Design and Fabrication of a Multiple Lever-Arm Creep Testing Setup for Rocks

ABSTRACT Rock exhibits creep behavior under prolonged loading environment. The characterization of rock creep is essential to ensure the long-term stability of the structure, which is primarily accomplished through laboratory creep tests. By definition, creep tests require applying constant stress. However, the constant load technique is widely used because of the ease of maintaining load rather than stress. There are numerous techniques to maintain a constant load. This study critically analyzed all such techniques and discusses the suitability of each creep frame on testing rocks. With simple, compact, and low-cost design approach, a multiple lever-arm creep testing frame is developed in-house for testing creep in rocks. The size of the creep frame is greatly reduced by introducing a three-tiered lever arms. By reducing the size, the machine becomes compact and can be operated without the help of any mechanical system, reducing the operation cost. A hydraulic piston is used in series with the lever arm to cushion and counter load loss associated with the technique. Multistage creep tests are performed using the installed creep frame on gypsum samples. During testing, the applied load is verified using a load cell, which indicates a constant loading. A good comparison between the creep curve and the modified Nishihara model is observed and a nonlinear viscous behavior is observed at high pressures. The test results indicate the machine’s efficiency, simplicity, and ability to perform creep tests and subsequent measurement of the high creep strain. This manuscript will educate and guide researchers in selecting the appropriate creep frame based on individual requirements and corresponding detailed design and fabrication of the creep frame.