Denis Kalumba | University of Cape Town (original) (raw)

Papers by Denis Kalumba

Geomechanics and geoengineering, Mar 5, 2024

Atlantis highlights in engineering, Dec 31, 2022

CRC Press eBooks, Sep 10, 2023

Scientific African, Aug 1, 2023

Geotechnical Research

Ordinary and reinforced granular columns were both tested in a laboratory to study the effect of ... more Ordinary and reinforced granular columns were both tested in a laboratory to study the effect of internal reinforcement using plastic fibres that were generated through the recycling of post-consumer polyethylene terephthalate bottles. A series of vertical compression tests was undertaken to understand the impact of varying the moisture content of the silt bed and the fibre concentration. The prepared samples were vertically loaded up to a maximum compression of 50 mm, and the load–vertical deformation characteristics were electronically recorded. Post-testing, the deformation behaviour of the column was physically modelled using a paste of plaster of Paris to obtain the maximum bulging diameter. In general, reinforcing the granular columns enhanced the load-carrying capacity, although the degree of improvement was dependent on the testing conditions. For experiments conducted on the softer silt beds, an increase in fibre content resulted in higher loading strengths. The largest enh...

Rock mass damage due to shear tectonic activity has been investigated largely in geoscience where... more Rock mass damage due to shear tectonic activity has been investigated largely in geoscience where fluid transport is of major interest. However, little has been studied on the effect of shear zones on rock mass behavior and its impact on stability of rock slopes. At Letšeng Diamonds open pit mine in Lesotho, the shear zone composed of sheared kimberlite material, calcite and altered basalt is forming part of the haul ramp into the main pit cut 3. The alarming rate at which the shear zone is deteriorating has triggered concerns about both local and global stability of pit the walls. This study presents the numerical modelling of the open pit slope affected by shear zone at Letšeng Diamond Mine (LDM). Analysis of the slope involved development of the slope model by using a two-dimensional finite element code RS2. Interfaces between shear zone and host rock were represented by special joint elements incorporated in the finite element code. The analysis of structural geological mapping ...

Proceedings of the First Southern African Geotechnical Conference, 2016

Proceedings of the International Conference on Ground Improvement & Ground Control, 2012

International Journal of Geosynthetics and Ground Engineering

Landfill liners are critical components of waste containment systems that are designed to prevent... more Landfill liners are critical components of waste containment systems that are designed to prevent the migration of pollutants into the environment. Accurate measurement of the shear strength of soil–geosynthetic and geosynthetic–geosynthetic interfaces is essential for designing safe and cost-effective landfill liners. This paper presents a comparative study of the shear strength parameters of single and multi-layer interfaces using a Large Direct Shear Apparatus (LDSA). The study aimed to investigate the effects of using different testing configurations on the Peak and Large Displacement (LD) strengths of the interfaces and to identify the test configuration that provides the most critical shear strength results. A “305 × 305 mm” LDSA was used to perform interface shear tests in saturated conditions with applied normal stresses ranging from 50 to 400 kPa. The results showed good agreement between strength envelopes derived from single and multi-layer interface tests for the materia...

Civil Engineering Journal

This study is focused on evaluating the factors affecting the performance of fiber-reinforced sub... more This study is focused on evaluating the factors affecting the performance of fiber-reinforced subgrade under cyclic loading. To achieve the objectives of this study, a series of dynamic triaxial (DT) tests was performed, and the following parameters, such as resilient modulus (MR), number of loading cycles (N), cyclic stress (CS), resilient strain (RS), and stress-strain hysteresis response of both the reinforced and unreinforced subgrades were evaluated. Subsequently, a series of scanning electron microscope (SEM) tests was conducted to track the fiber-soil interfacial bonding after the completion of DT test. The results indicated that N and CS triggered an appreciable decrease in MR with significantly high RS deformation for the unreinforced subgrade. However, reversed responses were noted upon the inclusion of sisal fiber due to fiber-soil adhesion and a high ductility response was portrayed by the reinforced subgrades. A reversed response was significant upon 0.25% and 0.5% fibe...

