This study used the finite element method (FEM) to analyze the stress field and seepage field of a roller-compacted concrete (RCC) dam, with an upstream impervious layer constructed with different types of concret...This study used the finite element method (FEM) to analyze the stress field and seepage field of a roller-compacted concrete (RCC) dam, with an upstream impervious layer constructed with different types of concrete materials, including three-graded RCC, two-graded RCC, conven- tional vibrated concrete (CVC), and grout-enriched vibrated RCC (GEVR), corresponding to the design schemes S 1 through $4. It also evaluated the anti-seepage performance of the imperious layer in the four design schemes under the normal water level and flood-check level. Stress field analysis of a retaining section and discharge section shows that the maximum tensile stress occurs near the dam heel, the maximum compressive stress occurs near the dam toe, and the stress distributions in the four schemes can satisfy the stress control criteria. Seepage field analysis shows that the uplift pressure heads in schemes S3 and S4 descend rapidly in the anti-seepage region, and that the calculated results of daily seepage flow under the steady seepage condition in these two schemes are about 30%-50% lower than those in the other two schemes, demonstrating that CVC and GEVR show better anti-seepage performance. The results provide essential parameters such as the uplift pressure head and seelga^e flow for physical model tests and anti-seepage structure selection in RCC dams.展开更多
According to the characteristics of thin-layer rolling and pouring construction technology and the complicated mechanical behavior of the roller compacted concrete dam(RCCD)construction interface,a constitutive model ...According to the characteristics of thin-layer rolling and pouring construction technology and the complicated mechanical behavior of the roller compacted concrete dam(RCCD)construction interface,a constitutive model of endochronic damage was established based on the endochronic theory and damage mechanics.The proposed model abandons the traditional concept of elastic-plastic yield surface and can better reflect the real behavior of rolled control concrete.Basic equations were proposed for the fluid solid coupling analysis,and the relationships among the corresponding key physical parameters were also put forward.One three-dimensional finite element method(FEM)program was obtained by studying the FEM type of the seepage-stress coupling intersection of the RCCD.The method was applied to an actual project,and the results show that the fluid solid interaction influences dam deformation and dam abutment stability,which is in accordance with practice.Therefore,this model provides a new method for revealing the mechanical behavior of RCCD under the coupling field.展开更多
To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring art...To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.展开更多
A scheme for identifying rolling layers in roller-compacted concrete (RCC) dam automatically was presented. First, a conceptual model was developed. Second, by using a computational geometry method, the auto identific...A scheme for identifying rolling layers in roller-compacted concrete (RCC) dam automatically was presented. First, a conceptual model was developed. Second, by using a computational geometry method, the auto identification of rolling layers and auto matching between rolling compaction machines and rolling layers were realized based on spatial control points. An application to the construction of Guandi RCC dam showed that the auto identification of rolling layers played an important role in ensuring the engineering quality.展开更多
The concept and realization process of intelligent compaction for the construction of high roller compacted concrete dam were presented,as well as the theory of monitoring and intelligent feedback control.Based on the...The concept and realization process of intelligent compaction for the construction of high roller compacted concrete dam were presented,as well as the theory of monitoring and intelligent feedback control.Based on the real-time analysis of the compaction index,a multiple regression model of the dam compactness was established and a real-time estimation method of compaction quality for the entire work area of roller compacted concrete dam was proposed finally.The adaptive adjustment of the rolling process parameters was achieved,with the speed,the exciting force,the roller pass and the compaction thickness meeting the standards during the whole construction process.As a result,the compaction quality and construction efficiency can be improved.The research provides a new way for the construction quality control of roller compacted concrete dam.展开更多
Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a maj...Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a major disadvantage as compared to environmental impact, that is, wildlife habitat disruption. In as much as it has become optimal for investment in hydropower dam construction, the scourge for dam failure is still eminent, which is as a result of excessive seepage compromising the integrity of the mechanical properties of the dam. The aim of the paper is to highlight successful application methods in joint bonding to avoid excessive seepage and reduce the autogenous healing to a few years of operation. In view of optimization, this paper presents a comprehensive study on the influences of interlayer joints bonding quality from RCC mix performances and how it consolidates the RCC layers to withstand the shear strength along the interface, especially on the high dams. The case study is the RCC dam at the 750 MW Kafue Gorge Lower Hydropower Station. The scope of the study reviews the joint type judged by Modified Maturity Factor (MMF) with joint surface long time exposed in regions with dry and high temperature, technical measures of layer bonding quality control under condition of long time joint surface exposure, effects of joints shear strength and impermeability of the RCC layers when under the conditions of plastic and elasticity. The subtle observations made during the dam construction phases were with respect to the optimal use of materials in relation to RCC mix designs and the basis for equipment calibration for monitoring important data that can be referenced during analysis of shear forces acting on the RCC dam over time.展开更多
