Research conclusions: ( 1) The origin of the water － bearing formation in the Taigu Tunnel was complex． The water －bearing formation had a certain compaction property，but it was poor in cementation as the lower Pleistocene stratum，with big influence of rich underground on the construction of the tunnel． ( 2) As the geological condition of the tunnel was complicated with much underground water，the construction plan would be adjusted according to the situation of the surrounding rocks and the volume of water bursting so as to ensure the construction safety． ( 3) The more attention should be paid to the construction in the similar formations in future for the construction safety．