Filling mining method, ground pressure control (2)

The vertical splitting (wall) filling mining method is taken as an example to illustrate the interaction between the filling body and the surrounding rock. Elastic foundation beam theory, research in this mining method slate top layer stress distribution and mechanical properties of filling materials relationship, determines the role of the filling body.

When using the elastic foundation beam theory to analyze the pressure acting on the roof rock, the following assumptions were made.

(1) As the mining work advances forward, the filled area is immediately filled with filling material.

(2) There are no pillars left in the mining area.

(3) The ore and the filling body are all elastomers.

(4) The load acting on the roof rock layer is evenly distributed, and the base value is q _o = γH.

Based on the above assumptions, the roof rock formation can be considered to be a beam that is placed on an elastic foundation. The working space between the backfill and the mining face is negligible. The computational mechanics model is shown in Figure 3.

Fig. 3 Computational mechanical model of stress distribution in roof rock stratum

1- ore body; 2-filler

On the x>0 side, ie the side of the ore body, the roof stress P _y ^o is:

In the formula:

K-ore resistance coefficient, Pa;

C-filler resistance coefficient, Pa;

El-modulus elastic modulus, Pa;

J-beam to neutral axis moment of inertia, m ⁴ .

It can be seen from the above formula that the stress in the roof rock layer is wavy, at x=0; P _y ^o has the maximum value, namely:

When x=∞, P _y ^o =q _o =γH

On the side of x<0, on the side of the filling body, the top plate stress P _y ^F is:

The symbol in the formula is the same as before.

As seen from the above equation, when x = 0, P _y ^F is the smallest, and its value is 0; when x = ,, P _y ^F = q _o = γH.

Comparing the above two formulas, at x=0, the stress P _y ^o acting on the working surface is not equal to the stress P _y ^F above the filling body, and P _y ^{o is the} largest, and P _y ^{F is the} smallest, that is, the stress jumps here. Change (Figure 4).

Figure 4 Stress changes in the roof rock formation

In addition, if the filling work is not timely, that is, C=0, the stress P _y ^o acting on the roof rock layer above the working surface will tend to infinity. At this point, the work surface must be destroyed and mining work cannot be carried out.

According to the application of numerical simulation calculation and analysis of the vertical stress in the filling body under different conditions, it is concluded that the vertical stress can reach the original rock stress value of 35% to 100% in the cemented filling of the gently inclined thin ore body. In the thick ore body, the vertical stress in the filling body is only 25% of the vertical stress value of the original rock. The results of stress measurements on the filling body from Singer's mine in Canada also show that the stress at the thinnest part of the ore body is high, and the pressure of the central part of the ore body is 0.6-0.65 MPa, while the edge is the thinnest. The location is 1.5MPa.

XIKUANGSHAN application antimony ore tailings backfill room cemented filling pillar, the lower portion smoothly recovery ore bed, with the tailings backfill gob effectively control the pressure generating again a large area, using Western Gold Mine filling escarpment The law returns to the gently inclined very thin ore body, which limits the movement and collapse of the surface due to the action of the filling body, and protects the surface buildings and rivers. These examples illustrate the mechanical effects of filling on improving rock mass stability.