At this stage, how do tunnel construction companies in my country carry out tunnel construction? What is the basic overview of tunnel step construction methods? The editor of Zhongda Consulting has compiled the basic content of tunnel excavation methods as follows:
Zhongda Consulting has compiled the knowledge from the construction knowledge column of this website and the basic information of tunnel excavation methods is as follows:
Tunnels are engineering buildings buried in the ground and are a form of human utilization of underground space. The structure of the tunnel consists of two parts: the main building and ancillary equipment. The main building is composed of a cave body and a door. Ancillary equipment includes car shelters, firefighting facilities, emergency communications and waterproofing and drainage facilities. The long tunnel also has special ventilation and lighting equipment. Zhongda Consulting takes the step method in the tunnel excavation method as an example. The basic situation is as follows:
Basic procedures of the tunnel excavation method:
Upper half section: measure the center line and horizontal line → draw out Contour line → Drilling → Charging and blasting → Ventilation and dust removal, removal of dangerous rocks → Installation of arch frames, setting up locking anchors and mechanical connecting steel bars → Advanced support, system anchors, hanging mesh spray concrete support → Advanced injection Slurry → slag discharge → check clearance → next cycle.
The excavation is from top to bottom, the lining is from bottom to top, the inverted arch is closed in time, the second lining is followed in time, and the entire tunnel forms a closed circle as soon as possible.
Basic overview of the tunnel excavation method: the step method:
The step method is to excavate the upper half section first, and then excavate the lower half section at the same time after the excavation reaches a certain length. The construction method of half-sections advancing simultaneously; there are three types according to the length of the steps: long steps, short steps and ultra-short steps. In recent years, due to the design of large-section tunnels, there are three-step temporary invert methods and even multi-step methods.
As for which step method should be used in construction, it must be decided based on the following two conditions:
(1) The time requirements for the initial support to form a closed section, the surrounding rock overhang The worse, the shorter the closing time requirement;
(2) Requirements on the size of the construction site for excavation, support, ballast removal and other mechanical equipment used in the construction of the upper section.
In weak surrounding rock, the former one should be given priority and the latter should be taken into consideration to ensure construction safety. When the surrounding rock conditions are good, the main consideration is how to better utilize the mechanical efficiency and ensure the economical construction, so only the latter condition is considered.
Advantages and disadvantages of the step excavation method:
The step excavation method can have sufficient working space and considerable construction speed. However, there is interference in the upper and lower operations; although step excavation increases the number of disturbances to the surrounding rock, the steps are conducive to the stability of the excavation surface. Especially after the upper part is excavated and supported, the lower part operation will be safer, but attention should be paid to the impact on the upper part stability during lower part operation.
The following points should be noted when excavating steps:
(1) Solve the problem of mutual interference between the upper and lower half-section operations. Micro-steps are basically combined into one working surface for synchronous excavation; long steps are basically pulled apart and have less interference; while short steps have greater interference, so attention must be paid to the organization of the work. For shorter tunnels, the upper half section can be penetrated and then the lower half section can be constructed.
(2) When excavating the lower part, attention should be paid to the stability of the upper part. If the stability of the surrounding rock is good, excavation can be carried out in sections; if the stability of the surrounding rock is poor, the lower excavation cycle footage should be shortened; if the stability is worse, it can be staggered left and right, or the middle trough can be dug first and then dug. Side gang.
(3) The lower side wall must be sprayed with concrete immediately after excavation, and initial support must be provided in accordance with regulations. (4) The measurement work must be carried out in a timely manner to observe the displacement values ??of the vault, arch feet and the middle of the side walls. When the velocity is found to increase, the inverted arch must be closed immediately.
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