Principle Analysis Of the Collapse Reduction Effect Of left-Handed Anchors

Principle analysis of the collapse reduction effect of left-handed anchors

If the unstable rock layer of the vault is regarded as the combined beam (plate) supported by the side wall, because the anchor hanging on the stable surrounding rock can be regarded as the fulcrum, the installation of left-handed anchor without longitudinal ribs is equivalent to adding the fulcrum, reducing the support span, and then reducing the bending stress and deflection of the support to maintain the stability of the support and the rock, so that the rock is not easy to deform and damage. This is the bolt's "reduce span" function, actually is the bolt's hanging function. But also failed to provide methods and parameters for the planning of anchor support parameters.

After the installation of mining anchor, the surrounding rock of the tunnel will constitute a continuous shortening zone. The effect of anchor rods is to make a certain thickness of shortening band in the surrounding rock to accept the concept of surrounding rock pressure.

According to the theory of composite arch, when pre-stressing anchor rods are installed in the fissure area of the surrounding rock of the arch hole, the compressive stress distributed in the cone is formed at both ends of the rods. If the anchor group is arranged around the tunnel, as long as the distance between the anchors meets the small, each anchor constitutes a cone of compressive stress interspersed with each other, constituting an average shortening zone in the rock body.

That is, the pressure arch (also known as composite arch or pressure arch), this pressure arch can accept the radial load applied by the upper broken rock. In the constrained arch, the rock accepts radial and tangential pressure, and in the three-dimensional stress state, the strength of the surrounding rock is improved, and the support is added accordingly.

Composite arch theory to a certain extent reminds the effect mechanism of mine anchor support, but in the analysis process, did not deepen the consideration of the mutual effect of the surrounding rock and support, just simply add the large support force of each support structure, and then get the total support force of the composite support structure, the lack of further analysis and comments on the mechanic behavior of the reinforced rock itself, the calculation is also pervasive utility, can not be used as a quasi-go The quantitative planning, can be used as an important reference for anchor reinforcement planning and construction.