mindlin解均化应力分层总和法计算群桩基础沉降

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1、第47卷第5期2014年5月土木工程学报CHINACIVILENGINEEＲINGJOUＲNALVol．47MayNo．52014Mindlin解均化应力分层总和法计算群桩基础沉降刘金砺邱明兵秋仁东高文生(中国建筑科学研究院，北京100013)摘要:对考虑桩径因素的Mindlin解群桩应力场剖析表明:端阻应力在桩端下2d范围呈现明显的应力集中现象，在竖向和水平向衰减迅速;侧阻应力在桩端平面分布明显不均，至桩端下1d平面趋于均匀，沿深度和水平向衰减较慢。按半无限体表面荷载下的Boussinesq解计算的群桩应力显

2、著偏大，致使按实体深基法计算的桩基沉降需乘以0．25～0．5经验系数折减。桩基沉降计算采用Mindlin解计算附加应力的合理性是明显的，但按习用的自由荷载下应力叠加法计算将导致中点沉降偏大、边角点偏小。基于群桩Mindlin解附加应力场和群桩基础变形特征，考虑承台和上部结构刚度对沉降变形的均化效应，提出Mindlin解均化应力分层总和法计算群桩基础沉降。该方法具有如下特点:一是可反映桩端应力集中贯入变形;二是可近似反映承台和上部结构刚度的影响;三是可查表或采用程序进行计算，操作简便;四是计算值与实测值、规范统计值接近

3、，初步预计无需修正。关键词:Mindlin解;群桩;应力场;均化应力;沉降计算中图分类号:TU473文献标识码:A文章编号:1000-131X(2014)05-0118-10AlayerwisesummationmethodforsettlementcalculationofpilegroupbasedonthehomogenizedMindlinstressLiuJinliQiuMingbingQiuＲendongGaoWensheng(ChinaAcademyofBuildingＲesearch，Beijing1

4、0013，China)Abstract:BasedontheMindlinstresssolutionwiththepile-diametereffectconsidered，itisseenthatpile-tipstressconcentrationmayappearwithintherangeoftwopilediametersbelowthepiletip，butthepile-tipstressattenuatesinthehorizontalandverticaldirections．Thesideres

5、istanceofthepilegroupisnotuniformlydistributedatthepiletip，butitiswelldistributedatonepilediameterabovethepiletip，andthesideresistanceattenuatesslightlyalongtheverticalandhorizontaldirections．SincethesettlementcalculationresultsbasedontheBoussinesqstresstheorya

6、relargerthantherealisticones，anempiricalcoefficientof0．25～0．5shouldbemultipliedtothepile-groupsettlementcalculatedfromsolidfoundationapproach．ItisreasonabletoapplytheMindlinstresstheorytocalculatetheadditionalstressofthepile-groupfoundation．However，calculatingt

7、headditionalstressofpile-groupfoundationwiththetraditionalstresssuperpositionmethodunderfreeloadsmayleadtothelargersettlementatthecenterandthesmallersettlementatthecorners．BasedonthestressfieldcalculatedbytheMindlinstresstheorywiththepilediametereffectconsidere

8、d，thedeformationbehaviorofthepile-groupfoundationaswellasthehomogenizationeffectofpilecapandthesuperstructurestiffnessonthesettlementdeformation，alayerwisesummationmethodfor