Abstract:

The causes of piping and sand boiling of shield launching are analyzed; a model that groundwater permeates from reinforced soil pervious underlying layer to wall is established. Using semi-confined aquifer seepage theory, an example is given to demonstrate that, supposing that the reinforced soil is impervious, the accident that water and sand inflows from tunnel portal is influenced by range of soil reinforcement, groundwater level and the gap of wall; the cost and safety of engineering have the positive correlation with the length of reinforced soil; the depth of reinforcement isn’t so deep but reasonable; the gap of wall also plays a key controlling role to shield launching’s safety. The factors are mutual constraint; construction parameters are influenced by security, economy and time limit for a project.

Key words: shield launching, seepage, soil reinforcement, accident mechanism