Qingsong Shen, Jia-ling Wang, Hong-yue Sun, Junwei Shu, Y. Shang
As a result of the siphon phenomenon in soft soil siphon drainage, groundwater is discharged from the soft soil without any power, and this increases the effective stress in the soil. A significant part of the drainage effect is determined by the spacing of the siphon holes. According to the model test presented in this study, the decrease in the groundwater level is more pronounced when the spacing of the siphon holes is smaller. In comparison to the single-hole test, the spacing of 0.4 m is 107.6% larger. Based on subsequent numerical simulations, it has been found that when the hole spacing is reduced to 1.0 m, the decrease in the groundwater level on the 60th day can reach the limit value of 10 m for soft soil with a permeability coefficient of 10−9 m/s. In addition, the field test indicates that the average decrease in the water level of the 0.9 m hole spacing is 75.9% greater than that of 1.8 m, while the time required to reach the same decrease in the water level is 63.6% shorter.
{"title":"Analysis of the influence of siphon hole spacing on soft soil drainage effect","authors":"Qingsong Shen, Jia-ling Wang, Hong-yue Sun, Junwei Shu, Y. Shang","doi":"10.1680/jgeen.22.00145","DOIUrl":"https://doi.org/10.1680/jgeen.22.00145","url":null,"abstract":"As a result of the siphon phenomenon in soft soil siphon drainage, groundwater is discharged from the soft soil without any power, and this increases the effective stress in the soil. A significant part of the drainage effect is determined by the spacing of the siphon holes. According to the model test presented in this study, the decrease in the groundwater level is more pronounced when the spacing of the siphon holes is smaller. In comparison to the single-hole test, the spacing of 0.4 m is 107.6% larger. Based on subsequent numerical simulations, it has been found that when the hole spacing is reduced to 1.0 m, the decrease in the groundwater level on the 60th day can reach the limit value of 10 m for soft soil with a permeability coefficient of 10−9 m/s. In addition, the field test indicates that the average decrease in the water level of the 0.9 m hole spacing is 75.9% greater than that of 1.8 m, while the time required to reach the same decrease in the water level is 63.6% shorter.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79998548","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}
The 36 kilometre haul road for the TengizChevroil Future Growth Project (TCO FGP) at the Tengiz oilfield in Western Kazakhstan provided a unique opportunity to examine the dynamic effect of heavy traffic loading on earthworks. The haul road was constructed to facilitate transport of 252no partially constructed module units from a purpose built terminal in the Caspian Sea to the construction area within the oilfield. The ground underlying the haul road comprises recent, predominantly granular deposits with palaeo-channels of very soft cohesive material up to 4 metres thick. The module units, weighing up to 2300 tonnes, were transported on multi-wheeled trailers imparting a maximum distributed ground bearing pressure of 80kN/m2. The project strategy was that areas underlain by soft cohesive soils would not be treated but a budget would be allocated for maintenance during operation of the road. The haul road was designed using quasi-static loading with checks using limit equilibrium and finite element methods. The construction programme allowed instrumentation installed during the ground investigation to be used to complete a dynamic embankment trial to monitor settlement and pore water pressure response in the underlying soils, which was supplemented by further monitoring during haul road operation. The monitoring indicated that adoption of the quasi-static approach for traffic loading does not realistically reflect short duration dynamic loading on earthworks and that the quasi-static approach is highly conservative when applied to moving loads.
