Ceryan, S.; Zorlu, K.; Gokceoglu, C.; Temel, A.

The weathering state and weatherability of rocks are highly important for engineering geology projects and the use of rocks as building stones. The weathering state of rocks can be described by various chemical and petrographical weathering indices. To determine weathering state of a rock, considerable amount of chemical analyses is required. Weatherability of rocks depends on not only their mineral composition but also the number of cation replaceable with hydrogen in a mineral. In this study, the use of the k-value (cation packing index is defined as the number of cation in a mole) for characterizing the degree of weathering of granitic rocks is investigated. For the purpose of the study, the Kurtun granitic rocks are selected as the material of the study. The study contains three main stages and these are field investigations, laboratory studies and regression analyses. During the field studies, in-situ weathering descriptions and sampling are carried out. The samples are subjected to chemical and petrographic analyses and physical and mechanical tests. At the final stage of the study, a series of regression analyses between the cation packing index and other properties of the samples are performed. The results show that the k-value can be used as a weathering indicator. When compared with the other chemical weathering indices, the k-value can be used as a weathering index without chemical analyses, because it can be determined by mineralogical analyses. (C) 2008 Elsevier B.V. All rights reserved.

Ceryan, Nurcihan; Ceryan, Sener

Large-scale instability phenomena frequently occur in slopes in such geologically complex areas as Dogankent in NE Turkey. This study presents an application of the interaction matrices (IM) methodology, as a semi-qualitative method sensitive to large-scale slope instability. For both rock and soil slopes, the main interactive factors were distance from faults, degree of weathering and slope angle. Using IM, a slope failure susceptibility map was created for the Dogankent area and checked again field evidence. The results indicated that IM could be a useful method for slope stability assessment.

Ceryan, Sener; Tudes, S.; Ceryan, N.

The description and classification of the rocks provide important information for geotechnical modeling in order to predict their engineering behaviors. One of the most imperative parameters influencing the engineering behaviors of the rocks is the degree of weathering. Therefore, it is evident that a realistic weathering classification is necessary mostly for establishing the geotechnical models in the engineering geology studies. For this reason, development of a qualitative weathering classification is the main purpose of the present study. The Weathering State Parameter has been first created by describing the chemical and physical changes separately owing to weathering by employing the ultrasonic wave velocity in the rock material. Then a quantitative weathering index was introduced by combining the weathering condition and the slake-durability known as the indicator of the rock/soil ratio in the rock material. Finally, this index obtained was applied on the prediction of the engineering properties of the Harsit granitic rocks (Giresun, NE Turkey). As a consequence of this study, it has been determined that the engineering properties of the samples and the numerical index proposed could be predicted. In addition, the use and the limitations of the index introduced herein were discussed.

Ceryan, Sener; Tudes, Sule; Ceryan, Nurcihan

Weathering and hydrothermal alteration of the granitic rocks in the Eastern Black Sea Region (NE Turkey) are important phenomena affecting the engineering projects in the region. The study investigated the probable paths of rock-forming mineral transformations due to weathering in the Harsit granitoid rocks, the changes of the major oxides as a consequence of weathering and the effects of weathering on the engineering properties. To identify the changes in the major oxides, the volume concentrations were considered in relation to the dry density. Chemical leaching during weathering was shown to be significant in changing the minerals. It was concluded that the engineering properties of the weathered granitic rocks can be most reliably predicted by P-wave velocity.

Ceryan, Şener

The chemical weathering of rock proceeds by water-rock interaction. During weathering geochemically mobile elements, alkali and alkali-earth elements are easily leached from rocks, leaving the residual elements to combine with components from the atmosphere to form new minerals. No single, weathering index given in the literature fits the model of the process involved in chemical weathering outlined above. This study deals with the derivation of three new chemical weathering indices oy taking both chemical processes such as leaching and new mineral formation into account. The new indices are chemical leaching index (CLI), chemical weathering product index (CWPI) and total chemical weathering index (TCWI). These indices are applied to selected weathering profiles in the Kürtün granodiorite, NE Turkey, in order to estimate the effects of chemical weathering on the physico-mechanical properties of rock materials. The relative variation of the mechanical properties and TCWI display a statistically significant correlation. Besides, it is shown that TCWI and weatherability index, originally defined by Hodder (1984) can be used together to evaluate the effect of chemical weathering on the mechanical behaviour of rocks.