Conference Papers & Presentations (Civil Engineering)

Permanent URI for this collectionhttp://hdl.handle.net/2263/3887

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Now showing 1 - 20 of 68

Using shear modulus to predict the bearing capacity of strip foundations on sand
(EDP Sciences, 2024-07) Murison, Ruan A.; Heymann, Gerhard; ruan.murison@tuks.co.za
This paper reports results of a study to predict load-settlement behaviour of strip foundations on a dry uncemented sand using only soil stiffness data, under both working loads and extreme loads. This involved predicting the strength of a foundation system without using any strength parameters. A non-linear stepwise load-settlement prediction algorithm was utilised, which used the small-strain shear modulus of layers below the footing, a suitable stiffness modulus reduction curve and elasticity theory. The algorithm was adapted to predict the ultimate bearing capacity, as well as to construct a stress-settlement curve and determine the bearing pressure experienced beneath a foundation at any particular settlement. The method was evaluated using two different sets of modulus reduction curves, for small-scale model foundations on loose, medium dense and dense sand. Model tests were conducted at 1g. Particle Image Velocimetry (PIV) was used to observe strains within the soil during loading. These strains were used to calculate the shear modulus of discrete layers throughout loading and back-estimate the layer small-strain shear moduli. Additionally, the mode of shear failure for each test at ultimate bearing capacity was observed using PIV. Modulus reduction curves that initially degrade shear modulus rapidly beyond the elastic threshold strain (0.001%) gave superior predictions under the given conditions. Using such curves, ultimate bearing capacity predictions produced errors of 0.4% to 10.8%. Using the same input parameters, stresssettlement predictions were of satisfactory accuracy over the entire settlement range.
Pore pressure response during tube sampling in gold tailings
(EDP Sciences, 2023) McDonald, Gregory Darren; De Lange, Wallace; Jacobsz, Schalk Willem
Capturing the in-situ state of mine tailings is important in determining its behaviour under loading for evaluating the risk of failure of tailings dams. Obtaining a high-quality undisturbed sample through tube sampling is thus of great value to the responsible engineer. However, the sampling process itself disturbs the soil and changes its state. Since soil behaviour is driven by effective stress, one method to evaluate the disturbance induced during tube sampling is to monitor the soil’s positive and negative pore water pressure response during the process. A laboratory study was conducted where tailings samples were prepared at a controlled void ratio and subsequently saturated with water. Tube samplers of different diameters were driven into the material and extracted by means of an electric actuator during which internal sample pore pressures were monitored using tensiometers. The material experienced significant instantaneous contractive and dilative tendencies during insertion. Instantaneous negative responses during extraction of the tube samplers were also measured. It was found that the largest tube sampler (100mm diameter) performed best in the study.
Investigation of piled foundations in swelling clays
(EDP Sciences, 2023) Gaspar, Tiago Alexandre Valentim; Jacobsz, Schalk Willem; Osman, Ashraf S.
This paper presents the results of element testing and centrifuge modelling to investigate the behaviour of piled foundations in swelling clays. The study revealed that the preparation procedure implemented, was able to retain key hydromechanical properties when compared with undisturbed specimens. Furthermore, the preparation method utilised to create an artificially ‘fissured’ fabric allowed for significant swell magnitudes to be achieved in the centrifuge within a reasonable timeframe. Centrifuge testing illustrated that, at lower magnitudes of swell, increases in lateral pressure against a pile shaft can increase shaft capacity. However, if swell is allowed to continue to large magnitudes, the effects of swellinduced softening tend to dominate, thus resulting in a reduction in shaft capacity. The effects of swellinduced softening are more prominent close to the clay surface where swell is allowed to occur more freely. However, at greater depths where swell is restricted, so too are the effects of swell-induced softening, resulting in local increases in shaft capacity at greater depths.
Evaluating the performance of three sensor types for long-term measurement of suctions in gold tailings
(EDP Sciences, 2023) Narainsamy, Yashay; Jacobsz, Schalk Willem
Please read abstract in article.
