According to the Xiedipo double-arch tunnel engineering of the Yishui(Yibin—Shuifu) Highway

the key parts of structure force are monitored and analyzed by setting testing component in the tunnel; and during each period of construction the stress state of surrounding rock

bolt axial force

internal force of the middle-wall and internal forces of tunnel supporting structure are obtained under the condition of the constructional partial press. By analyzing tunnel mechanical characteristic under constructional partial press

the conclusions are drawn as follows: the most dangerous construction procedure of the tunnel structure force is from one side to the other side in the construction of the tunnel

that the bending moment direction of the middle-wall is always from one tunnel constructed lastly to the other tunnel constructed firstly in the double-arch tunnel. The monitored data and the experience can be for reference in the design

construction and research of similar tunnels.