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Experimental Study on Steel Pipe Pile Reinforcement of the Soft Foundations of Saturated Loess Tunnels
(1 College of Civil Engineering, Lanzhou Jiaotong University, Lanzhou 730070; 2 Key Laboratory of Road & Bridge and Underground Engineering of Gansu Province, Lanzhou 730070; 3 China Railway First Survey and Design Institute Group Ltd., Xi′an 710043)
Abstract As for the reinforcement measures for the soft foundation of saturated loess in the Wangjiagou tunnel on
the Baoji- Lanzhou passenger dedicated line, laboratory tests containing 4 kinds of loess water content and field tests for reinforcing the soft foundation were conducted. The settlement characteristics of the model pile and the field single pile and composite foundation were analyzed, respectively, and the strain characteristics of the modelpile were studied for the high water content of the loess. Conclusions could be summarized as follows: Q-S curves of the model piles change from a smooth shape to an abrupt shape with the increase of the moisture content in the soil around the pile, while the settlement rate of the pile becomes higher, and the ultimate side friction of the pile decreases, as the law of the power function. For the high water content of loess, the strains along the steel pipe pile distribute in a“B”shape with the loading time. Based on the results of field tests, it is suggested that the steel pipe pile and composite foundation should be used for reinforcing the soft foundation of the Wangjiagou saturated loess tunnel, with steel pipe piles distributed as an equilateral triangle. The proposed design parameters for the piles are given according to the specifications. The experiment results provide a reference for laboratory tests and field tests of soft foundations reinforced by steel pipe piles.
Abstract：
As for the reinforcement measures for the soft foundation of saturated loess in the Wangjiagou tunnel on
the Baoji- Lanzhou passenger dedicated line, laboratory tests containing 4 kinds of loess water content and field tests for reinforcing the soft foundation were conducted. The settlement characteristics of the model pile and the field single pile and composite foundation were analyzed, respectively, and the strain characteristics of the modelpile were studied for the high water content of the loess. Conclusions could be summarized as follows: Q-S curves of the model piles change from a smooth shape to an abrupt shape with the increase of the moisture content in the soil around the pile, while the settlement rate of the pile becomes higher, and the ultimate side friction of the pile decreases, as the law of the power function. For the high water content of loess, the strains along the steel pipe pile distribute in a“B”shape with the loading time. Based on the results of field tests, it is suggested that the steel pipe pile and composite foundation should be used for reinforcing the soft foundation of the Wangjiagou saturated loess tunnel, with steel pipe piles distributed as an equilateral triangle. The proposed design parameters for the piles are given according to the specifications. The experiment results provide a reference for laboratory tests and field tests of soft foundations reinforced by steel pipe piles.
.Experimental Study on Steel Pipe Pile Reinforcement of the Soft Foundations of Saturated Loess Tunnels[J] MODERN TUNNELLING TECHNOLOGY, 2017,V54(3): 73-81
2017, Vol. 54 