详情

原文传递 CALIBRATING WASHINGTON HYDRAULIC FRACTURE APPARATUS.

题名：	CALIBRATING WASHINGTON HYDRAULIC FRACTURE APPARATUS.
作者：	Alford-TE; Janssen-DJ
关键词：	RAPID-METHODS; TEST-METHODS; AGGREGATE-TESTING; D-CRACKING; SUSCEPTIBILITY-; HYDRAULIC-FRACTURING; MEASURING-EQUIPMENT; CALIBRATING-; PRESSURE-TIME-HISTORIES; PRESSURE-RELEASE-RATES
摘要：	The Washington Hydraulic Fracture Test (WHFT) was developed as a part of the Strategic Highway Research Program (SHRP) as a rapid method to identify aggregates susceptible to D-cracking. WHFT relies on the pressure differential between the inside and outside of the aggregate pieces to cause D-cracking susceptible pieces to fracture. D-cracking susceptible aggregates sources are identified as those that produce more fracturing than non-D-cracking susceptible sources. Agencies will be able to establish their own criteria for threshold fracturing, which defines D-cracking. Experience, however, suggests that a hydraulic fracture index of approximately 60 to 80 or lower indicates D-cracking susceptible aggregate. Though the procedure was found to be fairly reliable for a large range of aggregate sources, the critical parameters of the test procedure were not determined during SHRP. Specifically, the critical pressure release rate believed to be responsible for the WHFT mechanism was not determined. Current research for the Michigan Department of Transportation is investigating the applicability of the WHFT for Michigan. Included in the work plan is the determination of what parameters were necessary to ensure that equipment remained in calibration. The important parameters necessary for calibration are described and the sensitivity of those parameters determined. Modifications were made to the WHFT apparatus and to the testing procedure so that a range in the amount of fracturing in the aggregate was produced. Measurements of the pressure-time history during pressure releases were taken, and pressure release rates determined from these pressure-time histories were compared with the amount of fracturing produced. The amount of fracturing produced was found to be sensitive to a pressure release rate at very short time durations (typically less than 0.02 sec). This information can be used to specify the pressure release rate at a given time duration so that agencies can be assured that multiple copies of WHFT equipment produce the same test results.
总页数：	Transportation Research Record. 1995. (1486) pp142-148 (6 Fig., 1 Tab., 9 Ref.)
报告类型：	科技报告