基于多因素评价的隧道围岩质量与超欠挖关系

围岩质量及施工方法是影响隧道超欠挖的本质原因，研究围岩质量与超欠挖的关系，对评价和预测超欠挖、判断隧道结构的稳定性具有重要意义。基于工程实测资料及数值试验，研究了跨度对隧道围岩质量的影响，进而建立了基于多因素评价的围岩质量修正指标。根据隧道开挖断面轮廓具有分形特征的特点，计算了鸳鸯会隧道20个典型断面轮廓分形维数，研究了围岩质量与超欠挖的关系，得出围岩质量多因素修正指标与超挖比及断面轮廓分形维数呈线性关系，随着围岩质量多因素修正指标的提高，超挖比和断面轮廓分形维数将降低，并根据复相关原理，建立了三者间的复相关关系，可为隧道围岩质量的正确评价及超欠挖分析提供有益参考。对比不同围岩分级方法与超欠挖的关系表明，基于多因素评价的BQ法在隧道工程中的适用性更好。

Relationship between surrounding rock quality based on multifactor evaluation and overbreak-underbreak of tunnels

The surrounding rock quality and construction method are essential reasons affecting overbreak-underbreak of tunnels. It is important to evaluate and forecast overbreak-underbreak, and judge the stability of tunnel structure for researching the relation between surrounding rock quality and overbreak-underbreak. Based on the measured data and numerical experiment, the effect of span on surrounding rock quality is studied; and modified rock quality index based on multifactor evaluation is established. According to excavation section profile showing the fractal characteristics, the fractal dimensions of 20 sections profile of Yuanyanghui tunnel are calculated; and the relation between surrounding rock quality and overbreak-underbreak is studied. The linear relations among modified rock quality index and percent of overbreak and fractal dimension are gained. With the increase of modified rock quality index, the percent of overbreak and fractal dimension are decreased. According to the principle of multiple correlation, the multiple correlation among modified rock quality index and percent of overbreak and fractal dimension of section profile are established so as to provide reference for correct evaluation of surrounding rock quality and analysis of overbreak-underbreak. Meanwhile, by contrast with relation between different surrounding rock classifications and overbreak-underbreak, it is shown that BQ method based on multifactor evaluation has better adaptability in tunneling engineering.