Ways to improve the efficiency of excavator loading in open pit mines

Haikou Phosphorus Industry Co., Ltd. is a modern open-pit phosphate mining and mining enterprise with abundant phosphate resources. The reserves are 182,229,200 tons, and the mining area is 12.74 km2. It consists of 4 mining areas, and the total stripping capacity of the whole area is 24,724. 90,000 m3, with the increasing production volume, the current production stripping capacity is 9 million m3/a, and the original mining capacity is 2.24 million t/a.

The phosphate deposit is located at the bottom of the Cambrian lower system and above the Sinian system of the Dengying Formation, which is a large-scale sedimentary layered phosphorite deposit. The main phosphorus-bearing layer has two layers, namely the upper phosphorus layer and The lower phosphorus layer has a sandwich layer of phosphorus-bearing sand dolomite . The production process is perforated blasting (for part of shale and primary ore) → mining → transportation → washing (selection) processing → grading → transportation, using the single-wall ditch from the top to the bottom, and stratifying and transporting along the horizontal layer. The shovel equipment mainly consists of two 6.7m3 Komatsu PC1250-7 backhoes, one 4.1m3 Komatsu PC750-7 positive and reverse shovel, and three 4m3 Volvo EC700BLC backhoes. It is used for the separation of the interlayer between the dolomite, the soil layer and the upper and lower phosphorus layers in the upper phosphate rock layer and the shovel loading of phosphate rock. The transport equipment mainly consists of 30 Volvo A40D (E, F) articulated dump trucks with a load of 37 to 39 tons for the transportation of strippers and phosphate rock. Under the condition of constant production equipment and geological conditions, through the analysis of the factors affecting the efficiency of the excavator shovel, the measures to improve the efficiency of the excavator shovel are formulated, and the amount of self-distribution is reduced, the production cost is reduced, and the sustainable development of the mine is guaranteed.
Analysis of Factors Affecting Shovel Efficiency of Excavator
The excavator production efficiency refers to the earthwork quantity Q calculated by the excavator excavating from the working surface and loading into the transport vehicle or unloading into the mound in unit time. The calculation formula is

