Special-shaped liquid nitrogen freezing device and production and construction method

Abstract

The invention relates to a special-shaped liquid nitrogen freezing device and a production and construction method. The freezing device is suitable for being used for shallow portion short-time freezing in municipal engineering. A plurality of sections of U-shaped freezing pipe are installed in freezing holes in a long groove shape and in other irregular shapes, the two ends of the freezing pipe are connected to form a snakelike freezing system, and the mode that during traditional construction, circular liquid supply pipes are always arranged in large-diameter circular freezing pipes to forma round freezing circulation system is changed. During construction, the long-groove-shaped freezing holes are constructed in the ground, and the segmented U-shaped freezing pipe are fixed through anupper annular steel pipe and a lower annular steel pipe respectively, so that the freezing pipe is closely attached to a stratum around the freezing holes, the cooling capacity transfer effect betweenthe freezing pipe and the stratum is improved, and the liquid nitrogen freezing efficiency is improved. Vertical freezing pipe bodies with different temperatures are symmetrically distributed, the formed freezing wall is uniform through superposition of freezing effects, the speed for the freezing wall to extends upwards and outwards in the length direction of the freezing holes, and the formed freezing wall is good in stress performance.

Description

technical field [0001] The invention relates to a liquid nitrogen freezer, a production method and a construction method, and is especially suitable for a special-shaped liquid nitrogen freezer, a production method and a construction method suitable for the freezing construction of a short section of ground with a small depth in municipal engineering. Background technique [0002] In the construction of municipal engineering, it is often necessary to strengthen and improve the ground freezing in a short period of time to solve the technical difficulties encountered in the construction of underground structures in weak water-bearing strata. Liquid nitrogen freezing is an efficient and fast freezing method. It has been widely used in construction. A circular freezing pipe with a smaller diameter is lowered into the freezing hole, and a circular liquid supply pipe with a smaller diameter is lowered in the freezing pipe to form a freezing cycle of the circular pipe. During the ...

AI Technical Summary

Problems solved by technology

Due to the short length of the freezing pipe buried in the formation, when using a traditional liquid nitrogen freezer to freeze, the liquid nitrogen poured into the bottom of the freezing pipe is gasified and flows through the formation for a short distance, and the cooling exchange time between the liquid nitrogen and the surrounding formation is short and large Part of the liquid nitrogen has not had time to gasify and is directly discharged out of the freezing tube along with the nitrogen, resulting in waste of liquid nitrogen

At the same time, due to the short length of the freezing tube, the time for liquid nitrogen to exchange cold with the surrounding formation is short, not only will the freezing efficiency of the formation be low, but also the temperature difference along the length of the freezing tube is large, resulting in poor uniformity of the frozen wall

The freezing tubes in the traditional liquid nitrogen freezing construction are all round, so the shape of the freezing hole can only be circular. In order to facilitate the smooth insertion of the freezing tube into the freezing hole, the diameter of the freezing hole is generally larger than that of the freezing tube. As a result, the freezing pipe cannot be close to the formation around the freezing hole, and the gap between the two will also affect the transfer of cold energy, reducing the freezing efficiency of liquid nitrogen during the freezing process, so the freezing wall between the two freezing holes has high temperature and high strength. Low, often called interface in construction, is the weak link in the whole frozen wall

When the quality of the freezing pipe is large, the construction of the entire freezing pipe into the freezing hole requires the use of large machinery such as lifting equipment, and the construction process is complicated

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