Browsing by Author "Ozvan, Ali"

Now showing 1 - 20 of 20

An Approach for Determining the Relationship Between the Parameters of Pressuremeter and Spt in Different Consistency Clays in Eastern Turkey
(Springer Heidelberg, 2018) Ozvan, Ali; Akkaya, Ismail; Tapan, Mucip
The pressuremeter test is one of the borehole loading tests that determines the deformation characteristics of subsurface soil. The main idea of the pressuremeter test is to inflate the cylindrical hole drilled in order to measure the pressure-deformation relations of the soil. Another in situ test by which soil properties are determined is the well-known standard penetration test (SPT). The consistency and firmness of soils can be determined using the test results of these in situ tests. In order to determine the relationship between the results of these two tests in clayey soils with low and high plasticity characteristics, a total of 20 boreholes with 1.5-4.5 m depths were drilled, and both tests were performed at varying depths. Following the pressuremeter test, pure limit pressure (P (L)) values and pressuremeter deformation modulus (E (M)) were calculated for 31 different levels, respectively. These values were compared to SPT (N (60)) values, and high determination coefficients (R (2)) were attained. Therefore, for clayey soils, it is possible to determine E (M) and P (L) values from SPT results, and consequently SPT test results can be used to calculate settlement and bearing capacity as well as the undrained shear strength values (c (u)) of low and high plasticity clayey soils.
Chemical Characterization of Patnos Scoria (Agri, Turkey) and Its Usability for Production of Blended Cement
(oficyna Wydawnicza Politechniki Wroclawskiej, 2012) Depci, Tolga; Efe, Tugba; Tapan, Mucip; Ozvan, Ali; Aclan, Mustafa; Uner, Tijen
This paper reports results of investigations on suitability of scoria (PTS), collected from Patnos (Agri) in Turkey, for blended cement production. Scoria (basic pumice) was chosen as cement replacement materials due to its availability and cost in Agri in Turkey. The portland cement was replaced by scoria within the range of 0, 5, 10, 20, 30, 40 and 50%. Characterization of scoria was subjected by the X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM), BET surface area and porosity, zeta potential (zeta) and thin sections. The standard tests were conducted for the obtained fresh and hardened states of scoria blended cement paste. Furthermore, the obtained cements were characterized by the XRF. According to experimental results, scoria up to 20% ratio could be added into clinker and it has a good potential of manufacturing blended scoria cement.
Comparison of Spt and Vs-Based Liquefaction Analyses: a Case Study in Ercis (Van, Turkey)
(Springer international Publishing Ag, 2018) Akkaya, Ismail; Ozvan, Ali; Akin, Mutluhan; Akin, Muge K.; Ovun, Ugur
Liquefaction which is one of the most destructive ground deformations occurs during an earthquake in saturated or partially saturated silty and sandy soils, which may cause serious damages such as settlement and tilting of structures due to shear strength loss of soils. Standard (SPT) and cone (CPT) penetration tests as well as the shear wave velocity (V-s)-based methods are commonly used for the determination of liquefaction potential. In this research, it was aimed to compare the SPT and V-s-based liquefaction analysis methods by generating different earthquake scenarios. Accordingly, the Ercis residential area, which was mostly affected by the 2011 Van earthquake (M-w = 7.1), was chosen as the model site. Ercis (Van, Turkey) and its surroundings settle on an alluvial plain which consists of silty and sandy layers with shallow groundwater level. Moreover, Caldiran, Ercis-Kocapinar and Van Fault Zones are the major seismic sources of the region which have a significant potential of producing large magnitude earthquakes. After liquefaction assessments, the liquefaction potential in the western part of the region and in the coastal regions nearby the Lake Van is found to be higher than the other locations. Thus, it can be stated that the soil tightness and groundwater level dominantly control the liquefaction potential. In addition, the lateral spreading and sand boiling spots observed after the 23rd October 2011 Van earthquake overlap the scenario boundaries predicted in this study. Eventually, the use of V-s-based liquefaction analysis in collaboration with the SPT results is quite advantageous to assess the rate of liquefaction in a specific area.
