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. Pdf models to estimate k subgrade reaction modulus values. Aasho road test subgrade in the aashto flexible pavement design equation is examined. Subgrade resilient modulus for pavement design and. And one of the major functions of a highway pavement is to reduce the.
Structure magazine correlation between soil bearing. Subgrade characterization plays a key role in the thickness design of airport pavements. The effects of variations in subgrade resilient modulus on various design parameters and on the aashto design thickness are examined. Clough february1998 indiana department oftransportation purdue. Me pavement design guide, the darwinme help files, and njdot research reports. Pdf correlation between subgrade reaction modulus and. 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. Ugpti selection of subgrade modulus for the revised. Rdgn042 pavement design for carriageway construction page 3 of 42 design charts page chart 1 bituminous pavement e subgrade 50mpa 34 chart 2 bituminous pavement e subgrade 100mpa 35 chart 3 bituminous pavement e subgrade 150mpa 36 chart 4 bituminous pavement e subgrade 200mpa 37 chart 5 bituminous pavement e subgrade 250mpa 38.
Figure 4 shows the required capping thickness according to the japan equation to achieve a design effective cbr of 3% for a semiinfinite subgrade cbr of 1% to 3. The american petroleum institute api code prescribes a methodology known as py method, which is widely used for design of offshore piles. Resilient modulus has been used for characterizing the stressstrain behavior of subgrade soils subjected to traffic loadings. Until now, the information available to help engineers choose. This procedure is calibrated to provide the worst case scenario for the foundation behavior under static. An example of design without soil strength test is by using hrb soil classification system, in which soils are grouped from a1 to a7 and a group index is. 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 structural design of concrete pavements according to aashto and pca methods makes use of modulus of reaction k from the subgrade and subbase subgrade system as parameter to calculate slab.
Implementation of subgrade resilient modulus for pavement. Estimating stiffness of subgrade and unbound materials for pavement design. With innovations ranging from the advent of superpave, the data generated by the longterm pavement performance ltpp project, to the recent release of the mechanisticempirical pavement design guide developed under nchrp study 7a, the field of pavement engineering is experiencing significant development. The effective modulus of the pavement structure is determined by m r and deflection at the center of loading area. The pavement manual is now the responsibility of the maintenance division, so most references to the. Pavement design manual section 1 introduction page 1 1 introduction 1.
The resilient subgrade modulus value is estimated using cbr values in the absence of vigorous laboratory tests. The resilient modulus mr is a measurement of the stiffness of the roadbed soil. To this end, this study evaluates the modulus of subgrade considering the effect of rap and moisture content at different stress levels in. Indianadepartmentoftransportation 100northsenateavenue room1101 indianapolis.
Soil classification, gradation, moisture limits, lift thickness limits, compaction testing, test rolling, and engineering judgement. The modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabsonground. But there should be one, as both are the measurements of soil capacities and any of these two parameters can be used to design a regular foundation. The use of reliability %r permits the pavement design. The structural design of concrete pavements according to aashto and pca methods makes use of modulus of reaction k from the subgrade and subbasesubgrade system as.
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. Transportation criteria manual section 3 pavement design. This is a subgrade modulus method with nonlinear depth dependent loaddeformation characteristics representing the pilesoil interaction. Adjustments are made and iterations continue until the values used to predict subgrade modulus reasonably match the calculated stresses in the pavement system. Selection of subgrade modulus for pavement overlay design.
Characterization of subgrade soil mixed with recycled asphalt. Darwin me pavement analysis and design manual for njdot. Design resilient modulus of subgrade soils from fwd tests. Proceedings of sessions of geodenver 2000, held in denver, colorado, august 58, 2000. Ev 10 design subgrade cbr for entire layer thickness concern that this resulted in higher moduli than granular materials new procedure developed to sublayer select material, modulus is limited by modulus of underlying insitu subgrade modulus doubles every 150 mm thickness of select material, up to max 10 x cbr. An example of design without soil strength test is by using hrb soil classification system, in which soils are grouped from a1 to a7 and a group index is added to differentiate soils within each group.
