关键词: 黄土斜坡桩基, 竖向承载特性, 现场试验, 区域性, 承载力的折减

Abstract: Combined with the pile foundation engineering constructed in loess slope for supporting super bridge, field experiments on two neighboring piles at the same slope region are conducted to investigate transmitted characteristics as well as distribution feature of axial force, skin friction and lateral earth pressure of both upslope side and downslope side under different vertical load cases. The test results show that load transmitting of pile foundation can be obviously classified into 3 regions. The first region covers from pile head to about the depth of three times pile diameter; within this region, the axial force developed in pile upslope side is less than corresponding position at downslope side; moreover, its decrease extent with pile depth and work efficiency of skin friction are greater than pile downslope side. The second region is within about pile depth of three times to ten times pile diameter, which shows a less axial force decrease extent with pile depth in upslope side and higher work efficiency of skin friction along downslope side at the same elevation. The third region starts from the pile depth of about ten times pile diameter and ends with pile tip. For pile body in this region, the difference of axial force and skin friction for two sides at the same elevation are insignificant; and the load from super region could be even and well-distributed transmitted downwards. For the special issue of uneven earth pressure of pile foundation installed in loess slope, certain reduction in some degree for vertical bearing capacity of pile design is conducted; and some necessary revision of the calculation formula is made. The acquired study results can provide a reference for other similar pile foundation.

Key words: pile foundation in loess slope, vertical bearing capacity, field test, regionalism, reduction of bearing capacity