Experimental Analysis Of The Relationship Between Medium-Low Compression Soil’s Structural Yield Pressure And Shear Dilation-Contraction Characteristic

Preconsolidation pressure natural foundation soil Deriving ways, soil test specification is generally recommended Casagrande mapping experience, to draw the relevant auxiliary line according to the indoor compress e-logp compression test curves calculated to approximate inquire, but there are some shortcomings, collected and analyzed the domestic and international pressure for Preconsolidation related research, streamline development context preconsolidation pressure, clearance the merits and applicability of each method. In the compression test data processing, the use of computer numerical analysis techniques, based on the mathematical model function fitting drawing Casagrande law Deriving preconsolidation pressure, the more value mapping method for solving pc more reliable traditional hand-drawn curve, but with a different model of the function is The fitting curve during subsequent judgment often have to solve a large deviation, it discusses how to choose the fitted curve when most reasonable mathematical model function. From Clay "Low dilatancy, high pressure cut-down" qualitative viewpoint taken by Ji-Hun Passenger Railway low compressibility undisturbed silty clay specimens in natural and saturation two states to carry out the compression and direct shear test, carried out under the same state structure of the sample yield stress and shear boundaries shrink swelling pressure data corresponding vertical comparative analysis, to explore their differences and links, and structural design preset remolded yield pressure direct shear tests Verify shearing expansion and contraction of the pressure to strike a reasonable yield of the structure. The main research work and achievements are as follows:(1) Analysis of the soil disturbance Casagrande experience mapping inquire preconsolidation pressure when facing the impact of operating procedures, loading and other experimental factors, as well as the presence of troublesome curve drawing to determine the point of maximum curvature larger issues such as error and propose appropriate solutions. Grouped together to determine preconsolidation pressure of a series of tests and methods to estimate:Estimating Method e-logp curve based on double logarithmic curve class methods, class methods as well as primary and secondary consolidation situ test alternative method, the shear strength of the replacement France, inverse density, experience reference method. From the aspect of the method type, theoretical, experimental operation test and analyze the characteristics of the various methods, specifically for the development of understanding of preconsolidation pressure, for design and engineering researchers for specific soil need to use certain areas viable Test program.(2) Origin software documentation provided in the proposed cost-effective and seizure patients were considered fit, fitting information and other aspects of the fit and residual plots provide analysis indicators, analyzes the mathematical model of each recommendation e-logp function fitting compression fitting effect curve fitting stability and function. Through the same set of A-5 (under) soil analysis data to fit a variety of fitting formula of comparison, the degree of fit model function data were good, but the choice of a different mathematical model function of the results of the pc value great impact, priority should be given a reasonable change in curvature curve fitting and curve segments exist model function point of minimum radius of curvature, demonstrated during compression curve fitting Calculating the precise function pc Harris closest to the measured value of the estimated value, indicating Harris rationality model function.(3) The paper carried out that Jilin-Hunchun Railway Passenger Line silty clay samples under undisturbed natural, undisturbed saturated two states compression and direct shear tests, using Casagrande method and f method analyzes the structure yield pressure of soil, discussed the dilation and contraction variation characteristics with vertical pressure in direct shear test, proposed a critical vertical pressure indicator that used to describe shear dilation and contraction. Experimental analysis shows that:although different state of soil samples will impact structural yield pressure and critical vertical pressure of shear dilation and contraction, but both them have a good consistency, accordingly innovated a test method based on the soil shear dilation and contraction deriving the structure yield pressure, and its reliability has been validated by preset structural yield pressure’s direct shear test. Research enriches the soil’s structural yield pressure understanding.