VIP exclusive Practical construction organization design of tunnel works (drawings attached by China Railway)
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6、 Main construction methods and main construction processes 1. Construction methods: 1.1 Before the open cut excavation of the portal section, portal and open cut construction tunnel, intercepting ditches shall be set 5m away from the slope brushing line of the front slope. The ditches shall be connected with the side ditches of the cutting to intercept the surface water and prevent the surface water from scouring the front slope and portal of the portal and causing harm; Remove or reinforce the dangerous rock mass above the front slope of the portal so as not to endanger the safety of construction and operation...... 1.1.1 The construction process is to excavate from the entrance (DK248+878, original ground elevation 403.41) at a gradient of 10% according to the design stable slope ratio of 1:1 to the light and dark boundary, and then carry out the support of the portal and front slope and the construction of the hidden tunnel, as well as the excavation and support of the lower part of the open tunnel Foundation treatment and tunnel lining. The excavation front face (tunnel face) at the light and dark boundary shall be temporarily supported by shotcrete with a thickness of 8cm; Arch steel frame shall be erected and arch support shall be provided. During the construction of large pipe shed support, the concrete guide wall shall be constructed in combination with the closure of the tunnel face, and the construction of large pipe shed shall be completed. After the completion of advanced support, under the protection of advanced support, and according to the excavation of concealed tunnel, the construction shall be carried out according to the CRD method of concealed tunnel...... 1.1.2 During the excavation of open tunnel construction, the lining construction of open tunnel shall be started, and during the construction of oblique cut tunnel portal, The lining trolley shall be used to construct the first ring lining concrete of the open cut tunnel in the portal section, and then the inclined cut portal lining concrete. Mantanghong scaffold is used, and a 5.0m wide and 4.5m high passage is reserved in the middle of the scaffold for construction vehicles in the tunnel. Self made lining bench with special steel formwork shall be used for formwork lining. The bench adopts I18 I-beam, and the butt support adopts φ 150mm steel pipe, the formwork is made of special steel formwork, the spacing between steel frames is 1.0m, the installation is vertical, the connection between steel formwork and steel frame is U-shaped clamp, the connection between formworks is pin and clamp, and mortar stop adhesive strip is set between formwork joints. Other technical parameters are the same as the main tunnel lining requirements. During construction, the inverted arch shall be constructed first, and then the arch wall shall be constructed. The formwork is constructed in full section with self-made multi-functional bench. The internal formwork shall be installed first and fixed stably. Concrete pouring can be carried out after it is checked to be correct. During concrete pouring, the external formwork shall be installed and fixed firmly with the increase of concrete pouring height. Concrete pouring shall be transported by concrete truck, pumped into the formwork, and vibrated by immersion vibrator. During concrete pouring, special personnel must be assigned to monitor the deformation of formwork. When removing the formwork, first remove the baffle formwork, then remove the external formwork, and finally remove the internal formwork...... Set deformation joints at the junction of the open and closed tunnels, and lay the middle buried drainage rubber waterstop at the joints for waterproofing. During construction, use special clamps to fix the waterstop to ensure that the position of the waterstop is correct...... When the concrete of the open tunnel arch ring reaches 50% of the design strength, The back of the arch ring shall be leveled with mortar. Set waterproof layer, and immediately lay coiled material waterproof layer from bottom to top after applying a layer of hot asphalt on the arch back; When laying, it shall be closely pasted, overlapped and staggered, and the overlapping length shall not be less than 100mm, and shall extend to the arch back in the tunnel for not less than 50cm. Non woven geotextile shall be laid vertically on the arch back as the filter layer, and the waterproof board and geotextile shall be overlapped and hung as a whole. The arch back shall be paved with clay water resisting layer, compacted layer by layer, well lapped with the slope and inverted slope, and tightly sealed...... When the arch ring concrete reaches the design strength and the arch wall back waterproof facilities are completed, the arch back can be backfilled. The mortar rubble backfilling shall be constructed in layers by symmetrical mortar squeezing method. The earth rock backfill shall be compacted symmetrically and layer by layer, with the thickness of each layer not more than 0.3m, and the height difference of the earth surface backfilled on both sides not more than 0.5m; After backfilling to the arch crown, it shall be fully paved and filled layer by layer, and the top backfill material shall be clay to facilitate water separation...... 1.2 Excavation and support of large section loess tunnel body 1.2.1 CD method excavation and support of Class IV surrounding rock of xxx tunnel with a total length of 370m. CD method excavation shall be adopted, and advance small conduits shall be pre constructed according to the design requirements, with combined support of anchor, mesh and shotcrete, and side walls shall be set Φ 22 mortar anchor rod, set at arch Φ 22 Cartridge anchor bolt, full section mesh shotcreting micro fiber concrete support, supplemented by arch Ф 42 Advance small conduit and full ring steel frame shall be strengthened for support. Each advance small conduit is 5.0m, the circumferential spacing is 0.4m, and the lap length is more than 1.5m; The longitudinal spacing of steel frame is 0.8m. Each steel frame shall be used separately in the upper section tooth groove and wall foot Ф 42. The foot lock anchor pipe is reinforced and welded firmly with the steel frame. The foot lock anchor pipe is 3.7m long Ф 42 steel flower tube and cement mortar. The specific settings of advance support and enhanced support can be adjusted according to the actual geological conditions of the construction...... 1.2.2 CRD method excavation and support The total length of the Class V surrounding rock of xxx tunnel is 266m, and the Class V surrounding rock, the shallow buried section of the tunnel and the tunnel through section are excavated by CRD method. Advance large pipe sheds or advance small conduits are pre constructed according to the design requirements, and the combined support of anchor, mesh and shotcrete is provided, and the side wall is set Φ 22 mortar anchor rod, set at arch Φ 22 Cartridge anchor bolt, full section mesh shotcreting micro fiber concrete support, supplemented by arch Ф 50 advance small conduit and full ring steel frame shall be strengthened for support. Each advance small conduit is 5.0m, the circumferential spacing is 0.4m, and the lap length is more than 1.8m; The longitudinal spacing of steel frame is 0.6~0.8m. Each steel frame shall be used separately in the upper section tooth groove and wall foot Ф 42. The foot lock anchor pipe is reinforced and firmly welded with the steel frame. The foot lock anchor pipe is 3.54m long, and the Ф 42 steel flower tube and cement mortar. The specific setting of advance support and strengthened support can be adjusted according to the actual geological conditions of the construction...... 1.4. Complete and smooth drainage system is set for the waterproof and drainage construction portal works to drain the surface water away from the portal as soon as possible and prevent the surface water from forming new holes near the portal. The ditch at the outer side of the portal end shall be made into a reverse slope drainage of not less than 2 ‰. An intercepting ditch is set 10 m away from the slope line at the tunnel top to intercept the surface water, so that the surface water will flow into the subgrade drainage system to avoid new scouring. The full slope protection of the side and front slopes of the tunnel portal to prevent rain erosion of the slope surface or loess collapse caused by infiltration...... EVA waterproof boards are laid on the arch walls of general sections of the tunnel, waterproof concrete is used for the secondary lining of the tunnel, and its impermeability grade is not less than P8...... The longitudinal and circumferential construction joints of the whole tunnel are coated with concrete interface agent and added with buried rubber waterstop, The inner edge of the circumferential construction joint of the arch wall shall be caulked with two-component polysulfide sealant. The circumferential construction joint shall be counted and listed as one 10m, and the longitudinal construction joint shall be counted and listed as two. Second lining arch
