地基基础检测 技术 Theoretical knowledge of rock foundation load tests for foundation testing technology-岩基 载荷试验理论知03课件讲解

地基基础检测技术岩基载荷试验理论知识

Theoreticalknowledgeofrockfoundationloadtestsforfoundationtestingtechnology是指确定完整、较完整、较破碎岩基作为天然地基或桩基础持力层承载力与变形参数的平板载荷试验，又称为岩基载荷试验。

Itreferstotheplateloadtesttodeterminethebearingcapacityanddeformationparametersoftheintact,relativelyintactandrelativelybrokenrockfoundationasnaturalfoundationorbearingstratumofpilefoundation,alsocalledrockfoundationloadtest.岩石地基载荷试验

RockFoundationLoadTest本视频以GB50007-2011为主进行讲解

ThisvideofocusesonGB50007-2011岩基载荷试验

Rockfoundationloadtest010101岩基载荷试验

Rockfoundationloadtest1.适用范围

1.ScopeofApplication岩基载荷试验

Rockfoundationloadtest适用于确定完整、较完整、较破碎岩石地基作为天然地基或桩基础持力层时的承载力。

Itissuitablefordeterminingthebearingcapacityofintact,relativelyintactandrelativelybrokenrockfoundationasnaturalfoundationorbearingstratumofpilefoundation.岩基载荷试验

Rockfoundationloadtest其岩性应为完整、较完整、较破碎岩石

Thelithologyshallbeintact,relativelyintactandrelativelybrokenrock岩基载荷试验

RockFoundationLoadTest检测天然岩石地基的承载力和变形参数

Testthebearingcapacityanddeformationparametersofnaturalrockfoundation检测桩端持力层的承载力和变形参数

Testthebearingcapacityanddeformationparametersofthebearingcourseatpileend1.适用范围

1.ScopeofApplication岩基载荷试验

Rockfoundationloadtest单位工程检测数量为每500m2不应少于1点，且总点数不应少于3点；

Thetestquantityofunitworksshallnotbelessthan1pointper500m2,andthetotalnumberofpointsshallnotbelessthan3;复杂场地或重要建筑地基应增加检测数量。

Thetestquantityshallbeincreasedforfoundationsofcomplexsitesorimportantbuildings.2.数量要求

2.Quantityrequirement岩基载荷试验

Rockfoundationloadtest试坑标高应与地基设计标高一致。当设计有要求时，承压板应设置于设计要求的受检岩基上。

Theelevationofthetestpitshallbeconsistentwiththedesignelevationofthefoundation.Whenrequiredbythedesign,thebearingplateshallbesetonthetestedrockfoundationrequiredbythedesign.3.场地处理

3.Sitetreatment岩基载荷试验

Rockfoundationloadtest试验前应采取措施，保持试坑或试井底岩土的原状结构和天然湿度不变。当试验标高低于地下水位时，应将地下水位降至试验标高以下，再安装试验设备，待水位恢复后方可进行试验。

Beforethetest,measuresshallbetakentomaintaintheundisturbedstructureandnaturalhumidityunchangedoftherockandsoil

atthebottomofthetestpitortestwell.Whenthetestelevationislowerthanthegroundwaterlevel,thegroundwaterlevelshallbeloweredbelowthetestelevation,andtheninstallthetestequipment,andcarryoutthetestafterthewaterlevelisrestored.3.场地处理

3.Sitetreatment岩基载荷试验

Rockfoundationloadtest在拟试压表面和承压板之间应用粗砂或中砂层找平，其厚度不应超过20mm。

Levelingwithcoarsesandormediumsandlayerbetweenthesurfacetobetestedandthebearingplate,anditsthicknessshallnotexceed20mm.3.场地处理

3.Sitetreatment岩基载荷试验

Rockfoundationloadtest原状结果

Undisturbedstructure天然湿度

Naturalhumidity基于岩石地基的工程特性

Engineeringcharacteristicsbasedonrockfoundation避免岩基扰动

Avoiddisturbanceoftherockfoundation岩基载荷试验

Rockfoundationloadtest饱和极限抗压强度

Saturatedultimatecompressivestrength

饱和极限抗压强度

SaturatedultimatecompressivestrengthKd<0.75时，

WhenKd<0.75,为易软化的岩石

Therockiseasytosoften花岗岩、砂岩、石灰岩、片麻岩

Granite,sandstone,limestoneandgneiss岩石有遇水软化、强度降低的特性，以软化系数(Kd)表示。

Rockischaracterizedbysofteninginwaterandstrengthreduction,expressedbysofteningcoefficient(Kd).岩基载荷试验

