Geo-Congress 2019: Geoenvironmental Engineering and Sustainability

Evapotranspiration (ET) landfill covers are an emerging final cover system in contrast to the widely implemented conventional practice for landfill closure. Performance of an ET cover primarily depends on the site-specific factors such as on-site climatological conditions, soil hydraulic properties, and native vegetation. The variation of soil moisture and matric suction (SWCC) due to the fluctuation in the environmental parameters, mainly precipitation and temperature, may affect the ET cover performance. The objective of the current study was to investigate the change in soil moisture and matric suction using resistivity imaging (RI) technique. The study was conducted on a test section final cover (lysimeter) in the city of Denton landfill. Installed sensors in the lysimeter at different depths measured moisture content and matric suction of the cover soil. Electrical resistivity testing was performed in the field at regular interval across the positions of the sensors. Based on the field instrumentation and geophysical measurement, the change in electrical resistivity with moisture content and matric suction was investigated. The results indicated a significant relationship between soil resistivity and unsaturated soil behavior (SWCC), especially at lower resistivity values. The relationships were also described using the Van Genuchten model. However, a significant difference was observed at higher resistivity values. The field investigation results showed the electrical resistivity imaging technique to be a potential geophysical method to quantify and evaluate the field unsaturated behavior of evapotranspiration cover.

Sodium bentonite (NaB) and enhanced bentonites are used extensively in engineered containment barriers. These high-swelling clays are relied upon to provide long-term, low hydraulic conductivity, k (e.g., 10^-10 m/s), to restrict advective transport of contaminants. Although diffusion becomes a significant contaminant transport mechanism relative to advection in barriers with k<10^-9 m/s, diffusion data for NaB and enhanced bentonites is limited due to the complexity and long test durations of traditional diffusion test methods. Thus, a dialysis-leaching test (DLT) method was developed and refined for measuring diffusion properties of bentonite specimens with porosities (n) similar to geosynthetic clay liners. The DLT method requires short test durations (<7 d), uses inexpensive and commercially-available equipment (<$300 per setup), and has shown good reproducibility of results between different laboratories and researchers. The DLT method, including recent improvements to the technique and testing limitations, is described in detail in this paper. Example results are provided for chloride diffusion in NaB and bentonite polymer composite (BPC) specimens (n=0.82–0.89). Apparent diffusion coefficients (D_a) were measured using 200 mM potassium chloride (KCl) and 100 mM calcium chloride (CaCl₂) solutions. The diffusion results were consistent with expectations based on the literature and diffuse-double layer theory. Tests were performed at both full-scale (7 L) and half-scale (3 L) sizes, and there were no significant effects of test scale on the results. Recommendations are provided for using the DLT method to measure chloride diffusion in bentonites for different test conditions and available laboratory resources.

The opportunity of exhuming and evaluating various components of a double lined landfill system after 23 years of service is presented herein. The primary geomembrane (textured, 1.5 mm thick, HDPE) was evaluated and all eleven test properties were very close to the original properties and within current specification values. This was likewise the case for both extrusion and hot wedge seams. The geonet leak detection layer (4.4 mm thick, biplanar, HDPE) was in its original condition since no evidence of leachate was indicated. That said, the plastic cable ties holding the geonet sheets together were all broken in a brittle manner. The compacted clay liner beneath the secondary geomembrane was observed to have numerous long vertical cracks up to 15 mm wide throughout its thickness. The intact sections between the longer vertical cracks were striated with smaller cracks in all directions. While the clay’s moisture content was 12%, the moisture content was likely higher during placement and subsequent shrinkage is the probable cause of the cracking.

A high content of salt in soil makes it unsuitable for crop production. In this study, a series of laboratory test was conducted to investigate the ability of bioremediation to reduce the salinity of soil samples. Saline soil was prepared after soaking the test soil in artificial seawater for 3 days and dried it. It was then mixed with different microorganisms. Soil samples were collected to measure the electrical conductivity regularly at different specified depths by using a portable electrical conductivity meter. It was found that the electrical conductivity reduced with the help of the bacterial activities. One of the collective microorganisms was the most efficient to reduce the salinity.

