The Application of Self Drilling Rock Bolt in Tunnel

With the increase in highway and railway engineering construction, tunnel support construction is inevitably carried out during the construction process. Since it integrates the three functions of drilling, grouting, and anchoring, self-drilling rock bolts have become the preferred supporting materials in tunnel excavation construction. Especially in the weak and broken surrounding rock geology, the self-drilling rock bolt can well solve the problem of difficult hole formation.

When the tunnel passes through the weak and broken surrounding rock, the excavation disturbance will cause large deformation of the surrounding rock. If the initial support is not done in time, the deformation of the surrounding rock may exceed its allowable range, and in severe cases, it will cause the instability of the face and the collapse of the tunnel, resulting in significant economic losses. At this time, it is necessary to adopt the tunnel advanced support measures to control the deformation of the surrounding rock, so as to achieve the purpose of ensuring the safety of the tunnel construction.

Self-drilling bolt is an irreplaceable product for tunnel advance support, and plays a major role in geotechnical support:

1. Consolidate the tunnel circumference and support the rock mass radially, forming a load-bearing ring, so that the rock mass can support itself (with shotcrete and other surface elements);

2. Umbrella shelters and advance braces are used as means of advance support in the case of inferior rock layers, shallow soil layers, and ultimate stress;

3. Reinforcing the end face to maintain the internal stress of the rock for tunnel excavation with a large cross-sectional area;

4. Locking piles for transferring pressure loads.

Advantages of Self-Drilling Rock Bolt

1. Self-drilling rock bolt system, which combines drilling, grouting, and anchoring together, is suitable for broken rock and conditions which are difficult to drill holes. Casing pipe is omitted in construction, which greatly improves construction efficiency.

2. Self-drilling rock bolt system has a rich variety of drill bits, and the drill bit can be selected according to the properties of rock and soil, which can improve the drilling efficiency.

3. Self-drilling rock bolt system can fill cracks, consolidate rock mass and soil layer through pressure grouting, and has good grouting spreading radius and reliable anchoring quality.

4. The hollow anchor bar can be cut arbitrarily and lengthened by the coupler. Therefore, the self-drilling anchor bolt is suitable for construction in a narrow space that large equipment cannot enter.

Most of the traditional tunnel support adopts the support method of following the pipe drilling, and the efficiency is extremely low. The construction of self-drilling rock bolts saves the steps of the casing pipe and is more efficient. Self-drilling rock bolts with special drilling rigs can be applied to various loose and broken formations. Simultaneous grouting during drilling can appropriately expand the hole diameter, thereby improving the pulling force and bearing capacity, and the effect of hole formation and force value is better than that of other reinforcement materials.