Based on the hypothesis of elastic two-layered foundation system under in-finite slab with known values of thicknesses of various layers and slab modulus,a programADMODE for evaluating foundation modulus is worked out...Based on the hypothesis of elastic two-layered foundation system under in-finite slab with known values of thicknesses of various layers and slab modulus,a programADMODE for evaluating foundation modulus is worked out by putting the inverse com-putation idea for moduli of various layers of foundation into an optimization problem.The validities of the theory and program have been checked and verified by taboratorytest.Besides,the foundation modulus have also been computed with this program by usingthe data obtained from Tai-Zhou experimental road.Through regression analyses,theempirical formulas for computing the increasing multiples of the moduli of subgrade andbase course are presented.展开更多
To investigate the validity of two dynamic modulus predictive models（ Witczak 1-37 A viscosity-based model and Witczak 1-40 D shear modulus-based model） in the context of Jiangsu, and evaluate the effect of differen...To investigate the validity of two dynamic modulus predictive models（ Witczak 1-37 A viscosity-based model and Witczak 1-40 D shear modulus-based model） in the context of Jiangsu, and evaluate the effect of different mixture design variables（ aggregate gradations, binder type, and volumetric properties） on dynamic modulus E＊, asphalt mixtures commonly used in the local surface layer, including Sup-13 and AC-13, are prepared in the laboratory and their dynamic modulus E＊values are predicted based on the above mentioned models. The corresponding asphalt tests, including viscosity and dynamic shear modulus tests, are also carried out to obtain the prediction model parameters. The test results showthat binder type and asphalt content have a significant impact on dynamic modulus.There is a good correlation between the E＊values based on above two predictive models and the measured E＊, while a relatively lower bias can be expected from Witczak 1-37 A model. The test results can be used for the calibration of dynamic modulus with higher accuracy.展开更多
In order to increase the applied efficiency of crushed rock base(CRB) in pavement structure design for Western Australia roads,the material modelling based on the experimental results was investigated,and the disturbe...In order to increase the applied efficiency of crushed rock base(CRB) in pavement structure design for Western Australia roads,the material modelling based on the experimental results was investigated,and the disturbed state concept(DSC) was used to predict the resilient modulus of CRB because of its simplicity and strong ability in capturing the elastic and inelastic responses of materials to loads.The actual deformation of DSC,at any loading state,was determined from its assumed relative intact(RI) state.The DSC equation of CRB was constructed by using a set of experimental results of resilient modulus tests,and an idealized material model,namely the linear elastic model,of relative intact(RI) part was considered.Analysis results reveal that the resilient modulus-applied stress relationships back-predicted by using the DSC modelling are consistent with the experimental results,so,the DSC equation is suited for predicting the resilient modulus of CRB specimen.However,the model and the equation coming from the test results are conducted in accordance with the Austroads standard,so further investigation and validation with respect to the field behaviours of pavement structure should be performed.展开更多
Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resil...Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resilient modulus values at only a specific stress state from DCP data, corresponding to the predefined thicknesses of pavement layers（a 50 mm asphalt wearing course, a 100 mm asphalt binder course and a200 mm aggregate base course）. In this study, field-measured DCP data were utilized to estimate the resilient modulus of low-plasticity subgrade Piedmont residual soil. Piedmont residual soils are in-place weathered soils from igneous and metamorphic rocks, as opposed to transported or compacted soils.Hence the existing empirical correlations might not be applicable for these soils. An experimental program was conducted incorporating field DCP and laboratory resilient modulus tests on "undisturbed" soil specimens. The DCP tests were carried out at various locations in four test sections to evaluate subgrade stiffness variation laterally and with depth. Laboratory resilient modulus test results were analyzed in the context of the mechanistic-empirical pavement design guide（MEPDG） recommended universal constitutive model. A new approach for predicting the resilient modulus from DCP by estimating MEPDG constitutive model coefficients（k;,k;and k;） was developed through statistical analyses. The new model is capable of not only taking into account the in situ soil condition on the basis of field measurements,but also representing the resilient modulus at any stress state which addresses a limitation with existing empirical DCP models and its applicability for a specific case. Validation of the model is demonstrated by using data that were not used for model development, as well as data reported in the literature.展开更多