Deformation Patterns in the Van Region (Eastern Turkey) and Their Significance for the Tectonic Framework
(Slovak Acad Sciences Geological inst, 2019) Sengul, M. Alper; Gurboga, Sule; Akkaya, Ismail; Ozvan, Ali
The area of investigation is located on the south-eastern shore of Lake Van in Eastern Turkey where a destructive earthquake took place on 23rd October. 2011 (Mw =7.1). Following the earthquake, different source mechanisms, deformations, and types of faulting have been suggested by different scientists. In this research, Edremit district and vicinities located on the southern side of Van have been investigated to understand the deformation pattern in a travertine (400 ka) formation on the surface, and its structural and stratigraphic relationships with the main faults under the surface by using two-dimensional (2D) Electrical Resistivity Tomography (ERT) profiles. The results were used to document the deformation pattern of rocks with the Miocene and the Holocene (400 ka travertine) in ages. By means of the investigations, deformation patterns implying the tectonic regimes during the Oligocene-Miocene-Pliocene, and Quaternary time have been determined. According to detailed field work, the local principal stress direction has been defined as approximately N35 degrees W. This is also supported by the joint set and slip-plane data. Moreover, Oligocene-Miocene units provide a similar principal stress direction. Our data suggest that the southern part of the Elmalik fault is characteristic of reverse faults rather than of the normal fault system that has been previously reported. In addition, the Gurpinar fault controlling the deformation patterns of the region is a reverse fault with dextral component.
Determining the Site Effects of 23 October 2011 Earthquake (Van Province, Turkey) on the Rural Areas Using Hvsr Microtremor Method
(indian Acad Sciences, 2015) Akkaya, Ismail; Ozvan, Ali; Tapan, Mucip; Sengul, M. Alper
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.
Earthquake Is Manmade Catastrophe Rather Than a Natural Disaster: Turkey
(Springer-verlag Berlin, 2011) Yilmazer, Ozgur; Yilmazer, Ozlem; Ozvan, Ali; Leventeli, Yasemin; Yilmazer, Hays
Soil grounds are several billion times more susceptible to earthquake disaster than rocky grounds. The probability of any soil to be liquefied is several billion times greater than that of even an extremely weak rock in case of fully saturated. Any rock, ranging from extremely weak to strong rock, is not susceptible to liquefaction even at submerged state. Shear strength of a saturated soil under dynamic condition approaches zero whereas the reduction in strength of the saturated rock is practically negligible. In another saying, the ratio of shear strengths [tau = c+sigma'(n) tan phi] of saturated rock over soil goes to infinite. Similarly, the ratio of modulus of elasticily [E, kPa] of saturated rock over soil tends to go infinite too. Turkey is a country over which many micro plates are moving relative to each other. The North Anatolian (NAF), East Anatolian (EAF), and Ecemi fault (EF) are the three major strike-slip faults that cause destructive earthquakes only in soil grounds. The fourth distinct one is the gravity fault (graben) system prevailing in the Aegean region, which is less destructive due to lower energy storage capacity. All of the active fault systems comprise fertile farm fields and extend their limits with time. Such soil grounds form lowlands rich in groundwater and mineral. However, such soil lands are exposed to earthquake catastrophe. Furthermore, the lowlands are not good human health. Most of the viruses and bacteria can grow up. That is the main reason why such lands have to be preserved for farming and should be closed to settlement. The strike slip faults are, in general, coincident with the former suture zones bearing numerous polished sub-vertical discontinuities. These planes have great potential to act as a strike slip fault plane. San Andreas Fault in USA, Kobe Fault in Japan, and Dead Sea Fault extending from Jordan to Turkey are the typical examples. The recurrences of earthquakes create fertile low lands with shallow groundwater table. Such medium favors liquefaction, plastic deformation, rupture, sand ridges and cones, and magnification of the amplitude. An earthquake becomes more destructive in the cases of shallower groundwater table (z < 20 m) and thicker soil mantle (t > 20 m). Hence, one may conclude that rocky grounds are favorable for construction whereas soil grounds should be reserved for agricultural activities.
