ABSTRACT:
This paper reports on the development and some initial results of modeling shotcrete test specimens prepared by the ASTM C-1550 procedure using the discrete element software package PFC3D.. PFC3D has been shown in this paper that it can be used to monitor the parameters of deformation, peak load, residual load, and the energy absorbed by the specimen during deformation, or specimen toughness. When weaker particles were mixed in with the stronger particles representing the aggregate-cementation matrix of the shotcrete, maximum values for peak load, residual load and specimen toughness (energy absorption during loading) developed at a mixing ratio of approximately 1:100 of weaker particles to the stronger particles, with a leveling off in these values at a mixing ratio of 1:20. This study has also shown that the micro-properties of the fundamental building block of PFC3D, the spherical ball, directly influence the macro-properties of the shotcrete test specimen.
1 INTRODUCTION
The Spokane Research Laboratory of NIOSH (U.S. National Institute of Occupational Safety and Health) is currently conducting a long-term study to examine the effectiveness of in-mine placement of shotcrete as a means to prevent rockfalls. One aspect of this long-term study is to construct numerical models in order to simulate shotcrete performance. The numerical models that are discussed in this paper were initially developed to model shotcrete test specimens prepared under the ASTM C-1550 test procedure. This ASTM test procedure utilizes a 75 mm thick by 800 mm diameter disk of shotcrete (ASTM, 2005). The shotcrete specimen is loaded at the center of the disk and has three points spaced 120º apart as reactions. The disk, during testing and failure, was numerically modeled with changes made to differing critical parameters of the shotcrete specimen. This paper reports on the development of the numerical models thus far.