Evaluation of Slake-Durability Tests and the Usage of Slake-Durability Index in Estimating Shemskak's Rocks UCS

Weatherablity of clay-bearing rocks and reduction of their geomechanical properties with wetting and drying cycles which determine with slake-durability test, is one of the most important challenges in construction of structures on such rocks. However, many investigations including the investigations carried out on in this research show that determining slake – durability index of hard and strong rocks such as sandstones using the initiated method can provide useful information from geomechanical properties of such rocks. In this research, some slake – durability tests have been carried out on some samples from Shemshak Formation and this index has been studied in different sandstones and clay-bearing rocks of the named formation. Meanwhile the effect of the number of cycles, period of time the sample is rotating in water and angularity of the rock samples on the slake – durability index as well as the relation between this index and uniaxial compressive strength has been investigated. The studies show that increase in the number of cycles reduces the slake – durability index of sandstones (different types) and clay-bearing rocks. Investigation on the effect of the time period the sample is rotating in water indicated that this factor has meaningful effect on the studied index of sandstone samples. However, the effect of the angularity of samples is quite considerable on the slake – durability index, so that in the samples with slake – durability index of above 98%, most of the angles are rounded at the end of the second cycle and there is a considerable difference between the slake – durability index in the first and second cycle of the angled samples and rounded samples. But the difference is much reduced in cycles three to five. In clay-bearing rocks with slake – durability index of lower than 98%, the effect of the angled nature on this index is more than sandstone samples, in cycles two and above. Investigation of the relation between the slake – durability index and uniaxial compressive strength shows that the slake – durability index is an acceptable and appropriate mean of estimating uniaxial compressive strength, especially in the sandstones.