Loess Slope Selection Of Strength Parameters And Application

It is essential in slope stability analysis to get a set of reasonable strength parameters of the soil. Presently, the parameters tested are generally necessary but difficult to be used in actual engineering. The main problem is disturbing of the samples and changing of the origin stress state in the process of sampling, transporting and testing. By contrastive analysis between strength parameters inversely calculated and parameters tested, the author suggests a way of choosing strength parameters, and according to these strength parameters, worKs out the basic parameters of designing loess slope, which is based on abundant local landform surveying data of loess landslide and limit slope. The main achievements of investigation and research by author are as follows:1. From the north to middle of Shanxi Province along 210 highway, according to the diversity of natural and geographical conditions and the loess's engineering characteristics, the survey zone is divided into three sections. The author has surveyed the typical cross sections of limit slope and the landform outline of old landslide. Original landform of old landslide is recovered, and the main section of recovered slope is also treated as limit slope, which has established geological model for inversely calculating of slope parameters. By large quantity of statistic analysis of limit slope, the correlative relations between height and gradient of slope in respective sections are elicited.2. While surveying, undisturbed soil samples from typical cross-sections of slope and landslide were also collected and indoor tests have been done to get the ordinary physical and mechanical indexes and direct shear test and tri-axial test under three different drainage and consolidation conditions also been done to get the strength parameters. By statistic analysis to test data, the regularities of spatial change of various soil parameters and the effects mat testing methods and testing conditions impact on strength parameters have been elicited. The total characteristic is that the variability of the c value is comparative high, that of the φ value is very low and under different testing methods, the variability of c value is big, that of the φ value is small.3. According to Bishop method genarally used in engineering, parameters' inversely calculating model has been optimized. Slice method is optimized to be integral method that avoids the inconvenience of artificial slicing. Considering the uncertainty of sliding surface of slope when inversely calculate the slope parameters, a search method for the most dangerous sliding surface of slope has been elicited. And by programming, the function ofstability calculation and parameters' inverse calculation has been realized. The calculation results indicate that when calculate stability factor of slope, the most dangerous sliding surface corresponds to the minimal value of stability factor and when inversely calculate the parameters(c or d>) of slope, the most dangerous sliding surface corresponds to the maximal value.4. When the improved model in this thesis is used to inversely calculate the limit slope, the strength parameters of inverse calculation could be considered as "truth value" or near to "truth value". Comparing the result of inverse calculation and the testing result indicates: the result of direct and fast shear test is nearest to inverse calculation. The inversely calculating result involved in this thesis is used to correct various testing results, and those inversely calculating parameters are used to calculate the corresponding design gradient of slope as given height and stability factor, and offer references to the design of slope. Compared with the methods and parameters used in present engineering, the choosing method of strength parameters of slope that is elicited in this thesis is logical, and the parameters of slope are approximately credible.