Ali Özvan

The effects of discontinuity surface roughness on the shear strength of weathered granite joints

Surface roughness is one of the most important parameters governing the shear strength of rock discontinuities. Roughness types may vary based on genesis, physico-mechanical, and mineralogical properties of rocks. In this study, granite samples representing three different weathering degrees were selected to evaluate the effects of surface roughness and weathering degree on shear strength. To this aim, we determined the profile roughness coefficient (PRC), profile roughness angle (PRA), and joint roughness coefficient (JRC) for the selected fresh and weathered granite joint samples. Values of PRC were in the range of about 1.043–1.073, and PRA and JRC varied in the ranges of 16.67–21.45 and 12–18, respectively. Weathering led to the increment of joint surface roughness of the selected granitic joints due to the higher resistance of quartz crystals in the weathered matrix. However, the increment in surface roughness did not result in an increase in the shear strength. On the contrary, the shear strength of discontinuities dramatically decreased.

Quality Assessment of Geo-Materials for Coastal Structures (Yumurtalık, Turkey)

Rubble mound breakwater is one of the most important coastal engineering structures for shore and harbor protection. Standard rock quality evaluation processes were performed on massive basalt, vesicular basalt, crystallized limestone, and micritic limestone from southeast of Turkey. The rock types were evaluated within five different rock quality classification systems (CIRIA, CUR, CETMEF 2007; Lienhart 1998; Winkler 1986; Fookes et al. 1988; BS 812). The methods of CIRIA, CUR, CETMEF (2007) and Lienhart (1998) were shown to be more successful than other methods, which are insufficient to explain rock quality. Massive basalt and micritic limestone can be used as armourstone, filter layer, and core materials, but vesicular and crystallized limestone provided engineering requirements for only core materials. Vesicular basalt and crystalline limestone exhibited few poor features in terms of strength, such as iddingsite, stylolites, and micro cracks. These features can favorably affect rock strength, and oppositely affect rock quality.

Evaluation of the physico-mechanical parameters affecting the deterioration rate of Ahlat ignimbrites (Bitlis, Turkey)

The paper principally focuses on the durability assessment of various stratigraphic levels of Ahlat ignimbrites collected from the eastern region of Turkey. A total of four different ignimbrite types with dissimilar color, texture and particularly welding degree were tested in laboratory. The laboratory tests performed on the ignimbrite specimens indicate that the welding degree as well as the lithic material content mainly controls the strength and capillarity properties of the ignimbrites. In addition, the durability of highly porous ignimbrites strongly depends upon the degree of welding. The effect of several weathering agents on the ignimbrites was evaluated on the basis of decay constant parameter. Accordingly, salt and ice crystallization pressures are a couple of major destructive agents acting within the micropores of the ignimbrites. Conversely, the investigated specimens are relatively durable against cyclic wetting–drying. Statistical evaluations reveal that the pore diameter is the major controlling factor on the deterioration rate of the ignimbrites after specifically recurrent freeze–thaw cycles. Moreover, the dry unit weight of the ignimbrites is more significant than the uniaxial compressive strength considering the deterioration rates during wetting–drying and salt crystallization. A less significant relationship was obtained between pore diameter and salt crystallization decay constant.

Geotechnical Handicap of Travertine with Different Lithotype Levels as Foundation Material

Two major earthquakes occurred on October 23rd, 2011 (M=7.1) and November 9th, 2011 (M=5.6) in Tabanli and Edremit districts of Van province in Turkey, respectively. New settlement areas for Van city were determined after these destructive earthquakes. One of the most important areas for new settlements to be built was Edremit region, consisting travertine where nearly 80% of new housing units (12.384) were built by TOKI (Housing Development Administration of Turkey). Travertines have different lithotypes depending on their depositional process such as crystalline crust, shrub, reed which can affect mechanical and engineering properties of travertine and each level has different handicaps. The purpose of this study is to investigate the relationship between lithotype and physico-mechanical properties of travertines. According to the results, lithotype has an effect on physical, mechanical and rock mass properties of travertine. It is ascertained by several research methods that various handicaps may occur on such areas when the active tectonic structure of the area is evaluated along with the karstic cavities within the travertine and different lithotype qualities.

Determining the site effects of 23 October 2011 earthquake (Van province, Turkey) on the rural areas using HVSR microtremor method

A magnitude of 7.1 Mw earthquake struck Van city on October 23, 2011. Although, construction practices of all rural housing units are similar in the region, the earthquake caused massive damage to villages located on soft soils in northern region of the city. In this study, the effects of soil conditions on damaged housing units were determined by conducting horizontal to vertical spectral ratios of microtremor (HVSR) measurements. The level of damage in the villages that are settled on lacustrine and stream sediments has verified that the damage correlates well with comparatively high HVSR peak period and HVSR peak amplitude values in the range of 0.2–1.6 s and 4–10, respectively. The HVSR peak period and HVSR peak amplitude levels on rock units are in the range of 0.1–0.2 s and 1.5–2, respectively. It is important to note that hillside effect is found to be another key factor that increased the level of damage to the housing units in some villages.