1 Overview The power lighting power supply system is a professional in the urban rail transit, with a bachelor's degree in engineering.
The heavy position, its reliability and safety determine the operation quality of communication, signal, equipment monitoring (BAS), automatic ticket checking (AFC), disaster prevention alarm (FAS) and fire protection systems, especially in non-normal work. Under the condition, the reliability of its operation directly affects the safety of human life. It is an indispensable guarantee for the normal operation of the subway. Based on the above, the reliability and rationality of the power supply scheme of the power lighting power supply system are becoming increasingly prominent. The back grouting of the lining behind the lining is carried out after the lining strength reaches 70%. The construction process is: pre-buried pipe (lining) y pulping y grouting y inspection y test y refilling y acceptance sealing.
When filling the lining concrete, the grouting pipe pre-embeds a plastic grouting flower tube along the longitudinal direction of the tunnel at the vault waterproof board, and grouts the lining behind the pipe according to the concrete lining construction condition. The grouting material is cement mortar, and its mixing ratio: cement: sand: water = 1:3: 0.8. When grouting, the deformation of existing roadbed and lining concrete should be closely monitored. If abnormality is found, immediately reduce pressure or stop grouting. .
In order to determine whether the support measures can ensure the stability of the existing roadbed, the sinking of the existing roadbed is monitored and the slope is observed. Measuring point arrangement: 1 measuring point of each line of the two lines in the existing line reinforcement range, the spacing between the top of the hole is 2m, the distance between the sides of the hole is 5m. The measurement is made every 3h within one day after tunnel excavation. Later, according to the measurement results, it is extended to 6, 12, and 4 hours. At the same time, attention should be paid to the observation of the existing slope, whether there is cracking or abnormality.
4 Conclusion The construction of the eight-meter tunnel under the existing railway section lasted for 35 days. After the passage of the tunnel, three consecutive heavy rains were tested. The existing railway subgrade was in a stable state, and the tunnel support structure did not show any abnormality. The method of overhead reinforcement of the line, advanced support of the large pipe shed in the cave, step-by-step excavation of the positive step, strong support and lining are safe and feasible.
When shallow buried and weak surrounding rock tunnels are worn under existing railways, in order to ensure the safety of existing railway operations and tunnel construction, it is necessary to consider not only the tunnel construction method is safe, but also the reinforcement measures for existing railway lines; The length of the pipe shed should meet the requirements of passing through the existing railway section. The smaller the extrapolation angle is, the better; the lining construction of the shallow buried and weak surrounding rock tunnel should be followed by the excavation face, and it should not be carried out after the deformation of the surrounding rock is converged; The tunnel construction will proceed smoothly, and it is necessary to coordinate with the railway departments such as public works, electricity, and power supply to jointly maintain the safety of existing railways.
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