Soil particle size distribution,which can be analyzed by using laser particle size instrument,is an im-portant factor influencing the soil engineering properties.In this paper,laser particle size instrument is used to analyze the natural clay and clay minerals particles′size distribution when they are under different dispersion such as non-dispersion,chemical dispersion,ultrasonic dispersion,etc.The experiment shows that when sample liquid limit is above 40 %,dispersion has to be chemical or ultrasonic,and no particular requirement is needed if it is less than 40 %for there is no much difference in final findings.However,no matter what the liquid limit is,the experimental performance is better when chemical or ultrasonic dispersion is applied.According to the ex-periment,mineral component and particle size are factors which will result in different size distribution curves when using different dispersion methods.It has been found that size distribution curves of montmorillonite are dif-ferent for different dispersion methods and there is almost no change on Kaolin.In addition,if the particle size is smaller than 0.02 mm,different distribution curves will be obtained with different dispersion methods.%土的粒径分布是影响土工程特性的重要因素，激光粒度法是目前常用的颗粒分析方法．文中通过采用激光粒度仪对天然土及粘土矿物开展未分散、化学分散、超声分散等分散方法下的粒径分析试验，试验结果表明：在采用激光粒度仪进行颗粒分析时，对于液限高于40％以上的土样，必须首先进行化学分散或超声分散，而对于液限低于40％的土样，是否对颗粒进行分散对试验结果影响较小．无论是液限大于40％的土样，还是液限小于40％的土样，采用化学分散或超声分散效果均较好，两者之间的差异可以忽略．不同分散方法获得的粒径分布曲线之间的差异与矿物成分及粒径级配相关，在粘土矿物方面，蒙脱土受分散方法的影响较大，高岭土则不受影响．在颗粒粒径方面，小于0.02 mm颗粒受分散方法影响较大．
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