Civil Engineering / İnşaat Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/13
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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: 13Citation - Scopus: 15A Survey of Damage Observed in Izmir Due To 2020 Samos-Izmir Earthquake(Springer, 2021) Demirci, Hasan Emre; Karaman, Mustafa; Bhattacharya, SubhamoyAn earthquake of magnitude 6.9 hit the city of Izmir (Turkey) on 30 October 2020, resulting in 117 deaths (in Turkey) and considerable economic losses. The earthquake also triggered a tsunami. Following the earthquake, field surveys are being conducted in a Covid-secure way to study and document the damages caused. The earthquake caused significant damages to residential buildings mainly located in the district of Bayrakli and Bornova. However, no damages were observed in railway and roadway bridges or tunnels and that helped the rescue operations. The damages were mainly structural which included the so-called pancake collapse (where the entire building collapsed) and soft storey type collapse (weak storey characterised with weak columns collapsed), and in some cases, only the ground floor completely collapsed. Due to the proximity of the epicentre and the geology of the area, it seemed that the ground motions were amplified. This technical note provides a summary of the seismological and recorded ground characteristics of the earthquake together with the lessons learnt.Article Citation - WoS: 37Citation - Scopus: 35Behaviour of Buried Continuous Pipelines Crossing Strike-Slip Faults: Experimental and Numerical Study(Elsevier, 2021) Demirci, Hasan Emre; Karaman, Mustafa; Bhattacharya, SubhamoyThe paper examines the behaviour of buried continuous pipelines crossing strike-slip faults using experimental and numerical modelling. A newly developed experiment setup is presented along with the derivation of relevant scaling laws and non-dimensional terms governing global response of continuous pipelines to strike-slip faulting. Four model tests are carried out to understand the performance of the pipelines and the results are presented through the derived non-dimensional framework. Three-dimensional (3D) Finite Element (FE) model is also undertaken to simulate buried continuous pipelines crossing strike-slip faults and is calibrated against the model test results and a field case record for validation and verification. A parametric study is also carried out to better understand the parameters influencing the response of buried continuous pipelines to strike-slip faults and to also investigate the effects of pipe end conditions on their behaviour. API 5 L X70 steel pipe with 490 MPa of yield strength was used in the numerical parametric study. Two different scenarios based on fault crossing angle of the pipe (beta) were considered in the parametric study: (a) pipelines in tension and bending; (b) pipelines in compression and bending. The experimental and numerical results show that the longitudinal pipe strains under strike-slip faulting are strongly dependent on six parameters: (a) normalized fault displacements (represented by delta/D where delta is the fault displacement and D is the pipe diameter which is also an indication of soil strain in the mobilised zone); (b) ratio of pipe diameter to wall thickness (D/t); (c) fault crossing angle of the pipe (beta); (d) relative soil-pipe stiffness (kD4/EI); (e) ratio of burial depth to pipe diameter (H/D) and (f) pipe end conditions. Finally, practical implications of the study are discussed.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: 34Citation - Scopus: 39Influence of Consolidation Properties on the Cyclic Re-Liquefaction Potential of Sands(Springer Verlag, 2015) Ecemiş, Nurhan; Demirci, Hasan Emre; Karaman, MustafaThe relative density can be used as the main indicator to assess the liquefaction resistance of clean sands. As relative density of the sand deposit increases significantly following the initial liquefaction, one should expect that the soil can improve its liquefaction resistance. However, earthquake records indicate that densified sand can be liquefied again (re-liquefied) at smaller cycles by the similar seismic loadings. This work aims to clarify the counterintuitive finding that, after the first liquefaction, the resulting significant increase in relative density (induced by settlements and variation of the water level) do not necessarily imply an increase in the number of loading cycles for re-liquefaction. In this paper, we present a series of experimental results concerning the cyclic liquefaction and the following re-liquefaction of clean sand deposits. The experimental setup is performed by a shaking table, transmitting one-degree of freedom transversal motion to the soil within the 1.5 m high laminar shear box. At four different seismic demands, the input excitation was imposed three times to examine the influence of the initial distributions of the relative density and the consolidation characteristics on the liquefaction potential of the sand. The re-liquefaction cycles of the sand, which previously experienced liquefaction under the same seismic loadings, show that post-liquefaction reconsolidation of the sand deposits affects the re-liquefaction resistance.Article Citation - WoS: 21Citation - Scopus: 23Influence of Non-/Low Plastic Fines on Cone Penetration and Liquefaction Resistance(Elsevier Ltd., 2014) Ecemiş, Nurhan; Karaman, MustafaUncertainties prevail at the current liquefaction screening method based on the cone penetration test (CPT) as to whether the existence of fines increases liquefaction resistance or decrease cone penetration resistance. In this study, field-based data are used to evaluate the effects of non-/low plastic fines on liquefaction resistance at the current CPT-based liquefaction assessment method. The first part of this paper examines the effects of the coefficient of consolidation or drainage characteristics of soils containing fines on cone penetration resistance. The coefficient of consolidation is influenced by the fines content and the relative density of the soil. The second part of this paper investigates the contribution of fines content less than 30% by weight on the liquefaction resistance of soils at different relative densities. Fines content over 30% by weight and/or high plasticity of fines can cause additional complications; therefore, it needs different valuation methods, which is beyond the scope of this paper. The liquefaction resistance of sands and silty sands is reinterpreted from the current CPT-based liquefaction assessment method. The trend, which presents the change of liquefaction resistance with fines content at the same relative density, is compared with the available laboratory-based data in the literature. The results show that the interpreted trend is not consistent with the laboratory-based correlations obtained by several previous researchers. Therefore, there will be probably some inaccuracies in estimation of liquefaction potential of silty sand using the current CPT-based liquefaction assessment method.