Abstract:  To investigate the stress distribution characteristics of the compression zone formed by endanchored prestressed anchor bolts in the surrounding rock of tunnels, the response of the surrounding rock under the action of a single prestressed bolt is analyzed using laboratory tests and numerical simulations. The ABAQUS software is used to explore the radial stress distribution patterns in the surrounding rock of a horseshoeshaped tunnel anchored by bolt groups with various prestresses, lengths, and bolt spacings. The results reveal the following: (1) The compression zone formed by endanchored prestressed bolts primarily concentrates in the unanchored section of the surrounding rock. By contrast, the anchored section experiences a tensile stress concentration due to the shearing effect of the anchors. (2) With increasing anchorage length, the compression zone noticeably decreases; when full anchorage is conducted, a compression zone is formed only within a very small range near the bearing plate, limiting the diffusion effect of prestress. (3) The thickness of the continuous compression zone formed by a group of prestressed anchors considerably increases as the bolt spacing decreases. However, it shows less variation with increasing anchor length. (4) A continuous compression zone is more likely to form by short anchors within their range, whereas it cannot be formed by long anchors within their range, thereby limiting the effectiveness of stress diffusion.

Key words: endanchored prestressed anchor bolt, distributed optical fiber, compression zone under bolt group, stress diffusion, stress field, ABAQUS software