# Influence of Crushed Rock Properties on the Productivity of a Hydraulic Excavator
## 1 Introduction
Based on blasted rock fragmentation data obtained by using image processing software and dependencies of the bucket fill factor and cycle time of the excavator on these data, the authors in [25] also concluded that excavator productivity directly depends on the granulometric composition of rock. By analyzing the particle size and ratio of bucket volume to truck capacity, the authors in [26] concluded that these properties affect the crowding efficiency, fill factor, and swell factor. Further, the blasting efficiency and operator competence were found to be effective parameters. In contrast to other research, in [27], the authors investigated the relationship between fuel efficiency (kg/l) and productivity (m\({}^{3}\)/h) by monitoring two independent variables, engine speed and bucket cut depth (BCD), in an excavator working with loose dry sand. It has been found that BCD and engine speed can affect the fuel efficiency and productivity of a hydraulic excavator in a way that a half-filled bucket (50% BCD) can have an effect of 30% higher productivity, 24% saving on fuel (l/kg), and 62% more sand moved per hour, in addition to the amount of fuel consumed. Except for granulometric composition, the productivity of the excavator will indubitably depend on the water content of the material. A simple explanation of this is the fact that if the quantity of water is greater, the bucket filling factor will be lower because part of the constructional bucket volume is filled by water [28]. Furthermore, the moisture in some materials causes the appearance of stickiness, resulting in a longer dumping time of the bucket that is longer than the cycle time of the excavator. On the other hand, the moisture in coherent material directly influences the increase in the bucket fill factor. It is clear from the presented literature review that the productivity of the excavator will strongly depend on the bucket fill factor, and one of the properties with a major influence on it is the particle size distribution of the material being manipulated. The swell factor is also the consequence of the particle size distribution of the material, and it can be hypothesized that there is a connection between them. Besides, the water content in coherent material will increase the fill factor in a way that it will increase the angle of repose of material, which results in expansion of the heaped volume of the bucket. It can be assumed that a higher material angle of repose will cause an increase in the heaped bucket volume and consequently, the productivity of the excavator. This work aims to determine the strength of impact of the angle of repose of crushed rock material on excavator productivity and to investigate the connection between the bucket fill factor and swell factor of the material being manipulated. Analysis of the simultaneous effect of the angle of repose, slewing angle, and particle size distribution of the material on hydraulic excavator productivity will also be conducted. Calculations are based on field measurements for determining the volume of the bucket load and the duration of the excavator loading cycle as the main factors that determine the productivity.