ETTL Engineers & Consultants Inc.

Pavement Design Services

ETTL regularly provides pavement design services for a variety of clients in road, highway, parking lot and similar projects. The general procedure followed involves taking soil samples, usually either by backhoe or shovel, along the right-of-way (ROW) of a road, or in the area where a parking lot or other construction calling for pavement is to be installed. The samples are transported to ETTL's soil labs where they first undergo Proctor testing (to determine moisture/density relationship).

For TxDOT pavement designs, each soil sample undergoes Texas Triaxial testing (see photo at left) to determine its subgrade stiffness modulus — one of the strength parameters used in pavement design. These and other data are turned over to ETTL's engineering department, most often to Project Engineer Robert Duke (right), for the pavement design to be worked out, following TxDOT formulas that take into consideration such factors as traffic counts and proximity to nearby metropolitan areas. The resulting design will recommend thicknesses and materials for the various layers of the pavement, with options relating to economy, strength and other factors.

In a recent project, ETTL took numerous soil samples along the ROW of the first leg of an outer loop being constructed around Tyler, TX, and provided recommended pavement designs to TxDOT.

With various other clients, ETTL may use slightly different testing techniques. For example, in a recent project for UT-Tyler, soil samples were taken by an ETTL technician (left photo) to provide pavement design data for a new parking lot planned to be built near the University's administrative center. In this case, formulas used by AASHTO (the American Association of State Highway & Transportation Officials) were employed, and instead of Texas Triaxial testing, California Bearing Ratio (CBR) tests were carried out. In photo at right, an ETTL lab technician carries out a CBR test. (It looks almost like a Triaxial test, but it is different!)

For in-depth information about ETTL's Pavement Design Services, contact Robert Duke

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