呼和浩特市地铁联络通道冻结施工监测与分析

Monitoring and Analysis of Freezing Construction for Contact Passage of Hohhot Metro

内蒙古呼和浩特市地铁2号线1号联络通道采用冻结法施工,冻土帷幕的发展情况是确保联络通道顺利开挖的关键.基于现场监测数据,对该地区的温度场、泄压孔压力进行数据分析研究,研究表明:冻结场的温度在冻结前期变化较大,在冻结后期逐渐平缓,且温度均低于-10℃;通过对比,C2测温孔的降温速度大于C1测温孔的降温速度,因此土体所在位置冻结管排布密度越大且越靠近冻土帷幕内侧,土体温度降温速率越快;泄压孔可以及时监测土体内冻土帷幕是否交圈,泄压孔压力在冻结16 d后恒定在0.23 MPa,此时冻土帷幕开始交圈;通过公式计算得到冻土帷幕最小厚度2.358 m,平均温度-11.04℃,均符合设计开挖要求.通过分析得出该地区的冻结管设计方案安全可靠,以期对往后类似工程提供参考依据.

The No.1 contact channel of Hohhot Metro Line 2 in Inner Mongolia is constructed by freezing method.The development of frozen soil curtain is the key to ensure the smooth excavation of the contact channel.In the report,based on the field monitoring data,the temperature field and frost heaving force in the region were analyzed.The results showed that the temperature of the freezing field changes greatly in the early stage of freezing,and gradually flats in the late stage of freezing,and the temperature is lower than-10℃;the cooling rate of C2 temperature measurement hole is greater than that of C1 temperature measurement,therefore,the larger the arrangement density of freezing pipe in the soil is and the closer it is to the inside of frozen soil curtain,the faster the temperature cooling rate of soil is;the pressure relief hole can timely monitor the frost heaving force of soil,when the frost heaving force is constant at 0.23 MPa after 16 days of freezing,the frozen soil curtain begins to circle.Based on the formula calculation,the minimum thickness of frozen soil curtain is 2.358 m,and the average temperature is-11.04℃,which meets the design and excavation requirements.The analysis results suggested that the design scheme of freezing pipe in this area is safe and reliable,and which can provide references for similar projects in the future.