In order to investigate the suction-dependent properties of subgrade granular material and its effect on pavement responses,coupled hydro-mechanical simulations were conducted in Abaqus.A suction-dependent resilient m...In order to investigate the suction-dependent properties of subgrade granular material and its effect on pavement responses,coupled hydro-mechanical simulations were conducted in Abaqus.A suction-dependent resilient modulus model was integrated into the commercial finite element(FE)code Abaqus by developing a user-defined material(UMAT)subroutine.The developed model was validated by triaxial test results under different suction conditions and good agreement was achieved.A three-dimensional(3D)FE pavement model was established and the suction-dependent properties of subgrade granular material was characterized by the developed constitutive model.Hydro-mechanical pavement responses subjected to three moisture states and the falling weight deflectometer(FWD)load were calculated.Simulation results reveal that the resilient modulus of subgrade granular material is sensitive to suction and stress states;high groundwater table decreases the overall resilient moduli of subgrade structure due to suction reduction,leading to the increase of the maximum surface deflection,the tensile strain at bottom of the surface layer,compressive strain on top of subgrade,and consequently,deterioration in pavement performance.展开更多
Repeated load triaxial tests were performed on five compacted gravel lateritic soils collected from different locations in Senegal: Sébikotane, Dougar, Pa Lo, Mont-Rolland and Ngoundiane. The study revealed that ...Repeated load triaxial tests were performed on five compacted gravel lateritic soils collected from different locations in Senegal: Sébikotane, Dougar, Pa Lo, Mont-Rolland and Ngoundiane. The study revealed that resilient modulus decreases with the increase of the bulk and deviatoric stress in constant confining pressure. In addition, resilient modulus increases with the percentage of cement for appreciably equal contents of moisture. This effect tends to stop for higher stress. Besides, correlations were made with some models of resilient modulus such as the Uzan-Witczack model (Witczack and Uzan, 1988 [1]) and the National Highway Research Program (NCHRP) model (2004 [2]). The study confirms that both models give very good results with the best correlations being obtained with the Uzan-Witczack model.展开更多
This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines...This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines content and the percentage of fractured coarse aggregates were identified as direct indicators of the resilient modulus susceptibility to changes in water content.The results showed that the percentage of fractured coarse aggregates particles(FR)has a more significant impact on the resilient modulus(Er)of crushed granular materials used in pavement construction than the combined indicator of the fines content and sample volumetrics(nf).Crushed granular materials with a higher percentage of fractured coarse aggregates are relatively insensitive to changes in the degree of saturation,but become more sensitive as the fine fraction porosity decreases.An adjusted model was proposed based on the existing formulation,but considers a complex parameter to describe and adjust the sensitivity of base granular materials to variations in moisture content with respect to fabrication charac-teristics,fines content and volumetric properties.The model shows that the variation of Er values is below10%for fully crushed granular materials.However,it reaches approximately±12%for materials with 75%of crushed coarse aggregates andþ40%and-25%for materials with FR=50%.This model could help select good ag-gregates characteristics and adjust grain-size distribution for environments where significant moisture content variations can occur in the pavement system,such as in the Province of Quebec(Canada).As it is based on pa-rameters that can be easily determined or estimated,it also represents a valuable tool for detailed design and analysis that can consider material characteristics.展开更多
The property of reclaimed asphalt pavement（RAP） mixture will be affected mainly by composition of old asphalt/soil and cement content in CIR system. We studied the relationship between A/S and cementitious materials...The property of reclaimed asphalt pavement（RAP） mixture will be affected mainly by composition of old asphalt/soil and cement content in CIR system. We studied the relationship between A/S and cementitious materials. It showed that if there was no soil in RAP, the unconfined compressive strength was only from 0.18 MPa to 1.07 MPa even if adding cement was from 2% to 6%, and RAP samples collapsed during conserving in water. The optimum water content rose from 6.5% to 11% with the declining of A/S from S=0 to A/S=1/5. Five RAP samples all got the maximum compressive strength when A/S=5/5, and the maximum compressive strength of the samples adding 6% cement was 3.17 MPa. It showed that the capacity of RAP was not only affected by A/S, but also by the content of cement. The dynamic modulus of RAP will increase with the rise of loading frequency and decrease with the temperature rising. SEM test showed that C-S-H interlacing formed the netted structure, and it enwrapped the aggregate and improved the strength of RAP.展开更多
