Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
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Research Project Kumlarda ve stili kumlarda suvılaşmanın ve sıvılaşma sonrası direncin belirlenmesinde sarsma tablası deneyleri(2012) Ecemiş, NurhanSıvılaşma, suya doygun gevşek zeminlerin deprem veya sismik bir hareket sonucunda danelerinin birbirleri olan temasının kaybolması ve boşluk suyu basıncının artması olayıdır. Yapılan literatür araştırmasına göre, ilk sıvılaşma sonrası zemin tekrar aynı büyüklükteki sismik yüklemeye maruz kaldığında rölatif sıkılık fazlasıyla artsa dahi sıvılaşma direncinde azalma veya çok az bir artış olur. Zeminin ilk sıvılaşma ve sıvılaşma sonrası direncindeki azalmanın nedeninin sadece daneler arası temas yoğunluğuna bağlı olmadığı aynı zamanda zeminin konsolidasyon karakterine bağlı olduğu düşünülmektedir. Bu proje ile eşdeğer boşluk oranının ve konsolidasyon katsayısının sıvılaşma ve sıvılaşma sonrası direnç üzerindeki etkilerine 1-g salınımlı laminer kutu (1.8x0.65x1.5m yükseklik) kullanılarak yapılan sınırlı sayıdaki sıvılaşma deneyleri ile açıklık getirilmeye çalışılmıştır. Bu proje kapsamında yapılan çalışmalarda, temiz kum ve %15 silt muhtevası içeren siltli kumlarda art arda bir seri sarsma tablası deneyleri gerçekleştirilmiştir. Her bir sarsma tablası deneyi öncesinde yapılan koni penetrasyon deneyleri (CPT) ile zeminin derinlik boyunca değişen rölatif sıkılığı ve sıkışabilirliği belirlenmiştir. Birinci sıvılaşma deneyinden sonra rölatif sıkılık çok arttığı halde ikinci sıvılaşma direncinde çok büyük bir artış olmamıştır. Ancak konsolidasyon katsayısının (cv) belirli bir limit değerinden sonra zeminin birinci, ikinci ve üçüncü sıvılaşma dirençlerinde büyük bir artış olduğu gözlemlenmiştir.Correction Cpt-Based Liquefaction Resistance of Clean and Silty Sands: a Drainage Conditions Based Approach Nurhan Ecemis (aug, 10.1007/S10518-022-01501-0, 2022)(Springer, 2022) Arık, Mustafa Sezer; Ecemiş, Nurhan; Monkul, Mehmet Murat; Tütüncü, Yunus EmreArticle Citation - WoS: 13Citation - Scopus: 12Geotechnical Reconnaissance Findings of the October 30 2020, Mw7.0 Samos Island (aegean Sea) Earthquake(Springer, 2022) Ziotopoulou, Katerinaa; Pelekis, Panagiotis; Klimis, Nikolaos; Çetin, Kemal Önder; Altun, Selim; Sezer, Alper; Ecemiş, NurhanOn October 30, 2020 14:51 (UTC), a moment magnitude (Mw) of 7.0 (USGS, EMSC) earthquake occurred in the Aegean Sea north of the island of Samos, Greece. Turkish and Hellenic geotechnical reconnaissance teams were deployed immediately after the event and their findings are documented herein. The predominantly observed failure mechanism was that of earthquake-induced liquefaction and its associated impacts. Such failures are presented and discussed together with a preliminary assessment of the performance of building foundations, slopes and deep excavations, retaining structures and quay walls. On the Anatolian side (Turkey), and with the exception of the Izmir-Bayrakli region where significant site effects were observed, no major geotechnical effects were observed in the form of foundation failures, surface manifestation of liquefaction and lateral soil spreading, rock falls/landslides, failures of deep excavations, retaining structures, quay walls, and subway tunnels. In Samos (Greece), evidence of liquefaction, lateral spreading and damage to quay walls in ports were observed on the northern side of the island. Despite the proximity to the fault (about 10 km), the amplitude and the duration of shaking, the associated liquefaction phenomena were not pervasive. It is further unclear whether the damage to quay walls was due to liquefaction of the underlying soil, or merely due to the inertia of those structures, in conjunction with the presence of soft (yet not necessarily liquefied) foundation soil. A number of rockfalls/landslides were observed but the relevant phenomena were not particularly severe. Similar to the Anatolian side, no failures of engineered retaining structures and major infrastructure such as dams, bridges, viaducts, tunnels were observed in the island of Samos which can be mostly attributed to the lack of such infrastructure.Article Citation - WoS: 10Citation - Scopus: 10Usage of Tyre Derived Aggregates as Backfill Around Buried Pipelines Crossing Strike-Slip Faults; Model Tests(Springer, 2022) Karaman, Mustafa; Demirci, Hasan Emre; Ecemiş, Nurhan; Bhattacharya, SubhamoyBuried pipelines crossing active faults are exposed to excessive soil forces under fault movements due to large relative movement between pipes and the soil surrounding them. As a result, extreme longitudinal strains develop within pipelines under large fault movements and this leads to pipeline failures. Several seismic mitigation techniques were proposed to improve the