The objectives of this study were to (i) measure the hydraulic conductivity and soil water retention of tailings and waste rock and tailings mixtures and (ii) assess how the tailings fraction influences hydraulic properties of the mixtures. Mine tailings and waste rock were collected from two mines, and tailings-dominated mixtures (i.e., GeoWaste) were created whereby waste rock particles act as inclusions in the tailings matrix. Hydraulic conductivity of pure tailings ranged between 9×10^-6 and 7×10^-8 cm/s, whereas hydraulic conductivity of GeoWaste ranged between 1×10^-4 and 3×10^-8 cm/s. The hydraulic conductivity of GeoWaste decreased with an increase in effective stress from 10 to 100 kPa, and was comparable to hydraulic conductivity of pure tailings at effective stresses of 100 and 500 kPa. Similarity in the water retention behavior of GeoWaste and pure tailings was dependent on the mixture ratio, whereby mixtures with larger tailings fractions exhibited more comparable soil water retention to pure tailings.

Carbonate reservoirs are characterized by extremely heterogeneity having fissures and vugs in them. Incidents are common practice when drilling through carbonate formation such as the loss of circulation and borehole breakouts. In drilling through fractured carbonate formation in North China, excessive volume of cavings accompanied significant volume of the mud loss were observed. Numerous laboratory experiments and the numerical simulation are conducted to better understand the mechanism of this drilling instability. Microstructure analysis of outcrop carbonate rock showed weak inter-granular bonding and abundance of microcracks existed in carbonate rock. Mechanical testing had been also conducted to obtain mechanical properties of carbonate rock. Through our work, discrete element method (DEM)-based square-shaped hollow model was established to further investigate the mechanism of the drilling instability of carbonate rock. Our modeling results showed that fluid invasion played the main role in detachment of particles and particle erosion was accompanied with few shear-induced microcracks. The borehole breakout orientation was along the maximum horizontal principal stress direction. The influence of drilling mud density on instability patterns was further analyzed through our DEM modeling.

This paper describes the results of a study conducted to assess the stability of a hazardous solid waste landfill resting on sloping ground. The base profile of the landfill was governed by the bedrock level which was at a shallow depth below the ground surface and exhibited significant elevation difference from one end to the other. The initial studies showed that the base inclination caused by the elevation difference results in planar failure through waste mass and lining system when smooth geomembrane is present in the lining system. As a consequence, an earthen berm was provided at the toe of the landfill and textured geomembrane in the lining system for stabilization. The stability was evaluated for five different rotational and translational failure slip surfaces for conditions of dry and wet waste mass, leachate head, and earthquake. The results show that the two stabilization measures generate satisfactory values of factor of safety for all conditions of analysis.

One of the main purposes of landfill cover system is to prevent the water infiltration into the waste mass and eventually minimize the generation of leachate. In this effort, the most prevalent parameter to control is the percolation of rainfall through the cover system into the waste mass. In addition to this, if the cover system utilizes an evapotranspiration (ET) or water balance cover, understanding the hydraulic behavior of soil becomes especially important. Environmental loading conditions can change drastically throughout the seasons, which in turn can substantially alter the hydraulic conductivity of the cover soil, and hence, affect the performance of the ET cover system. Therefore, assessment of seasonal variation of soil hydraulic conductivity is vital. To address this, a study was conducted on an existing ET cover in the city of Irving landfill. The objective of the study was to monitor the change in the saturated hydraulic conductivity of the ET cover soil at variable environmental conditions. Due to its versatility, the Guelph permeameter was used to estimate the in situ saturated hydraulic conductivity of the ET cover soil. However, the more commonly used Boutwell permeameter (two-stage borehole test) was also used to compare the two methods. To develop a better understanding, the selected sites were monitored monthly at depths of: 15.24 cm (6″), 30.48 cm (12″), and 60.96 cm (24″). Based on the field investigation, it was observed that the average saturated hydraulic conductivity decreased proportionally to an increase in the investigated depth. The registered saturated hydraulic conductivity value during fall (October 2016) at 15.24 cm (6″) depth (2.38×10^-5 cm/sec) was almost 100 times higher than the 60.96 cm (24″) depth (4.68×10^-7 cm/sec). Furthermore, it was observed that the saturated hydraulic conductivity of the cover soil at all of the investigated depths, varied in a cyclical pattern in accordance to the changing seasons. The highest values were logged during the summer seasons, whereas, the lowest values were observed in the winter season. Saturated hydraulic conductivity values measured at different times of the year varied as much as 100 times at corresponding depths.

Fluid flow through porous media consisting of randomly-generated mono- and binary-sized spherical particles is investigated using the lattice Boltzmann (LB) method. The effects of porosity, particle mean diameter and diameter ratio, and Reynolds number on velocity and drag force distribution in porous media are investigated. Based on the numerical results, a more accurate equation for calculation of the mean drag force in particulate porous media is proposed. Probability density distributions of velocity in pore space and drag force on individual particles are investigated and the range of variations according to the mean drag force is introduced. The results suggest that porosity and Reynolds number in mono-sized domain have the most significant effect on the mean drag force; in binary-sized domain, however, the size ratio has a significant effect.

