打开文本图片集

摘 要：为了研究冻融循环作用下岩石的细观结构损伤特性，以花岗岩为研究对象，进行了90次冻融循环实验，并采用核磁共振技术对冻融岩石进行了检测，得到了花岗岩的细观结构变化特征。结果表明：随着冻融循环次数的增多，花岗岩的孔隙度逐渐增大，在0～30次的冻融阶段，岩样的孔隙度增速缓慢，而在30～70次冻融循环阶段，孔隙度增长幅度明显加快，花岗岩的T2谱分布主要集中在0.1～100 ms;将岩样的T2谱分布转化为岩石孔径分布曲线，统计出了冻融后花岗岩的孔隙分布结果，孔径分布在1～500 μm范围内最多，且以小孔孔隙为主，占总孔隙比例最高达78.62%，中孔次之，微孔数量最少。基于核磁共振技术的冻融循环作用岩石细观结构的损伤特性为研究岩石破坏机理提供了可靠的实验数据。

关键词：冻融循环;核磁共振;细观结构;孔径分布

中图分类号：TU 458+.2 文献标志码：A

An LF-NMR study of the micro-structural deterioration

of rocks under the effect of freeze-thaw cycles

LI Jie-lin1，2，LIU Han-wen1，2，

ZHOU Ke-ping1，2，

ZHU Long-yin1，2

（

1.School of Resource and Safety Engineering，Central South University，Changsha 410083，China;

2.Mining Engineering Technology Research Center for High Altitude Cold Region，Central South University，Changsha 410083，China）

Abstract：In order to study the characteristics of micro-structural deterioration of rocks under the effect of freeze-thaw cycles，a series of 90 freeze-thaw cycles experiments were conducted on granites，and the Low Field Nuclear Magnetic Resonance（LF-NMR）was used to test the frozen-thawed rocks，thus the micro-structural changing features of granites were acquired.The results show that as freeze-thaw cycles increase，the porosity of granite gradually grows.At the stage of 0～30 freeze-thaw cycles，the porosity of rock specimens grows slowly，yet at the stage of 30～70 freeze-thaw cycles，the porosity evidently grows quickly.The T2 spectral distribution of granites mainly exists within the range between 0.1 and 100 ms.The T2 spectral distribution was transformed into the distribution curve of rock pore sizes.Statistics of the pore distribution of granites after freeze-thaw cycles shows that pores of which the radius is within the range of 1～500 μm are the most，and they are mainly mini-pores，which take up a percentage as high as 78.62%.The meso-pores are less，and the micro-pores are the least.Based on NMR，the deterioration characteristics of rock microstructures after freeze-thaw cycles provide reliable experimental date for studying rock damage mechanism.

Key words：freeze-thaw cycles;nuclear magnetic resonance;micro-structure;pore distribution

0 引 言

巖石是一种复杂的天然介质，其内部存在大量的微裂隙、微孔洞等地质缺陷[1-2]，且呈随机状态分布[3]。在寒区环境中，岩土工程普遍面临着冻融作用的影响，在自然界反复的冻融循环过程中，弥散在岩石内部的微细缺陷不断演化，形成宏观裂纹，引起岩体材料力学性能劣化[4]，并最终导致岩体结构破坏，进而引发岩质边坡的冻融风化、剥蚀以至滑坡，路基及建筑地基冻胀抬升和融化下沉等冻融灾害[5-7]。寒区岩体工程稳定性评价、冻融灾害防治等已成为急需解决的关键科学问题[8]。因此，研究冻融循环影响下的岩石细观结构特征对于分析岩石的损伤变形和破坏具有重要意义，能有助于揭示寒区岩体的损伤机理。