Role of geotechnical engineering in assuring the integrity of buried pipeline systems

Buried pipeline systems form a major part of global infrastructure that threads the human-made physical environment, contributing to the health, safety, and welfare of communities. Satisfactory performance of these pipeline systems, therefore, has become a key factor in assuring a sustainably built environment since any significant disruption to them often translates into undesirable impacts on economies or the living conditions of citizens. Geotechnical engineering has a dominant role to play in ensuring satisfactory performance of buried pipelines. Adequate knowledge of site-specific soil and groundwater conditions is critical to the design of pipelines, as well as ensuring good predictions of their field performance. Quantification of anticipated geotechnical hazards and evaluation of their impacts are other important considerations in assessing the long-term performance of buried pipelines. The interaction between buried pipes and surrounding soil is complex. Therefore, approaches ranging from those based on simplified assumptions to sophisticated numerical modeling techniques need to be employed in solving soil-pipe interaction problems. The overall goal is to reduce the risk of damage to buried pipelines from geotechnical hazards. A spectrum of options such as isolation from the hazard, accommodation of the hazard, or mitigation of the hazard using ground improvement can be considered in this regard

A framework for providing a lifelong social security system for the operational workforce in the construction industry in Sri Lanka

Construction is a projectised industry. One of the important resource requirements for construction projects is the availability of an operational workforce for its physical production. Hence, the operational workforce is a critical deciding factor in the success and failure of construction projects.The construction sector in Sri Lanka is suffering from a shortage of a required operational workforce for its physical operations even though the unemployment rate in Sri Lanka is about 5.2%. Research has further highlighted that “work” and “pay” are only the surface factors, hiding underneath them (Similar to an iceberg) are a multitude of different problems and the psychological needs of the workers. In addition to the shortage, there is a lack of an organised structure for human resources, which delivers time, cost and quality related behavioural constraints within the construction industry of Sri Lanka since circa the 1980’s. The aim of the research is to develop a sustainable framework for a lifelong social security system for the operational workforce of the construction industry in Sri Lanka without increasing the prevailing construction costs. The hypothesis is the minimising of resource wastages and behavioural impacts of current practices and the introduction a secured future life through a new system of lifelong social security [PR/SS] for the operational workforce. It is anticipated that the finances required for providing a social security system can be salvaged from the recovery values of material and time wastages and the demand and supply impacts generated as repercussions from the behavioural practices of the current operational workforce.The research instruments used for gathering primary and secondary data for evaluating the financial impacts of behavioural constraints were a questionnaire survey and audited financial statements. About 400 questionnaires (That were premeditated to calculate the finical impacts of the social behaviors of the construction operatives via ‘degree of importance’ and ‘relative important index’) were distributed to higher management of contracting organisations in Sri Lanka. A further request was made to the contracting organisations to provide audited statements for the past five years. From the research, it was identified that the unavailability of a human resources structure is a major constraint for the construction industry in Sri Lanka. Salvaged finances that could derive from the removal of the transitional layers of risk multiplication and the removal of the behavioural constraints of the construction operatives are sufficient to finance a lifelong social security system for themselves. Based on the research findings, a framework for the Building Forces of Sri Lanka [BFSL] was developed to overcome from the interim thinking pattern of the current construction operatives. In the current system, contracting organisations are not capable of providing the required training for the operatives. With the implementation of BFSL alongside the strong intervention from statutory organisations, a trained operational workforce can be developed to face any situation within the construction arena in Sri Lanka

Tephra layers : a controlling factor on submarine translational sliding?

