Impact of agricultural waste additive on 1-dimensional clay consolidation behaviour
- Agbenyeku, Emem-Obong Emmanuel, Muzenda, Edison, Msibi, Innocent Mandla
- Authors: Agbenyeku, Emem-Obong Emmanuel , Muzenda, Edison , Msibi, Innocent Mandla
- Date: 2014
- Subjects: Rice husk ash , Kaolinitic clay , Soil treatment , Soil consolidation , Soil stabilization , Agricultural waste , Landfills , Fills (Earthwork)
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/386034 , uj:5050 , http://hdl.handle.net/10210/13589
- Description: Soil treatment is of vital concern in geoenvironmental and construction engineering in present times as suitable naturally occurring materials are rapidly depleted. Efforts are continually invested towards the resourceful utilization of wastes as fillers, cement enhancers, stabilizers and blenders with little or no significant impacts on the environment. This paper explains the use of a locally available and abundant agricultural waste- Rice husk ash (RHA) in West Africa, Nigeria for the treatment and stabilization of kaolinitic clay (KC) sampled from an active landfill site in Johannesburg, South Africa. The impact of incorporating different percentages of RHA on the compressibility characteristics of a parent compressible landfill KC sample was investigated under a One-dimensional consolidation test. Compacted soil specimens were treated at optimum water content (OWC) and maximum dry unit weight (MDUW) by the addition of agricultural waste material to the parent KC. The compacted specimens were subjected incremental vertical loading in a fixed ring consolidometer device. This was done with a view to closely simulate the waste loading effects from a typical landfill on a treated and parent clay/clayey bottom barrier based on one-dimensional consolidation behaviours. The introduction of RHA waste material to the parent KC revealed an outcome with substantial improvements in compaction characteristics. Hence, the results presented herein showed the agricultural waste to positively increase one-dimensional rigidity while settlement was effectively decreased. From results and analysis, the KC stabilized with RHA can withstand loadings from waste heaps under conditions as were applied in this study. With due recommended examination by geoenvironmental specialists, the stabilized material may be considered as an environmental and cost saving beneficiation approach for use in landfill liners.
- Full Text:
- Authors: Agbenyeku, Emem-Obong Emmanuel , Muzenda, Edison , Msibi, Innocent Mandla
- Date: 2014
- Subjects: Rice husk ash , Kaolinitic clay , Soil treatment , Soil consolidation , Soil stabilization , Agricultural waste , Landfills , Fills (Earthwork)
- Type: Article
- Identifier: http://ujcontent.uj.ac.za8080/10210/386034 , uj:5050 , http://hdl.handle.net/10210/13589
- Description: Soil treatment is of vital concern in geoenvironmental and construction engineering in present times as suitable naturally occurring materials are rapidly depleted. Efforts are continually invested towards the resourceful utilization of wastes as fillers, cement enhancers, stabilizers and blenders with little or no significant impacts on the environment. This paper explains the use of a locally available and abundant agricultural waste- Rice husk ash (RHA) in West Africa, Nigeria for the treatment and stabilization of kaolinitic clay (KC) sampled from an active landfill site in Johannesburg, South Africa. The impact of incorporating different percentages of RHA on the compressibility characteristics of a parent compressible landfill KC sample was investigated under a One-dimensional consolidation test. Compacted soil specimens were treated at optimum water content (OWC) and maximum dry unit weight (MDUW) by the addition of agricultural waste material to the parent KC. The compacted specimens were subjected incremental vertical loading in a fixed ring consolidometer device. This was done with a view to closely simulate the waste loading effects from a typical landfill on a treated and parent clay/clayey bottom barrier based on one-dimensional consolidation behaviours. The introduction of RHA waste material to the parent KC revealed an outcome with substantial improvements in compaction characteristics. Hence, the results presented herein showed the agricultural waste to positively increase one-dimensional rigidity while settlement was effectively decreased. From results and analysis, the KC stabilized with RHA can withstand loadings from waste heaps under conditions as were applied in this study. With due recommended examination by geoenvironmental specialists, the stabilized material may be considered as an environmental and cost saving beneficiation approach for use in landfill liners.
