A commonly used approach to evaluating the potential for internal instability in soils is that of Kenney and Lau. This method involves a shape analysis of the grain size curve over a length of the soil’s finer part. ...A commonly used approach to evaluating the potential for internal instability in soils is that of Kenney and Lau. This method involves a shape analysis of the grain size curve over a length of the soil’s finer part. A soil that is internally unstable has a particle size distribution with a finer fraction less than the coarser fraction;therefore, the coarser fraction makes up the primary fabric of the material. Thus, the fine-grained particles are loose (non-structural) in between fixed (structural) coarser grains, and these loose fine particles are permitted to migrate through the constrictions of the fabric of the coarser fraction. This paper discusses the evolution of the Kenney-Lau method and its boundary relations, and furthermore, a discussion on adaptations of the method, which touches on field experience and engineering practice, is given.展开更多
This paper presents a database of glacial till gradations that are compiled from laboratory internal stability tests from the literature and from core soils of existing dams, some of which have experienced internal er...This paper presents a database of glacial till gradations that are compiled from laboratory internal stability tests from the literature and from core soils of existing dams, some of which have experienced internal erosion. The potential internal instability of these gradations is assessed using empirical methods. Two approaches of evaluation are used: the Kenney-Lau method, which analyzes the shape of the gradation curve;and the Burenkova method, which uses factors of uniformity of the slope of the gradation. Although they include some uncertainties in terms of soils with fines, these methods, which are primarily developed from laboratory studies of sand and gravels, are used in engineering practice to evaluate widely graded soils that include fines, such as glacial tills. This study evaluates the glacial till gradations of the database using these approaches and discusses their applicability and relative predictive success. This study indicates that both the Kenney-Lau method and the Burenkova method have merit, but a closer analysis indicates that the Kenney-Lau approach has relatively better predictive ability based on the glacial till gradations analyzed in this study.展开更多
If the core of an embankment dam is damaged by internal erosion,it can be remediated by injection grouting.The grout material should not be allowed to harden,but rather become a natural part of the core after injectio...If the core of an embankment dam is damaged by internal erosion,it can be remediated by injection grouting.The grout material should not be allowed to harden,but rather become a natural part of the core after injection,exhibiting similar geotechnical characteristics as the core.However,the grout material must be pumpable during the injection.A new type of non-hardening grout material made for embankment dams has therefore been developed and tested.The grout material is made from natural,rounded sand and gravel aggregates,limestone filler,water,superplasticizer,air release agent,and bentonite powder.Since no hardening materials are included in the grout material,such as cement,the hardening of the grout material after injection relies on the effect of the superplasticizer to wear off.Test results show that this type of grout material is possible to pump and inject,eventually becoming part of the original core.Due to its tendency to absorb air,the grout material should not be homogenized longer than 15 minutes.After 34 days of storage,the undrained shear strength of the grout material was~13 kPa,and its bulk density and water content had similar values expected in a core.展开更多
基金part of the“Swedish Hydropower Centre-SVC”financial support has also been received from WSP Sweden
文摘A commonly used approach to evaluating the potential for internal instability in soils is that of Kenney and Lau. This method involves a shape analysis of the grain size curve over a length of the soil’s finer part. A soil that is internally unstable has a particle size distribution with a finer fraction less than the coarser fraction;therefore, the coarser fraction makes up the primary fabric of the material. Thus, the fine-grained particles are loose (non-structural) in between fixed (structural) coarser grains, and these loose fine particles are permitted to migrate through the constrictions of the fabric of the coarser fraction. This paper discusses the evolution of the Kenney-Lau method and its boundary relations, and furthermore, a discussion on adaptations of the method, which touches on field experience and engineering practice, is given.
基金part of the“Swedish Hydropower Centre-SVC”the financial support received from WSP Sweden
文摘This paper presents a database of glacial till gradations that are compiled from laboratory internal stability tests from the literature and from core soils of existing dams, some of which have experienced internal erosion. The potential internal instability of these gradations is assessed using empirical methods. Two approaches of evaluation are used: the Kenney-Lau method, which analyzes the shape of the gradation curve;and the Burenkova method, which uses factors of uniformity of the slope of the gradation. Although they include some uncertainties in terms of soils with fines, these methods, which are primarily developed from laboratory studies of sand and gravels, are used in engineering practice to evaluate widely graded soils that include fines, such as glacial tills. This study evaluates the glacial till gradations of the database using these approaches and discusses their applicability and relative predictive success. This study indicates that both the Kenney-Lau method and the Burenkova method have merit, but a closer analysis indicates that the Kenney-Lau approach has relatively better predictive ability based on the glacial till gradations analyzed in this study.
文摘If the core of an embankment dam is damaged by internal erosion,it can be remediated by injection grouting.The grout material should not be allowed to harden,but rather become a natural part of the core after injection,exhibiting similar geotechnical characteristics as the core.However,the grout material must be pumpable during the injection.A new type of non-hardening grout material made for embankment dams has therefore been developed and tested.The grout material is made from natural,rounded sand and gravel aggregates,limestone filler,water,superplasticizer,air release agent,and bentonite powder.Since no hardening materials are included in the grout material,such as cement,the hardening of the grout material after injection relies on the effect of the superplasticizer to wear off.Test results show that this type of grout material is possible to pump and inject,eventually becoming part of the original core.Due to its tendency to absorb air,the grout material should not be homogenized longer than 15 minutes.After 34 days of storage,the undrained shear strength of the grout material was~13 kPa,and its bulk density and water content had similar values expected in a core.