Drying and wetting soil-water retention behaviour of a highly expansive clay under varying initial density
(EDP Sciences, 2023) Murison, Ruan A.; Jacobsz, Schalk Willem; Gaspar, Tiago Alexandre Valentim; Da Silva Burke, Talia Simone; Osman, Ashraf S.; ruan.murison@tuks.co.za
Expansive (or swelling) clays are the most prolific problem soil across Southern Africa and many parts of the world. Large volume changes due to seasonal wetting and drying cause millions of dollars’ worth of damage to engineering infrastructure yearly. Soil-water retention behaviour is dependent on density, and determining the correct retention curve may be key for reliable design of infrastructure. Soilwater retention curves and shrinkage curves were measured for recompacted samples of a highly expansive bentonite clay from South Africa. Four samples were prepared at varying initial dry densities between approximately 1200 and 1500 kg/m3 and subjected to total suction testing in a dewpoint hygrometer. The water content of each sample was varied through wetting and drying. The sample volume was measured after each suction reading, allowing relationships between suction and void ratio, degree of saturation and water content to be determined. The relationship between gravimetric water content and suction was not significantly influenced by initial density. Degree of saturation at a given suction varied significantly according to initial density. Volume reductions of 25% to 36% from saturated to residual conditions were recorded, and samples tended to a residual void ratio of 0.35 to 0.4. The swelling clay showed propensity for maintaining high suctions (over 300 MPa at residual conditions) and hysteretic response between primary drying and wetting.
Gauteng toll roads: an overview of issues and perspectives
(Document Transformation Technologies, July 2012) Southern African Transport Conference (31st : 2012 : Pretoria, South Africa); Minister of Transport, South Africa; Pienaar, P.A. (Petrus)
Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.
The effectiveness of Bus Rapid Transit as part of a poverty-reduction strategy: some early impacts in Johannesburg
(Document Transformation Technologies, July 2012) Southern African Transport Conference (31st : 2012 : Pretoria, South Africa); Minister of Transport, South Africa; Vaz, Eunice; Venter, C.J. (Christoffel Jacobus)
Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.
A case study of permeability determination at longitudinal joints on an airport asphalt pavement
(Document Transformation Technologies, July 2012) Horak, A.B.M.; Horak, Emile; Southern African Transport Conference (31st : 2012 : Pretoria, South Africa); Minister of Transport, South Africa; Steyn, Wynand Jacobus Van der Merwe
Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.
Application of laser based technology to quantify shape properties of railway ballast
(Document Transformation Technologies, July 2012) Mvelase, Gculisile Mavis; Anochie-Boateng, Joseph K.; Southern African Transport Conference (31st : 2012 : Pretoria, South Africa); Minister of Transport, South Africa; Grabe, Petrus Johannes
Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.
Characterising railway substructure layers for rehabilitation design
(Document Transformation Technologies, July 2012) Van Vreden, Pieter H.; Hartman, Anton M.; Southern African Transport Conference (31st : 2012 : Pretoria, South Africa); Minister of Transport, South Africa; Grabe, Petrus Johannes
Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.
Influence of road roughness on the transportation of fresh produce
(Document Transformation Technologies, July 2012) Southern African Transport Conference (31st : 2012 : Pretoria, South Africa); Minister of Transport, South Africa; Pretorius, C.J. (Lientjie); Steyn, Wynand Jacobus Van der Merwe
Paper presented at the 31st Annual Southern African Transport Conference 9-12 July 2012 "Getting Southern Africa to Work", CSIR International Convention Centre, Pretoria, South Africa.
Location, mobility and access toork: Aqualitative exploration in low-income settlements.
(Document Transformation Technologies, 2011-07) Cross, Catherine; Southern African Transport Conference (30th : 2011 : Pretoria, South Africa); Transportation Research Board of the National Academies (TRB); Minister of Transport, South Africa; Venter, C.J. (Christoffel Jacobus)
Paper presented at the 30th Annual Southern African Transport Conference 11-14 July 2011 "Africa on the Move", CSIR International Convention Centre, Pretoria, South Africa.
Comparative study of non-destructive field testing devices on BSM- emulsion
(Document Transformation Technologies, 2010-08) Guiamba, D.; Horak, Emile; Southern African Transport Conference (29th : 2010 : Pretoria, South Africa); Transportation Research Board of the National Academies (TRB); Visser, Alex T.
