This paper presents the results of a research study carried out to investigate the performance of the pentice structure at an underground mine in NSW during the extension and equipping of a haulage shaft by Macmahon under high-speed impact loading caused by the potential projectiles falling from the surface. This assessment will allow the structure to comply with AS 3785.5 for “Headframes” (Australian Standard, 1998). The pentice structure is installed 1000 m below the surface in a 4.268 m diameter shaft at the considered underground mine. The objective of the pentice is to allow Macmahon construction and shaft sinking crews to work in the shaft without any risk to their safety. The pentice structure includes a number of steel boxes 1-m high that are filled with high yielding foaming grout Tekseal from Minova Australia Pty Ltd. The major aim of this investigation is to evaluate the capacity of the existing pentice to resist high-velocity impacts and to develop a high-performance protective system which is capable of absorbing energy and terminating large projectiles falling from a height of 1000 m. High-fidelity physics based finite element models for the mine pentice were developed to find a satisfactory solution to protect workers 1000 m below the surface from potential falling projectiles. It is established that the existing level 11 pentice structure is not capable of stopping the projectiles dropping from a height of 1000 m. Several high-performance protective solutions for strengthening the pentice against impact loads were proposed and evaluated numerically. As the final design, two-level protection is designed that includes the 9 level and 11 level pentice protective structures. The models of the 9 level pentice and the 11 level pentice are evaluated for the relevant impact loads. It is found that the new 9 level pentice requires an additional layer of the railway concrete sleepers along with the high-strength steel cover plate to provide adequate protection and terminate the falling projectiles. The supporting frames for the 9 level and 11 level pentice structures are designed using the dynamic reaction forces transferred from the pentice boxes. The developed two-level pentice protective system has proven to provide high level of protection against high-speed falling projectiles for workers performing shaft sinking duties in the shaft below.