C. Gokceoglu
Hacettepe University, Geological Engineering, Faculty Member
On May 21, 1998, a catastrophic mass movement stroke the disseminated Dağköy settlement in the West Black Sea Region and caused demolishment of several tens of houses and death of many domestic animals. The mass movement occurred on a... more
On May 21, 1998, a catastrophic mass movement stroke the disseminated Dağköy settlement in the West Black Sea Region and caused demolishment of several tens of houses and death of many domestic animals. The mass movement occurred on a gentle slope with relatively dense vegetation cover after the 3-day lasted heavy rainfall. The ground material, c.a. 0,6 km 3 of volume that composed of marl and quartzite bedrock and overlying several metres thick soil profile, was removed 600 m downslope, blocked the nearby rivercourse and produced an artificial lake. The analysis of the rainfall data for long and short periods (daily and hourly) clearly indicate that the heavy rainfall was the triggering factor for the landslide. The topography, dip of marl bedding, dense high trees and thick soil horizon developed on top of the marly ground contributed to the event in various degrees. The eyewithness of the villagers and subsequent field observations show that the Dağköy landslide is complex in nature in terms of material transport and deposition. Near the crown, dismembering of the ground into slope-parallel slices and their domino-style sliding and rotation are the dominant processes. Within the central part of the accumulation zone, several enormous (with respect to landslide scale) ground blocks without any internal deformation are embedded in the muddy debris material. The highly plastic debris material is mostly clay and silt grade with lesser amount of disseminated gravels. Restoration of the landslide depicts that these large terrains were transported several hundred metres downslope within the mudflow in a rotational manner. The fringes of the accumulation zone were marked by gravel to boulder-sized angular quartzite blocks without binding fine-grained material, which is a fact sugesting another particular process, the grain flow. As the main causes of this, the mechanic fragmentation in the basal part of the landslide under the thick moving material and a pressure relief towards the fringes were suggested. Lastly, the accumulation zone was slightly gullied by subsequent low viscosity mudflows and fluid flows that deposited mud-sized fans in the very distal reach. As a complex failure and mass movement case, the Dağköy landslide was restored by means of the morphology produced, the nature and distribution of the accumulated facies, and eyewithnes of the villagers. It is concluded that the varying transportation processes from debris flow to massive sliding were determined by the initial conditions such as water content and strength of the material. The dynamic conditions such as shape, velocity and stress distribution of the failure, grinding and mixing of the material also should have played significant roles in the formation and distribution of the processes. Ref: T7-1
Turkey, landslides are the second major natural hazard, following earthquakes (Ildir, 1995). For this reason, economic losses and causalities sourced from landslides are great. Espe-cially, landslides are frequent in the Black Sea Region... more
Turkey, landslides are the second major natural hazard, following earthquakes (Ildir, 1995). For this reason, economic losses and causalities sourced from landslides are great. Espe-cially, landslides are frequent in the Black Sea Region of Turkey. Landslides are controlled by two main factors such as conditioning and triggering factors. Geology, topography, vegetation cover, drainage and groundwater conditions etc are accepted as conditioning factors while earthquakes and heavy precipitations are known as the main triggers for landslides. Investi-gation of mechanism and activity of a large and complex landslide, namely Yokuslubag land-slide, is the main purpose of the present study, because descriptions of landslides have great importance for landslide hazard mitigation efforts. For this reason, mechanism and activity of the Yokuslubag landslide are described combining air-photo interpretations, field observations and monitoring data, because the Yokuslubag landslide seems interesting and scientifically valuable. The Yokuslubag locates at south east part of the Black Sea Region (Fig.1). The re-gion has mountainous morphological characters and the Coruh River, the biggest river of the region, locates at the southern part of the landslide being the toe of the landslide. Agglomer-ates, andesites and tuffs, and their weathering products are the main slope-forming material.
The term landslide includes a wide range of ground movement, such as slides, falls, flows etc. mainly based on gravity with the aid of many conditioning and triggering factors. Particularly in the last two decades, there is an increasing... more
The term landslide includes a wide range of ground movement, such as slides, falls, flows etc. mainly based on gravity with the aid of many conditioning and triggering factors. Particularly in the last two decades, there is an increasing international interest on the landslide susceptibil-ity, hazard or risk assessments (Aleotti and Chowdhury, 1999). However, several methods and techniques have been proposed and tested to evaluate landslide assessments, but no general agreement has yet been reached about the methods used to produce such maps (Guzzetti et al., 2000). One of the important stages for the landslide susceptibility mapping is the preparation of the landslide inventory maps. In addition, analyzing the factors conditioning the landslides is also vital. In the present study, it is aimed to evaluate the landslide suscepti-bility using the most relevant conditioning parameters on the landslide occurrence in a se-lected landslide prone area in the West Black Sea region of Turkey. For this purpose, a de-tailed landslide inventory map is prepared and the fuzzy relations are considered to select the most relevant parameters. Results are compared with the factor analysis. Finally, landslide susceptibility maps of the study area are produced using two techniques and performances of the produced maps are discussed.
The uniaxial compressive strength of rocks is controlled by many factors such as mineralogy, texture, porosity, degree of saturation, weathering etc. For this reason, some researchers (Hoshino, 1974; Shea and Kronenberg, 1993; Ulusay et... more
The uniaxial compressive strength of rocks is controlled by many factors such as mineralogy, texture, porosity, degree of saturation, weathering etc. For this reason, some researchers (Hoshino, 1974; Shea and Kronenberg, 1993; Ulusay et al, 1994 Gokceoglu et al., 1998; Prik-ryl, 2001) proposed some empirical relationships between the uniaxial compressive strength and such petrophysical parameters of the rocks. Besides, it is possible to find some correla-tions between the uniaxial compressive strength and slake durability index (Cargill and Sha-koor, 1990; Koncagul and Santi, 1999). However, these researchers considered two-cycle slake durability index as recommended by ISRM (1981) and ASTM (1990). As stated by Kon-cagul and Santi (1999), Cargill and Shakoor (1990) found a statistically significant correlation between the uniaxial compressive strength and slake durability index. Some researchers (Taylor, 1988; Moon and Beattie, 1995; Ulusay et al., 1995; Bell et al., 1997; Gokceoglu et al. 2000) emphasized that two cycle slake durability testing did not appear to offer an acceptable indication of the durability of clay bearing rocks. For this reason, in this study, the four cycles slake durability index values were considered as proposed by Gokceoglu et al. (2000) when developing the predictive model. In addition, the clay contents of the rock studied were also used as the independent variable of the model. The purpose of the present study proposes a predictive model for estimating the uniaxial compressive strength of the clay-bearing rocks selected from Turkey. When developing the predictive model, the rule-based fuzzy model was taken into consideration.