In order to investigate the stress-dependent properties of hot-mix asphalt （HMA）,a dynamic modulus test was conducted on a group of AC-20 specimens at various stress states and loading frequencies,respectively.A use...In order to investigate the stress-dependent properties of hot-mix asphalt （HMA）,a dynamic modulus test was conducted on a group of AC-20 specimens at various stress states and loading frequencies,respectively.A user-defined material （UMAT ）subroutine incorporating stress-dependent constitutive model was developed and finite element （FE）simulation was utilized to confirm the validity of the UMAT.A three-dimensional （3D ）FE model for typical pavement structure was established,considering the HMA layer as a stress-dependent material and other layers as linear elastic materials.Periodic load was applied to the pavement model and the pavement responses were calculated,including dynamic modulus distributions,surface deflection,shear stress and tensile strain in the HMA layer,etc.Both test results and FE model predictions indicate that the dynamic modulus of asphalt concrete is sensitive to stress state and loading frequency.Using the nonlinear stress-dependent model results in greater predicted pavement responses compared with the linear elastic model.It is also found that the effects of stress-dependency on pavement responses become more significant as loading frequency decreases.展开更多
Rubblization technique has been extensively used to repair the damaged concrete pavement and has proven successful in developed countries like the US and Europe. It has not been fully adopted in developing region like...Rubblization technique has been extensively used to repair the damaged concrete pavement and has proven successful in developed countries like the US and Europe. It has not been fully adopted in developing region like the Middle East and this paper presents the design and construction challenges posed while assessing damaged concrete runway in empty quarter of Saudi Arabia. <span style="font-family:Verdana;">A number of design options for repairs for runway pavement were consi</span><span style="font-family:Verdana;">dered and rubblization was chosen as a preferred option for repair. This paper includes the consideration for the assessment and adoption of the concrete rubblized modulus value using the falling weight deflectometer, optimization </span><span style="font-family:Verdana;">of the tests for the whole runway using the Heavy Weight Deflectometer</span><span style="font-family:Verdana;"> HWD testing to replace pits, safely working around the utilities, reasonable assumption of drop height of the pavement and installation of utility conduits in the rubblized layer. Findings of the paper demonstrates resolving</span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">technical issues which are not very well covered in the Federal Aviation Authority (FAA) EB-66 such as the additional test strips, minimum areas of rubblization for assessment using test pits, drop in the height of concrete surface and fixing of utilities in rubblized pavement. The case study demonstrates that the rubblization can be successfully carried out in remote locations like empty quarter of Saudi Arabia with carefully carried out detailed site investigations, adopt</span><span style="font-family:Verdana;">ing correct assumed design rubblization modulus, quality control using </span><span style="font-family:Verdana;">HWD, protection of utilities while rubblizing and use of polymer modified asphalt for successful project deployment.</span></span></span></span>展开更多
文摘Based on the hypothesis of elastic two-layered foundation system under in-finite slab with known values of thicknesses of various layers and slab modulus,a programADMODE for evaluating foundation modulus is worked out by putting the inverse com-putation idea for moduli of various layers of foundation into an optimization problem.The validities of the theory and program have been checked and verified by taboratorytest.Besides,the foundation modulus have also been computed with this program by usingthe data obtained from Tai-Zhou experimental road.Through regression analyses,theempirical formulas for computing the increasing multiples of the moduli of subgrade andbase course are presented.
基金The Specialized Research Fund for the Doctoral Program of Higher Education of China(No.20120092110053)
文摘To investigate the validity of two dynamic modulus predictive models（ Witczak 1-37 A viscosity-based model and Witczak 1-40 D shear modulus-based model） in the context of Jiangsu, and evaluate the effect of different mixture design variables（ aggregate gradations, binder type, and volumetric properties） on dynamic modulus E＊, asphalt mixtures commonly used in the local surface layer, including Sup-13 and AC-13, are prepared in the laboratory and their dynamic modulus E＊values are predicted based on the above mentioned models. The corresponding asphalt tests, including viscosity and dynamic shear modulus tests, are also carried out to obtain the prediction model parameters. The test results showthat binder type and asphalt content have a significant impact on dynamic modulus.There is a good correlation between the E＊values based on above two predictive models and the measured E＊, while a relatively lower bias can be expected from Witczak 1-37 A model. The test results can be used for the calibration of dynamic modulus with higher accuracy.
