武汉地区溶洞存在埋深较浅、溶洞高度较小、地下水“高水头”等特征。基于这些特征,利用MIDAS GTS进行数值正交试验,分析了武汉地铁27号线围岩水平、侧压力系数、溶腔跨度、溶腔高跨比、渗透系数等对隧道与溶洞安全距离的影响规律和显著性。研究结果表明:隐伏溶洞位于隧道下方、侧方或上方工况条件下,围岩水平、溶腔跨度均会对隧道与溶洞的安全距离有显著影响,而渗透系数对其并无显著影响;侧压力系数只在隐伏溶洞位于隧道下方时有显著影响;溶腔高跨比只在隐伏溶洞位于隧道侧方时有显著影响。结合试验结果的非线性多元回归分析,分别建立溶洞在隧道下方、侧方、上方时的隧道与溶洞安全距离预测模型;通过工程实例的检验与应用,该分析方法可靠合理,可为类似工程提供借鉴和参考。

Karst caves in Wuhan are featured with shallow buried depth, small height, and high-head groundwater. Through numerical orthogonal test by MIDAS GTS, the significance of five major factors affecting the safe distance between the tunnel of Wuhan metro line 27 and the hidden karst caves is examined. The five major factors involve surrounding rock level, lateral pressure coefficient, span of cave, ratio of height to span of cave, and permeability coefficient. Results suggest that surrounding rock level and span of cave have significant impact on the safe distance between tunnel and cave whether the peripheral cave is located below, lateral to or above the tunnel, while permeability coefficient has no significant effect. Lateral pressure coefficient has a significant effect only when the peripheral cave is located beneath the tunnel. The ratio of height to span of cave has a significant influence only when the peripheral cave is located lateral to the tunnel. In association with nonlinear multiple regression analysis on the results, formulas for estimating the safe distance between tunnel and cave when caves are located below, lateral to and above tunnel are obtained. Case study proves that the proposed formulas are reliable.