Analysis: Basement plugging construction measures

Basement plugging construction measures: According to the importance of the project and the requirements for plugging in the basement during use, determine the basement plugging level of the underground project, and use the combination of ‘anti-discharge, discharge, interception and plugging’ for different parts of the project. Soft and harmonious, adapt to local conditions, comprehensive management. 1. Anti-discharge combination The underground foundation pit is supported by the cement-type mixing pile gravity retaining wall to form a water-stop curtain around the foundation pit, and the deep-water precipitation point is arranged in the supporting foundation pit through the design of the precipitation. Basement plugging Before the earthwork excavation in the basement, the well group pump is started to carry out the precipitation, so that the groundwater level is kept 30cm below the basement plugging layer during the construction of the underground basement. The ground water around the foundation pit is discharged into the surrounding open ditch, which ensures that the basement structure basement is blocked during construction without water and mud. 2. Rigid basement plugging Determine the impermeability level of the basement plugging in the basement project. The structure is sealed from the basement. The pumping UEA is used to compensate for the shrinkage enthalpy. The UEA blends a large amount of 8% to 10% of the cementitious material. The limiting expansion ratio of UEA is 2~4×104-4, which can increase the strength of bismuth by 10%~30%, increase the impermeability by 2 times, and improve the freeze resistance and sulfate resistance. It has no rust effect on steel bars. There is also the advantage of retardation, which can compensate for the temperature difference shrinkage of bismuth. The combination of retarding and water reducing agent is one of the best measures to reduce the cracking of large volume bismuth. It can effectively suppress the void ratio inside the sputum and increase the porosity. The interface is dense, so as to achieve the purpose of plugging in the basement. The integrity of the basement plugging large volume 砼 foundation is high, so the raft should be layered and stratified (typically 30cm ~ 40cm). The basement of the basement plugging cement base is required to be smooth, clean and moist, with sufficient strength, and the yin and yang angles are rounded. The liquid material and the powder material are used in a ratio of 1:1 and fully stirred, and the prepared paint should be used up in time; the construction sequence is the additional layer reinforcement treatment such as the first yin and yang angle, and then the façade construction. During the construction, if the base layer is too dry, it is necessary to use a dilution material to make a base. The first coating should be thinner and uniform when applied. Generally, it is 3 to 5 times, and the dosage is (3 to 5) kg/m2. After the first coating film is dried, the second coating can be performed, and the second coating direction should be perpendicular to the first pass. After the same, the thickness of the coating reached 1.5mm. The paint contains cement components and is easy to bond with cement materials. Therefore, the protective layer of cement mortar and masonry materials can be directly applied to the coating, but it needs to be carried out after the basement plugging layer is dried. After the underground outdoor wall completes the underground chamber plugging treatment, the gap between the foundation pit and the outer wall is backfilled with cohesive soil to change the soil layer environment, artificially reduce the permeability of the soil layer in the foundation pit, and then achieve the purpose of plugging the basement. 3. Post-casting with basement plugging treatment The post-casting belt is the junction of the second stage and the first stage, which is a weak part of the basement plugging function, which is very likely to cause leakage, and should be paid special attention. Therefore, in order to prevent the occurrence of vertical cracks, on the basis of the original design drawings, a plurality of telescopic post-casting belts are additionally added to ensure that a post-casting belt is disposed every 30m to 40m. A long closed steel plate waterstop is arranged in the middle of the back pouring strip thickness, and the joint is fully welded to improve the quality of the basement plugging of the post-casting strip. Before the construction of the post-casting belt, first remove the wooden molds or fine wire mesh on both sides, clean the surface of the loose concrete, the surface is chiseled, wet for more than 48h, and check whether the template leaks. A post-basement plugging coating shall be added to the post-casting zone, and a layer of 100-thick 1.4 m wide crucible cushion shall be added to the back-casting strip of the bottom plate according to the design requirements, with a bidirectional reinforcing mesh. The construction interval between the post-casting and the cast-in-place concrete on both sides shall be at least 2 months. The post-casting construction temperature should be lower than the temperature of the cast-in-place concrete on both sides. This is to reduce the temperature gradient between the inner and outer crucibles, thus reducing the crack caused by the shrinkage deformation under the restriction. The ground guarantees the construction quality of the post-casting belt. After the final condensation, the sack is covered and watered for maintenance, and the curing time is generally not less than l4d.

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