Papers by Gerald Maregesi
Detailed analysis of 181 Atterberg limits test results collected from literature demonstrates tha... more Detailed analysis of 181 Atterberg limits test results collected from literature demonstrates that shrinkage limit is the plasticity characteristic of soil. The main factor affecting the shrinkage limit is the specific surface area of the clay minerals. As the specific surface area increases, the shrinkage limit decreases. Two models for estimating the shrinkage limit have been developed. The first model is based on the average slope of the fall cone flow curve (20/LL), while the second model uses the liquid limit to estimate the shrinkage limit of the soil. In line with AASHTO T92-88, the reproducibility of the shrinkage limit test results is ±6.8. 95% of the shrinkage limit results computed using the proposed models plotted within the statistical testing bound, indicating the robustness of the proposed model and its potential for estimating the shrinkage limit of the soil.
This paper presents two models that predict the quantity of active clay content within the soil m... more This paper presents two models that predict the quantity of active clay content within the soil matrix. The first model utilizes the ratio of the second to the first norm (distance factor) of the idealized fall cone flow curve. In contrast, the second model is based on the correlation between liquid limit and clay content. These models were developed by analyzing 307 Atterberg limits and clay content test results, a comprehensive data collection from thirteen published literature. The models were validated using 55 test results from four additional published literature. The predicted clay content was within the statistical testing bound of ±12 given in AASHTO T88-10.
The active and inactive clay content are delineated at a clay index of zero. The soil with a posi... more The active and inactive clay content are delineated at a clay index of zero. The soil with a positive clay index is active clay, while the soil with a negative clay index is inactive clay. The soil with a positive clay index (active clay) is correlated to the liquid limit and plasticity index. In contrast, soil with a negative clay index (inactive clay) is not correlated with the liquid limit and plasticity index. This paper presents a model that predicts the clay content based on the correlation between the clay content of the soil with a positive clay index and the average fall cone slope (20/LL). The model was meticulously developed after analyzing 307 Atterberg limits and clay content test results collected from thirteen different literature. The proposed model was found to compute the clay content with an accuracy of 87% (87% of the calculated clay content results were within the statistical testing bound of ±12% given in AASHTO T88-10), ensuring its robustness.
Zenodo (CERN European Organization for Nuclear Research), Aug 11, 2022
Invariably most highways specifications call for placement moisture content of engineered fills a... more Invariably most highways specifications call for placement moisture content of engineered fills and pavement layers geomaterial to be in the range of OMC±2%. Some awarding agencies specify the placement moisture content in terms of percentage of OMC, typically between 75-120% of OMC. These specifications do not consider the moisture sensitivity of some soils, particularly finegrained soils. A slight increase or decrease in moulding/placement moisture content of the geomaterial can result in a significant loss of strength. This paper examines the compaction and strength of eight soils of different geological formations at a moisture content of OMC±2% using CBR to measure the bearing capacity of the soil. Shortcomings of specifications based on an arbitrary placement moisture content specification of OMC ±2% are illustrated.
This paper presents models that estimate the active clay content of the soil based on the correla... more This paper presents models that estimate the active clay content of the soil based on the correlation between the ratio of the second and first norm of the idealized fall cone curve (distance factor) and the arithmetic difference between the plasticity index and the clay content (clay index). The models were developed based on an analysis of 306 test results of clay content and Atterberg limits collected from the literature. The models were found to compute the active clay limit reasonably well, with most of the calculated results falling within the statistical testing bound of ±12 as provided in AASHTO T88-10.
This paper presents an analysis of more than 300 Atterberg limit and clay content test results co... more This paper presents an analysis of more than 300 Atterberg limit and clay content test results collected from the literature. The correlation between the Atterberg limits and active clay is discussed. Simple models of computing active clay content are presented. The proposed models were found to estimate the active clay content within the statistical testing bound of ±12 given in AASHTO T88-10.
