Albert Atterberg introduced various consistency limits (state transitions) for fine-grained soil in the 1910s. Of these, the liquid limit (LL) and plastic limit (PL) are ubiquitous in geotechnical engineering practice, including their usage for soil classification purposes and in deducing useful geotechnical parameters via correlations. Given it is about 120 years since first introduced, it seems timely to critically review the current state of play regarding various definitions and theory of these index parameters and their standardised testing methods, as described in majorly used codes worldwide. Because different codes allow different LL apparatus types and employ some dissimilar criteria (e.g., in establishing the end-point for the PL test), a change in method or code may produce different results for testing the same soil. These differences are rationalised in terms of the controlling parameter(s). Some potential pitfalls in consistency limits testing are highlighted. Attention then turn to strength-based approaches, mostly employing fall cone (FC) setups, emphasising their unsuitability for determining Atterberg’s PL. Considering the PL test’s general poor reproducibility, the paper concludes with an alternative way forward, obtaining useful FC index parameters that provide new possibilities for strength predictions and in the classification of fine-grained soils.
{"title":"Theory of liquid and plastic limits for fine soils, methods of determination and outlook","authors":"B. O’Kelly","doi":"10.1680/jgere.23.00038","DOIUrl":"https://doi.org/10.1680/jgere.23.00038","url":null,"abstract":"Albert Atterberg introduced various consistency limits (state transitions) for fine-grained soil in the 1910s. Of these, the liquid limit (LL) and plastic limit (PL) are ubiquitous in geotechnical engineering practice, including their usage for soil classification purposes and in deducing useful geotechnical parameters via correlations. Given it is about 120 years since first introduced, it seems timely to critically review the current state of play regarding various definitions and theory of these index parameters and their standardised testing methods, as described in majorly used codes worldwide. Because different codes allow different LL apparatus types and employ some dissimilar criteria (e.g., in establishing the end-point for the PL test), a change in method or code may produce different results for testing the same soil. These differences are rationalised in terms of the controlling parameter(s). Some potential pitfalls in consistency limits testing are highlighted. Attention then turn to strength-based approaches, mostly employing fall cone (FC) setups, emphasising their unsuitability for determining Atterberg’s PL. Considering the PL test’s general poor reproducibility, the paper concludes with an alternative way forward, obtaining useful FC index parameters that provide new possibilities for strength predictions and in the classification of fine-grained soils.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":"6 1","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-12-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"138602010","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}
High-precision visualized 3D slope modeling and stability analysis have benefited from the quick development of big data technology. The research aims to utilize unmanned aerial vehicle survey data to obtain influencing information on slope topography. A high-precision three-dimensional surface model is established, which is then overlaid with three-dimensional geological models and three-dimensional mineral models constructed using Geographic Information System technology. This approach enables more efficient and accurate three-dimensional visualization modeling of slopes. Based on the 3D model, the search for the most dangerous sliding surface under the rainfall conditions is completed. The average absolute error of sample points in the surface modeling effect verification experiment is less than 0.5 m and the average relative error is less than 2%. These results indicate that the overall modeling effect of 3D slope model can meet the requirements of subsequent stability analysis. According to the results of random simulation, the minimum safety factor on the most neutral surfaces is less than 1, which indicates that the slopes at some locations in this site do have the possibility of landslide. The neutral surface where the least safety factor appears can be used to pinpoint the position of the most hazardous sliding surface.
{"title":"Slope visualization and stability study using GIS technology and UAV","authors":"Xianghui Jian","doi":"10.1680/jgere.23.00030","DOIUrl":"https://doi.org/10.1680/jgere.23.00030","url":null,"abstract":"High-precision visualized 3D slope modeling and stability analysis have benefited from the quick development of big data technology. The research aims to utilize unmanned aerial vehicle survey data to obtain influencing information on slope topography. A high-precision three-dimensional surface model is established, which is then overlaid with three-dimensional geological models and three-dimensional mineral models constructed using Geographic Information System technology. This approach enables more efficient and accurate three-dimensional visualization modeling of slopes. Based on the 3D model, the search for the most dangerous sliding surface under the rainfall conditions is completed. The average absolute error of sample points in the surface modeling effect verification experiment is less than 0.5 m and the average relative error is less than 2%. These results indicate that the overall modeling effect of 3D slope model can meet the requirements of subsequent stability analysis. According to the results of random simulation, the minimum safety factor on the most neutral surfaces is less than 1, which indicates that the slopes at some locations in this site do have the possibility of landslide. The neutral surface where the least safety factor appears can be used to pinpoint the position of the most hazardous sliding surface.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"136263451","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}
The Harbor Bay Isle residential project in Alameda, California comprises some 600 acres reclaimed from the margin of San Francisco Bay underlain by very soft (Cc ∼ 1), high water-content clay (e0 >2): San Francisco Bay Mud. Settlements of as much as 2.5 m developed from about 7 m (varying across the site) of sandfill surcharge, with records over some 43 years extending through primary consolidation and into secondary (creep). Iterative numerical modelling using large-strain theory (implemented in Excel), constrained by insitu void ratios and oedometer trends, achieved close matches to settlement histories over the full 43 years for the three locations considered each of which displayed a markedly different history from the others. The presence or absence of a dried ‘crust’ was found unimportant; instead, the proportion of sub-units within the Bay Mud controlled the evolution of settlements. Sub-units within Bay Mud, evident in modern CPTu soundings (which were not available during the reclamation works), exist across the region and have systematically different states and properties. Further, while ageing is a factor, depositional conditions of the Bay Mud have produced a residual fabric that presents as a component of the pre-consolidation pressure.
