北京砂卵石地层盆形冻结的温度场扩展规律研究

地下工程盆形冻结止水结构包括位于开挖范围周围的冻结帷幕（盆壁）及开挖范围底部的水平冻结板（盆底）两部分。采用物理模型试验与数值模拟的方法，分析了北京典型富水砂卵石地层条件下盆形冻结在静水及0.5 m/d渗流条件下的温度场扩展规律。研究发现：盆形冻结技术作为冻结工法在市政工程领域的全新应用，对地下工程的施工区域能够有效起到冻结止水效果；盆形结构不同部位在不同的渗流条件会表现出不同的冻结交圈次序，静水条件下盆壁冻结管会先于盆底冻结管交圈，渗流条件下则依次是顺水流盆壁、盆底、背水面盆壁、迎水面盆壁，此时盆壁冻结是制约盆形冻结的关键因素，实际工程应重点关注盆壁冻结；冻结厚度是评价冻结效果最直观的指标，在静水条件下盆壁厚度趋于稳定，盆底水平冻结板厚度逐渐超过盆底冻结管长度且向盆内与盆外两个方向同时发展；渗流条件下，迎水面盆壁厚度最小，背水面盆壁由于绕流现象出现冻结锥体而局部厚度增大，盆底水平冻结板厚度仅向盆内单向发展。

Temperature field expansion of basin-shaped freezing technology in sandy pebble stratum of Beijing

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.