风积粉砂土的颗分试验对比分析

Comparative analysis on particle grading test methods of aeolian silty soil

风积粉砂土不同粒级的分选是土工试验的基础。目前颗分试验总体可分为干式分级和湿式分级两类,湿式分级方法中常采用离心法和静水沉降法。为了寻求适用于粉砂土的有效分选方法,对目前常用的标准筛筛分法、过滤法、离心法、静水沉降法进行了对比试验,再结合光学显微镜和激光粒度仪对分级后的土颗粒进行观察分析。总结了几种方法的适用性,指出标准筛筛分法不能有效分选细小颗粒,因此不适合于粉砂土的颗分试验。对于粒径小于0.075 mm细粒土分别对比了过滤法、离心法、静水沉降法,其中过滤法分级效果不理想,而离心法虽在时间控制和实验效率上有不可替代的优点,但就分级结果的精确性而言,静水沉降法比离心法精确度更高。

Separation of different grain size of aeolian silty soil is the basis of geotechnical test. At present,particle grading test can be divided into two types,dry and wet classification,and centrifugation and hydrostatic sedimentation are often used in the wet classification method. In order to find an effective way for the separation of silty soil,standard sieve method,filtration method,hydrostatic sedimentation method and the centrifugation method were conducted and compared,the separated soil particles were observed by microscopy and laser particle size analyzer. The rationality of each method is summarized and it is concluded that the standard sieve method is not suitable for silty soil as it could not separate small particle effectively. The filter method,centrifugation method and hydrostatic sedimentation method were compared aiming to the fine grain size of less than 0.075 mm. The results show that filter method doesn＇t have ideal classification effect. Although the centrifugation method has the irreplaceable advantages in time control and experimental efficiency,the hydrostatic sedimentation method is more accurate in terms of classification results.