地铁联络横通道水平冻结施工的热固耦合分析

基于考虑相变的热固耦合理论,采用GEO-SLOPE软件模拟地铁联络横通道水平冻结和开挖施工过程,分析地层温度场和位移场的变化规律。结果表明:隧道冻结帷幕交圈的时间约为26d,但需积极冻结到40d,冻结帷幕平均厚度达到120cm,再经过36d的维护冻结期才可实施开挖;在维护冻结期采用比积极冻结期略高的盐水温度,防止了冻土范围继续扩大,避免了隧道开挖过程中遭遇强度较高的冻土;在进行具体的冻结设计时,应结合地层和隧道轮廓线的特点,设定冻结盐水温度、冻结时间、冻结管间距和冻结管数量等参数;对比分析不同冻结帷幕保护下隧道开挖的地层位移场,结果证明冻结对抑制地层变形具有良好的效果,但需要足够的冻结时间方可将地表变形限制在可接受的范围内。

Thermal-Solid Coupling Analysis of the Connected Cross Aisle inMetro Constructed by Horizontal Freezing in Ground

Based on thermal-solid coupling theory in consideration of phase change,and with the help of GEO-SLOPE software,the complete construction process of the horizontal ground freezing and excavation of the connected cross aisle in metro were simulated,and the variations of temperature field and ground displacement field were analyzed.Results show that it would take 26 days for the freezing curtain of tunnel to enclose,and 40 days active freezing for the average thickness of freezing curtain to reach to 120 cm.After that,the freezing curtain should have been maintained for 36 days before the excavation is carried out.Higher temperature of salt water was adopted during the period of maintaining than it was during the active freezing period to prevent the area of frozen soil from expanding in order to avoid encountering frozen soil of higher intensity during the excavation.During the specific freezing design,the characteristics of ground and tunnel profile should be considered to set the corresponding parameters such as the temperature of freezing salt water,freezing time,and the spacing and number of freezing pipes.Contrasts and analyses were made between ground displacement field resulted from tunnel excavation under different thickness protection of freezing curtain.Results have proved that freezing has favorable effect on restraining the ground from deformation,but it demands adequate freezing time to limit ground displacement within the acceptable range.