Abstract:

The fluctuation rules of the ground water levels outside the foundation pit during water filling period and water discharging period are summarized on basis of site measurements, with the immersed tunnel from Shengwudao Island to University Town as an example. During the water filling period, the soil outside the foundation pit is in a water-absorbing process; during the water discharging and secondary excavation period, the soil outside the foundation pit is in a water-releasing process; the water absorbing rate is higher than the water releasing rate; due to the water bearing capacity of the side slope, the difference between the water level inside the foundation pit and that outside the foundation pit at local positions reaches 4m, which severely jeopardizes the stability of the side slope. Due to the treatment of the slope foot in advance, the water seepage inside the side slope has not jeopardized the stability of the side slope. In the whole course, the side slope has good stability.

Key words: foundation pit of axial dry dock, immersed tunnel, load increasing by filling water, load decreasing by discharging water, fluctuation rule