Pub Date : 2023-03-01DOI: 10.1680/jgrim.2023.176.1.67
{"title":"<i>Ground Improvement</i>: Referees 2022","authors":"","doi":"10.1680/jgrim.2023.176.1.67","DOIUrl":"https://doi.org/10.1680/jgrim.2023.176.1.67","url":null,"abstract":"","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"19 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-03-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136173714","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Shashika Atapattu, B. Indraratna, Cholachat Rujikiatkamjorn
Railways are often subjected to periodic cyclic loading and intermittent rest periods. Excessive consolidation settlements can affect the performance of railway tracks built on the soft subgrade. The consolidation behavior under railway loading conditions with rest periods has not been evaluated thoroughly. In this study, laboratory testing was conducted to investigate the influence of periodic cyclic loading and rest periods on the consolidation of Holocene soft clay from Ballina NSW. The specimens were subjected to a loading frequency of 1Hz for 54hrs with multiple rest periods. The recorded settlements and excess pore water pressures (EPWP) during cyclic consolidation were employed to determine the corresponding hydraulic gradient, void ratio, resilient (dynamic) modulus and damping ratio. The settlement and accumulated EPWP can be observed during cyclic loading. In contrast, settlements do not occur within a rest period, despite the rapidly dissipating EPWP at the start of a given rest period. The maximum EPWP and settlements decrease as the number of resting periods increases. An analytical model capturing the effect of cyclic loading and rest period is proposed where the unique relationships between the hydraulic gradient and the flow rate are established.
{"title":"Influence of periodic cyclic loading and rest period on soft clay consolidation in railway subgrades","authors":"Shashika Atapattu, B. Indraratna, Cholachat Rujikiatkamjorn","doi":"10.1680/jgrim.22.00082","DOIUrl":"https://doi.org/10.1680/jgrim.22.00082","url":null,"abstract":"Railways are often subjected to periodic cyclic loading and intermittent rest periods. Excessive consolidation settlements can affect the performance of railway tracks built on the soft subgrade. The consolidation behavior under railway loading conditions with rest periods has not been evaluated thoroughly. In this study, laboratory testing was conducted to investigate the influence of periodic cyclic loading and rest periods on the consolidation of Holocene soft clay from Ballina NSW. The specimens were subjected to a loading frequency of 1Hz for 54hrs with multiple rest periods. The recorded settlements and excess pore water pressures (EPWP) during cyclic consolidation were employed to determine the corresponding hydraulic gradient, void ratio, resilient (dynamic) modulus and damping ratio. The settlement and accumulated EPWP can be observed during cyclic loading. In contrast, settlements do not occur within a rest period, despite the rapidly dissipating EPWP at the start of a given rest period. The maximum EPWP and settlements decrease as the number of resting periods increases. An analytical model capturing the effect of cyclic loading and rest period is proposed where the unique relationships between the hydraulic gradient and the flow rate are established.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"7 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-02-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88023112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Surcharging or preloading is one of the oldest and most widely used in-situ ground improvement techniques to strengthen weak compressible clays and to remove undesirable settlements prior to erection of permanent infrastructure. Recently, the ground improvement technique has been adopted in combination with many other techniques. The current design methodology for surcharging based on the concept of average degree of consolidation is inadequate, as all the primary consolidation settlement to be induced by the permanent load is not eliminated by the surcharging process. The problem is quantitatively analyzed using Terzaghi's one-dimensional consolidation theory. The proportion of residual primary consolidation settlement is quantified, and the starting time of the re-occurrence of primary consolidation upon exertion of the permanent load is determined. The effect of a change in surcharging duration on the proportion of residual settlement is quantified. The results are presented in design charts to facilitate application of the results by practicing geotechnical engineers.
