（中煤科工集团重庆设计研究院有限公司， 重庆 400016）

［摘要］针对山区极软岩上覆原生土很薄且新近填土较厚时，机械成孔桩即使按最大嵌岩深径比计算单桩的竖向极限承载力仍无法满足上部荷载要求的情况，利用现行规范推导出中风化极软岩桩的极限端阻力标准值和极限侧阻力标准值取值范围，并结合岩基载荷试验数据对取值范围进行了修正。提出了嵌岩桩按经验参数法计算单桩竖向极限承载力的思路，并结合工程实例中的桩载荷试验数据验证了此计算思路及中风化极软岩桩的极限端阻力标准值和极限侧阻力标准值取值范围的安全合理性。研究结果表明：中风化极软岩桩的极限端阻力标准值取值范围为1 500～3 800kPa，极限侧阻力标准值取值范围为140～280kPa，按新计算思路获得的单桩竖向承载力特征值比按嵌岩桩计算方法获得的数值可最大提高约12%，且计算深度大于8倍的嵌岩深径比。

［关键词］桩基; 极限端阻力; 极限侧阻力; 极软岩

中图分类号：TU473        文献标识码：A        文章编号：1002-848X(2014)08-0021-04

Research on ultimate tip resistance and ultimate shaft resistance of piles in middle weathered extremely soft rock

Zhan Kaiyu

 (Chongqing Design and Research Institute Co., Ltd., China Coal Technology and Engineering Group, Chongqing 400016, China)

Abstract: According to machine drilling hole can not meeting the requirements of upper loads calculating by largest embedded depth-diameter ratio under the conditions of thin primary soil and thick recent filling overburden extremely soft rock in mountain area, the standard value range of ultimate tip resistance and shaft resistance of piles in middle weathered extremely soft rock was derived by utilization of current code and was revised by utilization of rock foundation loading test data. A modified method of calculating single pile vertical ultimate bearing capacity by empirical formula for rock-socketed pile was put forward, and the modified method and the standard value range of ultimate tip resistance and shaft resistance of piles in middle weathered extremely soft rock were validated by pile loading tests in a project. The results show that the standard value range of ultimate tip resistance of piles in middle weathered extremely soft rock is 1 500～3 800kPa, the standard value range of ultimate tip resistance is 140～280kPa. The characteristic value of vertical bearing capacity of single pile can increase 12% and the calculation depth can be more than 8 to embedded depth-diameter ratio by the modified method.

Keywords: pile foundation; tip resistance; shaft resistance; extremely soft rock

作者简介：湛铠瑜，硕士，工程师，Email: zhankaiyu@163.com。

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