Experimental Study On Mechanical And Microscopic Pore Properties Of One-time Thawing Clay Soil

Soil is composed by micro soil particles and pore through a certain arrangement and cementation, the macro physical and mechanical indexes of soil get indoor geotechnical experiment is the important basis to guide the practical engineering design and construction. Macro physical and mechanical properties of soil index of soil is essentially by the microscopic particles and the size of the pore of permutation and combination, so the relationship between change of soil microstructure and macro physical and mechanical properties of the has important scientific significance and practical significance. In addition, with the widespread application of freezing method construction, research of soil under the action of freezing and thawing macro mechanical properties and microstructure of change is an important subject, soil freezing and thawing effect on micro changed the cementation of soil particle and pore and arrangement, and transforms the macroscopic mechanical properties of the soil. Therefore, from the perspective of microstructure quantitative change to explain macro mechanics is feasible.This paper, taking Q3 clay as the research object in Xuzhou, obtained from the melting of the triaxial untrained shear experiment, scanning electron microscope(SEM), mercury injection test(MIP) on unfrozen soil and thawing soil under different consolidation stress state according to the test results analyzed the strength properties, microstructure change rule. Discussed and the research relationship between microstructure quantitative parameters and macroscopic mechanical parameters. Mainly the following conclusions are drawn, mainly got the following conclusions:1. According to the triaxial untrained shear test, found out that the strength and elastic modulus of the unloading path are less than the intensity of loading path, with the increase of consolidation stress under the two paths of the difference of elastic modulus became smaller; Under the same consolidation stress state of thawing soil shear strength and elastic modulus value are less than the intensity of unfrozen soil, with the increase of consolidation stress of two kinds of elastic modulus difference became smaller; By using the hyperbolic model can better describe the relationship between the stress state of stress and strain.2. With the increase of consolidation stress, the average pore size and average pore diameter and porosity are in gradually decreases, the and the tendency with the further consolidation stress changes gradually tend to be stable. The average pore diameter and average pore size of the thawing soil are larger than unfrozen soil, the difference with the increase of consolidation stress decreases gradually. The pore fractal dimension stress decreases, compact state of pore arrangement is become by relatively loose, samples were enhanced the coupling function of sample tend to be more compact. The thawing soil pore average fractal dimension were greater than the unfrozen soil, stress level and freeze-thaw action changed the pore characteristics of directional arrangement of sample.3. With the increase of consolidation stress accumulation into the mercury sample quantity to reduce gradually, big pore percentage content gradually reduce, micro- pore percentage content increased gradually, the porosity of the sample rate is decreased obviously. Thawing soil mercury accumulation into volume were greater than unfrozen, porosity increases, the corresponding content of big pore percentage increased slightly, micro- pore percentage content is slightly lower; The pore volume fractal dimension gradually increases, unfrozen soil of pore volume fractal dimension of is large than thawing soil, the increase of fractal dimension is mainly due to the sample of the clay content increasing, the increase of the micro pore and porosity decrease.4. The average pore size and triaxial shear strength has a significant negative correlation relationship, can be described by power function model. Big pore content percentage and specimen has obvious negative correlation between shear strength values, small pore content and sample shear strength value has significant positive correlation, obtained the correlation fitting equation of quantitative analysis from the micro change characteristics of the strength; Shear strength and the fractal dimension has significant positive correlation, the correlation fitting found that from the perspective of quantitative through pore volume fractal dimension to estimate reliability higher shear strength value of the sample.