Study On New Supporting Technology Combined With Artificial Ground Freezing Under High Artesian Head In Saturated Soil Layers During Deep Foundation Pit Excavation

The artificial ground freezing method has many advantages, such as sealing water, adapting for various complicated environment and geology conditions, and good environmental protection function. It has been extensively used in the engineerings, like tunnel, subway, bridge, foundation pit and other engineering areas.Through analysis of application of artificial ground freezing in tunnel, foundation pit and other areas inland and abroad, based on the engineering supporting of Yangtze River tunnel shield well in Wuhan, the paper researchs how to support the foundation pit excavation with the artificial ground freezing method under high water pressure in rich water soil layers conditions. Combining the principle of the soil-mixing wall, the paper suggests a new supporting method, in which the artificial ground freezing wall serves as sealing water structure, at the same time large structure steels will be inserted into the artificial freezing soil layers to increase the strength of freezing soil layers. In order to obtain the shear strength of the artificial freezing soil layers in site, direct shearing tests are carried out with undisturbed samples under the artificial freezing condition. The focus of the paper is the new combined supporting technology with artificial ground freezing, which includes how to combine the strength of freezing soil all with the strength of structure steels, and to design the thickness of freezing soil wall combined with structure steels. Strength and stability of the combined supporting structure are checked, and the design method for freezing system and monitor the deep foundation pit excavation is presented. Through this series of study on the freezing soil wall, we hope to get the method of design and construction of new combined supporting technology with artificial ground freezing, and to provide a application reference at the deep foundation pit excavation for applying the artificial ground freezing.