A comprehensive view on the compilation of an engineering geological map of carbonate rocks: a case study in the Central Alborz Zone, Iran

Abstract

The geological provinces of Iran can be divided into different zones based on different geological and structural units. The Central Alborz Zone (CAZ) is one of the most important zones among them, which extends along the southern coast of the Caspian Sea from Sepidrud valley to Firoozkuh valley. The CAZ comprises a range of industries and a high population concentration, and it is important to provide material resources and create the necessary infrastructure for this massive population. The materials produced in the different industries have different characteristics and parameters. Therefore, various studies should be carried out based on the type of materials produced and their application. The CAZ has a large variety of rock formations and facies, which facilitates extensive expansion in the production of rock materials and resources. One of the major materials in the CAZ is the carbonate rocks which exist in a wide variety of forms such as limestone, dolomite, etc. Recognizing the geological and engineering geological characteristics of carbonate rocks is important for proper use in order to increase their efficiency. The novelty of the present work is the extensive and comprehensive engineering geological study of a vast area (about 2900 km 2 ) of an important geological zone of Iran, which has not previously been conducted. As previously shown by other researchers the presence of carbonate rocks in a certain range of characteristics anywhere, we found similar results in drawing engineering geological map by integrating geological, engineering geological, geomorphological, and joint study information of carbonate rocks. Results showed that in physical tests all formations were classified as moderate to very high density (2450–2830 kg m −3 ), and very low (0.98%) to medium (8.06%) porosity. Also, uniaxial compressive strength (UCS) results showed that all formations fall within the moderate strength (20–60 MPa) to high strength (60–200 MPa) range based on the International Standard for Rock Mechanics (ISRM) classifications, and very high strength range (3–10 MPa) for point load index (PLI) based on the Broch and Franklin classification. According to these works an engineering geological map for carbonate formations of the CAZ is presented in this paper.