UFC 3-260-03
15 Apr 01
CHAPTER 4
PAVEMENT EVALUATION USING NONDESTRUCTIVE TESTING
1. EVALUATION PRINCIPLES. The structural deterioration of flexible pavements caused by traffic is
normally evidenced by cracking of the asphalt concrete (AC) surface course and development of ruts in
the wheel paths. The NDT evaluation procedure handles these two modes of structural deterioration
through limiting values of the strain at the bottom of the AC layer and at the top of the subgrade. Failure
of rigid pavements due to the repeated application of loads (fatigue) is normally evidenced by cracking of
the portland cement concrete (PCC) layer. Performance criteria for rigid pavements are based on limiting
the tensile stress in the PCC slab to levels such that failure occurs only after the pavement has sustained
a number of load repetitions. The stresses and strains used for entering the criteria are computed by the
use of Burmister's solution for multilayered elastic continua. The solution of Burmister's equations for
most pavement systems will require the use of computer programs and characterization of pavement
materials by the thickness, modulus of elasticity, and Poisson's ratio.
2. PAVEMENT RESPONSE MODEL. The computer code recommended for computing pavement
response is the five-layer linear elastic program WESLEA, which is a subroutine of the Layered-Elastic
Evaluation Program (LEEP). When WESLEA is used, the following assumptions are made:
a. The pavement is a multilayered structure, and each layer is represented by the thickness, a
modulus of elasticity, and Poisson's ratio. Individual layers are assumed to be homogeneous, isotropic,
and extending infinitely in the horizontal direction.
b. The interface between layers is continuous; i.e., the friction resistance between layers is greater
than the developed shear force.
c.
The bottom layer is of infinite thickness.
d. All loads are static, circular, and uniform over the contact area.
3. PROCEDURE. The procedure outlined in this chapter is applicable to flexible, plain concrete, plain
concrete overlays, and nonrigid overlays on plain concrete pavements. Criteria are not yet available for
reinforced or fibrous pavements. The procedure outlined in this section is based on a layered linear
elastic model that characterizes multilayered pavement systems. The program uses layer strength
parameters determined from field in situ measurements to compute allowable loads for a selected number
of aircraft passes, allowable passes at a specified load, and the Pavement Classification Number (PCN).
Strengthening requirements can then be determined for the design pass level and aircraft load. The
evaluation will be valid for conditions existing at the time of test. The evaluation procedure is computer
based, and installation guidelines for these programs are given in appendix C. Computer programs
needed for the evaluation may be obtained as discussed in chapter 9.
4. STEP 1 (FEATURE IDENTIFICATION). Pavement facilities are divided into features according to
type of traffic area, pavement type, and/or construction.
a. Traffic Areas. Air Force airfield pavements are categorized by traffic area as a function of traffic
distribution and aircraft weight. The Air Force defines traffic areas in four categories (types A, B, C, and
D) as described in TI 825-01/AFM 32-1124(I)/NAVFAC DM 21.10. The Army defines traffic areas in three
categories (types A, B, and C). The Navy and Marine Corps define traffic areas as primary and
secondary. For evaluation purposes, the Navy and Marine Corps also use the Army defined A, B, and C
traffic areas. "A" is used for channelization traffic typically found on aprons. The terms "primary" and
"secondary" refer to the pavement rank which is assigned as part of the condition survey. A primary
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