While the standards contained in this manual provide a basis for uniform design practice for typical pavement design situations, precise rules which would apply to all possible situations are impossible to give. It includes some of the latest developments in the field, and some very useful computer softwaredeveloped by the authorwith detailed instructions. Base and subgrade layers must provide adequate and moisture resistant strength that meets the design modulus, in addition to durability and stability. In m e pavement design approach, the pavement is idealized as a layered structure generally assumed as elastic for simplicity in analysis consisting of three to four horizontal layers made up of bituminous surfacing, base, sub base and the subgrade. Design pamphlet for the determination of design subgrade in support of the 1993 aashto guide for the design of pavement structures publication no. Principles of bituminous pavement design and the recent trends. From a mechanical point of view, a subgrade soil represents a highly diverse heterogeneous structure. Selection of subgrade modulus for aashto flexible pavement design. Evaluation of engineering performance of subgrade material mixed with rap is important for pavement design and new constructions. Nov 09, 2015 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. Compaction testing useful, but not adequate for me design. Annual book of astm standards, section 4 construction, volume 04.
Figure 30 is a nomograph that determines the effective modulus of subgrade reaction. Geotechnical aspects of pavements fhwa us department of. In the current design and redesign of driving surfaces like pavement, it is crucial to understand the limitations of the underlying subgrade ground beneath the surface. The name of this manual is the pavement design manual pdm. For all new designs, particularly for critical projects, repeated load resilient modulus. Characterization of subgrade resilient modulus for mepdg and. Supplement to part 2 pavement structural design of the.
Trbs national cooperative highway research program nchrp synthesis 382. To this end, this study evaluates the modulus of subgrade considering the effect of rap and moisture content at different stress levels in the laboratory. Pdf field and laboratory determination of subgrade resilient. 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. Implementation of subgrade resilient modulus for pavement 2. 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.
Modulus of subgrade reaction k and kc k is the modulus of the subgrade soil. Modulus of subgrade reaction design k values for untreated subbases design k values for cementtreated subbases 30. Selection of subgrade modulus for aashto flexible pavement design robert p. This manual is neither a textbook nor a substitute for engineering knowledge. Joint transportation research program jtrp fhwainjtrp982 finalreport partii designsubgraderesilientmodulus implementationofsubgrade resilientmodulusforpavement designandevaluation a. Pdf models to estimate k subgrade reaction modulus. The resilient modulus value 3,000 psi used to represent the. An empirical analysis of flexible pavement design can be done with or with out a soil strength test. A conventional flexible pavement consists of a prepared subgrade or foundation and layers of subbase, base and surface courses aashto 1993 for the roadbed soils, the seasonal variation of resilient moduli is considered and used directly to determine the design or. The allowable number of load repetitions to cause fatigue cracking depends on the stress ratio between flexural tensile stress and concrete modulus of rupture. 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. Pdf subgrade resilient modulus for pavement design and.
This book consists of 26 chapters and is divided into two parts. Paul guyer is a registered civil engineer, mechanical engineer, fire protection engineer, and architect with over 35 years experience in the design of buildings and related. Selection of subgrade modulus for aashto flexible pavement. The capping materials in this figure can have a cbr between 4% and 10%. All subgrade and unbound pavement layers for all pavement types are characterized using m r in the nchrp 7a design methodology. With the recent release of the me design guide, highway agencies are. Take cores and perform lab tests strongly recommended.
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. The effects of variations in subgrade resilient modulus on various design parameters and on. Subgradefoundation design inputs transportation research board. The introduction of the resilient modulus into routine pavement design caused considerable concern and discussion among engineers re. Introduction to rigid pavement design ced engineering. Design pamphlet for the determination of design subgrade.
The use of the borrow material does not affect the design thickness of the pavement structure. These stresses are compared to those assumed values used in the initial iteration. Rdgn042 pavement design for carriageway construction page 2 of 42 6. A pavement design brief is essential for projects where the designer is external to transport and main roads, particularly where the contract is a type where the designer is employed or engaged by a third party such as a construction contractor or developer. Application of subgrade equivalency based on the japan equation. Front matter estimating stiffness of subgrade and unbound. To evaluate the subgrade strength is important during construction and design stage. It is a required input in the aashto method of flexible pavement design. Improved consideration of the influence of subgrade and unbound layers on pavement performance proposes and develops enhancements to aashtos pavement me design procedures for both flexible and rigid pavements, which will better reflect the influence of subgrade and.