Performance assessment of water balance cover or evapotranspiration (ET) cover is critical for waste containment as its performance largely depends on the site-specific condition. Post construction changes in the soils’ hydraulic properties, as a consequence of wetting-drying cycles, frost action, ingress of plant root, etc. may affect the cover performance. The objective of this study was to evaluate the water balance performance of ET cover in the semi-humid region of North Texas. As part of the study, a large-scale test section was constructed with drainage lysimeter (12 m×12 m) in the City of Denton landfill for continuous and direct monitoring of the water balance. The test section was constructed with 0.9 m (3 ft.) of a compacted fine-grained soil layer and 0.3 m (1 ft.) of a vegetated surface layer. Cover soil was placed over a geomembrane and a geocomposite drainage layer. An extensive field instrumentation program was implemented in the field to monitor the water balance components of the drainage lysimeter. Moisture sensors and tensiometers were installed at the site to monitor the change in soil water storage. Surface runoff and percolation collection tanks, connected to the lysimeter through HDPE pipes, were placed at the site to monitor these two components. A weather station was also installed to monitor the overall climatic condition. Based on the monitoring results accumulated after two years, drainage from the bottom of the cover soil (percolation) was recorded to be 42 mm/year and 49 mm/year (2.8% and 3.7% of precipitation) respectively. Annual percolation was identified to be significantly influenced by annul precipitation and water storage capacity of the cover soil.

Microbial induced carbonate precipitation (MICP) is a bio-mediated approach to improve engineering properties of granular materials. Cell population, substrate concentration, alkalinity, and temperature are the main factors controlling urea hydrolysis rate in the MICP process. In this study, the effects of initial substrate (urea) concentration and cell population on the rate of urea hydrolysis were evaluated using electrical conductivity as a monitoring method. For this purpose, a correlation between electrical conductivity and hydrolyzed urea concentration was derived from a batch test program. Various initial substrate concentrations and cell populations were selected in another batch test program to evaluate their contribution to the urea hydrolysis rate. Increasing both initial substrate concentration and cell population accelerated the rate as discussed in detail in this paper. Finally, a simplified column testing program was completed to demonstrate the effectiveness of electrical conductivity as a monitoring parameter during MICP treatment.

The objective of this study was to evaluate the potential of contamination by the aqueous benzene through transport in a saturated soil domain supporting subsurface concrete pipe. The focus of the study was on assessing the potential for benzene to migrate through concrete pipe and/or its joints (gaskets) for both intact and damaged conditions. A three-dimensional finite difference method (FDM), implemented through Visual MODFLOW Flex, was utilized to simulate groundwater flow and contaminant transport phenomena. Site conditions and soil parameters were selected on the basis of the average range of hydrologic parameters representative of regions in the coastal area of North Carolina. The study was conducted by varying the following parameters: i. hydraulic conductivity (k), and ii. longitudinal dispersivity (α_L). Damaged pipe and damaged gaskets scenarios were considered, as represented by k-values. No benzene broke through the pipe, even under damaged gaskets scenarios, when the saturated k_soil was 10^-5 cm/s. In this case, benzene was transported upward into the backfill soil with a higher k_backfill of 10^-3 cm/s. For damaged pipe scenarios and k_soil =10^-5 cm/s, benzene concentrations inside of the pipe remained below 5 μg/L, the maximum contaminant level (MCL) for drinking water. In the case of the saturated k_soil=10^-3 cm/s, benzene concentrations reached the MCL for the case of damaged pipe. The highest potential for aqueous benzene migration into water flowing in the pipe was when pipe damage was assumed. The simulated contaminant was not sensitive to the variations of the α_L.

Bangalore generates around 3,500 tons of municipal solid waste (MSW) per day. The current waste management practices involve preliminary mechanical and biological treatment before landfilling. Assessment of the waste management practices followed by the municipality by using life cycle analysis (LCA) is presented in this study. LCA is also used in the study to explore alternatives to the current practices and handle the waste in a more sustainable way. The analysis is performed in terms of material flow, energy flow, and the impacts of waste processing on the environment. Five impact categories consisting of global warming, acidification, eutrophication, human toxicity, and aquatic ecotoxicity potentials were investigated. The result presents the comparison of open dumping of MSW (which was practiced earlier) with the existing integrated waste management (IWM) system. Results also show that the environmental impact of IWM system with a bioreactor landfill having an energy recovery facility is lesser than the above two cases.