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Geotechnical properties of marginal highway backfill stabilized with activated fly ash
- Authors: Aneke, Ikechukwu Frank
- Date: 2015
- Subjects: Engineering geology , Geotechnical engineering , Reliability , Soil stabilization , Fly ash
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/82735 , uj:18995
- Description: Abstract: Soil stabilized with fly ash is the most frequently used method in improvement of the geotechnical properties of soil in South Africa and it is increasingly gaining interest internationally. However, South Africa has several standards and regulations for the use of fly ash and other by products in the soil stabilization process as well as in concrete production. Activated fly ash has not been explored for stabilization of soils in South Africa. Therefore, the present study is an attempt to empirically evaluate the use of chemically activated class „F‟ fly ash obtained from Lethabo power plant in South Africa. The use of the activated fly ash could improve the geotechnical properties [including consistency limits, compaction properties, unconfined compressive strength (UCS), elasticity modulus, durability, california bearing ratio (CBR) and hydraulic conductivity]of the two different fine-grained soils tested in this study. A Red soil sample collected from Parktown, Johannesburg, South Africa was studied in two combinations; a proportion of 50% Kaolinite + 50% Red soil = Kaolinite soil and 30% Bentonite + 20% Kaolinite + 50% Red soil = Bentonite soil. Soils used in the study were built up from the red soil with different proportions to Bentonite and Kaolinite clays. One of the significant objectives of this study was to use mechanically and chemically activated class „F‟ fly ash to improve the geotechnical properties of the heavy clay content soils and to compare these properties with those of the same soils when untreated... , M.Ing. (Civil Engineering)
- Full Text:
- Authors: Aneke, Ikechukwu Frank
- Date: 2015
- Subjects: Engineering geology , Geotechnical engineering , Reliability , Soil stabilization , Fly ash
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/82735 , uj:18995
- Description: Abstract: Soil stabilized with fly ash is the most frequently used method in improvement of the geotechnical properties of soil in South Africa and it is increasingly gaining interest internationally. However, South Africa has several standards and regulations for the use of fly ash and other by products in the soil stabilization process as well as in concrete production. Activated fly ash has not been explored for stabilization of soils in South Africa. Therefore, the present study is an attempt to empirically evaluate the use of chemically activated class „F‟ fly ash obtained from Lethabo power plant in South Africa. The use of the activated fly ash could improve the geotechnical properties [including consistency limits, compaction properties, unconfined compressive strength (UCS), elasticity modulus, durability, california bearing ratio (CBR) and hydraulic conductivity]of the two different fine-grained soils tested in this study. A Red soil sample collected from Parktown, Johannesburg, South Africa was studied in two combinations; a proportion of 50% Kaolinite + 50% Red soil = Kaolinite soil and 30% Bentonite + 20% Kaolinite + 50% Red soil = Bentonite soil. Soils used in the study were built up from the red soil with different proportions to Bentonite and Kaolinite clays. One of the significant objectives of this study was to use mechanically and chemically activated class „F‟ fly ash to improve the geotechnical properties of the heavy clay content soils and to compare these properties with those of the same soils when untreated... , M.Ing. (Civil Engineering)
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A holistic approach to open-pit slope stability using Artificial Neural Networks and Rock Engineering Systems Approach
- Authors: Fakir, Muhammad
- Date: 2018
- Subjects: Strip mining - Planning , Slopes (Soil mechanics) , Rock mechanics , Soil stabilization , Earth construction
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280443 , uj:30135
- Description: M.Phil. (Civil Engineering) , Abstract: As open-pit mines become deeper, the stability aspects of large slopes can be at the limit or beyond precedent practice. There are new design demands, scale related challenges, continuous blasting effect to the rock mass, various complex interactions between rock stress, fractures, and water flow, over long periods. Thus, there is a greater probability of slope failure associated with deeper and eventually steeper slope development. Interactions between the factors affecting slope stability in open-pit mines are therefore more complex and often difficult to define. Determination of the non-linear behaviour of such a multivariate dynamic system is often challenging and demanding. In addition, the problem is often dictated by non-linear equations. Therefore, there is a need for the proposal of an intelligent slope stability index. A new objective holistic approach is proposed in order to address the status of stability of slopes in open-pit mines. Through this approach the primary role of rock mass structure, in situ stress, waterflow, and construction effect have been extended into 18 system parameters describing the overall environment, intact rock quality, rock mass properties, in situ rock stress, hydraulic conditions, discontinuities properties, geometry, construction, and history of instabilities. Soft computing methods such as Back Propagation, Self-Organising Maps, and Artificial Neuro Fuzzy Inference System algorithms are used in conjunction with the Rock Engineering Systems approach to assess the stability status of 141 open-pit slopes in a complex rock engineering system. Implementation of the Rock Engineering System allows for the complex interaction investigation between the influential parameters using the generic interaction matrix. The central reasoning behind employing ANN to slope stability in open-pit mines is its ability to identify interesting and useful patterns in data. Hence, new knowledge is gained with regards to the open-pit engineering environment in an attempt to reduce the associate uncertainty. An Intelligent Open-pit Mine Slope Stability Index is proposed to assess the potential status regime from an objective holistic point of view. The reliability of the predictive capability is computed as the Mean Squared Error, and further validated through a Receiver Operating Characteristic curve. Together with the Mean Squared Error, and Receiver Operating Characteristic curve of 92%, 97% and 98% for Back Propagation, Self-Organising Map, and Artificial Neuro Fuzzy Inference System respectively, the application illustrates that the prediction of slope stability through Artificial Neural Networks produces fast convergence giving reliable predictions, and thus being a useful tool at the preliminary stage of open-pit slope stability project.
