# An Investigation into Bol Anchoring Performance during Tunnel Construction in Bedded Rock Mass
## 3 Experimental Results
### Uniaxial Compression Testing
The reason for this is that under the action of full-length bonding and bolt \"pin action\", the strength of the specimen near the two ends of the bolt is increased, and the interior is relatively soft, so there is a \"soft-hard interface\" in the specimen. Shear failure occurs along the \"soft-hard interface\" under load, as shown in Figure 6b. Figure 4: Rock strength parameters by different anchoring methods: (**a**) Uniaxial compressive strength; (**b**) Elasticity modulus. On the basis of this, the reinforcement mechanism of the bolt can be summarized as follows. Figure 5: Failure forms: (**a**) No anchoring; (**b**) End anchoring; (**c**) Full-length anchoring. Figure 6: Failure planes of anchored specimens: (**a**) End anchoring; (**b**) Full-length anchoring. (1) The anchoring agent has a bonding effect and damage repairing effect on rock mass around boreholes. Joints, fissures, and other structural planes often exist in the rock forming process, which reduce the mechanical properties of rock, large-scale structural planes, and even the controlling factors of surrounding rock failure. The anchoring agent enters the structural plane under grouting pressure and plays a role in bonding and strengthening the surrounding rock near the structural plane, thus forming a \"reinforcement area\" within a certain range. The size of the \"reinforcement area\" is related to the grouting pressure, the material properties of the anchoring agent, the pore distribution of the surrounding rock, and so on. (2) The axial tensile and tangential shear capacity of the bolts can improve the stress state of the specimen. Under load, the specimen is affected by both the shear action along the bedding plane and the tension action along the axis (Figure 5a). When the specimen is deformed, the tension and shear action are applied to the bolt, and the bolt body provides support resistance, which limits the deformation of the specimen. Based on the above findings, we inferred that the anchoring increases the specimen strength and changes the failure plane direction by improving the tensile capacity and tangential shear-bearing capacity. Under axial compression, the specimen simultaneously bears the shear effect along the bedding and the tensile effect along the axial direction (as shown by Figure 5a), while the bolt body provides support resistance to restrain the specimen deformation. Based on the analysis of the bolt reinforcing performance, we determined that a difference existed between the reinforcing effect of the bolt for full-length anchoring and that for end anchoring. The gap between the bolt body for full-length anchoring and the surrounding rock was filled by the anchoring agent, which could bond and reinforce the surrounding rock with greater scope. In the case of the rock developing shear deformation, the bolt with full-length anchoring could immediately restrain further deformation. Meanwhile, a gap existed between the end anchoring bolt and surrounding rock. The bolt's tangential anchoring force only played a role when the surrounding rock developed a certain tangential deformation. Therefore, the bolt for full-length anchoring could form an \"anchoring area\" of greater range and provide greater support resistance than the end anchoring bolt.