The Tennessee Valley Authority (TVA) has been conducting field trails and pilot projects since 2012 to evaluate new quality control/assurance methods for construction of dry stacked coal combustion residues (CCRs) at fossil plant facilities. Based on lessons learned from those studies, TVA is now implementing a method of material and plant specific field calibration procedure to establish process control and target values for quality control/assurance (QC/QA). This paper presents results of one such calibration effort performed at Cumberland Fossil Plant in Cumberland City, Tennessee. Field testing included using an instrumented vibratory smooth drum validated intelligent compaction (VIC) roller and in situ point test methods to measure moisture, dry density, modulus of subgrade reaction, shear wave velocity, and dynamic cone penetrometer resistance. Laboratory testing was conducted to assess compaction characteristics of fly ash and gypsum, and to assess influence of compaction delay and curing time on the chemically reactive fly ash material. Results from the field and laboratory testing are summarized in this paper along with the development of target values and field implementation practices.

In municipal solid waste landfills, the long-term stability and integrity of the lining systems play an important role in containing the waste and its byproducts. In fact, the modern lining systems that consist of geosynthetic components (e.g. geomembrane and geotextile) form various interfaces within the liner system which when subjected to the high stresses of the overlying waste, hold the major chances of failure and loss of integrity in the liner system. Moreover, the MSW in landfill is influenced by coupled hydraulic, mechanical, and biochemical processes simultaneously, which changes the waste characteristics over time. The system gets increasingly complex when leachate recirculation is performed as in the case of bioreactor landfills. The dynamic changes in the waste properties/characteristics due to the coupled interactions within the waste affect the waste-liner interaction and consequently affects the performance of the liner systems. This study presents a numerical investigation to evaluate the interface shear behavior of four different interfaces typically observed in composite liner systems consisting of HDPE geomembrane and nonwoven geotextile. The numerical analysis of the interface shear response was performed on a typical landfill configuration considering leachate recirculation (to simulate bioreactor conditions) in a typical representative landfill cell model. The results showed that the interface formed by smooth HDPE geomembrane and nonwoven geotextile form the critical interfaces in the liner systems. The distribution of the shear stresses along the interface varied based on the type of the interface materials. The interface shear stresses and shear displacements were found to be noticeably influenced by the contemporaneous changes in waste properties due to waste decomposition.

Among many anthropogenic sources of greenhouse gases (GHG), landfill emissions, consisting of methane (CH₄) and carbon dioxide (CO₂), are one of the major contributors of anthropogenic GHG. In recent years, various innovative landfill biocovers have been investigated and developed to mitigate the emissions of methane (CH₄) from municipal solid waste (MSW) landfills. However, the problem of CO₂ emissions [which constitute about 40% of landfill gas (LFG)] from MSW landfills still remains unresolved. An innovative cover system which consists of basic oxygen furnace (BOF) slag with biochar amended soil is being developed to mitigate CH₄ and CO₂ emissions from landfills. The biochar amended soil is effective in mitigating CH₄ emissions by microbial methane oxidation, while BOF slag could be effective in sequestering CO₂ emissions by carbonation mechanisms. However, the properties of BOF slag vary based on several factors such as mineralogical composition of slag, particle size, moisture content, and temperature. In this study, CO₂ sequestration potential of BOF slag was evaluated under synthetic LFG condition. The performance of the BOF slag in sequestering CO₂ under different moisture condition was also examined. The results showed that BOF slag can sequester substantial amount of CO₂ under LFG condition. The study also enlightened the importance of moisture for initiating carbonation reaction; however, the moisture alone was not the controlling parameter for CO₂ sequestration. The mineralogy of the BOF slag plays an important role in determining CO₂ sequestration capacity of the slag.

An emerging strategy for the management of flue gas desulfurization wastewater (FGDWW) involves volume reduction of the FGDWW by concentrating to brine and then mixing the brine with fly ash and other chemical additives to form a paste suitable for landfill disposal. This process, termed as paste encapsulation technology, has not achieved the same level of success in immobilizing halides as achieved in sequestering heavy metals, because of the high solubility and elevated concentrations of halides in the brines. The focus of this study is to synthesize and characterize AFm (alumina, ferric oxide, monosulfate) phases like Friedel’s salt (FS) in the laboratory using reagent-grade chemicals. The formation of these AFm phases in the brine-fly ash paste can enhance the encapsulation of halides in the paste. The structure and morphology of the synthesized samples were examined using thermogravimetric analysis (TGA), and x-ray diffraction (XRD). The total mass loss of FS, calculated using TGA, was comparable to the theoretical value. The XRD patterns also showed good agreement to a monoclinic layered double-hydroxide structure. Using these optimized operating variables, preliminary results of phase formation will be assessed using field materials such as fly ash, wastewater brine, and chemical binders.