Effect of Physical, Chemical and Electro-Kinetic Properties of Pumice on Strength Development of Pumice Blended Cements
(Springer, 2013) Tapan, Mucip; Depci, Tolga; Ozvan, Ali; Efe, Tugba; Oyan, Vural
In the present study, the potential effects of physical, chemical and electro-kinetic properties of pumice on the strength development of pumice blended cements (PBC) were examined and documented. A significant relationship between zeta potential of pumice samples, setting time and water demand of PBC was found. A relationship between the chemical content of pumice samples and compressive strength of PBC was also observed. However, zeta potential of the pumice samples was found to be less effective in strength development. Despite the lower clinker content, the setting time of the PBC samples was shorter than control specimen. 30 % pumice replacement by clinker resulted in 5-28 % reduction in 28-day strength depending on the characteristics of the pumice samples and grinding time.
Effect of Physical, Chemical and Electro-Kinetic Properties of Pumice Samples on Radiation Shielding Properties of Pumice Material
(Pergamon-elsevier Science Ltd, 2014) Tapan, Mucip; Yalcin, Zeynel; Icelli, Orhan; Kara, Husnu; Orak, Salim; Ozvan, Ali; Depci, Tolga
Pumice has been used in cement, concrete, brick, and ceramic industries as an additive and aggregate material. In this study, some gamma-ray photon absorption parameters such as the total mass attenuation coefficients, effective atomic number and electronic density have been investigated for six different pumice samples. Numerous values of energy related parameters from low energy (1 key) to high energy (100 MeV) were calculated using WinXCom programme. The relationship between radiation shielding properties of the pumice samples and their physical, chemical and electro-kinetic properties was evaluated using simple regression analysis. Simple regression analysis indicated a strong correlation between photon energy absorption parameters and density and SiO2, Fe2O3, CaO, MgO, TiO2 content of pumice samples in this study. It is found that photon energy absorption parameters are not related to electro-kinetic properties of pumice samples. (C) 2013 Elsevier Ltd. All rights reserved.
The Effects of Discontinuity Surface Roughness on the Shear Strength of Weathered Granite Joints
(Springer Heidelberg, 2014) Ozvan, Ali; Dincer, Ismail; Acar, Altay; Ozvan, Burcu
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.
Evaluation of Liquefaction in Karasu River Floodplain After the October 23, 2011, Van (Turkey) Earthquake
(Springer, 2013) Akin, Mutluhan; Ozvan, Ali; Akin, Muge K.; Topal, Tamer
The eastern shore of Lake Van was shaken by a powerful earthquake (M (w) 7.2) on October 23, 2011. The epicenter of the earthquake was located at about 30 km north of the Van Province, which is one of the main cities in the Eastern Anatolia. The Van Province and particularly its largest district Ercis were adversely affected by the earthquake, and unfortunately, a total of 600 people lost their lives. Besides severe constructional damages and building collapses, ground deformations were widespread at many locations nearby the Lake Van and Karasu River floodplain. Numerous sand boils and lateral spreading cracks were observed at the left and right embankments of the Karasu River, which is one of the major streams in the region. In this study, field observations on liquefaction and lateral spreading features triggered by the M (w) 7.2 Van earthquake are initially presented. Then, the results of subsurface investigations including trial pits, drillings and geophysical surveys on specific large-scale sand boils are explained. Subsequently, liquefaction back-analysis is performed considering the gathered subsurface data. The analysis indicates that the liquefaction occurred in a shallow zone with approximately 4 m thickness in the investigated area. The Liquefaction Potential Index method reveals high liquefaction potential for the analyzed sand boil location. In addition, the effect of cap soil thickness on liquefaction is once more validated by this case.
Evaluation of Strength Parameters and Quality Assessment of Different Lithotype Levels of Edremit (Van) Travertine (Eastern Turkey)
(Pergamon-elsevier Science Ltd, 2015) Erdogan, Onur; Ozvan, Ali
Travertine deposits have an economic value due to their chemical composition and widespread use in the construction industry. Travertines reveal different lithotypes depending on their depositional process and this can affect mechanical and engineering properties of travertine. Edremit travertine displays various structural features in lateral and vertical distributions. In this study, Edremit travertine is firstly differentiated into three different levels such as crystalline crust, shrub and reed based on the mechanical, physical properties and field observations. A strength map of different lithotypes is prepared and crystalline crust level is investigated for using in marble industry. For this purpose, the long-term performance/durability of crystalline crust travertine is investigated against various environmental processes by using several accelerated weathering tests. Accordingly, compared to the crystalline crust other levels of travertine (shrub and reed) are much more affected from atmospheric conditions. Among these levels, the crystalline crust level is recommended to be used as marble according to laboratory test results whereas other levels are appropriate for cement industry. (C) 2015 Elsevier Ltd. All rights reserved.