Submarine slope failures occur at all continental margins, but the processes generating different mass wasting phenomena remain poorly understood. Multibeam bathymetry mapping of the Middle America Trench reveals numerous continental slope failures of different dimensions and origin. For example, large rotational slumps have been interpreted to be caused by slope collapse in the wake of subducting seamounts. In contrast, the mechanisms generating translational slides have not yet been described. Lithology, shear strength measurements, density, and pore water alkalinity from a sediment core across a slide plane indicate that a few centimeters thick intercalated volcanic tephra layer marks the detachment surface. The ash layer can be correlated to the San Antonio tephra, emplaced by the 6000 year old caldera-forming eruption from Masaya-Caldera, Nicaragua. The distal deposits of this eruption are widespread along the continental slope and ocean plate offshore Nicaragua. Grain size measurements permit us to estimate the reconstruction of the original ash layer thickness at the investigated slide. Direct shear test experiments on Middle American ashes show a high volume reduction during shearing. This indicates that marine tephra layers have the highest hydraulic conductivity of the different types of slope sediment, enabling significant volume reduction to take place under undrained conditions. This makes ash layers mechanically distinct within slope sediment sequences. Here we propose a mechanism by which ash layers may become weak planes that promote translational sliding. The mechanism implies that ground shaking by large earthquakes induces rearrangement of ash shards causing their compaction (volume reduction) and produces a rapid accumulation of water in the upper part of the layer that is capped by impermeable clay. The water-rich veneer abruptly reduces shear strength, creating a detachment plane for translational sliding. Tephra layers might act as slide detachment planes at convergent margins of subducting zones, at submarine slopes of volcanic islands, and at submerged volcano slopes in lakes

A study of principle stress rotation on granular soils using DEM simulation of hollow cylinder test

This study presents a numerical modelling of HCT (Hollow Cylinder Test) using DEM (Discrete Element Method) by developing of TRUBAL code on granular soils. Due to high expenditures of HCT, a verified numerical modelling of this test was developed. In addition, this numerical model can be used to address the gap in understanding the relationship between the particle-scale interactions and the overall material response. In the introduced numerical model (HCTBALL), plane and cylindrical walls were defined to apply the boundary forces and stresses. Also, an efficient method was presented to apply the torque. The displacements of inner and outer walls were interdependent while applying the torsion to control the intermediate principal stress parameter (b). To verify the model, the results of experimental hollow cylinder tests on Firoozkooh sand under monotonic loading and drained condition were employed. Therefore, the simulations were compared qualitatively with experiments to verify the presented model. It is observed that the deviatoric stress at failure, increased with a decreasing rate by increasing the confining pressure. By increasing the rotation angle of principal stress direction, the difference between deviatoric stresses in specific confining pressures was decreased

Chemistry of black leaf films synthesised using rail steels and their influence on the low friction mechanism

Fallen leaves are the main issues for train operations in the autumn season due to their low friction coefficient (COF), leading to signals being passed dangerously and amended timetables. The main aim of this study was to elucidate the mechanism of low friction due to black leaf films, which are often seen on leaf-contaminated rails. A black material was successfully synthesised in the laboratory with water extracts from sycamore leaves and a plate of R260 rail steel. The black powder made from the extracts of brown leaves (BBP) was identified as the key material of low friction by the pin-on-flat tribological test, giving a COF between 0.08 and 0.14, which was lower than the COF of commercial engine oil (approximately 0.14). X-Ray fluorescence showed that the black material was a mixture of iron and leaf-organics. Laser Raman spectroscopy revealed that graphite-like carbon was likely to be formed on iron oxides. Fourier transform infrared spectroscopy showed that the formation of iron carboxylate was likely in bulk, which possibly transformed into iron oxides on the surface. Moreover, X-ray photoelectron spectroscopy detected a relatively high concentration of phosphates only in BBP. Hence, the low friction is presumably due to graphitic carbon, iron oxides and phosphate compounds in the black leaf films, as well as mechanical separation effects of bulk leaves. This black material could be a product of the Maillard reaction or reaction between iron and organic acids, such as tannic acids

Motivating blue collar workforce towards construction industry

The fundamental purpose of this study is to recognise the reasons for scarcity of the Blue Collar Workforce in construction industry today and highlight its impact, and to forward my recommendations with an intention of resolving the issue. As a Construction Professional, my great concern is, what will happen to the industry, if we keep on neglecting the people who brings the desires of clients, blended with innovativeness of architects, strengthened by engineers, enumerated by quantity surveyors, documented by contract administrators into reality according to the sequence of planning engineers, performed by builders and contractors, if no proper Blue Collar Workforce is available. Professionals such as client advisors, architects, engineers, quantity surveyors, planning engineers, contract administrators, builders, contractors etc. are working towards the future of the industry. Series of professional bodies are supporting them to develop their career status stanchion with professional development programmes, seminars, exhibitions, award ceremonies, annual general meetings, day outings, dinners and so on. Although there are thousands of Research Papers available in various means of publishing, I was unable to locate a single article addressing how to motivate people towards the core layer of the Construction Industry or to discuss the problems they are being experienced by the foundation layer of the industry. Hence, I have selected 'Motivating Blue Collar Workforce towards Construction Industry' as my research project for partial fulfillment of the requirement for the MSc in Construction Project Management at the Faculty of Civil Engineering, University of Moratuwa, Sri Lanka