位于美国加利福尼亚州阿拉米达的港湾湾岛住宅项目包括从旧金山湾边缘回收的约600英亩(243公顷)土地，下面是非常软的(C C ~ 1)，高含水量粘土(e 0 >2):旧金山湾泥。从约7米(不同地点不同)的沙土堆积物发展到多达2.5米的沉降，在大约43年的记录中，从初级固结延伸到次级固结(蠕变)。使用大应变理论(在Microsoft Excel软件程序中实现)的迭代数值模拟，在原地空隙率和土壤测量趋势的约束下，获得了与所考虑的三个地点在整整43年的沉降历史的密切匹配，每个地点都显示出明显不同的历史。干“皮”的存在与否被认为不重要;相反，海湾泥内亚单元的比例控制了聚落的演变。湾泥中的亚单元，在现代锥贯贯测试中很明显(在填海工程期间无法获得)，存在于整个地区，具有系统不同的状态和性质。此外，虽然老化是一个因素，但海湾泥的沉积条件产生了残余结构，作为预固结压力的一个组成部分。
{"title":"Retrospective evaluation of large settlement of a very soft clay","authors":"Curtis Jensen, Michael Jefferies","doi":"10.1680/jgere.23.00022","DOIUrl":"https://doi.org/10.1680/jgere.23.00022","url":null,"abstract":"The Harbor Bay Isle residential project in Alameda, California comprises some 600 acres reclaimed from the margin of San Francisco Bay underlain by very soft (Cc ∼ 1), high water-content clay (e0 >2): San Francisco Bay Mud. Settlements of as much as 2.5 m developed from about 7 m (varying across the site) of sandfill surcharge, with records over some 43 years extending through primary consolidation and into secondary (creep). Iterative numerical modelling using large-strain theory (implemented in Excel), constrained by insitu void ratios and oedometer trends, achieved close matches to settlement histories over the full 43 years for the three locations considered each of which displayed a markedly different history from the others. The presence or absence of a dried ‘crust’ was found unimportant; instead, the proportion of sub-units within the Bay Mud controlled the evolution of settlements. Sub-units within Bay Mud, evident in modern CPTu soundings (which were not available during the reclamation works), exist across the region and have systematically different states and properties. Further, while ageing is a factor, depositional conditions of the Bay Mud have produced a residual fabric that presents as a component of the pre-consolidation pressure.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":"55 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135943975","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}
Hadi Moghadam Joybari, Mobin Afzali Rad, Hanieh Hosseinzadeh, Naveen B P.
In the construction of civil structures, the strength of the foundation is of high importance, so engineers face many challenges such as bearing capacity, settlement, high groundwater level, etc., especially if the structure is on sandy soil. In order to deal with these problems, solutions have been proposed, one of which is the use of skirted foundations. In this method, walls skirt the surface foundation and are buried deep in the soil, which are called skirted foundations. In this study, using numerical Analysis, taking into account the parameters of different lengths of skirted foundation walls, different percentages of soil densities and wall thickness, have been investigated under static load. On the basis of the obtained results, a series of charts are presented to estimate bearing capacity improvement, Skirted foundations resting on sand are dense more beneficial than those resting on medium and loose sand.
