为分析小净距交叉隧道台阶法施工过程中新建隧道和既有隧道的衬砌安全性，基于断裂力学的Griffith准则，提出了判定衬砌开裂的开裂安全系数CF，并假定CF>1时衬砌开裂，CF<1时衬砌安全；依托实际工程，结合开裂安全系数和规范中的衬砌截面安全系数，采用有限元软件ANSYS分析交叉隧道的衬砌安全性。分析发现： 施工过程中，交叉断面新建隧道衬砌环向安全系数小于纵向安全系数，但基本满足规范要求；既有隧道二次衬砌开裂安全系数CF远小于1，其开裂安全系数CF云图关于新建隧道轴线对称。分析结果对新建隧道的施工和既有隧道衬砌的防护具有重要意义。

Crack factor (CF) is proposed on basis of Griffith criterion to analyze the safety of the lining of the smallspaced intersecting tunnel constructed by benchcut method, as well as the safety of the lining of the existing tunnel. It is supposed that crack will occur to the lining when CF is more than 1 and that the lining is safe when CF is less than 1. The safety of the tunnel lining is analyzed, on basis of the crack factor and the safety coefficient of the lining provided in relevant standards, by means of ANSYS. Conclusions drawn are as follows: during the process of the construction of the new tunnel, the circumferential safety factor of the lining of the underconstruction tunnel at the intersection point is less than the longitudinal safety factor, but they both meet the requirements of relevant standards; the crack factor of the lining of the existing tunnel is far less than 1, and the cloud picture of the crack factor is symmetrical along the axis of the underconstruction tunnel. 