For example, the resilient modulus of cohesive soils typically decreases. In 2005, txdot initiated research 0 4714 to evaluate the mepdg for potential implementation. Department of transportation federal highway administration research and development turnerfairbank highway research center 6300 georgetown pike mclean, va 221012296. And one of the major functions of a highway pavement is to reduce the. The method of excavation and replacement is commonly adopted in situations where the subgrade soaked cbr is less than the assumed design soaked cbr. General information the subgrade is that portion of the pavement system that is the layer of natural soil upon which the pavement or subbase is built. Pavement design now the guide to pavement technology.
Aci the modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of slabsonground. Resilient modulus of subgrade materials for mechanistic. Resilient modulus and aashto transportation research board. The pavement design engineer must integrate this information into the materials design package materials design report, pavement design summary and preliminary pavement structure cost estimate that will provide the necessary documentation and communication of this design process. It is the single most important unbound material property input in most current pavement design procedures. 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. Prediction of subgrade resilient modulus for flexible. The effects of variations in subgrade resilient modulus on various design parameters and on the aashto design thickness are examined. It is not intended as definitive treatise, and it does not encompass the design of rigid pavements. Engineers are cautioned that much of pavement design is governed by codes, specifications and practices of public agencies. To facilitate pavement design, the new proposed mechanisticempirical pavement design guide recommends the resilient modulus to characterize subgrade soil and its use for calculating pavement responses attributable to traffic and environmental. The nature and properties of subgrade soils must be considered in struc tural pavement design. The plate load test see figure 1 and 2 can be used to measure the modulus of subgrade reaction for in situ material. The effects of variations in subgrade resilient modulus on various design parameters.
Thompson subgrade soils play an integral part in pavement performance. The kvalue can be determined by field tests or by correlation with other tests. Estimating base layers and subgrade modulii for me pavement. Under average conditions the concrete should achieve a 28day modulus of rupture mr of 550 to 700 psi 3. A new four lane divided highway is to be constructed on a subgrade of cbr. Prediction of subgrade resilient modulus for flexible pavement design article pdf available in scientific research and essays 621 september 2011 with 1,087 reads how we measure reads. Since pavement design is ultimately an attempt to minimize future pavement distresses and, thereby maximize. Subbase thickness10 subbase modulus30,000 psi subgrade m r10,000 psi to get k. Subgrade soil provides support to the remainder of the pavement system. Engineering properties of stabilized subgrade soils for. Aci the modulus of subgrade reaction is an often misunderstood and misused concept for the thickness design of. 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. Design pamphlet for the determination of design subgrade. Introduction to rigid pavement design ced engineering. The final iterated value for resilient modulus is the design resilient modulus. Design pamphlet for the determination of design subgrade in.
Soilpropertybased subgrade resilient modulus estimation for flexible pavement design kevin 0. Selection of subgrade modulus for aashto flexible pavement design. 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. Introduction to flexible pavement design ced engineering. Selection of subgrade modulus for pavement overlay design. Hence the performance of the pavement is affected by the characteristics of the subgrade. A comprehensive laboratory study was undertaken to determine engineering properties of cementitiously stabilized common subgrade soils in oklahoma for the design of roadway pavements in accordance with the aashto 2002 mechanisticempirical pavement design guide mepdg. Subgrade impact to pavement performance benchmark inc. The study recommended, for various reasons, not to implement the mepdg as a replacement for the design methods currently being used.
The variation of truck factor with asphalt layer thickness and subgrade modulus was also studied. All borings should extend through unsuitable foundation strata for example. Impact of axle overload, asphalt pavement thickness and. The primary objective of this work is to investigate the resilient modulus of four typical victorian finegrained subgrade soils under trafficlike repeated. Design pamphlet for the determination of design subgrade in support of the 1993 aashto guide for the design of pavement structures publication no. Fulldepth pavement constructed on subgrade deepstrength pavement constructed on thin granular base course aka extendedlife pavement or longlife pavement. Beginning in 1986, the aastho design guides have recommended use of resilient modulus for characterizing subgrade support for flexible and rigid pavements and for determining structural layer coefficients for flexible pavements. The loaddeformation characteristics of the granular. However, it is recommended that a k value be established for the subgrade and then corrected to account for the effects of subbase. 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. Selection of subgrade modulus for aashto flexible pavement. Resilient modulus of stabilized subgrade for flexible pavement design resilient modulus of stabilized subgrade for flexible pavement design.
Subgradefoundation design inputs transportation research board. Experimental evaluation of subgrade modulus and its. Mar 25, 2009 the austroads guide to the structural design of road pavements. Pdf evaluation of granular subgrade modulus from field and. The introduction of the resilient modulus into routine pavement design caused.
With the recent release of the me design guide, highway agencies are. Flexural strength modulus of rupture subgrade strength, or subgrade subbase combination modulus of subgrade reaction, kvalue weights, frequencies, and types of truck axle loads load transfer load safety factor design period design factors. Page 1 of 11 modulus of subgrade reaction which one should be used. This paper describes the test program, proposed test protocol for subgrade resilient modulus m r, determination of m r values, and development of design tables and constitutive models for m r estimations. Progressive development of the guide is required to take advantage of improved knowledge and technology and hence improve pavement design procedures. In some cases, these surface distresses are due directly to deficiencies in the asphalt or concrete surface layers.
