南京地铁应用人工地层冻结法的可行性研究

A Study on the Feasibility of Ground Freezing Method in Nanjing Metro Engineering

人工地层冻结技术用于采矿凿井在国外有 10 0余年的历史 ,在中国也有 4 0余年 ,然而 ,它在其它岩土工程中的应用尚处于起步阶段。本文以南京地铁珠江路—鼓楼区间为例 ,探讨了冻结法施工的可行性、设计方法、技术要点及其可能遇到的环境岩土工程问题。

The authors summarized the application of artificial ground freezing method (AGFM) to geotechnical engineering at home and abroad. Although AGFM has been used in mining shaft construction for over 100 years at abroad and over 40 years in China, its application in other geotechnical engineering is still in its beginning stage. Nanjing Metro will be built in a complicated and adverse geoenvironment, facing a series problems as the alternation of rockmass with soft soils, surface water, pore water in ancient buried river, karst water and fault water etc. Alternation of rockmass with soils makes the excavation hard in Shield Method and is difficult proof water and support in current NATM. Therefore, the authors suggest AGFM, and discuss its feasibility, design method and technical key points taking Zhu Gu section (from Zhujiang road station to Gulou station) as an example. Considering the unfavorable factors, which will be encountered in urban underground freezing engineering, we suggest that higher safety coefficient should be used in the ice wall design according to Lamé's formular. The authors also believe that the following environmental problems arising from AGFM deserve particular attention: weakening of mechanical properties of soil in freezing thawing cycle, freezing expansion and thawing collapse, additive stress on subject structure arising from the freezing thawing process and frost defect to concrete of underground structure. From engineering analogy, it can be concluded that freezing expansion and thawing collapse in the Zhu Gu section can be limited by building protection of effective engineering countermeasures.