压实延安黄土土-水特性及快速测定方法探讨

Rapid Determination Method of Soil-Water Characteristic Curve for the Compacted Yan’an Loess

土-水特征曲线(SWCC)是描述土体含水率与基质吸力的关系曲线,是非饱和土力学中重要的本构关系。传统通过逐步施加吸力并获得平衡状态下的含水率的测试方法,耗时费力。基于利用核磁共振技术(NMR)快速测定SWCC的新方法,对压实黄土的土水特征关系曲线进行了预测,并与实测数据进行了对比分析。结果表明,压实延安黄土的土水特性受初始含水率、干密度的影响较大,且具有不同的影响机制。快速测定方法对于较高干密度压实黄土的土水特征关系曲线预测结果较好,而对较低干密度土样的土水特征关系预测稍差。主要原因在于压实密度越大,测得的孔隙分布更接近与单峰分布,预测结果更为准确。对于具有明显双峰分布孔隙结构土体的土水特征关系曲线的预测方法需要进一步研究。

The soil-water characteristic curve(SWCC) is a curve that describing the relationship between the soil moisture content and the matrix suction,and it is an important constitutive relationship in the unsaturated soil mechanics.The traditional testing method of gradually the applying suction and obtaining the moisture content in equilibrium is usually both time and labor consuming.Based on the recently developed new method of using nuclear magnetic resonance(NMR) technique,this paper presents a method of rapid determining the SWCC of compacted loess and the results are compared with the measured data.The results show that the soil-water properties of compacted Yan’an loess are greatly affected by the initial moisture content and dry density.Both methods have different influence mechanisms.The rapid determination method has a better predictive result for the soil-water characteristic relationship curve of the compacted loess with higher dry density,while the predictive result of soil-water characteristic relationship for the lower dry density soil samples is slightly worse.The main reason is that the higher the compaction density,the closer the measured porous distribution is to the unimodal distribution,and the more accurate prediction results.For the prediction of soil-soil-water characteristic curve with obvious bimodal porous size distribution,the rapid method needs to be further investigated.