Estimation of subgrade resilient modulus using the. Note that m r is the principal material input parameter for designing asphalt pavement using the recent mechanisticempirical pavement design software. These two parameters are the two main elements that may influence the pavement design, especially in canada. Overview of rigid pavement subbase design base layer combinations for concrete slab support crcp or cpcd. This is a subgrade modulus method with nonlinear depth dependent loaddeformation characteristics representing the pilesoil interaction. Base and subgrade layers must provide adequate and moisture resistant strength that meets the design modulus, in. Design of pavement structures 1993 requires selecting a value for the design subgrade resilient modulus. Geotechnical aspects of pavements fhwa us department of.
Base and subgrade layers must provide adequate and moisture resistant strength that meets the design modulus, in addition to durability and stability. Perpetual pavement asphalt pavement designed to last over 50 years without major structural rehabilitation needing only periodic surface renewal. The aashto 1993 design manual recommends using the last sensor deflection for calculating the resilient modulus of the subgrade. Any required fill material shall be placed to the subgrade elevation prior to sampling. Resilient modulus has been used for characterizing the stressstrain behavior of subgrade soils subjected to traffic loadings. As a first step of the current study, different percentages of rap and. 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. Pavement performance depends greatly upon the qua lity and uniformity of materials incorporated into the pavement structure. Front matter estimating stiffness of subgrade and unbound. 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. Soilpropertybased subgrade resilient modulus estimation. Under average conditions the concrete should achieve a. Cut across the e sb cut across m r to the tl vertically meet other line read kvalue k600pci topic 10 aashto rigid pavement design figure 12. Adjustments are made and iterations continue until the values used to predict subgrade modulus reasonably match the calculated stresses in the pavement system.
Pdf prediction of subgrade resilient modulus for flexible. The austroads guide to the structural design of road pavements. Models to estimate subgrade resilient modulus for pavement. 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. Astm d 6951 describes the dcp apparatus and test methodology. Estimating base layers and subgrade modulii for me. Based on the mdot field manual of soil engineering, the information obtained. The effects of variations in subgrade resilient modulus on various design parameters and on. Subgrade samples were collected from 12 locations throughout the state of wyoming, usa for standard laboratory and m r tests. 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. Prediction of subgrade resilient modulus for flexible pavement design mehmet ridvan ozel 1 and abbas mohajerani 2 1department of civil engineering, school of engineering and architecture, gediz university, izmir, turkey. Part 2 pavement structural design has been used throughout australia for over 20 years. The quality of the subgrade will greatly influence the pavement design and the actual. Modulus of subgrade reaction which one should be used.
Aasho road test subgrade in the aashto flexible pavement design equation is. Engineers must always determine the requirements of the. The upper 500 mm of soil, whether in embankment or in cutting, compacted to a higher density than that of the native soil below it is considered as the subgrade of a flexible pavement as per the current practice in india. The modulus of subgrade reaction is a required parameter for design of rigid pavements. Nov 09, 2015 astm d 6951 describes the dcp apparatus and test methodology. It estimates the support of the layers below a rigid pavement surface course the pcc slab. The modulus of subgrade reaction k is used as a primary input for rigid pavement design. When the subgrade does not possess these attributes, corrective action in the form of a subgrade treatment is needed. It can be used to evaluate undisturbed soil andor compacted, unbound layers within existing pavements.
The pavement design manual is published by alberta transportation. This is an introduction to flexible pavement design for engineers. The foundation modulus k value should be assigned to the material directly beneath the concrete pavement. This study investigates the effect of rap on the resilient modulus m r of subgrade soils mixed with rap materials. Pdf pavement design considerations for subgrades stabilized with. 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. Selection of subgrade modulus for aashto flexible pavement design robert p. Resilient modulus of subgrade soils is an important input in mechanistic pavement design. Pavement design keywords mechanistic empirical flexible pavement design mnpave me fatigue rutting asphalt modulus stress strain layered elastic analysis lea weslea minnesota department transportation subgrade soil aggregate base proctor density. 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. Characterization of subgrade soil mixed with recycled asphalt.
There is no direct laboratory procedure for determining kvalue. This paper discusses various methods used to obtain the design effective subgrade. In march 2004, nchrp 7 report and the mechanistic empirical pavement design guide software mepdg were released. Resilient moduli measured through repeated triaxial load tests on cylindrical. Example of repeated load triaxial resilient modulus test results of a clay soil.
Subgrade soil characterization, in terms of resilient modulus, is crucial for both flexible and rigid pavement design. The effects of variations in subgrade resilient modulus on var ious design parameters and on. 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 test involves pressing a steel bearing plate into the surface to be measured with a hydraulic jack. Estimation of subgrade resilient modulus using the unconfined.