基于掌子面结构量化的公路隧道围岩分级方法

A Method for Classifying Surrounding Rock of Highway Tunnel Based on Quantization of Tunnel Face Structure

公路隧道围岩级别的划分是指导隧道设计、施工及地下工程岩体稳定性评价和安全风险控制的重要依据,目前在设计和施工中对隧道围岩级别的判定方法具有较多的经验性因素,且在实际隧道工程中各级围岩的稳定性情况极为复杂,即使是同一级别的围岩,隧道稳定性也不尽相同。为了实现施工阶段围岩分级的可操作性与准确性,通过研究在公路隧道开挖时采集的隧道掌子面图像,利用MATLAB编程建立了照相测量围岩分级系统。根据岩体块度指标RBI的概念,向隧道轮廓线依次布设19条虚拟测线,以掌子面径向19个方位的RBI值综合评价了掌子面岩体结构的差异性。考虑结构面分布特征,结合掌子面节理玫瑰花图获取岩体结构综合量化指标Z-RBI,对掌子面进行了综合评价,得出了Z-RBI与岩体结构类型对应关系。综合考虑岩体坚硬程度、Z-RBI、地下水条件、初始地应力状态等主要分级指标,利用层次分析法,提出了隧道围岩BT分级方法及评价标准。实际工程应用表明:与传统的BQ法相比,BT分级方法获取的围岩等级更符合开挖后掌子面围岩的实际等级,且各等级可靠指标的延续性可对隧道施工过程中地质属性的变化情况进行定量表征,有助于工程地质人员据此对围岩质量的渐变过程进行动态评估。

The classification of surrounding rock grades of highway tunnels is an important basis for guiding tunnel design, construction and underground rock mass stability evaluation and safety risk control. At present, there are many empirical factors in the design and construction of tunnel surrounding rock grade determination methods, and the stability of the surrounding rock at all grades is extremely complicated in the actual tunnel engineering. Even for the surrounding rock of the same grade, the stability of the tunnel is not the same. In order to realize the operability and the accuracy of surrounding rock classification in the construction stage, by studying the images of tunnel face collected during excavation of highway tunnel, the surrounding rock photographic classification system is established by MATLAB programming. According to the concept of rock block index(RBI), 19 virtual measuring lines are arranged in turn to the tunnel contour line, and the difference of the rock mass structure of the excavation face is evaluated synthetically by the RBI values of 19 radial azimuths. Considering the distribution characteristics of structural planes and the rose diagram of joint of the excavation face, the comprehensive quantitative index of rock mass structure(Z-RBI) is obtained to comprehensive evaluate the excavation face, and the corresponding relationship between Z-RBI and rock structure type is obtained. Comprehensively considering the main classification indicators such as hardening degree of rock mass, Z-RBI, groundwater condition and initial geostress state, the BT classification method and the evaluation criterion of tunnel surrounding rock is put forward by using AHP. The engineering application shows that compared with the traditional BQ method,the surrounding rock grades obtained by the BT classification method is more in line with the actual surrounding rock grade of excavation face, and the continuity of the reliability indicators of each grade can quantitatively characterize the changes of geological properties during tunnel construction, which helps the engineering geologists to dynamically evaluate the gradual changing process of surrounding rock quality.