Subway tunnel seepage is a common and harmful phenomenon. If handled badly, it will not only affect the service life of the structure, but also the safety of traffic. The relatively weak link in the waterproofing of subway tunnels is the specific structure. Therefore, it is very important to deal with these particular places. It is necessary to accurately use the construction methods to ensure the waterproof material works and gain the best effect.
Construction joints are joints formed due to the construction methods and process. The construction joints are the weak link of concrete waterproofing, which could cause concrete to be discontinuous if not properly handled. Therefore, the poor construction joint treatment directly affects the overall waterproof . For the construction joint treatment, the best waterproof material is the one that on meeting water, it will expand. Therefore, it can fill the cracks in the construction joints. The water-based polyurethane is highly recommended and has the best ideal effect.
Before the construction of the grouting nipple, the concrete slurry on the surface of the construction joints should be first removed. Use high pressure air to sweep it thoroughly and make sure that the construction joints should be solid, smooth, dry and spotless. During the construction, the pressure should be stabilized and grouting should be continued. Then completely fill the construction gaps. Once leakage occurs in the construction joint of the pre-embedded grouting pipe, epoxy resin chemical slurry is injected through the repeatable grouting pipe, so that the slurry completely fills the pores of the water in the construction joint to achieve waterproof.The filling range of the slurry is not only limited to the surface of the construction joint, but also the seepage cracks and pores that penetrate the two sides of the construction joints. Before installing the grouting pipe, it is necessary to clean the construction joints once again. After cleaning, the grouting pipe shall be installed. The grouting pipe shall be installed at a position 10 cm away from the back surface of the construction joint. Before the construction, check whether the installation position of the grouting pipe is smooth. If it is not smooth after cleaning, the waterproof mortar can be used to level. Make sure that any part of the grouting pipe closely is attached to the surface of the construction joint, and the grouting pipe cannot have any hanging part. The grouting pipe is fixed with plastic buckles, and the buckle interval is set at 30 cm to avoid the pipe moving when concrete is poured. The pipe leads to the outside of the concrete at intervals of 5 to 6 meters and the leading length is not less than 15 centimeters, and also it should be at a distance from the construction joint which is no less than 20 cm. The open end of the conduit should be temporarily plugged to prevent foreign matter from entering; When ligating or welding reinforcing bars near the grouting pipe, special personnel should be arrange for supervising this construction, and temporary occluding measures should be adopted to protect the grouting pipe.