为探明端部锚固预应力锚杆在隧道围岩中所形成的压缩带应力分布特征，先结合室内试验和数值模拟手段分析单根预应力锚杆作用下的围岩响应；然后，采用ABAQUS软件研究不同预应力大小、长度及间距的锚杆群在马蹄形隧道围岩中形成的径向应力的分布规律，并对压缩带内径向应力分布规律进行进一步分析探讨。研究结果表明： 1）端锚型锚杆预应力所形成的压缩带主要集中在未锚固段围岩中，而锚固段围岩中由于锚杆剪力作用会形成拉应力集中区； 2）随着锚固长度的增加，压应力区明显减小，全长锚固时，仅在垫板端附近极小范围内形成压应力区，无法较好地发挥预应力的扩散效果； 3）群锚预应力形成的连续压缩带厚度随间距减小明显增大，但随长度增大变化不明显； 4）短锚杆更易在杆长范围围岩内形成连续压缩带，而长锚杆无法在整个杆长范围围岩内形成压缩带，其应力扩散效果有限。
To investigate
the stress distribution characteristics of the compression zone formed by endanchored
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
horseshoeshaped tunnel anchored by bolt groups with
various prestresses, lengths, and bolt spacings. The results reveal the
following: (1) The compression zone formed by endanchored
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.