{"title":"Improved analysis and design for surcharging","authors":"A. Yeung, S. T. So","doi":"10.1680/jgrim.22.00044","DOIUrl":"https://doi.org/10.1680/jgrim.22.00044","url":null,"abstract":"Surcharging or preloading is one of the oldest and most widely used in-situ ground improvement techniques to strengthen weak compressible clays and to remove undesirable settlements prior to erection of permanent infrastructure. Recently, the ground improvement technique has been adopted in combination with many other techniques. The current design methodology for surcharging based on the concept of average degree of consolidation is inadequate, as all the primary consolidation settlement to be induced by the permanent load is not eliminated by the surcharging process. The problem is quantitatively analyzed using Terzaghi's one-dimensional consolidation theory. The proportion of residual primary consolidation settlement is quantified, and the starting time of the re-occurrence of primary consolidation upon exertion of the permanent load is determined. The effect of a change in surcharging duration on the proportion of residual settlement is quantified. The results are presented in design charts to facilitate application of the results by practicing geotechnical engineers.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"28 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78377014","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Electrokinetic (EK) has been proven to effectively consolidate ultra-soft geomaterials, such as coal washeries, mine tailings, oil sands tailings, etc. The conventional consolidation model based on the small strain theory encountered difficulties with these geomaterials because of continuous changes in material properties during consolidation. This research developed a one-dimensional large strain EK consolidation model (LSEK-1D) for ultra-soft geomaterials. The model is validated using experimental laboratory results regarding settlements and times on mature fine oil sand tailings (MFT), a major environmental challenge for the oil industry in Northern Alberta, Canada. Moreover, the effects of initial sample heights and applied current densities on consolidation times are evaluated. The experimental data on consolidation times of MFT is consistent with the LSEK-1D model. The LSEK-1D model was used to find the scale effect of drainage path on the EK consolidation behavior of MFT. The model can also be used for other ultra-soft geomaterials and to facilitate the geotechnical engineering design for EK application.
{"title":"One-dimensional large strain electroosmotic consolidation of ultra-soft geomaterials","authors":"Yu Guo, J. Q. Shang","doi":"10.1680/jgrim.22.00050","DOIUrl":"https://doi.org/10.1680/jgrim.22.00050","url":null,"abstract":"Electrokinetic (EK) has been proven to effectively consolidate ultra-soft geomaterials, such as coal washeries, mine tailings, oil sands tailings, etc. The conventional consolidation model based on the small strain theory encountered difficulties with these geomaterials because of continuous changes in material properties during consolidation. This research developed a one-dimensional large strain EK consolidation model (LSEK-1D) for ultra-soft geomaterials. The model is validated using experimental laboratory results regarding settlements and times on mature fine oil sand tailings (MFT), a major environmental challenge for the oil industry in Northern Alberta, Canada. Moreover, the effects of initial sample heights and applied current densities on consolidation times are evaluated. The experimental data on consolidation times of MFT is consistent with the LSEK-1D model. The LSEK-1D model was used to find the scale effect of drainage path on the EK consolidation behavior of MFT. The model can also be used for other ultra-soft geomaterials and to facilitate the geotechnical engineering design for EK application.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"99 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-02-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81022979","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Abouzar Esfandyaripour, S. H. Lajevardi, H. Molaabasi
Incorporating zeolite for the enhanced treatment of the cement-treated sands, apart from environmental benefits and saving cost and time, results in the improvement of pozzolanic reactions and hence, the failure mechanisms over time. Besides, reinforcing these samples with fibers can be a further contribution to mitigate the brittle behavior along with increasing the strength characteristics of the base soil. The main focus of the current study is to investigate the changes of the stress-strain (q–ε) relationships and the micro-character of the zeolite-cement treated sands with and without fibers subjected to the drained behavior. In this regard, the samples were prepared with cement content of 4%, zeolite contents of 15, 30, 45 and 60% (cement replacement) and fiber content of 0.5%, considering the relative density of 50% and 56 days of curing time. The consolidated drained (CD) triaxial tests with confining pressures of 50, 100 and 200 kPa and SEM analysis were performed. Crucial geotechnical parameters, obtained from the q–ε curves, like maximum strength (qmax), failure strain (εf), brittle index (BI), secant modulus (E50), cohesion (C) and internal friction angle (ϕ) were evaluated. The results indicated that concurrent use of fiber and zeolite substantially modified the high brittle index and low failure strain of the cement-treated sands. In fact, zeolite incorporation in the mixture enhanced the post-peak behavior while post-peak stresses in cement-treated sands experienced a dramatic drop. Besides, observational analysis from SEM micrographs confirmed that pores were roughly filled up in the optimum zeolite content and more tension resistance were witnessed in the fiber-reinforced samples. Furthermore, fibers in the zeolite-cement treated samples exposed to less tension rather than cement-treated ones. Zeolite fully covered the fibers and helped them to provide more resistance, hence, prevented the complete failure and improved the strain-hardening characteristics.