Soil bentonite (SB) slurry trench cutoff walls have been widely used for over 40 years to control ground water flow through and beneath dams and levees and to control subsurface contaminant transport at contaminated sites. The idea that the state-of-stress in SB slurry trench cutoff walls is less than geostatic was first published over 30 years ago and it is well established that the hydraulic conductivity of SB backfill is stress dependent. With funding from the National Science Foundation, a full-scale, instrumented SB slurry trench cutoff wall was constructed with embedded instrumentation that directly measures the stress and pore pressure in three dimensions at multiple depths and locations. These data have been synthesized and the authors compare the results of stress measurements in this wall with various models. Finally, the authors provide summary opinions and practical recommendations for the design and construction of SB walls.

Natural fibers are commonly used in geosynthetic rolled erosion control products (RECPs). One distinguishing feature of natural fiber RECPs is their ability to absorb water. Water improves the contact and adhesion of RECPs with underlying soil, increases the ability of RECPs to absorb raindrop energy, and helps RECPs moderate soil conditions. Although water absorption is an important natural fiber RECP property, it is not typically used for design. Further, the Erosion Control Technology Council (ECTC) standard test method used to measure the absorptive capacity of natural fiber RECPs was found to produce results that varied over a wide range and did not correlate well with soil loss results obtained from rainsplash erosion tests. To address these concerns, a water uptake test was developed to measure the rate and volume of water that an RECP can absorb. This paper presents water uptake test results for eight different natural fiber RECPs. Results are correlated to soil loss results from rainsplash erosion tests. Overall, the water uptake test was found to provide useful results for the manufacture, design, and selection of RECPs.

The geocell retention system is one of the recent advancement techniques of soil reinforcement in geotechnical engineering. This paper presents an overview of the application of geocells with different infill material in retention systems and retaining walls. The paper also discusses the suitability of tire crumb mixed with sand as infill material in geocell in comparison to sand. Relative density and direct shear tests were conducted for various samples of sand-waste tire crumb mix (ST). The geocells were infilled with different proportions of sand and ST. These infilled geocells were used as facing of retaining models for laboratory static model tests. Model tests were performed on geocell retaining walls to examine the effect of the infill material in retaining structures and the failure mechanism of these structures under surcharge. Static surcharge loads up to 10,500 kg were applied using concrete blocks. Model wall response regarding displacements is also discussed.

Fly ash a waste material can be used in huge quantity in construction of retaining walls, highways, and railway embankments. In the present study, a series of laboratory plane strain model tests along with numerical simulation were performed on unreinforced and cellular reinforced fly ash slopes under uniformly distributed loading (UDL) and strip loading with an inclination of 60 degree overlaying fly ash foundation to verify the efficiency of reinforcement in improvement of load carrying capacity and stability of slope. Cellular reinforcement which is used in the current study is the post-consumer waste plastic polyethylene terephthalate (PET) bottles. Laboratory model tests were carried out by varying factors of cellular reinforcement such as diameter of geocell (50 and 75 mm) and height of geocell (10 and 20 mm) by keeping constant vertical spacing of 100 mm and length of reinforcement layer of 0.7H (where H=height of the slope). A numerical analysis using finite-element analysis (PLAXIS 3D) was conducted to validate the laboratory model test results. The dimension of the numerical model was maintained same as that of the laboratory test model. In finite-element analysis, two materials were modeled, one is fly ash as a backfill material and other one is cellular reinforcement. Here, fly ash modeled with Mohr-Coulomb failure criteria as linear elastic plastic material and waste plastic bottles as cellular reinforcement was modeled as elastoplastic material. According to numerical and experimental results, the significant values of the cellular reinforcement factors for maximum reinforcing effects were constituted and found to be reasonably good.

