Geotechnical engineers face several challenges when designing structures over soft soils. These include potential bearing failure, intolerable settlement, large lateral pressures and movement, and global or local instability. Geosynthetic-reinforced and pile- supported earth platforms provide an economic and effective solution for embankments, retaining walls, and storage tanks, etc. con- structed on soft soils; especially when rapid construction and/or strict deformation of the structure are required. The inclusion of geosynthetic~s! in the fill enhances the efficiency of load transfer, minimizes yielding of the soil above the pile head, and potentially reduces total and differential settlements. A numerical study has been conducted to investigate pile-soil-geosynthetic ~s! interactions by considering three major influence factors: the height of the fill, the tensile stiffness of geosynthetic, and the elastic modulus of pile material. While current methods have not fully addressed important effects of the geosynthetic stiffness and pile modulus on the soil arching ratio, numerical results suggested that the stress concentration ratio and the maximum tension in geosynthetic increase with the height of the embankment fill, the tensile stiffness of geosynthetic, and the elastic modulus of the pile material. The distribution of tension force in the geosynthetic reinforcement indicated that the maximum tension occurs near the edge of the pile.

Numerical Analysis of Geosynthetic-Reinforced and Pile-Supported Earth Platforms over Soft Soil

Bearing capacity of circular footing on geocell–sand mattress overlying clay bed with void

Laboratory Investigation on Strength Characteristics of Expansive Soil Treated with Jute Fiber Reinforcement

Water treatment sludge (WTS) management is a growing global problem for water treatment plants (WTPs) and governments. Considering the scarcity of raw materials in many parts of the planet and unique properties of WTS, extensive research has been conducted on the application of WTS in the production of construction materials such as roof tiles, bricks, lightweight aggregates, cement, concrete and geopolymers. This paper critically reviews the progress in the application of WTS in construction materials, by synthesizing results from recent studies. Research findings have revealed that incorporation of ≤10% alum-based sludge in ceramic bricks is satisfactory with a small reduction of mechanical performance. Using the iron-based sludge, the bricks presented better mechanical strength than the reference clay-bricks. Concerning WTS application in concrete, 5% replacement of cement or sand by WTS was considered as the ideal value for the application in a variety of structural and non-structural concrete without adverse effect on concrete mechanical performance. Furthermore, this paper discusses sludge-amended concrete in terms of durability, potential leaching of toxic elements and cost, and suggests topics for future research on the sustainable management of WTS.

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Progress in manufacture and properties of construction materials incorporating water treatment sludge: A review

Variation in physical and mechanical properties of fired-clay bricks incorporating ETP biosolids

The engineering behavior of one iron and two alum coagulant water-treatment plant sludges was investigated. The behavior studied included plasticity characteristics, moisture-density relation, compressibility, and shear strength. Additionally, a hypothetical disposal landfill was analyzed and discussed to demonstrate possible applications of the developed data base. The test results indicate that the sludges are extremely plastic and highly compressible. The drained shear strength is high, but the undrained strength is very low. They are also highly sensitive and thixotropic. Compared with the iron sludge, the alum sludges are more plastic and compressible, and have higher undrained shear strength at the same solids content. The moisture-density relation of the iron sludge exhibits the typical one-hump shape, whereas that of the alum sludge shows no peak formation. The results of landfill analysis indicate that the required minimum solids content for maintaining a desired slope is higher for the iron sludge than the alum sludge.

Engineering behavior of water treatment sludge

Stability of geosynthetic-reinforced soil above a cavity

This paper compares experimental results on the stabilization of clayey dredged material (DM) using quicklime (QL), hydrated lime (HL), portland cement (PC), and Class F fly ash (FA). The D...

Stabilization of Silty Clayey Dredged Material

Stability of strip footings above concrete-lined soft ground tunnels

There are cases that footings are supported by stratified soil deposits with cavities. The presence of underground cavities may adversely affect the stability of the overlying footings. At present, there is no widely accepted methodology to analyze the stability of such a footing-cavity system. To develop such an analytical method, a study on the effect of underground cavity on the bearing capacity of strip footings in two layer soils was undertaken. The study was made by means of the finite element method. For the analysis, a two-dimensional plane-strain elasto-plastic finite element computer program was developed. Using this computer program, the stability of strip footings was analyzed for a wide range of cavity conditions, soil types, and soil layer combinations. The results of the analysis provide the ultimate bearing capacity of the footing and the progress of plastic yielding of the foundation soil for each condition analyzed. Based on these results, the collapse mechanism of the footing and cavity was presented and discussed in detail. Furthermore, bearing capacity equations for strip footings on two-layer soils with cavities were formulated. The developed equations are shown to be able to provide reasonably good bearing capacity values for a range of soil layer and cavity conditions. (A)

M. Jao

Papers

Engineering behavior of water treatment sludge

Stability of geosynthetic-reinforced soil above a cavity

Stabilization of Silty Clayey Dredged Material

Stability of strip footings above concrete-lined soft ground tunnels

Cavity effect on stability of strip footing in two-layer soils