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水电部土工试验规程SDS01—79(以下简称规程)已将土塑性图定为细粒土分类的标准,并有专文介绍。塑性图首先由美国卡萨格兰德(A.Casagrande)提出,是目前许多国家进行细粒土分类的依据。 卡氏塑性图是在以塑性指数I_P为纵坐标,以液限ω_L为横坐标的直角坐标图上,绘上两条直线:A线I_P=0.73(ω_L-20),B线ω_L=50％,将图划为四个区域,分出六大类土:A线以上为高液限和低液限粘质土(CH、CL),A线以下为高液限和低液限粉质土(MH、ML)与有机粘土和有机粉土(OH、OL)。卡氏塑性图是根据试验成果的统计而制订的,A线和B线是从实践中总结出来的经验分界线。由于塑性图考虑了土中有机质含量与土的塑性指数和液限等决定细粒土性质的基本因素的影响,能较全面地反映细粒土的分类原则,使用塑性图,可避免单纯考虑粒度成分或塑性指数进行分类的缺点。
The Ministry of Water Resources’ soil test procedure SDS01-79 (hereinafter referred to as “the Regulation”) has defined the soil plasticity map as the standard for the classification of fine-grained soil, and has introduced special articles. The plastic map was first proposed by A. Casagrande in the United States. It is the basis for fine-grained soil classification in many countries. The Cartesian plasticity plot is based on the plasticity index I_P as the ordinate and the liquid limit ω_L as the abscissa of the Cartesian coordinate diagram. Two lines are drawn: A line I_P=0.73 (ω_L-20), and B line ω_L=50% The map is divided into four areas and six types of soil are classified: Above line A is high and low liquid limit clay soil (CH, CL). Below line A is high liquid limit and low liquid limit silty soil. (MH, ML) with organoclay and organic silt (OH, OL). The Karnofsky plasticity chart is based on the statistics of the test results. Lines A and B are the empirical dividing lines drawn from practice. Since the plastic map takes into account the influence of the organic matter content in the soil, the plasticity index of the soil, and the basic factors that determine the nature of the fine-grained soil, it can more fully reflect the classification principle of the fine-grained soil, and the plastic map can be used to avoid considering the granularity alone. The disadvantages of classification of composition or plasticity index.