Durability classification of red beds rocks in central Yunnan based on particle size distribution and slaking procedure

Moisture induced disintegration of soft rock in Red Beds is common all over the world. The slake durability index test is most useful to quantify durability of the soft rocks. Based on a series of slaking test, this article aims to develop a durability classification involving particle size and slaking procedure. To describe the slaking procedure in detail, the Relative Slake Durability Index (Idi) is proposed. The Idi is the percentage ratio of the ith weight of oven-dry retained portion to the (i-1)th weight of ovendry retained portion. Results show that the Idi of samples have a large difference in certain slaking procedure, whereas the traditional Durability Slake Index (Id) is almost constant. Considering this limitation of Id in durability classification, an advanced classification by applying the Idi and disintegration ratio (DR) is further established in this article. Compared to the durability classification based on Slake Durability Index (Id), the new classification accounts for the particle size of the slaked material and the slaking procedure, so it provides a better measure of the degree of slaking. The classification recommended in this article divide the slake durability into three classes (i.e., low, medium and high class). Furthermore, it divides both the low class and the medium class into 3 subclasses.