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原文传递 Heavy-Duty Flexible Bases: Field Performance and Draft Specifications.

题名：	Heavy-Duty Flexible Bases: Field Performance and Draft Specifications.
作者：	scullion, t. harris, j. p. sebesta, s. nazarian, s.
关键词：	texas, specifications, field performance
摘要：	Traditional Texas flexible bases specified under Item 247 perform well as long as they are kept dry. However, rapid and sudden failures can occur if water enters these bases. The source of the moisture susceptibility problems is the fine clay in these bases. One base in this study contained over 2 percent Smectite, a highly expansive clay mineral. The concept of heavy-duty bases resolves around (a) controlling the type and amount of fine material and (b) requiring a high-strength rock. In Project 4358 laboratory and field studies were conducted. The use of heavy-duty bases with fines contents between 5 and 10 percent requires modifications to laboratory testing, design, and field construction procedures. Three TxDOT projects containing bases which met the proposed heavy-duty base specifications were monitored in this study. The long-term benefits of these low-fines bases could not be demonstrated in this short study, as all the applicable sections are new and performing well. However, the oldest section on FM-1810 in the Fort Worth District has higher long-term modulus than the control Item 247 base section. This report includes a draft construction specification (Item 245) for consideration on future heavy-duty base projects. This specification is based on recommendations from Texas district laboratory engineers. Heavy-duty bases will cost more than traditional bases, and they are not required in many areas of west Texas where rainfall is low. However, these bases will be economically viable in many areas of Northeast Texas, especially with the escalating prices of traditional road building materials. / NOTE: Technical rept. (Sept. 2004-Aug. 2005). / Supplementary Notes: See also PB2006-109714 and PB2007-103749. Sponsored by Texas Dept. of Transportation, Austin. Research and Technology Implementation Office. and Federal Highway Administration, Austin, TX. Texas Div. / Availability Note: Order this product from NTIS by: phone at 1-800-553-NTIS (U.S. customers); (703)605-6000 (other countries); fax at (703)605-6900; and email at orders@ntis.gov. NTIS is located at 5285 Port Royal Road, Springfield, VA, 22161, USA.
总页数：	u0813；126p
报告类型：	科技报告