Related Papers
Journal of Pipeline Systems Engineering and Practice
Field Performance of In-Service Cast Iron Gas Reticulation Pipe Buried in Reactive Clay
2016 •
Jayantha Kodikara
Canadian Geotechnical Journal
An equation to predict maximum pipe stress incorporating internal and external loadings on buried pipes
2016 •
Jayantha Kodikara
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 subje...
Canadian Geotechnical Journal
Hydromechanical behaviour of overconsolidated unsaturated soil in undrained conditions
2018 •
Jayantha Kodikara
Hydromechanical behaviour of an unsaturated silt with various suctions and different overconsolidated ratios (OCRs) was investigated through a series of undrained triaxial tests (constant water contents, CW). All the samples were prepared from the slurry state. Different OCRs (= 1, 2, 4, and 8 in net stress) were achieved by unloading the samples to 400, 200, 100, and 50 kPa from an initial confining net pressure of 400 kPa. Then the samples were dried to various suctions (0, 100, 200, 300, and 400 kPa). Unsaturated samples with different OCRs were then sheared at CW conditions following the conventional triaxial compression (CTC) paths. Full hydromechanical responses including the changes in deviator stress, stress ratio, volumetric strain, suction, and degree of saturation with axial strain were monitored and are presented in this paper. Some key findings include (i) the critical state for unsaturated soils with different OCRs can be well defined by Bishop’s effective stress; (ii)...
Canadian Geotechnical Journal
Isotropic volumetric behaviour of compacted unsaturated soils within specific volume, specific water volume, mean net stress (v, vw, p) space
2019 •
Jayantha Kodikara
A detailed description of the volumetric behaviour of compacted unsaturated soils is essential for modelling compacted soil behaviour. It is more complex than when the soil is saturated, as unsaturated soils exhibit a range of responses, such as yielding under loading, swelling and collapse under wetting, and shrinkage and cracking during drying. In unsaturated modelling, (v, s, p) or (v, s, p′) is commonly used as the state space to describe volumetric behaviour, where v (= 1 + void ratio, e) is the specific volume; s is the soil suction; and p and p′ are the mean net and mean effective or skeleton stress, respectively. An alternative approach is to use (v, vw, p) space to describe volumetric behaviour, where vw is specific water volume. In either case, coupled water retention behaviour is needed to describe the overall macroscopic process more completely by including the fourth state variable (vw or degree of saturation, Sr, for the former and s for the latter). Following from wor...
Canadian Geotechnical Journal
Interpretation of the loading/wetting behaviour of compacted soils within the MPK framework: Part II Dynamic compaction
2016 •
Jayantha Kodikara
Dynamic compaction is commonly used to construct structural fills for various geo-infrastructures. Current practice is to specify a minimum dry density and moisture content criterion to be used in the field on the basis of Proctor compaction carried out in the laboratory. However, there are still no practical methods for predicting compacted clay behaviour under expected mechanical and environmental loadings. Current theories are difficult to apply in practice due to difficulties in determining the necessary parameters. In this paper, the recently developed “void ratio – moisture ratio (volume of water / volume of solids) – net stress space” (MPK) framework is extended to cover dynamically compacted soils, with significant supporting experimental evidence. Two types of soils are used: lightly reactive kaolin and reactive Merri Creek clay. As the compaction stress was unknown for dynamic compaction, recompression of soil specimens from compacted soil was used to establish the “loadin...
Canadian Geotechnical Journal
Influence of water and lubricant fluids on peak strength of Queenston shale from southern Ontario
2017 •
Hayder Al-maamori
The strength of Milton Queenston shale (MQS) before and after soaking in water and lubricant fluids (LFs) was examined. The investigated LFs (i.e., bentonite and polymer solutions) are utilized in the microtunnelling technique (MTT) to facilitate the installation of tunnel or pipe sections. To investigate the relevant mechanical properties of MQS under different wetting conditions, a series of laboratory tests including Brazilian split, uniaxial compression, and triaxial compression were carried out. These tests were performed on vertically and horizontally cored specimens with respect to the rock bedding. Fresh specimens (i.e., intact) and specimens soaked for 100 days in LFs and in water were examined. The 100 day period was selected, as it may reasonably represent the construction period where some swelling of the Queenston shale can occur. It was revealed that the strength of MQS substantially decreased after soaking. With greater impact in the vertical direction, both water and...
Canadian Geotechnical Journal
Compression and shear strength characteristics of compacted loess at high suctions
2017 •
Fardin Jafarzadeh
Compression and shear behavior of a loosely compacted loess is investigated via two series of saturated and unsaturated direct shear tests. The vapor transfer mechanism is used to modify a shear box device for control of suction at high range. In spite of significant volumetric strain upon wetting (up to 14%), suction-induced volumetric shrinkage is less than 2% for all suction levels considered because of the as-compacted moisture content at the dry side of the optimum value. During shearing, all unsaturated tests dried to high suctions indicate a strain-softening mode of failure associated with noticeable dilation. There is a continuous increase in peak strength with suction but at a reduced rate, which cannot be captured by the improved Bishop’s effective stress model, as it underestimates the contribution of high suctions by approaching zero degree of saturation. Unsaturated tests at high suctions also show an increased rate of dilation with suction for both values of net stress...
Canadian Geotechnical Journal
Effect of microstructure on shear strength and dilatancy of unsaturated loess at high suctions
2019 •
Fardin Jafarzadeh
To investigate the influences of microstructure changes on dilatancy of unsaturated loess at high suctions, a direct shear box device using the vapour equilibrium technique was used. Through conducting two series of direct shear tests on both intact and recompacted loess specimens and also investigating microstructural changes using the mercury intrusion porosimetry (MIP) technique, a linear increase in dilatancy with suctions ranging from 8 to 230 MPa can be identified at different net stresses. The enhanced dilatancy observed is mainly attributed to desiccation-induced high suctions as the reduction in void ratio due to enhancement of suction was negligible. A macrovoid ratio, eM, may be quantified and proposed to explain the differences in the increased dilatancy of recompacted and intact loess with suction.
Medium-scale laboratory model of mono-bucket foundation for installation tests in sand
2019 •
Lars Ibsen
Design implications of suction installation of bucket foundations are still not well understood. During suction installation, applied suction under the bucket lid results in seepage flow through the surrounding sand. Seepage flow plays a pivotal role in reducing the penetration resistance, allowing for full penetration despite the initial large soil resistance. However, loosening of the inside soil plug might be problematic when the soil approaches its failure stage, due to soil piping or extensive soil heave inside the bucket foundation. To better understand the interaction between the soil and bucket skirt during suction installation, this paper describes the results of medium-scale tests of bucket foundation installations in sand, comparing jacking and suction installations. Experimental measurements of the pore pressure around the bucket skirt are compared with the numerical simulation results, to validate the finite-element model and to enable analysis of the soil behavior arou...
Canadian Geotechnical Journal
Evaluation of defective sewer pipe–induced internal erosion and associated ground deformation using laboratory model test
2017 •
Samanthi Renuka