- Full Text:
- Authors: Fakir, Muhammad
- Date: 2018
- Subjects: Strip mining - Planning , Slopes (Soil mechanics) , Rock mechanics , Soil stabilization , Earth construction
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280443 , uj:30135
- Description: M.Phil. (Civil Engineering) , Abstract: As open-pit mines become deeper, the stability aspects of large slopes can be at the limit or beyond precedent practice. There are new design demands, scale related challenges, continuous blasting effect to the rock mass, various complex interactions between rock stress, fractures, and water flow, over long periods. Thus, there is a greater probability of slope failure associated with deeper and eventually steeper slope development. Interactions between the factors affecting slope stability in open-pit mines are therefore more complex and often difficult to define. Determination of the non-linear behaviour of such a multivariate dynamic system is often challenging and demanding. In addition, the problem is often dictated by non-linear equations. Therefore, there is a need for the proposal of an intelligent slope stability index. A new objective holistic approach is proposed in order to address the status of stability of slopes in open-pit mines. Through this approach the primary role of rock mass structure, in situ stress, waterflow, and construction effect have been extended into 18 system parameters describing the overall environment, intact rock quality, rock mass properties, in situ rock stress, hydraulic conditions, discontinuities properties, geometry, construction, and history of instabilities. Soft computing methods such as Back Propagation, Self-Organising Maps, and Artificial Neuro Fuzzy Inference System algorithms are used in conjunction with the Rock Engineering Systems approach to assess the stability status of 141 open-pit slopes in a complex rock engineering system. Implementation of the Rock Engineering System allows for the complex interaction investigation between the influential parameters using the generic interaction matrix. The central reasoning behind employing ANN to slope stability in open-pit mines is its ability to identify interesting and useful patterns in data. Hence, new knowledge is gained with regards to the open-pit engineering environment in an attempt to reduce the associate uncertainty. An Intelligent Open-pit Mine Slope Stability Index is proposed to assess the potential status regime from an objective holistic point of view. The reliability of the predictive capability is computed as the Mean Squared Error, and further validated through a Receiver Operating Characteristic curve. Together with the Mean Squared Error, and Receiver Operating Characteristic curve of 92%, 97% and 98% for Back Propagation, Self-Organising Map, and Artificial Neuro Fuzzy Inference System respectively, the application illustrates that the prediction of slope stability through Artificial Neural Networks produces fast convergence giving reliable predictions, and thus being a useful tool at the preliminary stage of open-pit slope stability project.
