Large Dynamic Direct Shear Machine for Geosynthetic Clay Liners
Fox, PJ
Professor, Department of Civil and Environmental Engineering and Geodetic Science, Ohio State University, Columbus, OH, 43210

Nye, CJ
Graduate Research Assistant, Department of Civil and Environmental Engineering and Geodetic Science, Ohio State University, Columbus, OH, 43210

Morrison, TC
Staff Engineer, Barr & Prevost, Columbus, OH, 43231

Hunter, JG
Civil Engineering Shop Manager, Department of Civil and Environmental Engineering and Geodetic Science, Ohio State University

Olsta, JT
Technical Manager, CETCO, Arlington Heights, IL, 60004

(Received 26 December 2005; accepted 22 May 2006)

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.

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Author Fox PJ, Nye CJ, Morrison TC, Hunter JG, Olsta JT Title Large Dynamic Direct Shear Machine for Geosynthetic Clay Liners Symposium , Committee on