Abstract:Phenomenon of lining cracks is one of the familiar diseases during highway tunnel construction. Based on the monitoring data and actual geological situations of Sangongjing tunnel,causes of cracks and their development are generalized by means of direct and back analysis from the viewpoint of mechanics. The application range of tunnel design norm is discussed and compared with the method of site monitoring or back analysis;meanwhile,the reasonable design and construction projects are suggested. Then,the internal force condition of the second liner lying in a certain section is analyzed as an example,which is checked up as an intensity index,aiming to explain the cracks. Result of synthetically analyzing and mechanical computation turns out that the unsymmetrical load is the main cause of the cracks in tunnel lining. Finally,synthetically disposal measures proposed in this paper show the effect is satisfactory after it being enforced.