Rockfoundationloadtest地表或接近地表的岩石在大气、水和生物活动等因素的影响下，发生物理和化学的变化，致使岩石崩解和破碎，这种作用称为风化作用。

Undertheinfluenceofatmosphericwaterandbiologicalactivities,thephysicalandchemicalchangesinrocksatornearthesurfacethatcausethemtodisintegrateandfragment,whichiscalledweathering.地表最明显，往深处则逐渐消失。

Itismostobviousonthesurfaceandgraduallydisappearsdeeper.各地风化的深度不一致，浅的仅几十厘米，深的可达几百米。

Thedepthofweatheringvariesfromdozensofcentimeterstohundredsofmeters.风化作用→岩石的成分发生变化→坚硬的岩石变得松软甚至破坏成松散的碎屑→岩石的物理性质改变→力学强度降低。

Weathering→changeofrockcomposition→softeningorevendestructionofhardrockintoloosedebris→changeofphysicalpropertiesofrock→decreaseofmechanicalstrength.岩基载荷试验

Rockfoundationloadtest物理风化

Physicalweathering风化作用

Weathering化学风化

Chemicalweathering生物风化

Biologicalweathering化学风化过程中“水”是作为主要反应物参与其中的(例如:CasO4+2H-0→CaSO4·2H-O)

"Water"isinvolvedasamainreactantinthechemicalweatheringprocess(e.g.CasO4+2H-0→CaSO4·2H-O)仪器设备及安装

Instrumentsandequipmentandtheirinstallation0102岩基载荷试验

Rockfoundationloadtest1.适用范围

1.ScopeofApplicationfrk︰岩石试件的室内饱和单轴抗压强度标准值，仅代表小体积试件的强度，不能代表整个地基的强度

frk:Thestandardvalueofindoorsaturateduniaxialcompressivestrengthofrocktestpieces,whichonlyrepresentsthestrengthofsmallvolumetestpiecesandcannotrepresentthestrengthofthewholefoundation岩基载荷试验

RockFoundationLoadTest由成因类型和风化程度决定

Bythegenetictypeandweatheringdegree由成因类型和风化程度决定

Bythegenetictypeandweatheringdegree岩基载荷试验

Rockfoundationloadtest因此，在确定岩石地基的承载力时还需考虑岩体是否完整。

Therefore,itisalsonecessarytoconsiderwhethertherockmassisintactwhendeterminingthebearingcapacityofrockfoundation.对完整、较完整和较破碎的岩石地基，可根据岩体的完整程度，将frk乘以0.5~0.1的折减系数后，作为承载力特征值采用。

Forintact,relativelyintactandrelativelybrokenrockfoundation,accordingtotheintegrityofrockmass,frkcanbemultipliedbyareductionfactorof0.5~0.1,andthenusedasthecharacteristicvalueofbearingcapacity.岩基载荷试验

Rockfoundationloadtest改变岩基天然湿度(如降水)

Changethenaturalhumidityofrockfoundation(suchasprecipitation)改变岩石的力学性质

Changethemechanicalpropertiesoftherock改变岩体的工程特性

Changetheengineeringcharacteristicsofrockmass仪器设备及安装

Instrumentsandequipmentandtheirinstallation为什么要在承压板底面下铺砂?

Whysandpavingunderthebottomsurfaceofthebearingplate?起找平作用。

Forlevellingpurposes.注意：找平砂层应尽可能薄；并保证承压板与土之间有良好的接触，同时避免应力集中。

Note:Thelevellingsandlayershallbeasthinaspossible;andensuregoodcontactbetweenthebearingplateandsoil,andavoidstressconcentration.岩基载荷试验

Rockfoundationloadtest采用圆形刚性承压板，直径为300mm。当岩石埋藏深度较大时，可采用钢筋混凝土桩，但桩周需采取措施以消除桩身与土之间的摩擦力。

Circularrigidbearingplatewithadiameterof300mmisadopted.Whentheburialdepthofrockislarge,reinforcedconcretepilescanbeused,however,measuresshallbetakenaroundthepiletoeliminatethefrictionbetweenthepilebodyandthesoil.4.承压板

4.Bearingplate岩基载荷试验

Rockfoundationloadtest因此，较破碎岩基载荷试验的承压板直径可考虑大于0.3m。

Therefore,thediameterofthebearingplatefortheloadtestofrelativelybrokenrockfoundationcanbeconsideredtobegreaterthan0.3m.4.承压板

4.Bearingplate对于较破碎岩石地基，采用0.3m的直径承压板可能会影响试验结果的准确性。

Theuseofa0.3mdiameterbearingplateforrelativelybrokenrockfoundationmayaffecttheaccuracyofthetestresults.注意

Notes岩基载荷试验

Rockfoundationloadtest为什么要在承压板底面下铺砂?