When subbase exists, AASHTO design of concrete pavement is based upon the composite subgrade reaction modulus. This composite modulus depends upon the resilient modulus and thickness of the subbase, modulus of subgrade reaction, and base/subgrade loss of support during pavement life. Design charts are available in AASHTO to determine the design composite reaction modulus. However, these design charts were developed based on non-stabilized subbase over subgrade. Sustainability of geotechnical practice necessitates the incorporation of recycled materials for use in pavement construction. While the inherent properties of recycled materials may not match those of their virgin counterparts, landfill space, availability of natural resources, and cost will drive industry to use recycled materials despite their properties do not match those of virgin products. Geosynthetics have been increasingly used to stabilize subbase and subgrade for roadway applications. It is expected that geosynthetic stabilization will increase the composite subgrade reaction modulus and thus allow the use of recycled subbase materials in lieu of their virgin counterparts. However, minimal research has been performed to evaluate this benefit. In this study, plate loading tests were conducted to determine the composite subgrade reaction modulus in a large geotechnical testing box at the University of Kansas. For comparison purposes, non-stabilized and geosynthetic-stabilized subbases over subgrade were constructed and tested. Modification for loss of support is proposed to capture the performance of geosynthetic-stabilized base course. This paper evaluates the benefit of the geosynthetic, the effect on the subgrade modulus, and the viability of recycled materials for rigid pavement applications.

Natural pozzolans are supplementary cementitious materials that, when used in the presence of materials with the correct chemistry, can produce a cementitious reaction. Common natural pozzolans include industrial by-products such as fly ash, calcined clay, and kiln dust, among others. The benefits of natural pozzolans in Portland cement concrete mix design are well known. The objective of this research is to determine the suitability of using a naturally occurring pozzolan, namely volcanic ash from the eruption of Mt. Mazama, for benefits such as dust abatement and unpaved roadway improvement. Mt. Mazama volcanic ash is plentiful at the ground surface in South-Central Oregon. If shown that Mt. Mazama volcanic ash has beneficial uses, and can replace Portland cement in some applications, there are potential economic and sustainability benefits for the region. This research documents the natural pozzolanic ability of the Mt. Mazama volcanic ash according to ASTM standards. A laboratory program was also carried out to determine the maximum proportions of volcanic ash in a Portland cement concrete mix design that would still produce a cementitious reaction. The laboratory program included innovative dust abatement tests and unpaved roadway penetration tests to determine if the sustainable, volcanic ash could be beneficial. Tests indicate that volcanic ash may prevent the formation of dust on unpaved roadways and may be used as a topically applied binder to loose, unpaved roads.

This paper pertain results of experimental studies carried out on bottom ash and blast furnace slag based geomaterial. The newly developed geomaterial was made by mixing bottom ash with blast furnace slag, expanded polystyrene beads, and ordinary Portland cement as binder. Present study consists of three different mix ratios 0.9%, 1.2%, and 1.5%. In the experimental study mix ratio was defined as ratio between the weight of beads and weight of bottom ash, it was expressed in percentages. The slag was added in different percentages 5%, 10%, and 15% with respect to the weight of bottom ash. The weight of cement to weight of bottom ash ratio was considered as 30%. The effect of various mix ratios, slag percentages, and curing periods on the compressive strength, stress-strain behavior, density, and initial tangent modulus of the geomaterial was studied and the results were incorporated in the paper. Cubical specimens of size 70 mm×70 mm×70 mm were used and compressive strength of geomaterial was calculated for curing periods of 14 and 28 days. For each mix ratio, compressive strength of geomaterial increased with increasing slag percentages and curing periods and it is in the range of 273 to 703 kPa. Non-linear relationship was observed between compressive stress and axial strain for all the mix ratios and curing periods. The density of prepared geomaterial was decreased considerably with addition of beads. The initial tangent modulus was increased as the compressive strength values increased. The present study results indicate that the industrial waste products such as bottom ash and blast furnace slag can be utilized effectively in geotechnical engineering applications there by reducing their amount of disposal in the environment and in the direction of sustainable development.

Contaminated sites are one of the major environmental problems faced by many countries across the globe. In the United States alone, the U.S. Environmental Protection Agency (USEPA) has identified several tens of thousands of contaminated sites that need remediation many of which are on the national priority list requiring urgent remedial action. The conventional approach to contaminated site remediation involves identifying the contaminants of concern and their site-specific risk-based allowable concentrations to which the contaminant concentrations at the site must be reduced by employing certain suitable remediation technologies. However, the choice of the remedial technology for the contaminated site remediation is largely driven by the potential of the technology to reduce the contaminant concentrations to the target risk-based levels, cost, time, and ease of implementation of the remediation technology at the site. This approach does not address the potential negative environmental impacts from the enormous use of energy and resources by the activities during remediation. Consequently, the broader environmental impacts such as the toxic air emissions, greenhouse gas (GHG) emissions, and other environmental waste streams that follow from their use are unaccounted. Hence, the net environmental benefit from the site remediation always remains questionable. In recent years a more holistic approach, the green and sustainable remediation, involving the quantification of net environmental, economic, and social impacts/benefits from site remediation activities is given great importance to promote sustainability principles in remediation. This study presents an overview on the concept of green and sustainable remediation along with the framework of triple bottom line sustainability assessment of the potential remedial alternatives in contaminated site remediation. Finally, a case study is presented that involves the application of this framework to compare the overall sustainability of potential remedial alternatives for a contaminated site.

