Shaking Table Test On Dynamic Response of Bridge Pile Foundation Near Fault Under Strong Earthquake

Taking Puqian bridge as the prototype, a 1:30-scale pile-soil-fault interaction model was established. Through the shaking table test, the difference of dynamic response of pile foundation on both sides of fault under 0.15~0.60g ground motion intensity was studied. The pile acceleration, pile top relative displacement, and pile bending moment on both sides of the fault are compared respectively. Research results showed that under the action of a strong earthquake, the pile foundation on the hanging wall was greatly affected by ground motion, and “the hanging wall effect” was significant. As the ground motion intensity increased, the “hanging wall effect” of the pile foundation was more obvious. Combined with the fundamental frequency response and the test phenomenon, when ground motions intensity was strong, cracks appeared near the joint of pile top and platform, soil interface, and bedrock surface. When building a bridge pile foundation near the fault, the seismic design of the pile foundation on the hanging wall of the fault is mainly considered.

Research on the Influence Mechanism of the High-Steep Slope on the Deformation Characteristics of Bridge Substructure

With the development of the Chinese railway, the high-steep slope is irreversible to be faced; especially under severe conditions such as heavy rainfall and earthquake, this kind of slope is prone to geological disasters, which seriously affects the safety and stability of the bridge substructure. Aiming to this, long-term monitorization and numerical analysis were carried out in this research, and the influence mechanism of the high-steep slopes on the stress and deformation characteristics of the bridge structure was studied. The research results show that under the effect of rainfall and earthquake, the original stress balance in the high-steep slope is broken, and the possibility of landslide thrust increases; under the comprehensive impact of residual landslide thrust, traction force at slope foot, vertical gravity of bridge slab and vehicle, and the bridge cap will deform. Besides, the deformation of the bridge pier exceeds the allowable lateral displacement of the top of the bridge pier, reaching 111.7%∼112.4% of the limit, which seriously affects the stability of the bridge structure and the safety of the railway service. Therefore, by increasing the support strength of the slope foot and the diameter of the bridge pile foundation, the traction force of the slope foot can be reduced, and the sliding resistance of the bridge pile foundation can be improved so as the safety of the bridge structure can be promoted.

Effects of Landslides on the Displacement of a Bridge Pile Group Located on a High and Steep Slope

Engineering practice shows that the deformation of the slide-resistant pile may be transferred to the adjacent bridge foundation on an inclined slope, which can compromise the safety of the entire bridge. However, this phenomenon has rarely been considered in the past. To reveal the deformation transfer mechanism between the slide-resistant pile and the adjacent structures, a full-scale field test was performed on a high and steep slope located in a section of a certain railway. A numerical analysis model was constructed to simulate the field test and validate its parameters. Moreover, parametric analysis was also conducted to examine the influence of the pile length, pile diameter, and arrangement of the pile foundation. The results show that the bridge pile foundation is simultaneously affected by the “load transfer effect” caused by the slide-resistant pile and “traction effect” of the sliding slope. With the distance between the pile foundation and the slide-resistant pile increasing, the dominant factor affecting the deformation mode of the pile body is switched from the “load transfer effect” to the “traction effect.” Furthermore, a critical embedment depth exists for the bridge pile foundation built on a high and steep slope, which varies at different locations along the inclined stratum. In addition, using a pile arrangement with a larger pile diameter and lower number of piles is more beneficial for controlling the horizontal displacement of the bridge foundation. The results of the research provide a reference for the safety control of the engineering on the high and steep slope.