The Texas Modified Triaxial (MTRX) Design Program

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E.G. Fernando, W. Liu, T. Lee, T. Scullion

Publication Date:

October 2001


The Texas Department of Transportation (TxDOT) uses the Texas modified triaxial design procedure as a design check to the Flexible Pavement System (FPS) design method. This report describes a computer program researchers developed to check the adequacy of the thickness design from FPS based on the Mohr-Coulomb yield criterion. The modified triaxial (MTRX) program incorporates the following features: 1) characterization of pavement materials using layer moduli backcalculated from FWD deflections and strength properties determined from Texas triaxial tests or approximate procedures; 2) modeling of single and tandem axles to evaluate pavement damage potential under different axle configurations; 3) application of layered elastic theory to predict stresses under applied wheel loads (with the option of characterizing pavement materials as linear or nonlinear); and 4) application of Mohr-Coulomb failure criterion to check pavement damage potential. Instructions on the operation of the computer program are given in this report.

Report Number:



Triaxial Test, Mohr-Coulomb Failure Envelope, Pavement Design

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