Abstract: 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.

Key words: karst tunnel, lining structure, Pasternak elastic foundation beam, compression modulus, cavern scale, mechanical behaviors