缩短核磁共振测定冻土未冻水含量实验时间的方法

A method to save the determining time of unfrozen water within frozen soil by nuclear magnetic resonance

为利用核磁共振(NMR)技术更快地测试得到冻土中未冻水的含量,首先对传统的单试样测试方法进行了分析,探究了其实验时间过长的原因.然后,基于传热学中的集总参数法,研究了小体积试样在空气中以自然对流传热为冷却方式的温度变化特征.根据试样温度与时间的对应关系,提出了多试样连续测试法.最后,以一种黏土为例,分别利用多试样连续测试法和单试样测试法测量了土样冻结过程中NMR信号强度随温度变化的关系.实验结果表明:二者的测量结果非常接近,但连续测试法耗费的时间非常少.综合比较两种利用NMR技术所耗费的时间和实验结果的精确程度,多试样连续测试法是可行的.

In this article, the conventional methods of determining unfroze water within frozen soil by nuclear magnetic resonance （NMR） were analyzed to see which one able to save determining time. According to the principle and criteria of lumped parameter method in heat transfer, the temperature variation of soil specimen cooled by convection in air was analyzed. Then a new test technique named sequential determine method is pres- ented based on the relation between time and temperature. The relations between NMR signal intensity and temperature of a type of clay-water system are obtained respectively by sequential determining method and conventional determining method. The determining results show that the difference between the two determining methods is slight, but the determining time of the former is considerable short. Comparing the determining time and accuracy between the two determining methods found that the sequential determining method is practical.