Ankara Kalesi ve civarindaki kaya şevleri için potansiyel duraysizlik haritasi

There is a dense population at the rock slopes of Ankara Castle and its vicinity, located at Altindaǧ town of Ankara. The rock type in the study area is vertically jointed andesite which forms steep topographical features. Due to the features of rock type and the site vicinity, instabilities sometimes cause casualties and damages. The aim of the present study is to investigate the probable modes of instabilities using kinematic analysis technique and to construct potential instability map of the study area with the aid of GIS (Geographical Information Systems). For this purpose, observations and measurements on natural rock slopes are carried out in conjunction with scanline surveys and sampling during the field studies and three major discontinuity sets are determined in the study area. Friction angle used in the kinematic analysis is obtained from laboratory direct shear tests carried out on the discontinuity surfaces. Test results are confirmed by limit equilibrium back analysis of a wedge type failure in the study area, and is accepted as 30° for the kinematic analysis. In order to perform the kinematic analysis in digital format, a computer program called DIKA (Digital Kinematic Analysis), is developed. Planar, wedge and toppling type of failures are assessed using this program, and potential instability map of the study area is then constructed. Based on the results from the produced instability map, 28 % of the study area is considered as potentially susceptible to toppling failure, while the areas potentially susceptible to wedge and planar failures are found as 15 % and 10 %, respectively. It is considered that potential instabilities can be transformed into rock falls after failures have occurred due to the presence of high and steep topographical features.