This is a textbook on the structural analysis and design of highway pavements. Pavement design guide mepdg based on long term pavement performance ltpp data from all. California bearing ratio cbr, plate load test plt, modulus of elasticity e, modulus of subgrade reaction k. May 01, 2018 purpose the pavement manual has been revised to reflect the transf er of the pavement design group from the construction division to the maintenance division. Pavement subgrade, unbound materials, and nondestructive. This uptodate book covers both theoretical and practical aspects of pavement analysis and design. The pavement design manual is published by alberta transportation and. 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.
Next, an extensive laboratory testing program, several back calculation analyses, and overlay thickness designs were completed. The 1986 aashto guide for design of pavement structures 1 adopted the resilient modulus as the subgrade soil property controlling the design of flexible pavements. 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. If deflection testing is not performed, laboratory tests of subgrade samples should be performed to determine the resilient modulus of subgrade soil. The test involves driving a conetipped rod into the unbound layers by dropping a sliding hammer from a prescribed height onto an anvil attached to the rod as illustrated in.
The soil bearing capacity is 50 knm2 and soil is soft clay soil but to analyze this foundation in safe i need to know the subgrade modulus k value so any one can suggest the conservative k value range for this type of soil and. Soils tested were five cohesive soils and one granular soil. Pdf pavement design considerations for subgrades stabilized with. Characterization of subgrade soil mixed with recycled. Pavement design is primarily a matter of sound application of acceptable engineering criteria and standards. Base and subgrade layers must provide adequate and moisture resistant strength that meets the design modulus, in. Axle load spectrum 1,837,000 586,900 422,500 307,200 235,800 106,900. Water under pavement is one of the primary causes of pavement failure. Hence the performance of the pavement is affected by the characteristics of the subgrade. Pavement subgrade, unbound materials, and nondestructive testing. Design pamphlet for the determination of design subgrade in. Subgrade resilient modulus for pavement design and evaluation. Thus, this manual has been prepared to assist pavement design. A comprehensive, stateoftheart resource on pavement design and materials.
This value may be based on laboratory testing, back calculation programs using deflection measurements, resilient modulus correlation studies, or the equation presented in the aashto overlay design procedures based on deflection measurements. Design methods require modulus of subgrade reaction as input parameter for characterizing subgrade materials underlying rigid pavement structures. Foreword a key challenge faced by engineers using the 1993, aashto guide for design of pavement structures aashto guide is the selection of appropriate design values for the subgrade soil and for the pavement materials. Estimating stiffness of subgrade and unbound materials for. 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. If the subgrade has a resilient modulus less than 10,000 psi, the designer could consider improving or strengthening the subgrade soils. Expanded polystyrene eps geofoam has been used as lightweight subgrade for rigid pavement construction over weak soils. The final iterated value for resilient modulus is the design resilient modulus. For the design of rigid pavements in those areas where no previous experience regarding pavement performance is available, the modulus of subgrade reaction k to be used for design purposes is determined by the field platebearing test. Default kvalues for estimating resilient modulus of. For cohesive subgrades, a minimum of 95 % of aashto t 180, method d density modified compaction. In highway formations the subgrade layer, where acts as a pavement foundation should be well designed.
Next, resilient modulus mr of subgrade soils for different geographic regions in. Frost conditions mobilization construction, engineering manual em 1110. Traditionally fatigue cracking has been considered as the major, or only criterion for rigid pavement design. Department of transportation federal highway administration research and development turnerfairbank highway research center 6300 georgetown pike mclean, va 221012296. This book is written in a relatively simple way so that it may be followed by people familiar with basic engineering courses in mathematics and pavement design. Introduction to flexible pavement design ced engineering. 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. Implementation report author woojin lee, nihal chand bohra, a.
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