performance of buried pipelines crossing active faults. In this study, the potential of using Tyre Derived Aggregates (TDA) as a backfill material for mitigating the effects of strike-slip faulting are investigated through physical model tests. First, the details of the physical model test setup and model configuration are presented. Then a comparative study is carried out to study the effect of TDA content in the backfill and trench configurations on TDA mitigation. Model tests revealed that using a sloped trench with 100% TDA content in the backfill can decrease peak axial pipe strains up to 62% and peak bending strains up to 19%. It is observed that enlarging the trench and using an inclined trench improve the performance of the TDA mitigation technique.Article Citation - WoS: 21Citation - Scopus: 23Soil Liquefaction-Induced Uplift of Buried Pipes in Sand-Granulated Mixture: Numerical Modeling(Elsevier, 2022) Valizadeh, Hadi; Ecemiş, NurhanThe significant uplift of buried pipes observed during recent earthquakes has showed the need for further research in remediation methods for soil liquefaction. Sand-granulated rubber mixture is reported as a new soil improvement method that can be applied as a liquefaction mitigation filling material around buried pipe. In this study, the effects of pipe size, burial depth, and shaking intensity on the pipe uplift and the liquefaction potential of the sand-tire derived granulated rubber mixture placed around the buried pipes were investigated using numerical models. First, the result of 1-g shaking table tests was used for the verification of the numerical analysis. Comparing the numerical results and the experimental measurements showed that the numerical simulation using the UBCSAND constitutive model could accurately estimate the liquefaction-induced uplift of the buried pipes as well as the related failure. Then, a parametric study was conducted to investigate the effects of the pipe diameter, the pipe depth, and the value of the acceleration on pipe uplift and liquefaction potential when the SGR mixture was placed as filling material. Eventually, an analytical formula was proposed to estimate the liquefaction-induced uplift of buried pipes, and the soil failure mode was categorized according to the pipe's burial depth ratio.Article Citation - WoS: 36Citation - Scopus: 39Sand-Granulated Rubber Mixture To Prevent Liquefaction-Induced Uplift of Buried Pipes: a Shaking Table Study(Springer, 2021) Ecemiş, Nurhan; Valizadeh, Hadi; Karaman, MustafaBuried pipelines in liquefiable soils are vulnerable and can float during earthquake excitation. The uplift forces due to pore-water-pressure generation relocate the pipelines in the soil. Therefore, it is essential to measure the liquefaction effects of the backfill materials on buried pipes and make an intelligent choice for the surrounding soil to reduce the applied forces on pipelines during liquefaction. Recently, scrap tire-soil mixtures have been used as a new geomaterial to decrease the adverse effects of liquefaction. This paper investigates the flotation of the buried pipe and the sand-granulated rubber mixture's effectiveness around the pipe by a series of shaking table tests. Dynamic tests were performed under 1 g conditions on a fully saturated sand-granulated rubber mixture with small-diameter buried pipes. Three different granulated-rubber dimensions of 2.5-5, 5-10, and 10-15 mm and granulated rubber ratios of 10, 20, and 30 percent were examined in the tests. The outcomes of excess pore water pressure, settlement, pipe uplift, and upward pressure during and after shaking were compared. The test results demonstrated that the sand-granulated rubber mixture reduces excess pore water pressure accumulation and prevents liquefaction. Moreover, the effect of pipe diameter, burial depth, consolidation coefficient of the mixture, and uplift initiation time on pore water pressure and load increment below the pipe were combined to predict the buried pipe's uplift probability.Article Citation - WoS: 39Citation - Scopus: 44Experimental and Numerical Modeling on the Liquefaction Potential and Ground Settlement of Silt-Interlayered Stratified Sands(Elsevier, 2021) Ecemiş, NurhanRecent seismic events indicate that the simplified liquefaction-evaluation procedures are incapable of depicting general trends in liquefaction damage for stratified sands interlayered with silts. The conditions and mechanisms affecting the liquefaction potential of stratified sands exist in the field and ground settlement after liquefaction remain poorly understood. This work aims to investigate the seismic response of nonhomogeneous soil deposits by large-scale model tests and numerical simulations using an advanced constitutive model. A comprehensive experimental program