基坑支护中土钉内力计算方法对比分析

大量足尺模型试验和实地监测结果表明,土钉支护中土钉内力具有开挖效应,土钉最大拉力出现在基坑中部,上部和下部内力均较小.规范《建筑基坑支护技术规程》（JGJ 120-99）及《基坑土钉技术规程》 （CECS 96∶97）的设计计算理论均不能准确反映土钉墙现场原型观测中实际土钉力,以上问题给合理确定土钉长度带来困难,使计算土钉力及确定长度更多依靠经验,造成土钉力设计偏于不安全或偏于保守.通过分析现行规程计算土钉力与实测土钉力的不一致性,指出现行规程计算方法存在的缺陷,进而分析研究土方开挖对土钉力的影响,讨论了基于增量法的土钉内力简化计算方法.

Discussions of Soil Nail Stress Calculation Methods in Soil Nail Wall

A large number of full-scale model tests and field monitoring results show that soil nail internal forces have excavation effect. The maximum tension of soil nail appears in the middle of the foundation pit, the upper and lower internal forces are smaller. But the design and calculation theory of norms ＂Technical specification for retaining and protection of building foundation excavation＂ （JGJ 120--99） and ＂Specification for soil nailing in foundation excavation＂ all cannot accurately reflect the actual soil nail internal force we prototype observed at the scene. The above issues bring difficulty to reason- ably determine the length of soil nail, make the calculation of internal forces and the length of soil nail rely more on experience, and lead to the design of soil nail forces unsafe or conservative. Here we analyzed the soil nail force calculated by current regulations is not consistent with the measured soil nail force, pointed out the defects existing in the current regulations calculation method, analyzed the effect of earthwork excavation of soil nail force, and discussed a simplified soil nail internal force calculation method based on incremental method.