A model of computing the plasticity index of inorganic soil using the ratio of the second norm (E... more A model of computing the plasticity index of inorganic soil using the ratio of the second norm (Euclidian norm) to the first norm (Manhattan distance) of the idealized fall cone flow curve is proposed. The model was developed using 204 controlled Atterberg limit test results of inorganic soils and validated using 74 Atterberg limit test results collected from the literature. The model computes the plasticity index of the inorganic soils within the statistical testing bound of ±8.
Zenodo (CERN European Organization for Nuclear Research), May 10, 2023
This paper presents two simple equations that can be used to compute the plasticity index of soil... more This paper presents two simple equations that can be used to compute the plasticity index of soil using the correlation between the slope of the British fall cone flow curve and the plasticity index. The models were developed using British fall cone test results using soils of widely varying plasticity, including commercial bentonite.
Zenodo (CERN European Organization for Nuclear Research), May 9, 2022
This paper presents a mathematical model that uses a British cone to predict the soil moisturepen... more This paper presents a mathematical model that uses a British cone to predict the soil moisturepenetration relationship. This relationship is nonlinear for non-bentonite bearing soil and can be modelled using a sigmoidal mathematical function. The developed mathematical model gives a unique opportunity for computing and predicting the fall cone penetration of the soil even at a very low moisture content, at which, due to practical limitations, it is impossible to determine the soil penetration. The mathematical model was found to fit the moisture-penetration data reasonably well. Based on the data presented in this paper, both the liquid limit and plastic limit can be determined from the extended liquid limit flow curve by determining the plastic limit at a 1.2 mm penetration value. The computed plastic limit at a 1.2 mm penetration value was found to be in close agreement with the measured plastic limit.
Zenodo (CERN European Organization for Nuclear Research), May 4, 2023
The Udzungwa escarpment is located in Iringa region, extending its boundary to Morogoro region (T... more The Udzungwa escarpment is located in Iringa region, extending its boundary to Morogoro region (Tanzania). The fine and coarse aggregates produced from the rocks available within these scarps contains an abundant amount of mica. The pit-run sand which is formed from mechanical and chemical disintegration of the parent rocks available within these scarps are equally contaminated with mica. Depending upon some geological formation, the mica content [biotite, muscovite] of Udzungwa scarp aggregates is invariably high. In this paper, the effect of mica on compressive strength and on the water demand of the concrete made using fine aggregates from these scarps is presented. From the laboratory test results, it was established that the presence of mica in fine aggregates causes a reduction of the compressive strength in the range of 8-23% while the water demand of the concrete was found to increase in the range of 8-16% [17-33 l/m 3 ].
Zenodo (CERN European Organization for Nuclear Research), May 10, 2023
In many cases, the liquid limit of the soil can be determined using the fall cone method, yet the... more In many cases, the liquid limit of the soil can be determined using the fall cone method, yet the soil is reported as non-plastic. This study suggests that if the liquid limit of the soil can be determined using the fall cone method, then soil possesses some plasticity which cannot be quantified using a conventional method of thread rolling. In this paper, the plasticity index of the alleged non-plastic soil is computed using a mathematical model.
Zenodo (CERN European Organization for Nuclear Research), Feb 7, 2023
Using a mathematical model which predicts the moisture-penetration relationship up to zero moistu... more Using a mathematical model which predicts the moisture-penetration relationship up to zero moisture content, a model which computes the plastic limit based on the penetration value at the plastic limit is proposed. The model was developed using 194 Atterberg limit test results and validated using 44 soil data collected from the literature. Calculated and determined plastic limits agreed within the narrow range of PL±3, with 92% of the results within the accuracy of PL±1. The calculated plastic limit using the proposed model was found to be within the statistical testing bound of PL±PL*18% provided in AASHTO T90-94.
Zenodo (CERN European Organization for Nuclear Research), Sep 7, 2022
This paper presents a model that uses a slope British cone flow curve or plasticity index of soil... more This paper presents a model that uses a slope British cone flow curve or plasticity index of soil to compute the shrinkage limit of the soil. The model was developed based on the analysis of 186 Atterberg limits test results collected from the literature. It has been demonstrated that all Atterberg limits, namely liquid limit, plastic limit, and shrinkage limit, can be determined using a British fall cone in a single testing operation.
