Discussion on Tunnel Construction Technology Paper 1 Tunnel Construction Technology
Abstract: In traffic construction, tunnels occupy a very important position. Tunnel construction is a very complicated project. Mastering tunnel construction technology can well grasp the quality of tunnel construction, which is of great significance to the safety and quality of traffic engineering.
Abstract: Tunnel plays a very important role in traffic construction. Tunnel construction is a very complicated project. Mastering the quality of tunnel construction technology can help us master tunnel construction well, which is of great significance to the safety and quality of traffic construction.
Keywords: tunnel construction; Problems; Architecture; Technology; way
Keywords: tunnel construction; Problems; Architecture; Technology; way
China Library ClassificationNo.: U455.4 Document ID: A DocumentNo.:1006-4311(2014)14-0098-02.
Introduction to 0
With the gradual expansion of highway tunnel construction scale, the two-car tunnel is far from meeting the growing traffic demand, and the three-car tunnel has been widely used in practice. However, the larger the tunnel, the more complicated the technology. Therefore, compared with ordinary highway tunnels in the past, it is qualitatively different in design, construction and operation management, which brings challenges to highway tunnel builders. Based on my own working experience, this paper analyzes the construction technology of highway tunnel.
1 Common construction techniques and existing problems of tunnel engineering in China
At present, the main construction technologies in China are: deep seabed compression construction technology; Deep hole drilling and blasting construction technology; Ultra-shallow buried shallow excavation technology; Auxiliary engineering construction technology; Shield construction technology; Open new excavation technology; Environmental protection construction technology; Many other new technologies, such as deep buried pipeline technology.
There are also many problems in the construction process. As far as the development of tunnel engineering is concerned, there are mainly the following problems: insufficient understanding of soil structure leads to unreasonable determination of construction scheme, resulting in the present situation of bean curd residue engineering; ② The quality of plateau frozen soil railway is difficult to guarantee and its durability is weak; ③ The compression effect of subsea tunnel can't meet the actual requirements, and deformation problems often occur; (4) The development of new technologies is slow, which cannot meet the needs of social construction and needs to be improved urgently; ⑤ Environmental protection tunnel technology is not in place, which leads to the phenomenon that the environment is destroyed from time to time; ⑥ The tunnel engineering construction system lacks unified construction standards, which often leads to unscientific construction.
2 technical preparation for construction preparation period
2. 1 construction environment investigation ① We classify the surrounding rocks according to the review of geological drilling data. It is not difficult to see that if the analysis of strata strike, folds, faults, groundwater and special soil is wrong, it will have a very serious impact on the construction. (2) targeted inspection of the construction site, mainly including geology, water supply, meteorology, drainage, raw materials, power supply, transportation conditions, waste residue, site, etc. For holes and shallow buried sections with serious weathering accumulation, there should be a perfect treatment or compensation scheme.
2.2 Preparation of construction materials, equipment and schemes ① If the site laboratory meets the requirements of temporary qualification examination and approval of the quality supervision station within the time limit, we need to have sound test equipment, technicians and a sound management system. When the contractor signs a contract with the owner, the supervision engineer may require the contractor to carry out various preparatory work according to the contract commitment and the time stipulated in the contract. (2) Before construction, the supervision project shall repeatedly check the external control points at both ends. (3) The contractor shall timely report the overall plan and specific implementation plan according to the date stipulated in the contract, so as to ensure the supervision engineer to conduct a comprehensive investigation and analysis of the project, and then discuss, clarify and modify the problems with the contractor.
3 Construction method
There are six main tunnel construction methods: full-face method, bench method, bench division method, upper (lower) heading method, single-side heading method and double-side heading method.
At present, tunnel construction in China is mainly based on NATM, and the essence of NATM construction is that surrounding rock, as a part of support, bears the pressure of overlying load. Using NATM for tunnel construction has obvious advantages in progress, quality and project cost. However, due to the difference of design support form and construction technology, the construction technology and support form should be adjusted according to the surrounding rock properties and geological changes during construction. In the construction of long-span tunnel, the main methods we choose are: upper half-section step method, middle wall method and double-arm heading method (glasses method).
4 Main technical analysis of tunnel construction
4. 1 construction technology of weak and broken surrounding rock section In view of the possible large deformation of weak surrounding rock, the U-shaped steel arch composite lining means of adding reserved deformation, bolting and shotcreting, anchor rod, steel mesh and contractibility is adopted, the initial support is closed in time, and the concrete can be sprayed for 2-3 times, then the monitoring and measurement are strengthened, and the feedback information is used to guide the construction. When passing through the water-rich section of the weak and fractured zone, the water should be controlled first, and the combination of drainage and plugging should be adopted. During the excavation, experienced geological engineers will be on duty 24 hours in turn to monitor the geological changes in time and guide the site construction.
