Nonlinear seismic response of the bridge pile foundation with elevated and embedded caps in frozen soils

Frost jacking of piles in seasonally and perennially frozen ground

Effect of frost heave deformation of bridge foundation on operation safety of high-speed railway

A new approach for improving lateral performance of pile foundations in seasonally frozen regions

Analysis and research on the difference of design codes for vertical bearing capacity of pile foundation in cold regions

Influence of seasonal freezing-thawing soils on seismic performance of high-rise cap pile foundation in permafrost regions

Pile foundation with elevated cap is always applied for railway bridges in permafrost region to minimize the thermal disturbance to vulnerable permafrost. Permafrost can influence the failure characteristics of the pile foundation under earthquakes and complicate the seismic performance evaluation of railway bridges with pile foundations in seismically active zones. Quasi-static tests of reduced scale models were carried out to investigate failure characteristics and hysteretic behaviors of the pile foundation with elevated cap in permafrost. Test results showed that the existence of permafrost can increase the stiffness of the foundation soil and then inhibit crack propagation of the unfrozen topsoil around the bridge pile foundation. Quite differently from the pile foundation in unfrozen soils, severer damages occurred at the pile foundation in soils with permafrost. Thus, the topsoil crack will be mitigated while the pile failure will be aggravated if strong earthquake occurs in permafrost regions for railway bridge pile foundation with elevated cap. Otherwise, the permafrost significantly influenced the loading bearing capacity and deformation features of the pile-soil interaction (PSI) system under seismic loads. The PSI system with permafrost has better energy dissipation than that with unfrozen soils due to the severe damage of the pile foundation. A simplified formula was developed to estimate the equivalent stiffness of the PSI system. It is indicated that the stiffness of the PSI system with permafrost degraded more severely than that with unfrozen soils. Therefore, permafrost effect cannot be neglected in seismic design of railway bridge pile foundations with elevated cap.

Effect of Permafrost on Seismic Performance of Railway Bridge Pile Foundation with Elevated Cap

Effect of the seasonal freeze–thaw cycle of the active layer on the seismic response of the free field in the permafrost region

Frozen soils are widely distributed in the seismically active regions of northwest China. Under the background of global warming, the study of the dynamic characteristics of frozen soil is very significant for the sustainable development of engineering in cold regions. In this study, the silty clay in the Lanzhou area of northwest China is selected to investigate the dynamic characteristics and its influence factors by dynamic triaxial tests. Various influence factors were considered, including confining pressure, soil temperature, soil water content and loading frequency. The dynamic elastic modulus ratio and reference dynamic strain amplitude increase as confining pressure and soil temperature decrease, and they also increase as soil water content and loading frequency increase. With an increase in confining pressure, soil water content, loading frequency, and a decrease in soil temperature, the damping ratio decreases but the maximum dynamic elastic modulus increases. With an increase in dynamic strain amplitude, the dynamic elastic modulus ratio has a decreasing trend, while the damping ratio has an increasing trend. It was found that the dynamic behaviors are most sensitive to the soil temperature. In addition, the comprehensive influence effect of soil water content, confining pressure, soil temperature, and loading frequency on the maximum dynamic elastic modulus, maximum damping ratio, and reference dynamic strain amplitude of frozen silty clay are analyzed, and the quantitative relationships between them are established. The results can provide evidence for seismic design and safe operation and maintenance of infrastructure in cold regions.

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Jiada Guan

Papers

Influence of seasonal freezing-thawing soils on seismic performance of high-rise cap pile foundation in permafrost regions

Nonlinear seismic response of the bridge pile foundation with elevated and embedded caps in frozen soils

Effect of Permafrost on Seismic Performance of Railway Bridge Pile Foundation with Elevated Cap

Effect of the seasonal freeze–thaw cycle of the active layer on the seismic response of the free field in the permafrost region

Experimental Study on the Dynamic Characteristics of Frozen Silty Clay and Its Influencing Factors