基于核磁共振技术的软土三轴剪切微观孔隙特征研究

doi:10.13722/j.cnki.jrme.2018.0118

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摘要为探讨软土(淤泥)剪切行为的微观机制，以南沙地区淤泥土为研究对象，对原状土和三轴试验后土样进行核磁共振试验，分析真三轴固结不排水剪切过程中软土的孔隙大小、孔径分布和孔隙结构参数变化特征。结果表明：(1) 淤泥的孔径主要分布在1～20 ?m范围内，T2主波峰幅度大于99%，淤泥土中孔隙具有孔径小、孔径分布范围较窄的总体特征。经三轴剪切试验后，土的含水率减少8.79%～17.73%，孔隙率呈减小趋势。(2) 剪切应变速率和应变大小对孔径分布影响规律：小孔径分布百分数随应变速率提高而减少，中、大孔径百分数随应变速率提高而增加。淤泥在剪切过程中存在应变阈值(约4%)，当应变小于阈值时，小孔径分布百分数随应变增加而增加，中、大孔径百分数随应变增加而降低；当应变大于阈值时，应变对孔径分布的影响规律则相反。(3) NMR法可直接测量孔径大小、孔隙结构参数( )，进而分析孔隙结构参数与宏观力学性质(广义剪应力和广义剪应变 )的关系，这可为宏微(细)观理论的进一步发展提供基础及依据。

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	刘勇健
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关键词 ：土力学, 软土, 三轴剪切, 弛豫时间, 微观孔隙结构, 核磁共振技术

Abstract：In order to investigate the microscopic shear mechanisms of soft soil(muck)，the nuclear magnetic resonance test are conducted on the undisturbed and disturbed Nansha muck before and after triaxial test. The evolutions of size，distribution，and structural characteristic of pore under true triaxial consolidated-undrained shearing are analyzed. The results show that the pores of muck are mainly concentrated in the range of 1 μm to 20 μm，and the main peak amplitude of T2 spectrum is more than 99%，indicating that the pores of muck are of small size and narrow distributed. The water content decreases by 8.79%–17.73%，and the porosity decreases after triaxial test. The percentage of small pore decreases and the medium and large pore rises with the increasing of the strain rate. The percentage of small pore rises and the large pore decreases with the increasing of the strain when the vertical strain is less than the threshold of vertical strain(about 4%). This behavior reverses after the threshold. The pore size and pore structure parameters( ) can be directly measured with NMR，so the relationship between the microstructure parameters and macroscopic mechanical properties (generalized shear stress and generalized shear strain ) can be analyzed.

Key words： soil mechanics soft soil triaxial shearing relaxation time micro-pore structure nuclear magnetic resonance technique

引用本文:

刘勇健，李彰明，郭凌峰，康文武，周瑶瑶. 基于核磁共振技术的软土三轴剪切微观孔隙特征研究[J]. 岩石力学与工程学报, 2018, 37(8): 1924-1932.
LIU Yongjian，LI Zhangming，GUO Lingfeng，KANG Wenwu，ZHOU Yaoyao. Pore characteristics of soft soil under triaxial shearing measured with NMR. , 2018, 37(8): 1924-1932.

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http://www.rockmech.org/CN/10.13722/j.cnki.jrme.2018.0118 或 http://www.rockmech.org/CN/Y2018/V37/I8/1924

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