Where q is the bucket volume, m3; Kz is the bucket fullness coefficient, 0.75~1.05); Kw is the soil excavation resistance coefficient, 0.65~1.0; Kt is the time utilization coefficient, 0 .7～0.85; Ks is the soil loose coefficient, 1.08～1.45; n is the number of theoretical working cycles per hour, n=3600/T, T=t1+t2+t3+t4+t5, T is For each working cycle time, s, t1, t2, t3, t4, and t5 are the excavation time, the time required for the full load bucket to rotate to the unloading, the unloading time, the time when the empty bucket is turned to the working surface, and the bucket descends to the working surface. Time, s[1].
From this, the factors affecting the efficiency of shovel loading in open pit mines are as follows: 1 the number of working cycles per hour n, its value and technical performance of the excavator, the operating level of the excavator driver, the blasting effect, the nature of the rock or soil, the shovel Matching, excavator loading method, etc.; 2 bucket filling factor Kz, which is the ratio of volume and bucket capacity of loose ore in the bucket, and the driver's operating skill level, blasting effect, ore rock or soil properties Relevant; 3 soil excavation resistance coefficient Kw, considering the influence of soil excavation resistance on the number of working cycles, which is related to the blasting effect, the nature of the rock or soil, the structure of the bucket, the excavation trajectory, the shape of the cutting, etc.; Coefficient Kt, considering the time lost for maintenance, repair and movement of the equipment; 5 Soil looseness coefficient Ks refers to the ratio of the volume of the material after the excavation to the original compact volume, which is related to the material grade and the bucket volume. Geological conditions (mineral structure, mineral or soil properties) and excavator parameters are objective and cannot be changed, while production organization management is open-pit mining technology, and development of working surface parameters (where the working step height is too high or too low will affect Shovel loading efficiency, especially when the working step height is too low, will reduce the loading efficiency by 15%~30%. [2], the work site layout and loading mode affect the excavator shovel loading efficiency; the blasting effect is not good, the blockiness is uneven The explosion pile is scattered, the bulk and the bottom are more increased to increase the loading time, reduce the full bucket coefficient, increase the soil excavation resistance coefficient, etc.; the vehicle shovel is unreasonable (the vehicle is insufficient), the phenomenon of the excavator and other vehicles appears, and the cycle time is increased; The operation level of the excavator driver is different. Under the same equipment and similar shovel loading conditions, the loading speed and time are different, the number of working cycles per hour, the bucket filling factor, the soil excavation resistance coefficient, and the time utilization coefficient are different. The production volume varies greatly; the technical condition of the excavator has a large impact on productivity, such as the engine power is reduced, the hydraulic system pressure is reduced, causing the excavator In summary, production organization management, blasting effect, vehicle shovel matching, excavator driver's operating level, excavator technical status and maintenance quality are the main factors affecting the excavator's shovel efficiency.
2 measures to improve the efficiency of the shovel
2.1 Organization Management
Strengthen the quality of management personnel, improve the management level of the organization, and optimize the mining plan. The steps are divided according to the elevation level, the design height is 10m, the width of the mining width is 8~10m, the minimum working plate width is 20m, the safety platform is 6m wide for each step, and the 8m wide cleaning is performed every 2~3 steps. Platform, rest step slope angle is 65 °. The Komatsu PC1250-7 backhoe has a maximum excavation depth of 7.9m, and the Volvo A40D (E, F) articulated dump truck with the excavator is 3.55m high. According to the mining parameters, the development is divided into 2 times, and the height of each step is 5m. Dump truck loading method: 1 bicycle loading method, limited by the loading place of the stope, one car is full after driving out, another car is driven in or back to the place to load the car; 2 double car loading method, among them When one car is loaded with soil, another car is driven in or back to the location at the same time; 3 double loading method, 2 dump trucks are respectively parked on the circular arc of the excavator bucket unloading, excavator Fill one, and then install one [4]. Excavator loading method: 1 flat loading, excavator and dump truck stop working on the same level of ground, the excavator driver may not be able to see the dump truck compartment, easy to install bias; 2 flat (high) loading, The excavator stops at a high place, and the dump truck stops at a low place. According to the amount of earthwork and the height of the step design, the height of the flat (high) platform (5m) of the excavator is determined. The position of the excavator is adjusted at any time, and two lanes are set. The car is just full and can be loaded with a car. The measured method and efficiency of the 2# Komatsu PC1250-7 backhoe excavator loaded with the Volvo A40 articulated dump truck are shown in Table 1. The operating efficiency and stripping capacity of the two PC1250-7 backhoe excavators are shown in Table 2. It can be seen that: 1 double-disc loading method is more efficient than double-vehicle loading method, double-vehicle loading method is more efficient than bicycle loading method; 2 flat (high) loading is more efficient than flat loading; 3 excavator The small turning angle is more efficient than the large turning angle; 4 short working cycle time of the excavator is more efficient than the long working cycle time. Therefore, effective ways to improve the efficiency of excavator loading in open pit mines: 1 full load, increase the degree of full bucket; 2 under the condition of ensuring work safety, the parking position of the vehicle should be beneficial to shorten the working cycle time (excavator excavation, bucket steering Unloading point, bucket alignment and unloading, and emptying of the bucket back to the working surface to the excavation point 4 process time), making full use of the waiting space to prepare for loading (loose, rewind and clean the working face) , select the unsuitable large block, etc., and pour the ore of the working face to a position close to the parking lot of the car. The angle of rotation of the excavator is not more than 90°, which reduces the angle of rotation of the excavator; 3 reduces the non-working time and improves the time utilization rate. 4 Develop a reasonable development design and production organization, set the appropriate level of flat (high), and try to use the flat (high) platform double loading method.

