A new mini-grating absolute displacement measuring system for static and dynamic geomechanical model tests

In this paper, a mini-grating displacement measuring system is developed for geomechanical physical model tests. This system consists of a portable multi-channel grating data acquisition instrument, a grating ruler, a micro multi-point extensometer, and other related accessories. The motherboard of the portable multi-channel grating data acquisition instrument uses a self-developed circuit board and all channels can collect high-speed and high-precision grating displacement signals. The micro multi-point extensometer has advantages of micro-flexibility and small interference in physical model tests. Embedded measuring points in tunnel surrounding rock connect with the grating ruler which is fixed on an independent frame outside of steel wires and connects to the data acquisition system with wire lines. The system is applied to a static and dynamic geomechanical model test on a tunnel. Testing results prove that the system can be satisfactorily applied in geomechanical model tests.