Pub Date : 2021-12-31DOI: 10.17159/2309-8775/2021/v63n4a5
M. S. Smit, E. Kearsley
Ultra-Thin Continuously Reinforced Concrete Pavement (UTCRCP) consists of a 50 mm thin High-Strength Steel-Fibre-Reinforced Concrete (HS-SFRC) overlay placed on existing pavements as rehabilitation or used as part of new pavements. Difficulties have been experienced with the construction of UTCRCP. Additionally, the thin HS-SFRC has superior fatigue properties, but poor load-spreading ability compared to conventional concrete pavements due to its reduced thickness. This results in high deflections when the pavement is loaded. The substructure of UTCRCP plays an important role in its performance. Cement-stabilised granular materials can be used to ensure gradual load spreading with depth, but its behaviour under flexible concrete layers is not yet well understood. In this study the effect of increasing the HS-SFRC layer thickness and the effect of incorporating cement-stabilised base layers were investigated using linear elastic finite element modelling. From stress levels calculated, it was found that C1 and C2 materials perform well underneath a 50 mm HS-SFRC layer subjected to standard axle loads of 80 kN, while C3 and C4 would deteriorate faster. Stabilised layers placed below a thin, flexible concrete layer may however crack, resulting in increased damage to supporting layers. It is recommended that the response of UTCRCP should be investigated using advanced material models for the cement-stabilised base and other substructure layers.
超薄连续钢筋混凝土路面(UTCRCP)由50毫米薄的高强度钢纤维增强混凝土(HS-SFRC)覆盖层组成，覆盖在现有路面上，作为修复或作为新路面的一部分。UTCRCP的建设经历了困难。此外，薄HS-SFRC具有优异的疲劳性能，但由于其厚度减小，与传统混凝土路面相比，其荷载扩散能力较差。这导致在路面加载时的高挠度。UTCRCP的子结构对其性能起着重要的作用。水泥稳定的颗粒材料可用于确保载荷随深度逐渐扩散，但其在柔性混凝土层下的行为尚未得到很好的理解。在本研究中，采用线弹性有限元模型研究了增加HS-SFRC层厚度的效果和加入水泥稳定基层的效果。从计算的应力水平来看，C1和C2材料在50 mm HS-SFRC层下承受80 kN的标准轴载时表现良好，而C3和C4材料的劣化速度更快。然而，将稳定层放置在薄而柔韧的混凝土层下面可能会出现裂缝，从而增加对支撑层的破坏。建议使用水泥稳定基层和其他子结构层的先进材料模型来研究UTCRCP的响应。
{"title":"Load spreading in ultra-thin high-strength steel-fibre-reinforced concrete pavements","authors":"M. S. Smit, E. Kearsley","doi":"10.17159/2309-8775/2021/v63n4a5","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n4a5","url":null,"abstract":"Ultra-Thin Continuously Reinforced Concrete Pavement (UTCRCP) consists of a 50 mm thin High-Strength Steel-Fibre-Reinforced Concrete (HS-SFRC) overlay placed on existing pavements as rehabilitation or used as part of new pavements. Difficulties have been experienced with the construction of UTCRCP. Additionally, the thin HS-SFRC has superior fatigue properties, but poor load-spreading ability compared to conventional concrete pavements due to its reduced thickness. This results in high deflections when the pavement is loaded. The substructure of UTCRCP plays an important role in its performance. Cement-stabilised granular materials can be used to ensure gradual load spreading with depth, but its behaviour under flexible concrete layers is not yet well understood. In this study the effect of increasing the HS-SFRC layer thickness and the effect of incorporating cement-stabilised base layers were investigated using linear elastic finite element modelling. From stress levels calculated, it was found that C1 and C2 materials perform well underneath a 50 mm HS-SFRC layer subjected to standard axle loads of 80 kN, while C3 and C4 would deteriorate faster. Stabilised layers placed below a thin, flexible concrete layer may however crack, resulting in increased damage to supporting layers. It is recommended that the response of UTCRCP should be investigated using advanced material models for the cement-stabilised base and other substructure layers.","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48416144","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-12-31DOI: 10.17159/2309-8775/2021/v63n4a1
C. S. James
Reducing uncertainty in flow resistance estimation in natural channels requires elucidation of contributing influences. Surface shear and form drag are the major contributors in channels containing large roughness elements under emergent flow conditions. The two effects can be accounted for in the Darcy-Weisbach and Manning equations by adding their associated, separate friction factors or taking the square root of the sum of the squares of the corresponding Manning coefficients. The friction factor for form drag can be estimated from the drag coefficient and areal density of the roughness elements and the flow depth. Predictions of the combined effect are tested against results of laboratory experiments with different arrangements of emergent cylinders on smooth and rough beds, using experimentally determined drag coefficients for the cylinders. The variation of the overall resistance coefficient with flow condition depends on the dominant influence, decreasing with flow depth when surface shear dominates, and increasing with depth when form drag dominates.
