Sinorock self-drilling hollow grouting bolt in tunnel surrounding rock support

13/mar/2017 07:11:10 hollowbar Contatta l'autore

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Application of self-drilling hollow grouting bolt in tunnel surrounding rock support

Summary

Since the type of hollow grouting bolt is a set of drilling, grouting, anchoring function in one of the new bolt, it can ensure high efficiency, safety and reliability in the complex formation. The application of this drilling method in tunnel surrounding rock support is described in detail in this article.

Introduction

Bolt anchoring support can give full play to the stability of the surrounding rock. It is widely used in road tunnel surrounding rock support.Permanent anchor bolts use ordinary mortar anchor mostly. But the grouting of ordinary mortar anchor is not sufficient, which leads to the actual effective anchorage zone cannot meet the design requirements.

In addition, it is hard to drill holes with the ordinary mortar injection bolt in the broken, loose rock condition. It results in failure of the bolt anchorage support.

Self-drilling hollow grouting anchor is a new set of drilling, grouting and anchoring functions into one. It can ensure the construction efficiently under the complex formation and reliable anchoring effect.

Comparative analysis of self-drilling hollow grouting anchor bolt and ordinary mortar injection anchor, ordinary hollow grouting bolt

In the same construction condition, respectively install Ф25 ordinary mortar anchor, hollow grouting anchor and self-drilling anchor (hereinafter referred as IBO hollow bar anchor) in the length of 2m and 5m. Mortar strength grade M30, anchorage by 150mm*150mm*60mm plates. The test results were analyzed as follows.

Pull out strength

As Table 1 shows, in the general crushing zone, 3 kinds of 2m anchor bolt tensile limit values are between 65-70 kN. The different from each other is not very big.

The pullout strength limit of 5m ordinary mortar anchor bolt is between 60-90 kN. The strength limit of two hollow IBO anchor types is between 140-150 kN. The increased pull resistance of Self-drilling anchor rods is not obvious.

In severe crushing zone, the pullout strength limit of 2m ordinary mortar anchor bolt is between 45-70 kN. For hollow grouting anchor and self-drilling anchor, the limit is between 60-75 kN. Decrease is not obvious.

For mortar grouting anchor bolt in the length of 5m, the strength limit is between 55-70 kN. And IBO bolt can achieve 130 to 145 kN. The pull strength advantage is very obvious.

In general, as the integrity of the rock mass decreases, the pull-out limit of the bolt decreases, and the ordinary mortar anchor decreases with the increase of the rock mass, and the hollow grouting anchor is more serious The loss of drawing limit in the broken rock mass is small.

Table 1: Comparison of anchor bolt pull strength

(Unit: kN)

Anchor Bolt Type 2m 5m
General broken area Severe broken area General broken area Severe broken area
Ordinary mortar anchor 65-75 45-70 60-90 55-70
Ordinary hollow bar anchor 65-75 65-75 140-150 130-145
IBO self-drilling anchor 65-75 65-75 140-150 130-145
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