The Variation of the Angle of Internal Friction with Size Consist for Mechanically-Chipped Material

In order to improve aspects of materials handling in the rapid excavation process, research is underway to characterize the muck from mechanical tunnel boring machines. The specific project involves the correlation of the angle in internal friction, to the size consist, often termed gradation, of this mechanically-chipped material. Existing references demonstrate that this angle depends upon mineral type, and for a given mineral type upon size of particles. Particle shape is usually a function of mineralogical character and is not as important a parameter in influencing this angle. The project investigators have visited nine tunnels and have samples from seven rock types collected include granite, limestone, mica shist, sandstone, and shale. A facility for testing these specimens is being prepared and will consist of a flexible arrangement of 2.8 or 6-inch triaxial cells, pressure system, testing machine, and automated data collection system. The latter will insure the removal of personal bias from the data. Testing of samples can begin soon after a load cell is delivered.