隧底溶洞对衬砌结构力学行为的影响

基于考虑地基剪切变形的Pasternak弹性地基梁理论,推导了无仰拱隧道拱脚处地基梁的位移和内力计算公式,对比分析了Pasternak模型和Winkler模型计算结果,与现场监测结果对比,并基于Pasternak模型研究不同介质压缩模量及不同溶洞规模情况下衬砌的变形受力状态.研究结果表明:Pasternak模型的计算结果比Winkler模型偏小,更符合实际变形受力情况;在溶洞和围岩的交界处衬砌存在明显的反弯点,且交界处剪力最大;溶洞填充物压缩模量与围岩压缩模量比值小于等于0.5时,溶洞段衬砌位移和内力急剧增加;溶洞规模对衬砌位移和剪力影响显著,长度8 m以上溶洞对衬砌结构危害性较大.

Influence of Karst Cavern on Mechanical Behavior of Tunnel Lining Structure

Based on the Pasternak elastic foundation beam theory considering the shear deformation， the displacement and the internal force calculation formulas of the beam for non-inverted tunnel arch foot were derived. Calculation results of Pasternak model and Winkler model and field monitoring results were contrasted. Based on the Pasternak model， the deformation and stress states of lining under different compression modulus ratio of cavern media and different cavern scales were comparatively analyzed. The results show that Pasternak′s solution is smaller than that of Winkler model and agrees with the field monitoring results. The inflection point of lining is located at the junction between cavern and the surrounding rockmass， where the maximum shear force can be observed. When the ratio of compression modulus of the infillings to the surrounding rockmass is less than or equal to 0.5， the displacement and internal force of the lining increase rapidly. The cavern scale has an obvious influence on the displacement and shear stress and the lining in the karst cavern with a length of over 8 m is easily destroyed.