富水砂砾地层盾构液氮冻结常压开仓施工技术

为了解决富水砂砾地层中盾构区间前盾范围的土体加固,使得盾构机具备常压开仓换刀的条件,考虑到液氮气化时剧烈吸热的原理,提出了采用液氮冻结技术快速冻结土体的解决思路。通过地面施工垂直钻孔,并下放液氮冻结管,液氮气化吸热,直至冻结面及周围土体,对盾构机前盾1.5 m范围的土体加固。实践证明,在富水砂砾地层中其它封水措施效果达不到安全要求的情况下,液氮快速冻结技术取得了理想效果。

Construction Technology for Shield Opening Chamber at Atmospheric Pressure in Water-rich Sand and Gravel Strata

In order to solve soil reinforcement at the front of shield in water-rich sand and gravel strata,the condition was satisfied for shield to open chamber at atmospheric pressure.Solution thought was proposed to rapidly freeze soil by liquid nitrogen freezing technology in consideration of the principle of vigorous heat absorption during liquid nitrogen gasification.The soil was reinforced at the 1.5 m ahead of shield by vertical drilling from ground surface,placing down the freezing pipe of liquid nitrogen.Liquid nitrogen was gasified to absorb heat until freezing ahead and around soil.The practice proved that ideal result was reached for liquid nitrogen to rapidly freeze,when other measures of prevention water couldn’t meet safe demand in water-rich sand and gravel strata.The research result could provide certain reference for similar complex geological conditions of shield to open chamber and change cutting tools at atmospheric pressure.