基于引水隧洞安全和经济施工的支护参数优化分析

以引大济湟项目为工程背景，结合引水隧洞施工工艺及现场条件，采用正交试验设计，建立以初衬厚度(因素A)、钢拱架间距(因素B)和开挖进尺(因素C)为影响因素的9个不同工况，运用MIDAS GTS进行数值模拟，采用极差法分析，得出各指标影响因素的主次排序，并将隧洞的安全性与经济性相结合，分析两者的线性关系，再引入灰色关联度理论，选择拱顶下沉、底板隆起等作为评价指标，对9个工况进行分析，评价出隧洞最优施工支护方案。结果表明：隧洞洞室初衬拱顶应力的影响因素主次顺序为钢拱架间距、初衬厚度、开挖进尺，即B、A、C；拱顶下沉、开挖成本占比及钢拱架成本占比的影响因素主次顺序为C、B、A；底板隆起、水平收敛以及初衬底板应力、边墙应力和拱脚应力的影响因素主次顺序为C、A、B。开挖成本占比和总成本与洞室位移、初衬应力（除开挖成本占比相对于拱顶应力之外）及综合得分均呈负相关；钢拱架成本占比与洞室位移、初衬应力(除拱顶应力之外)及综合得分均呈正相关。计算各工况灰色关联度得出综合安全性和经济性的最优方案为工况7，其关联度为0.763，具体参数为初衬厚度16 cm，钢拱架间距1.0 m，开挖进尺1.5 m。

Optimization of supporting structure parameters based on safe and economic construction of water diversion tunnels

Taking the Datong-to-Huangshui River Water Diversion Project as the research object, MIDAS GTS was adopted for the simulation of the diversion tunnel using orthogonal design, based on the construction technique and site conditions. Nine different working conditions with the primary support thickness (A), the interval between steel arches (B) and the excavation length per cycle (C) as the influencing factors were simulated to analyze the significance of each influencing factor using extreme range method. Then, in order to achieve the goal of safe construction with less investment, the linear relationship between safety and economy of the construction was analyzed by grey relational theory with the crown settlement, floor uplift and other parameters as the evaluation indicators. Finally, the nine working conditions were analyzed and an optimal construction plan for the tunnel was determined. The results show that the order of the primary and secondary influencing factors of the primary support arch stress was B, A, C, namely the interval between steel arches, primary support thickness and excavation length per cycle, that of the crown settlement, proportion of expenses of excavation and steel arches was C, B, A, and that of the floor uplift, horizontal convergence primary support floor stree, side wall stress and vault foot stress was C, A, B. The proportion of excavation expense and total cost are all negatively correlated with displacement, primary support stress except the proportion of excavation expense relative to vault stress and comprehensive score; whereas the proportion of steel arch expense is positively correlated with the above parameters except the vault stress of the primary support stress. According to the calculation of the grey relational degree of each working condition, it is concluded that the optimal scheme in terms of comprehensive safety and economy is working condition 7, and its relational degree is 0.763. The specific parameters of the primary support thickness is 16 cm, the interval between steel arches is 1.0 m, and the excavation length per cycle is 1.5 m.