地基基礎(chǔ)檢測 技術(shù) Theoretical knowledge of rock foundation load tests for foundation testing technology-巖基 載荷試驗理論知03課件講解

地基基礎(chǔ)檢測技術(shù)巖基載荷試驗理論知識

Theoreticalknowledgeofrockfoundationloadtestsforfoundationtestingtechnology是指確定完整、較完整、較破碎巖基作為天然地基或樁基礎(chǔ)持力層承載力與變形參數(shù)的平板載荷試驗，又稱為巖基載荷試驗。

Itreferstotheplateloadtesttodeterminethebearingcapacityanddeformationparametersoftheintact,relativelyintactandrelativelybrokenrockfoundationasnaturalfoundationorbearingstratumofpilefoundation,alsocalledrockfoundationloadtest.巖石地基載荷試驗

RockFoundationLoadTest本視頻以GB50007-2011為主進(jìn)行講解

ThisvideofocusesonGB50007-2011巖基載荷試驗

Rockfoundationloadtest010101巖基載荷試驗

Rockfoundationloadtest1.適用范圍

1.ScopeofApplication巖基載荷試驗

Rockfoundationloadtest適用于確定完整、較完整、較破碎巖石地基作為天然地基或樁基礎(chǔ)持力層時的承載力。

Itissuitablefordeterminingthebearingcapacityofintact,relativelyintactandrelativelybrokenrockfoundationasnaturalfoundationorbearingstratumofpilefoundation.巖基載荷試驗

Rockfoundationloadtest其巖性應(yīng)為完整、較完整、較破碎巖石

Thelithologyshallbeintact,relativelyintactandrelativelybrokenrock巖基載荷試驗

RockFoundationLoadTest檢測天然巖石地基的承載力和變形參數(shù)

Testthebearingcapacityanddeformationparametersofnaturalrockfoundation檢測樁端持力層的承載力和變形參數(shù)

Testthebearingcapacityanddeformationparametersofthebearingcourseatpileend1.適用范圍

1.ScopeofApplication巖基載荷試驗

Rockfoundationloadtest單位工程檢測數(shù)量為每500m2不應(yīng)少于1點(diǎn)，且總點(diǎn)數(shù)不應(yīng)少于3點(diǎn)；

Thetestquantityofunitworksshallnotbelessthan1pointper500m2,andthetotalnumberofpointsshallnotbelessthan3;復(fù)雜場地或重要建筑地基應(yīng)增加檢測數(shù)量。

Thetestquantityshallbeincreasedforfoundationsofcomplexsitesorimportantbuildings.2.數(shù)量要求

2.Quantityrequirement巖基載荷試驗

Rockfoundationloadtest試坑標(biāo)高應(yīng)與地基設(shè)計標(biāo)高一致。當(dāng)設(shè)計有要求時，承壓板應(yīng)設(shè)置于設(shè)計要求的受檢巖基上。

Theelevationofthetestpitshallbeconsistentwiththedesignelevationofthefoundation.Whenrequiredbythedesign,thebearingplateshallbesetonthetestedrockfoundationrequiredbythedesign.3.場地處理

3.Sitetreatment巖基載荷試驗

Rockfoundationloadtest試驗前應(yīng)采取措施，保持試坑或試井底巖土的原狀結(jié)構(gòu)和天然濕度不變。當(dāng)試驗標(biāo)高低于地下水位時，應(yīng)將地下水位降至試驗標(biāo)高以下，再安裝試驗設(shè)備，待水位恢復(fù)后方可進(jìn)行試驗。

Beforethetest,measuresshallbetakentomaintaintheundisturbedstructureandnaturalhumidityunchangedoftherockandsoil

atthebottomofthetestpitortestwell.Whenthetestelevationislowerthanthegroundwaterlevel,thegroundwaterlevelshallbeloweredbelowthetestelevation,andtheninstallthetestequipment,andcarryoutthetestafterthewaterlevelisrestored.3.場地處理

3.Sitetreatment巖基載荷試驗

Rockfoundationloadtest在擬試壓表面和承壓板之間應(yīng)用粗砂或中砂層找平，其厚度不應(yīng)超過20mm。

Levelingwithcoarsesandormediumsandlayerbetweenthesurfacetobetestedandthebearingplate,anditsthicknessshallnotexceed20mm.3.場地處理

