Study on microstructure and macro-mechanical properties of paleosol under dry-wet cycles
YE Wanjun1，2，WU Yuntao1，YANG Gengshe1，JING Hongjun1，2，CHANG Shuaibin3，CHEN Ming3
(1. College of Architecture and Civil Engineering，Xi?an University of Science and Technology，Xi?an，Shaanxi 710054，China；
2. Road Engineering Research Center，Xi?an University of Science and Technology，Xi?an，Shaanxi 710054，China；
3. The 4th Engineering Co.，Ltd.，of China Railway 12th Bureau Group，Xi?an，Shaanxi 710021，China)
Abstract：In order to make clear microscopic characteristics and mechanical property of natural paleosol and dry-wet cyclical paleosol，to reveal the correlation between microstructure change and macro-mechanical property and to distinguish the difference between paleosol and loess，the microscopic characteristics and mechanical properties of paleosol samples taken from Zaosheng tunnel No.3 of Yinchuan-Xi?an high-speed railway were systematically investigated under different conditions from the aspects of mineral component，porosity characters，contact form and relaxation time，adopting X-ray diffraction，scanning electron microscope and nuclear magnetic resonance，and comparisons were made with the existing research results on loess. Paleosol mainly containing quartz，feldspar and calcite shows some microscopic characteristics including coagulum and graining developing，indirect contact and surface-surface contact，a large proportion of tiny holes，quasi-circular grains and relative concentration of distribution. On the mesoscopic scale，the results of MRI show that paleosol has a T2 spectral distribution form with good inversions as well as one primary and two secondary peaks. With the proceeding of dry-wet circulation，intergranular contact form is gradually transited from surface-surface to side-surface and finally side-side or spot-surface Meanwhile，the proportion of micro holes gradually reduces accompanying with medium and large holes gradually increasing，the granular abundance value constantly increases and fractal dimension gradually decreases. On the mesoscopic scale，the main peak of T2 spectrum still takes a large proportion，and with increasing cycle number，the peak value of the spectrogram roughly increases and constantly moves right accompanying with the spectrum area gradually increasing. Due to the interaction of micro，fine and macro levels，both the cohesion and internal friction angle have a negative correlation with the number of dry-wet circulation，while the non-loading expansion rate has certain positive respondence. compared with loess，the content of quartz in paleosol is less，followed by illite and calcite，and the proportions of micro，small，and medium and large holes are respectively larger，smaller and same. The granular distribution of paleosol is relatively centralized and the shape tends to be round.
叶万军1，2，吴云涛1，杨更社1，景宏君1，2，常帅斌3，陈 明3. 干湿循环作用下古土壤细微观结构及宏观力学性能变化规律研究[J]. 岩石力学与工程学报, 2019, 38(10): 2126-2137.
YE Wanjun1，2，WU Yuntao1，YANG Gengshe1，JING Hongjun1，2，CHANG Shuaibin3，CHEN Ming3. Study on microstructure and macro-mechanical properties of paleosol under dry-wet cycles. , 2019, 38(10): 2126-2137.
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2019, Vol. 38 