{"title":"An experimental study to examine the effect of fiber and natural pozzolan on the failure characteristics of a cement-treated sand","authors":"Abouzar Esfandyaripour, S. H. Lajevardi, H. Molaabasi","doi":"10.1680/jgrim.22.00024","DOIUrl":"https://doi.org/10.1680/jgrim.22.00024","url":null,"abstract":"Incorporating zeolite for the enhanced treatment of the cement-treated sands, apart from environmental benefits and saving cost and time, results in the improvement of pozzolanic reactions and hence, the failure mechanisms over time. Besides, reinforcing these samples with fibers can be a further contribution to mitigate the brittle behavior along with increasing the strength characteristics of the base soil. The main focus of the current study is to investigate the changes of the stress-strain (q–ε) relationships and the micro-character of the zeolite-cement treated sands with and without fibers subjected to the drained behavior. In this regard, the samples were prepared with cement content of 4%, zeolite contents of 15, 30, 45 and 60% (cement replacement) and fiber content of 0.5%, considering the relative density of 50% and 56 days of curing time. The consolidated drained (CD) triaxial tests with confining pressures of 50, 100 and 200 kPa and SEM analysis were performed. Crucial geotechnical parameters, obtained from the q–ε curves, like maximum strength (qmax), failure strain (εf), brittle index (BI), secant modulus (E50), cohesion (C) and internal friction angle (ϕ) were evaluated. The results indicated that concurrent use of fiber and zeolite substantially modified the high brittle index and low failure strain of the cement-treated sands. In fact, zeolite incorporation in the mixture enhanced the post-peak behavior while post-peak stresses in cement-treated sands experienced a dramatic drop. Besides, observational analysis from SEM micrographs confirmed that pores were roughly filled up in the optimum zeolite content and more tension resistance were witnessed in the fiber-reinforced samples. Furthermore, fibers in the zeolite-cement treated samples exposed to less tension rather than cement-treated ones. Zeolite fully covered the fibers and helped them to provide more resistance, hence, prevented the complete failure and improved the strain-hardening characteristics.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"126 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-01-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86771574","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
M. E. El Sawwaf, M. Shahien, A. Nasr, Mahmoud S. Habib
This article presents a comprehensive study of using xanthan gum, sodium alginate, and gelatin to stabilize collapsible soil. Modified Proctor, one-dimensional collapse, unconsolidated undrained triaxial, and California bearing ratio (CBR) tests were conducted to estimate the engineering characteristics of the untreated and treated soil. Additionally, X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were utilized to demonstrate the changes in the microstructure of the treated samples. It was found that biopolymers decreased the maximum dry density and increased the optimum water content. The results also indicated that a 4% content of xanthan gum, sodium alginate, and gelatin significantly reduced the collapse index by 96%, 95%, and 82%, respectively. Shear tests showed that biopolymers slightly reduced the internal friction angle and significantly increased the cohesion intercept, which led to shear strength improvement. The results also indicated that 4% xanthan gum-treated samples, 4% sodium alginate-treated samples, and 4% gelatin-treated samples exhibited higher shear strengths by 145%, 106%, and 73%, respectively, than the untreated sample under the same conditions. The findings also indicated that when the soil was mixed with a 4% concentration of xanthan gum, sodium alginate, and gelatin, the unsoaked CBR value increased by about 185%, 157%, and 141%, respectively. The results of SEM and XRD studies also demonstrated the interaction between the fine-grained particles and the biopolymers.
