Formation mechanisms of debris-flow material on slopes in Roudbar-e-Ghasran, Iran; A case study of the weathering impacts

Physical and chemical properties of soft sedimentary rocks can be highly affected by weathering process resulting in the alteration of the engineering behaviour of debris-flow materials, deposited on the slopes. Characterisation of the weathering process of parent rocks in debris-flow material is a crucial issue in assessing the stability of slopes that are covered with debris-flow materials (yakota & iwamatsu, 1999). The weathering process generally is defined as the breakdown of solid bedrock, through different mechanisms such as chemical, biological, and mechanical process, as well as complete transition between bedrock and soil. Among all weathering mechanisms chemical and mechanical effects are the most dominant factors in breaking down the rocks into fragments (timotHy, 2008). This paper aims to investigate the important weathering indices including petrographical, chemical and engineering indices and a discussion of their limitations and usefulness with regard to climate condition. Some of the existing methods for determination of weathering indices have been tested in experiments on two common rocks of the Eocene Karaj formation: gray-green vitric tuff and dark gray tuffaceous limestone. The results are discussed and the most dominant type of weathering in the region is discussed in the conclusion section.