The Texas Department of Transportation (TXDOT) has embarked upon one of the largest transportation infrastructure projects in the world: the Trans-Texas Corridor.
On its Web site, TXDOT shows conceptual alignments of a yet-to-be-determined route paralleling the commercial backbone of the state: the Interstate 35 corridor. The first portions of the road are under construction and had been featured previously in the Oct. 15, 2005, issue of Construction Equipment Guide.
Currently, the corridor is being publicized by the transportation lobby in Austin and will contribute an enormous investment in capital infrastructure, with the aim of continued economic development and prosperity through the 21st century.
On the Trans-Texas Corridor Web site (www.keeptexasmoving.org), there are statistics and research compiled by the Perryman Group in Waco, Texas. The vision of the corridor is best summarized by Ray Perryman, president of Perryman Group, in his report called “Moving Into Prosperity”:
“Because the TTC enhances efficiency, improves logistics, and reduces transportation time and costs, it increases the ability of companies within the region to expand intrastate trade and operations and, thus, increase market size and market share on a global basis,” Perryman wrote. “These factors improve competitiveness and profitability across a broad spectrum of industrial sectors, and the strategic position of Texas as a site for corporate locations and expansions is enhanced.”
As developers, design professionals, and property owners anticipate the massive undertaking, planning and cost estimates for the roadway are being fine-tuned. The alignment will run between San Antonio and the Dallas Fort-Worth Metroplex, veering to the east of the City of Dallas. The section that is already open, TX130, is equipped for tolling, but currently serves as a free reliever for I-35, which currently is undergoing large swaths of reconstruction through the Central Texas plains.
Future design seeks to unify passenger and freight rail, as well as heavy truck traffic, with selected direct connection to the municipalities and arterials traversed by the corridor. This poses interesting problems in construction. Since the corridor is so long, it passes through varying soil and bedrock formations. While the alignment will be as close to grade as possible to optimize cuts and fills across the right-of-way, there will be selected fill on expansive clays in North Texas as well as cuts into shallow bedrock, particularly in the Texas Hill Country.
For clay soils, TXDOT implements a lime-stabilized subcourse. Lime is hydrated at a nearby batch plant, and delivered, typically in 7 cu. yd. (5.4 cu m) trucks, which discharge through gravity onto compacted earth. The lime is then mixed, using a soil stabilizer, similar to the CAT-RM-350B. This machine is equipped with a 500 hp (372.7 kW) flywheel power rating. It is capable of a 4.5 ft. (1.4 m) cut, and can operate as fast as 10 mph. Typically, this is used for mixture of hydrated lime into a road or parking surface subgrade. However, current university research has focused on alternative soil stabilization practices, ranging from cement-stabilization to gypsum in some applications.
As the earth is limed, and the route prepared for the Trans-Texas Corridor, the slip-form paving machine will be a familiar site along the wide-open Texas prairie and farmland, paving across colossal tonnage of white, hydrated lime.
(David H. Recht owns an Irving-based civil engineering and construction firm.) CEG