2.2 Suitable blasting method

Select appropriate blasting parameters; select the detonation position reasonably; use multi-point detonation to increase the parameters of the blast stress wave and increase the degree of rock fragmentation; use segmented charge to make the middle and upper parts of the step can be broken to varying degrees. Reduce the large block formed by the collapse; use the millisecond blasting to reduce the damage to the unexploded rock mass, reduce the block rate and the unit consumption of the explosive, so that the shape and size of the explosion pile is beneficial to the safe and efficient operation of the excavator, and improve the shovel loading, Transportation equipment efficiency is about 10% to 15% [5]; in addition, sufficient bursting volume is another important aspect to ensure the maximum efficiency of the excavator.

2.3 car shovel matching

The shovel matching is the matching between the volume of the dump truck and the volume of the excavator bucket. The principle of determining the car and shovel in the open pit mine is centered on the shovel. The capacity of the dump truck should be an integral multiple of the bucket capacity of the excavator [4]. .
The external drainage distance of the mine is 1.5~2km, the internal drainage distance is 0.5~1km, the Komatsu PC1250-7 backhoe excavator has a bucket capacity of 6.7m3, the normal loading volume is 5.7m3, Volvo A40F The articulated dump truck weighs 39t, and the normal loading capacity of the car is 17m3. It adopts the flat (high) double-disc loading method. When the distance is 1.5~2km, according to the dump truck running cycle time 11.3~14.4min/趟, the excavator is full of dump trucks with 3 buckets. It is most reasonable to configure 5 dump trucks; when the distance is 0.5~ 1km, according to the dump truck running cycle time 6.9 ~ 8.4min / 趟, the excavator is full of dump trucks with 3 buckets, the most reasonable configuration of 4 dump trucks, guide the dump truck to the position of the excavator bucket easy to flip, shorten Excavator waiting time, improve the effective working time of the excavator, and give full play to the excavator and dump truck capacity.
2.4 Safety Education and Skills Training
First, strengthen safety training, strengthen "three-level" safety education and post safety education, and improve the safety awareness of excavator drivers. Secondly, for the excavator driver to carry out daily professional skills training, post training, skill competition, so that the excavator driver masters the equipment operation skills, continuously improve the driver's operating technology level, give full play to the equipment ability; finally, the excavator driver is recurring Ideological education and professional ethics training, carry out regular job evaluation, final elimination mechanism, strengthen work responsibility, and give full play to the enthusiasm and creativity of drivers.
2.5 Excavator Maintenance
Equipment failure is one of the main factors affecting production efficiency. Daily maintenance work is done in place, timely maintenance, real-time maintenance, to ensure the quality of fault repair; through the analysis of equipment operating conditions, to provide maintenance warning, targeted preventive maintenance, Thereby reducing the maintenance cost; strengthening the maintenance of the equipment to ensure that all parts of the equipment perform well,
High equipment integrity rate.
3 Conclusion
Through the analysis of the influencing factors of the excavator shovel efficiency, under the condition of constant production equipment and geological conditions, strengthen the organization, coordination and management of each process, give full play to the capabilities of its own personnel and equipment, and adopt the flat (high) platform. Loading method and appropriate blasting method, reasonably match the shovel, strengthen the safety education and skill training of the excavator driver, strengthen the maintenance of the excavator, and improve the shovel loading efficiency of the open pit mine.

As the manager of production and equipment, we need to continuously learn advanced management concepts, management experience and management skills, timely understand the equipment, master the equipment dynamics, and in-depth production of the first line to find problems and solve problems, in order to truly make the equipment to the maximum capacity for the mine Providing strong support for cost reduction and efficiency.
references
[1] Wuhan Institute of Water Conservancy and Electric Power, North China Institute of Water Conservancy and Electric Power. Construction Machinery User Manual [M]. Beijing: Power Industry Press, 1980.
[2] Wang Weiping. The influence of step height on the economic benefits of open pit mines [J]. Metal mines, 1994 (10): 8-9.
[3] Huang Shaowei. Preliminary study on ways to improve the efficiency of shovel loading and transportation in stope [J]. Jiugang Technology, 2013 (2): 113-117.
[4] Li Hong. Excavator operation and maintenance [M]. Beijing: China Labor and Social Security Press, 2004.
Article source: "Modern Mining"; 2016.10;
Author: locking mechanism in; YPC Co., Ltd. Haikou phosphorus;
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