Pipelines used for water and other services are very important lifelines in modern society. Commonly, these buried pipes are subjected to significant stresses due to external (traffic and earth) and internal (water pressure) loads. As many of these pipelines were laid sometime in the last century or earlier, in most cases their condition has deteriorated primarily by electrochemical and (or) microbiological corrosion. Corrosion activity (internal and external) can manifest in various forms, but in many cases will lead to reduced pipe thickness, which in turn leads to an increase in pipe stresses induced by the external and internal loads. Currently available analytical procedures to estimate pipe stresses are based on oversimplifications such as the two-dimensional (2-D) analysis based on Winkler springs, limiting their application to general pipe burial conditions. This paper describes the application of a three-dimensional (3-D) finite element method to analyse a buried pipe subjected to external and internal loads. Firstly, the finite element model is validated against the data from field tests conducted on the basis of a cast iron pipe that was laid in 1930 at Strathfield, Sydney, Australia. The results of these 3-D finite element analyses are then used to develop a closed-form expression to predict maximum stresses in pipes of different sizes buried in different soil types. Having obtained a good agreement between the proposed model outcomes and the 3-D finite element analysis results, the proposed model has been validated against the field test data under different internal and external loadings. The verified outcomes of the model reveal that it can be used to predict maximum stresses without conducting a full-scale finite element analysis, which often requires specific computational resources and computational skills. Furthermore, the proposed model can be used in probabilistic analyses, where a large number of calculations need to be carried out to account for the uncertainty of the input variables. The applications of the model are also discussed in relation to the assessment of pipe performance and remaining safe life.

Enzyme-based soil stabilizers have been successfully used in ground applications for the last 30 years. However, the successful application of a given enzyme-based additive is case specific and depends on soil type, soil condition, and operational loads. As a result, contractors incur a substantial cost in terms of time and money for preliminary lab tests, which may determine the suitable mix proportions to utilize in the field application. A sound understanding of the stabilization mechanism of these additives can minimize these costs and yield optimum benefits from the stabilization process. This paper investigates the stabilization effects of a novel enzyme-based additive, commercially known as Eko Soil, that is being applied to construct unpaved roads in Australia and worldwide. The aim of this research is to identify the optimized mix proportions of the additive by unveiling its mechanism of stabilization for a fine-grained field soil, which is dominant in Victoria, Australia. A series of experiments were conducted under a 4-stage test program that included macroscale mechanical tests and microscale imaging tests to unveil stabilization effects and the mechanism of stabilization. The identified mechanism has facilitated enhancement in the efficiency of enzyme-based soil stabilization significantly compared to the strength of nonstabilized soil. The research will substantially benefit the road construction industry by not only replacing traditional construction methods with economical/reliable approaches, but also providing insight on the optimum additive amount required to stabilize road pavements based on this stabilization mechanism.

Because pipelines traverse large geographical areas, they frequently must cross active faults when constructed in locations vulnerable to earthquakes. In this study, the authors performed three-dimensional (3D) finite-element analyses to investigate the behavior of buried pipe subject to strike-slip fault movement in dry sand and, more realistically, in partially saturated sand. The performance of the finite-element model was first validated by comparing the computed results with the data from the full-scale experiments at Cornell University. The analysis was then extended by varying the initial conditions of the sand (e.g., sand type, density, moisture content), pipe material, pipe burial depth, and pipeline–fault-rupture inclination to assess the effect of these parameters on the soil loads applied to the pipe and the corresponding deformations. On the basis of the simulation results, the authors propose a soil–structure interaction mechanism for pipelines crossing active faults. The authors als...

Expansive clays feature high compressibility and large swelling-shrinkage potential, which may cause significant damage to the infrastructures, including pavements. This study investigates the potential use of industrial waste ash generated from municipal solid waste incineration (MSWI) as a more sustainable treatment method to treat expansive soils compared to the use of conventional coal fly ash. A series of tests was conducted to study the mechanical, durability, and environmental performance of the MSWI fly ash in comparison with the coal fly ash. The study reveals that the compressive strength and resilient modulus of 20% MSWI fly ash treated sample increased to 0.86 MPa and 213 MPa respectively, depicting an increase of 150% and 240% of the control clay specimen. Results also indicate that MSWI treated expansive clay shows better performance during the soaked California bearing ratio (CBR) testings, moisture susceptibility and cyclic wetting–drying tests compared to coal fly ash treated samples. Microlevel investigations reveal that the influence of cation exchange is more decisive in the MSWI-treated clays due to the presence of higher Ca²⁺ ions, during the early stages, and the influence of hydration is stronger at the later stage of stabilisation. X-ray diffraction (XRD) results show that gismondine, albite, calcite, portlandite, andradite, and ettringite are the main crystalline phases formed during the stabilization. Heavy metal concentrations after the stabilisation are within the allowable limit defined by state regulations. Applying MSWI fly ash as a ground treatment for expansive clays can reduce the consumption of natural resources, promoting a “zero landfill” policy.