One of the key problems in the construction of the electrification reconstruction project of Gela section of Qinghai-Xizang Railway is to ensure the frost jacking stability of the pile foundation of the overhead contact system mast(OCSM).In order to study the anti-frost jacking performance of piles with different sections(equal-section circular pile(Z1),straight-cone cylindrical pile(Z2),and curved-cone cylindrical pile(Z3)),the indoor model tests with three freeze-thaw cycles were carried out by using the subgrade filling materials of Qinghai-Xizang Railway as the test soil sample.The distribution laws of ground temperature,pile-top displacement,and pile body stress of the OCSM pile foundations under the influence of freezing and thawing were obtained.The test results show that the freezing(thawing)of the subgrade is two-dimensional,and the depth of freezing near the OCSM pile foundations is about 30 cm.The vertical frost-heave displacement at the subgrade shoulder is 4.30 mm,and the vertical frost jacking displacement of Z1 is 0.26 mm.In addition,the vertical frost jacking displacement of Z2 and Z3 is only 46％and 58％of Z1,respectively.The top of the three piles has a horizontal displacement of about 0.1 mm.During the freezing process,the pile is under tension as a whole,and the axial force is greatest near the depth of freezing.The maximum value of tangential frost-heave stress occurs near the ground surface.The total tangential frost-heave force of the curved-cone cylindrical pile is the smallest,with the best anti-frost jacking effect.
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