In the Navy Yard district of south Philadelphia lies Southport, an approximately 150-acre site comprising an former seaplane hangar and a stretch of empty waterfront property with a storied past. The abandoned site was formerly used for naval operations throughout the 19^th and 20^th centuries. To transform the site into an economic driver, the Port of Philadelphia (PhilaPort) envisioned a new future marine terminal at the site with the initial development consisting of a vehicle import/export terminal. Design for the dichotomy of short-term, cost-effective site preparation, which allowed for immediate use as vehicle staging while multi-purposing for possible future heavy industrial loads, required a hybrid ground improvement program of surcharge and wick drains. Remnant fill, former foundations, undocumented former infrastructure, and soft ground conditions all provided challenges which required numerous field adjustments to allow the vehicle port to open as scheduled. Ground improvement, using surcharge, and vertical wick drains, is a well-established geotechnical technique. While post-construction total and differential settlements can be substantially reduced, total elimination of settlements is not a reasonable expectation even for a well-designed and properly constructed surcharge program. Some of the risks associated with this technique may result from variable site subsurface conditions, remnant site structures, the presence of obstructions, data interpretation, and quality of construction. At this project site, implementation of a surcharge program was well adapted to the current project site use as settlement-tolerant temporary vehicular storage, with the understanding that heavily-loaded and settlement-sensitive future structures would likely require a pile foundation or, if feasible, more extensive ground improvement measures. The purpose of this paper is to discuss some of the difficulties encountered considering the complex site history.

Rapid industrialization and urbanization has resulted in accumulation of large quantities of industrial/domestic wastes and gainful utilization of these waste materials for civil engineering applications will provide environmental friendly and sustainable solution for their disposal. In view of these requirements, a series of model footing tests were carried out to study the strength and deformation characteristics of bottom ash reinforced with geocell mattress made of waste polyethylene terephthalate (PET) bottles. Geocell mattress were made using waste PET bottles cut in to rings and tied together to form a mattress. Tests were carried out in a test tank using a square model footing with varying embedment depths and width of geocell mattress. The study reveals that the utilization of waste PET geocell mattress not only improves the strength of bottom ash but also provides a sustainable solution for waste disposal.

This study focuses on the performance of a shallow, horizontal thermal energy storage system in San Diego. Heat collected from solar thermal panels over a period of 120 days was injected into a slinky-loop heat exchanger installed at a depth of 1.2 m from the ground surface in compacted backfill soil, and the evolution in ground temperature was measured using embedded temperature sensors in the subsurface. Although the heat injection rate used in the experiment was relatively small, the field test still provides useful data for the validation of design models for horizontal heat storage systems. For an average heat injection rate of 20 W/m², the ground temperature increased to approximately 6°C greater than the ambient ground temperature expected at the depth of the heat exchanger. An analytical model for horizontal heat exchangers considering surface temperature fluctuations was calibrated against the measured data and was used to evaluate the impacts of design parameters on the storage of thermal energy in the shallow subsurface.

The tridirectional bamboo grid is a new innovative reinforcement of the limited life geotextiles (LLGs) family. It is more stable than the bidirectional bamboo grid and capable of transferring the stresses uniformly in all directions. Experimental studies of the pressure settlement behavior of single layer bamboo grid reinforced sand are introduced in this manuscript. Various laboratory model tests were performed to assess the bearing capacities of reinforced sand with the tridirectional bamboo grid and bidirectional bamboo grid. In the present study, static plate load tests were conducted in a steel tank (0.7 m×0.7 m×0.6 m) on non-reinforced and reinforced sand in the laboratory. The square model footing of size 100 mm×100 mm was used for all laboratory model tests. Two types of geogrids, namely bidirectional and a tridirectional bamboo grid made of a bamboo material of different aperture shape were utilized in the model testing. The effect of aperture shape and placement of bamboo grid at different depth ratios u/B on the bearing capacity of reinforced sand was investigated. The pressure settlement behavior of reinforced sand showed the placement of reinforcement beyond the zone of influence of depth ratio gives marginal improvement. The geometry of bamboo grid is more useful for improving the bearing capacity of reinforced sand. The experimental results indicate that the tridirectional bamboo grid provides better performance as compared to the bidirectional bamboo grid.

