Abstract:Combined with the facts that the strata of the entrance at Xiang¢an side of Xiamen Xiang¢an subsea tunnel are weak and unstable,the excavation is difficult,and the preliminary lining deforms severely. The reason of the left tunnel deformation excavated by CRD method under the condition of surrounding rock of class V is analyzed. Based on the measuring data,the construction stability of the large-section subsea tunnel in weak strata is analyzed,including the characters of surrounding rock,the distance between each step of CRD working face,the time of each step of CRD first shoring finished,the time of the whole working face completed,the distance between the permanent inverted arch and the working face,and grouting behind preliminary support or not. Based on these,the measures controlling the deformation are put forward. Successful practice and techniques are summarized to provide experiences for similar engineering.