{"title":"TengizChevroil Future Growth Project – The Design of Temporary Haul Roads","authors":"P. Nowak, J. Barr","doi":"10.1680/jgeen.22.00090","DOIUrl":"https://doi.org/10.1680/jgeen.22.00090","url":null,"abstract":"The 36 kilometre haul road for the TengizChevroil Future Growth Project (TCO FGP) at the Tengiz oilfield in Western Kazakhstan provided a unique opportunity to examine the dynamic effect of heavy traffic loading on earthworks. The haul road was constructed to facilitate transport of 252no partially constructed module units from a purpose built terminal in the Caspian Sea to the construction area within the oilfield. The ground underlying the haul road comprises recent, predominantly granular deposits with palaeo-channels of very soft cohesive material up to 4 metres thick. The module units, weighing up to 2300 tonnes, were transported on multi-wheeled trailers imparting a maximum distributed ground bearing pressure of 80kN/m2. The project strategy was that areas underlain by soft cohesive soils would not be treated but a budget would be allocated for maintenance during operation of the road. The haul road was designed using quasi-static loading with checks using limit equilibrium and finite element methods. The construction programme allowed instrumentation installed during the ground investigation to be used to complete a dynamic embankment trial to monitor settlement and pore water pressure response in the underlying soils, which was supplemented by further monitoring during haul road operation. The monitoring indicated that adoption of the quasi-static approach for traffic loading does not realistically reflect short duration dynamic loading on earthworks and that the quasi-static approach is highly conservative when applied to moving loads.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89422328","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}
O. Hamza, A. Kourdey, Yawar Hussian, Abdul-hakim Mawas
This paper investigates the interference effect of closely-spaced foundations on the modulus of subgrade reaction (k) and provides an insight into some of the factors affecting the k-value of a raft foundation when other foundations (isolated footings or other identical rafts) are closely placed on both sides. The investigation adopted a three-dimensional, non-linear Finite Element numerical analysis based on a case study of a residential project with several multi-story buildings constructed on sand underlain by weathered limestone. A site-specific ground investigation was conducted to determine soil properties, which were used to construct 3D numerical models to simulate different arrangements of foundations and estimate the corresponding k-values. The results show that the k-value starts to decrease when the spacing between the foundations becomes less than three times the raft width, and the percentage of reduction in k-value increases in a non-linear way as the spacing decreases further. In addition to spacing, the study revealed that the effect of adjacent foundations depends on their size and the magnitude of their applied pressure. The case study provides a framework for developing a correction factor that can be applied to k-value for improving the structural and geotechnical design of closely-spaced shallow foundations.
{"title":"Evaluation of the Subgrade Reaction for closely-spaced raft and isolated foundations on sand – Case study","authors":"O. Hamza, A. Kourdey, Yawar Hussian, Abdul-hakim Mawas","doi":"10.1680/jgeen.21.00212","DOIUrl":"https://doi.org/10.1680/jgeen.21.00212","url":null,"abstract":"This paper investigates the interference effect of closely-spaced foundations on the modulus of subgrade reaction (k) and provides an insight into some of the factors affecting the k-value of a raft foundation when other foundations (isolated footings or other identical rafts) are closely placed on both sides. The investigation adopted a three-dimensional, non-linear Finite Element numerical analysis based on a case study of a residential project with several multi-story buildings constructed on sand underlain by weathered limestone. A site-specific ground investigation was conducted to determine soil properties, which were used to construct 3D numerical models to simulate different arrangements of foundations and estimate the corresponding k-values. The results show that the k-value starts to decrease when the spacing between the foundations becomes less than three times the raft width, and the percentage of reduction in k-value increases in a non-linear way as the spacing decreases further. In addition to spacing, the study revealed that the effect of adjacent foundations depends on their size and the magnitude of their applied pressure. The case study provides a framework for developing a correction factor that can be applied to k-value for improving the structural and geotechnical design of closely-spaced shallow foundations.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-11-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85312712","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}
This paper summarises work to evaluate the effectiveness of innovative geotechnical slope repair techniques used on National Highways’ slopes. The techniques assessed were live willow poles, Electrokinetic Geosynthetics (EKG) and Fibre Reinforced Soil (FRS) used in place of conventional approaches to reduce the overall impact of various challenges including environmental constraints (habitat and visual), access and utility constraints, and to reduce the scale and/or cost of traffic management and traffic delays. Trials were undertaken over the last 20 years or so, but monitoring was generally limited to just a few years post-construction; longer term evaluation was not generally undertaken. The evaluated success, or otherwise, of the techniques led directly to recommendations for future use ranging from the development of willow pole design guidance and specification information, guidance on further EKG trials, and the cessation of use of FRS, primarily on environmental grounds but also acknowledging the construction difficulties encountered. A life cycle analysis shows significant carbon saving compared to rock fill replacement for each of the techniques. More generic lessons learnt from the trials and the practical application reported were used to produce guidance for future trials of innovative geotechnical repair techniques, including those for slopes.
