# Research on Selection and Matching of Truck-Shovel in
## 3 Selection and Matching of Trucks  
### Efficiency Model of Truck-Shovel and Determination of Bucket-To-Capacity Ratio  
In the process of open-pit mine design, the general principle of truck-shovel selection is to decide the truck by shovel, which is often represented by the bucket-to-capacity ratio. The bucket-to-capacity ratio refers to the ratio between the volume of truck compartment and the bucket volume of the shovel, and the best bucket-to-capacity ratio is the value when the comprehensive working efficiency of the truck-shovel system reaches the maximum [22; 23; 24]. The working efficiency of the truck-shovel system is composed of two parts: the truck working efficiency and the shovel working efficiency. The truck working efficiency is the proportion of the transport time in the total cycle time, and the transport time is related to the transport distance of materials, while the total cycle time refers to the sum of the time needed to complete the material transfer, including loading, unloading, turning around and staying, in addition to the running time. The working efficiency of the shovel is the ratio of the effective working time to the total cycle time. The effective working time is the loading time. The total cycle time also includes the waiting time. For a particular mine, after deciding the type of shovel and transport distance, the operation time of the truck is fixed. The larger the bucket-to-capacity ratio, the longer the loading time of the truck, and the lower truck's working efficiency will be. On the other hand, the larger the bucket-to-capacity ratio, the longer the loading time of the shovel, the higher the shovel's working efficiency will be. It can be seen that the bucket-to-capacity ratio is negatively correlated with the working efficiency of the truck, and positively correlated with the working efficiency of the shovel. Therefore, to study the best bucket-to-capacity ratio of an oversized open-pit mine, the working efficiency of the truck-shovel should be comprehensively considered. Meanwhile, to reflect the influence of different processes on mine economic benefits, the unit production cost of each process is taken as the efficiency weight, and the efficiency analysis model of the truck-shovel system is established as follows:  
\[P=\frac{C_{t}}{C_{ts}}P_{t}+\frac{C_{s}}{C_{ts}}p_{s} \tag{4}\]  
where \(P\) is the comprehensive efficiency of the truck-shovel system, \(P_{t}\) is the work efficiency of trucks, \(P_{s}\) is the work efficiency of shovels, \(C_{t}\) is the unit cost of materials in the truck transport process (RMB/t), including the cost of the truck depreciation, maintenance, labor wages, fuel consumption, tires and other vulnerable and consumable parts; \(C_{s}\) is the unit cost of materials in the shovel loading process (RMB/t), including the cost of the depreciation, maintenance, labor wages, power consumption, teeth and other vulnerable and consumable parts; \(C_{ts}\) is the unit cost of materials (RMB/t) of the truck-shovel system, equal to \(C_{t}+C_{s}\). The above model can be further transformed into a truck-shovel efficiency model related to the bucket-to-capacity ratio:  
\[P=\frac{C_{t}}{C_{ts}}\left(\frac{t_{ty}}{T_{t}}\right)+\frac{C_{s}}{C_{ts}} \left(\frac{R\cdot t_{s}}{T_{s}}\right) \tag{5}\]  
where \(t_{ty}\) is the truck transport time (min); \(T_{t}\) is the cycle time required by the truck to complete the transfer of materials (min), including loading, transport, unloading, turning around and staying, etc. \(R\) is the bucket-to-capacity ratio; \(t_{s}\) is the loading time of the shovel's single bucket (min); \(T_{s}\) is the cycle time of the shovel (min), including loading time and waiting time. The meaning of \(C_{t}\), \(C_{s}\) and \(C_{ts}\) is the same as in Formula (4).