(1) The secondary lining construction (including widened section) shall adopt the hydraulic automatic walking integral lining trolley. The lining trolley shall have accurate structure size, good operation of various telescopic components, hydraulic system and electrical control system, and reasonable setting of various supporting mechanisms; It shall meet the requirements of automatic walking and have locking device to ensure accurate positioning.

(2) The second lining trolley must be in the front field of the tunnel entry, and there must be two second lining trolley in the multi-arch tunnel and the small clear distance tunnel to ensure the reasonable step distance of the left and right line excavation and the second lining and ensure the safety of the structure. If the widened section is in the section of Ⅳ and Ⅴ surrounding rock, the gate shall be equipped with the whole lining trolley of the widened section to ensure the timely construction of the second lining of the widened section.

-----------------------------------------------------------------------------------------------------------------®(3) The overall formwork plate of the trolley is composed of panel, support frame, hinge joint, operation window, etc. When the lining section is large and the load is large, the support frame shall be made of truss structure, and the number of joints of the plate shall be reduced as much as possible. The formwork and support shall have sufficient strength, rigidity, stability and anti-floating ability, and can safely bear the gravity and lateral pressure of the poured concrete and various loads that may be generated during construction. The template is not concave-convex, the support is not offset, not twisted, to meet the requirements of repeated use without deformation.

(4) The clearance under the truss door supported by the trolley formwork shall meet the traffic requirements of large-scale equipment required for the construction in front of the tunnel lining; The height of the platform at each floor of the truss shall meet the requirements of concrete construction, which is beneficial for workers to carry out construction operations such as pipe installation and concrete tamping. There must be climbing ladders up and down.

On and off the trolley, install the ladder. On and off the trolley, install the ladder.

(5) In order to ensure the clearance of the lining, the outer diameter of the formwork shall be appropriately expanded in consideration of the deformation as the reserved settlement.

(6) The thickness of the plate plate of the two-lane two-lining trolley shall not be less than 10mm; The thickness of the plate plate of the two-lining trolley in the three-lane tunnel shall not be less than 12mm; The four-lane two-lining trolley must be calculated and customized after being studied and reviewed by relevant parties. In order to reduce the traces between the two lining formwork, the width of each steel plate of the outer arc formwork shall be 2m, but shall not be less than 1.5m, and the joint between the plates shall be lapped or welded and polished according to the tooth opening. In order to ensure that the second lining trolley has a certain rigidity and strength, the weight per linear meter of the two-lane trolley shall not be less than 6.8 tons, and the weight per linear meter of the three-lane trolley shall not be less than 8.5 tons.

(7) working windows shall be set up at 3m, 5.3m and vault. the spacing between working windows shall not be greater than 3m in the longitudinal direction and 2.5m in the transverse direction. the window size shall be 50cm × 50cm and shall be neatly drawn. The periphery of the operation window shall be strengthened to prevent deformation. The windows and doors shall be smooth, tight and free from slurry leakage.

(8) The length of the second lining trolley shall be reasonably selected according to the plane curve radius and longitudinal slope of the tunnel. The length is generally 10~12m, and the length of the trolley with curve radius less than 1200 m shall not be greater than 9m.

(9) The lining trolley shall be manufactured in the factory and assembled on site. The middle line, section and clearance size shall be checked during on-site assembly. Before lining, the surface of the formwork shall be thoroughly polished to remove rust spots and apply oil to prevent rust. The joint of the formwork plate shall be welded and polished to smooth the weld, so as to prevent the warping and deformation of the formwork from affecting the concrete surface quality during use and avoid the wrong joint between the plate.

(10) For the used secondary lining trolley. Strictly debug the operating conditions of various telescopic components, hydraulic systems and electrical control systems to ensure good operating conditions, otherwise they should be replaced. The external arc formwork must be replaced with a new one and repaired by the formwork manufacturer.