Determining The Critical Thaw Weakened Period In Asphalt Pavement Structures

Author : Erik Simonsen
Publisher :
ISBN 13 : 9789929658332
Total Pages : pages
Book Rating : 4.6/5 (583 download)

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Download or read book On Thaw Weakening of Pavement Structures written by Erik Simonsen and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This doctoral thesis focuses on thaw weakening of pavement structures. The thesis consists of a literature review (Paper I), modeling and field verification of an evaluation procedure for pavements exposed to seasonal frost conditions (Papers II and III), and experimental studies on the resilient properties of unbound road materials during freezing and thawing (Papers IV and V).The literature review describes factors identified as significant for the extent of weakening during soil thawing, e.g. soil type, permeability, drainage conditions and rate of thaw. Also the rate of freezing may indirectly affect thaw weakening. Persisting structural changes in soil fabric are also frequently observed. Findings concerned with frost action effects on a number of test roads are presented. The effects of frost action on resilient behavior are also described. In conclusion, attempts to develop semi-mechanistic pavement design and evaluation procedures for pavements in cold regions are presented. Although the effects of climate on pavement structures are recognized as a major contributor to the deterioration of pavement structures in cold regions, only a few models concerned with both frost heave and thaw settlement have been developed. In Paper II, a coupled mass and heat transfer model is tested and evaluated with respect to parameters critical to thaw weakening. The results indicate that soil temperature is predicted very well and soil moisture relatively well during freezing and thawing. Paper III presents an initial attempt to implement a commercially available finite element program in an evaluation procedure for pavements in seasonal frost areas. The results are compared with data from an extensively instrumented test road and indicate that surface deflection and relative change in pavement stiffness are predicted very accurately. Although a time lag between maximum measured and predicted surface deflection is observed during thawing, the procedure is found to be promising. The results from extensive resilient modulus laboratory tests during freezing and thawing are presented in Paper IV. The results indicate that all the soils exhibited substantially decreased resilient modulus after freeze-thaw. The decrease is ascribed to an observed increase in volume, and consequently a looser soil structure, due to freeze-thaw. A significant hysteresis for the clay soil in warming and cooling was also observed. Variable confining pressure (VCP) triaxial tests are generally preferred to constant confining pressure (CCP) tests, due to the more realistic stress application. However, VCP tests have never been utilized for investigation of freeze-thaw effects on unbound road materials. Paper V reports results obtained utilizing CCP and VCP triaxial tests for the characterization of resilient soil behavior during freezing and thawing. The results indicate a significant difference in moduli computed from CCP and VCP data. However, resilient moduli display compatible values if interpreted in terms of mean values of deviator stress and mean normal stress. With regard to freeze-thaw effects on resilient moduli, the results are inconsistent with previous findings. However, this can be explained by the different test conditions applied. (Abstract shortened by UMI.)