Evaluation of the Physico-Mechanical Parameters Affecting the Deterioration Rate of Ahlat Ignimbrites (Bitlis, Turkey)
(Springer, 2017) Akin, Mutluhan; Ozvan, Ali; Dincer, Ismail; Topal, Tamer
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.
Experimental Studies on Ignimbrite and the Effect of Lichens and Capillarity on the Deterioration of Seljuk Gravestones
(Elsevier, 2015) Ozvan, Ali; Dincer, Ismail; Akin, Mutluhan; Oyan, Vural; Tapan, Mucip
Ignimbrites are used extensively in masonry and decorative cladding not only in historical structures, but also in residential houses recently as well as monuments around Ahlat (Bitlis-Turkey) region because of their light weight, softness and insulating properties. The most famous architectural monument is the Ahlat Seljuk Tombs, in which ignimbrites were used for the structure. These are thousand year old gravestones that have been subjected to significant degradation over time caused by many physical and chemical effects. The aim of this study is revealing the mineralogical, petrographical, petrophysical and mechanical properties of fresh ignimbrites as well as determining the effect of lichens and capillarity on the deterioration of Seljuk gravestones in accordance with laboratory studies and field observations. A total of four different ignimbrite levels have been evaluated, which are widespread in the region and named as N1 (reddish brown), N2 (dark brown), N3 (yellowish gray) and N4 (black), respectively. Among these ignimbrites, the samples of N1 and N2 were employed in the construction of Seljuk gravestones. The lithic material content and welding degree are the main controlling factors of the engineering properties of ignimbrites. Laboratory test results indicate that high porosity of ignimbrites and transport of water mediated by capillarity accelerate the deterioration of ignimbrites. Furthermore, lichens play a preventive role in the deterioration mechanism of ignimbrites rather than disintegrating the tombstones. (C) 2014 Elsevier B.V. All rights reserved.
Impact of Jet-Grouting Pressure on the Strength and Deformation Characteristics of Sandy and Clayey Soils in the Compression Zone
(Korean Society of Civil Engineers-ksce, 2019) Akin, Mutluhan; Akkaya, Ismail; Akin, Muge K.; Ozvan, Ali; Ak, Yusuf
Jet-grouting as a soil improvement method is extensively preferred in today's civil engineering practice. High-modulus grout columns constructed by extremely high jetting pressures displace the surrounding soil causing a densification in soil particles. Accordingly, the strength as well as the deformation characteristics of subsurface soils are relatively improved across the compression zone which is under the influence of high jetting pressure. In this study, the modification of soil properties in compression zone after jet-grouting in sandy and clayey soils is investigated by standard penetration tests (SPT) and multi-channel analysis of surface waves (MASW) performed at a couple of construction sites along established jet-grout column rows. The in-situ test results point out significant improvement of the measured parameters compared to initial values. The rate of enhancement in the compression zone is higher in sandy strata than that of clayey deposits. The strengthening of soil due to jetting pressure is validated by finite element analyses as well. Furthermore, very low shear strain values are obtained in clayey soils with respect to the improved characteristics of compression zone representing extremely low shear deformation under foundation.
A New Empirical Correlation Between Pressuremeter Modules (Em) and Shear Wave Velocity (Vs) for Clay Soils
(Elsevier, 2019) Akkaya, Ismail; Ozvan, Ali; Ozvan, Elif E.