基金Curtin International Postgraduate Research Scholarship(CIPRS)Human Resource Development Scholarship of Kasetsart University
文摘In order to increase the applied efficiency of crushed rock base(CRB) in pavement structure design for Western Australia roads,the material modelling based on the experimental results was investigated,and the disturbed state concept(DSC) was used to predict the resilient modulus of CRB because of its simplicity and strong ability in capturing the elastic and inelastic responses of materials to loads.The actual deformation of DSC,at any loading state,was determined from its assumed relative intact(RI) state.The DSC equation of CRB was constructed by using a set of experimental results of resilient modulus tests,and an idealized material model,namely the linear elastic model,of relative intact(RI) part was considered.Analysis results reveal that the resilient modulus-applied stress relationships back-predicted by using the DSC modelling are consistent with the experimental results,so,the DSC equation is suited for predicting the resilient modulus of CRB specimen.However,the model and the equation coming from the test results are conducted in accordance with the Austroads standard,so further investigation and validation with respect to the field behaviours of pavement structure should be performed.
文摘Dynamic cone penetrometer（DCP） has been used for decades to estimate the shear strength and stiffness properties of the subgrade soils. There are several empirical correlations in the literature to predict the resilient modulus values at only a specific stress state from DCP data, corresponding to the predefined thicknesses of pavement layers（a 50 mm asphalt wearing course, a 100 mm asphalt binder course and a200 mm aggregate base course）. In this study, field-measured DCP data were utilized to estimate the resilient modulus of low-plasticity subgrade Piedmont residual soil. Piedmont residual soils are in-place weathered soils from igneous and metamorphic rocks, as opposed to transported or compacted soils.Hence the existing empirical correlations might not be applicable for these soils. An experimental program was conducted incorporating field DCP and laboratory resilient modulus tests on "undisturbed" soil specimens. The DCP tests were carried out at various locations in four test sections to evaluate subgrade stiffness variation laterally and with depth. Laboratory resilient modulus test results were analyzed in the context of the mechanistic-empirical pavement design guide（MEPDG） recommended universal constitutive model. A new approach for predicting the resilient modulus from DCP by estimating MEPDG constitutive model coefficients（k;,k;and k;） was developed through statistical analyses. The new model is capable of not only taking into account the in situ soil condition on the basis of field measurements,but also representing the resilient modulus at any stress state which addresses a limitation with existing empirical DCP models and its applicability for a specific case. Validation of the model is demonstrated by using data that were not used for model development, as well as data reported in the literature.
基金The Science and Technology Project of China Communications Construction(No.2015-ZJKJ-26)
文摘In order to investigate the suction-dependent properties of subgrade granular material and its effect on pavement responses,coupled hydro-mechanical simulations were conducted in Abaqus.A suction-dependent resilient modulus model was integrated into the commercial finite element(FE)code Abaqus by developing a user-defined material(UMAT)subroutine.The developed model was validated by triaxial test results under different suction conditions and good agreement was achieved.A three-dimensional(3D)FE pavement model was established and the suction-dependent properties of subgrade granular material was characterized by the developed constitutive model.Hydro-mechanical pavement responses subjected to three moisture states and the falling weight deflectometer(FWD)load were calculated.Simulation results reveal that the resilient modulus of subgrade granular material is sensitive to suction and stress states;high groundwater table decreases the overall resilient moduli of subgrade structure due to suction reduction,leading to the increase of the maximum surface deflection,the tensile strain at bottom of the surface layer,compressive strain on top of subgrade,and consequently,deterioration in pavement performance.
文摘Repeated load triaxial tests were performed on five compacted gravel lateritic soils collected from different locations in Senegal: Sébikotane, Dougar, Pa Lo, Mont-Rolland and Ngoundiane. The study revealed that resilient modulus decreases with the increase of the bulk and deviatoric stress in constant confining pressure. In addition, resilient modulus increases with the percentage of cement for appreciably equal contents of moisture. This effect tends to stop for higher stress. Besides, correlations were made with some models of resilient modulus such as the Uzan-Witczack model (Witczack and Uzan, 1988 [1]) and the National Highway Research Program (NCHRP) model (2004 [2]). The study confirms that both models give very good results with the best correlations being obtained with the Uzan-Witczack model.
