried out. According to the analysis of the test data and results, for the deformation properties, a more matching stress-strain model and its corresponding load- secant modulus model were established. The function relation of the original O2 loess’ s stress-strain-water content has been developed, as well as the relating curved surface of the moistening and deformation.Based on the secant modulus method, the calculation method of soil deformation in the case of moistening and demoistening was obtained. For the strength properties, function relation of the water content of soil mass, its shear strength and the soil mass confining pressure was developed. And then a curved surface of its corresponding soil strength was described. Based on the theory of the strength of the Moire- Kulun, the function expression between the soil strength index and the soil water content was established.Through combining the obtained conclusions respectively with engineering practices,and applying to the calculation of the shallow foundation deformation and the calculation of the ultimate bearing capacity of the foundation, the feasibility of the method is verified by the results compared with the commonly used calculation methods.