{"title":"The Assessment of Innovative Geotechnical Slope Repair Techniques","authors":"M. Winter, I. Nettleton, R. Seddon, J. Codd","doi":"10.1680/jgeen.22.00143","DOIUrl":"https://doi.org/10.1680/jgeen.22.00143","url":null,"abstract":"This paper summarises work to evaluate the effectiveness of innovative geotechnical slope repair techniques used on National Highways’ slopes. The techniques assessed were live willow poles, Electrokinetic Geosynthetics (EKG) and Fibre Reinforced Soil (FRS) used in place of conventional approaches to reduce the overall impact of various challenges including environmental constraints (habitat and visual), access and utility constraints, and to reduce the scale and/or cost of traffic management and traffic delays. Trials were undertaken over the last 20 years or so, but monitoring was generally limited to just a few years post-construction; longer term evaluation was not generally undertaken. The evaluated success, or otherwise, of the techniques led directly to recommendations for future use ranging from the development of willow pole design guidance and specification information, guidance on further EKG trials, and the cessation of use of FRS, primarily on environmental grounds but also acknowledging the construction difficulties encountered. A life cycle analysis shows significant carbon saving compared to rock fill replacement for each of the techniques. More generic lessons learnt from the trials and the practical application reported were used to produce guidance for future trials of innovative geotechnical repair techniques, including those for slopes.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-11-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73438124","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}
In the present study, a prediction model for the bearing capacity estimation of strip and ring footing embedded in layered sand is proposed using soft computing approaches, i.e., Artificial Neural Network (ANN) and Random Forest Regression (RFR). In this regard, the required data for the model preparation was generated by performing a lower and upper bound finite elements limit analysis by varying the properties of the top and bottom layers. Two types of layered sand conditions are considered in the study; namely, (i) dense on loose sand and (ii) loose sand on dense sand. The investigation for strip footing was carried out by varying the thickness of the top layer, embedment depth of the foundation, and friction angles of the top and bottom layers. In the case of ring footing, the internal to external diameter ratio forms an additional variable. The bearing capacity was taken as an average of lower and upper bound values. A total of 1222 and 4204 data sets were generated for strip and ring footings, respectively. The models were trained and tested using 70 % and 30 % of the selected data, and the bearing capacity was predicted in normalized form. The performance measures obtained during the training and testing phase suggest that the Random Forest Regression model outperforms the ANN model. Additionally, following the literature, an analytical model was developed to predict the bearing capacity of strip footing on layered sand. The ANN and the generated analytical model predictions agreed with the published experimental data in the literature.
{"title":"Bearing Capacity Prediction of Strip and Ring footings Embedded in Layered Sand","authors":"Pragyan P. Das, V. N. Khatri","doi":"10.1680/jgeen.22.00071","DOIUrl":"https://doi.org/10.1680/jgeen.22.00071","url":null,"abstract":"In the present study, a prediction model for the bearing capacity estimation of strip and ring footing embedded in layered sand is proposed using soft computing approaches, i.e., Artificial Neural Network (ANN) and Random Forest Regression (RFR). In this regard, the required data for the model preparation was generated by performing a lower and upper bound finite elements limit analysis by varying the properties of the top and bottom layers. Two types of layered sand conditions are considered in the study; namely, (i) dense on loose sand and (ii) loose sand on dense sand. The investigation for strip footing was carried out by varying the thickness of the top layer, embedment depth of the foundation, and friction angles of the top and bottom layers. In the case of ring footing, the internal to external diameter ratio forms an additional variable. The bearing capacity was taken as an average of lower and upper bound values. A total of 1222 and 4204 data sets were generated for strip and ring footings, respectively. The models were trained and tested using 70 % and 30 % of the selected data, and the bearing capacity was predicted in normalized form. The performance measures obtained during the training and testing phase suggest that the Random Forest Regression model outperforms the ANN model. Additionally, following the literature, an analytical model was developed to predict the bearing capacity of strip footing on layered sand. The ANN and the generated analytical model predictions agreed with the published experimental data in the literature.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-10-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89195139","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}
