The Seismic Responses Of Fissures And Lining Structure Under Earthquake Motion

Considering the underground fissures of Xi’an and construction of metro in this city,research techniques such as the large scale of shaking table experiment has been conducted tosimulate the underground fissures under earthquake motions, which is used to research theseismic response of those fissures under Xi’an. Finite element method was also used toimitate seismic response of metro tunnel which is across underground fissures underearthquake force. the shaking table test and FEM results are showed below:1. Triggered by El Centro wave, the amplification coefficient reduced as the excitingpeak acceleration of El Centro wave increased, which is varied between2.13and1.00.Besides, the amplification coefficient changed dramatically when exciting peak accelerationof the wave reach300gal; the amplification coefficient of Taft wave and Lanzhou wavelowered by the rising of exciting peak acceleration, which ranged at3.21-1.33and1.6-0.23respectively. While the amplification coefficient of Lanzhou wave showed totally differencefrom other two waves, the amplification coefficient lowered than1after exciting peakacceleration pass300gal.2. Triggered by El Centro wave, the responded peak acceleration of both sides of themain fissure and sub-fissure grew up with the increasing of exciting peak acceleration. Thehangingwall/footwall coefficients of main fissure are over1in all situations at the bottom ofthe model; while the coefficient kept around1at middle and less than1at the top of themodel. The hangingwall/footwall coefficients of sub-fissure are bigger than1at the bottomand middle of the model, which decreased less than1at the top of the model.3. Triggered by El Centro wave, the hangingwall/footwall coefficients of main fissureenlarged with the increment of the depth of the soil; which is also fulfilled in sub-fissure,however, the values of this coefficient fluctuated when the exciting peak acceleration are200gal and800gal.4. The results of FEM simulation showed the responded acceleration at the top oftunnelling shield is larger than exciting acceleration at both hangingwall and footwall parts,while the responded velocity and displacement showed little difference at both sides. Theother parts of the tunnelling shield responded less significant as the top of tunnel and there islittle response difference between the hangingwall part and footwall part.