文摘This study aims to quantify the susceptibility of granular materials used in pavements to changes in moisture content and propose a correlation model to incorporate this susceptibility into seasonal analyses.The fines content and the percentage of fractured coarse aggregates were identified as direct indicators of the resilient modulus susceptibility to changes in water content.The results showed that the percentage of fractured coarse aggregates particles(FR)has a more significant impact on the resilient modulus(Er)of crushed granular materials used in pavement construction than the combined indicator of the fines content and sample volumetrics(nf).Crushed granular materials with a higher percentage of fractured coarse aggregates are relatively insensitive to changes in the degree of saturation,but become more sensitive as the fine fraction porosity decreases.An adjusted model was proposed based on the existing formulation,but considers a complex parameter to describe and adjust the sensitivity of base granular materials to variations in moisture content with respect to fabrication charac-teristics,fines content and volumetric properties.The model shows that the variation of Er values is below10%for fully crushed granular materials.However,it reaches approximately±12%for materials with 75%of crushed coarse aggregates andþ40%and-25%for materials with FR=50%.This model could help select good ag-gregates characteristics and adjust grain-size distribution for environments where significant moisture content variations can occur in the pavement system,such as in the Province of Quebec(Canada).As it is based on pa-rameters that can be easily determined or estimated,it also represents a valuable tool for detailed design and analysis that can consider material characteristics.
基金Funded by the National High-tech Research and Development Program of China ('863' Program) (2009AA11Z106)
文摘The property of reclaimed asphalt pavement（RAP） mixture will be affected mainly by composition of old asphalt/soil and cement content in CIR system. We studied the relationship between A/S and cementitious materials. It showed that if there was no soil in RAP, the unconfined compressive strength was only from 0.18 MPa to 1.07 MPa even if adding cement was from 2% to 6%, and RAP samples collapsed during conserving in water. The optimum water content rose from 6.5% to 11% with the declining of A/S from S=0 to A/S=1/5. Five RAP samples all got the maximum compressive strength when A/S=5/5, and the maximum compressive strength of the samples adding 6% cement was 3.17 MPa. It showed that the capacity of RAP was not only affected by A/S, but also by the content of cement. The dynamic modulus of RAP will increase with the rise of loading frequency and decrease with the temperature rising. SEM test showed that C-S-H interlacing formed the netted structure, and it enwrapped the aggregate and improved the strength of RAP.
基金Jiangsu Provincial Transportation Science and Technology Project(No.2011Y02-1-G1)
文摘In order to investigate the stress-dependent properties of hot-mix asphalt （HMA）,a dynamic modulus test was conducted on a group of AC-20 specimens at various stress states and loading frequencies,respectively.A user-defined material （UMAT ）subroutine incorporating stress-dependent constitutive model was developed and finite element （FE）simulation was utilized to confirm the validity of the UMAT.A three-dimensional （3D ）FE model for typical pavement structure was established,considering the HMA layer as a stress-dependent material and other layers as linear elastic materials.Periodic load was applied to the pavement model and the pavement responses were calculated,including dynamic modulus distributions,surface deflection,shear stress and tensile strain in the HMA layer,etc.Both test results and FE model predictions indicate that the dynamic modulus of asphalt concrete is sensitive to stress state and loading frequency.Using the nonlinear stress-dependent model results in greater predicted pavement responses compared with the linear elastic model.It is also found that the effects of stress-dependency on pavement responses become more significant as loading frequency decreases.
文摘Rubblization technique has been extensively used to repair the damaged concrete pavement and has proven successful in developed countries like the US and Europe. It has not been fully adopted in developing region like the Middle East and this paper presents the design and construction challenges posed while assessing damaged concrete runway in empty quarter of Saudi Arabia. <span style="font-family:Verdana;">A number of design options for repairs for runway pavement were consi</span><span style="font-family:Verdana;">dered and rubblization was chosen as a preferred option for repair. This paper includes the consideration for the assessment and adoption of the concrete rubblized modulus value using the falling weight deflectometer, optimization </span><span style="font-family:Verdana;">of the tests for the whole runway using the Heavy Weight Deflectometer</span><span style="font-family:Verdana;"> HWD testing to replace pits, safely working around the utilities, reasonable assumption of drop height of the pavement and installation of utility conduits in the rubblized layer. Findings of the paper demonstrates resolving</span><span><span><span style="font-family:;" "=""> </span></span></span><span><span><span style="font-family:;" "=""><span style="font-family:Verdana;">technical issues which are not very well covered in the Federal Aviation Authority (FAA) EB-66 such as the additional test strips, minimum areas of rubblization for assessment using test pits, drop in the height of concrete surface and fixing of utilities in rubblized pavement. The case study demonstrates that the rubblization can be successfully carried out in remote locations like empty quarter of Saudi Arabia with carefully carried out detailed site investigations, adopt</span><span style="font-family:Verdana;">ing correct assumed design rubblization modulus, quality control using </span><span style="font-family:Verdana;">HWD, protection of utilities while rubblizing and use of polymer modified asphalt for successful project deployment.</span></span></span></span>