T. Miranda, A. Viana, F. F. Martins, Xiangfeng Guo, N. Cristelo, D. Dias
This study applies random field theory to simulate the spatial variability of the ground where a tunnel was excavated in a granitic soil mass, in the city of Porto (Portugal). Numerical analyses are performed using finite element method combined with random field theory to simulate tunnel excavation. A parametric study to analyse the influence of the correlation coefficient is performed. The results are compared with the measured values and the values obtained with the deterministic computation. The performance of the models is evaluated using two measures of error: root mean squared error (RMSE) and mean absolute deviation (MAD). With the random fields approach (correlation length equal to 0.5) values of MAD equal to 2.18 and RMSE equal to 4.16 were obtained, whereas with the deterministic approach values of MAD equal to 2.29 and RMSE equal to 4.26 were obtained. Furthermore, the performance of the models improves as far as the correlation coefficient increases. Therefore, it is concluded that the results obtained using random fields are better than those obtained using the deterministic analysis.
{"title":"Numerical analysis of a tunnel behaviour considering the spatial variability of the geotechnical parameters","authors":"T. Miranda, A. Viana, F. F. Martins, Xiangfeng Guo, N. Cristelo, D. Dias","doi":"10.1680/jgeen.22.00032","DOIUrl":"https://doi.org/10.1680/jgeen.22.00032","url":null,"abstract":"This study applies random field theory to simulate the spatial variability of the ground where a tunnel was excavated in a granitic soil mass, in the city of Porto (Portugal). Numerical analyses are performed using finite element method combined with random field theory to simulate tunnel excavation. A parametric study to analyse the influence of the correlation coefficient is performed. The results are compared with the measured values and the values obtained with the deterministic computation. The performance of the models is evaluated using two measures of error: root mean squared error (RMSE) and mean absolute deviation (MAD). With the random fields approach (correlation length equal to 0.5) values of MAD equal to 2.18 and RMSE equal to 4.16 were obtained, whereas with the deterministic approach values of MAD equal to 2.29 and RMSE equal to 4.26 were obtained. Furthermore, the performance of the models improves as far as the correlation coefficient increases. Therefore, it is concluded that the results obtained using random fields are better than those obtained using the deterministic analysis.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76900902","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}
Groundwater pressure is the main cause of debonding (i.e., tensile failure) of the sprayed waterproofing membrane interface within composite sprayed concrete lined (SCL) tunnels. It is critical to understand the failure mechanisms, the right approach to numerically simulating its effects and the practical implications on lining design and membrane interface testing methodology. This paper answers these questions. The paper first presents a conceptual relationship between the possible groundwater pressure application locations and the stress state and hence potential failure mechanism of the membrane interface in composite SCL tunnels. To quantify stresses in the fully bonded membrane interface, two numerical modelling approaches for the membrane interface with different levels of complexity are introduced. Example numerical analyses of composite beams and whole composite SCL tunnels with fully bonded membrane interface are demonstrated. The results confirm the conceptual relationship between water application location and the stress state and potential failure mechanism of the membrane interface. The results also confirm the proposed two numerical modelling approaches are both able to simulate the effects of groundwater pressure on the stress states of membrane interface and tunnel lining forces. The implications on the tunnel design and testing programme for the sprayed membrane interface are discussed.