{"title":"Flow resistance in channels with large emergent roughness elements","authors":"C. S. James","doi":"10.17159/2309-8775/2021/v63n4a1","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n4a1","url":null,"abstract":"Reducing uncertainty in flow resistance estimation in natural channels requires elucidation of contributing influences. Surface shear and form drag are the major contributors in channels containing large roughness elements under emergent flow conditions. The two effects can be accounted for in the Darcy-Weisbach and Manning equations by adding their associated, separate friction factors or taking the square root of the sum of the squares of the corresponding Manning coefficients. The friction factor for form drag can be estimated from the drag coefficient and areal density of the roughness elements and the flow depth. Predictions of the combined effect are tested against results of laboratory experiments with different arrangements of emergent cylinders on smooth and rough beds, using experimentally determined drag coefficients for the cylinders. The variation of the overall resistance coefficient with flow condition depends on the dominant influence, decreasing with flow depth when surface shear dominates, and increasing with depth when form drag dominates.","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-12-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42032697","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-11DOI: 10.17159/2309-8775/2021/v63n3a1
M. De Beer, Y. Van Rensburg, J. Maina
The main aim of this paper is to quantify the three-dimensional contact stresses imposed by a single slow-moving (or rolling) slick solid rubber tyre on a relatively rough contact surface, such as stiff asphalt concrete or airport concrete surfacing layers. The results indicated the tyre-contact patch of a slick solid rubber tyre to be of rectangular shape for a vertical tyre loading range between 20 kN and 100 kN. The rectangular tyre contact shape was confirmed with static paper prints, as well as an electronically measured contact patch with the stress-in-motion pad device. The study included load calibration using a mass load scale, and a stress-in-motion device. These were used with an existing full-scale accelerated pavement test device, referred to as the heavy vehicle simulator. In addition, simplistic multi-layer linear elastic modelling was used to quantify differences between stress and strain responses of two types of two relatively 'stiff' based pavements, such as an asphalt concrete base and Portland cement concrete base, on similar subbase and subgrade layers. Notable differences were obtained, which could potentially influence further detailed studies on the performance of full-scale slick solid rubber tyres on typical multi-layered pavements.
{"title":"Three-dimensional contact stresses of a slick solid rubber tyre on a rigid surface","authors":"M. De Beer, Y. Van Rensburg, J. Maina","doi":"10.17159/2309-8775/2021/v63n3a1","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n3a1","url":null,"abstract":"The main aim of this paper is to quantify the three-dimensional contact stresses imposed by a single slow-moving (or rolling) slick solid rubber tyre on a relatively rough contact surface, such as stiff asphalt concrete or airport concrete surfacing layers. The results indicated the tyre-contact patch of a slick solid rubber tyre to be of rectangular shape for a vertical tyre loading range between 20 kN and 100 kN. The rectangular tyre contact shape was confirmed with static paper prints, as well as an electronically measured contact patch with the stress-in-motion pad device. The study included load calibration using a mass load scale, and a stress-in-motion device. These were used with an existing full-scale accelerated pavement test device, referred to as the heavy vehicle simulator. In addition, simplistic multi-layer linear elastic modelling was used to quantify differences between stress and strain responses of two types of two relatively 'stiff' based pavements, such as an asphalt concrete base and Portland cement concrete base, on similar subbase and subgrade layers. Notable differences were obtained, which could potentially influence further detailed studies on the performance of full-scale slick solid rubber tyres on typical multi-layered pavements.","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48929127","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-11DOI: 10.17159/2309-8775/2021/v63n3a5
K. A. Johnson, J. Smithers, R. Schulze
Frequency analysis of extreme rainfall and flood events are used to determine design rainfalls and design floods which are needed to design hydraulic structures such as dams, spillways and culverts. Standard methods for frequency analysis of extreme events are based on the assumption of a stationary climate. However, this assumption in rainfall and flood frequency analysis is being challenged with growing evidence of climate change. As a consequence of a changing climate, the frequency and magnitude of extreme rainfall events are reported to have increased in parts of South Africa, and these and other changes in extreme rainfall occurrences are expected to continue into the future. The possible non-stationarity in climate resulting in changes in rainfall may impact on the accuracy of the estimation of extreme rainfall quantities and design rainfall estimations. This may have significant consequences for the design of new hydraulic infrastructure, as well as for the rehabilitation of existing infrastructure. Hence, methods that account for non-stationary data, such as caused by climate change, need to be developed. This may be achieved by using data from downscaled global circulation models in order to identify non-stationary climate variables which affect rainfall, and which can then be incorporated into extreme value analysis of a non-stationary data series.
