Dynamic Test Response of Ground Support Systems for Underground Excavations at the Walenstadt Testing Facility

Ground support systems must provide a safe environment to personnel while maintaining the excavation functionally to ensure continuous mine’s production. In addition, in burst-prone mines, these systems must be capable of resisting dynamic loading from mining induced seismic events. Hence, dynamic testing of the ground support system (combination of different reinforcement and retention elements) is required to assess the support system capacity and improve the performance of these elements under dynamic loading. During the recent years, Geobrugg has been working on improving load transfer element products (retention elements) by testing them in conjunction with different arrangements of reinforcement elements in a field-scale impact test facility located at Walenstadt, Switzerland. The test facility is composed of a double level platform of a square-shaped pyramidal truss geometry, in the upper-level housing a loading mass that drop from a height up to 5 m. The mass is guided by a central steel pipe and impacts a support system sample located at the lower level with an area of 3.6 m × 3.6 m, where the ground support system is installed. In this paper, six dynamic tests performed between 2018 and 2021 are considered. The arrangement, measurement, results, analyses, and some recommendations (conclusions) on the design of ground support under dynamic loads based on the tests performed are presented. The results of these tests have enabled to improve the understanding of the behaviour of ground support systems under dynamic loads. The main findings include a classification of the performance of mesh types used as load transfer elements and some recommendations on the design of ground support systems under dynamic loading. Among the recommendations, it is suggested the use of embedded meshes in shotcrete, and the use of load transfers materials (gap or damping materials, such as ‘gabions’) between the rock mass and the ground support system to improve the performance.