3.Sitetreatment巖基載荷試驗

Rockfoundationloadtest原狀結(jié)果

Undisturbedstructure天然濕度

Naturalhumidity基于巖石地基的工程特性

Engineeringcharacteristicsbasedonrockfoundation避免巖基擾動

Avoiddisturbanceoftherockfoundation巖基載荷試驗

Rockfoundationloadtest飽和極限抗壓強(qiáng)度

Saturatedultimatecompressivestrength

飽和極限抗壓強(qiáng)度

SaturatedultimatecompressivestrengthKd<0.75時，

WhenKd<0.75,為易軟化的巖石

Therockiseasytosoften花崗巖、砂巖、石灰?guī)r、片麻巖

Granite,sandstone,limestoneandgneiss巖石有遇水軟化、強(qiáng)度降低的特性，以軟化系數(shù)(Kd)表示。

Rockischaracterizedbysofteninginwaterandstrengthreduction,expressedbysofteningcoefficient(Kd).巖基載荷試驗

Rockfoundationloadtest地表或接近地表的巖石在大氣、水和生物活動等因素的影響下，發(fā)生物理和化學(xué)的變化，致使巖石崩解和破碎，這種作用稱為風(fēng)化作用。

Undertheinfluenceofatmosphericwaterandbiologicalactivities,thephysicalandchemicalchangesinrocksatornearthesurfacethatcausethemtodisintegrateandfragment,whichiscalledweathering.地表最明顯，往深處則逐漸消失。

Itismostobviousonthesurfaceandgraduallydisappearsdeeper.各地風(fēng)化的深度不一致，淺的僅幾十厘米，深的可達(dá)幾百米。

Thedepthofweatheringvariesfromdozensofcentimeterstohundredsofmeters.風(fēng)化作用→巖石的成分發(fā)生變化→堅硬的巖石變得松軟甚至破壞成松散的碎屑→巖石的物理性質(zhì)改變→力學(xué)強(qiáng)度降低。

Weathering→changeofrockcomposition→softeningorevendestructionofhardrockintoloosedebris→changeofphysicalpropertiesofrock→decreaseofmechanicalstrength.巖基載荷試驗

Rockfoundationloadtest物理風(fēng)化

Physicalweathering風(fēng)化作用

Weathering化學(xué)風(fēng)化

Chemicalweathering生物風(fēng)化

Biologicalweathering化學(xué)風(fēng)化過程中“水”是作為主要反應(yīng)物參與其中的(例如:CasO4+2H-0→CaSO4·2H-O)

"Water"isinvolvedasamainreactantinthechemicalweatheringprocess(e.g.CasO4+2H-0→CaSO4·2H-O)儀器設(shè)備及安裝

Instrumentsandequipmentandtheirinstallation0102巖基載荷試驗

Rockfoundationloadtest1.適用范圍

1.ScopeofApplicationfrk︰巖石試件的室內(nèi)飽和單軸抗壓強(qiáng)度標(biāo)準(zhǔn)值，僅代表小體積試件的強(qiáng)度，不能代表整個地基的強(qiáng)度

frk:Thestandardvalueofindoorsaturateduniaxialcompressivestrengthofrocktestpieces,whichonlyrepresentsthestrengthofsmallvolumetestpiecesandcannotrepresentthestrengthofthewholefoundation巖基載荷試驗

RockFoundationLoadTest由成因類型和風(fēng)化程度決定

Bythegenetictypeandweatheringdegree由成因類型和風(fēng)化程度決定

Bythegenetictypeandweatheringdegree巖基載荷試驗

Rockfoundationloadtest因此，在確定巖石地基的承載力時還需考慮巖體是否完整。

Therefore,itisalsonecessarytoconsiderwhethertherockmassisintactwhendeterminingthebearingcapacityofrockfoundation.對完整、較完整和較破碎的巖石地基，可根據(jù)巖體的完整程度，將frk乘以0.5~0.1的折減系數(shù)后，作為承載力特征值采用。

Forintact,relativelyintactandrelativelybrokenrockfoundation,accordingtotheintegrityofrockmass,frkcanbemultipliedbyareductionfactorof0.5~0.1,andthenusedasthecharacteristicvalueofbearingcapacity.巖基載荷試驗

Rockfoundationloadtest改變巖基天然濕度(如降水)

Changethenaturalhumidityofrockfoundation(suchasprecipitation)改變巖石的力學(xué)性質(zhì)

Changethemechanicalpropertiesoftherock改變巖體的工程特性

Changetheengineeringcharacteristicsofrockmass儀器設(shè)備及安裝

Instrumentsandequipmentandtheirinstallation為什么要在承壓板底面下鋪砂?

