The collision experiment between rolling stones of different shapes and protective cushion in open-pit mines

Though gravel cushions are used worldwide in open-pit mines and railway slopes to control the impact of rolling stones,no universal technical standards have been put in place to guide engineers in their correct design,and few laboratory test results are available with which to characterize collisions between rolling stones and a gravel cushion.We carried out a large number of experiments in which rolling stones made of the same material but differently shaped were dropped from various heights onto cushions with various particle sizes and thicknesses.We investigated the characteristics of the resulting collisions,and the relationships between coefficients of restitution(CORs)of blocks with different shape and release height H,cushion thickness h and particle diameter d are obtained through linear fitting method.Orthogonal testing reveals the relative influence of block shape,release height,and the particle size and thickness of the cushion on the collision characteristics,which can assist engineers in designing a gravel cushion suitable to the distribution and weathering characteristics of rolling stones in a specific area.

The energy distribution of a train impact process based on the active-passive energy-absorption method

This paper examines the energy-absorption characteristics of trains for active-passive safety protection.A one-dimensional collision-simulation model of traditional subway vehicles and active-passive safety vehicles was developed based on the multibody dynamics theory using MATLAB simulation software.The effectiveness of the simulation model was verified by scaled-collision tests.Then,the energy-absorption characteristics of traditional trains and the active-passive safety trains under different marshalling conditions were studied.The results showed that as the number of marshalling vehicles increased from 5 to 8,the energy absorption of interface 1 for the active-passive safety trains during the collision was 681 kJ,775 kJ,840 kJ and 901 kJ,and the physical compression of the interface of the head car of the active-passive safety trains was 619 mm,704 mm,764 mm and 816 mm,which was far below the maximum value of 1773 mm.The head car of the active-passive safety subway vehicles therefore had sufficient energy-absorption capacity.Finally,to find the maximum safe impact velocity of the active-passive safety trains,the energy distribution of the active-passive safety subway vehicles with 8-car marshalling at different impact velocities was studied.It was found that the safe impact velocity of an active-passive safety subway vehicle conforming to the requirements of the EN15227 collision standard reached 32 km/h,far exceeding the safe impact velocity of 25 km/h allowed by traditional trains,and representing an increase in the safe impact velocity of 28%.The total collision-energy absorption of the interface of the head car of the active-passive trains was 89.1%higher than that of the traditional trains at the safe impact velocity.The active-passive energy absorption method was therefore effective at improving the crashworthiness of the subway trains.