Browsing by Author "Kalumba, D."

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Designing a Paved Road Using Geogrids to Reduce the Thickness of the Pavement Layers
(9th South African Young Geotechnical Engineers Conference, 2017) Melling, H. C.; Tusabe, K. S.; Jjuuko, S.; Kalumba, D.
Performance and durability of road pavements are significantly dependent on the strength and stability of the underlying soil layers, most especially the subgrade pavement layer. Currently, in Uganda most roads are constructed through low lying areas characterized by soft, hence weak, clay soils. The main practice, of improving the strength of such subgrade layers, has been to import stronger lateritic soils and dump them in layers over the weaker soils in thicknesses of more than 1.0 m. This is expensive, especially in terms of the haulage costs, and not environmentally friendly. Additionally, the lateritic soils are also getting depleted. Hence the need to utilize alternative means of increasing the strength of weak subgrades. This study focused on the application of Geogrids in pavement layers to reduce their overall thickness and life cycle costs of the road. A low-lying section on the Bajjo road, a bypass connecting Mukono to Seeta, was used as a case study. According to the AASHTO classification system of subgrade materials, the subgrade soils fell under the soil ranges of A-7, A-7-6, and A-6 group, therefore a poor subgrade material requiring stabilization. The average CBR was determined as 19%. The inclusion of the Geogrid reduced the overall layer works thickness by 25% and it’s cost effective by 42% over the whole lifecycle of the road.
The Effect of expanded polystyrene and cement on properties of sand soils for foundation use
(17th African Regional Conference on Soil Mechanics and Geotechnical Engineering, 2019-10) Mugera, P.; Magyezi, S.; Jjuuko, S.; Kalumba, D.
The increase in Expanded Polystyrene (EPS) waste in Uganda is prone to cause serious environmental pollution owing to the related poor disposal methods. The common practices include open disposal and/or burning which are both environmentally degrading. Other approaches of recycling EPS are unpopular and quite expensive. This research aimed to investigate the effect of EPS and cement on sand soil for a foundation material. The soil was a poorly graded sand. Preliminary tests were carried out to determine the grading, Optimum Moisture Content (OMC) and Maximum Dry Density (MDD) of the sand. Initial cement consumption test was done to determine a constant weight of cement required for just the binding effect on the materials. The unconfined compressive strength, shear box, permeability and consolidation tests were performed on the treated soil specimens at various percentages of EPS. The sand-EPS-cement composite showed an increase in unconfined compressive strength and shear strength with the maximum at 0.5% EPS. The permeability of the composite decreased while there was a minimal increase in settlement with increasing EPS content.
Use of Crushed Concrete Aggregate Waste in Stabilization of Clayey Soils for Sub Base Pavement Construction
(9th South African Young Geotechnical Engineers Conference, 13, 14 & 15 September 2017, 2017) Kashoborozi, O.; Aturinda, E.; Jjuuko, S.; Kalumba, D.
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).
Use of Lime Piles as an Alternative Method for Stabilisation of Road Embankments
(9th South African Young Geotechnical Engineers Conference, 2017) Nakyeyune, J. R.; Bamwesigye, S.; Jjuuko, S.; Kalumba, D.
The durability and performance of an embankment depends on its stability. Several options are available for controlling stability and settlement problems associated with embankment slopes. One of them involves using stabilising agents which are suitable for the existing embankment. This research focused on improving the engineering properties of clay soil insitu by using lime pile technique. The clay soil was obtained from a failed embankment along Kamwenge – Fort portal road, chainage 18 + 900. Preliminary tests were carried out to determine if the soil required stabilisation. It had a high liquid limit of 58.6%, plastic limit 26.5% and plasticity index of 32.1. It was classified as CH using the Unified Soil Classification System. Various tests were carried out, for curing days of 14, 21 and 28, to investigate the effect on the engineering properties of the soil. Results showed an increase in Maximum Dry Density, shear strength and a decrease in Optimum Moisture Content and plasticity index hence improved soil properties for embankment slope stability.