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What kind of gate is the coal mine horse head gate? — Black King Kong Report
In the complex system of coal mining, there is a "throat section" connecting the shaft and the bottom car yard — the shaft collar. Although it does not directly produce coal like the coal face, it is the core hub ensuring underground transportation, personnel passage, and equipment transfer. Its design and operation directly affect the efficiency and safety of coal mine production. Today, we will comprehensively understand the coal mine shaft collar from the dimensions of definition, structure, function, and classification.
1. What is a coal mine shaft collar?
The coal mine shaft collar refers to the special roadway structure connecting the shaft or inclined shaft with the bottom car yard roadway. It is named for its cross-sectional shape, which is often "wider at the top and narrower at the bottom," resembling a horse's head profile. It is located at the deepest part underground (in the vertical shaft scenario) or at the end of the shaft (in the inclined shaft scenario). One side connects the vertical or inclined shaft, and the other side connects the horizontally arranged bottom car yard. It is the "transition zone" between the surface and underground, shaft and roadway system, and also the "first transfer station" for underground material, personnel, and information flow.
It should be noted that the shaft collar is not an independent roadway but forms an organic whole with the shaft and bottom car yard. Its size and strength must strictly match the shaft diameter, car yard transportation capacity, and equipment specifications. It is one of the core links in the coal mine design phase.
2. The core structure of the shaft collar: must "bear weight" and "allow passage"
The structural design of the shaft collar must balance "load-bearing safety" and "transport convenience," mainly composed of the following three key parts:
Shaft neck section: the transition area connecting the shaft, also the "top load-bearing area" of the shaft collar. Because the vertical pressure transmitted by the shaft (such as the self-weight of the shaft wall and rock layer pressure) concentrates here, the shaft neck section is usually cast with reinforced concrete, with a thickness of 0.5-1.5 meters (adjusted according to shaft depth and geological conditions). In some complex geological conditions, anchor bolts and anchor cables are added to prevent rock deformation causing cross-section reduction.
Shaft bottom section: located at the bottom of the shaft collar, mainly functions to "accommodate shaft equipment" and "drainage." In the vertical shaft scenario, the shaft bottom reserves space for the shaft cage track (guiding the hoisting cage) installation and sets a drainage slope (generally not less than 3‰) to channel underground water to the drainage pump room, avoiding water accumulation that could soak equipment or affect transportation.
Passage section: the horizontal roadway part connecting the bottom car yard, serving as the "main passage" for materials and personnel. The cross-sectional size of the passage section must be determined according to the transportation equipment — if transported by belt conveyor, the cross-section must accommodate the belt width plus maintenance space; if by mine car, it must ensure a safety clearance of more than 0.8 meters on both sides when the mine car passes. Additionally, the passage section will set up refuge chambers (for personnel to avoid mine cars), signal devices (to coordinate transportation scheduling), and other auxiliary facilities.
3. The four core functions of the shaft collar
The shaft collar is called a "hub" because of its irreplaceable four functions, covering the entire coal mine production process:
Coal transfer "transfer station": Coal mined underground is transported by mine cars or belt conveyors from the bottom car yard to the shaft collar, then transferred to the surface by the hoisting cage (vertical shaft) or winch (inclined shaft) in the shaft. The shaft collar must ensure "seamless connection" in coal transfer to avoid coal blockage or material jamming.
Personnel and equipment "entry and exit passage": Underground workers commuting and large equipment (such as shearers, scraper conveyor parts) entering and maintenance all need to pass through the shaft collar. For example, when the vertical shaft hoisting cage stops at the shaft collar, personnel can directly enter the passage section from the cage, and equipment is hoisted to the car yard through a dedicated lifting hole (set at the top of the shaft collar).
Underground ventilation "key node": Continuous ventilation is required underground to dilute gas and dust. The shaft collar, as the connection point between the shaft and roadway, is a "must-pass" for the ventilation system. Wind doors or windows are set inside the shaft collar to regulate airflow distribution, ensuring sufficient fresh air for each working face.
Emergency refuge "safety barrier": In case of gas outburst, water inrush, or other accidents underground, the shaft collar can serve as a temporary refuge area — its sturdy concrete structure can withstand certain impact pressures, and its connection to the shaft provides an emergency escape route for personnel. Some mines also set emergency supply storage points near the shaft collar, storing self-rescue devices, food, and other materials.
4. Main classifications of the shaft collar
Different coal mines have different shaft types and transportation needs, so the shaft collar is correspondingly classified, commonly into the following two types:
By shaft type: vertical shaft collar and inclined shaft collar
Vertical shaft collar: used for vertical shafts, structured as a "vertical shaft + horizontal passage" combination. It must focus on vertical load-bearing. The depth of the shaft bottom section is usually 2-5 meters (determined by cage length), commonly found in deep shaft coal mines (shaft depth over 500 meters).
Inclined shaft collar: used for inclined shafts (generally 15°-30° inclination), the structure aligns with the slope of the inclined shaft. The passage section must be equipped with anti-slip sleepers (to prevent mine cars from sliding), and the shaft neck section must adapt to rock pressure in the inclined direction. It is common in shallow shafts or coal mines with shallow coal seam burial.
By purpose: main shaft collar and auxiliary shaft collar
Main shaft collar: specifically used for coal transfer, the passage section directly connects with the main shaft hoisting cage. The cross-section is larger (to accommodate coal transportation equipment) and includes a coal bunker funnel (for temporary coal storage) to reduce transfer waiting time.
Auxiliary shaft collar: mainly used for personnel, equipment, material transportation, drainage, and ventilation. It has more comprehensive functions, with multiple branch passages (such as roadways to pump rooms, substations, car yards) and reserves sufficient maintenance space for equipment loading and unloading.
5. Design and construction of the shaft collar
The design and construction of the shaft collar must strictly follow the "Coal Mine Safety Regulations," with core points including:
Geological Adaptation Design: First, determine the properties of the rock layers at the Matoumen location through drilling (such as hardness and fracture development). If encountering soft rock layers or aquifers, the "support first, then excavation" method (such as pipe roofing support or freezing method) must be used to prevent collapse or water seepage.
Accurate Load Calculation: Consider vertical shaft pressure, lateral rock pressure, dynamic loads from transportation equipment (such as impact forces when mine cars pass), ensuring the concrete strength grade is not lower than C30, and adjust the reinforcement ratio according to the load magnitude.
Construction Precision Control: Use smooth blasting during excavation (to reduce rock disturbance), control cross-section dimension errors within ±50mm; during concrete pouring, vibrate to ensure compaction and prevent defects like honeycombing or rough surfaces. After pouring, cure for more than 28 days to ensure strength standards are met.
6. Safety Management of Matoumen
As a key underground facility, Matoumen requires three daily maintenance tasks:
Regular Monitoring: Use total station to monitor cross-section deformation (to prevent cross-section reduction caused by rock extrusion), use piezometers to monitor water levels in the shaft section (to avoid water accumulation), at least once a month;
Explosion-Proof and Corrosion Protection: Electrical equipment inside Matoumen (such as signaling devices and lighting) must meet explosion-proof standards; metal components in the shaft section (such as tank roads) must be regularly coated with anti-rust paint to prevent corrosion;
Cleaning and Unblocking: Timely clean coal dust and debris in the passage section to ensure smooth transportation; regularly inspect drainage pipes to prevent blockage and water accumulation.
