Tunnel belongs to underground engineering. Groundwater is shown in many forms during construction, and groundwater is corrosive in general, which is harmful to tunnel support, especially secondary lining. If groundwater can not be discharged in time and effectively, once it penetrates into lining, it will cause serious corrosion to lining concrete and reinforcement, which will affect the strength of the whole lining, thus affecting the strength of the lining. It greatly shortens the service life of the project and causes irreparable huge losses, so the tunnel waterproof and drainage construction is very important. Tunnel waterproofing and drainage construction is of great importance, and the construction is not complicated. The key is to fully recognize its stakes. The constructors should be careful and skilled in operation, so as to ensure that the tunnel waterproofing and drainage meet the requirements of design and specifications.
Laying waterproof board
In the design, the waterproof board is laid without nails. In order to facilitate the laying and fixing of waterproof slabs, the waterproof slabs about 5 cm wide should be fixed on geotextiles along the tunnel longitudinally with hot-melt pads, with a longitudinal distance of 1 meter, to determine the width of the waterproof slabs and the location of the tunnel; to lay on both sides from one side to the other, and to ensure a certain degree of tightness and smoothness; to fix the waterproof slabs and hot-melt pads by manual special welders. The bonding spalling strength is not less than the tensile strength of waterproof board, and the lapping width of adjacent parts should be 10-20 cm, but not less than 10 cm. The adjacent parts of waterproof board should be bonded by a special Jeint crawler welding machine. Before welding, the bonding parts should be wiped clean to prevent the bonding quality from being affected by dirt and other contaminants. The temperature of crawling welding is 400 degrees Celsius, and the speed is about 1.5-2 m/10 seconds. Personnel should cooperate closely with each other. The climbing welding machine needs to be leveled by hand to facilitate smooth and smooth passage of the machine. This can prevent the phenomenon of bulging and exposed welding and reduce welding breakpoints. For the insufficient length of waterproof board, the connecting part should be based on the principle of reducing the number of lap joints, preventing cross joints and facilitating manual welding. It is suggested that the whole waterproof plate be overlapped longitudinally, so that the joints are generally T-type, and the number of joints is greatly reduced. For those parts that can not be bonded by climber welding machine, such as T-type joints, manual welder should be used to weld them, and then a circular waterproof plate with radius of 1.5 times the length of T-type joints should be used to cover them and weld them adequately with manual welder. Geotextiles and waterproof boards are laid not less than 1 meter in advance in longitudinal direction, but not more than twice the length of formwork trolley.
Notices needing attention in construction:
Weld quality does not meet the requirements: because the speed and temperature of climbing welding machine can not be well mastered, it is easy to appear that the pressure can not meet the requirements of specifications within the specified time, or the phenomenon of bursting and leaking gas when checking the weld quality of waterproof board by aeration test.
The construction operation and the cooperation between workers are not standardized: during the construction process, the constructors can not cooperate closely and the operation is not standardized, which causes many unnecessary troubles. For example, the temperature of the climbing welding machine is not in place and blindly carried out, resulting in a false welding phenomenon. The irregularity of the weld seam and the phenomenon of exposed welding occur when the cooperation between workers is not good.
Damage waterproof board when steel bar is used: when lining steel bar is positioned, welding slag and open fire easily damage waterproof board, and when steel bar is installed, the end of steel bar pierces waterproof board.
All departments should work together to ensure the quality of the project.