Assessment of design parameters and the slope stability analysis of weak clay-bearing rock masses and associated spoil piles at Tunçbilek basin

• Published in: Arabian journal of geosciences Vol. 13; no. 1
• Main Authors: Erguler, Zeynal Abiddin, Karakuş, Hüseyin, Ediz, İ. Göktay, Şensöğüt, Cem
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 2020; Springer Nature B.V
• Subjects: Basins; Bearing; CAJG 2018: Topic 3; Clay; Conglomerates; Deformation; Design parameters; Disintegration; Earth and Environmental Science; Earth science; Earth Sciences; Energy demand; Field tests; Internal friction; Lignite; Marl; Mechanical properties; Mining; Moisture content; Mudstone; Open pit mining; Parameters; Piles; Rock masses; Rocks; Sandstone; Sedimentary rocks; Shear strength; Siltstone; Slope stability; Soil properties; Spoil; Stability analysis; Time dependence; Underground mining; Water content; Weak rock; Turkey; Weak rock mass; Instability; Slope stability; Open-pit mining; Spoil pile
• ISSN: 1866-7511; 1866-7538
• DOI: 10.1007/s12517-019-5030-8

Tunçbilek lignite basin situated in western part of Turkey has been increasingly excavated by open-pit and underground mining methods since 1940 to meet Turkey’s energy demand. The blasted and then the excavated stratified rock masses in this basin consist mainly of clay-bearing rocks such as claystone, mudstone, siltstone, and marl. It was found that the strength and deformation properties of these clay-bearing rocks decrease with the increase in water content. In addition, time-dependent attenuations were also recorded in the mechanical properties due to disintegration caused by physical weathering processes. Therefore, considerable time-dependent instabilities were observed in the slopes left after open-pit mining activities. In this study, it was aimed to determine the design parameters of weak rock masses and spoil piles at Tunçbilek basin and then to recommend safe slope geometry for open-pit mining activities. For this purpose, the geotechnical properties of rock masses and spoil piles were obtained based on field tests as well as characterizations and back analyses of the instabilities. This study reveals that shear strength parameters of undisturbed clay-bearing rock masses are 200 kPa and 30°. In addition, a cohesion of 150 kPa and an internal friction angle of 25° should be used for slope stability analyses of both weakly cemented conglomerate-sandstone and disturbed clay-bearing rock masses.