Discussion on the technology of high-grade general mining face passing through fault

The two working faces of 35405 and 35404 are typical working faces with smooth surface faults, all of which are DY-150 type and single roller.

Analysis of the condition of the top plate of 1,35405 working face and 35404 working face

From the comprehensive histogram of the coal and rock layers of the two working faces, the top plates of the two working faces are very similar. The commonalities are:

(1) The coal seams are all four layers of coal;

(2) The basic top of the working face is grayish white sandstone , and the direct top is gray fine sandstone. The hardness is higher than f=4.

(3) There is a false top on the coal seam above the working face.

The so-called fault, fault refers to the fracture structure of the rock mass along the rupture surface with significant relative displacement. The displacement of the fault is large and small, only a few centimeters small, and can reach several kilometers. The rock layers and rock masses on both sides of the fault plane are called discs. If the fault plane is inclined, the part located on the upper side of the fault surface is called the upper disc, and the part located on the lower side of the fault plane is called the lower disc. Faults can be divided into normal faults, reverse faults, and translational faults.

Here we will focus on the mining technology of the working face in the case where the fault strikes a small angle of 150 with the coal wall of the working face. We are all introducing normal faults here. The drop is 1.2 to 1.5 m, and the thickness of the coal seam on both working faces is 2.2 to 2.5 m.

2. Variation characteristics of roof and coal seams in fault mining

From the summary of the changes of the roof and coal seams during the faults of the two working faces, the fault mining face has the following characteristics:

(1) The top plate of the working face is relatively broken, and the top plate is partially concave and convex.

(2) The coal seam is soft and has obvious squeezing phenomenon.

(3) The pressure on the top surface of the working face is obviously increased, and the pillar bottoming and the three-way valve unloading valve are opened.

(4) The amount of sinking of the roof is increased, and the coal wall of the working face is helped to slide down.

It can be seen from these four characteristics that in the fault mining, the mine pressure observation advance prediction and roof support are emphasized.

3. Analysis of over-fault technology

In view of the technical characteristics of fault mining, combined with our experience in mining 35405 and 35404 working faces, the following sections summarize the following fault mining:

3.1 Reasonable working face roof control design:

The roof control design goal can be summarized into four words: safe and economical. The normal pillar spacing of the 35405 working face and the 35404 working face is 0.6m, the row spacing is 1.0m, and the support density is 1.67 roots/m2.

Determination of the actual working resistance of the pillar:

RT=kg×kz×Rb=0.95×0.95×25×9.8=221(kN)

Where: Kg: pillar working coefficient, take 0.95;

Kz: coefficient of increase of resistance, taking 0.95; Rb: rated working resistance of the pillar;

Determination of reasonable support density:

N=Ps/Rt=332/221=1.50(花/m2)

According to the support strength selected by this surface and the actual working resistance of the pillar, the reasonable support density is calculated to be 1.50 trees/m2. It can be seen from the calculation that the actual basic support density of the working face is greater than the reasonable support density.

3.2 Improve the initial support of the pillar

3.2.1 Increasing the initial support of the strut can effectively prevent the top plate from being free

If the initial support force of the pillar is small, due to the fracture of the roof at the fault, the basic roof will slip under the weight of the self-weight and the overburden, resulting in a catastrophic roof-breaking accident, causing significant personnel and property losses. Improve the initial support of the strut so that the initial support of the strut not only can bear the weight of the basic top, but also can make the basic top close to the overburden, so that the friction between them is enough to prevent the lower stratum from falling.

3.2.2 Reasons for the low initial support of the pillar:

The initial support of the pillars is small, and there are two reasons: First, the construction is not carried out according to the requirements, the initial support force is not achieved, or the pillars are supported on the floating coal, so that the pillars fail to meet the design requirements. The other is due to the failure of the pillars and the design requirements are not met.

3.2.3 Methods and advantages of improving the initial support of the pillar:

(1) When the soft bottom left or bottom strut coal iron shoes wear, the wearing iron shoes, when the end of the pillar drill than 100mm, or bamboo fence sabot to the underlying iron shoes.

(2) The support of the pillars must not be supported on the floating coal.

(3) Strengthen the secondary injection of the pillars.

Solving the stability problem of the single bracket by increasing the initial supporting force of the pillar itself can not only prevent the push-over type roofing at the fault, but also increase the process, which is relatively easy to accept.

3.3 Working surface fault section using double-resistance net or bamboo raft top

There are three advantages to using a double-resistance net or a bamboo-backed top at the fault. Generally, the top plate is prevented from damaging people. Second, improve the integrity of the top board. Third, avoiding the phenomenon of burying the column when returning to the column.

3.4 Shortening the overhead time

When the unit cuts the top coal, closely observe the condition of the roof and timely fix the temporary column or sleeve to strengthen the support of П steel. In particular, when the fault plane is exposed, stop and stop, and temporarily install a temporary column behind the drum of the unit, and move the section of П steel forward.

3.5 fault support

When the unit is tilted along the working surface to expose a large area of ​​the fault, under the support of the first exposed disc, the post-exposure disc is supported in time, and the fault of the fault can be larger, and the section can be used to support the fault. The cannon was taken after two cycles. The disclosure of the fault section can be seen in five times and six times. Keep the sidewalk open. see Attachment

3.6 Controlling the height of the rock so that the rock formation can exceed the mining height.

When the 35405 working face is mined, the average mining height is 2.2 meters. Since the four-layer coal roof is relatively hard and the rock layer is free to fall, the goaf cannot be filled. The topping work should be strengthened to ensure that the falling meteorite can fill the goaf. Prevent large pieces of free meteorites from pushing across the work surface at the fault.

4 Conclusion

During the mining process of 35405 and 35404 working faces, a reliable over-fault mining technology was formed, which achieved safe production and achieved good economic benefits.