{"title":"A comparative study of stabilizing collapsible soil using different types of biopolymers","authors":"M. E. El Sawwaf, M. Shahien, A. Nasr, Mahmoud S. Habib","doi":"10.1680/jgrim.22.00072","DOIUrl":"https://doi.org/10.1680/jgrim.22.00072","url":null,"abstract":"This article presents a comprehensive study of using xanthan gum, sodium alginate, and gelatin to stabilize collapsible soil. Modified Proctor, one-dimensional collapse, unconsolidated undrained triaxial, and California bearing ratio (CBR) tests were conducted to estimate the engineering characteristics of the untreated and treated soil. Additionally, X-ray diffraction (XRD) and scanning electron microscopy (SEM) tests were utilized to demonstrate the changes in the microstructure of the treated samples. It was found that biopolymers decreased the maximum dry density and increased the optimum water content. The results also indicated that a 4% content of xanthan gum, sodium alginate, and gelatin significantly reduced the collapse index by 96%, 95%, and 82%, respectively. Shear tests showed that biopolymers slightly reduced the internal friction angle and significantly increased the cohesion intercept, which led to shear strength improvement. The results also indicated that 4% xanthan gum-treated samples, 4% sodium alginate-treated samples, and 4% gelatin-treated samples exhibited higher shear strengths by 145%, 106%, and 73%, respectively, than the untreated sample under the same conditions. The findings also indicated that when the soil was mixed with a 4% concentration of xanthan gum, sodium alginate, and gelatin, the unsoaked CBR value increased by about 185%, 157%, and 141%, respectively. The results of SEM and XRD studies also demonstrated the interaction between the fine-grained particles and the biopolymers.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"10 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2023-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74719346","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Vamsi N. K. Mypati, S. Saride, Subrahmanyam Challapalli
The present study investigates the durability and leachate behavior of an alkali-activated fly ash (FA) as a binder to stabilize expansive soils in deep mixing applications. To activate FA, a liquid alkali activator (LAA) to binder ratio (LAA/FA) was introduced and varied from 1.0 to 1.5. Swelling-shrinkage, consolidation and unconfined compressive strength (UCS) characteristics under wetting-drying cycles (durability) were studies on deep mixed expansive soils. Leachate studies were performed to determine the environmental impact of alkali-activated fly ash. Heavy metal and sodium ions concentrations were measured in each leachate cycle. To examine the permanent microstructural and phase changes in the mixes, scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were conducted. The swelling-shrinkage behavior of soil could be marginally controlled for LAA/FA = 1.0 and 1.25 due to heavy weight loss during the wetting-drying cycles. However, even after twelve durability cycles, the unconfined compressive strength (UCS) of soil with LAA/FA =1.5 retained 1.0 MPa and showed non-critical swelling-shrinkage behavior. The heavy metals and sodium ion concentrations were in acceptable range for LAA/FA = 1.25 and 1.5. XRD and SEM studies revealed that soil treated with a binder ratio of LAA/FA = 1.5, showed high crystalline peaks and aggregated structures.