{"title":"Numerical modeling of skirt foundation under vertical load","authors":"Hadi Moghadam Joybari, Mobin Afzali Rad, Hanieh Hosseinzadeh, Naveen B P.","doi":"10.1680/jgere.23.00005","DOIUrl":"https://doi.org/10.1680/jgere.23.00005","url":null,"abstract":"In the construction of civil structures, the strength of the foundation is of high importance, so engineers face many challenges such as bearing capacity, settlement, high groundwater level, etc., especially if the structure is on sandy soil. In order to deal with these problems, solutions have been proposed, one of which is the use of skirted foundations. In this method, walls skirt the surface foundation and are buried deep in the soil, which are called skirted foundations. In this study, using numerical Analysis, taking into account the parameters of different lengths of skirted foundation walls, different percentages of soil densities and wall thickness, have been investigated under static load. On the basis of the obtained results, a series of charts are presented to estimate bearing capacity improvement, Skirted foundations resting on sand are dense more beneficial than those resting on medium and loose sand.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":"48 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-10-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"135830505","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}
In recent times, geopolymer has gained attention as a soil stabilization binder due to its ability to improve soil’s engineering properties while remaining eco-friendly. This study seeks to investigate the stabilization of soft soil using palm oil fuel ash (POFA)-based geopolymers. The geopolymer was created by combining POFA with an alkaline activator solution composed of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The mechanical and microstructural behaviour of two clayey soil types stabilized with four doses of POFA-based geopolymer (G10PA, G20PA, G30PA, G40PA) was studied by conducting one-dimensional consolidation, California Bearing Ratio (CBR), Field Emission Scanning Electron Microscopy (FESEM), and X-Ray Diffraction (XRD) tests. The optimum dosage found was G40PA in both soil samples. The CBR value of S1-G40PA was 1.7 times the S1 while S2-G40PA was nearly 1.5 times the S2. The void ratio of S1 was significantly reduced from 0.70 (untreated sample) to 0.56 (S2-G40PA), whereas for S2, it was decreased from 1.43 (untreated sample) to 0.43 (S2-G40PA). The microstructural analysis (FESEM) revealed that changes in material composition correlate to consolidation behaviour, with the geopolymer gel-binding effect enhancing the mechanical properties of stabilized soils.
{"title":"Consolidation and microstructural behaviour of soil treated with palm oil fuel ash-based geopolymer","authors":"I. Khasib, N. Daud, MohammadAli Izadifar","doi":"10.1680/jgere.23.00013","DOIUrl":"https://doi.org/10.1680/jgere.23.00013","url":null,"abstract":"In recent times, geopolymer has gained attention as a soil stabilization binder due to its ability to improve soil’s engineering properties while remaining eco-friendly. This study seeks to investigate the stabilization of soft soil using palm oil fuel ash (POFA)-based geopolymers. The geopolymer was created by combining POFA with an alkaline activator solution composed of sodium hydroxide (NaOH) and sodium silicate (Na2SiO3). The mechanical and microstructural behaviour of two clayey soil types stabilized with four doses of POFA-based geopolymer (G10PA, G20PA, G30PA, G40PA) was studied by conducting one-dimensional consolidation, California Bearing Ratio (CBR), Field Emission Scanning Electron Microscopy (FESEM), and X-Ray Diffraction (XRD) tests. The optimum dosage found was G40PA in both soil samples. The CBR value of S1-G40PA was 1.7 times the S1 while S2-G40PA was nearly 1.5 times the S2. The void ratio of S1 was significantly reduced from 0.70 (untreated sample) to 0.56 (S2-G40PA), whereas for S2, it was decreased from 1.43 (untreated sample) to 0.43 (S2-G40PA). The microstructural analysis (FESEM) revealed that changes in material composition correlate to consolidation behaviour, with the geopolymer gel-binding effect enhancing the mechanical properties of stabilized soils.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-07-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44995758","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}
Pub Date : 2023-06-01DOI: 10.1680/jgere.2023.10.2.49
D. E. L. Ong, Md Mizanur Rahman
{"title":"Editorial","authors":"D. E. L. Ong, Md Mizanur Rahman","doi":"10.1680/jgere.2023.10.2.49","DOIUrl":"https://doi.org/10.1680/jgere.2023.10.2.49","url":null,"abstract":"","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45849810","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}
Five sewage sludge specimens with different organic contents were prepared by mixing mass ratio 0%, 5%, 10%, 20% and 40% of dry soil powder into raw sewage sludge. The addition of dry soil powder can reduce the organic content of sewage sludge without significantly changing its particle composition. Oedometer tests were conducted, starting from a small effective vertical stress σ v′ = 3 kPa. It is observed that the e-logσ v′ compression curves show an inverse ‘S’ shape due to suction pressure resisting deformation. The suction pressure decreases exponentially with the organic content, a regressed equation for which has been provided. Burland’s concept of intrinsic compression line (ICL) is adopted for correlating the compression curves of sludgewith various organic contents. It is found that the ICL with high organic content lies above the low one, that is, the higher the organic content, the greater the void index. In addition, the shape of the ICL for organic sludges is an inverse ‘S’ rather than slightly concave upwards for inorganic reconstituted clays. An average ICL is provided to normalize the compression curves of sludges with different organic contents. The intrinsic compression parameters e * 100 and C c * can be correlated with the organic content, which increase linearly with the organic content, and the regressed equations for them were provided.
