High impact shovel loading operations expose the truck operators to whole body vibrations (WBV), exceeding the ISO exposure limits resulting in long term disabilities and health issues. With dynamic force resulting from the gravity dumping of material during each shovel pass being the main cause for these high frequency shockwaves, this work focused on developing a robust mathematical model, using Lagrangian mechanics, for capturing and examining the force on truck surface during multi-pass shovel loading process. The model was tested through experiments for the case where a CAT 793D dump truck was loaded by a large capacity P&H 4100 XPC cable shovel. Maximum impact force amplitudes of 692 kN and 622 kN, were recorded for the first and second shovel passes, respectively. Moreover, a cushioning effect of 10.12% was observed during the second shovel pass, which significantly reduced the impact on the truck bed surface. With such deeper understanding of generation and propagation of the impact force, solutions can be developed to eliminate, or at least reduce, the force magnitudes to keep them within appropriate levels. This work will serve as a stepping stone towards the development toof technologies to enhance the health and safety of truck operators.