| Summary: | 碩士 === 國立臺灣大學 === 土木工程學研究所 === 105 === Ground deformation induced by faulting is one of the causes for engineering structural damages in addition to strong ground motion Using the Sanchiao Fault in Taipei as an example, it is a normal fault located on the west side of Taipei Basin. There are many important structures above Sanchaio Fault, the Taiwan High Speed Rail (THSR) crossing Sanchiao Fault by bridges is an example. Once Faulting, the overburden soil will cause ground deformation and make structures damaged. The usage of pile foundations is very common as they provide the necessary bearing capacity. The piles may suffer rotation, inclination, displacement due to faulting and make the bridges collapse. Therefore, the study in The Deformation of Overburden Soil and Interaction with Pile Foundations of Bridges Inducd by Normal Faulting is a very important issue.
In this study, a small-scale sandbox model in sandy soil in relative density 55%, friction angle 35˚ is used to evaluate development of triangular shear zone, the ground deformation and the rotation, inclination and displacement of piles in 1g surroundings subjected to faulting. The experiment results are used to validate the numerical simulations.
The results in experiments indicates that the shear zone developed seven to nine in hanging wall and footwall and the wider primary deformation zone in lower fault tip angle (30˚) while the shear zone developed three in hanging wall for one and footwall for two and the narrower primary deformation zone in higher fault tip angle (60˚). However, all of them form graben subjected to faulting. We can understand the rotation, inclination, displacements in the all experiments. The pile in different locations will cause different soil deformation. Take the high fault tip angle (60 ˚) as am example, the pile above fault tip or in the footwall 10 cm, the width primary deformation zone in hanging wall will occur. The pile in the hanging wall 5 cm, the width primary deformation zone in foot wall will occur. The behaviors of pile doesn’t wok up when the pile in the foot wall for more distance.
The numerical program PFC 3D be used to validated by small-scale sandbox experiments in the first. Then, bridges simulations, different soil simulations be simulated. The end, study real case “THSR crossing Sanchiao Fault by bridges” in 1/20 scale simulation.
The simulations indicate, the PFC 3D have effective to calibrate from sandbox experiments and it can simulate the piles and bridges subjected to faulting. There have practicability to simulate faults and structures from PFC 3D. Through the change of parameters in program, it can simulate different overburden soil such as sandy soil, clay, complex soil. The sandy soil has the widest primary deformation zone. The clay has tension crack on the surface. The surface appearance is controlled by upper material from complex soil. According to the paramters in this study, the “THSR crossing Sanchiao Fault by bridges” simulations, it can understand that if the locations of Sanchiao Fault crossing between 018PR14 and 018PR13A, it has the possibility collapse of superstructures. Since the accurate location of Sanchiao Fault is uncertain, the safety of superstructures of bridges needed to be considered more careful.
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