将质量比为0%、5%、10%、20%、40%的干土粉掺入原污泥中，制备5个不同有机含量的污泥样品。添加干土粉可以在不显著改变污泥颗粒组成的情况下降低污泥的有机含量。从小的有效垂直应力σ v′= 3 kPa开始，进行了电测试验。观察到，由于吸力抗压变形，e-logσ v '压缩曲线呈倒“S”形。吸力压力随有机质含量呈指数递减，并给出了其回归方程。采用伯兰(Burland)的内在压缩线(ICL)概念，将污泥的压缩曲线与不同有机物含量相关联。结果表明，有机含量高的ICL位于有机含量低的ICL之上，即有机含量越高，孔隙指数越大。此外，有机污泥的ICL形状是一个反“S”，而无机重构粘土的ICL形状是微凹向上的。给出了一个平均ICL，用于对不同有机含量污泥的压缩曲线进行归一化。本征压缩参数e * 100和C C *与有机质含量呈线性关系，并给出了其回归方程。
{"title":"Effects of organic content on sewage sludge compression behaviour","authors":"Ruixing Yang, Ren-wei Wei, Zhen-ning Zhang, Teng-long Zheng","doi":"10.1680/jgere.23.00004","DOIUrl":"https://doi.org/10.1680/jgere.23.00004","url":null,"abstract":"Five sewage sludge specimens with different organic contents were prepared by mixing mass ratio 0%, 5%, 10%, 20% and 40% of dry soil powder into raw sewage sludge. The addition of dry soil powder can reduce the organic content of sewage sludge without significantly changing its particle composition. Oedometer tests were conducted, starting from a small effective vertical stress σ v′ = 3 kPa. It is observed that the e-logσ v′ compression curves show an inverse ‘S’ shape due to suction pressure resisting deformation. The suction pressure decreases exponentially with the organic content, a regressed equation for which has been provided. Burland’s concept of intrinsic compression line (ICL) is adopted for correlating the compression curves of sludgewith various organic contents. It is found that the ICL with high organic content lies above the low one, that is, the higher the organic content, the greater the void index. In addition, the shape of the ICL for organic sludges is an inverse ‘S’ rather than slightly concave upwards for inorganic reconstituted clays. An average ICL is provided to normalize the compression curves of sludges with different organic contents. The intrinsic compression parameters e * 100 and C c * can be correlated with the organic content, which increase linearly with the organic content, and the regressed equations for them were provided.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-05-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44311328","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}
Johan Lagerlund, J. Laue, P. Viklander, Erik Nordström
Embankment dams can be damaged by internal erosion, which ultimately leads to a failure. When internal erosion occurs, finer soil particles from the core soil are washed out. To restore the function of the core, injection grouting can be undertaken. Grouting the core of an embankment dam should be performed with a grout material with characteristics similar to the core soil, such as a low-mobility grout. This type of grout material has similarities to a fine-grained moraine core soil given its stiffness, but it has difficulties permeating the damaged core soil. A modified low-mobility grout material containing gravel, sand, limestone filler, bentonite, plasticizer, air release agent, and water has been tested in the laboratory with focus on permeation. Injection was done on different-sized aggregates. The impact of paste-to-aggregate ratio, grout consistency, maximum grain size of grout material, particle size distribution of injected material, and injection method was tested. Higher paste-to-aggregate ratios, lower viscosity and lower yield strength of the grout material improved the permeation.