Rooftop farming systems deliver the benefits of rural and suburban agriculture to an urban setting by taking advantage of seldom-used roof real estate. One of the challenges preventing the industry from reaching a bigger audience is the existing building’s roof ability to withstand additional structural loads imposed by soil, vegetation, retained water, and increased activity. To help minimize added structural loads designers have used lightweight engineered soil to mimic the characteristics of natural soil. However, lightweight engineered soils have poor water retention properties which leads to the need for heavy irrigation schedules, which in turn leads to rapid leaching of nutrients. This imposes an economic deterrent to the wider use of this green technology. The conundrum leaves the designers and/or farmers with the difficult choice of sacrificing soil depth available for plant growth by adding heavier fine grained soils; or, planning for heavy irrigation schedules accompanied by nutrient loss which results in added economic liability. Through laboratory experiments, the authors have found results which indicate that the addition of repurposed textile to lightweight engineered soils has the effect of modifying the hydraulic properties of the soil without compromising its weight. The results of our experimental program are presented as well as the implications on imposed roof weights, loss of nutrients, and economic benefits of adopting the technology. By presenting this work to the geotechnical community the authors intend to create awareness to this niche technical area, where soil mechanics and structural knowledge can be used to solve problems faced by agronomists.

Based on index properties in laboratory testing, foundry sand, and blast furnace steel slag may be considered as a construction backfill alternative. Naturally available granular materials for various fill applications are fast dwindling and sometimes not readily available near every construction site. In the current scenario, there is a substantial need to use alternative geomaterials. Many industry by-products and waste materials [fly ash, copper slag, bottom ash, construction, and demolition wastes (C&D), etc.] have been extensively studied for their suitability as a geomaterial. Steel slag generation in the world was estimated to be in the range of 170–250 MT in 2015, and considerable amounts of waste foundry sand are also generated. In the present study, waste foundry sand from Ordnance Factory, Medak, India, and blast furnace (BF) steel slag from Tata Steel, Jamshedpur, India, are tested for basic characteristics including gradation, specific gravity, morphology, chemical composition, and compaction. The engineering properties, shear strength, and permeability, are evaluated. In addition, leachate studies are conducted to assess the environmental impact of use of these materials for the proposed applications. Compaction behaviour of both the materials is found to be similar to granular soils. Foundry sand and BF steel slag exhibited an angle of shearing resistance of 31⁰ and 37⁰, respectively. A comparative study on the properties of foundry sand and BF steel slag with the conventional fill material is performed, and the two waste products considered in the study are assessed for fill applications.

In New Jersey, upland confined disposal facilities (CDFs) are used to store fine-grained dredged material from the state channel network along the Atlantic coast. Many of these earthen CDFs were damaged during Superstorm Sandy, which presented an opportunity to study the New Jersey CDFs and develop geotechnical guidelines for design, and resilience of these CDFs as well as for increased operational sustainability. Drawing from the authors’ experience on over 20 upland CDFs in New Jersey since 2012, geotechnical design guidelines and lessons learned are presented and highlighted through a series of case studies to cover geotechnical investigations and construction monitoring and coordination. Further case studies emphasize geotechnical resilience engineering guidelines including: geotechnical dike composition, location-based considerations, climate change, and life-cycle considerations. Building on these guidelines, coastal CDFs, marsh enhancement using dredged material, and a hybrid upland/marsh CDF approach are presented as the next evolution in upland CDF design.

Looking at the present scenario of increase in population and demand of modern life style, sustainable municipal solid waste (MSW) management may always remain a matter of concern. The major objective of this study is to use existing Pirana landfill MSW (Ahmedabad, Gujarat) as fill material for reinforced earth (RE) wall with uniaxial geogrid reinforcement and evaluate its load-displacement characteristics under gradual incremental loadings. To fulfill this objective, sand, MSW, sand sandwiched between MSW, and mix 1(sand):3(MSW) composites were used as backfill material under dry condition. Lateral displacements were measured at 4 locations on facing panel (wall) for each load increments as 20%, 40%, of maximum theoretical load. For the most efficient MSW composite, the effect of degree of saturation and particle size characterization was measured and evaluated using displacement and earth pressure theories. From results and analysis it is concluded that MSW can be effectively used as backfill material in RE wall based on MSW-reinforcement interaction and tensile strain compatibility of reinforcement playing role in load dispersion under maximum loadings.