基于图解法的嵌岩抗拔桩极限承载力分析

基于嵌岩抗拔桩现场试验结果,采用图解法对实测荷载-位移曲线进行极限承载力判定取值,并将判定值与实测值进行比较。结果表明,初始直线斜率法受到3.8 mm位移增量的限制,对嵌岩抗拔桩极限承载力取值为实测值的42.0%～102.4%,平均66.0%,偏于保守;双直线交点法的取值为实测值的85.2%～98.5%,平均94.8%,较为合适;L_1-L_2法的L_1取值仅为实测值的15.5%～64.1%,平均29.7%;L_2取值方法是现行桩基规范中确定极限承载力的判据之一。当基础变形有严格特殊的要求时,在试桩荷载-位移曲线特征明显的情况下,L_1-L_2法可以用于试桩承载变形分析,但并不适合用于确定极限承载力。

Analysis of ultimate bearing capacity of rock-socketed uplift piles based on graphical methods

Based on the field test results of rock socketed uplift piles, the ultimate uplift capacity is determined by graphical methods that applied on load-displacement curve, and the determined value is compared with the test value. The results show that the initial straight line gradient method is limited by the displacement increment of 3.8mm, and the value of ultimate bearing capacity of rock socketed uplift pile is 42.0% ~ 102.4% of the test value, with an average of 66.0%, which is conservative; The value of double straight line intersection method is 85.2% ~ 98.5%, with an average of 94.8%, which is more appropriate; The L1 value of L1-L2 method is only 15.5% ~ 64.1%, with an average of 29.7%; The L2 value method is one of the criteria for determining the ultimate bearing capacity in the current pile foundation code. When the foundation deformation has strict and special requirements, L1-L2 method can be used to analyze the bearing deformation of test piles, but it is not suitable for determining the ultimate bearing capacity.