The Thixotropic Properties On Loess Of Ningxia Tongxin

Loess is widely distributed in Northwest China, which is characterized by a wide distribution of depth, with many pores and water sensitivity. There are a lot of soluble salt in the Loess of Ningxia Province, and the soil structure is very easy to be destroyed, which has brought many new problems to the loess area. There are a lot of problems about the remolded soil in practical engineering, the current the characteristics of the structural strength and collapsibility of loess on the content of soluble salt which the study has a lot, but the quantitative research is less, and the degree of influence and regularity of various salt on the strength on loess are not systematic and clear. Based on..the above problems, this paper uses the soil mechanics test and the practical data of the project, put on a subject of the thixotropic properties of remolded loess is studied. By compared with the method of sampling which has press, and the compacted sampling method is selected. With water content w, dry density pd and age a as factors, uniform mixing test scheme is designed, using the regression analysis method was used to analyze the single factor effect and marginal effect and the coupling effect. With dry density ρd, water content w and salt content c as factors based on the age, the orthogonal test scheme of "four factors and five levels" was set up, the test results were analyzed by range and variance analysis method, and the mathematical model of the relationship between the parameters and the time was established. The results show that:(1) the uniformity of the remolded loess sampling increases with the increasing of the number of layers, and the effect of density is decreased, compared with the same layers of sampling, the press sanpling method has good uniformity. (2) Remolded loess structure strength and thixotropic parameters, along with the age growth early increases rapidly, the late increase slowly, and gradually stabilized, similar to a logarithmic relationship and strength determination of reasonable time node is about 14 days. (3) The structure strength of remolded loess, decreases with the increasing of water content, increases with the increasing of dry density salt content; the thixotropic parameters of remolded loess, increases with the increase of water content and salt content, decreases with the increasing of dry density. (4) The factors of remolded loess structure strength effect significantly, the order from big to small is dry density, moisture content, Na2SO4 content, CaCl2 content; the significance of various factors effect on thixotropic parameters, the order from big to small is water content, dry density, Na2SO4 content, CaCl2 content; the thixotropic parameters under the action of the double salt are bigger than the effect of the single salt. (5) The mathematical model established of structural strength of loess and the thixotropic parameters reached significant level, and each factor has a good correlation and prediction value is high credibility; regression model fitting parameters of the Tpu and b and the correlation, high degree of fitting and prediction model is accurate and reliable. The research results have important guiding significance for the design and evaluation of the loess foundation or roadbed.