Nature-based solutions (NBS) can protect, manage and restore natural or modified ecosystems. They are a multidisciplinary, integrated approach to address societal challenges and some natural hazards effectively and adaptively, simultaneously providing human well-being and biodiversity benefits. NBS applications can be easily noticed in circular cities, establishing an urban system that is regenerative and accessible. This paper aims to offer a review on NBS for urban water management from the literature and some relevant projects running within the COST Action ‘Implementing nature-based solutions for creating a resourceful circular city’. The method used in the study is based on a detailed tracking of specific keywords in the literature using Google Scholar, ResearchGate, Academia.edu, ScienceDirect and Scopus. Based on this review, three main applications were identified: (i) flood and drought protection; (ii) the water-food-energy nexus; and (iii) water purification. The paper shows that NBS provide additional benefits, such as improving water quality, increasing biodiversity, obtaining social co-benefits, improving urban microclimate, and the reduction of energy consumption by improving indoor climate. The paper concludes that a systemic change to NBS should be given a higher priority and be preferred over conventional water infrastructure.

The development and application of appropriate Circular Economy indicators is an issue that concerns both the scientific and the business community, as well as decision makers. The existing gap between research, policy and practice could be bridged by using a dynamic indicators selection approach that combines both expert and participatory practices. This study aims to develop such a novel approach for the selection of indicators based on views and needs of practitioners, whilst considering the complex interdependencies of the indicators and determining their importance. Twenty circularity indicators for the Water-Energy-Food-Ecosystems nexus are selected and ranked by different stakeholders. The interrelationships of the indicators are identified using the Interpretive Structural Model, resulting in six levels of importance. Cross-impact matrix multiplication applied to classification (MICMAC) analysis further enabled the classification of the twenty indicators into four categories based on their driving and dependence power. The results indicate that seven indicators—one related to regeneration of natural environment principle, four related to keep resources in use, and two related to design out negative externalities—are the driving indicators to Circular Economy. The approach can be applied to other sets of indicators as well, enabling their prioritization and implementation with other systems.

In this study, the effects of wind on an Eastern Red Cedar were investigated using numerical simulations. Two different tree models were proposed, each with varying bole lengths and canopy diameters. A total of 18 cases were examined, including different canopy diameters, bole lengths, and wind velocities. Using computational fluid dynamics (CFD) methods, the drag force, deformation, and stress of the tree models were calculated under different wind velocities and geometric parameters. A one-way fluid–structure interaction (FSI) method was used to solve the deformation of the tree. Additionally, velocity and pressure distribution around the tree were obtained. The results indicate that wind velocity and geometric parameters of the tree have a significant impact on deformation, drag force, and stress. As wind velocity increases from 15 to 25 m/s, the force on the tree increases substantially. The results also show that the diameter of the canopy has a bigger effect on stress and strain than the bole length. This study provides insights into tree behavior under wind loading for urban planning and design, informing optimal tree selection and placement for windbreak effectiveness and comfortable environments.

Excessive settlement of clayey soils and low-bearing capacity leading to damage and collapse of the structure induce problems in infrastructure construction. Various ground improvement methods are used to solve this problem. The purpose of these methods, in which the cement mixture is included, is to increase the soil bearing capacity and to reduce the soil settlement. In this study, total plastic and consolidation settlement analysis of sandy-clay soil model mixed with cement by different percentages (5%, 10%, 15%) are made. The physical and mechanical properties of the improved clay-cement soil are obtained based on the results available in the literature and in the laboratories of Istanbul Aydın University. A Finite Element program was used to perform static analysis. Static analysis of the soil was carried out under different loads (50, 100, 150, 200 kPa). The results showed that fort he plastic analysis, the 15% cement treated soil had 25% total deformation less than the untreated soil. Considering the same soil profile, for consolidation analysis, the decrease was observed to be 28% at the end of 7 days.

