界面水条件下暗挖地铁车站埋深的合理选择

Selection of Appropriate Cover Depth for Mined Metro Station under Interfacial Water Condition

根据经验,第四系地层中暗挖地铁车站的埋深常常设置为6-8 m,若车站隧道拱部位于界面水影响范围,则车站施工采用常规支护手段难以保证安全。为了有效规避暗挖地铁车站在富水界面时的施工风险,结合北京地铁9号线军事博物馆站设计过程,通过现场抽水试验和计算分析,提出设计阶段应重视水文地质研究,选择车站合理埋深使其拱顶避开界面水影响范围,提高施工安全性。车站拱部留设的防水保护层厚度据水头高度和隧道开挖跨度确定为4.5 m;施工过程中应加强超前探测,结合探测结果设置帷幕注浆或自进式锚杆等拱部超前支护措施。埋深加大后结构钢管柱应根据受力情况进行加强。

In normal cases, 6 -8 m cover depth is taken for mined Metro stations in Quaternary strata in accordance with experience. If the arch of the Metro station tunnel is located in the influence scope of the interfacial water, the safety of the construction of the Metro station cannot be guaranteed by the conventional support means. In the design of the Military Museum station on Line 9 of Beijing Metro, field water pump tests are conducted, and calculations and analysis are made, so as to minimize the risks in the construction of the mined Metro station close to water-rich interface. Conclusions drawn are as follows：1 ） In the design stage, emphasis shall be paid to the study on the hydrogeological conditions and appropriate cover depth shall be selected for the Metro station so that the crown of the Metro station will not be located within the influence scope of the interfacial water and the construction safety can be improved;2 ） The thickness of the waterproof protection strata reserved on the top of the arch of the Metro station is determined as 4 . 5 m in accordance with the water head and the tunnel excavation width; 3 ） During construction, advance probing shall be emphasized and advance reinforcement measures such as curtain grouting and self-boring bolts shall be taken on basis of the advance probing results; 4 ） Due to the increase of the cover depth, the structural steel pipe columns shall be strengthened according to the force-undertaking conditions.