1. Overview of sand gold deposit mining
     There are two broad approaches open pit mining and underground mining deposits in sand mining gold. Underground mining is used less in China and will not be introduced here.
     Open pit mining of sand gold is divided into three categories according to the mining machinery used:
     (1) Gold mining method (referred to as “ship miningâ€): In the early 1960s, China’s first gold mining ship was completed and put into production, which opened the historical prelude of the mechanization of gold mining in China. At present, China's gold gold has basically achieved mechanization. By 1989, China had 33 models of more than 130 gold mining vessels, which were used in more than 10 provinces (districts). The gold mining volume of gold mining vessels accounted for more than 80% of the production of gold.
     (2) Engineering machinery mining method (referred to as "machine mining"): refers to the use of mechanical shovel, bulldozer, scraper, loader and other construction machinery to excavate and load mineral rock, belt conveyor, car scraper, loader, etc. Transport machinery transports ore deposits by mining gold deposits. It is suitable for use in arid areas of China such as Inner Mongolia, Sichuan, Gansu, Qinghai and Xinjiang. The bulldozer mining method, the front end loader mining method, the scraper mining method, and the mechanical shovel mining method will be described below.
     (3) Hydraulic machinery mining method (referred to as “water miningâ€): It is a continuous production process that uses water guns, sand pumps and water pumps to complete the flushing, transportation, washing and tailings discharge operations in sequence using the same water flow.
     2. Gold mining ship and its production process
     The gold mining ship is a mining and mineral processing combined equipment. It is actually a punt, floating in or on the rivers and lakes. The ship is equipped with multiple bucket excavators, gold selection equipment and tailings discharge equipment, which can complete both mining and mineral processing operations.
     The mining process of the gold mining ship is shown in Figure 1. The ore excavated from the underwater bucket is sent to the washing cylinder screen through the loading funnel. The undersize product and water are distributed to the beneficiation equipment via a slurry distributor. The gravel and mud on the screen are transported by a belt conveyor to the goaf at the stern to form a gravel pile. The selected tailings are discharged into the tailings pile through the tailings tank or pipeline to the rear of the gold mining vessel.
figure 1 
     3. Gold mining method
     The mining of gold deposits begins with mineral deposits. The development is to place the gold mining vessel at a certain level, so that it is close to the ore body in a floating state, and create conditions for further mining. There are several ways to develop:
     (1) Foundation pit development method: Dig the pit of the gold mining ship along the boundary of the ore body or near the ore body. The size of the foundation pit is determined by the size of the gold mining vessel, and the depth is determined by the water depth required for the gold mining vessel to float. This method cannot be used when the underwater burial depth of the deposit is less than the minimum underwater burial depth of the sand mine defined by the draught condition of the gold mining vessel.
     (2) Dam development method: build a permanent or temporary retaining dam in the valley, increase the water level of the mining pond, and enable the gold mining vessel to enter the mining area.
     (3) Cofferdam development method: When the water level required for gold mining is small, it is not necessary to construct a high permanent dam, as long as the lower earth dam is built. This method is called cofferdam development. [next]
     (4) Independent level development method: In essence, the gold mining ship is built in the foundation pit, but it only mines the deep part of the sand mine. The alluvium layer in the upper part of the sand mine needs to be mined by mining equipment such as bulldozers and scrapers. This method is to divide the sand deposit into several stages, so it is also called the stage development method.
     4. Gold mining method
     Mining can be carried out after the development work is completed. According to the number of working faces in the mining pond and the moving direction of the gold mining vessel relative to the valley axis, the mining method can be divided into:
     (1) Single working face mining method: The gold mining ship is fully exploited in the full width of the mining area. During the mining process, the gold mining vessel always uses one for forward advancement. According to the moving direction of the gold mining ship, this method can be divided into vertical mining method and horizontal mining method.
     (2) Mining method of adjacent working face: The gold mining ship is alternately mined in several adjacent working faces that are associated with each other.
     (3) Joint mining method: the joint application of the above two mining methods.
     5. Bulldozer mining method
     The bulldozer is a self-propelled earthmoving machine that can perform all the processes such as excavation, transportation and loading. Bulldozers are both crawler and tire type. Track-type bulldozers are divided into three types: high-pressure bulldozers for rock stripping in stonework operations; medium-pressure bulldozers for general dozing operations; and low-pressure bulldozers for wetlands and marshes.
