关键词: 地铁车站, 试验桩, 单桩承载力试验, 桩侧摩阻力, 桩端阻力, 单桩极限承载力, 单桩承载力特征值

Abstract:

The static loading test is used to test the pile of Renminguangchang Station of Shijiazhuang Metro. The test of bearing capacity of the pile, determination of the ultimate side friction resistances of every soil layer and pile end resistance and the ratios of pile side friction resistance and pile end resistance to the ultimate bearing capacity and characteristic value of bearing capacity of single pile are required in design. The doublesleeve is used to eliminate the pile side friction resistance of the invalid soil layer; the distribution and variation of the axial force, side friction resistance and end resistance of pile body are calculated by the elastomechanical formula, which provides reference for project design. The results show that: 1) The doublesleeve can directly eliminate the friction resistance of the invalid soil layer, which can actually reflect the bearing capacity, friction resistance, end resistance and settlement value of the test pile. 2) When the ultimate bearing capacity is reached, the total side resistance of the pile is about 65%-66%, and the total end resistance of the pile is about 34%-35%; when the characteristic value of bearing capacity is reached, the total side resistance of the pile is about 76%-80%, and the total end resistance of the pile is about 20%-24%; the bearing capacity of the test pile presents end bearing friction. 3) The side friction resistance of the pile in local range presents softening characteristic of stress and displacement. 4) The bearing layer of pile end is mainly composed of cobble layer, which accounts for about 30% of the total bearing capacity.

Key words: metro station, test pile, bearing capacity test of single pile, pile side friction resistance, pile end resistance, ultimate bearing capacity of single pile, characteristic value of bearing capacity of single pile