- Full Text:
Desilication of fly ash and geotechnical applications of the desilicated fly ash
- Authors: Falayi, Thabo
- Date: 2016
- Subjects: Geotechnical engineering , Engineering geology , Soil stabilization , Fly ash
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/233013 , uj:23780
- Description: D.Phil. (Civil Engineering Science) , Abstract: Silica was leached from fly ash (FA) produced by Camden power station (South Africa). The residue, desilicated fly ash (DFA) was then stabilised using lime and alkaline activation. The stabilised residue was then used as a soil stabiliser. Camden FA was found to have a basic pH (10.7) whilst DFA was more basic (12.3) due to a higher K2O content.The major difference between DFA and FA was the presence of a zeolite (Phillipsite K) in DFA. Radiological analysis showed that the activity concentrations of 226Ra, 232Th and 40K for both DFA and FA were below the limits of the South African Government Gazette of 2006. Silica was leached from FA using KOH. The leaching parameters investigated were leaching time, KOH concentration, agitation speed, FA particle size, leaching temperature and liquid solid ratio (L/S). It was found that the optimum leaching conditions were leaching time of 6 h, 3 M KOH, 500 rpm agitation speed, 25 L/S ratio, leaching temperature of 100˚C. The yield was found to be 283.7 g of silica per kg of FA. Silica leaching followed a modified Jander equation kinetics with an N value of 1.48 and an activation energy of 5.9 kJ/mol. DFA was stabilised using lime at elevated temperatures. DFA and lime were mixed in different ratios at optimum moisture content and maximum dry density and then cured at 40ºC, 80ºC and 100ºC for 4 days. 80ºC was found to be the optimum curing temperature. The DFA: lime ratio of 70:30 was found to have an average UCS of 8.8 MPa. Lime consumption was found to follow modified Jander kinetics with activation energy of 16 kJ/mol. Toxicity leaching tests showed a 79% reduction in the leachability of trace and heavy metals. The composite met the minimum requirement of ASTM C34-13 and South African burnt clay standard (SANS227:2007). The influence of open porosity, sum of hydration products and extent of DFA hydration on the strength of DFA lime composites was also studied. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of fly ash/desilicated fly ash hydration and sum of hydration products) had the greatest influence on the UCS than individually with correlation coefficients above 0.98. The use of DFA-lime composite as a stabiliser for expansive soil was also studied. A 70:30 DFA: lime composite was used as the stabiliser. The 30% stabilised soil was found to have a UCS of 4.1 MPa. The stabilised soil met the minimum requirements for the American Concrete Institute’s requirements for backfill material. A 40% addition of FA: lime composite was the optimum for the stabilisation of the same expansive soil. DFA composite stabilisation was better than the FA composite stabilisation due to a superior UCS (4.1 vs 2.62 MPa), better 24 h soak UCS (3.62 vs 0.98 MPa) and a better saturation coefficient 0.35 vs 0.68...
- Full Text:
- Authors: Falayi, Thabo
- Date: 2016
- Subjects: Geotechnical engineering , Engineering geology , Soil stabilization , Fly ash
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/233013 , uj:23780
- Description: D.Phil. (Civil Engineering Science) , Abstract: Silica was leached from fly ash (FA) produced by Camden power station (South Africa). The residue, desilicated fly ash (DFA) was then stabilised using lime and alkaline activation. The stabilised residue was then used as a soil stabiliser. Camden FA was found to have a basic pH (10.7) whilst DFA was more basic (12.3) due to a higher K2O content.The major difference between DFA and FA was the presence of a zeolite (Phillipsite K) in DFA. Radiological analysis showed that the activity concentrations of 226Ra, 232Th and 40K for both DFA and FA were below the limits of the South African Government Gazette of 2006. Silica was leached from FA using KOH. The leaching parameters investigated were leaching time, KOH concentration, agitation speed, FA particle size, leaching temperature and liquid solid ratio (L/S). It was found that the optimum leaching conditions were leaching time of 6 h, 3 M KOH, 500 rpm agitation speed, 25 L/S ratio, leaching temperature of 100˚C. The yield was found to be 283.7 g of silica per kg of FA. Silica leaching followed a modified Jander equation kinetics with an N value of 1.48 and an activation energy of 5.9 kJ/mol. DFA was stabilised using lime at elevated temperatures. DFA and lime were mixed in different ratios at optimum moisture content and maximum dry density and then cured at 40ºC, 80ºC and 100ºC for 4 days. 80ºC was found to be the optimum curing temperature. The DFA: lime ratio of 70:30 was found to have an average UCS of 8.8 MPa. Lime consumption was found to follow modified Jander kinetics with activation energy of 16 kJ/mol. Toxicity leaching tests showed a 79% reduction in the leachability of trace and heavy metals. The composite met the minimum requirement of ASTM C34-13 and South African burnt clay standard (SANS227:2007). The influence of open porosity, sum of hydration products and extent of DFA hydration on the strength of DFA lime composites was also studied. For both FA and DFA it was observed that the three parameters combined (open porosity, extent of fly ash/desilicated fly ash hydration and sum of hydration products) had the greatest influence on the UCS than individually with correlation coefficients above 0.98. The use of DFA-lime composite as a stabiliser for expansive soil was also studied. A 70:30 DFA: lime composite was used as the stabiliser. The 30% stabilised soil was found to have a UCS of 4.1 MPa. The stabilised soil met the minimum requirements for the American Concrete Institute’s requirements for backfill material. A 40% addition of FA: lime composite was the optimum for the stabilisation of the same expansive soil. DFA composite stabilisation was better than the FA composite stabilisation due to a superior UCS (4.1 vs 2.62 MPa), better 24 h soak UCS (3.62 vs 0.98 MPa) and a better saturation coefficient 0.35 vs 0.68...