{"title":"Durability of fly ash geopolymer Binder in Deep Mixed Expansive Soils","authors":"Vamsi N. K. Mypati, S. Saride, Subrahmanyam Challapalli","doi":"10.1680/jgrim.22.00015","DOIUrl":"https://doi.org/10.1680/jgrim.22.00015","url":null,"abstract":"The present study investigates the durability and leachate behavior of an alkali-activated fly ash (FA) as a binder to stabilize expansive soils in deep mixing applications. To activate FA, a liquid alkali activator (LAA) to binder ratio (LAA/FA) was introduced and varied from 1.0 to 1.5. Swelling-shrinkage, consolidation and unconfined compressive strength (UCS) characteristics under wetting-drying cycles (durability) were studies on deep mixed expansive soils. Leachate studies were performed to determine the environmental impact of alkali-activated fly ash. Heavy metal and sodium ions concentrations were measured in each leachate cycle. To examine the permanent microstructural and phase changes in the mixes, scanning electron microscopy (SEM) and X-ray diffraction (XRD) studies were conducted. The swelling-shrinkage behavior of soil could be marginally controlled for LAA/FA = 1.0 and 1.25 due to heavy weight loss during the wetting-drying cycles. However, even after twelve durability cycles, the unconfined compressive strength (UCS) of soil with LAA/FA =1.5 retained 1.0 MPa and showed non-critical swelling-shrinkage behavior. The heavy metals and sodium ion concentrations were in acceptable range for LAA/FA = 1.25 and 1.5. XRD and SEM studies revealed that soil treated with a binder ratio of LAA/FA = 1.5, showed high crystalline peaks and aggregated structures.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"27 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2022-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74403383","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Soil stabilization of soil has been carried out by many researchers in the past using conventional materials such as lime, fly ash, silica fumes, quarry dust etc. Ground improvement using enzymes or micro-organisms, fermented from vegetable extracts, has been one of the latest sustainable invents in Geotechnical Engineering. The present work explores and compares the effectiveness of Terrazyme in improving the mechanical properties such as strength and compressibility characteristics of locally available soils. The experimental studies are extended to two soils which possess extreme characteristics namely lateritic and black cotton soils. The work is carried out on 3 different dosages of Terrazyme namely 150 ml/m3, 200 ml/m3 and 250 ml/m3 respectively, obtained through volumetric proportioning. In order to understand the long-term behaviour pattern of Terrazyme, studies are carried out on varying curing periods (7 and 28 days) and results are compared. The results highlight that Terrazyme modification is more effective in black cotton soil than lateritic soil. To evaluate the change in soil fabric brought about on account of enzyme application, scanning electron microscope (SEM) and energy dispersive X Ray analysis (EDAX) studies are performed on these soils. The design of flexible pavement with an enzyme modified subgrade revealed a more robust and sustainable infrastructure solution.
{"title":"Comparative Study on Mechanical Behaviour of Enzyme Modified Soils","authors":"V. Divya, M. Asha","doi":"10.1680/jgrim.22.00029","DOIUrl":"https://doi.org/10.1680/jgrim.22.00029","url":null,"abstract":"Soil stabilization of soil has been carried out by many researchers in the past using conventional materials such as lime, fly ash, silica fumes, quarry dust etc. Ground improvement using enzymes or micro-organisms, fermented from vegetable extracts, has been one of the latest sustainable invents in Geotechnical Engineering. The present work explores and compares the effectiveness of Terrazyme in improving the mechanical properties such as strength and compressibility characteristics of locally available soils. The experimental studies are extended to two soils which possess extreme characteristics namely lateritic and black cotton soils. The work is carried out on 3 different dosages of Terrazyme namely 150 ml/m3, 200 ml/m3 and 250 ml/m3 respectively, obtained through volumetric proportioning. In order to understand the long-term behaviour pattern of Terrazyme, studies are carried out on varying curing periods (7 and 28 days) and results are compared. The results highlight that Terrazyme modification is more effective in black cotton soil than lateritic soil. To evaluate the change in soil fabric brought about on account of enzyme application, scanning electron microscope (SEM) and energy dispersive X Ray analysis (EDAX) studies are performed on these soils. The design of flexible pavement with an enzyme modified subgrade revealed a more robust and sustainable infrastructure solution.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"19 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2022-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89971301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
V. Sivakumar, B. Solan, M. Moorhead, C. Serridge, S. Tripathy, S. Donohue
This paper examines the consolidation and settlement behaviour of soft clays deposits treated with granular columns (single and in groups). Two Rowe Cell loading chambers were used to conduct the investigations on samples of kaolin and a local Belfast natural estuarine alluvium called ‘sleech’. Tests were carried out on unreinforced samples and then reinforced samples with single and multiple column configurations. The test duration for each test was between 3 and 4 months, depending on the test material and the granular column configuration. The settlement reduction factors based on primary and secondary consolidation were examined. The study suggests that the effectiveness of granular columns at mitigating primary and/or secondary settlement is directly related to the loading intensity, the stress history and the creep characteristics of the subsoil. It was also found that the stress concentration ratio reduced with the stress level. Secondary consolidation also has some effects on the stress concentration ratio.