By means of fracture testing on roller-compacted concrete (RCC) three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture t...By means of fracture testing on roller-compacted concrete (RCC) three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture theory, KiniⅠC,KunⅠC, as well as the critical effective crack length and the critical crack tip opening displacement, were evaluated. Based on the double-K fracture parameters above, the calculation model of equivalent strength for induced crack was established, thus the calculation method on its initiation, stable propagation and unstable fracture was ascertained. Moreover, the finite element simulation analysis of stress field in ShaPai arch dam and the on-site observational splaying points of induced crack at different altitudes validated the reliability of the model. Finally, crack inducer′s optimal setting in RCC arch dam was studied. It improves the design level of induced crack in RCC arch dam and satisfies the necessity of engineering practice.展开更多
The size effect rule of roller compacted concrete (RCC) fracture toughness was reached on the analysis of fracture toughness of RCC specimens, which have been done by project team. And then the rule was applied to the...The size effect rule of roller compacted concrete (RCC) fracture toughness was reached on the analysis of fracture toughness of RCC specimens, which have been done by project team. And then the rule was applied to the calculation formula of equivalent strength of crack director in the RCC arch dam, thus a simple and useful formula was reached. The study shows that the equivalent strength of crack directors increases with the increasing intensity of concrete, but the surplus rate of strength of crack directors section decreases with the increasing intensity of concrete and the distance between centers of adjacent crack directors, and that bilateral interval crack directors are more efficient in weakening the strength of section than unidirectional interval crack directors in the case of the same distance between adjacent crack director centers. A good design for crack directors of RCC arch dam is proposed via the rule.展开更多
基金supported by the National Basic Research Program of China(Grant No.2013CB035903)the National Natural Science Foundation of China(Grants No.51321065 and 51209159)
文摘This study used the finite element method (FEM) to analyze the stress field and seepage field of a roller-compacted concrete (RCC) dam, with an upstream impervious layer constructed with different types of concrete materials, including three-graded RCC, two-graded RCC, conven- tional vibrated concrete (CVC), and grout-enriched vibrated RCC (GEVR), corresponding to the design schemes S 1 through $4. It also evaluated the anti-seepage performance of the imperious layer in the four design schemes under the normal water level and flood-check level. Stress field analysis of a retaining section and discharge section shows that the maximum tensile stress occurs near the dam heel, the maximum compressive stress occurs near the dam toe, and the stress distributions in the four schemes can satisfy the stress control criteria. Seepage field analysis shows that the uplift pressure heads in schemes S3 and S4 descend rapidly in the anti-seepage region, and that the calculated results of daily seepage flow under the steady seepage condition in these two schemes are about 30%-50% lower than those in the other two schemes, demonstrating that CVC and GEVR show better anti-seepage performance. The results provide essential parameters such as the uplift pressure head and seelga^e flow for physical model tests and anti-seepage structure selection in RCC dams.
基金Projects(51139001,51179066,51079046,50909041) supported by the National Natural Science Foundation of ChinaProject(NCET-10-0359) supported by the Program for New Century Excellent Talents in UniversityProjects(2009586012,2009586912,2010585212)supported by the Special Fund of State Key Laboratory of China
文摘According to the characteristics of thin-layer rolling and pouring construction technology and the complicated mechanical behavior of the roller compacted concrete dam(RCCD)construction interface,a constitutive model of endochronic damage was established based on the endochronic theory and damage mechanics.The proposed model abandons the traditional concept of elastic-plastic yield surface and can better reflect the real behavior of rolled control concrete.Basic equations were proposed for the fluid solid coupling analysis,and the relationships among the corresponding key physical parameters were also put forward.One three-dimensional finite element method(FEM)program was obtained by studying the FEM type of the seepage-stress coupling intersection of the RCCD.The method was applied to an actual project,and the results show that the fluid solid interaction influences dam deformation and dam abutment stability,which is in accordance with practice.Therefore,this model provides a new method for revealing the mechanical behavior of RCCD under the coupling field.
基金Projects(20120094110005,20120094130003)supported by the Research Fund for the Doctoral Program of Higher Education of ChinaProjects(51379068,51139001,51279052,51209077,51179066)supported by the National Natural Science Foundation of China+1 种基金Project(NCET-11-0628)supported by the Program for New Century Excellent Talents in University,ChinaProjects(201201038,201101013)supported by the Public Welfare Industry Research Special Fund Project of Ministry of Water Resources of China
文摘To study the influence of construction interfaces on dynamic characteristics of roller compacted concrete dams(RCCDs),mechanical properties of construction interfaces are firstly analyzed. Then, the viscous-spring artificial boundary(VSAB) is adopted to simulate the radiation damping of their infinite foundations, and based on the Marc software, a simplified seismic motion input method is presented by the equivalent nodal loads. Finally, based on the practical engineering of a RCC gravity dam, effects of radiation damping and construction interfaces on the dynamic characteristics of dams are investigated in detail. Analysis results show that dynamic response of the RCC gravity dam significantly reduces about 25% when the radiation damping of infinite foundation is considered. Hot interfaces and the normal cold interfaces have little influence on the dynamic response of the RCC gravity dam.However, nonlinear fracture along the cold interfaces at the dam heel will occur under the designed earthquake if the cold interfaces are combined poorly. Therefore, to avoid the fractures along the construction interfaces under the potential super earthquakes,combination quality of the RCC layers should be significantly ensured.