In this research, one of the most effective soil remediation methods in clay soils is investigated using fly ash. Consolidation settlement of clayey soils is one of the major parameters which are essential to be controlled before any construction. In order to control this parameter, consolidation test is used to determine the rate and magnitude of soil consolidation when the soil is restrained laterally and loaded axially. In this study, to study the effect of fly ash in improving the physical properties of clay, fly ash content was increased as (0%, 5%, 10%, 15%, and 20%). Moreover Sieve analysis, water content test, Atterberg limits, and Standard Proctor tests were performed for the same percentage. It was observed that by adding fly ash, plasticity of sample decreases. Furthermore, 15% mixture gives the lowest consolidation coefficient result; therefore it is advised to implement this percentage in fields.

Bu çalışmada, eksenel yükleme testi yapılan beş farklı projeye ait derin karıştırma kolonlarının taşıma gücünün grafiksel ve analitik yöntemler ile belirlenmesi ve sonuçların birbiri ile kıyaslanması olarak amaçlanmıştır. Yükleme deneylerinin sonuçlarının yorumlanmasında literatürde sıkça kullanılan üç yöntem kullanılmıştır. Bunlar Decourt, De Beer ve Chin-Kondner yöntemleridir. Sahada oluşturulan derin karıştırma kolonlarına eksenel yükleme testleri uygulanmıştır. Her proje için daha önceden belirlenen proje yükü değeri baz alınarak yükleme gerçekleştirilmiştir. Yük artışı ile deformasyonlar arasındaki ilişkiden yola çıkılarak yapılan hesaplamalarda Decourt ve Chin-Kondner yöntemleri ile hesaplanan taşıma gücü değerlerinin beş proje için birbirine yakın sonuçlar verdiği ortaya çıkmıştır. De Beer yöntemi ile hesaplanan taşıma gücü değerleri diğer yöntemlere oranla nispeten daha düşük çıkmıştır.

Correlations between compression index and atterberg limits found in the literature are very important for preliminary estimation. These equations are usually interpreted based on the R-square parameter and classified according to the conditions of the data (disturbed, undisturbed, remoulded, etc.). Although correlations reliable enough to eliminate oedometer tests are not yet fully available, these correlations can be useful in local calculations. In this study, correlations obtained from studies conducted after 2000 on the relationship of compression index and consolidation coefficient with atterberg limits and water content are mentioned and clearly shown. While the compression index equations are quite high in the literature, the equations produced with the consolidation coefficient are less in number. This is because consolidation calculations take a lot of time. Using 105 data obtained from researches in the literature, two equations were formed between the compression index, liquid limit and plasticity index. This study does not propose new equations, only relationships are generated using the Linear Regression method with data obtained from independent studies, based on the belief that the compression index has a stronger relationship with the liquid limit and plasticity index

Zemin iyileştirme teknikleri arasında çimento en çok kullanılan yöntemlerden biridir. Bu çalışmada %30 kum ve %70 kil karışımına farklı yüzdelerde çimento eklenerek bu karışım oranlarının mekanik özellikleri araştırılmıştır. Deneylerde, kaolin kil, portland çimentosu CEM-I (42.5) ve kum kullanılmıştır. İlk aşamada %70 oranında kaolin kil ve %30 oranında kum kullanılarak özgül ağırlık deneyi, elek analizi deneyi, kıvam limitleri deneyi ve kompaksiyon deneyleri yapılmıştır. Elde edilen değerler üzerine konsolidasyonsuz-drenajsız üç eksenli basınç deneyleri (UU) yapılmıştır. İkinci aşamada %70 koalin kil ve %30 kum oranlarından eşit miktarda düşürülerek %5, %10, %15 ve %20 oranlarında çimento eklenerek 1 günlük ve 7 günlük numunelere konsolidasyonsuz-drenajsız üç eksenli basınç deneyleri yapılmıştır. Deneyler sonucunda içsel sürtünme açısının çimentoya bağlı olarak belirli bir yüzdeye kadar arttığı daha sonra düştüğü görülmüştür.