Study and engineering application on the bolt-grouting reinforcement effect in underground engineering with fractured surrounding rock

• Published in: Tunnelling and underground space technology 2019-02, Vol.84, p.237-247
• Main Authors: Wang, Q., Qin, Q., Jiang, B., Yu, H.C., Pan, R., Li, S.C.
• Format: Article
• Language: English
• Subjects: Bolt-grouting parameters; Bolt-grouting reinforcement; Bolts; Design engineering; Diffusion performance; Diffusion rate; Engineering; Field test; Fractured surrounding rock; Grout; Grouting; Influence law; Interfacial shear strength; Interfacial strength; Internal friction; Lithology; Mathematical analysis; Mechanical properties; Modulus of elasticity; Parameters; Rocks; Support systems; Tunnels
• ISSN: 0886-7798; 1878-4364
• DOI: 10.1016/j.tust.2018.11.028

•The influence law of anchorage body interface strength were obtained.•The systematic field bolt-grouting test was performed.•The variation trend of the grout diffusion performance was analyzed.•The effects law of various bolt-grouting parameters on the surrounding rock were obtained. Bolt-grouting support is an effective means for addressing the difficulty of fractured surrounding rock control in underground engineering. In this paper, to determine the improvement in the anchorage body interface strength resulting from grouting, theoretical equations for calculating the anchorage body interface shear strength before and after grouting were derived, and the influence law of various mechanical parameters (elastic modulus, cohesion, internal friction angle, and dilation angle) of the surrounding rock on the anchorage body interface strength were obtained. Based on the aforementioned theoretical analysis, a systematic field bolt-grouting test was performed on surrounding rock with the same lithology and different fragmentation degrees. The variation trend of the grout diffusion performance under the different grouting bolt length was analyzed. Furthermore, the effects law of various bolt-grouting parameters on the surrounding rock and support system were also revealed. The following results were obtained: (1) The pullout forces of the common bolts increased significantly after grouting. In addition, the grout diffusion basically stabilized 7 days after grouting. (2) The increasing rate of pullout force on the common bolt around the grouting bolt presented the rule of “Below > Side > Above”. (3) With the length of grouting bolt increasing, its effective reinforcement range gradually expanded. (4) The variation in the grouting bolt length had a relatively insignificant impact on pullout forces of the common bolts in its immediate vicinity. Based on the above theory and experimental study, relevant engineering proposal were recommended and adopted in the design of site bolt-grouting support schemes. The research results can provide methods and basis for selecting and evaluating of grouting bolt parameters in underground engineering with fractured surrounding rock.