The top management method is to retain the pillars, and the second is to use bolts. The stability of the surrounding rock itself is an important aspect.
1) Retaining column support
When the poor stability of roof rock, the pole can be mounted in the roof rock in order to increase its stability. When the top plate is partially unstable, the pillars can be left in a local area. When the roof of the mine encounters a fault or a large span, a temporary pillar can be reserved. [The pressure is relatively large near the lower part of the mine. Therefore, the first row of pillars is generally left in the lower part of the mine. The spacing of the pillars is 5 to 8 meters, and the size of the pillars is φ 3 to 7 meters. 〕
2) Bolt support (you can also use wooden pillars, should not specifically mention the type of bolts, only mention the name of the bolt and the role of the bolt)
The bolt is a new kind of bracket. It uses the rod that is driven into the rock to strengthen the rock. Its advantage is that the installation pole can work quickly and in time, and the support process can be mechanized. Low cost, low labor intensity and increased production capacity. It occupies a small space and is good for ventilation. At the same time, the cost of transporting, loading, unloading and storing the stent material can be reduced. There is no danger of fire, and because of its many advantages, it is widely used at home and abroad.
Many different types of anchor, there mortar anchor, slotted metal wedge anchor, expansion shell bolt, resin bolt, now applied and a friction bolt truss bolt.
The bolt has a good effect, but the structure is complicated, the processing cost is high, and the metal ore is applied more.
3) Mortar anchor
The mortar anchor is to make a good eye on the top plate, load the waste steel wire rope, and then pour into the cement mortar to form the pole support. The advantage of mortar anchors is that they can be used in soft rock and fractured rock formations; the cost is also relatively low. The disadvantages are: slow consolidation and poor resistance to blasting vibration.
4) resin bolt - which is a resin, initiator, and filler hose material enclosed or aluminum tube, is inserted on the head of the bolt bore, when in the end portion, the rotary bolt stirring and mixing, the resin and initiator to two The chemical reaction combines the anchor head with the rock formation.
In recent years, countries such as France, the United States and West Germany have vigorously developed resin anchors. Anchored block of this kind of anchor, anchoring force
Large and resistant to shocks. But the cost is high. The source of the material is subject to certain restrictions. Some current coal mine more applications.
(Common resins are epoxy resins and polyester resins)
5) Friction type anchor (also called slotted anchor or slotted anchor)
The United States proposed this idea in 1972. Batch production began in 1977. (The study was completed in 1973, is Scott of the United States)
This kind of anchor is made by twisting a steel plate into a tube that is not closed. It can also be made by drawing a steel pipe. That is to say, the anchor is a steel pipe that cuts a slit along the entire length of the rod.
The anchor has a diameter of 38 mm, a wall thickness of 2.3 mm, and a slit width of 12.7 mm, and the steel pipe is made of a molded steel material having a strength of 4,900 kg/cm 2 . The hole diameter of the anchor rod is φ=35mm. When installing, the anchor rod is driven into the hole by the impactor, so that the seam portion of the steel tube is closed, so as to be in close contact with the hole wall, and a considerable frictional resistance is generated. Therefore, this anchor is called a friction bolt. According to the measurement, the anchoring force per m of the anchor is 2.5 to 5 tons.
The advantage of the anchor rod is that it can be used in soft rock, and can function in time, is convenient to install, requires less labor, and has low cost. At the same time, it is anchored in full length, so the anchoring force is relatively large.
6) Anchor truss
Anchor truss is a new method of roof support developed in recent years. The practice of applying anchor trusses from home and abroad proves that this support method is an effective support method for a roof with poor stability or an unstable roof.
This method is shown in the figure, which has a riser-type anchor on each side, and the lower end is connected by a high-strength steel rod. By means of the elastic nut, a pre-tightening force is applied to the anchor truss, so that the anchor is After the tie rod member is installed, the inverted truss is formed together with the roof rock formation. It has been proved by experiments that the anchor truss can be used to change the tensile stress of the top plate of the deposit to compressive stress, so that the top plate is in a stable state.
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