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（1 清華大學(xué)土木工程系，北京，100084；2天津農(nóng)學(xué)院水利工程系 300384；3 天津大學(xué)水利工程系 300072）

［提要］通過自編的Mindlin群樁沉降計(jì)算軟件，對(duì)規(guī)范中新引入的群樁沉降計(jì)算方法——Mindlin方法中兩個(gè)重要計(jì)算參數(shù)α，β的影響進(jìn)行了研究分析。α對(duì)樁端附近上下各約8d范圍內(nèi)應(yīng)力相對(duì)集中區(qū)域的應(yīng)力場(chǎng)影響較為明顯，從而影響沉降計(jì)算結(jié)果，因此應(yīng)根據(jù)工程經(jīng)驗(yàn)或?qū)崪y(cè)資料合理確定α值；β取值大小決定了樁側(cè)摩阻力的分布形式，其影響主要體現(xiàn)在樁身范圍內(nèi)，而對(duì)樁端以下應(yīng)力場(chǎng)的影響較小，因而規(guī)范規(guī)定對(duì)于一般的摩擦型群樁基礎(chǔ)，采用此法計(jì)算樁基沉降（只計(jì)算樁端以下地基土的壓縮量）時(shí)可取β＝0的做法是可行的。

［關(guān)鍵詞］樁基礎(chǔ)；沉降；應(yīng)力集中；附加應(yīng)力；樁側(cè)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