{"title":"A comparative settlement response of soft clays reinforced with granular columns subjected to widespread loading","authors":"V. Sivakumar, B. Solan, M. Moorhead, C. Serridge, S. Tripathy, S. Donohue","doi":"10.1680/jgrim.21.00074","DOIUrl":"https://doi.org/10.1680/jgrim.21.00074","url":null,"abstract":"This paper examines the consolidation and settlement behaviour of soft clays deposits treated with granular columns (single and in groups). Two Rowe Cell loading chambers were used to conduct the investigations on samples of kaolin and a local Belfast natural estuarine alluvium called ‘sleech’. Tests were carried out on unreinforced samples and then reinforced samples with single and multiple column configurations. The test duration for each test was between 3 and 4 months, depending on the test material and the granular column configuration. The settlement reduction factors based on primary and secondary consolidation were examined. The study suggests that the effectiveness of granular columns at mitigating primary and/or secondary settlement is directly related to the loading intensity, the stress history and the creep characteristics of the subsoil. It was also found that the stress concentration ratio reduced with the stress level. Secondary consolidation also has some effects on the stress concentration ratio.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"16 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2022-10-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90779434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anthony L. Wong, P. Chung, Florence L. F. Chu, S. T. So, L. Wong
Deep cement mixing is a typical ground improvement technique, and has recently been introduced in some large-scale reclamation projects in Hong Kong. There is a lack of internationally recognised testing standard for determining the tensile strength of cement stabilised soil. Owing to its low tensile strength and strain at failure, the practical difficulties of these tests are intrinsic. In this study, tensile properties of cement stabilised clay have been investigated using direct tension test and Brazilian test. The interpretation of tensile strength in Brazilian test is not straightforward due to the formation of multiple cracks during loading. As such, focus is given on the validation of the fundamental assumption on crack initiation mechanism. A consolidated database of tensile strength of cement stabilised soil is compiled. A constitutive model in the finite element program PLAXIS, namely Concrete Model, has been studied. This model, originally aiming to simulate the behaviour of concrete and shotcrete, duly considers the cracking and the strain-softening characteristics, and is able to reasonably simulate the fundamental tensile behaviour of cement stabilised soil. Numerical simulations have been conducted using the Concrete Model to assess the stability of seawall founded on cement stabilised clay. Tensile properties are found to have an important bearing in maintaining the seawall stability when column-pattern stabilisation is adopted.
{"title":"Tensile Properties of Cement Stabilised Clay and Their Contribution to Seawall Design","authors":"Anthony L. Wong, P. Chung, Florence L. F. Chu, S. T. So, L. Wong","doi":"10.1680/jgrim.21.00047","DOIUrl":"https://doi.org/10.1680/jgrim.21.00047","url":null,"abstract":"Deep cement mixing is a typical ground improvement technique, and has recently been introduced in some large-scale reclamation projects in Hong Kong. There is a lack of internationally recognised testing standard for determining the tensile strength of cement stabilised soil. Owing to its low tensile strength and strain at failure, the practical difficulties of these tests are intrinsic. In this study, tensile properties of cement stabilised clay have been investigated using direct tension test and Brazilian test. The interpretation of tensile strength in Brazilian test is not straightforward due to the formation of multiple cracks during loading. As such, focus is given on the validation of the fundamental assumption on crack initiation mechanism. A consolidated database of tensile strength of cement stabilised soil is compiled. A constitutive model in the finite element program PLAXIS, namely Concrete Model, has been studied. This model, originally aiming to simulate the behaviour of concrete and shotcrete, duly considers the cracking and the strain-softening characteristics, and is able to reasonably simulate the fundamental tensile behaviour of cement stabilised soil. Numerical simulations have been conducted using the Concrete Model to assess the stability of seawall founded on cement stabilised clay. Tensile properties are found to have an important bearing in maintaining the seawall stability when column-pattern stabilisation is adopted.","PeriodicalId":51705,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Ground Improvement","volume":"12 1","pages":""},"PeriodicalIF":1.2,"publicationDate":"2022-10-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73620305","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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