A method to identify the position of fracture surface in a rock slope based on multi-point extensometer monitoring

The multi-point extensometer is widely used to measure the displacement of geological bodies. In this work, we proposed a simple mathematical approach to directly identify the position of the major fracture surface in a slope based on the data from multi-point extensometers. By comparing the cumulative absolute displacement per unit length between two adjacent gauging points of each multi-point extensometer, the most likely zone of the fracture surface is determined preliminarily. Then, selecting any three adjacent multi-point extensometers across a fracture zone as the reference fracture surface, and assuming there is a same displacement catastrophe, thus the equations relating to the coordinates of the three intersection points between the multi-point extensometers and the fracture surface can be obtained according to the characteristic of displacement distribution. On the basis of the solved coordinates of the two endpoints of the reference surface, the coordinates of the intersection point between the fracture surface and the displacement extensometer are determined step by step. Finally, the entire fracture surface can be deduced by connecting all the solved intersection points. In addition, a real slope monitored by multi-point extensometers and simulated by the finite element software ABAQUS to verify the feasibility and rationality of the proposed method. The adaptations and limitations of this method are also discussed. The results show that the proposed method can effectively detect the position of the internal fracture surfaces in a slope.