Whysandpavingunderthebottomsurfaceofthebearingplate?起找平作用。

Forlevellingpurposes.注意：找平砂層應(yīng)盡可能??；并保證承壓板與土之間有良好的接觸，同時避免應(yīng)力集中。

Note:Thelevellingsandlayershallbeasthinaspossible;andensuregoodcontactbetweenthebearingplateandsoil,andavoidstressconcentration.巖基載荷試驗

Rockfoundationloadtest采用圓形剛性承壓板，直徑為300mm。當(dāng)巖石埋藏深度較大時，可采用鋼筋混凝土樁，但樁周需采取措施以消除樁身與土之間的摩擦力。

Circularrigidbearingplatewithadiameterof300mmisadopted.Whentheburialdepthofrockislarge,reinforcedconcretepilescanbeused,however,measuresshallbetakenaroundthepiletoeliminatethefrictionbetweenthepilebodyandthesoil.4.承壓板

4.Bearingplate巖基載荷試驗

Rockfoundationloadtest因此，較破碎巖基載荷試驗的承壓板直徑可考慮大于0.3m。

Therefore,thediameterofthebearingplatefortheloadtestofrelativelybrokenrockfoundationcanbeconsideredtobegreaterthan0.3m.4.承壓板

4.Bearingplate對于較破碎巖石地基，采用0.3m的直徑承壓板可能會影響試驗結(jié)果的準(zhǔn)確性。

Theuseofa0.3mdiameterbearingplateforrelativelybrokenrockfoundationmayaffecttheaccuracyofthetestresults.注意

Notes巖基載荷試驗

Rockfoundationloadtest為什么要在承壓板底面下鋪砂?

Whysandpavingunderthebottomsurfaceofthebearingplate?起找平作用。

Forlevellingpurposes.注意：找平砂層應(yīng)盡可能?。徊⒈ＷC承壓板與土之間有良好的接觸，同時避免應(yīng)力集中。

Note:Thelevellingsandlayershallbeasthinaspossible;andensuregoodcontactbetweenthebearingplateandsoil,andavoidstressconcentration.巖基載荷試驗

Rockfoundationloadtest當(dāng)巖石埋藏深度較大、采用鋼筋混凝土樁時，為什么需要采取措施消除樁身與土之間的摩擦力?

Whentheburialdepthofrockislargeandreinforcedconcretepilesareused,whyshouldmeasuresbetakentoeliminatethefrictionbetweenthepilebodyandthesoil?目的是使荷載讀數(shù)不打折扣，否則會發(fā)生讀數(shù)大于實際荷載的情況。

Thepurposeistomaketheloadreadingsundiscounted,otherwisethereadingswillbegreaterthantheactualload.巖基載荷試驗

Rockfoundationloadtest壓重平臺反力裝置

Reactiondeviceofballastplatform加載反力宜選擇壓重平臺反力裝置

(同淺層平板載荷試驗)

Thereactiondeviceofballastplatformshallbeselectedforloadingreaction(thesameasshallowplateloadtest)巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest正式試驗前宜進(jìn)行預(yù)壓。

Preloadingshallbecarriedoutbeforeformaltest.預(yù)壓荷載宜為最大加載量的5%，預(yù)壓時間宜5min。

Thepreloadingloadshallbe5%ofthemaximumloadingcapacity,andthepreloadingtimeshallbe5min.預(yù)壓后卸載至零，測讀位移測量儀表的初始讀數(shù)并應(yīng)重新調(diào)整零位。

Unloadtozeroafterpreloading,measureandreadtheinitialreadingofthedisplacementmeasuringinstrumentandreadjustthezeroposition.預(yù)

壓

Preloading巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest工程驗收檢測的巖石地基載荷試驗最大加載量不應(yīng)小于設(shè)計承載力特征值的3倍；

Themaximumloadingcapacityofrockfoundationloadtestforprojectacceptancetestshallnotbelessthan3timesofthecharacteristicvalueofdesignbearingcapacity;為設(shè)計提供依據(jù)的載荷試驗應(yīng)加載至極限狀態(tài)。

Theloadtestprovidingthebasisfordesignshallbeloadedtothelimitstate.注

意

Attention巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest加載應(yīng)采用單循環(huán)加載，荷載逐級遞增直到破壞，然后分級卸載。

Singlecycleloadingshallbeadopted,andtheloadshallbeincreasedstepbystepuntilfailure,andthenunloadedinstages.第一級加載值應(yīng)為預(yù)估設(shè)計荷載的1/5，以后每級應(yīng)為預(yù)估設(shè)計荷載的1/10。

Theloadingvalueofthefirststageshallbe1/5oftheestimateddesignload,andthatofeachsubsequentstageshallbe1/10oftheestimateddesignload.加載方式

Loadingmode巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest沉降量測讀應(yīng)在加載后立即進(jìn)行，以后每10min讀數(shù)一次。

Thesettlementmeasurementandreadingshallbecarriedoutimmediatelyafterloading,andshallbecarriedoutevery10minthereafter.連續(xù)三次讀數(shù)之差均不大于0.01mm，可視為達(dá)到穩(wěn)定標(biāo)準(zhǔn)，可施加下一級荷載。

