The currently used grouting anchors and resin anchors cannot simultaneously meet the demand for the anchor’s high pre-tightening force, high-strength support at the initial phase, ability to fill fissures of surrounding rocks, and strong corrosion resistance and durability in deep broken surrounding rocks of the roadway support. Meanwhile, after the application of the pre-tightening force, the grout body, which is already bound to the anchor body, is in a most disadvantaged stress state: the brittle materials of the grout body are under tension, causing the supportive effect of the grouting anchor to further decrease and even become invalid. Even if the pre- tightening force can be applied, it must wait until the grout body reaches a certain strength, which is a fatal defect for deep roadways that require timely and sufficient supporting strength at the initial phase of excavation. However, because the length of the free segment of the grouting anchor is usually quite short, the application of pre-tightening force is very limited, which fails to meet the demand of active support. Grouting anchor measures can effectively improve the integrity of the surrounding rocks in the roadway and effectively enhance the cohesion and internal friction angle of the surrounding rocks, thereby increasing the self- supporting ability of the surrounding rocks and significantly improving the roadway- supporting effect and quality. Practice has demonstrated that whether an anchor can provide sufficient pre-tightening force is key to realizing active support, effectively controlling the deformation of the surrounding rock in the roadway, and improving the anchor supporting quality in the deep roadway, especially in roadway support under broken rock mass conditions. At present, the pre-stressed anchor support is the major form applied in deep roadway anchor support.
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