     The bulldozer directly pushes the topsoil from the mining site to the dumping site. The dump site is located on the side of the mine. In sand mining, bulldozers are generally used in conjunction with other equipment:
     (1) Bulldozer-one belt conveyor mining: Firstly, the ore body is divided into several mining areas, a loading funnel is set in the center of the mining area, the ore in the mining area is pushed to the funnel by the bulldozer, and the ore is transported by the belt conveyor. Give the washing equipment as shown in Figure 2.
figure 2 [next]
     (2) Bulldozers one by one mechanical shovel mining: bulldozers as the main mining equipment, mechanical shovel loading. The aim is to increase mining efficiency when mining thinner deposits.
     (3) Bulldozers one-and-a-half-shovel mining: This method has not been used in China, and it is used more abroad.
     (4) Bulldozers - Front-end loader mining: used in Inner Mongolia to turn to gold mines.
     (5) Bulldozer-one water gun mining: first push the ore to the appropriate location with a bulldozer, then rinse the ore with a water gun, and then send the ore to the concentrator by hydraulic transportation, as shown in Figure 3.
image 3
     6. Front end loader mining method
     The front end loader is a diesel-driven hydraulically operated device that can be transported and unloaded in addition to being shovel mounted. It is available in both crawler and rubber wheels. The crawler type can only be used for loading, and it can be used in extremely soft ground and uneven mining roads; the tire type can be self-loaded and transported, and it is flexible and flexible. It is an ideal mining equipment in sand gold mining.
     In the production practice, the front-end loader is used for self-loading only when the transportation distance is short. When the transportation distance is large, it is generally transported by automobile or belt conveyor.
     7. Scraper mining method
     The scraper is a revolving earth-moving machine that can comprehensively complete four operations of shovel, loading, transporting, and unloading rock. It is mainly used for large-scale ore mining operations in the middle distance. There are two basic types of scrapers for mining sand: crawler-type drag-and-scrapers, which consist of tractors, buckets and bucket operating mechanisms, which are generally used in small-scale stripping operations with short distances and soft ground; The dragging and scraping machine is composed of a buckling car, a bucket and a bucket operating mechanism, and is suitable for large-scale peeling operations with a long distance and a hard ground.
     Scraper mining method: When the local surface condition is good, and there is good road and the transportation distance is small, the scraper can be used to directly supply the ore to the mineral processing warehouse; when the thickness of the ore layer and the topsoil are not large The mining method of mining and stripping topsoil can be used, as shown in Figure 4. [next]
Figure 4
     8. Mechanical shovel mining method
     The mechanical shovel is a kind of machine with a shovel. There are two types of single shovel and half shovel. The single bucket shovel is divided into two types: the bucket steel connection and the flexible connection according to the connection mode of the bucket and the fuselage. The former is called a mechanical shovel or excavator, and there are also a part of the front and back shovel; the latter mainly has a shovel and a shovel. The multi-chopper is divided into a bucket shovel and a chain shovel.
     The forward mechanical shovel and the reverse mechanical shovel are used in China's gold mining. The schematic diagram is shown in Figure 5.
Figure 5
     In the actual production, there are single bucket shovel one-car mining method and single bucket shovel one belt conveyor mining method. Single bucket shovel - The advantage of the automobile mining method is that the transportation of soil and rock in the automobile transportation is large and flexible. The single bucket shovel belt transporter mining method is transported by belt conveyor, and the mining funnel and the ore feeding device shall be provided to ensure uniform supply to the belt conveyor. The ore mined by the bucket is directly discharged into the receiving funnel, and then the ore feeder uniformly supplies the belt conveyor, and the belt conveyor sends the ore to the concentrator.
     9. Hydraulic mechanized mining method
     The hydraulic mining method is a method for completing the gold-gold mining process by using high-pressure water sprayed from a high-pressure water gun. The water is pumped into the water gun by the pump, and the high-pressure water column emitted by the high-pressure water gun impacts the working surface, causing the ore to collapse and disintegrate to form a slurry and flow into the slurry pool along the transporting ditch, and then sent to the gold-selecting plant through the sand pump.
Production process of hydraulic mining method:
     (1) Topsoil stripping: When the topsoil layer is thick, it is removed by machinery (tractor, bulldozer, etc.), and when the topsoil layer is thin, it is removed by water gun impact.
     (2) Mine sand mining: that is, using the water gun high-pressure water column to impact the working surface, causing the ore to collapse and disintegrate.
     (3) Hydraulic transportation: The ore produced by the rushing is self-flowing into the slurry pool and then pumped to the gold selection plant.
     The hydraulic mining method is suitable for general cementation and less hard ore bodies, and requires the ore body to be buried shallow and the bottom plate to be flat. The method has the advantages of less capital investment, short construction period, high mining recovery rate, simple and easy maintenance of equipment, and the disadvantage is high power consumption. The sand pump conveying ore technology needs to be improved, so it is not widely used in China's gold mines.
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