Jeoloji Mühendisliği Dergisi

ABSTRACT: The onset of dilation and uniaxial compressive strength of rocks are known to be affected by mineralogical, petrographical and microstructural features. In this study, volcanic rock samples with different micro-textural characteristics from different locations in Gökçeada (Turkey) were evaluated considering the effect of mineralogical, petrographical and microstructural features on their physical and mechanical properties. Furthermore, detailed analyses were also used to understand the cracking processes under axial loads. The analyses of the cracking processes were evaluated by using thin sections obtained from the mechanically tested specimens. The results from the quantitative mineralogical and petrographical studies and observations from thin sections revealed that the mineral mass fractions have an effect on the specific gravity and loss-on-ignition (LOI) values. On the other hand, uniaxial compressive strength (UCS) and elastic properties are mostly affected by petrographic variables (e.g., mineral content). The UCS values tend to decrease with a relative increase in the groundmass with respect to the phenocryst content and vice versa. Biotite is the only mineral that influences the UCS individually. Geometric features (e.g., Feret’s diameter and perimeter) of opaque minerals and biotite are found to be important constituents influencing the Young’s modulus of the rocks. Under axial loads, crack propagation is strongly dependent on the proportional distribution of the phenocryst and groundmass. It is observed that increasing groundmass content leads to predominantly axial cracks. The cracks tend to bend or propagate as a boundary crack when they reach the boundary of an unaltered phenocryst. Thus, axial and shear cracks co-exist with increasing amounts of phenocrysts, which hinder the crack propagation. Occasionally, cracks can penetrate the altered or opaque phenocrysts, depending on the degrees of orientation (with respect to applied load) of the same minerals. Furthermore, the synthesis of the measurements obtained from UCS tests and thin section observations reveals that an increase in the amount of phenocrysts, which promote the formation of more shear cracks in addition to axial cracks, causes an increase in the radial strain and Poisson’s ratio. The other factors investigated have minor effects on the physical and mechanical properties of the studied rocks.

ABSTRACT: The Seljuk Tombs of the Seljuk Empire in the Ahlat region are included in UNESCO’s World Heritage Tentative List due to the fact that the tombstones are known to be the largest graveyards of Muslims with their historical significance. Tombstones were erected using ignimbrite type pyroclastic rocks which are widespread in the region, and several inscriptions and patterns were carved on them thanks to their softness and easy processing. However, these tombstones have been subjected to weathering effects for almost a duration of 800 years. The most striking point after the inspection of tombstones is that many of them were broken from the middle section. In this study, experimental studies were carried out on fresh ignimbrite specimens and particularly the effect of capillary water absorption on deterioration was investigated to reveal the factors leading to deterioration of Ahlat Seljuk tombstones. Accordingly, high porosity and capillary water absorption characteristics of the ignimbrites are found to be the major reasons for the deterioration of tombstones.

ABSTRACT: Heterogeneous rock mass consisting of rock blocks that is surrounded by a weak matrix is regarded asblock-in-matrix-rocks (Bimrock). Obtaining samples from this type of rock mass according to the standardsand preparing them to be used in laboratory studies are often difficult. For this reason, it is quite difficultto determine the shear strength parameters and the mechanical properties such as uniaxial compressivestrength in these sorts of rocks. There are just a few laboratory studies over bimrocks, and there isn’t awidely accepted empirical approach in the field of rock mechanics available due to the limitations of theexisting empirical methods. In scope of this work, synthetic Bimrocks samples were prepared with differentgrain sizes and different volumetric grain ratio. Uniaxial compressive strength tests were conducted onprepared samples. As a result of the experiments, the effect of grain size and volumetric grain proportionon the strength of artificial Bimrock samples were investigated. Artificial Bimrock samples with 20%, 30%and 40% volumetric grain proportions were prepared in the laboratory using gravel shaving diameters0.6 to 9.5 mm. Plaster and water were used to form matrix. The uniaxial compressive strengths of the testsamples decrease from 0.68 MPa to 0.45 MPa as the grain size decreases; and increase from 0.51 MPa to0.66 MPa as the volumetric grain proportion increase. The results indicate that the uniaxial compressivestrength of Bimrocks increases with increasing grain size and volumetric grain proportion.

ABSTRACT: Groundwater is used for drinking and irrigation purposes in many parts of the world. Irrigationpractices result in the deterioration of the quality of the groundwater over the time and this adversely affects the human health and plant growth. Monitoring of the vulnerable aquifers with cost-effectivemethods is important. In this study an artificial neural network model is proposed for the prediction ofsodium absorption ratio (SAR) in the unconfined aquifer, located in the east of Ergene basin. The samplestaken from 18 observation wells were analysed monthly for electrical conductivity, total dissolved solids,temperature, total hardness, chloride and pH. Levenberg–Marquardt (trainlm) was selected for backpropagation algorithm and 35 neurons were used in the model architecture. The model follows up theexperimental data very closely (R= 0,855). Application of the proposed model would make possible tomonitor the aquifers in a more cost-effective and easier way

ABSTRACT: Water quality assessment has always been a major part of environmental management plans. In thisstudy, the groundwater quality and spatial distribution in the eastern Thrace region was assessed andmapped for agricultural and drinking purposes. Groundwater samples (n = 18) were collected from deepwells in the study area and analyzed for hydrochemical properties for the water quality assessment. TheWater Quality Index (WQI) was calculated for the quantification of water quality for human consumption.The WQI values showed that 52 % of the groundwater samples fall in the “poor” and “very poor” categorydue to agricultural impact. Nevertheless, the majority of the groundwater were suitable for irrigationin terms of sodium absorption ratio (SAR), residual sodium carbonate (RSC), sodium ratio (Na%) andmagnesium hazard (MH).

ABSTRACT: In this study, organic geochemistry, depositional environments and paleo-climatic conditions ofEkizköy coals located southeast of Muğla (Milas) were investigated. The average values of total organic carbon content (TOC) of the coal (46.24 %), HI (152.88 mgHK/gTOC) and OI (76.63 mgCO2/gTOC) showthat the depositional environment of peat deposits is suboxic. According to HI-Tmax, S2-TOC classificationdiagrams, the organic matter is composed of Type II and Type III kerogen. In gas chromatographs,n-alkanes with high, mostly single-numbered carbons are dominated and they are associated with a slightalgal contribution. CPI22-30 is calculated as 2.8, and 2.4. CPI26-28 is calculated as 3.2, and 2.8. Terrigenous/aquatic ratio (TARHC) is very high, computed as 13 and 22. These values indicate a dominance of highcarbon numbered n-alkanes, meaning the presence of terrestrial organic matter. The CPI, TARHC, ACL,Qwood/grass, Qwood/plant ve Qgrass/plant values of the sample M-4 show that woody plants were the dominantvegetation in the peat mire and the climate was relatively wet and subtrophic. However, these values of thesample M-8 show warmer climate, higher water table and also contain further aquatic vegetation thanthe values of M-4 sample.