对现行规范以液性指数I_L确定极限端阻力标准值q_(pk)的质疑

Inquiry on determination of soil standard value of ultimate bearing capacity of end of piles by liquid index in technical code for building pile foundations

通过对某工程单桩极限承载力标准值不满足设计要求的原因进行深入分析,指出持力层土所含的高岭土浸水软化,当受到荷载作用时,在桩端周围形成塑性剪切滑移面,产生局部剪切破坏,大大降低了桩端持力层土的极限端阻力标准值qpk,从而指出现行《建筑桩基技术规范》(JGJ 94-94)[1]仅以液性指数IL,确定极限端阻力标准值qpk值存在不足,宜综合压缩模量Es和孔隙比e而定。

For an actual project, the reason of standard ultimate bearing capacity of a single pile less than that of designing value is analyzed. It is suggested that when kaolin included in the soil at the end of piles is softened by water, a plastic shear-sliding plane will be generated. Then the soil will be in shear failure mode under static loading which significantly decreases the soil standard ultimate bearing capacity. For this case, it is not reasonable to determine the soil standard ultimate bearing capacity only by liquid index based on technical code for building pile foundations, the compression modulus and ratio of pore should be added for consideration.