Research on Standard Value of Ultimate Shaft Resistance for Fragile Intermediary Weathered Bedrock
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摘要: 针对将桩基置于较破碎中等风化岩体时需要提供其极限端阻力标准值而桩基规范中无中等风化岩体极限端阻力标准值的取值建议,结合重庆地标和桩基规范通过理论推导获得了中等风化岩体的极限端阻力标准值计算公式;通过理论计算结合桩基规范提出了较破碎中等风化岩体极限端阻力标准值的取值范围;结合工程实际分析了较破碎中等风化岩体极限端阻力标准值取值范围的合理性。研究结果表明,采用人工挖孔桩时,较破碎中等风化软质岩的取值范围为1 400~5 400 kPa,较破碎中等风化硬质岩的取值范围为5 400~21 700 kPa;采用机械成孔桩时,较破碎中等风化软质岩的取值范围为1 200~4 600 kPa,较破碎中等风化硬质岩的取值范围为4 600~18 500 kPa;较破碎中等风化极软岩与强风化软质岩的工程性质相似,较破碎中等风化软岩好于强风化硬质岩的工程性质但不如密实状态卵(碎)石的工程性质,较破碎中等风化较软岩与密实状态卵(碎)石的工程性质相似,较破碎中等风化较硬岩好于密实状态卵(碎)石的工程性质。Abstract: This paper presents a calculation formula and puts forward the value range of standard value of shaft resistance for fragile intermediary weathered bedrock because it needs to be provided when the pile was placed at the fragile intermediary weathered bedrock, but there was no value recommended of it in technical code of building pile foundations.And the value range of standard value of shaft resistance for fragile intermediary weathered bedrock was validated by engineering practice.The results show that the value range of standard value of shaft resistance was 1 400~5 400 kPa for soft rock and it was 5 400~21 700 kPa for hard rock under dry drilling, and it was 1 200~4 600 kPa for soft rock and it was 4 600~18 500 kPa for hard rock under mechanical hole building.And the engineering property of fragile intermediary weathered extremely soft rock is similar to strong weathered soft rock, the fragile intermediary weathered soft rock is inferior to compacting gravel, the fragile intermediary weathered relatively soft rock is similar to compacting gravel, the fragile intermediary weathered relatively hard rock is better than compacting gravel.
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