Strengthen monitoring and measurement. When the initial support deformation is abnormal and there is no convergence trend, it is necessary to adjust the support parameters and implement secondary lining if necessary. Therefore, secondary lining is a measure to increase steel bars and improve concrete strength.
4.2 Tunnel anti-leakage and anti-collapse technology ① Anti-leakage technology. The secondary lining of tunnel is mainly to improve the impermeability of concrete and also to avoid expansion. Its main function is to prevent local water seepage caused by rupture of composite waterproof board. Therefore, we should design the layout of blind ditch according to the increase of water quantity to better facilitate drainage. In the construction of waterproof board, it is necessary not only to strictly check the welding conditions of weld seams, but also to ensure that construction joints and deformation joints are watertight. ② Anti-collapse technical measures. Shock absorption blasting is adopted to reduce the disturbance to surrounding rock. After excavation, shotcrete and other initial support shall be applied in time to make the surrounding rock reach a stable state as soon as possible. For the area with poor self-stabilization ability of surrounding rock, advance support or advance reinforcement should be adopted for the surrounding rock in front, and the construction should be organized according to the principle of roof protection first and then excavation. When the deformation of primary support is abnormal and there is no convergence trend, primary support strengthening measures should be taken to carry out secondary lining in advance. In the secondary lining, measures such as increasing steel bars and improving concrete strength have been taken. According to the geological survey data, the included angle between the rock stratum and the tunnel axis is small. Therefore, measures such as reducing circulating footage, strengthening advanced support and strengthening surrounding rock are taken to prevent it. Water control should be carried out first in the water-bearing section of surrounding rock: rubber belt blind ditch should be set for drainage when there is seepage; When the seepage area is large, rubber belt blind ditches can be set side by side. When there is concentrated water flow, a spring blind ditch is set for drainage to minimize the influence of water pressure on the initial support. In order to strengthen the control of the construction process, experienced geological engineers are on duty 24 hours a day during the excavation to monitor the geological changes in time and guide the site construction. In the weak and unstable surrounding rock area, the main leaders take turns to be on duty, strengthen management, be strict with requirements and deal with emergency problems in time.
4.3 Waterproof and Drainage Construction Technology ① Waterproof for construction joints and deformation joints. Construction joint is mainly caused by cold joint of tunnel lining concrete during construction, and it is also the weak link of waterproof, which is the most prone to leakage in the whole tunnel. Therefore, when lining the tunnel, it should be avoided that improper treatment will affect the normal use of the tunnel and traffic safety, and seriously reduce the strength and durability of the structure. In order to prevent uneven lining from cracking, we need to set settlement joints to avoid lining cracks caused by concrete shrinkage due to drastic temperature changes. ② Waterproof concrete. The secondary lining concrete of tunnel is not only the bearing structure of external force, but also the last waterproof defense line. However, most waterproof concrete is mixed according to the specified grade and a small amount of additives are added. Waterproof concrete with certain impermeability was prepared by adjusting the mixture ratio. The impermeability grade of secondary concrete required by China Railway Tunnel Engineering Technical Guidelines shall not be lower than P8.
4.4 Construction technology of tunnel secondary lining ① Reinforcement processing and installation. The rebar is processed by special processing equipment, and the rebar joint is mainly welded by one side, and the welding length is generally not less than 10d. The main purpose of steel bar welding is to ensure the weld is full and chisel away the welding slag. Self-made trolley shall be used for installation, and construction shall be carried out according to the design size and protective layer during installation. (2) pouring concrete. After the trolley is in place, the end can be sealed tightly with pine boards. The pipeline of the concrete delivery pump is connected to the mold through the skylight on the upper part of the trolley, and at the same time, the concrete delivery truck pours concrete into the delivery pump, and the delivery pump presses the concrete into the mold through the pipeline.
5 concluding remarks
In tunnel construction, we should strive to control the quality of tunnel construction and achieve optimization under the guiding ideology of safety, order, high quality and high efficiency. Constantly update the tunnel construction technology, and adopt appropriate construction technology for each control point to ensure the tunnel construction quality.
References:
Edited by Chen Xiaoxiong. Tunnel construction technology [M]. Beijing: People Communications Publishing House, 20 1 1, 6.
[2] Wang Haonan, Overview of Tunnel Construction Technology Quality Control [J]. Highway Construction and Management, 20 12.
[3] Feng Xu. Construction management technology of Xuefeng Mountain extra-long tunnel [J]. Science and Technology Innovation Guide, 2009.
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