前处理方法对马兰黄土粒度测量影响的实验研究

采用9种不同的前处理方法对延安新区马兰黄土样品进行了粒度分析,以探讨不同前处理方法对马兰黄土粒度测量结果的影响。结果表明,除去有机物、碳酸盐或加分散剂后,马兰黄土的粒度分布发生明显变化,表现为中值粒径和平均粒径显著减小,粒度分布曲线向细粒方向偏移;马兰黄土中含有一定量的有机质,会影响粒度测量结果。因而,在粒度测量前处理时,需要加双氧水去除有机质;在使用盐酸进行前处理时,可能与矿物发生反应,使得所测粒径变大,且使细颗粒含量减少。综合考虑除去有机物、碳酸盐和加分散剂,前处理方法 7使样品中值粒径、平均粒径和细粒含量变化最为显著。因此,对马兰黄土进行粒度分析时,建议使用方法 7,即给样品加入15 m L浓度为10%的H_2O_2溶液(除去有机质)煮沸使其充分反应,冷却后给烧杯注满蒸馏水,静置24 h,抽去蒸馏水,加入15 m L浓度为4%的(Na PO_3)_6(分散剂)溶液后测量。

Experimental Study on the Effect of Pretreating Method on Grain Size Distribution Pattern of Malan Loess

Nine methods were adopted to pretreat Malan loess samples from New District of Yan''an City, China to investigate the effect of different pretreatments on grain-size (GS). Results show that the GS distribution of Malan loess changed obviously after the removal of organic matter, carbonate or adding dispersant, and the median and mean GS decreased significantly, and the grain-size distributions shifted to fine end. Malan loess contained a certain amount of organic matter, which would affect the result of grain-size measurement. Therefore, H₂O₂ was needed to remove organic matter before GS measurement. Bigger grain size and fewer fine particles were found, for HCL reacting with minerals in Malan loess when using it to pretreatment. Considering the removal of organic matter, carbonate and the addition of dispersant, the pretreating method 7 made the most significant change of the median GS, mean GS and fine particle content. Therefore, method 7 is proposed for the GS analysis of Malan loess, i.e. to add 15 mL H₂O₂ solution with the concentration of 10% (in order to remove organic matter), and boil it for fully reaction, then fill the beaker with distilled water after it cooled. After standing for 24 hours, the GS was measured when the distilled water was pumped out and 15 mL of 4% solution of (NaPO₃)₆ (dispersant) was added.