Global development of various emerged substrates utilized in constructed wetlands.

Constructed wetlands (CWs) are affordable and reliable green technologies for the treatment of various types of wastewater. Compared to conventional treatment systems, CWs offer an environmentally friendly approach, are low cost, have fewer operational and maintenance requirements, and have a high potential for being applied in developing countries, particularly in small rural communities. However, the sustainable management and successful application of these systems remain a challenge. Therefore, after briefly providing basic information on wetlands and summarizing the classification and use of current CWs, this study aims to provide and inspire sustainable solutions for the performance and application of CWs by giving a comprehensive review of CWs' application and the recent development of their sustainable design, operation, and optimization for wastewater treatment. To accomplish this objective, thee design and management parameters of CWs, including macrophyte species, media types, water level, hydraulic retention time (HRT), and hydraulic loading rate (HLR), are discussed. Besides these, future research on improving the stability and sustainability of CWs are highlighted. This article provides a tool for researchers and decision-makers for using CWs to treat wastewater in a particular area. This paper presents an aid for informed analysis, decision-making, and communication. The review indicates that major advances in the design, operation, and optimization of CWs have greatly increased contaminant removal efficiencies, and the sustainable application of this treatment system has also been improved.

Design, Operation and Optimization of Constructed Wetland for Removal of Pollutant.

Underground structures play an important role in achieving the requirements of rapid urban development such as tunnels, parking garages, facilities, etc. To achieve what is needed, new transportation methods have been proposed to solve traffic congestion problems by using of high-speed railway and subway tunnels. One of the issues in urban spaces due to tunnel excavation is considerable surface settlements that also induce problems for surface structures. There are a variety of published relationships concerned with field measurements and theoretical approaches to evaluating the amount of the maximum surface settlement value due to tunneling. This paper studies the ground surface settlement caused by the Greater Cairo Metro – Line 3 - Phase-1. This project was constructed by a slurry shield Tunnel Boring Machine (TBM). Therefore, this work consists of two parts. The first part presents the details of the project and monitoring results field and laboratory geotechnical investigations in order to determine the soil properties. The second part is to the comparison between the field measurements and theoretical approaches for surface settlement due to tunneling construction. At the end of the works, the results show that the more convenient methods which approach the field measurements, and the major transverse settlement occurs within the area about 2.6 times the diameter of the tunnel excavation. Doi: 10.28991/cej-2020-03091617 Full Text: PDF

/pdf/prediction-of-ground-settlement-induced-by-slurry-shield-whrecco88t.pdf

Prediction of Ground Settlement Induced by Slurry Shield Tunnelling in Granular Soils

The Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management publishes articles relating to the allied engineering and scientific disciplines involved in the environmental aspects of the management of hazardous, toxic, and radioactive waste (HTRW). These include the traditional areas of investigation, design, and construction and the related areas of planning, analysis, oversight, operations, regulations, and policy. This publication offers articles with practical approaches and solutions as well as application oriented research to the problems and challenges faced by practicing engineers, scientists, and government policymakers. Photographs and drawings are desirable; illustrative graphs and tables may be included; theoretical or lengthy formulas are discouraged. Two reviews are required for approval for publication or rejection, and the review period is very brief. Articles must relate to real-life implementation of solutions rather than research. Research-oriented papers received for review will be forwarded to the appropriate ASCE journal editor for evaluation. Articles must be technically sound and be of interest and value to a significant number of practicing engineers, scientists, and contractors in the HTRW field.

Practice Periodical of Hazardous, Toxic, and Radioactive Waste Management

A rigid nonyielding retaining structure needs to be dimensioned to have adequate stiffness, such that it can resist mobilized lateral earth pressures. This corresponds to the at-rest condition, as there are, in general, negligible lateral deformations in the backfill. Measures that can mobilize higher soil shear strength and reduce lateral thrust are therefore sought to provide a more efficient design. The present study investigates the possibility of inserting compressible geofoam panels against rigid walls using physical model testing. Controlled yielding is allowed in the backfill with the occurrence of deformations in the geofoam. The mobilized earth pressures vary from the maximum at rest, to the intermediate, and finally to the minimum full active state depending on the magnitude of displacement. The effects of geofoam thickness and stiffness on lateral earth pressure reduction are explored. The measured pressure and displacement distributions form a comprehensive reference for use in calibr...