Zenodo (CERN European Organization for Nuclear Research), May 11, 2023
Determining the shrinkage limit using the mercury or wax method is time-consuming and error-prone... more Determining the shrinkage limit using the mercury or wax method is time-consuming and error-prone. This paper presents a model that uses a British cone flow index to compute the shrinkage limit of the soil. The model was developed based on the analysis of 186 Atterberg limits test results from the literature leading to the formulation of an equation for computing the shrinkage limit of the soil using the British fall cone flow index.
Zenodo (CERN European Organization for Nuclear Research), May 6, 2023
Zenodo (CERN European Organization for Nuclear Research), May 18, 2023
This paper summarizes the binder and wearing course mix design test results used during the secti... more This paper summarizes the binder and wearing course mix design test results used during the sectional rehabilitation of the Tanzam highway in Tanzania. The mix design was carried out using the Marshall mix design procedures whereby the Marshall specimens were compacted to refusal using 500 Marshall blows. The optimum binder content was selected as the binder content, which gave 3% air voids at 500 blows-0.4%. The rehabilitated pavement section has been heavily trafficked, with estimated traffic loading of 6 million equivalent standard axles traversing the pavement within three years with no noticeable rutting. Therefore, the Marshall mix design method can be used to design asphalt concrete for heavily loaded pavement if the binder content is correctly selected to limit the effect of postconstruction densification.
This paper presents a mathematical model which defines the moisture-penetration relationship usin... more This paper presents a mathematical model which defines the moisture-penetration relationship using British cone. The developed mathematical model gives a unique opportunity of computing or predicting the cone penetration of the soil even at a very low moisture content at which, due to practical limitation it is impossible to determine the soil penetration. The model was found to fit the moisture-penetration data reasonably well. The model was used to compute the penetration of soil at the plastic limit of 394 soils. This study indicates that the plastic limit cannot be defined using one unique penetration value.
This paper presents a cost-effective method of improving the quality of marginal geo-materials th... more This paper presents a cost-effective method of improving the quality of marginal geo-materials through mechanical stabilisation. Two case study of the mechanical stabilisation as used during the construction of two projects in Tanzania, namely Mwika – Kilacha and Songea-Namtumbo, is presented. In both cases, substantial savings to the contract were realised. In this paper, the geotechnical and geo-mechanical properties of the geo-materials from these two cited projects before mechanical modification and after mechanical modification are presented and discussed. From the laboratory results as well as field test results, it can be concluded that mechanical stabilisation is the simplest method of stabilisation yet cost-effective means of improving the geotechnical and geo-mechanical properties of the marginal geo-materials.
This paper presents the unusual engineering properties of coralline aggregates used for asphalt b... more This paper presents the unusual engineering properties of coralline aggregates used for asphalt binder course production during the rehabilitation of Zanzibar airport (Tanzania). The geotechnical and geomechanical properties of the coralline aggregates, asphalt concrete mix design and the volumetric parameters achieved during mix design are discussed. Asphalt concrete production and the placing procedures are also discussed. Finally, the paper recommends the measures to be taken when using coralline aggregates for asphalt concrete production.
This paper presents and discusses the unusual poor engineering properties of coral limestone from... more This paper presents and discusses the unusual poor engineering properties of coral limestone from Mpiji Borrow area in Bagamoyo District-Tanzania used as subbase materials during the construction of Wazo Hill-Bagamoyo Road. The discussion is based on the study and assessment of road subbase made of coral limestone at the project site in the coast of Dar Es Salaam and Coastal region, which involved about 148,000 square metres of pavement from chainage 28+900 to 42+800. The road length is 42.8 Kilometres starting at Wazo Hill Junction (Chainage 0+000) ending at Bagamoyo town (Chainage 42+800). The deterioration and damage of pavement started while the road construction was ongoing. The pavement failure warranted an immediate forensic investigation to establish the probable cause of the pavement failure. The geoforensic investigation established that the primary cause of pavement failure was due to softening and swelling of coralline subbase caused by the imbibition of water supplied to the subbase layer during crushed base placing and compaction using 'slushing' compaction procedures.
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Papers by Gerald Maregesi