{"title":"A review of methods to account for impacts of non-stationary climate data on extreme rainfalls for design rainfall estimation in South Africa","authors":"K. A. Johnson, J. Smithers, R. Schulze","doi":"10.17159/2309-8775/2021/v63n3a5","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n3a5","url":null,"abstract":"Frequency analysis of extreme rainfall and flood events are used to determine design rainfalls and design floods which are needed to design hydraulic structures such as dams, spillways and culverts. Standard methods for frequency analysis of extreme events are based on the assumption of a stationary climate. However, this assumption in rainfall and flood frequency analysis is being challenged with growing evidence of climate change. As a consequence of a changing climate, the frequency and magnitude of extreme rainfall events are reported to have increased in parts of South Africa, and these and other changes in extreme rainfall occurrences are expected to continue into the future. The possible non-stationarity in climate resulting in changes in rainfall may impact on the accuracy of the estimation of extreme rainfall quantities and design rainfall estimations. This may have significant consequences for the design of new hydraulic infrastructure, as well as for the rehabilitation of existing infrastructure. Hence, methods that account for non-stationary data, such as caused by climate change, need to be developed. This may be achieved by using data from downscaled global circulation models in order to identify non-stationary climate variables which affect rainfall, and which can then be incorporated into extreme value analysis of a non-stationary data series.","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41321566","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-11DOI: 10.17159/2309-8775/2021/v63n3a3
N. Ngobeni, A. Marnewick, D. J. van Vuuren
This research proposes a parametric design process model to improve the structural engineering project team performance by automating the design and three-dimensional modelling procedures of box culverts. Although standardised design procedures can reduce the design time of repetitive structures such as box culverts, the increased time and effort required for revising construction drawings negatively impacts a project's performance. A literature review was conducted to develop a theoretical process model to improve the current structural design optimisation and three-dimensional modelling procedures of box culverts. The proposed process model was validated using structured interviews with professionally registered structural engineers for appropriateness to box culverts and the potential to improve project performance. The data analysis revealed that the interviewed engineers were in favour of automating the design optimisation and three-dimensional modelling procedures of box culverts. Moreover, parametric design automation would result in improved project performance when encountering an inevitable design change. However, the user's control over the output of each process should not be discarded. This study can help readers understand the transformation of the structural design and three-dimensional modelling procedures of repetitive structures, such as box culverts, into an algorithmic form to achieve improved project performance.
{"title":"A parametric design process model for box culverts","authors":"N. Ngobeni, A. Marnewick, D. J. van Vuuren","doi":"10.17159/2309-8775/2021/v63n3a3","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n3a3","url":null,"abstract":"This research proposes a parametric design process model to improve the structural engineering project team performance by automating the design and three-dimensional modelling procedures of box culverts. Although standardised design procedures can reduce the design time of repetitive structures such as box culverts, the increased time and effort required for revising construction drawings negatively impacts a project's performance. A literature review was conducted to develop a theoretical process model to improve the current structural design optimisation and three-dimensional modelling procedures of box culverts. The proposed process model was validated using structured interviews with professionally registered structural engineers for appropriateness to box culverts and the potential to improve project performance. The data analysis revealed that the interviewed engineers were in favour of automating the design optimisation and three-dimensional modelling procedures of box culverts. Moreover, parametric design automation would result in improved project performance when encountering an inevitable design change. However, the user's control over the output of each process should not be discarded. This study can help readers understand the transformation of the structural design and three-dimensional modelling procedures of repetitive structures, such as box culverts, into an algorithmic form to achieve improved project performance.","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49462158","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-11DOI: 10.17159/2309-8775/2021/v63n3a4
J. A. Du Plessis, J. K. Kibii
Long-term rainfall data with good spatial and temporal distribution is essential for all climate-related analyses. The availability of observed rainfall data has become increasingly problematic over the years due to a limited and deteriorating rainfall station network, occasioned by limited reporting and/or quality control of rainfall and, in some cases, closure of these stations. Remotely sensed satellite-based rainfall data sets offer an alternative source of information. In this study, daily and monthly rainfall data derived from Climate Hazards Group InfraRed Precipitation (CHIRPS) is compared with observed rainfall data from 46 stations evenly distributed across South Africa. Various metrics, based on a pairwise comparison between the observed and CHIRPS data, were applied to evaluate CHIRPS performance in the estimation of daily and monthly rainfall. The results show that CHIRPS data correlate well with observed monthly rainfall data for all stations used, having an average coefficient of determination of 0.6 and bias of 0.95. This study concludes that monthly CHIRPS data corresponds well, with good precision and relatively little bias when compared to observed monthly rainfall data, and can therefore be considered for use in conjunction with observed rainfall data where no or limited data is available in South Africa for hydrological analysis.
