Long-term deformations of rockfill dams can be related to the type of dam,the pre-compaction achieved during the construction of the dam,the history of loading events,the rheological properties of the rockfill materia...Long-term deformations of rockfill dams can be related to the type of dam,the pre-compaction achieved during the construction of the dam,the history of loading events,the rheological properties of the rockfill material used,the seepage behavior caused by defects of the sealing,the interactions of the dam building with the foundation,and the hydrothermal phenomena of the stressed rockfill material.The present paper investigates the theological propcrtics of coarse grained rockfill materials using a hypoplastic constitutive model.Particular attention is paid to wetting deformation under different deviatoric loading states and pre-compactions.To quantify the state of weathering a so-called“solid hardness”is used in the sense of a continuum description.It is shown that an appropriate modeling of wetting deformations requires a unified description of the interaction at least between the state of weathering,the stress state,the density and the rate of deformation.The results obtained from the numerical simulations are compared with available experimental data for a rockfill material used in Xiaolangdi earth dam.展开更多
While modem prestressed techniques have improved the torsion properties of high-strength concrete （HSC） composite beams with prestressed steel （PS） boxes, no research has been reported in either the national or in...While modem prestressed techniques have improved the torsion properties of high-strength concrete （HSC） composite beams with prestressed steel （PS） boxes, no research has been reported in either the national or international literature on the an- ti-torque and composite torque properties of this type of beam. With the aim of understanding the torque properties of these beams, this paper presents results of ten comprehensive tests; three of these were based on stirrup spacings and prestressing levels as the main parameters, while the other seven were based on torsional rates. The torsion tests were conducted on the re- sults which established several key parameters, including curves of constant torsion, strain curves of steel torsion, strain distri- bution of steel beams and concrete, curves of bending-moment and mid-span deflection, as well as cross strain distribution.The prestressing impact-factor method was adopted to deduce semiempirical equations for cracking torque in such composite beams. Furthermore, this involves the use of the equation of ultimate torque based on tress-model-theory of the distortion an- gle, the calculated results show good agreement with the measured values. In summary, this paper offers theoretical analysis for future applications of HSC composite beams with PS boxes, and provides both validation of the methods employed and a reference point for on-going research on composite beams and related anti-torque studies.展开更多
A simplified in situ direct shear test （DST） was developed for measuring the shear strength of soils in fields. In this test, a latticed sheafing frame replaces the upper half of the shear box used in the convention...A simplified in situ direct shear test （DST） was developed for measuring the shear strength of soils in fields. In this test, a latticed sheafing frame replaces the upper half of the shear box used in the conventional direct shear box test. The latticed shearing frame is directly embedded in the ground to be tested after a construction process and is pulled with a flexible chain while a constant dead load is applied to the sample in the sheafing frame. This simplified in situ DST has been validated by comparing its results with those of triaxial tests on samples with parallel gradations under normal stresses less than 100 kPa. In this study, the DST was further validated by carrying out tests on samples with the same gradations, rather than on samples with parallel gradations, under normal stresses up to 880 kPa. In addition, the DST was performed inside fills in two applications.展开更多
To explore the microscopic responses of granular materials to wetting,the inter-particle lubrication effect and particle breakage in an odometer were simulated using a two-dimensional discrete element method.The lubri...To explore the microscopic responses of granular materials to wetting,the inter-particle lubrication effect and particle breakage in an odometer were simulated using a two-dimensional discrete element method.The lubrication effect was modeled by reduction of the inter-particle friction coefficient and particle breakage was initiated by decreasing the particle strength.Once the strength of the particles decreased to a threshold value,the particles began to break so that new contacts could be established to transfer the external loads.Numerical simulations successfully reproduced the additional compaction of the material and the intensification of the horizontal stress in addition to the microscopic responses of the granular assemblies.The microscopic interpretation of the earth pressure coefficient at rest and the evolution of the grain number distribution during particle breaking were also investigated.展开更多
Geopolymer is a material with high early strength.However,the insufficient durability properties,such as long-term strength,acid-base resistance,freeze-thaw resistance,leaching toxicity,thermal stability,sulfate resis...Geopolymer is a material with high early strength.However,the insufficient durability properties,such as long-term strength,acid-base resistance,freeze-thaw resistance,leaching toxicity,thermal stability,sulfate resistance and carbonation resistance,restrain its practical application.Herein,a longterm stable geopolymer composite with high final strength(ASK1)was synthesized from shell coal gasification fly ash(SFA)and steel slag(SS).Additionally,a geopolymer composite with high early strength(ASK2)was also synthesized for comparison.The results showed that ASK1 exhibited better performance on freezing-thawing resistance,carbonization resistance and heavy metals stabilization compared to the ASK2 at long-term curing.Raising the curing temperature could accelerate the unconfined compressive strength(UCS)development at initial curing ages of 3 to 7 d.Both ASK1 and ASK2 exhibited excellent acid-base and sulfate corrosion resistance.An increase for UCS was seen under KOH solution and MgSO_(4)solution corrosion for ASK1.All leaching concentrations of heavy metals out of the two geopolymers were below the standard threshold,even after 50 freezingthawing cycles.Both ASK1 and ASK2 geopolymer concrete exhibited higher sustainability and economic efficiency than Portland cement concrete.The result of this study not only provides a suitable way for the utilization of industrial solid waste in civil and environmental engineering,but also opens a new approach to improve the long-term stabilities of the geopolymers.展开更多
基金This work was partially supported by the National Natural Science Foundation of China(Grant No.51179059)the Fund for Young Scientists in Nanjing Hydraulic Research Institute。
文摘Long-term deformations of rockfill dams can be related to the type of dam,the pre-compaction achieved during the construction of the dam,the history of loading events,the rheological properties of the rockfill material used,the seepage behavior caused by defects of the sealing,the interactions of the dam building with the foundation,and the hydrothermal phenomena of the stressed rockfill material.The present paper investigates the theological propcrtics of coarse grained rockfill materials using a hypoplastic constitutive model.Particular attention is paid to wetting deformation under different deviatoric loading states and pre-compactions.To quantify the state of weathering a so-called“solid hardness”is used in the sense of a continuum description.It is shown that an appropriate modeling of wetting deformations requires a unified description of the interaction at least between the state of weathering,the stress state,the density and the rate of deformation.The results obtained from the numerical simulations are compared with available experimental data for a rockfill material used in Xiaolangdi earth dam.