The pressuremeter (PMT) and standard penetration (SPT) tests are the most common in situ tests used for determining the engineering properties of soils and rocks. PMT method can be used to determine the deformation and strength properties of soil or very blocky rock masses. PMT procedure is time-consuming and expensive, and it requires advanced testing equipment. Both SPT and PMT methods also require drilling to be performed in the area. The shear wave velocity (V-s) is a parameter obtained using active and passive seismic methods and provides insight into the strength properties of the soil and rock. V-s is easy to obtain with these methods and can be determined in all kinds of field conditions. Due to the difficulties experienced during many types of in-situ tests, numerous empirical equations for the soil or rock units have been proposed in the literature that are based on V-s. In this paper, correlations of Menard Deformation Modules (E-M) with the corrected SPT blow counts (SPT-N-60) and shear wave velocity (V-s) data were conducted. For this purpose, parameters of the pressuremeter were defined as a function of two variables. In order to determine the relationship between the results of these field tests and the results obtained from high-consolidated clayey soils with high and low plasticity properties, 10 boreholes with a depth of 15 m were drilled and in-situ tests were carried out at diverse depths. In addition, seismic measurements were performed at the same locations and depth-based V-s velocity data was obtained. It was concluded that E-M could be predicted as a function of SPT-N60 and V-s values, and the predictions had relatively high R-2 values of 0.77 and 0.75, respectively. This study thereby introduces to the literature empirical equations between E-M and V-s for the first time. As soil properties are heterogeneous and anisotropic, it has been shown that it is more appropriate to use the equations produced from logarithmic and exponential relations in both single and multiple statistical analysis. (C) 2019 Elsevier B.V. All rights reserved.
A New Quantitative Welding Degree Classification for Ignimbrites
(Springer, 2023) Akin, Mutluhan; Topal, Tamer; Dincer, Ismail; Akin, Muge K.; Ozvan, Ali; Orhan, Ahmet; Orhan, Ayse
As a pyroclastic rock type, ignimbrites may reveal varying degrees of welding depending on the temperature (> 535 celcius) and overburden pressure conditions during its formation. The welding degree of ignimbrites increases as the formation temperature and the thickness of the overburden deposit in the depositional environment escalate, which are the most crucial factors controlling the rate of welding in ignimbrites. With the increasing temperature, plastic deformation is observed in ignimbrites and the glassy minerals are being welded. Furthermore, the thickness of the overburden causes the deformation of the ash matrix in ignimbrites at the lower sections and the pumice grains are flattened at different rates. An increase in the degree of welding of ignimbrites causes an improvement in the physical and mechanical properties of the rock material as well. Within the scope of this research, petrographical, mineralogical, and geochemical studies were carried out on a total of 16 different ignimbrite types, which have different color and texture properties, obtained from three different regions of Turkey (Kayseri, Nevsehir, Ahlat) where ignimbrites extensively crop out, and the physical and mechanical properties of these samples were revealed. Consequently, a new welding classification was developed for ignimbrites considering the uniaxial compressive strength and dry unit weight. The proposed welding classification consists of six classes ranging from non-welded to highly welded. When the welding degrees of the selected ignimbrites are evaluated, Kayseri ignimbrites mostly exhibit moderate welding characteristics. Nevsehir ignimbrites, on the other hand, have a low welding degree whereas the degree of welding in Ahlat ignimbrites may vary from low to high. Additionally, long and short axis lengths of pumice grains in the ignimbrite specimens were determined by measuring under the microscope, and shape ratios were determined by different shape parameter evaluation methods. As a result, it has been concluded that the pumice grains in Kayseri and Ahlat ignimbrites have a more lenticular structure than the pumice grains in Nevsehir ignimbrites. Eventually, the welding degree classes of ignimbrites and the classification developed by using threshold values of the oblateness ratio (OR) values of pumice grains at different welding degrees are quite compatible. The proposed welding degree classification is of great importance in the selection of ignimbrites widely used as dimension stone and in terms of engineering classification of this rock type as well as it will guide to the scientific studies to be performed on ignimbrites with varying physical and mechanical properties.
Quality Assessment of Geo-Materials for Coastal Structures (Yumurtalik, Turkey)
(Taylor & Francis inc, 2011) Ozvan, Ali; Dincer, Ismail; Acar, Altay
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.
