Large dynamic direct shear machine for geosynthetic clay liners

Patrick J. Fox, Christopher J. Nye, Todd C. Morrison, Jay G. Hunter, James T. Olsta

Research output: Contribution to journalArticlepeer-review

33 Scopus citations

Abstract

A large direct shear machine for static and dynamic shear strength testing of geosynthetic clay liners (GCLs) and GCL liner systems is described. The machine tests rectangular GCL specimens measuring 305 × 1067 mm and has a maximum shear displacement of 254 mm, which is sufficiently large to allow for the measurement of residual or near-residual shear strengths in most cases. The basic design concept for the device is to shear a GCL specimen between a bidirectional pullout plate and a stationary reaction plate, each covered with an aggressive gripping surface. The pullout plate is driven by a computer-controlled hydraulic actuator. The maximum normal stress is 2000 kPa, the maximum shear stress is 750 kPa, and the shearing system is capable of imposing general stress-controlled or displacement-controlled dynamic loading to a test specimen. The actuator has a maximum frequency of 4 Hz for sinusoidal loading with a displacement amplitude of 25 mm. The maximum displacement rate for burst loading (i.e., single thrust) at zero force is 1 m/s. The paper describes four main components of the machine: (1) the shearing system; (2) the normal stress and vertical displacement measurement system; (3) the specimen hydration system; and (4) the process control and data acquisition system. The performance of the machine is illustrated using displacement-controlled test data for the static and cyclic internal shear strength of a hydrated needle-punched GCL.

Original languageEnglish (US)
Pages (from-to)392-400
Number of pages9
JournalGeotechnical Testing Journal
Volume29
Issue number5
StatePublished - Sep 1 2006

All Science Journal Classification (ASJC) codes

  • Geotechnical Engineering and Engineering Geology

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