Abstract
To study the settlement and deformation characteristics of a long-short pile composite foundation and its influencing factors, the indoor centrifuge model test and numerical simulations were performed under the actual working conditions to treat the saline soft soil foundation in the Soltan salt lake area of Iran. Firstly, the settlement of a long-short pile composite foundation and the law of pile-soil stress ratio development with time were studied using a centrifuge model test. In addition, FLAC3D was used to simulate the test conditions, and it has been observed that the numerical and experimental results were in good agreement. Based on the numerical model, the effects of the replacement rate of long and short piles, cushion modulus, and pile length on the settlement of the composite foundation and the stress ratio of long and short piles were analyzed. The results show that the long-short pile composite foundation can effectively control settlement. Compared to the untreated foundation, the total settlement of a long-short pile composite foundation was reduced by 67%, and the postconstruction settlement was reduced by 47.7%. Compared to the final settlement of the composite foundation obtained using the centrifuge model test, the error range of the numerical simulation results was between 2.4% and 8%. The influence of pile spacing on the settlement and stress characteristics of a long-short pile composite foundation is greater than that attributable to the arrangement of the piles. Under this geological condition, it is reasonable to choose a pile spacing of 4d∼5d. When the long pile reaches the bearing stratum, the length of the short pile should not exceed 0.6 times the length of the long pile. The setting cushion not only reduces uneven settlement of the composite foundation but also improves the joint bearing capacity of the pile and the soil between the piles.
Highlights
Introduction eDY (Tehran to Isfahan) high-speed railway in Iran starts in Tehran and ends in Isfahan and has a total length of approximately 405 km
Deep soft soil containing salt is widely distributed in the Soltan salt lake area where the highspeed railway passes. e geological location of the project is shown in Figure 1. e foundation in the salt lake area has the characteristics of high groundwater level, large salt content, and low bearing capacity. e variation of the environmental temperature causes the migration, accumulation, crystallization, and dissolution of water and salt in the soil, resulting in salt expansion, frost heave, and an increased risk of collapse of highway and railway foundations [1]
To study the deformation characteristics of a long-short pile composite foundation in saline soft soil region and to analyze its in uencing factors, indoor centrifuge model tests were conducted as part of this investigation. e settlement and the variation of the pile-soil stress ratio for a long-short pile composite foundation were analyzed
Summary
Introduction eDY (Tehran to Isfahan) high-speed railway in Iran starts in Tehran and ends in Isfahan and has a total length of approximately 405 km. E variation of the environmental temperature causes the migration, accumulation, crystallization, and dissolution of water and salt in the soil, resulting in salt expansion, frost heave, and an increased risk of collapse of highway and railway foundations [1]. To avoid these problems, it is necessary to reinforce the foundation using appropriate ground treatment. The pile technology can be used to reinforce the soft soil foundation to form a composite foundation that bears the load through the pile with high rigidity, in addition to the surrounding soil. Composite foundation technology has been widely used in soft soil regions in China, it is being used for the first time in Iran
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