Selection of the Standard for Liquid Limit and Plastic Limit

The strength of soil at liquid limit according to the current standard of liquid limit in our county is higher than those according to the standard of liquid limit in majority of countries in world, therefore a new standard is required. In this paper, based on the results of the comparative tests, considering the practice in our country, the moisture content, at which a 76 g cone penetrometer （30°apex angle） penetrates into the soil by 17mm, is suggested as the liquid limit. Meanwhile, as an interim measure, the moisture content reading for 10mm penetration of 76g cone is retained. In the combined determination method for liquid and plastic limits, the moisture content, at which a 76 g cone penetrates into the soil by 2mm, is adopted as the plastic limit. This standard is consistent with that obtained by the thread rolling method for most of the finegrain soils except low liquid limit soils and some special soils as laterite.