{"title":"Testing of a modified low-mobility grout material for permeation grouting in embankment dams","authors":"Johan Lagerlund, J. Laue, P. Viklander, Erik Nordström","doi":"10.1680/jgere.22.00066","DOIUrl":"https://doi.org/10.1680/jgere.22.00066","url":null,"abstract":"Embankment dams can be damaged by internal erosion, which ultimately leads to a failure. When internal erosion occurs, finer soil particles from the core soil are washed out. To restore the function of the core, injection grouting can be undertaken. Grouting the core of an embankment dam should be performed with a grout material with characteristics similar to the core soil, such as a low-mobility grout. This type of grout material has similarities to a fine-grained moraine core soil given its stiffness, but it has difficulties permeating the damaged core soil. A modified low-mobility grout material containing gravel, sand, limestone filler, bentonite, plasticizer, air release agent, and water has been tested in the laboratory with focus on permeation. Injection was done on different-sized aggregates. The impact of paste-to-aggregate ratio, grout consistency, maximum grain size of grout material, particle size distribution of injected material, and injection method was tested. Higher paste-to-aggregate ratios, lower viscosity and lower yield strength of the grout material improved the permeation.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-05-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43234706","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}
It is sometimes convenient to treat a relatively rigid footing as a single element subjected to up to six force-resultants: vertical load, horizontal load in two directions, overturning moment about two axes, and torsion. Applications include calculations of initial, elastic settlement; foundation responses under seismic loading or for machine vibrations; and fixity of an offshore jackup foundation under cyclic wave loading. Present codes of practice provide formulae that assume fully isotropic and linear elastic soil, and in some case assume no friction between footing and soil. This paper uses recent theoretical advances to develop solutions for stiffnesses of rigid circular footings on transversely isotropic linear elastic soil, including with interface friction. Closed form solutions are developed for vertical load and overturning moment on a frictionless interface, and for vertical load and torsion on a frictional interface. A boundary element analysis is presented for the cases of lateral load and overturning moment on a frictional interface. By fitting expected forms to the results, new formulae are proposed for stiffnesses for these cases. Effects of interface friction on limiting loads are calculated. Practical applications are outlined, and some limitations are briefly discussed.
{"title":"Rigid circular footing on the surface of a transversely isotropic linear elastic half-space","authors":"E. Dean","doi":"10.1680/jgere.22.00064","DOIUrl":"https://doi.org/10.1680/jgere.22.00064","url":null,"abstract":"It is sometimes convenient to treat a relatively rigid footing as a single element subjected to up to six force-resultants: vertical load, horizontal load in two directions, overturning moment about two axes, and torsion. Applications include calculations of initial, elastic settlement; foundation responses under seismic loading or for machine vibrations; and fixity of an offshore jackup foundation under cyclic wave loading. Present codes of practice provide formulae that assume fully isotropic and linear elastic soil, and in some case assume no friction between footing and soil. This paper uses recent theoretical advances to develop solutions for stiffnesses of rigid circular footings on transversely isotropic linear elastic soil, including with interface friction. Closed form solutions are developed for vertical load and overturning moment on a frictionless interface, and for vertical load and torsion on a frictional interface. A boundary element analysis is presented for the cases of lateral load and overturning moment on a frictional interface. By fitting expected forms to the results, new formulae are proposed for stiffnesses for these cases. Effects of interface friction on limiting loads are calculated. Practical applications are outlined, and some limitations are briefly discussed.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49534203","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}
General solutions for the displacements, strains, and changes of stress in a transversely isotropic, linear elastic (TILE) half-space subject to a point load were published in 1998. They represent a massive advance on the 19th century solutions by Boussinesq, Cerruti and others which were for fully isotropic, linear elastic (FILE) half-spaces. The 1998 solutions were for loads at a general depth below the surface, and were criticized for being difficult. The present paper deduces more accessible expressions for the special case of loads are on the surface. This allows one clarification and one potential error in the original equations to be identified and avoided. With support from existing data of geological materials, agreement is found with a previous claim that a limit proposed in 1970 on one of the shear moduli for a TILE material is invalid. Corrected equations derived herein can be the basis of calculating ground stresses and movements due to linear responses to distributed surface loads, behaviours of flexible foundations, and stiffnesses for rigid surface footings.
{"title":"Point loads on the surface of a transversely isotropic linear elastic half-space","authors":"E. Dean","doi":"10.1680/jgere.22.00063","DOIUrl":"https://doi.org/10.1680/jgere.22.00063","url":null,"abstract":"General solutions for the displacements, strains, and changes of stress in a transversely isotropic, linear elastic (TILE) half-space subject to a point load were published in 1998. They represent a massive advance on the 19th century solutions by Boussinesq, Cerruti and others which were for fully isotropic, linear elastic (FILE) half-spaces. The 1998 solutions were for loads at a general depth below the surface, and were criticized for being difficult. The present paper deduces more accessible expressions for the special case of loads are on the surface. This allows one clarification and one potential error in the original equations to be identified and avoided. With support from existing data of geological materials, agreement is found with a previous claim that a limit proposed in 1970 on one of the shear moduli for a TILE material is invalid. Corrected equations derived herein can be the basis of calculating ground stresses and movements due to linear responses to distributed surface loads, behaviours of flexible foundations, and stiffnesses for rigid surface footings.","PeriodicalId":44054,"journal":{"name":"Geotechnical Research","volume":" ","pages":""},"PeriodicalIF":1.9,"publicationDate":"2023-03-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44500310","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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