The Relationships Among Different Abrasion Tests on Deteriorated and Undeteriorated Rocks
(Springer Heidelberg, 2021) Ozvan, Ali; Direk, Nevzat
In ancient times, the most widely used rocks, especially in construction of roads and monuments, were sedimentary and magmatic rocks. Natural stones used in the buildings and historical monuments are subjected to atmospheric effects such as freeze-thaw, salt crystalisation and wetting and drying cycles which accelerates abrasion. Therefore, wear resistance of natural stone materials is important for selection of suitable materials in engineering projects. In order to investigate the effect of deterioration on abrasion properties of natural rock samples, three different abrasion tests (Bohme abrasion (BA), wide wheel abrasion (WWA) and aggregate impact value (AIV)) were applied to undeteriorated and artificially deteriorated (samples were subjected to accelerated weathering tests (AWT)) natural rock samples in this study. For the first time, the relationship between AIV-WWA and BA-AIV tests was experimentally investigated. Consequently, the relationships among BA-WWA, BA-AIV and AIV-WWA values were examined, the empirical formulas showing these relationships were developed and high correlations (R-2 > 0.80) were obtained. Finally, an abrasion class was proposed using classification of WWA for determining BA and AIV of natural rock samples in this study.
Site Characterization in the Van Settlement (Eastern Turkey) Using Surface Waves and Hvsr Microtremor Methods
(Elsevier Science Bv, 2019) Akkaya, Ismail; Ozvan, Ali
The settlements around Lake Van are generally located on young, unconsolidated, saturated, Quaternary aged, current lake and stream sediments. The region is under active tectonism, and many destructive earthquakes have occurred in the area both recently and in historical times. The site effect plays a very crucial role in the prediction of earthquake damage to existing structures and in the planning and design of new structures. The main purpose of this study is to determine the mechanical and physical properties of soils in and around the settlement area of Van and to determine their behaviour under a possible earthquake. Considering these situations, both borehole-based geological data and data obtained from geophysical methods were collected in the Van settlement area. Within the scope of this study, 247 boreholes (the maximum drilled depth approximately 5 km), 185 shallow seismic profiles, 56 multi-channel analysis of surface wave (MASW) profiles, and more than 200 single-station microtremor measurements were collected in the study region, and the soil structure of the study area was evaluated and mapped by analysing the data obtained. In order to investigate the engineering properties of the study area, the parameters such as shear-wave velocity (Vs) at each layer, average Vs down to 30 m depth (Vs30), soil classification, fundamental frequency (period) and the ground motion amplification factor, have been prepared. All of the geological and geophysical data sets obtained in the study area within the scope of this study were mapped with GIS-based database features, and an updatable database was prepared for future works. (C) 2018 Elsevier B.V. All rights reserved.
A Study of the Relationship Between the Pressuremeter Modulus and the Preconsolidation Pressure Around a Thrust Fault
(Springer, 2019) Ozvan, Ali; Ozvan, Elif E.; Akkaya, Ismail; Akin, Mutluhan; Akin, Muge K.
The study area is in a zone under the influence of the Lake Van water changes and the Van fault, which caused a destructive earthquake in 2011. Due to the level changes of Lake Van, sediments with different thicknesses as well as grain sizes were deposited in this region and the characteristics of these sediments were significantly affected by the morphology and lake water fluctuations in the past. A total of six boreholes were drilled along a 3-km line within the study area to determine the preconsolidation pressure (sigma(pc)) and the pressuremeter test values of the clayey levels of old lake deposits-which are known to have different physical and mechanical properties-with hopes to gain an insight on how they influence the mechanical tests performed in the field and in laboratory conditions. The relationship between these values was also statistically evaluated. When both datasets were evaluated together, it was determined that the stresses in the area close to the Van Thrust Fault plane caused deformations in the soil, which in turn affected the hanging-wall block of the thrust fault in particular. The inspection of E-M and sigma(pc) values for the area within the primary compression zone of the Van Fault revealed that both values of the boreholes on the footwall block were higher compared to other boreholes close to the lake (southwest). This finding indicates that the fault stresses at the footwall block of the fault plane enhance the mechanical characteristics of the soil. The data obtained were also evaluated using regression analysis. Relationships between all available data were investigated and a high coefficient of determination was derived between the Menard deformation modulus (E-M) and the preconsolidation (sigma(pc)) pressure.