SPA Application: Quality Management of Flexible Pavements

The primary strength parameters that affect the performance of a flexible pavement section are the moduli of different layers. Current mechanistic-empirical procedures for structural design of flexible pavements consider these parameters. Construction specifications however are not based on these engineering parameters.

Procedures have been developed to measure the moduli of each pavement layer shortly after placement. The PSPA allows rapid data collection and interpretation for this purpose. Thus, any problem during construction process can be identified and adjusted. The major advantages of seismic measurements is that the PSPA can characterize material properties at depth and delineate changes within a layer.

Test protocols have been developed for a comprehensive quality management for subgrade, base and hot mix asphalt layers

Case Studies for Quality Management of Flexible Pavements

Quality Management of Flexible Pavement Layers with Seismic Methods
by
Soheil Nazarian, PhD, PE; Deren Yuan, PhD; Vivek Tandon, PhD, PE and
Miguel Arellano, PE

Research Project 0-1735
Texas Department of Transportation
The Center for Highway Materials Research
The University of Texas at El Paso
El Paso, TX 79968-0516
Research Report 1735-3F
December 2002

Abstract


Under this project several field protocols and test equipment have been developed, which in a rational manner, combine the results from laboratory and field tests with those used for quality control during construction. The significance of the project is that more rational methods for quality control during construction can be developed, at the same time, feedback to the pavement design engineer can be provided in terms of the assumption made to design the pavement. The protocols proposed have potential to provide the first step towards developing performance-based specifications.

This report contains the results of an effort to address the issues related to the implementation of the devices recommended in the day-to-day operation of TxDOT. The major issues that are addressed are the repeatability, reproducibility of the methods, means of relating the measured parameters to the design moduli, and relating the parameters to performance of the pavement.


Use of Resilient Modulus Test Results in Flexible Pavement Design
Soheil Nazarian(1), Imad Abdallah(2)
Center for Highway Materials Research, The University of Texas
at El Paso, El Paso, TX 79968

Amitis Meshkani(3)
Flexible Pavement Branch, Texas Department of Transportation, 9500 Lake
Creek Parkway, Bldg 51, Austin, TX 78717

Liqun Ke(4)
Nichols Consulting Engineers, Chtd., 1101 Pacific Ave Ste 300, Santa Cruz,
CA 95060

Abstract

The state of practice in designing pavements in the United States is primarily based on empirical or simple mechanistic-empirical procedures. Even though a number of state and federal highway agencies perform resilient modulus tests, only few incorporate the results in the pavement design in a rational manner. A concentrated national effort is on the way to develop and implement mechanistic pavement design in all states. In this paper, recommendations in terms of the use of the resilient modulus as a function of the analysis algorithm selected and material models utilized are made. These recommendations are also influenced by the sensitivity of the critical pavement responses to the material models for typical flexible pavements. The inaccuracies in laboratory and field testing as well as the accuracy of the algorithms should be carefully considered to adopt a balance and reasonable design procedure. The more sophisticated the material models and the analysis algorithm are, the closer the calculated response will be to the actual response of the pavement.

Integrating Seismic and Deflection Methods to
Estimate Pavement Moduli


Imad Abdallah, Deren Yuan and Soheil Nazarian
Center for Highway Materials Research
The University of Texas at El Paso
El Paso, Texas, 79968

A Paper for Inclusion in A2L02/A2K01 Session Entitled
Integrated Methods of Subsurface Characterizations
2001 Annual TRB Meeting

Abstract

Nondestructive testing (NDT) of pavements has made substantial progress during the last two decades. Most algorithms currently used to determine the remaining life of pavements rely on stiffness parameters determined from NDT devices. One major area of continual improvement is the reliable and rapid extraction of stiffness parameters from nondestructive field data. Two of the most common NDT methods used are the deflection and seismic-based methods. The Spectral Analysis of Surface Waves (SASW) tests are the most common seismic method. In this method, time records obtained with vibration sensors are used to obtain an experimental dispersion curve, which through an inversion procedure, provides an estimate of the elastic modulus profile of the pavement. Deflection bowls are also used to backcalculate modulus profiles of pave ments through the inverse theory. The inversion processes used in both methods are complex and either requires a significant computational effort and/or frequent operator’s intervention. Each method, of course, has its own limitations and strengths. To improve the accuracy of the predicted moduli, an algorithm for joint reduction of the deflection and seismic based data have been developed. Thickness and modulus of each pavement layer are estimated in real time using artificial neural network models.

This paper provides an overview of a proposed joint inversion and its practical use in pavement analysis and design. The joint reduction algorithm shows promise since it seems to be more robust and to yield more consistent results when compared with the process and results from each method independently.


Geomedia SPA Application: Quality Management of Flexible Pavements