This is a proceeding paper presented at the 9th South African Young Geotechnical Engineers Confer... more This is a proceeding paper presented at the 9th South African Young Geotechnical Engineers Conference, 13, 14 & 15 September 2017 – Salt Rock Hotel, Dolphin Coast, Durban, KwaZulu-Natal 523 on the Use of Crushed Concrete Aggregate Waste in Stabilization of Clayey Soils for Sub Base Pavement Construction.The research aimed at stabilizing lateritic soils, using crushed concrete aggregates from demolished buildings, foundations, roads and other structures, for use as sub-base for a paved road. Lateritic soils were sampled along the Mukono-Jinja Highway from a borrow pit owned by Stirling Company LTD. Crushed concrete aggregate wastes were fairly angular and strong as they showed comparative values to the fresh aggregates as earlier researched. The lateritic soils were blended with different percentages of waste aggregates 0%, 30%, 40% and 50%, chosen basing on previous studies. The study looked at properties such as grading and flakiness of the waste aggregates, grading, atterberg limits, Optimum Moisture Content, Maximum Dry Density and 4 day soaked California Bearing Ratio for the stabilized and un-stabilized material. Mix designs with 40 % and 50 % of the waste aggregates were considered suitable for use as sub base material. They had CBR of 46 and 59, respectively, at 95 % relative compaction and PI values of 13.64 and 11.40. These met the specified standards of a CBR equal or greater than 45 and PI equal or less than 14 according to the general specifications of Ministry of Works, Housing and Communications (2004)

World Academy of Science, Engineering and Technology, International Journal of Environmental, Chemical, Ecological, Geological and Geophysical Engineering, 2017

Rock mass damage due to shear tectonic activity has been investigated largely in geoscience where... more Rock mass damage due to shear tectonic activity has been investigated largely in geoscience where fluid transport is of major interest. However, little has been studied on the effect of shear zones on rock mass behavior and its impact on stability of rock slopes. At Letšeng Diamonds open pit mine in Lesotho, the shear zone composed of sheared kimberlite material, calcite and altered basalt is forming part of the haul ramp into the main pit cut 3. The alarming rate at which the shear zone is deteriorating has triggered concerns about both local and global stability of pit the walls. This study presents the numerical modelling of the open pit slope affected by shear zone at Letšeng Diamond Mine (LDM). Analysis of the slope involved development of the slope model by using a twodimensional finite element code RS2. Interfaces between shear zone and host rock were represented by special joint elements incorporated in the finite element code. The analysis of structural geological mapping d...

13th ISRM International Congress of Rock Mechanics, May 10, 2015

International Journal of Geosynthetics and Ground Engineering

Geosynthetics form an integral part of engineered municipal solid waste (MSW) landfill lining sys... more Geosynthetics form an integral part of engineered municipal solid waste (MSW) landfill lining systems, as they provide cost saving and technical benefits. Their introduction in lining systems, however, has presented new potential interfaces for shear failure especially on bases and on side slopes of engineered MSW landfills. In the laboratory, interface shear strength parameters used in slope designs of landfill lining systems are determined through single-interface testing configurations as per ASTM D5321-20 and D6243-20 standards. However, single-interface testing configurations do not provide a clear understanding of shear strength transfers among the lining components and does not aid in pin-pointing the interface facilitating failure especially when a multi-layered lining system has been proposed. Multi-interface testing configurations present an alternative that may address such limitations. But there is minimum information available on this type of testing as it is not stipul...

This is a proceeding paper presented at 17th African Regional Conference on Soil Mechanics and Ge... more This is a proceeding paper presented at 17th African Regional Conference on Soil Mechanics and Geotechnical Engineering on the effects of expanded polystyrene and cement on properties of sand soils for foundation use.

E3S Web of Conferences

The design of a competent basal lining system is crucial in ensuring a long-lasting and functiona... more The design of a competent basal lining system is crucial in ensuring a long-lasting and functional engineered municipal solid waste (MSW) landfill. However, due to the inclusion of numerous geosynthetics and geomaterials forming a multi-layered lining system, there rises an uncertainty on determining the critical or weakest interface. This is exacerbated by the different properties offered by these lining materials and their inter-crossing functions in landfills. According to ASTM D5321-20 standard, the interface shear strengths used in design of bases and side-slopes of lining systems are determined through a single interface testing configuration. However, minimal research has been done to evaluate the consequences of multi-interface testing configurations on the minimum factors of safety (FoSmin). The present study was thus conducted to further investigate this phenomena while establishing the appropriateness of double interface testing configuration using large direct shear equi...

The first resource, 2011

Millions of tonnes of waste are generated in South Africa. A considerable amount of this is in th... more Millions of tonnes of waste are generated in South Africa. A considerable amount of this is in the form of plastic (polyethylene) shopping bags, most of which are destined for landfill. Can this modern waste and environmental hazard find a new application in civil engineering projects?