- Full Text:
Validation of the vibrating hammer for soil compaction control
- Authors: Lange, Desmond Peter
- Date: 2012-02-06
- Subjects: Soil compaction , Soil stabilization , Vibratory compacting
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/382575 , uj:1976 , http://hdl.handle.net/10210/4332
- Description: M.Tech. , There is a general lack of understanding of the laboratory compaction test based on the vibrating hammer method. The impact method of testing soil in the laboratory is conservatively used by engineers for design and construction control purposes even when the specified mode of compaction on site is vibratory. Furthermore, the effects of vibratory compaction are not fully understood, and hence this mode of compaction in the field has not always been effectively utilized. The objective of this research project was to determine whether the vibrating hammer method could be used in the laboratory for design and control purposes, through an investigation of its operating characteristics, and a comparison of its effectiveness against that of the impact method, following a study of the compaction properties of a range of different soils used in road and embankment construction. The results of the study showed that the vibrating hammer can be used in place of impact in the laboratory for non-cohesive soils and gravels. In one instance, vibratory compaction produced maximum dry densities for a decomposed granite which were almost 5 % higher than that for impact compaction. Cohesive soils reached maximum compaction at moisture contents which were 7 % wetter under the vibratory mode as opposed to those for impact, but at lower densities. This showed that field densities under vibratory compaction would be difficult to achieve when the laboratory control method was based on impact. The research showed that electrical power input to the vibrating hammer must be carefully regulated in order to maintain specified standards which are based on a fixed frequency. Further study based on operation at different frequencies would be required to determine whether the vibrating hammer would be suitable for cohesive soils having natural frequencies lower than the current standard specified.
- Full Text:
- Authors: Lange, Desmond Peter
- Date: 2012-02-06
- Subjects: Soil compaction , Soil stabilization , Vibratory compacting
- Type: Thesis
- Identifier: http://ujcontent.uj.ac.za8080/10210/382575 , uj:1976 , http://hdl.handle.net/10210/4332
- Description: M.Tech. , There is a general lack of understanding of the laboratory compaction test based on the vibrating hammer method. The impact method of testing soil in the laboratory is conservatively used by engineers for design and construction control purposes even when the specified mode of compaction on site is vibratory. Furthermore, the effects of vibratory compaction are not fully understood, and hence this mode of compaction in the field has not always been effectively utilized. The objective of this research project was to determine whether the vibrating hammer method could be used in the laboratory for design and control purposes, through an investigation of its operating characteristics, and a comparison of its effectiveness against that of the impact method, following a study of the compaction properties of a range of different soils used in road and embankment construction. The results of the study showed that the vibrating hammer can be used in place of impact in the laboratory for non-cohesive soils and gravels. In one instance, vibratory compaction produced maximum dry densities for a decomposed granite which were almost 5 % higher than that for impact compaction. Cohesive soils reached maximum compaction at moisture contents which were 7 % wetter under the vibratory mode as opposed to those for impact, but at lower densities. This showed that field densities under vibratory compaction would be difficult to achieve when the laboratory control method was based on impact. The research showed that electrical power input to the vibrating hammer must be carefully regulated in order to maintain specified standards which are based on a fixed frequency. Further study based on operation at different frequencies would be required to determine whether the vibrating hammer would be suitable for cohesive soils having natural frequencies lower than the current standard specified.
- Full Text:
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