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工程科学与技术:2022,54(4):121-128
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基于NMR技术的孔隙结构与充填体强度关联机制
(1.华北理工大学 矿业工程学院,河北 唐山 063210;2.北京科技大学 土木与资源工程学院,北京 100083)
Correlation Mechanism Between Pore Structure and Backfill Strength Based on NMR Technology
(1.College of Mining Eng., North China Univ. of Sci. and Technol., Tangshan 063210, China;2.School of Civil and Environmental Eng., Univ. of Sci. and Technol. Beijing, Beijing 100083, China)
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投稿时间:2021-06-03    修订日期:2022-06-10
中文摘要: 充填料浆凝固后形成的充填体中含有大量的孔隙,孔隙对充填体力学性能的影响尚不明确。为探究充填体内孔隙结构与充填体单轴抗压强度(uniaxial compressive strength,UCS)的关联机制,利用十二烷基硫酸钠(sodium dodecyl sulfate,SDS)调节充填体内的孔隙含量,采用低场核磁共振技术(nuclear magnetic resonance,NMR)测试充填体内部孔隙的横向弛豫时间,利用压力机测试充填体的UCS,利用扫描电镜(scanning electron microscope,SEM)获取充填体破坏面孔隙结构的微观图像,对孔隙的孔径分布进行了分析,对孔径的分形特征进行了研究。结果表明:充填体内孔隙总量随着养护龄期的增加逐渐降低,且SDS掺量越高,样品在14 与28 d时的孔隙总量越接近;多害孔隙的占比随着养护龄期的增加明显降低,且与样品的UCS呈负相关,无害孔隙、低害孔隙、有害孔隙的占比在各龄期间变化较小;SDS掺量为所用水泥质量的0.2%时对样品的UCS最有益;孔径在5~130 nm区间的孔隙数量具有较为明显的分形特征,而孔径不在该区间的孔隙数量不具有分形特征;水泥水化产物中的钙矾石呈簇状,钙矾石因生长、发育、延伸而挤占了孔隙空间是孔隙总量、多害孔隙数量随养护龄期增加不断降低的微观原因。研究结果可以为更全面地理解充填体强度提供理论支撑。
Abstract:The backfill formed by the solidification of the filling slurry contains a large number of pores, and the influence of pores on the mechanical properties of the backfill is not clear. In order to explore the correlation mechanism between the pore structure and the uniaxial compressive strength (UCS) of the backfill, sodium dodecyl sulfate (SDS) was used to adjust the pore content of the backfill. Low-field nuclear magnetic resonance (NMR) technology was used to test the transverse relaxation time of the internal pores, the UCS was tested by a press, and the microscopic image of the damaged surface pore structure was obtained by scanning electron microscope (SEM). The pore size distribution was analyzed, and the fractal characteristics of the pore size were studied. The results showed that the total pores in the backfill gradually decrease with the increase of curing age, and the higher the SDS content, the closer the total pores of the sample at 14 and 28 d. The proportion of multi-damaging pores decrease significantly with the increase of the curing age, and it is negatively correlated with the UCS of the sample. The proportions of non-damaging pores, less-damaging pores, and damaging pores change little during each age. When the SDS content is 0.2% of the quality of the cement used, the UCS of the sample is the highest. The number of pores with pore diameters in the range of 5~130 nm has obvious fractal characteristics, while the number of pores with pore sizes outside this range do not have fractal characteristics. The ettringite in the hydration products is clustered, and the clustered ettringite squeezes the pore space due to growth, development, and extension. This is the microscopic reason why the total number of pores and the number of multi-damaging pores decrease with the increase of curing age. The research results can provide theoretical support for a more comprehensive understanding of the strength of the backfill.
文章编号:202100524     中图分类号:TD853    文献标志码:
基金项目:国家自然科学基金资助项目(51774137);河北省自然科学基金资助项目(E2019209326);华北理工大学研究生创新项目(CXZZBS2020137)
作者简介:第一作者:张友志(1990-),男,博士生.研究方向:充填采矿理论与技术.E-mail:zhangyouzhi@ncst.edu.cn;通信作者:甘德清,E-mail:17330544396@163.com
引用文本:
张友志,甘德清,薛振林,刘志义,陈勋.基于NMR技术的孔隙结构与充填体强度关联机制[J].工程科学与技术,2022,54(4):121-128.
ZHANG Youzhi,GAN Deqing,XUE Zhenlin,LIU Zhiyi,CHEN Xun.Correlation Mechanism Between Pore Structure and Backfill Strength Based on NMR Technology[J].Advanced Engineering Sciences,2022,54(4):121-128.