复杂场地中盾构出洞水平冻结法现场试验

Field Test of Horizontal Freezing Method for Shield Tunneling in Complex Sites

目的研究复杂场地下盾构出洞水平冻结法冻结特性及对周围环境的影响,为今后类似工程提供指导。方法结合郑州地铁17号线双鹤湖站南端头盾构出洞水平环形冻结工程,基于现场试验,对冻结温度场及位移场进行系统研究。结果降温期间盾构推进注浆会造成测温孔测点温度小幅上升;邻近基坑降水导致左线各个测温孔降至0℃以下所用天数总体比右线多6 d;在平均含水率相差不大的前提下,粉砂在到达冰点后仍可继续以较快的速度降温;左、右线距离冻结管较远试验孔所测得的发展速度分别是较近试验孔的2.40倍、6.03倍;离冻结区越近,冻胀位移越大,冻结区最大冻胀量约是非冻结区的1.70倍。结论土质本身比平均含水率对冻结的影响更大;冻结壁向外扩展速度随着与冻结管距离的增加而变慢;盾构推进注浆对冻结效果影响较小,然而地下水的流动对降温以及地表竖向位移会有较大的影响,显著影响冻结加固效果。

In order to study the freezing characteristics and the influence on the surrounding environment of the horizontal freezing method of shield tunneling under the condition of complex site,combined with the horizontal annular type freezing engineering of the south end shield tunneling of Shuanghehu station of Zhengzhou metro line 17,the temperature field and the frost heave displacement field of the horizontal annular type freezing are systematically studied through the field measurement method.The results show that during the cooling period,the temperature of the measuring point will rise slightly.Due to the dewatering near the foundation pit,the number of days taken for each temperature measuring hole on the left line to drop below 0℃is 6 days more than that on the right line.The soil itself has a greater influence on freezing than the average moisture content of the soil layer.On the premise that the average moisture content is similar,the silt can continue to cool down at a faster speed after reaching the freezing point.The development speed measured by the test hole far away from the freezing pipe on the left line and the right line is 2.40 times and 6.03 times of that measured by the test hole near the freezing pipe,respectively.And the closer to the frozen zone,the greater the frost heave displacement.The maximum frost heave in the frozen zone is about 1.70 times of that in the non frozen zone.To sum up,the soil itself has more influence on freezing than the average moisture content.With the increase of the distance from the freezing pipe,the expansion speed of the freezing wall becomes slower.Shield synchronous grouting has little influence on freezing effect,but groundwater flow has great influence on cooling and surface vertical displacement,which significantly affects freezing reinforcement effect.