Evaluation of subgrade strength and flexible pavement designs for reliability nayan saha follow this and additional works at. Design pamphlet for the determination of design subgrade in support of the 1993 aashto guide for the design of pavement structures publication no. Under average conditions the concrete should achieve a. It estimates the support of the layers below a rigid pavement surface course the pcc slab. Designs free fulltext estimation of resilient modulus. Cbr or modulus value, for the combination of a capping layer and a semiinfinite subgrade. A value used in rigid pavement design determined by. A 24,000lb axle load with a wheel spacing of 6 ft is. Featured software all software latest this just in old school emulation msdos games historical software classic pc games software library. Pdf effect of subgrade properties on pavement performance. It can be used to evaluate undisturbed soil andor compacted, unbound layers within existing pavements. This geotechnical special publication contains 10 papers on timely and important issues related to characterization of pavement subgrade and unbound materials using new analytical and experimental techniques. Historically, numerous techniques have been applied by a multitude of jurisdictions dealing with roadway pavements.
Proceedings of sessions of geodenver 2000, held in denver, colorado, august 58, 2000. Aci the modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabsonground. Pavement subgrade, unbound materials, and nondestructive testing. Joint transportation research program jtrp fhwainjtrp982 finalreport partii designsubgraderesilientmodulus implementationofsubgrade resilientmodulusforpavement designandevaluation a. Interruption, delay and discomfort in transportation flow that characterize roads across the globe due to poor pavement conditions are pathetic experiences.
W 18 total accumulated flexible esals for pavement design period predicted number of 18,000 lb. Estimating stiffness of subgrade and unbound materials for pavement design explores the significance of the resilient modulus property, various methods of determining this property of subsoils and unbound bases, and the application of this parameter in the mechanistic. For cohesive subgrades, a minimum of 95 % of aashto t 180, method d density modified compaction. This may be attributed to the decrease in the subgrade soil modulus due to increasing. The effective modulus of the pavement structure is determined by mr and deflection at the center of loading area. Pavement subgrade, unbound materials, and nondestructive. The resilient modulus is typically estimated in the laboratory using a repeated load cyclic triaxial test, which is complex and time consuming to perform. Sensitivity analysis of modulus of subgrade reaction. Resilient modulus development of aggregate base and subbase containing recycled bituminous and concrete for 2002 design guide and mnpave pavement design 7. Subgrade resilient modulus prediction using lightweight.
Characterization of subgrade soil mixed with recycled asphalt. Full text of subgrade resilient modulus for pavement. Estimating stiffness of subgrade and unbound materials for. Calculate the effective modulus of subgrade reaction k per table 3. A 24,000lb axle load with a wheel spacing of 6 ft is applied at the joint, with one wheel 6 from the edge, as shown in figure 3. For cohesive soils, it is shown that this requires that laboratory values be based on tests conducted unconfined using a deviator stress of 6 psi. Nov 09, 2015 astm d 6951 describes the dcp apparatus and test methodology. Pdf models to estimate k subgrade reaction modulus. The resilient subgrade modulus value is estimated using cbr values in the absence of vigorous laboratory tests. Resilient modulus development of aggregate base and. Concrete pavement design,construction, andperformance.
Selection of subgrade modulus for pavement overlay design. Hence, the modulus of subgrade reaction, which is the function of soil settlement and the external pressure,is used for flexible foundation design. Subgrade resilient modulus for pavement design and. Resilient modulus has been used for characterizing the stressstrain behavior of subgrade soils subjected to traffic loadings. Cimento portland, is regularly used and accepted for rigid pavement design.
Nddot implementation of aashto flexible pavement design. All activities, except the verification, are forwarded to the district engineer for concurrence. The name of this manual is the pavement design manual pdm. Influence of moisture content and climate change on subgrade soil resilient modulus davies, obafemi, andrew g heydinger, prof. Jan 09, 2008 pavement design and materials is a practical reference for both students and practicing engineers that explores all the aspects of pavement engineering, including materials, analysis, design, evaluation, and economic analysis. Since the mode of failure in the design of concrete pavement is flexural fatigue, it is important that the concrete have adequate flexural strength modulus of rupture to resist cracking from flexural fatigue. The subgrade modulus for pave ments designed by the aashto guide for design of pavement structures must be consistent with this value for the guide to be used correctly. The applied load in test and the water content in the subgrade should be representative of the work state of subgrade in the future pavement structure. The modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabsonground. Base and subgrade layers must provide adequate and moisture resistant strength that meets the design modulus, in. Thus, a new formula form is developed in this book, as shown in eq.