Geomechanics and geoengineering, Mar 5, 2024

Atlantis highlights in engineering, Dec 31, 2022

CRC Press eBooks, Sep 10, 2023

Scientific African, Aug 1, 2023

Geotechnical Research

Proceedings of the First Southern African Geotechnical Conference, 2016

Proceedings of the International Conference on Ground Improvement & Ground Control, 2012

International Journal of Geosynthetics and Ground Engineering

Civil Engineering Journal

World Academy of Science, Engineering and Technology, International Journal of Environmental, Chemical, Ecological, Geological and Geophysical Engineering, 2017

Rock mass damage due to shear tectonic activity has been investigated largely in geoscience where... more Rock mass damage due to shear tectonic activity has been investigated largely in geoscience where fluid transport is of major interest. However, little has been studied on the effect of shear zones on rock mass behavior and its impact on stability of rock slopes. At Letšeng Diamonds open pit mine in Lesotho, the shear zone composed of sheared kimberlite material, calcite and altered basalt is forming part of the haul ramp into the main pit cut 3. The alarming rate at which the shear zone is deteriorating has triggered concerns about both local and global stability of pit the walls. This study presents the numerical modelling of the open pit slope affected by shear zone at Letšeng Diamond Mine (LDM). Analysis of the slope involved development of the slope model by using a twodimensional finite element code RS2. Interfaces between shear zone and host rock were represented by special joint elements incorporated in the finite element code. The analysis of structural geological mapping d...

13th ISRM International Congress of Rock Mechanics, May 10, 2015

International Journal of Geosynthetics and Ground Engineering

E3S Web of Conferences

The first resource, 2011

The global initiative of minimizing the generation of waste materials and the reduction in the en... more The global initiative of minimizing the generation of waste materials and the reduction in the environmental footprints of industrial processes has impelled the innovation into their use in geotechnical applications. Use of these materials in this manner, especially as soil reinforcements, could help solve the drudgery and the secondary snags of disposing of the materials. This study therefore aimed at investigating the effects of sugarcane bagasse reinforcement on selected South African soils as well as the drawbacks of the environmental conditions on the composite formed. Different types of sugarcane bagasse were utilised in evaluating their effect on the shear strength characteristics of the composite. The results indicated a higher improvement in the angle of internal friction in finely grained soil compared to coarsely grained soil. Saturation of the composite in water insignificantly reduced the strength characteristics beyond 2 days. In addition, an increase in the shear characteristics depended on the bagasse type and content, and on the vertical load.

Wind energy has been selected an appropriate means of diversifying South Africa's energy mix and ... more Wind energy has been selected an appropriate means of diversifying South Africa's energy mix and improving its electricity capacity in view of growing socioeconomic and environmental pressures. However, this comes with engineering challenges, one being designing efficient foundations for wind turbine structures. This discussion was centred on the sources of loading that wind turbines experience and the consequences of this on the geotechnical design of gravity footings. Rotational stiffness of the foundation was shown to have an important effect on the dynamic response of the wind turbine tower, and thus, on the assumptions surrounding the calculation of the natural frequency of the global system. Means of assessing the rotational and lateral stiffness as well as models investigating soil stiffness inclusion in natural frequency assumptions were evaluated in the context of a South African case study, specific to the South Eastern city of Port Elizabeth. Soils of this region were dominated by weathered silty fine sands and varying degrees of pedogenic calcrete, creating unique challenges in design. Soil stiffness effects on natural frequency assumptions were found to be more critical than the minimum stiffness requirements applied by design guidelines and had a notable effect on dynamic amplification for an undamped system.

Since the 1990's, the mining industry has introduced diverse kinds of Thin Spray-on Liners (TSLs)... more Since the 1990's, the mining industry has introduced diverse kinds of Thin Spray-on Liners (TSLs). The aim has been to replace the conventional methods of surface support like Shotcrete. Since then, TSLs have shown potential as alternative surface support systems with increased benefits. However, their application is largely based on experience, assumptions, field observations and cost considerations. This is due to the fact that mechanisms by which TSLs provide support are not yet fully understood. In this study, Phase2 v.7.0, a numerical analysis program was utilised to compare performance of these thin spray-on liners and Shotcrete in underground tunnel applications. The computer software was used to determine the induced stresses, deformations and developed plastic zone around the tunnel, with different support linings of Shotcrete and TSL, combined with rock bolts. A tunnel 10 m wide and 15 m high was considered. The tunnel was assumed to be through sandstone at a depth of 550 m. The strength of sandstone was represented by the generalised Hoek-Brown failure criterion with the uniaxial compressive strength of the intact rock equal to 50 MPa and the Geological Strength Index (GSI) equal to 50. The other Hoek-Brown parameters were determined using RocLab software. Numerical analysis showed that TSL thickness of 24.2 mm offers the same structural capacity as Shotcrete of 50 mm thickness. This is a significant reduction in material consumption with associated economic benefits.