Abstract: To study the excavation unloading response (EUR) of the surrounding rock of grouting curtain for vertical shaft, a triaxial excavation unloading test was conducted using fractured rock-like sample of vertical shaft grouting curtain (VSGC). The strain response of the VSGC sample was measured during the simulated excavation uloading process. Furthermore, the cracking mode and damage radius of the VSGC samples after excavation unloading were analyzed using CT scanning. Results indicate that the strain response of the VSGC sample after excavation unloading decreases rapidly with the increase of radius, with the strain during the excavation unloading stage dominating the total strain. Additionally, with the deformation of the grout stone being greater than that of the rock-like matrix. Moreover, the VSGC sample filled with cement grout exhibits has stronger deformation resistance than VSGC sample filled with clay cement grout. Hence, both the tangential and radial strains at the same radius in the sample filled with cement grout are significantly smaller than those sample filled with clay cement grout. Furtherly, the initial stress level significantly impacts the EUR of the VSGC sample, and the higher the stress level, the more severe the deformation during the excavation unloading stage, and the higher the proportion of strain during the excavation unloading stage. Finally, the VSGC samples filled with cement grout are prone to cracking along the contact surface between the grout stone and the prefabricated cracks, with the damage radius being 1.2 to 1.5 times the excavation radius. On the other hand, the cracking behavior of VSGC samples filled with clay-cement grout is complex, and the damage radius ranges from 1.5 to 2.0 times the excavation radius. The research findings can offer technical insights for designing grouting curtain for vertical shaft in the prevention and control of shaft water hazards.

Key words: deep mining, vertical shaft, grouting curtain, excavation unloading, strain response