Utilization of pneumatic artificial muscles on a direct shear test setup

Abstract

A pneumatic artificial muscles, which is basically a type of actuator that contracts under pressure while exerting a tensional force in the axial direction, possesses several advantages, such as high power/weight ratio, ability to be used in harsh environment etc., over conventional methods of actuation. Since the development of pneumatic artificial muscles, they have been employed frequently in robotic applications and medical devices. However, very few studies utilized this innovative technology in civil engineering problems. In this study, the possible use and feasibility of pneumatic artificial muscles in geotechnical applications have been investigated. Design of a largescale direct shear apparatus that is capable of conducting direct shear and direct shear interface tests has been proposed to evaluate the utilization of PAMs in geotechnical applications . The direct shear test has been one of the most widely employed methods in determination of the shear strength behavior of soils and interfaces due to its relative simplicity compared to other shear strength experiments. The limitations of the apparatuses necessitate the use of a large-scale device in order to perform tests on soils containing larger particles and interfaces. In the proposed design, PAMs are used in the normal load application system, which can exert a normal stress without a reaction frame and in a uniform manner. The utilization of the muscles as a cyclic actuator for the interface tests are also described in detail. As an outcome of this thesis, PAMs may be employed in geotechnical applications especially in laboratory applications as the muscles can exert higher forces than hydraulic and pneumatic cylinders of equal volume and can be mounted easily without further mechanical parts to other devices, which results in the possibility of extensive usage in several laboratory applications.