01044085

Component

Forensic investigations of pavement failures are critical, as the information gained can be used to identify the underlying cause of the problem, develop an optimal rehabilitation strategy, and to resolve construction disputes. The Texas Department of Transportation has had a formalized forensic team approach for over 10 years. Application of nondestructive testing such as the Ground Penetrating Radar (GPR) and Falling Weight Deflectometer (FWD), as well as field testing such as Dynamic Cone Penetration (DCP), coring, and laboratory testing have been found critical to these forensic investigations on flexible pavements. The root causes of the pavement failures often can be identified through these tools, in conjunction with thorough review of construction records and rehabilitation history. In this paper three field projects are presented to illustrate the integrated approach used widely in Texas. In each case the combined GPR and FWD data was extremely useful at identifying contributing factors; such as stripping in the hot mix or localized areas of wet or weak base. The DCP is used for validating problems with base and subbase layers. To determine the optimum rehabilitation strategy, it requires knowledge of what is the main cause of the problem. Laboratory tests are often required to complete the investigation especially if the repair strategy calls for in place recycling of the existing structure. The extent of stripping and high porosity that caused delamination for projects 1 and 2 were detected by GPR and verified by core samples. This combination (GPR+coring) was used to map the entire project. GPR, FWD, DCP and field soil samples all showed indications that the existing base on project 1 was wet and the stiffness was only about 1/3 of a typical flexible base in Texas. FWD data demonstrates that the pavement structure for projects 1 and 2 were inadequate, so a rehabilitation strategy was selected that included structural strengthening. In project 3, GPR, lab density, and permeability tests indicate that the dramatic pavement failures were attributed to moisture entering the base through a poorly-compacted AC layer and poor longitudinal joints. The base material was found to be highly susceptible to moisture. It did not meet TxDOT’s compressive strength requirements when subjected to capillary soaking. The repetitive triaxial test results revealed that the stiffness and load carrying capability became inadequate when the base materials were exposed to moisture. The techniques demonstrated in this study are widely used within Texas and are applicable to a wide range of pavement forensic studies.

01042056

07-0309

English

27p

2007

Transportation Research Board 86th Annual Meeting

CD-ROM

Figures; Photos; References (11)

Base course (Pavements); Compressive strength; Cone penetrometers; Falling weight deflectometers; Flexible pavements; Forensic science; Ground penetrating radar; Pavement design; Pavement distress; Pavement maintenance; Pavement performance; Pavements; Rehabilitation; Structural engineering; Triaxial shear tests

Load carrying capacity

Texas

Highways; Pavements; I23: Properties of Road Surfaces

Transportation Research Board Annual Meeting 2007 Paper #07-0309

PRP, TRIS, TRB

Feb 8 2007 4:51PM