An Deng

Measuring and Modeling Proportion-Dependent Stress-Strain Behavior of EPS-Sand Mixture

A geofoam was produced by blending expanded polystyrene (EPS) beads and sands in proportions. The formed mixtures, known as EPS-sands, were 26–63% lighter than general earth fills (e.g., sand). Consolidated-drained (CD) triaxial compression tests were conducted on EPS-sand mixture specimens to observe their stress-strain characteristics, specifically, the stress-strain responses in relation to the EPS contents (0.5, 1.5, and 2.5% by weight) used in the mixtures and confining pressures (100, 200, 300 to 400 kPa) loaded on the specimens. The EPS content and confining pressure were found to influence the stress-strain and volumetric strain behavior of the mixtures. Increasing EPS content led to decreased shear strength and increased volumetric strain. Increasing confining pressures enhanced the strength of the mixture. EPS-sand mixtures underwent a shear contraction throughout the CD tests. The optimum EPS bead content (i.e., the one reasonably balancing the unit weight, strength, and deformation) was in the order of 0.5% by weight. EPS content dependent strain increment equations were derived by compromising Cam-clay and modified Cam-clay, and used to model the stress-strain characteristics of EPS-sand mixtures. The established equations were verified being able to depict the stress-strain observations of EPS-sand specimens, at least for the ranges of EPS contents and confinements considered in this study.

Excess Foundry Sand Characterization and Experimental Investigation in Controlled Low-Strength Material and Hot-Mixing Asphalt

This report provides technical data regarding the reuse of excess foundry sand. The report addresses three topics: (1) a statistically sound evaluation of the characterization of foundry sand, (2) a laboratory investigation to qualify excess foundry sand as a major component in controlled low-strength material (CLSM), and (3) the identification of the best methods for using foundry sand as a replacement for natural aggregates for construction purposes, specifically in asphalt paving materials. The survival analysis statistical technique was used to characterize foundry sand over a full spectrum of general chemical parameters, metallic elements, and organic compounds regarding bulk analysis and leachate characterization. Not limited to characterization and environmental impact, foundry sand was evaluated by factor analyses, which contributes to proper selection of factor and maximization of the reuse marketplace for foundry sand. Regarding the integration of foundry sand into CLSM, excavatable CLSM and structural CLSM containing different types of excess foundry sands were investigated through laboratory experiments. Foundry sand was approved to constitute a major component in CLSM. Regarding the integration of foundry sand into asphalt paving materials, the optimum asphalt content was determined for each mixture, as well as the bulk density, maximum density, asphalt absorption, and air voids at N{sub ini}, N{sub des}, and N{sub max}. It was found that foundry sands can be used as an aggregate in hot-mix asphalt production, but each sand should be evaluated individually. Foundry sands tend to lower the strength of mixtures and also may make them more susceptible to moisture damage. Finally, traditional anti-stripping additives may decrease the moisture sensitivity of a mixture containing foundry sand, but not to the level allowed by most highway agencies.

Contaminants in waste foundry sand and its leachate.

The environmental characteristics of Waste Foundry Sands (WFS), including chemicals in WFS and its leachate, are essential in understanding the environmental impact, rational disposal and potential development of beneficial applications of this solid industrial waste. This paper presents an assessment of broad-spectrum chemicals (metallic, non-metallic and organic chemicals) in aspects of their statistics (mean, median and the 95th percentile) in dry-weight WFS and WFS leachates based on laboratory measurements of 594 WFS samples from 123 foundry facilities in the USA. Results indicate that WFS is basically not hazardous except a risk associated with WFS from copper-based foundry facilities. Leachability of metallic chemicals varies among investigated WFS. A clear delineation between different leaching protocols is implicated.

Modeling Electroosmosis and Surcharge Preloading Consolidation. I: Model Formulation

AbstractA numerical model, EC2, is developed to simulate the consolidation of a soil layer subjected to combined electroosmosis and surcharge preloading. EC2 includes the capabilities of a previous model, EC1, in accounting for large-strain-induced nonlinear changes in the physical and geoelectrical properties that take place on a layer, with the additions of two-dimensional consolidation, coupled loading and electric fields, time-dependent loading and current density, and an external hydraulic gradient. A highlight of the EC2 model is the superposition of multiple streams between small elements, which improves the prediction accuracy of the rate of flow and the degree of consolidation. The consolidation algorithm of EC2 is one-dimensional and conducted using finite-difference and piecewise-linear methods. This paper presents the theoretical and numerical development of the EC2 model. A companion paper presents the validation of the model and the results of simulations that illustrate the optimization of ...

Conversion of Sewage Sludge to Biosolids

With the increasing generation of sewage sludge, its proper handling and disposal play a critical role in protecting our environment. Sustainable sludge treatment and management depend on controlling the quantity, quality, and characteristics of biosolids in favor of efficient sludge handling and biosolids beneficial use. One of the ultimate goals in the treatment is to convert sludge into biosolids or a product subject to subsequent treatment, in simplified operations that are cost-effective and environmentally safe. This chapter discusses the main treatment processes—clarification, stabilization, conditioning, thickening, dewatering, and drying—of sludge. The principle, operation, relevant diagrams, and criteria of each treatment method are presented. A case study of sludge management operation is also included.