was undertaken in which a total of three shake-table tests were performed on uniform sand and two stratified-sand deposits interlayered with different thicknesses of silt to investigate the ground settlement and distribution and dissipation of excess pore pressure during and after shaking. The shake-table test results and the numerical simulations of the silt-interlayered stratified sands, first indicate that the thickness of the silt seam has a significant influence on the liquefaction resistance of stratified-sand deposits beneath the silt layer. The second conclusion of this study reveals that the thickness and coefficient of consolidation of the silt and the liquefied sand below the silt layer significantly alter the degree of dissipation after the shake, and this causes different deformation/settlement at the ground surface. Therefore, there will be probably inaccuracies in applying simplified liquefaction evaluation procedures to the actual soil profile characterized by various patterns of layering in the field.Conference Object Citation - WoS: 1Citation - Scopus: 1Validation of Porosity in 2d-Dem Cpt Model Using Large Scale Shaking Table Tests in Saturated Sands(Taylor & Francis, 2015) Bakunowicz, Paulina; Ecemiş, NurhanThis paper contains the calibration phase of two-dimensional numerical modelling of Cone Penetration Tests (CPT) in clean saturated sand deposits. The data for calibration is obtained from the CPTs conducted before five different large scale laminar box shaking table tests. The numerical simulations of the cone penetration tests are carried out under application of the Distinct Element Method (DEM) software PFC2D (ITASCA, 2008). This software has additional basic fluid analysis option which uses well recognized SIMPLE shame (Patankar, 1980). A series of conventional Consolidated Drained (CD) triaxial tests were performed in the laboratory to assess the stress-strain behavior of the tested soil. Based on these physical experiments, calibration and scaling of DEM model was performed. In this paper, it is also proven that CPT laminar box based correlations facilitate to overcome limitations of 2D simulation. Outcome can be widely and successfully applied both in scientific research and engineering practice.Article Citation - WoS: 13Citation - Scopus: 13Effect of Soil-Type and Fines Content on Liquefaction Resistance—shear-Wave Velocity Correlation(Taylor & Francis, 2020) Ecemiş, NurhanDirect measurement of shear-wave velocity, Vs, in the field to evaluate the liquefaction resistance of soils is an alternative or complement approach to penetration-based methods. However, the existing liquefaction assessment methods established on the Vs have uncertainties about how the fines content and soil-type change the relationship between Vs and liquefaction resistance. The first part of this paper discusses the existence of fines on the correlation between cone penetration resistance and Vs. The second part focuses on the liquefaction resistance that is construed over again using the simplified cone penetration test (CPT)-based liquefaction screening procedure in terms of Vs for three distinct ranges of non-/low plastic fines content <35% fines. The outcomes of the investigation indicate that for each fines content, the correlation between CRR and Vs1 is not unique; there is a significant scattering of the curves for different soil types. Finally, using the results of this investigation as well as the simplified CPT-based liquefaction screening method, a soil-type specific CRR–Vs1 relationship developed for the unbounded, very young (Holocene-age) soils. © 2018 Taylor & Francis Group, LLCArticle Citation - WoS: 3Citation - Scopus: 3Feasible Packing of Granular Materials in Discrete-Element Modelling of Cone-Penetration Testing(Taylor and Francis Ltd., 2018) Ecemiş, Nurhan; Bakunowicz, PaulinaThis paper explores how the discrete-element method (DEM) was found to play an increasingly important role in cone penetration test (CPT) where continuum-mechanics-based analysis tools are insufficient. We investigated several crucial features of CPT simulations in the two-dimensional DEM. First, the microparameters (stiffness and friction) of discrete material tailored to mimic clean, saturated sand, which is used in cone-penetration tests, were calibrated by curve-fitting drained triaxial tests. Then, three series of cone-penetration simulations were conducted to explore (1) top boundary conditions, (2) reasonable size of discrete particles at different initial porosities, and (3) limit initial porosity of the model for a balance between accurate representation and computational efficiency. Further, we compared the cone-penetration resistance obtained in the laboratory and numerical simulations for the range of relative densities.