Study On The Shear Of Sanyuan Fissured Loess Under Plain Strain Condition

Based on small deformation suppose and without thinking of local large deformation in the soil before destroying,normal design methods can't reflect real conditions when soil destroys.This causes difference between design results and construction practices.Therefore how to apply the research of shear bands to practical constructions in conjunction with the designs is becoming more and more important.Internal and outer force make the rock and soil mass be out of shape, when it exceeds the internal cementing property, the rock and soil mass burst, their continuities are destroyed, and then, the ground fissures appear. Presently, the distribution and activity characteristic of Xi'an ground fissures have been found out basically, but its genetic mechanism is immature being many different points of view and disputes on it for that there are some key basic problems being unresolved. The author in this thesis according to the field in Sanyuan fissured loess .In order to deeply research the shear band phenomenon, a plane strain apparatus was developed, and a series of consolidated undrained plane strain compression tests of Sanyuan fissured loess was carried on .Most of the sample's response during the shearing procedure, such as the stress-strain response. analyzed the rupture characteristics and behavior related to loess ground fissures. Based on this, discussed the genesis and expansion mechanism of ground fissures developed in loess.Base on the experimental results, it's helpful to understand the shear band phenomenon in quantity:1)Make out the standard to determine the shear band beginning and the shear band fully formation.2)Get the full information of the following special points: shear band beginning point ,the peak ,and the shear band fully formation point.3)Suggest a strengthen standard with the consideration of localization .In order to know more about the shear band phenomenon, were done FEM program FLAC .To stimulate the shear band phenomenon, weak element was set in the FEM model. Some beneficial conclusions were got form the modeling. The test of fissured loess indicated that, the stress state and the original structural plane controlled the rupture of fissures loess, and the fissured loess was easier to produce cracks under low confining pressure.