An empirical analysis of flexible pavement design can be done with or with out a soil strength test. Estimating stiffness of subgrade and unbound materials for pavement design. Selection of subgrade modulus for aashto flexible pavement design. A slab on ground and pavements normally are designed to be supported by a solid subbase, which needs to be uniform by nature to support the structure above it. Astm d 6951 describes the dcp apparatus and test methodology. Estimating stiffness of subgrade and unbound materials for pavement design explores the significance of the resilient modulus property, various methods of determining this property of subsoils and unbound bases, and the application of this parameter in the mechanisticempirical pavement design guide. Bowles equation 120xqa give me the subgrade modulus value is about 22pci which is very less then as suggested above 50 pci so which value is best approach to design this raftmat footing on grade. The subgrade modulus for pave ments designed by the aashto guide for design of pavement. These stresses are compared to those assumed values used in the initial iteration. Influence of spatial variation in subgrade properties on the integrity of highway pavement design is the burden of this research. This study evaluates the modulus of subgrade considering the. The values of e bs from the base layers in the original aasho road test are summarized in table 540. Use of nonlinear subgrade modulus in aashto design procedure.
It is a required input in the aashto method of flexible pavement design. In the structural design, one of the parameters is the value of modulus of reaction k from the subgrade or subbasesubgrade system, which is conventionally determined through. The most common and probably the safest answer to the question of correlation between bearing capacity and the modulus of subgrade reaction is that there is no correlation. The overall strength and performance of a pavement is dependent not only upon its design including both mix design and structural design but also on the loadbearing capacity of the subgrade soil. The resilient modulus of subgrade soils is a required input parameter for the aashto method of flexible pavement design and is also used to compute the modulus of subgrade reaction for the aashto rigid pavement design equations. Implementation of subgrade resilient modulus for pavement 2. Selection of subgrade modulus for aashto flexible pavement.
Design resilient modulus of subgrade soils from fwd tests. Subgrade preparation for new pavements pavement interactive. According to the chinese specifications of asphalt pavement design for highway, 6 the. Correlation between modulus of subgrade reaction and dcp. This work is an attempt to investigate the influence of subgrade variation on the design thicknesses of. As a result, we felt that the time was right for recapturing the pavement engineering state of the art in a textbook. The effects of variations in subgrade resilient modulus on various design parameters. Under average conditions the concrete should achieve a 28day modulus of rupture mr of 550 to 700 psi 3. Design pamphlet for the determination of design subgrade in.
Adjustments are made and iterations continue until the values used to predict subgrade modulus reasonably match the calculated stresses in the pavement system. With the recent release of the me design guide, highway agencies are. Design pamphlet for the determination of design subgrade. All subgrade and unbound pavement layers for all pavement types are characterized using m r in the nchrp 7a design methodology. Resilient modulus m r of subgrade is a very important factor in the pavement design and evaluation process.
The effects of variations in subgrade resilient modulus on various design parameters and on the aashto design thickness are examined. Trbs national cooperative highway research program nchrp synthesis 382. The use of the borrow material does not affect the design thickness of the pavement structure. The most recent model, recommended by the mechanisticempirical pavement design guide mepdg and used in this paper, calculates resilient modulus as a function of bulk stress, octahedral shear stress, and three fitting coefficients. Water under pavement is one of the primary causes of pavement failure. It is recommended that this design value be used to calculate pavement thickness requirements for all pavement types under consideration for the project. Selection of subgrade modulus for aashto flexible pavement design robert p.
Concrete pavement design, political userdefined subgrade. The final iterated value for resilient modulus is the design resilient modulus. Subgrade and pavement engineering fourth editionchinese. Improved consideration of the influence of subgrade and unbound layers on pavement performance get this book. Alternatively our books are available from all good bookshops. For the design of new construction pavement structures, the subgrade resilient modulus is estimated using an existing representative roadway. Concrete pavement design, political userdefined subgrade material. Pavement design and materials is a practical reference for both students and practicing engineers that explores all the aspects of pavement engineering, including materials, analysis, design, evaluation, and economic analysis. Subgrade and pavement engineering fourth editionchinese edition. Pdf characterization of subgrade soil mixed with recycled. Characterization of subgrade soil mixed with recycled.
