INTRODUCTION In recent years, there has been an increasing number of full-scale and small-scale strength and stiffness measuring devices available in many countries around the world for characterizing subgrades and granular layers.
PAVEMENT MODULI BACKCALCULATION SHORTCOURSE FULL
Although some good correlations have been obtained in various cases, the results have been found to be material dependent, and so the equations should be used with care and only with a full understanding of the material properties of the soils on which the correlative expressions were developed and of the soil being tested. It indicates that the variation in the correlative expression output results for each type of test makes their use entirely uncertain, at least for the studies carried out in Israel. The paper presents a comparison of local correlative expressions with some of those described. Various established correlative expressions between CBR and each of the following testing outputs are given in the technical literature: (a) DCP index, (b) VSS, (c) M R (backcalculated Resilient Modulus from FWD testing or Resilient Modulus from direct laboratory testing), (d) M FWD (Resilient Surface Modulus, also known as Stiffness, from FWD testing), and (e) M LDW (Resilient Surface Modulus, also known as Stiffness, from LDW testing). Copyright © National Academy of Sciences.1 UNCERTAINTY ASSOCIATED WITH PRE-DEFINED CORRELATIVE EXPRESSIONS OF VARIOUS IN-SITU TEST OUTPUTS By: Moshe Livneh Faculty of Civil and Environmental Engineering Transportation Research Institute Technion-Israel Institute of Technology Technion City, Haifa Israel Phone: (972 4) Fax: (972 4) PRESENTED FOR THE 2007 FAA WORLDWIDE AIRPORT TECHNOLOGY TRANSFER CONFERENCE Atlantic City, New Jersey, USA April 2007Ģ Livneh 1 ABSTRACT The paper deals with the following full-scale and small-scale strength and stiffness measuring devices: Dynamic Cone Penetrometer (DCP), Vane-Shear Strength (VSS), Falling Weight Deflectometer (FWD), and the Light Drop Weight (LDW) tests.
PAVEMENT MODULI BACKCALCULATION SHORTCOURSE PDF
Unless otherwise indicated, all materials in this PDF are copyrighted by the National Academy of Sciences. Distribution, posting, or copying of this PDF is strictly prohibited without written permission of the Transportation Research Board of the National Academy of Sciences. 1293, Backcalculation of Pavement Moduli 1991. This paper appears in Transportation Research Record No.Find a library where document is available.Finally, an expert system approach that uses a specific analyst's knowledge to prepare input for the mechanistic backcalculation program and to interpret results is described. The sources of systematic errors and ways to reduce them are discussed. The results indicate that discrepancies among agencies can be large however, a few agencies reached good agreement in many cases. To better understand the accuracy and consistency of the available backcalculation procedures, backcalculation results from different agencies using various procedures were compared. Such variation causes concern because engineers will not have confidence using the backcalculated moduli in pavement evaluation or design if the size of the error associated with the backcalculated moduli values is unknown. However, the results often vary among analysts because of the assumptions made in each procedure and the different input assigned by individual analysts. A number of pavement structural models and computerized procedures have been developed to perform backcalculation.
ACCURACY AND CONSISTENCY OF BACKCALCULATED PAVEMENT LAYER MODULIīackcalculation of pavement layer moduli from deflection measurements has been a focus of recent pavement research because of the need to adopt mechanistic design and analysis methods and the widespread use of nondestructive testing devices such as the falling weight deflectometer and Dynaflect.
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