What are the tunnel excavation methods, a brief description of the tunnel excavation methods

Currently at home and abroad tunnel excavation methods are open cut method, cover digging along with the method, cover digging inverse method, cover digging half inverse method, dark excavation method, shield method immersed tube method.

1, open cut method:

Open cut method refers to the excavation of the ground, from the top down to the design elevation of the excavation, from the base of the bottom upward construction, the completion of the main tunnel structure, and finally backfill the pit or restoration of the ground construction method. Shallow buried subway stations and interval tunnels often use open cut method. Because the subway project is generally located in the urban area of dense buildings, so the main technical difficulties of deep foundation pit project is the protection of the original ten around the pit, to prevent surface settlement, reduce the impact on existing buildings.

2, cover digging and smooth operation method

Cover digging and smooth operation method is to complete the retaining structure in the surface work, with the stereotyped prefabricated standard overshaw structure, including longitudinal and transverse beams and road panels placed on the retaining structure to maintain the traffic, and then repeatedly downward excavation and addition of transverse support until the design elevation. Backfill is constructed sequentially from the bottom up. Finally, the exposed portion of the retaining structure is removed as necessary and the roadway is restored.

3, cover digging inverse method

Cover digging inverse method is the first in the ground surface down to do the pit maintenance structure and intermediate piles, pit maintenance structure is mostly used underground diaphragm wall or curtain piles, the intermediate support is mostly used to reduce the cost of construction of the main structure of the intermediate columns itself. Afterwards, the surface soil can be excavated to the ground elevation, and the top slab can be poured using the unexcavated soil as the soil mold. The roof slab can be used as a strong cross brace to prevent the maintenance structure from deforming into the pit, and the road can be restored and traffic resumed after backfilling.

4, cover excavation semi-reverse method

The difference between cover excavation semi-reverse method and reverse method only lies in the completion of the top plate and restoration of the road surface, downward excavation to the design elevation and then pouring the bottom plate, and then upward layer by layer to pour the side walls and floor slabs. In the semi-reverse method construction, generally must be set up cross-bracing and prestressing.

5, concealed excavation method

Concealed excavation method is in specific conditions, not digging up the ground, all underground excavation and repair of lining structure of the tunnel construction method. Concealed excavation method mainly includes: drilling and blasting method, shield method, roadheader method, shallow concealed excavation method, pipe jacking method, immersed tube method. In particular, the shallow excavation method and shield method is more widely used.

6, shield method

Shield is a shield can both support the ground pressure and can be advanced in the ground in the activities of the steel cylinder structure. The front end of the cylinder is equipped with a device to support and excavate the soil, the middle section is installed with jacks needed for jacking, and the tail can be assembled prefabricated or cast-in-place tunnel lining ring. For every ring of distance the shield advances, a ring of lining is assembled or cast-in-place under the support of the shield tail, and cement mortar is pressed into the void at the periphery of the lining ring to prevent the tunnel and the ground from sinking.

7, immersed tube method

Immersed tube method is the tunnel tube segments prefabricated in segments, segments of the two ends of the temporary stop head, and then floated to the tunnel axis, sunk in a pre-dug trench, complete the underwater connection between the tube segments, remove the head of the temporary stop head, backfill the trench to protect immersed tubes, paving the internal facilities of the tunnel, so that the formation of a complete underwater channel.

Extended information:

Tunnel excavation related technology:

1, pre-cracking blasting

Stone excavation, blasting in the main blasting area along the contour line of the design of the first burst a certain width of the penetrating cracks to buffer, reflect the excavation blasting. Buffer, reflect the vibration wave of the excavation and blasting, control its destructive influence on the retained rock body, so that it is more level excavation profile, this blasting technology for the pre-cracking blasting. Pre-cracking blasting is not only in the vertical, inclined excavation wall is widely used; in the regular curved surfaces, twisted surfaces, as well as the horizontal foundation surface is also used pre-cracking blasting.

2, into the hole

The hole section of the thin cover, poor geological conditions, when the depth of excavation to the arch line, the first into the hole guide wall and large pipe shed, to be completed after the lining of the open hole, lengthening the end of the shed, lap on the open hole, so that the end of the shed to form a fixed support, in the protection of the large pipe shed openings into the inner side of the wall, the two inner side of the wall guide pit should be staggered before and after the footage (5 ~ 10m). 10m). If it is a small spacing must also be set prestressed tensile anchors.

Baidu Encyclopedia-Tunnel Construction Technology