黄土隧道围岩的结构性变化特征分析

Variation characteristic analysis of a structural parameter for surrounding soils in loess tunnels

在分析和修正已有结构性参数的基础上,首次提出了将结构性参数直接应用于工程实践的思路。研究了黄土隧道开挖后围岩结构性的变化规律。研究得出:围岩的结构性参数与径深和洞径密切相关;随着径深的增大,拱顶方向上围岩的结构性参数均呈现出先减小后增大的规律,存在一个最小值。与开挖前原状土的结构性参数相比,围岩的结构性损失在距拱顶约1.7～2.5 m时达到最大。随着洞径的增大,开挖对围岩黄土的扰动增强,拱顶方向上围岩的结构性减弱,结构性参数的最小值变化不大,但最小值发生的位置逐渐远离拱顶。最后,提出了以围岩结构性损失最大为依据判断围岩松动圈的新方法。分析表明,黄土隧道围岩的松动圈在1.7～2.5 m变化。

The structural parameter was applied to engineering firstly based on its analysis and modifiability. The variation of structural characteristics for excavated tunnels was studied. It was shown that the structural parameter was strongly affected by the diameter and depth of tunnels. The structural parameter in vault direction decreased firstly and then increased along with the tunnel depth. There was a minimum value of this paraneter. Compared with the structural parameter before excavating, its loss came to the maximum at the vault top of 1.7-2.5 m. The disturbance of structural characteristics for tunnels with larger diameter was more serious than that for small one. Although the minimum value of structural parameter did not obviously change, and its position moved gradually apart from the vault. Finally a new method to estimate broken zone according to the structural parameter was proposed. It was found that the thickness of broken zone of loess tunnels was about 1.7-2.5 m.