基金Supported by Foundation for Innovative Research Groups of National Natural Science Foundation of China (No. 51021004)National Natural Science Foundation of China (No. 50879056)Key Project in the National Science and Technology Pillar Program during the Eleventh Five-Year Plan Period(No. 2008BAB29B05)
文摘A scheme for identifying rolling layers in roller-compacted concrete (RCC) dam automatically was presented. First, a conceptual model was developed. Second, by using a computational geometry method, the auto identification of rolling layers and auto matching between rolling compaction machines and rolling layers were realized based on spatial control points. An application to the construction of Guandi RCC dam showed that the auto identification of rolling layers played an important role in ensuring the engineering quality.
基金National Natural Science Foundation of China (No. 51021004No. 51079096)the Program for New Century Excellent Talents in University (No. NCET-08-0391)
文摘The concept and realization process of intelligent compaction for the construction of high roller compacted concrete dam were presented,as well as the theory of monitoring and intelligent feedback control.Based on the real-time analysis of the compaction index,a multiple regression model of the dam compactness was established and a real-time estimation method of compaction quality for the entire work area of roller compacted concrete dam was proposed finally.The adaptive adjustment of the rolling process parameters was achieved,with the speed,the exciting force,the roller pass and the compaction thickness meeting the standards during the whole construction process.As a result,the compaction quality and construction efficiency can be improved.The research provides a new way for the construction quality control of roller compacted concrete dam.
文摘Roller Compacted Concrete (RCC) has gained favorable recognition in hydropower and water resource dam construction. With optimization in construction technology and materials used for RCC Dams, cost is no longer a major disadvantage as compared to environmental impact, that is, wildlife habitat disruption. In as much as it has become optimal for investment in hydropower dam construction, the scourge for dam failure is still eminent, which is as a result of excessive seepage compromising the integrity of the mechanical properties of the dam. The aim of the paper is to highlight successful application methods in joint bonding to avoid excessive seepage and reduce the autogenous healing to a few years of operation. In view of optimization, this paper presents a comprehensive study on the influences of interlayer joints bonding quality from RCC mix performances and how it consolidates the RCC layers to withstand the shear strength along the interface, especially on the high dams. The case study is the RCC dam at the 750 MW Kafue Gorge Lower Hydropower Station. The scope of the study reviews the joint type judged by Modified Maturity Factor (MMF) with joint surface long time exposed in regions with dry and high temperature, technical measures of layer bonding quality control under condition of long time joint surface exposure, effects of joints shear strength and impermeability of the RCC layers when under the conditions of plastic and elasticity. The subtle observations made during the dam construction phases were with respect to the optimal use of materials in relation to RCC mix designs and the basis for equipment calibration for monitoring important data that can be referenced during analysis of shear forces acting on the RCC dam over time.
文摘By means of fracture testing on roller-compacted concrete (RCC) three-point bending beams with two different specimen sizes, the P-CMOD complete curve for RCC was gained. Furthermore, by applying double-K fracture theory, KiniⅠC,KunⅠC, as well as the critical effective crack length and the critical crack tip opening displacement, were evaluated. Based on the double-K fracture parameters above, the calculation model of equivalent strength for induced crack was established, thus the calculation method on its initiation, stable propagation and unstable fracture was ascertained. Moreover, the finite element simulation analysis of stress field in ShaPai arch dam and the on-site observational splaying points of induced crack at different altitudes validated the reliability of the model. Finally, crack inducer′s optimal setting in RCC arch dam was studied. It improves the design level of induced crack in RCC arch dam and satisfies the necessity of engineering practice.
基金Sponsored by the National Natural Science Foundation of China(Grant No.50179002,50709013)Liaoning Province Dr. Fund(Grant No.20071025)
文摘The size effect rule of roller compacted concrete (RCC) fracture toughness was reached on the analysis of fracture toughness of RCC specimens, which have been done by project team. And then the rule was applied to the calculation formula of equivalent strength of crack director in the RCC arch dam, thus a simple and useful formula was reached. The study shows that the equivalent strength of crack directors increases with the increasing intensity of concrete, but the surplus rate of strength of crack directors section decreases with the increasing intensity of concrete and the distance between centers of adjacent crack directors, and that bilateral interval crack directors are more efficient in weakening the strength of section than unidirectional interval crack directors in the case of the same distance between adjacent crack director centers. A good design for crack directors of RCC arch dam is proposed via the rule.