Note that m r is the principal material input parameter for designing asphalt pavement using the recent mechanisticempirical pavement design software. Modulus of subgrade reaction k and kc k is the modulus of the subgrade soil. Aashto pavement design guide 1993 suggested a theoretical relationship between modulus of subgrade reaction and resilient modulus of subgrade based on the assumption that the. Joint transportation research program jtrp fhwainjtrp982 finalreport partii designsubgraderesilientmodulus implementationofsubgrade resilientmodulusforpavement designandevaluation. The resilient modulus of subgrade soils is a required input parameter for the aashto method of flexible pavement design and is also used to compute the modulus of subgrade reaction for. Accordingly, we can use dcp testing to estimate the subgrade resilient modulus for new pavement design and base course and subgrade moduli for rehabilitation design. Barrett during the design life of a project there are five activities completed by pavement design. Elliott the resilient modulus value 3,000 psi used to represent the aasho road test subgrade in the aashto flexible pavement design equation is examined. Evaluation of subgrade strength and flexible pavement designs. Mechanistic pavement design predicts pavement failure due to. For price availability and ordering visit our website. Nov 06, 2016 influence of spatial variation in subgrade properties on the integrity of highway pavement design is the burden of this research.
Influence of spatial variation in subgrade properties on. Implementation of subgrade resilient modulus for pavement. Subgrade resilient modulus for pavement design and evaluation. Department of transportation federal highway administration research and development turnerfairbank highway research center 6300 georgetown pike mclean, va 221012296. As a first step of the current study, different percentages of rap and. Rigid pavement thickness design systems investigated during this study were the 1986 aashto, american concrete. Subgrade resilient modulus in psi design input factors.
A subbase will go on top of the subgrade, which typically is native soil or improved soil that has been compacted. Sep 11, 2014 subgrade and pavement engineering fourth editionchinese edition huang xiao ming on. This study investigates the effect of rap on the resilient modulus m r of subgrade soils mixed with rap materials. Estimating stiffness of subgrade and unbound materials for pavement design explores the significance of the resilient modulus property, various methods of determining this property of subsoils and unbound bases, and the application of this parameter in the mechanisticempirical pavement design guidepublishers. Pavement performance can be largely attributed to the care given in designing and preparing its foundation, which is comprised of the subgrade and base layers. Modulus of subgrade reaction which one should be used. Influence of spatial variation in subgrade properties on the. I need to know if there is a correlation, a formula or any method to determine the modulus of subgrade reaction using the dcp index or cbr values. Correlation between modulus of subgrade reaction and dcp or. Subgrade and pavement engineering fourth editionchinese edition huang xiao ming on. Note that the e bs values are not only functions of moisture, but also of stress state. The resilient modulus represents the subgrade soil stiffness, and it is considered one of the key material inputs in the mechanistic empirical pavement design guide mepdg. This is a subgrade modulus method with nonlinear depth dependent.
Clough february1998 indiana department oftransportation purdue. The modulus of subgrade reaction k is used as a primary input for rigid pavement design. Since pavement life and surface deflection are strongly related, resilient modulus is a fundamental and rational material property that needs to be included in pavement design. Geotechnical aspects of pavements fhwa us department of. Structure magazine correlation between soil bearing.
Annual book of astm standards, section 4 construction, volume 04. Thus, anything that can be done to increase the loadbearing capacity or structural support of the subgrade soil will most likely improve the. The subgrade resilient modulus mr is backcalculated by measuring the deflection far from the loading area. The modulus of the unbound base materials depends on the stress state ie, on the subgrade modulus and the thickness of base course. The pavement response model for rigid pavement design, however, is based on a winklerspring foundation model that requires a value for the modulus of subgrade reaction k dynamic see appendix d for more details on. Base and subgrade layers must provide adequate and moisture resistant strength that meets the design modulus, in addition to durability and stability. Technical ability is also required to prepare the test specimens. There is no direct laboratory procedure for determining kvalue.
1268 821 820 108 975 835 1180 447 185 1149 463 961 1465 1032 807 838 1216 1353 1310 1301 37 46 583 695 1224 540 1189 1464 882 796 1161 621 997 201 194 75 237 1388 723 179 931 546