Experimental study of a segmented metro tunnel in a ground fissure area

This paper studies the seismic response of a segmented metro tunnel with flexible joints passing through active ground fissures in Xi'an by shaking table model test. A coupling dynamic ground motion was generated in the test model. The tunnel acceleration, earth pressure and tunnel structure strain were monitored and compared. It was observed that each part of the tunnel has an independent movement with flexible joints. The tunnel located in the hanging wall has 3.17 times peak acceleration than that in the foot wall. Higher magnitudes of earth pressures were recorded close to the areas of the ground fissures. The earth pressure in the hanging wall was greater than that in the foot wall. The coupling loads increase the earth pressure. The strain in the middle of the tunnel arch was the largest. The strain at the bottom of the floor was the secondary. The one on the top of the arch was the smallest. The strain increased less in each section because the tunnel is divided into four parts by flexible joints, and no sharp strain increase close to the ground fissure was observed. The results indicate that the flexible joints can decrease the stress concentration. The tunnel with flexible joints can adjust to large deformations in the ground fissure areas.