Mechanical Properties of Full-Grouted Prestressed Anchor Bolts under Typical Bed-Separation Conditions

Abstract

For tunnel-support engineering, the bed separation of surrounding rock has a great influence on the support performance of bolts. In order to reveal the mechanical properties of the full-grouted prestressed bolt under the influence of bed separation, three typical working conditions of single-separation, multi-separation and different separation positions were set up, and theoretical models and numerical models were established. Furthermore, the characteristics of bolt axial force and anchorage–interface shear stress were analyzed by numerical method, and the sensitivity based on an orthogonal test was studied by means of range analysis and variance analysis. The results showed that: (1) under the single-separation condition, the separation value has a significant effect on the mechanical properties of the bolt, and with the increase in the separation value, the sliding failure unit of the bolt increases; (2) for multi-separation conditions, if the total separation value is the same, the increase in the number of separation interfaces is beneficial to the force of the bolt; (3) for the case where the separation layer is located at different positions, the separation layer on the right side is more likely to cause the overall slip failure of the bolt; and (4) for the above three influencing factors, the separation value has the greatest influence on the mechanical properties of the bolt, and the separation position has the least influence.

Comparative Analysis of Mechanical Properties of Three Typical Bolts under the Influence of Bed Separation

“…In Figure 3, L is the total length of the bolt, L a is the length of the secondary bonding section, L b is the length of the initial bonding section, F is the preload force, and b is the value of the bed separation. The full-length anchored pre-stressed bolt under the action of the bed separation was regarded as the superposition of the end-anchored pre-stressed bolt and the fulllength anchored bolt under the action of the bed separation [21,22], and the axial force and interfacial shear stress expressions were derived by the superposition principle.…”