Paper presented at the 29th Annual Southern African Transport Conference 16 - 19 August 2010 "Walk Together", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT:
Test and application of stated preference and mixed logit modelling techniques for travel behaviour research in a rural context
(Document Transformation Technologies, 2010-08) Venkatesh, Anand; Southern African Transport Conference (29th : 2010 : Pretoria, South Africa); Transportation Research Board of the National Academies (TRB); Venter, C.J. (Christoffel Jacobus)
Paper presented at the 29th Annual Southern African Transport Conference 16 - 19 August 2010 "Walk Together", CSIR International Convention Centre, Pretoria, South Africa. ABSTRACT:
Unravelling public transport customer satisfaction and dissatisfaction dynamics in the high-end middle class market
(Document Transformation Technologies, 2010-08) Mokonyama, Mathetha; Lehasa, S.; Southern African Transport Conference (29th : 2010 : Pretoria, South Africa); Transportation Research Board of the National Academies (TRB); Venter, C.J. (Christoffel Jacobus)
Paper presented at the 29th Annual Southern African Transport Conference 16 - 19 August 2010 "Walk Together", CSIR International Convention Centre, Pretoria, South Africa.
Modeling captivity and the demand for motorised transport in rural areas of South Africa.
(12th International Conference on Travel Behaviour Research, Jaipur, India., 2009-12) Venkatesh, Anand; christo.venter@up.ac.za; Venter, C.J. (Christoffel Jacobus)
Mobility and access problems in rural areas of developing countries have received some attention from researchers, but this has mostly been of a qualitative nature using small-sample studies. Progressively achieving rural development objectives requires, amongst other things, a better and more quantitative understanding of the nature of the demand for mobility in rural environments, and its links with livelihoods. Rural travel demand differs from urban demand in key respects, including the existence of more restricted choice contexts. Issues of captivity and choice set formation thus need to be dealt with explicitly and carefully. The paper reports on a study undertaken in an isolated rural area within Limpopo Province in South Africa, aimed at exploring and modelling mode choice behaviour in a very constrained situation. The combined use of qualitative participatory approaches with conventional travel diary and stated choice techniques is described as a way of exploring unfamiliar aspects of rural travel behaviour. A mixed logit mode choice model is successfully calibrated, showing that rural travellers exhibit rational compensatory decision making behaviour when faced with real alternatives. However descriptive analysis suggests that, in reality, multiple alternatives are often absent or uncertain, leading to non-compensatory behaviour. This is confirmed by efforts to incorporate “soft” cutoffs to model choice set constraints for this sample.
Evaluation of issues around road materials for sustainable transport
(Document Transformation Technologies, 2009-07-06) Paige-Green, Philip; Southern African Transport Conference (28th : 2009 : Pretoria, South Africa); Steyn, Wynand Jacobus Van der Merwe
Paper presented at the 28th Annual Southern African Transport Conference 6 - 9 July 2009 "Sustainable Transport", CSIR International Convention Centre, Pretoria, South Africa.
Implementation of interactive web-based training tools in pavement engineering
(Document Transformation Technologies, 2009-07-06) Mahoney, J.P.; Muench, S.T.; White, G.T. (Gary); Southern African Transport Conference (28th : 2009 : Pretoria, South Africa); Steyn, Wynand Jacobus Van der Merwe
Paper presented at the 28th Annual Southern African Transport Conference 6 - 9 July 2009 "Sustainable Transport", CSIR International Convention Centre, Pretoria, South Africa.
A relook at residential trip generation variables
(Document Transformation Technologies, 2009-07-06) Peska, P.; Southern African Transport Conference (28th : 2009 : Pretoria, South Africa); Venter, C.J. (Christoffel Jacobus)
Paper presented at the 28th Annual Southern African Transport Conference 6 - 9 July 2009 "Sustainable Transport", CSIR International Convention Centre, Pretoria, South Africa.
Fracture mechanics in pavement design
(Document Transformation Technologies, 2009-07-06) Wu, Rongzong; Southern African Transport Conference (28th : 2009 : Pretoria, South Africa); Denneman, Erik; Kearsley, Elsabe P.; Visser, Alex T.
Paper presented at the 28th Annual Southern African Transport Conference 6 - 9 July 2009 "Sustainable Transport", CSIR International Convention Centre, Pretoria, South Africa.

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