冻结法施工旁通道的冻土压力现场监测方法

In-situ monitoring method for frozen soil pressure during cross passage construction by freezing method

冻结法广泛用于盾构隧道的旁通道施工,但设计上对于冻结引起的作用在隧道上的冻胀力还没有明确取值方法,其主要原因之一是缺乏现场测量数据。以上海长江隧道的旁通道施工为背景工程,采用新型土压力计监测。首先介绍了PAD式土压力计的基本特征和安装方法,然后介绍了自动数据采集和测点设置原则,接着通过实例重点说明电缆保护的重要性和保护措施。上述监测工作保证了全部5个土压力计的正常工作,并获得了有效的实测数据。数据显示,冻结工法造成的最大荷载增量远小于预期值,这主要是由于施工上设置了泄压孔,从而减少了作用在管片上的冻胀力。

Artificial freezing method is widely used in construction of cross passage for shield tunnel, while due to lack of measurement data, no clear rule for determining frost-heave force is given for tunnel design. Based on the Shanghai Yangtze River Tunnel project, a careful in-situ monitoring is carried out by utilizing a new type earth pressure gauge. Firstly, the main characteristics of PAD type earth pressure gauge and the installation method are introduced. Secondly, the automatic data collection system and the layout of measuring points are described. Aforementioned efforts successfully protect all 5 gauges, and valid data are obtained. The data show that the maximum measured frost-heave force is much smaller than the prediction. It is due to the countermeasure of pressure release hole, which reduced the frost-heave pressure on segment.