（1 清华大学土木工程系，北京，100084；2天津农学院水利工程系 300384；3 天津大学水利工程系 300072）

［提要］通过自编的Mindlin群桩沉降计算软件，对规范中新引入的群桩沉降计算方法——Mindlin方法中两个重要计算参数α，β的影响进行了研究分析。α对桩端附近上下各约8d范围内应力相对集中区域的应力场影响较为明显，从而影响沉降计算结果，因此应根据工程经验或实测资料合理确定α值；β取值大小决定了桩侧摩阻力的分布形式，其影响主要体现在桩身范围内，而对桩端以下应力场的影响较小，因而规范规定对于一般的摩擦型群桩基础，采用此法计算桩基沉降（只计算桩端以下地基土的压缩量）时可取β＝0的做法是可行的。

［关键词］桩基础；沉降；应力集中；附加应力；桩侧阻力

Effects of Parameters αand β in Calculating Settlement of Grouped Piles Foundation with Mindlin Method of Code/Wang Xiangyu1, Li Shaofei2，3(1 Dept. of Civil Engineering, Tsinghua University, Beijing 100084, China; 2 Dept. of Hydraulic Engineering, Tianjin Agriculture College, Tianjin 300384, China；3 Dept. of Hydraulic Engineering, Tianjin University, Tianjin 300072, China)

Abstract:Using the pile foundation settlement calculating software, the effects of the two important parameters αandβin Mindlin method, which is a recommended method in the code for calculating the settlement of pile foundation,are studied. The parameter α has great influence on stresses of the points that lie in the region ranging from about 8d distance above to 8d distance below the piles bottom surface. Consequently, it can obviously influence the settlement calculation. Therefore, it should be reasonably determined according to engineering experiences or practical data. β, which influences the skin friction"s distribution, mainly inf  luences stresses of the points above the piles bottom surface, while it has little influence on stresses of the points below the piles bottom surface. So the prescription in the code that β can be taken as zero for general frictional pile foundations when only considering compression of the soil below the piles bottom surface is feasible.

Keywords:pile foundation； settlement； stress concentration； additional stress； skin friction