考虑土体参数空间变异性的浅基础扩展式可靠度设计

Expanded reliability-based design of shallow foundations in spatially variable soils

岩土体是天然材料,其性质存在固有的空间变异性,这是岩土体参数不确定性的重要来源.提出了考虑土体参数空间变异性的浅基础扩展式可靠度设计方法,探讨了不同空间变异性表征模型对浅基础可靠度设计的影响规律.结果表明：土体参数空间变异性对浅基础可靠度设计结果影响显著;方差折减方法可视作简化的随机场模拟方法,在给定基础承载力影响区条件下能够合理地表征土体参数的空间变异性;方差折减法中不同的方差折减函数计算形式对可靠度设计结果有明显影响,采用简化计算形式得到的设计结果偏保守.

Geotechnical materials are nature materials,whose properties are inherently variable from one location to another.Such variability is one of the main sources of uncertainties in geotechnical properties.This paper proposes an expanded reliability-based design（RBDE）method for shallow foundations in spatially variable soils.Effects of different spatial variability modeling methods（including random field modeling（RFM）and equivalent variance technique（EVT））on reliability-based design（RBD）results of shallow foundations are explored.The results show that the inherent spatial variability of geotechnical parameters has significant influences on RBD results of shallow foundations and EVT can be viewed as a simplified form of RFM,which properly characterizes spatial variability of geotechnical parameters for a given influence zone for the bearing capacity of shallow functions.The variance reduction function adopted in EVT may have significant effects on RBD results of shallow foundations.Using the simplified form of variance reduction function may lead to relatively conservative designs in this study.