{"title":"Applicability of CHIRPS-based satellite rainfall estimates for South Africa","authors":"J. A. Du Plessis, J. K. Kibii","doi":"10.17159/2309-8775/2021/v63n3a4","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n3a4","url":null,"abstract":"Long-term rainfall data with good spatial and temporal distribution is essential for all climate-related analyses. The availability of observed rainfall data has become increasingly problematic over the years due to a limited and deteriorating rainfall station network, occasioned by limited reporting and/or quality control of rainfall and, in some cases, closure of these stations. Remotely sensed satellite-based rainfall data sets offer an alternative source of information. In this study, daily and monthly rainfall data derived from Climate Hazards Group InfraRed Precipitation (CHIRPS) is compared with observed rainfall data from 46 stations evenly distributed across South Africa. Various metrics, based on a pairwise comparison between the observed and CHIRPS data, were applied to evaluate CHIRPS performance in the estimation of daily and monthly rainfall. The results show that CHIRPS data correlate well with observed monthly rainfall data for all stations used, having an average coefficient of determination of 0.6 and bias of 0.95. This study concludes that monthly CHIRPS data corresponds well, with good precision and relatively little bias when compared to observed monthly rainfall data, and can therefore be considered for use in conjunction with observed rainfall data where no or limited data is available in South Africa for hydrological analysis.","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43275432","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-11-11DOI: 10.17159/2309-8775/2021/v63n3a6
E. Sanadgol, M. Heidarpour, R. Mohammadpour
This study investigated the effectiveness of bed sills in reducing the scour depth with time at rectangular piers in a laboratory. Experiments were conducted just below the threshold of sediment motion (U/Uc = 0.95) for round-nosed piers with the length-to-width ratios of L/b = 1, 2, 3 and 4. Accordingly, a 1 cm thick PVC section as wide as the channel was used as the bed sill, which was flush with the bed and located at various distances, D, in the downstream of the piers, i.e. D/b = 0, 1, 2 and 3. It was found that the efficiency of the bed sill for a rectangular pier was significantly less than that for the circular one; there was a decrease in efficiency and scour depth with an increase of the pier length. The maximum efficiency obtained for the round-nosed piers with L/b = 1, 2, 3 and 4 was 32.5%, 21.3%, 14.4% and 5.7%, respectively. The application of a bed sill to reduce the local scour in round-nosed rectangular piers, when the length-to-width ratio exceeds 2, is therefore not recommended. Furthermore, the efficiency of the bed sill is the best when it is attached to the downstream end of the pier; its efficiency is decreased when increasing its distance from the pier.