基金supported by the National Natural Science Foundation of China (Grant No. 50879048)"948" Project of the Ministry of Water Resources of China (Grant No. 201127)
文摘While modem prestressed techniques have improved the torsion properties of high-strength concrete （HSC） composite beams with prestressed steel （PS） boxes, no research has been reported in either the national or international literature on the an- ti-torque and composite torque properties of this type of beam. With the aim of understanding the torque properties of these beams, this paper presents results of ten comprehensive tests; three of these were based on stirrup spacings and prestressing levels as the main parameters, while the other seven were based on torsional rates. The torsion tests were conducted on the re- sults which established several key parameters, including curves of constant torsion, strain curves of steel torsion, strain distri- bution of steel beams and concrete, curves of bending-moment and mid-span deflection, as well as cross strain distribution.The prestressing impact-factor method was adopted to deduce semiempirical equations for cracking torque in such composite beams. Furthermore, this involves the use of the equation of ultimate torque based on tress-model-theory of the distortion an- gle, the calculated results show good agreement with the measured values. In summary, this paper offers theoretical analysis for future applications of HSC composite beams with PS boxes, and provides both validation of the methods employed and a reference point for on-going research on composite beams and related anti-torque studies.
基金supported by the Special Foundation of the State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University (Grant No. 2009586012)
文摘A simplified in situ direct shear test （DST） was developed for measuring the shear strength of soils in fields. In this test, a latticed sheafing frame replaces the upper half of the shear box used in the conventional direct shear box test. The latticed shearing frame is directly embedded in the ground to be tested after a construction process and is pulled with a flexible chain while a constant dead load is applied to the sample in the sheafing frame. This simplified in situ DST has been validated by comparing its results with those of triaxial tests on samples with parallel gradations under normal stresses less than 100 kPa. In this study, the DST was further validated by carrying out tests on samples with the same gradations, rather than on samples with parallel gradations, under normal stresses up to 880 kPa. In addition, the DST was performed inside fills in two applications.
基金supported by the National Natural Science Foundation of China (51179059)the Innovation Plan for Postgraduate Students Sponsored by the Education Department of Jiangsu Province, China (CX08B_107Z)
文摘To explore the microscopic responses of granular materials to wetting,the inter-particle lubrication effect and particle breakage in an odometer were simulated using a two-dimensional discrete element method.The lubrication effect was modeled by reduction of the inter-particle friction coefficient and particle breakage was initiated by decreasing the particle strength.Once the strength of the particles decreased to a threshold value,the particles began to break so that new contacts could be established to transfer the external loads.Numerical simulations successfully reproduced the additional compaction of the material and the intensification of the horizontal stress in addition to the microscopic responses of the granular assemblies.The microscopic interpretation of the earth pressure coefficient at rest and the evolution of the grain number distribution during particle breaking were also investigated.
基金funded by the Jiangxi Academy of Water Science and Engineering Open Project Fund(No.2021SKSG04)the National Natural Science Foundation of China(No.51979011)+1 种基金the Central Non-Profit Scientific Research Fund for Institutes(Nos.CKSF2021483/CL,CKSF2023359/HL,and CKSF2023397/HL)the Knowledge Innovation Program of Science and Technology Bureau of Wuhan,China(No.CKSD2022360/CL)。
文摘Geopolymer is a material with high early strength.However,the insufficient durability properties,such as long-term strength,acid-base resistance,freeze-thaw resistance,leaching toxicity,thermal stability,sulfate resistance and carbonation resistance,restrain its practical application.Herein,a longterm stable geopolymer composite with high final strength(ASK1)was synthesized from shell coal gasification fly ash(SFA)and steel slag(SS).Additionally,a geopolymer composite with high early strength(ASK2)was also synthesized for comparison.The results showed that ASK1 exhibited better performance on freezing-thawing resistance,carbonization resistance and heavy metals stabilization compared to the ASK2 at long-term curing.Raising the curing temperature could accelerate the unconfined compressive strength(UCS)development at initial curing ages of 3 to 7 d.Both ASK1 and ASK2 exhibited excellent acid-base and sulfate corrosion resistance.An increase for UCS was seen under KOH solution and MgSO_(4)solution corrosion for ASK1.All leaching concentrations of heavy metals out of the two geopolymers were below the standard threshold,even after 50 freezingthawing cycles.Both ASK1 and ASK2 geopolymer concrete exhibited higher sustainability and economic efficiency than Portland cement concrete.The result of this study not only provides a suitable way for the utilization of industrial solid waste in civil and environmental engineering,but also opens a new approach to improve the long-term stabilities of the geopolymers.
