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Pleistocene deposits in Q2 loess is collapsible and has weak structural clay. In this paper, a new authentication Xi'an University of Technology, based on true triaxial apparatus, carried out with different confining pressure, water content and the principal stress ratio Q2 loess under true triaxial test, the effects of different moisture content of loess deformation, strength and Shear damage characteristics, revealing the different stress paths Q2 loess stress-strain characteristics and spatial intensity stress failure surface. Based on full amount of shear modulus change, the establishment of a damage characteristics can reflect damage factor; analysis of moisture content, confining pressure, stress path and shear strain development produce damage caused by structural changes in the native characteristics. Get the following conclusions: (1) comparative analysis of four kinds of tests to verify the Xi'an University of Technology developed true triaxial test result reliability. ① the same stress paths repeat the test five times the basic stress-strain curves converge. ② axisymmetric triaxial stress conditions tested and true triaxial stress-strain curve approximation consistent. ③ axisymmetric stress paths of different dry density remolded true triaxial tests and tests to determine the strength of the line parameters are reasonable. ④ under different shear rates reflect changes in the test results of the sensitivity of the instrument. (2) Moisture content through four, five intermediate principal stress ratio, four different confining pressure of Q2 loess true triaxial test, analysis of complex stress conditions different moisture content, the principal stress ratio and confining Q2 loess under pressure nonlinear stress-strain behavior. Indicating a low moisture content and confining pressure conditions, with the intermediate principal stress ratio increases, the stress-strain curve from strong softening softening gradually transformed into a weak or weak hardening; same confining pressure and intermediate principal stress ratio conditions, with the water content increases, the stress-strain curve from weak or weak softening hardened into a hardening; same moisture content and the principal stress ratio conditions, with the consolidation stress increases, the stress-strain curve is defined by softening into hardening type. (3) analysis of the different moisture Q2 loess variation of shear strength parameters and the destruction of the plane π trajectory. When Q2 loess in a low water content state, its cohesive strength, as b increases, when b is from 0 to 0.25, the soil significantly reduced cohesion and internal friction angle (?) Significantly increased, when b is from 0.25 to 1, the soil cohesion, c began to slow growth, internal friction (?) basically no increase or even decrease in the latter; With the water content increases, the occurrence of a significant variation changed from 0 to 0.25 with b, soil cohesion significantly increasing, when it reaches 0.3 or so, close to its peak, and then the stress ratio b, although increasing, but the cohesion has been slow in lower; internal friction angle variation and cohesion opposite. Under the same moisture content as the average increase of stress balls, π plane intensity gradually extended outward facing destruction, is a cluster of the approximate shape of the curve; same confining pressure, with the water content increases, the failure surface gradually inward contraction. (4) based on different moisture content, different intermediate principal stress ratio, different confining pressure Q2 loess whole amount of the variation of the shear modulus, revealing the evolution and development characteristics of Q2 loess damage. The same confining pressure, moisture conditions, different intermediate principal stress ratio tends to damage than a curve are, among the principal stress ratio b is small, the initial shear damage smaller than Ψ; same moisture conditions, with the confining pressure increases, the initial shear damage ratio decreases; same confining pressure, with the water content increases, the initial shear damage ratio increases. Confining pressure is high, Q2 loess of the original structure remains unchanged, and the pressure increases rigid, damage ratio decreases; moisture content is large, Q2 loess enhance existing structural damage, damage ratio increases.
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