{"title":"Reduction of local scouring at round-nosed rectangular piers using a downstream bed sill","authors":"E. Sanadgol, M. Heidarpour, R. Mohammadpour","doi":"10.17159/2309-8775/2021/v63n3a6","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n3a6","url":null,"abstract":"This study investigated the effectiveness of bed sills in reducing the scour depth with time at rectangular piers in a laboratory. Experiments were conducted just below the threshold of sediment motion (U/Uc = 0.95) for round-nosed piers with the length-to-width ratios of L/b = 1, 2, 3 and 4. Accordingly, a 1 cm thick PVC section as wide as the channel was used as the bed sill, which was flush with the bed and located at various distances, D, in the downstream of the piers, i.e. D/b = 0, 1, 2 and 3. It was found that the efficiency of the bed sill for a rectangular pier was significantly less than that for the circular one; there was a decrease in efficiency and scour depth with an increase of the pier length. The maximum efficiency obtained for the round-nosed piers with L/b = 1, 2, 3 and 4 was 32.5%, 21.3%, 14.4% and 5.7%, respectively. The application of a bed sill to reduce the local scour in round-nosed rectangular piers, when the length-to-width ratio exceeds 2, is therefore not recommended. Furthermore, the efficiency of the bed sill is the best when it is attached to the downstream end of the pier; its efficiency is decreased when increasing its distance from the pier.","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-11-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44461774","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.17159/2309-8775/2021/v63n2a3
I. Luker
ABSTRACT Laboratory measurements were done of the end-bearing and side-shear stresses on small piles subjected to "static" and rapid load tests. Interpretation, by the unloading-point method, of the results of rapid tests were done to estimate what the behaviour under a static test would have been if it had been done instead. Comparisons were made of the estimated static test behaviour to the actual static test behaviour to determine empirical values of a factor to adjust estimates closer to actual static test results. The dependence of the empirical factor on soil type, the liquid limit of plastic soils and water content is shown. Keywords: piles, load test, clays, dynamics, empiricism
{"title":"Static pile capacity from the rapid test via the unloading-point method","authors":"I. Luker","doi":"10.17159/2309-8775/2021/v63n2a3","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n2a3","url":null,"abstract":"ABSTRACT Laboratory measurements were done of the end-bearing and side-shear stresses on small piles subjected to \"static\" and rapid load tests. Interpretation, by the unloading-point method, of the results of rapid tests were done to estimate what the behaviour under a static test would have been if it had been done instead. Comparisons were made of the estimated static test behaviour to the actual static test behaviour to determine empirical values of a factor to adjust estimates closer to actual static test results. The dependence of the empirical factor on soil type, the liquid limit of plastic soils and water content is shown. Keywords: piles, load test, clays, dynamics, empiricism","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49195345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.17159/2309-8775/2021/v63n2a6
F. Haupt, F. Netterberg
ABSTRACT A preliminary statistical analysis of 914 mostly Transvaal soils of average selected subgrade quality produced useful, highly statistically significant methods for the prediction of the maximum Proctor CBR and the Proctor compaction characteristics, as well as relationships between soaked and unsoaked CBR and between Proctor and MAASHO compaction characteristics. Because of the well-known poor reproducibilty of the CBR, as well as the indicator tests used, it is believed that the accuracy of the prediction methods is better than it appears from the large scatter of results. These methods do not replace CBR testing but supplement it by possibly reducing the number of expensive tests and providing a check on gross errors. Keywords: CBR, prediction, indicator tests, subgrade, Proctor
{"title":"Prediction of California Bearing Ratio and compaction characteristics of Transvaal soils from indicator properties","authors":"F. Haupt, F. Netterberg","doi":"10.17159/2309-8775/2021/v63n2a6","DOIUrl":"https://doi.org/10.17159/2309-8775/2021/v63n2a6","url":null,"abstract":"ABSTRACT A preliminary statistical analysis of 914 mostly Transvaal soils of average selected subgrade quality produced useful, highly statistically significant methods for the prediction of the maximum Proctor CBR and the Proctor compaction characteristics, as well as relationships between soaked and unsoaked CBR and between Proctor and MAASHO compaction characteristics. Because of the well-known poor reproducibilty of the CBR, as well as the indicator tests used, it is believed that the accuracy of the prediction methods is better than it appears from the large scatter of results. These methods do not replace CBR testing but supplement it by possibly reducing the number of expensive tests and providing a check on gross errors. Keywords: CBR, prediction, indicator tests, subgrade, Proctor","PeriodicalId":54762,"journal":{"name":"Journal of the South African Institution of Civil Engineering","volume":" ","pages":""},"PeriodicalIF":0.4,"publicationDate":"2021-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49665632","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":4,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2021-06-01DOI: 10.17159/2309-8775/2021/v63n2a5
F. C. Rust, K. Wall, M. Smit, S. Amod
ABSTRACT The South African Institution of Civil Engineering (SAICE) Infrastructure Report Cards of 2006, 2011 and 2017 reported that much of the South African infrastructure is in a poor condition. To augment the recent 2017 Report Card, a survey was, for the first time, conducted amongst SAICE members to obtain their opinion on the condition of infrastructure (in terms of a grading), the trend of the condition over time, as well as the reasons for the individual's grading. The 669 respondents indicated that, apart from a few exceptions such as national airports and the Gautrain, much of the infrastructure is in a poor state, which is very similar to the results obtained from the SAICE Report Card process. The results were also analysed per province and indicated that, in the opinion of respondents, specific provinces in particular are struggling with poor infrastructure. The main reasons given for the poor infrastructure were a lack of maintenance, lack of institutional capability, lack of sufficient funding and over-loading of infrastructure. Keywords: infrastructure condition, SAICE Infrastructure Report Card, Infrastructure grading system
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