关键词: 盆形冻结, 地下工程, 砂卵石地层, 渗流, 冻结厚度

Abstract: Basin-shaped freezing technology is applied to form a water-proof structure, which consists of two parts: the frozen curtain (basin wall) around the excavation zone and the horizontal frozen body (basin bottom) at the bottom of the excavation zone. In this paper, physical model test and numerical simulation were used to study temperature field expansion of basin-shaped technology under static water and 0.5 m/d seepage condition in water-rich sandy gravel stratum of Beijing. As a new application of freezing method in the field of municipal engineering, basin-shaped freezing technology can effectively play the role of water proofing. Different parts of basin structure show different frozen orders under different seepage conditions. Under the condition of static water, the basin wall is frozen prior to the basin bottom. While under the condition of seepage, the order of the freezing intersection of different positions is basin wall along the seepage, basin bottom, basin wall on the back surface and basin wall on the face surface in sequence, the freezing of basin wall is the key factor to restrict the basin-shaped freezing under this condition, and basin wall should be focused in the actual engineering. Freezing thickness is the most direct index to evaluate freezing effect. The freezing thickness of the basin wall tends to be stable under the condition of static water, and the freezing thickness of the basin bottom gradually exceeds the length of the freezing tube at the basin bottom and develops in both directions of in and outside the basin structure. Under seepage conditions, the freezing curtain of the basin wall with the smallest thickness appears on the front-water surface, while the local thickness of the freezing curtain on the basin wall of the back-water surface increases, and the horizontal freezing plate thickness at the basin bottom is only one-way develops inside of the basin.

Key words: basin-shaped freezing method, underground engineering, sandy gravel stratum, seepage, freezing thickness