Analytically Determining Bond Shear Strength of Fully Grouted Rock Bolt Based on Pullout Test Results

  • Mousa Hazrati Aghchai ORCID
    Affiliation

    Department of Mining Engineering, Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology 424 Hafez Ave, Tehran, Iran, P.O.B. 159163-4311

  • Parviz Maarefvand
    Affiliation

    Department of Mining Engineering, Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology 424 Hafez Ave, Tehran, Iran, P.O.B. 159163-4311

  • Hossien Salari Rad
    Affiliation

    Department of Mining Engineering, Faculty of Mining and Metallurgical Engineering, Amirkabir University of Technology 424 Hafez Ave, Tehran, Iran, P.O.B. 159163-4311

Abstract

Usually, in a fully grouted rock bolt pullout test the load-displacement curve of the rock bolt head is recorded. This paper presents an analytical method to use this curve for determining the bond (bolt-grout and grout-rock interface) shear strength parameters. For this purpose, the fully grouted rock bolt interaction with grout and surrounding rock in the pullout test is investigated and the load-displacement curve of the bolt head (beginning of the bonded section) is obtained analytically. For modeling the bolt-grout interface behavior a distribution of the shear stress along the fully grouted rock bolt by consideration of bolt shank failure is used. In this regard, different stages including complete bonding, partial decoupling, decoupling with the residual shear strength and complete decoupling are considered. With increasing the applied load, two possible cases involving the rock bolt complete pullout and bolt shank yielding are taken into account. Based on the presented analytical method, the obtained bolt head load-displacement curve can be compared with the one recorded in the pullout test. With this, the relevance of selected shear strength parameters compared to real parameters can be assessed. A flowchart for determining the bolt bond shear strength parameters is presented using the trial and error method (coded in Matlab). The proposed solution is used to determine two experimental pullout shear strength parameters. The results show good agreement between predicted and calculated load-displacement curves.

Keywords: load-displacement curve, fully grouted rock bolt, pullout test, bond shear strength
Published online
2020-02-03
How to Cite
Hazrati Aghchai, M., Maarefvand, P., Salari Rad, H. “Analytically Determining Bond Shear Strength of Fully Grouted Rock Bolt Based on Pullout Test Results”, Periodica Polytechnica Civil Engineering, 64(1), pp. 212-222, 2020. https://doi.org/10.3311/PPci.15195
Section
Research Article