Displacement-Dependent Earth Pressures on Rigid Retaining Walls with Compressible Geofoam Inclusions: Physical Modeling and Analytical Solutions

This paper presents studies on use of recycled tire shreds in sand–tire chips (STC) mixture for retaining wall applications. Small-scale physical model tests were performed on rigid retaining wall with different STC mixtures. Rigid retaining wall model of 600 mm height was constructed in a Perspex container. The wall was made with hollow rectangular steel sections. STC mixtures with different tire chips proportions, such as 10, 20, 30, 40, and 50 % along with pure sand were considered as backfill materials. Static surcharge load, up to 10 kPa, was applied using concrete blocks. Model wall behaviour in terms of displacements and earth pressures has been discussed for sand alone (control case) and STC mixtures as backfill materials. The experimental results indicate that the horizontal displacements and lateral earth pressures are reduced to about 50–60 % of that of control case by using STC mixtures which functioned as light weight backfill materials.

/pdf/recycled-tire-chips-mixed-with-sand-as-lightweight-backfill-31aan9i68s.pdf

Recycled Tire Chips Mixed with Sand as Lightweight Backfill Material in Retaining Wall Applications: An Experimental Investigation

This paper presents the evaluation of the optimum mixing ratio of sand-tire chips (STC) mixtures based on void ratio and shear-strength properties. Locally available sand and tire chips of 20×10  mm size are adopted. Different STC mixtures, in the range 10–70% by weight of tire chips (TC), are considered, along with pure sand (0% TC) and pure tire chips (100% TC). Specific gravity, density, and large direct shear tests were conducted for various samples. The volume of voids and weight-volume relations were determined from the dry unit weight and specific gravity values obtained for various mixtures. The results showed that the addition of tire chips up to 40% by weight showed significant decrease of void ratio by 43%. Shear-strength properties, like angle of internal friction values, are increased with TC contents up to 30%. Based on experimental results, the optimum percentage of tire chips of the selected size is in the range of 30–40% by weight, which is the equivalent of 50–60% by volume. Furt...

Evaluation of the Optimum Mixing Ratio of a Sand-Tire Chips Mixture for Geoengineering Applications

Use of scrap tire derived (STD) geomaterials in geotechnical engineering applications has received growing interest to prevent creation of wastes and conserve natural resources towards achieving sustainability. STD geomaterials and their mixtures with soils are being used in highway embankments, retaining walls, landfills and other applications as lightweight fill, backfill, compressible inclusion, vibration absorber, and drainage material. The use of STD geomaterials in these applications has been affirmed by characterization of the engineering properties based on laboratory tests and performance assessment based on physical model studies. This paper provides a review of engineering properties of STD geomaterials and their mixtures with soil (predominantly sand) based on published studies. Further, laboratory model and field studies on typical applications of STD geomaterials/mixtures such as retaining walls, foundations, embankments, and landfills are discussed. Overall, STD geomaterial alone or sand mixed with optimal STD content of 30–40% by weight has been shown to be effective for geoengineering applications.

Sustainable Utilization of Scrap Tire Derived Geomaterials for Geotechnical Applications

This paper presents the dynamic response of retaining wall models backfilled with different types of sand–tyre chips (STC) mixtures using shaking table tests. The STC mixtures with different tyre c...

Sand–scrap tyre chip mixtures for improving the dynamic behaviour of retaining walls

The applications of scrap tire-derived recycled materials in civil engineering applications have been increasing largely because of their potential economic and environmental benefits. This paper first evaluates sand–tire chip (STC) mixture properties and then discusses about the application of STC mixtures in geoengineering applications through laboratory model studies. Locally available sand and tire chips of 20 mm long with 10 mm square cross section are adopted for preparing the STC mixtures. Tire chips are mixed with sand in various percentages, ranging from 10 to 70 % with an increment of 10 %. Index and mechanical properties of sand–tire chip mixtures are determined for different proportions. Based on large direct shear tests, it was found that internal friction angle values are increased with TC contents up to 30 %. The study indicates that the optimum percentage of tire chips of the selected size is in the range of 30–40 % by weight, which is the equivalent of 50–60 % by volume. Model tests on retaining wall models by using various STC mixtures ranging from 10 to 50 % were discussed. The paper concluded that the STC mixture at the optimum ratio results in lightweight material with 20 % less unit weight with better strength parameters and compressibility behavior, which can effectively be used for geoengineering applications.

S. Bali Reddy

Papers

Recycled Tire Chips Mixed with Sand as Lightweight Backfill Material in Retaining Wall Applications: An Experimental Investigation

Evaluation of the Optimum Mixing Ratio of a Sand-Tire Chips Mixture for Geoengineering Applications

Sustainable Utilization of Scrap Tire Derived Geomaterials for Geotechnical Applications

Sand–scrap tyre chip mixtures for improving the dynamic behaviour of retaining walls

Sand–Tire Chip Mixtures for Sustainable Geoengineering Applications