TxDOT Austin District 
​I-35 at Oltorf
Austin, TX

The overall project consisted of major reconstruction of the I-35 corridor from Hillsboro to Salado (90 miles total) in Travis County. The reconstruction project will result in the completion of eight lanes through Waco and Belton and six lanes through the remainder of the corridor. GES is the Geotechnical Engineer-of-Record for reconstruction of an approximately 2-mile section near downtown Austin.

Project consisted of developing PS&E plans for bridges, MSE walls, new frontage roads, main lanes and cross streets along the alignment.  Proposed pavement improvements included widening of main lanes, adding auxiliary lanes, and widening of frontage roads. FWD data and GPR data was provided by TxDOT to aid in evaluating the thickness and stiffness of existing pavement, base, and subgrade.  FWD data provided by TxDOT was used to evaluate the moduli values of existing asphalt, base, and subgrade. Modulus software program was used to analyze the FWD data.  FPS mechanistic empirical software program was used to design flexible pavement.

SMA, HMA, asphalt stabilized base and flexible base options were provided for I-35 main lanes. TOM, HMA and flexible base option was provided for I-35 frontage roads. I-35 main lanes were designed as perpetual pavement. 

GES provided geotechnical recommendations for proposed MSE walls, cast-in-place walls, sign structures, pavement and bridges.  MSE wall strap lengths ranged from 0.7 to 1.1 times the height of the wall.  Subgrade improvement was required for walls greater than 20-feet in height.  Subgrade improvement consisted of removing and replacing onsite soils with flexible base material.  Drilled piers bearing in shale were recommended for proposed bridges.