Effect of disturbed zone depth on slope stability analysis: a case study from Western Black Sea Region (Turkey)

Rocks in road cuts are affected by weathering, excavation and tectonic activities. The weak rocks especially disturbed by tectonic activities lose their strength over the years due to excavation and weathering. One of the most important parts to consider here is the damage caused by the type of excavation to the rock mass. In addition, weathering reduces the rock strength towards inside of the slope through discontinuities. In this study, the effects of weathering and excavation on rock strength parameters have been investigated by using twenty rock slopes located in Western Black Sea region of Turkey. Strength parameters and index rock properties were investigated in laboratory extensively. Detailed discontinuity analyses were done for all cut slopes by scan line surveys in the field. The intact rock and rock mass properties were determined for both weathered and relatively fresh zones at the cut slopes. The evaluations of disturbance depths were made according to strength differences and visual estimations of weathering degrees. According to these investigations the effects of weathering and excavation were found to be changing between 10 and 50 cm for the studied cut slopes within 5 years of lifetime. Throughout the study area the disturbance factor was assigned only to weathered zones to evaluate the stability of the slopes. Also the slope stability analyses were done by assigning the disturbance factor to different depths. It is found that the field observations are matching with the stability assessments considering the disturbed zone depths. Fresh and weathered rock mass properties were evaluated by Geological Strength Index (GSI) and the ratio between global rock mass and intact rock strength. It has been obtained that fresh and weathered rock mass properties are coherent with the Hoek Brown criterion on disturbance factor. Results indicate that the surfaces of the slopes reveal different degrees of disturbances and towards inside effects of weathering and excavation decrease. As a result, it is noted that the disturbance factor value should be used only for a certain depth and rest of the slope should be assigned as zero disturbance.
Citation Formats
T. Ersöz and T. Topal, “Effect of disturbed zone depth on slope stability analysis: a case study from Western Black Sea Region (Turkey),” presented at the 7th International Earth Science Colloquium on the Aegean Region (2019), İzmir, Türkiye, 2019, Accessed: 00, 2021. [Online]. Available: https://hdl.handle.net/11511/70715.