Whysandpavingunderthebottomsurfaceofthebearingplate?起找平作用。

Forlevellingpurposes.注意：找平砂层应尽可能薄；并保证承压板与土之间有良好的接触，同时避免应力集中。

Note:Thelevellingsandlayershallbeasthinaspossible;andensuregoodcontactbetweenthebearingplateandsoil,andavoidstressconcentration.岩基载荷试验

Rockfoundationloadtest当岩石埋藏深度较大、采用钢筋混凝土桩时，为什么需要采取措施消除桩身与土之间的摩擦力?

Whentheburialdepthofrockislargeandreinforcedconcretepilesareused,whyshouldmeasuresbetakentoeliminatethefrictionbetweenthepilebodyandthesoil?目的是使荷载读数不打折扣，否则会发生读数大于实际荷载的情况。

Thepurposeistomaketheloadreadingsundiscounted,otherwisethereadingswillbegreaterthantheactualload.岩基载荷试验

Rockfoundationloadtest压重平台反力装置

Reactiondeviceofballastplatform加载反力宜选择压重平台反力装置

(同浅层平板载荷试验)

Thereactiondeviceofballastplatformshallbeselectedforloadingreaction(thesameasshallowplateloadtest)岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest正式试验前宜进行预压。

Preloadingshallbecarriedoutbeforeformaltest.预压荷载宜为最大加载量的5%，预压时间宜5min。

Thepreloadingloadshallbe5%ofthemaximumloadingcapacity,andthepreloadingtimeshallbe5min.预压后卸载至零，测读位移测量仪表的初始读数并应重新调整零位。

Unloadtozeroafterpreloading,measureandreadtheinitialreadingofthedisplacementmeasuringinstrumentandreadjustthezeroposition.预

压

Preloading岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest工程验收检测的岩石地基载荷试验最大加载量不应小于设计承载力特征值的3倍；

Themaximumloadingcapacityofrockfoundationloadtestforprojectacceptancetestshallnotbelessthan3timesofthecharacteristicvalueofdesignbearingcapacity;为设计提供依据的载荷试验应加载至极限状态。

Theloadtestprovidingthebasisfordesignshallbeloadedtothelimitstate.注

意

Attention岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest加载应采用单循环加载，荷载逐级递增直到破坏，然后分级卸载。

Singlecycleloadingshallbeadopted,andtheloadshallbeincreasedstepbystepuntilfailure,andthenunloadedinstages.第一级加载值应为预估设计荷载的1/5，以后每级应为预估设计荷载的1/10。

Theloadingvalueofthefirststageshallbe1/5oftheestimateddesignload,andthatofeachsubsequentstageshallbe1/10oftheestimateddesignload.加载方式

Loadingmode岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest沉降量测读应在加载后立即进行，以后每10min读数一次。

Thesettlementmeasurementandreadingshallbecarriedoutimmediatelyafterloading,andshallbecarriedoutevery10minthereafter.连续三次读数之差均不大于0.01mm，可视为达到稳定标准，可施加下一级荷载。

Ifthedifferencebetweenthreeconsecutivereadingsshallnotbegreaterthan0.01mm,itcanbeconsideredasreachingthestabilitystandardandtheloadofnextstepcanbeapplied.沉降量测读

Settlementmeasurementandreading岩基载荷试验

Rockfoundationloadtest规定：岩基载荷试验的沉降稳定标准为连续三次读数之差均不大于0.01mm

Regulations:Thesettlementstabilitystandardofrockfoundationloadtestisthatthedifferencebetweenthreeconsecutivereadingsisnotmorethan0.01mm6.现场检测

6.Fieldtest修改为：30min读数之差小于0.03mm，并在四次读数中连续出现两次(JGJ340-2015和广东地规有类似规定)

Modifiedto:Thedifferencebetweenreadingsin30minislessthan0.03mm,andtwoconsecutiveoccurrencesoffourreadings(JGJ340-2015andGuangdongLocalRegulationshavesimilarprovisions)岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest当出现下列情况之一时，即可终止加载:

Loadingcanbeterminatedwhenoneofthefollowingconditionsoccurs:①沉降量读数不断变化，在24h内，沉降速率有增大的趋势;

①Thereadingofsettlementchangescontinuously,andthesettlementratetendstoincreasewithin24h;②压力加不上或勉强加上而不能保持稳定。

