Method for detecting thickness of frozen soil curtain of urban underground large-scale freezing project

Abstract

The invention discloses a method for detecting the thickness of a frozen soil curtain of an urban underground large-scale freezing project. The method is suitable for being used in the urban underground large-scale project. The current focusing principle is adopted, the current of an emitting electrode is compressed into a limited height range, a freezing pipe in the height range is insulated, and therefore it is guaranteed that the current is propagated in a nearly tubular mode, and the tubular current propagation equivalent area is calibrated through a model test; the apparent resistivity of a frozen soil-unfrozen soil-frozen soil system between an emitting electrode and a receiving electrode is calculated based on the voltage and current of the emitting electrode, the function relation between the frozen soil curtain thickness and the apparent resistivity on a current propagation path is established, and then the frozen curtain thickness detection method based on cross-hole resistivity measurement is achieved by utilizing the condition of adjacent freezing pipes. According to the method, the current propagation range is narrowed, the apparent resistivity measurement precision is improved, a traditional strong nonlinear inversion problem is simplified into a one-dimensional linear problem, and the method has the advantages of being simple, economical and practical.

Description

technical field [0001] The invention relates to a method for detecting the thickness of a frozen soil curtain, in particular to a method for detecting the thickness of a frozen soil curtain for large-scale urban underground engineering frozen soil curtains. Background technique [0002] Since the freezing method was first used in the Swedish pedestrian tunnel project (total length 24m) in 1886, the municipal freezing project has a history of 134 years. Since my country adopted the freezing method for the first time in Beijing subway project in 1973, the number of urban underground freezing projects has exceeded 200. For more than a century, a large number of basic achievements have emerged in the aspects of artificial frozen soil water, heat, and force multi-field coupling laws, freeze-thaw ice formation mechanism, theoretical models, freeze-thaw control, etc. However, the monitoring of permafrost curtain shape and anomaly early warning seriously lag behind the basic resear...

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Problems solved by technology

The electrical method has low cost, and the electrode is easy to miniaturize, which can better meet the fine measurement requirements of small-scale targets, but it needs to face the interference of the urban underground environment, especially the interference of steel frozen pipes (low resistance)

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