A sulphonated oil for stabilisation of expansive soils

ABSTRACT The efficiency of a commercially manufactured sulphonated oil (SO) agent in treating a highly expansive soil was investigated through an extensive experimental program. A total of six SO to water mass concentrations, i.e. 0.25, 0.5, 0.75, 1, 1.25 and 2.5%, were examined. The test program included swell–load oedometer, unconfined compressive strength and cyclic wetting and drying tests. SO-stabilisation amended the soil’s mechanical behaviour through improvements achieved in swelling and strength characteristics. The reduction in swelling potential and swelling pressure was dependent on SO concentration, while the effect of curing time was found to be insignificant. A similar dependency was concluded for the unconfined compressive strength and stiffness of the stabilised soil. Both dependencies suggested an SO concentration of 1.25% capable of yielding an optimal stabilisation scheme. Results of the cyclic wetting and drying tests indicated that the beneficiary effects of SO-stabilisation at optimum concentration, particularly in ameliorating the adverse effects of swell–shrink-related volume changes and to some extent increasing the strength, are strongly preserved under the influence of alternate wetting and drying.

Consolidating dredge soil by combining vacuum and dynamic compaction effort.

Escalating lands are being reclaimed at coastal areas by dredging soils from sea or rivers. Such formed lands are often characterized as presenting high water content, high void ratio, high compression, worst disturbance and weak bearing capacity, and thus cannot be directly used as a bearing deposit. It is time consuming to consolidate such -lands by relying on naturally occurring evaporation and hydraulic dissipation. Enhanced engineered technology has to be introduced to expedite the dredge consolidation process. A technology, known as high vacuum densification method (HVDM), was developed to treat the dredge soil in a time-efficient and cost-effective means. Its principle is to consolidate the soil by combining vacuum effort and dynamic compaction. The vacuum effort is used to pump the moisture out of the soils in steps; and the drained soils are densified by dynamic compactions. Soils amenable to HVDM can be treated to favorable conditions meeting both strength and deformation requirements. Besides the principles and the construction procedures of HVDM, cases studies were also presented in this paper, which demonstrates the attractive merits of HVDM in contrast to comparable soil treatment methods.

Mechanism and Prevention of Highway Distress in Seasonal Frost area

Frozen damage to highways in colder climates, including frost heaving because of ice lenses growth and thaw weakening caused by ice lenses melting. The frost action reacts on the highway structure that is a major concern at the locations constructing a highway in cold regions, and the frozen damage of road is a phenomenon of great practical importance in highway engineering design and construction. The objectives of this paper are to: (1) study the effects of frozen damage on road performance in cold climate regions, (2) investigate the factors contributing to the changes in highway structure physical and mechanical properties, (3)provide guidelines for anti-freezing design of highway in seasonal frost areas. The approach focuses on analyzing the characteristics and the mechanisms of frost heaving and frost boiling, and adopting initiative methods to reduce the frozen damage to highways. This thesis gives a review and summary of the preventive measures to minimize highway distress in seasonally frozen regions that will benefit the design and maintenance for highway structure.

Modeling Electroosmosis and Surcharge Preloading Consolidation. II: Validation and Simulation Results

AbstractThe results of numerical simulations for electroosmosis–surcharge preloading consolidation, obtained using the EC2 model, are presented. EC2 accounts for hydraulic and electroosmotic flows under the conditions of changing physical and geoelectrical properties of saturated compressible porous media. Verification checks for EC2 show excellent agreement of the pore pressure and degree of consolidation with analytical solutions for one- and two-dimensional small-strain consolidation. Similarly, excellent agreement is attained for two-dimensional large-strain consolidation occurring to a kaolinite layer subjected to an experimental test. The EC2 model is then used to investigate consolidation optimization for soil layers in three example problems. The electroosmosis–surcharge preloading combined method outperformed single-process methods, particularly where hydraulic conductivity is on an order of magnitude of 10−8  m/s or lower. Applying voltage in steps optimizes electric power usage, as does cutting...

Granular Lightweight Fill Composed of Sand and Tire Scrap

A granular geomaterial, known as sand-tire lightweight fill, was proposed by blending sand with disposed tire scrap in proportions. The geomaterial can be used as alternative backfill in many infrastructure works, where less overburdens and lateral loads are expected. The reuse of tire scraps may not only address growing environmental and economic concerns, but also help solve geotechnical problems associated with low soil shear strength. In this study, an experimental testing program was undertaken with the goal of evaluating the compression and shear behavior of the materials. Three tests were implemented, i.e., 1-D compression tests, direct shear tests and consolidated drained triaxial compression tests. A compression strain-load model was proposed to describe its compression behavior. Rebound-reload tests revealed that materials’ plastic deformation was associated with the mixing ratios. The tire scrap content was found to influence the stress-strain and volumetric strain behavior of the mixtures. Mixtures underwent shear contraction during shearing processes, which is different from the shear dilation of compact sands. Effects of mixing ratios and stress conditions on shear deformation behaviors were also discussed.