Constant volume friction angle of granular materials

The postulate that the constant volume friction angle Φ[sub cv] of a granular material is unique is verified experimentally. The constant volume friction angle of a wide spectrum of granular granular materials is measured using the ring shear device, enabling the material to be sheared to large, in fact unlimited strains at which 0cv is mobilized. Granular materials tested were composed of particles ranging from minerals to metals. The effects of confining pressure, initial packing density, particle size, gradation and particle shape on the value of Φ[sub cv] are studied. The possible influence of the presence of pore water is also investigated. The test results indicate that for a given material, Φ[sub cv] is independent of confining pressure, initial packing density and particle size. Neither particle crushing nor change in shape of the particle had any noticeable effect on the observed value of Φ[sub cv]. These experimental results suggest that the constant volume friction angle is a fundamental property of a granular material which is dependent only on the mineral constituency of the material. A comparison of Φ[sub cv] and the friction angle mobilized at the point of maximum contraction in drained shear (a transient constant volume state) as well as the friction angle mobilized at phase transformation state in undrained shear (a transient constant pore pressure state) is also made, in an attempt to seek a broader fundamental significance of Φ[sub cv].Applied Science, Faculty ofCivil Engineering, Department ofGraduat

Behaviour of sand under simultaneous increase in stress ratio and rotation of principal stresses

Drained behaviour of sands under simultaneous increase in stress ratio and principal stress rotation is investigated. The hollow cylinder torsional (HCT) device which permits independent control of four stress parameters: mean normal stress σ'[subscript]m, stress ratio R, intermediate principal stress parameter b and the inclination α[subscript]σ of σ'₁ to the vertical, is adopted as the testing device. In order to conduct complex stress path testing in the HCT device, a new automatic stress path control system is developed. The stress non-uniformities due to the curvature of the HCT specimen is assessed using an incremental elastic representation of sand behaviour, in order to delineate the domain of stress space that could reliably be explored using the HCT device. It is shown that previous assessments of stress non-uniformities assuming linear elastic soil grossly overestimate the stress non-uniformities in a HCT sand specimen. A much larger domain of stress space with acceptable levels of non-uniformities is apparent from the results of incremental elastic analysis. New domain of stress space for reliable exploration using the HCT device is delineated and the testing program is developed so that all stress paths lie within these acceptable limits. Tests are carried out on pluviated sand under saturated drained conditions. The deformations under increasing R and α[subscript]σ is shown to be path independent, if the final stress state is within the approximate bounds of R ≤ 2 and α[subscript]σ ≤ 45°, regardless of the b or relative density D[subscript]r, levels. With increasing stress ratio R and/or principal stress rotation α[subscript]σ, the deformations gradually become path dependent. Once loaded to a stress state within the domain R ≤ 2 and α[subscript]σ ≤ 45°, the strain response under subsequent principal stress rotation is shown to be independent of the previous loading history. It is demonstrated that the strain response under any general increasing R - α path in the domain of R ≤ 2 and α[subscript]σ ≤ 45° can be predicted using the results of a limited number of tests characterizing that domain. It is shown that these concepts can be extended to loading paths which involve simultaneous increase of three stress parameters. Strain increment direction α[subscript]Δε is shown to be approximately coincident with and totally governed by the stress increment direction α[subscript]Δσ when the stress increment direction α[subscript]Δσ is more inclined towards the vertical deposition direction. When the stress increment direction is inclined closer to the bedding plane, the strain increment direction depends in addition, on other parameters such as R, α[subscript]σ and R[subscript]r etc. Under any stress path involving principal stress rotation, the deformations decrease with increasing density and therefore the principal stress rotation is more crucial in loose sands. Deformations increase with the level of stress ratio R. Level of b parameter does not affect deformations under principal stress rotation, if the rotations are small. However, with increasing α[subscript]σ deformations due to principal stress rotation tend to increase with decreasing b value.Applied Science, Faculty ofCivil Engineering, Department ofGraduat