1. Roadway metal stents operating characteristics

From the general law, the weight of the overlying rock mass on the roadway is only 1% to 2% of the weight of the roadway support, and the rest is completely absorbed by the rock mass around the roadway. The research shows that the working characteristics of the roadway support are fundamentally different from the general ground engineering structure. The size of the support is not only dependent on its own mechanical properties (bearing capacity, stiffness and structural characteristics), but also its supporting object-surrounding rock itself. The mechanical properties and structure are closely related, that is, the "scaffold-surrounding rock" interaction relationship.

2. The basic state of the "bracket-surrounding rock" interaction

â‘  When the roadway stone and slate roof delamination or peeling overburden, limited only by delamination or peeling stent weight rock pressure, the stent at a given load condition.

2 When the roof rock and the overlying rock layer are not separated or fallen off, the load and compression deformation of the support will depend on the movement state of the overburden. In this case, the support of the bracket itself cannot prevent the movement of the overburden. Only when the overburden is covered by the meteorite or the filler, the shrinkage deformation of the bracket can be stopped. When the bracket is in a given deformation state.

3. "Brace-surround rock" interaction principle

The existing roadway brackets can only bear a very limited part of the load in the "bracket-surrounding rock" mechanical balance system. The role of the bracket in the internal stress balance relationship of the surrounding rock is small, but not Attempts to rely on the bracket to change the motion state of the overburden. However, this tiny supporting force of the bracket is extremely important and indispensable. The working resistance of the bracket, especially the initial supporting force, can restrain the direct roof separation layer to a certain extent and control the redevelopment of the plastic zone of the surrounding rock. And the continuous deformation of the surrounding rock to maintain the stability of the surrounding rock. Therefore, the roadway support system must have appropriate strength and certain shrinkage to effectively control and adapt to the deformation of the surrounding rock.

a b

Figure 7-17 Mechanical model of the "support-surrounding rock" interaction Figure 7-18 Interaction between the support and the surrounding rock

A—given load state b—given deformation state A—elastoplastic phase B—loose fracture phase

4. Application of the principle of "bracket-surrounding rock" interaction

(1) Implement secondary support

When the surrounding rock of the roadway reaches a stable state, the deformation amount is large, and when the continuation time is long, it is necessary to carry out a support after opening the roadway. The surrounding rock is closed and isolated in time to prevent some dangerous stones from falling on the exposed surface of the surrounding rock, and at the same time, the initial movement of the surrounding rock is limited to a certain extent. One support allows a certain deformation of the surrounding rock, and after the deformation of the surrounding rock and the release of energy to a certain extent, secondary support is carried out. The secondary support shall be carried out at an appropriate time when the initial support has not failed and the speed of the surrounding rock has been small.

(2) Using flexible support

The metal shrinkable bracket not only has a certain resistance to the deformation of the surrounding rock, but also has a shrinkage property to avoid serious deformation and damage of the bracket. While allowing the finite deformation of the surrounding rock to continue to release energy, the bracket still has sufficient working resistance, which can adapt to the deformation of the surrounding rock and control the deformation of the surrounding rock, and fully exert the supporting effect of the bracket.

(3) Emphasis on active support

The metal bracket with a certain initial working resistance is used to increase the confining pressure of the surrounding rock of the roadway, improve the strength of the surrounding rock of the roadway, and reduce the load on the bracket. Filling the concrete behind the roadway bracket and spraying the concrete to improve the stress state of the support and the surrounding environment of the surrounding rock, and improve the bearing capacity of the support and surrounding rock.

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