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原文传递 AUTOMATIC STRESS PATH CONTROL SYSTEM FOR HOLLOW CYLINDER TORSIONAL TESTING OF SOILS.

题名：	AUTOMATIC STRESS PATH CONTROL SYSTEM FOR HOLLOW CYLINDER TORSIONAL TESTING OF SOILS.
作者：	Wijewickreme-D; Uthayakumar-M; Vaid-YP
关键词：	SANDS-; DEFORMATION-; HOLLOW-CYLINDER-TORSIONAL-TESTS; COMPUTER-CONTROL-SYSTEMS; STRESS-PATH; STRESS-CONTROLLED-TESTS; STRAIN-CONTROLLED-TESTS; STRAIN-SOFTENING; SOIL-BEHAVIOR
摘要：	The deformation response of sands, which are often anisotropic because of their alluvial mode of deposition, under generalized field stress paths that involve principal stress rotation can be assessed systematically in a hollow cylinder torsional test. In this test, the specimen is subjected to four independently controlled surface tractions that allow loading under a prescribed stress or strain path. Pursuit of such stress or strain paths requires the use of simultaneous increments to more than one stress or strain component. A computer feedback control system for carrying out complex stress path tests in a hollow cylinder torsional device is described. As opposed to the generally adopted sequential loading and transducer signal readout methods, simultaneous control of all four external surface tractions and the synchronous digital readout of all transducers is carried out. This is accomplished by using four stepper motor-driven pneumatic regulators and a system of parallel analog-to-digital converters in which the number of converters equals the number of transducer signals monitored. The system allows the performance of totally stress-controlled or strain-controlled tests. In strain-controlled tests, more than one strain component can be positively controlled. The strain-controlling option permits the accurate capture of the postpeak strain softening characteristics of loose saturated sands by overcoming undesirable runaway strains inevitable in stress-controlled tests. Thus the behavior of soil can be assessed not only under controlled stress paths but also under controlled strain paths. The details of the control system are described, and its capabilities are illustrated by using experimental data from complex stress path tests.
总页数：	Transportation Research Record. 1994. (1432) pp1-8 (6 Fig., 13 Ref.)
报告类型：	科技报告