Analysis On Dynamic Response And Long-term Settlement Of The Ground Fissure Sites By Vibration Of The Subway

In resent years, China’s subway transport system has gone the rapid development.However, the subway long-term operation of soil and ground deformation has becomeincreasingly prominent. Therefore, it is necessary to study the ground fissures metro venuesdynamic response and long-term settlement caused by vibration. This paper adopted theANSYS finite element analysis software to build a two-dimensional finite element modelcombined with the results of previous tests so as to obtain the analyze cracks dynamicresponse and long-term settlement rule under the subway vibration loads. the mainconclusions are as follows:Ground fissures on both sides of the vertical displacement of soil changes with a certainperiodicity, commonly the dominant frequency of vibration displacement of about0.89Hzthat belongs to low-frequency vibration. This indicated soil foundation displacement isdominated by low-frequency vibration loads. Under the traffic vibration loadings, the platevertical displacement and vertical acceleration of ground fissures are greater than those of thelower plate. Also with the increase of the horizontal distance of the ground cracks, thevertical displacement and acceleration of the disk decreases, while the vertical displacementand acceleration of lower plate increases, vertical displacement, acceleration amplitudedifference and the peak difference between upper and lower plate decreases. When the crackreached50m (about2.5times the distance to the crack depth), the impact of train vibrationloading on the ground fissures was not obvious.With increasingly horizontal distance, vertical stress of upper plate increases while thoseof lower plat e goes down. When the crack distance reaches30m (approximately1.5times the depth of ground fissures), the peak value and amplitude of vertical stress varieslittle along with horizontal distance. The presence of soil vertical stress attenuated with theincreasingly depth and attenuated fast first and slow after with vertical dynamic stressamplitude at1.2Kpa, about the dynamic stress amplitude surface1/16.With increased ground cracks horizontal distance, the surface soil subsidence decreaseswhile the lower plate surface soil subsidence increases and the upper and lower plate differential settlement showed a decreasing trend. Particularly when the crack is greater than50m (approximately to crack depth of2.5times) the settling differences between upper andlower plate is very small. In the early subway operators, vertical settlement of soil faster andduring the first0.5years (train9000times) the soil deformation is substantially more than50%of the final deformation; in the first10years (train180000times), the differencebetween the upper and lower plate became stable to12mm.