②Thepressurecannotbeaddedorisbarelyaddedtokeepstable.终止加载

Terminateloading注：若限于加载能力，荷载也应增加到不少于设计要求的2倍。

Note:Iflimitedtotheloadingcapacity,theloadshallalsobeincreasedtonotlessthan2timesthedesignrequirements.岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest承压板上和板外的测表不停地变化，这种变化有增加的趋势;

Thegaugesonandoutsidethebearingplatechangeconstantly,andthischangetendstoincrease;有时还表现为荷载加不上，或加上去后很快降下来。

Sometimes,itisalsomanifestedastheloadcannotbeadded,ordropsquicklyafterbeingadded.确定终止试验的标准(岩体)

Standardfordeterminingtheterminationofthetest(rockmass)如果荷载已达到设备的最大出力，则不得不终止试验，但应判定是否满足了试验要求。

Iftheloadhasreachedthemaximumoutputoftheequipment,thetesthastobeterminated,butitshallbedeterminedwhetherthetestrequirementsaremet.岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest卸载及卸载观测应符合下列规定:

Unloadingandunloadingobservationshallmeetthefollowingrequirements:①每级卸载为加载时的2倍，如为奇数，第一级可为3倍;

①Eachstepisunloadedby2timeswhenloading.Ifitisanoddnumber,thefirststepcanbe3times;②每级卸载后，隔10min测读一次，测读三次后可卸下一级荷载;

②Aftereachstepofunloading,measureandreadonceevery10min,andthenunloadthenextstepofloadafterthreemeasurementsandreadings;③全部卸载后，当测读到半小时回弹量小于0.01mm时，即认为达到稳定。

③Afterallunloading,whenthemeasuredreboundamountislessthan0.01mminhalfanhour,itisconsideredstable.卸

载

Unloading如果荷载已达到设备的最大出力，则不得不终止试验，但应判定是否满足了试验要求。

Iftheloadhasreachedthemaximumoutputoftheequipment,thetesthastobeterminated,butitshallbedeterminedwhetherthetestrequirementsaremet.岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest通过卸载可读取弹性变形和残余变形，进而对岩基的岩体力学性质做进一步印证。

Elasticdeformationandresidualdeformationcanbereadbyunloading,whichfurtherconfirmsthemechanicalpropertiesofrockmassofrockfoundation.注

意

Attention岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest卸载及卸载观测应符合下列规定:

Unloadingandunloadingobservationshallmeetthefollowingrequirements:①每级卸载为加载时的2倍，如为奇数，第一级可为3倍;

①Eachstepisunloadedby2timeswhenloading.Ifitisanoddnumber,thefirststepcanbe3times;②每级卸载后，隔10min测读一次，测读三次后可卸下一级荷载;

②Aftereachstepofunloading,measureandreadonceevery10min,andthenunloadthenextstepofloadafterthreemeasurementsandreadings;③全部卸载后，当测读到半小时回弹量小于0.01mm时，即认为达到稳定。

③Afterallunloading,whenthemeasuredreboundamountislessthan0.01mminhalfanhour,itisconsideredstable.岩基承载力的确定

Determinationofbearingcapacityofrockfoundation岩基载荷试验

Rockfoundationloadtest6.现场检测

6.Fieldtest岩石地基承载力特征值的确定应符合下列规定:

Thedeterminationofcharacteristicvalueofbearingcapacityofrockfoundationshallmeetthefollowingrequirements:①对应于p-s曲线上起始直线段的终点为比例界限。符合终止加载条件的前一级荷载为极限荷载。将极限荷载除以3的安全系数，所得值与对应于比例界限的荷载相比较，取小值。

①Theendpointcorrespondingtothestartingstraightsectiononthep-scurveistheproportionlimit.Theloadofthepreviousstepmeetingtheloadingterminationconditionsistheultimateload.Thevalueobtainedbydividingtheultimateloadbyasafetyfactorof3iscomparedwiththeloadcorrespondingtotheproportionlimit,whicheverissmaller.岩基承载力的确定

Determinationofbearingcapacityofrockfoundation岩基载荷试验

Rockfoundationloadtest取该比例界所对应的荷载值

TheproportionallimitshallbetakenCorrespondingloadvalue对应的荷载下，岩基变形尚处于弹性状态，如此取值偏于安全

Underthecorrespondingload,thedeformationofrockfoundationisstillinanelasticstate,sothevalueissafe取极限荷载值的1/3

Takeultimateload1/3ofvalue体现了对岩石地基承载力较高安全储备的要求

Reflectingtherequirementofhighsafetyreserveforbe