{"title":"Groundwater pressure induced failure of sprayed waterproof membrane interface in tunnels","authors":"J. Su, A. Bloodworth","doi":"10.1680/jgeen.22.00111","DOIUrl":"https://doi.org/10.1680/jgeen.22.00111","url":null,"abstract":"Groundwater pressure is the main cause of debonding (i.e., tensile failure) of the sprayed waterproofing membrane interface within composite sprayed concrete lined (SCL) tunnels. It is critical to understand the failure mechanisms, the right approach to numerically simulating its effects and the practical implications on lining design and membrane interface testing methodology. This paper answers these questions. The paper first presents a conceptual relationship between the possible groundwater pressure application locations and the stress state and hence potential failure mechanism of the membrane interface in composite SCL tunnels. To quantify stresses in the fully bonded membrane interface, two numerical modelling approaches for the membrane interface with different levels of complexity are introduced. Example numerical analyses of composite beams and whole composite SCL tunnels with fully bonded membrane interface are demonstrated. The results confirm the conceptual relationship between water application location and the stress state and potential failure mechanism of the membrane interface. The results also confirm the proposed two numerical modelling approaches are both able to simulate the effects of groundwater pressure on the stress states of membrane interface and tunnel lining forces. The implications on the tunnel design and testing programme for the sprayed membrane interface are discussed.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73750183","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}
A. Azhari, A. Y. Bafghi, L. Faramarzi, Ramin Salamat Mamakani
Most studies on open-pit mine stability have been performed in the two-dimensional (2-D) mode which neglected the effect of the circular shape and thus the effect of third direction boundary conditions. This paper aims to study the effect of the third dimension in static and dynamic stability analyses of pit slopes, comparing results from 2-D and 3-D numerical and limit equilibrium analyses. The geomechanical data from Choghart open pit mine located in the seismically active area in central Iran is considered, under a historical earthquake (Mw=6.4). Kinematic analyses showed that two tectonic blocks of the mine namely, BL1 and BL2 are susceptive to wedge and planar failures, respectively. From the 2-D and 3-D static analyses, both blocks are stable with higher safety factors for numerical 3-D analyses. For dynamic analyses, unlike BL1 where both 2-D and 3-D analyses showed wedge instability, for BL2 the 2-D numerical analyses showed instability, whereas the 3-D numerical and pseudo-static analyses indicated the block stability. The results revealed that the 3-D safety factors are generally 20 to 40 percent greater than the ones from 2-D analyses. This can be explained by the consideration of the third direction effect, verifying the importance of 3-D analysis.
{"title":"Significance of three-dimensional analyses on static and seismic stability analyses of fractured open-pit mine slopes","authors":"A. Azhari, A. Y. Bafghi, L. Faramarzi, Ramin Salamat Mamakani","doi":"10.1680/jgeen.21.00030","DOIUrl":"https://doi.org/10.1680/jgeen.21.00030","url":null,"abstract":"Most studies on open-pit mine stability have been performed in the two-dimensional (2-D) mode which neglected the effect of the circular shape and thus the effect of third direction boundary conditions. This paper aims to study the effect of the third dimension in static and dynamic stability analyses of pit slopes, comparing results from 2-D and 3-D numerical and limit equilibrium analyses. The geomechanical data from Choghart open pit mine located in the seismically active area in central Iran is considered, under a historical earthquake (Mw=6.4). Kinematic analyses showed that two tectonic blocks of the mine namely, BL1 and BL2 are susceptive to wedge and planar failures, respectively. From the 2-D and 3-D static analyses, both blocks are stable with higher safety factors for numerical 3-D analyses. For dynamic analyses, unlike BL1 where both 2-D and 3-D analyses showed wedge instability, for BL2 the 2-D numerical analyses showed instability, whereas the 3-D numerical and pseudo-static analyses indicated the block stability. The results revealed that the 3-D safety factors are generally 20 to 40 percent greater than the ones from 2-D analyses. This can be explained by the consideration of the third direction effect, verifying the importance of 3-D analysis.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82838197","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}
Micropiles are often implemented through drilling, steel pipe installation, reinforcement, and grouting. However, in some parts of the world, especially in the areas with fine-grained soils, these shafts are implemented by steel pile driving, followed by reinforcement, and grouting has been expanded considerably. In this study, micropile shafts were installed at the site by both driving and drilling methods. Reinforcement and grouting were carried out by the two-step grouting and applying different grouting pressures in micropiles. Some boreholes (at a distance of 0.3 m from the micropile axis) and test pits were drilled to investigate the penetration radius of the grout at different grouting pressures. Results showed that the bearing capacity of driven micropiles is about 4% to 14% more than that of the drilled micropiles due to the soil compaction impacts. The average uniaxial compressive strength of the soil samples after the micropiles grouting was dependent on the applied grouting pressure and increased from 25% to 56%. In addition, the direct shear test results showed an increase of 15% in the soil cohesion and an increase of 4 degrees in the internal friction angle for the soil after the micropiles grouting.
{"title":"A Field Study on the Behavior of Driven and Drilling Micropiles Implemented in Clay","authors":"Alireza Heydari Abdollahi, A. Ghanbari","doi":"10.1680/jgeen.22.00006","DOIUrl":"https://doi.org/10.1680/jgeen.22.00006","url":null,"abstract":"Micropiles are often implemented through drilling, steel pipe installation, reinforcement, and grouting. However, in some parts of the world, especially in the areas with fine-grained soils, these shafts are implemented by steel pile driving, followed by reinforcement, and grouting has been expanded considerably. In this study, micropile shafts were installed at the site by both driving and drilling methods. Reinforcement and grouting were carried out by the two-step grouting and applying different grouting pressures in micropiles. Some boreholes (at a distance of 0.3 m from the micropile axis) and test pits were drilled to investigate the penetration radius of the grout at different grouting pressures. Results showed that the bearing capacity of driven micropiles is about 4% to 14% more than that of the drilled micropiles due to the soil compaction impacts. The average uniaxial compressive strength of the soil samples after the micropiles grouting was dependent on the applied grouting pressure and increased from 25% to 56%. In addition, the direct shear test results showed an increase of 15% in the soil cohesion and an increase of 4 degrees in the internal friction angle for the soil after the micropiles grouting.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"84540541","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}
This paper explores the efficacy of a pervious concrete pile (PCP) in accelerating the rate of consolidation in unconsolidated soft clay deposits. A series of laboratory consolidation tests were performed on the pervious concrete pile, sand drains, and stone columns in two different soft clay soils (CI & CH), and their consolidation characteristics were compared. A novel annular setup was utilized to determine the consolidation characteristics of all three techniques employed. An extensive enhancement in consolidation characteristics like the coefficient of compressibility and coefficient of consolidation was observed when PCP was employed compared to sand drains and stone columns. Enhancement in compression index for PCP implied a compelling scope for accelerating the radial consolidation from surrounding soil, which was lesser in the case of stone columns and comparatively lesser in the case of sand drains. The rate of consolidation in the radial direction was observed in both CI and CH soils when PCP was employed. Perhaps, acceleration in consolidation was predominant in CH soil rather than CI soil.
{"title":"Improved radial consolidation in soft clay using pervious concrete piles","authors":"Umanath Umaiyan, K. Muthukkumaran","doi":"10.1680/jgeen.22.00046","DOIUrl":"https://doi.org/10.1680/jgeen.22.00046","url":null,"abstract":"This paper explores the efficacy of a pervious concrete pile (PCP) in accelerating the rate of consolidation in unconsolidated soft clay deposits. A series of laboratory consolidation tests were performed on the pervious concrete pile, sand drains, and stone columns in two different soft clay soils (CI & CH), and their consolidation characteristics were compared. A novel annular setup was utilized to determine the consolidation characteristics of all three techniques employed. An extensive enhancement in consolidation characteristics like the coefficient of compressibility and coefficient of consolidation was observed when PCP was employed compared to sand drains and stone columns. Enhancement in compression index for PCP implied a compelling scope for accelerating the radial consolidation from surrounding soil, which was lesser in the case of stone columns and comparatively lesser in the case of sand drains. The rate of consolidation in the radial direction was observed in both CI and CH soils when PCP was employed. Perhaps, acceleration in consolidation was predominant in CH soil rather than CI soil.","PeriodicalId":54572,"journal":{"name":"Proceedings of the Institution of Civil Engineers-Geotechnical Engineering","volume":null,"pages":null},"PeriodicalIF":2.2,"publicationDate":"2022-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83422350","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：