Ifthedifferencebetweenthreeconsecutivereadingsshallnotbegreaterthan0.01mm,itcanbeconsideredasreachingthestabilitystandardandtheloadofnextstepcanbeapplied.沉降量測讀

Settlementmeasurementandreading巖基載荷試驗

Rockfoundationloadtest規(guī)定：巖基載荷試驗的沉降穩(wěn)定標(biāo)準(zhǔn)為連續(xù)三次讀數(shù)之差均不大于0.01mm

Regulations:Thesettlementstabilitystandardofrockfoundationloadtestisthatthedifferencebetweenthreeconsecutivereadingsisnotmorethan0.01mm6.現(xiàn)場檢測

6.Fieldtest修改為：30min讀數(shù)之差小于0.03mm，并在四次讀數(shù)中連續(xù)出現(xiàn)兩次(JGJ340-2015和廣東地規(guī)有類似規(guī)定)

Modifiedto:Thedifferencebetweenreadingsin30minislessthan0.03mm,andtwoconsecutiveoccurrencesoffourreadings(JGJ340-2015andGuangdongLocalRegulationshavesimilarprovisions)巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest當(dāng)出現(xiàn)下列情況之一時，即可終止加載:

Loadingcanbeterminatedwhenoneofthefollowingconditionsoccurs:①沉降量讀數(shù)不斷變化，在24h內(nèi)，沉降速率有增大的趨勢;

①Thereadingofsettlementchangescontinuously,andthesettlementratetendstoincreasewithin24h;②壓力加不上或勉強(qiáng)加上而不能保持穩(wěn)定。

②Thepressurecannotbeaddedorisbarelyaddedtokeepstable.終止加載

Terminateloading注：若限于加載能力，荷載也應(yīng)增加到不少于設(shè)計要求的2倍。

Note:Iflimitedtotheloadingcapacity,theloadshallalsobeincreasedtonotlessthan2timesthedesignrequirements.巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest承壓板上和板外的測表不停地變化，這種變化有增加的趨勢;

Thegaugesonandoutsidethebearingplatechangeconstantly,andthischangetendstoincrease;有時還表現(xiàn)為荷載加不上，或加上去后很快降下來。

Sometimes,itisalsomanifestedastheloadcannotbeadded,ordropsquicklyafterbeingadded.確定終止試驗的標(biāo)準(zhǔn)(巖體)

Standardfordeterminingtheterminationofthetest(rockmass)如果荷載已達(dá)到設(shè)備的最大出力，則不得不終止試驗，但應(yīng)判定是否滿足了試驗要求。

Iftheloadhasreachedthemaximumoutputoftheequipment,thetesthastobeterminated,butitshallbedeterminedwhetherthetestrequirementsaremet.巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest卸載及卸載觀測應(yīng)符合下列規(guī)定:

Unloadingandunloadingobservationshallmeetthefollowingrequirements:①每級卸載為加載時的2倍，如為奇數(shù)，第一級可為3倍;

①Eachstepisunloadedby2timeswhenloading.Ifitisanoddnumber,thefirststepcanbe3times;②每級卸載后，隔10min測讀一次，測讀三次后可卸下一級荷載;

②Aftereachstepofunloading,measureandreadonceevery10min,andthenunloadthenextstepofloadafterthreemeasurementsandreadings;③全部卸載后，當(dāng)測讀到半小時回彈量小于0.01mm時，即認(rèn)為達(dá)到穩(wěn)定。

③Afterallunloading,whenthemeasuredreboundamountislessthan0.01mminhalfanhour,itisconsideredstable.卸

載

Unloading如果荷載已達(dá)到設(shè)備的最大出力，則不得不終止試驗，但應(yīng)判定是否滿足了試驗要求。

Iftheloadhasreachedthemaximumoutputoftheequipment,thetesthastobeterminated,butitshallbedeterminedwhetherthetestrequirementsaremet.巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest通過卸載可讀取彈性變形和殘余變形，進(jìn)而對巖基的巖體力學(xué)性質(zhì)做進(jìn)一步印證。

Elasticdeformationandresidualdeformationcanbereadbyunloading,whichfurtherconfirmsthemechanicalpropertiesofrockmassofrockfoundation.注

意

Attention巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest卸載及卸載觀測應(yīng)符合下列規(guī)定:

Unloadingandunloadingobservationshallmeetthefollowingrequirements:①每級卸載為加載時的2倍，如為奇數(shù)，第一級可為3倍;

①Eachstepisunloadedby2timeswhenloading.Ifitisanoddnumber,thefirststepcanbe3times;②每級卸載后，隔10min測讀一次，測讀三次后可卸下一級荷載;

②Aftereachstepofunloading,measureandreadonceevery10min,andthenunloadthenextstepofloadafterthreemeasurementsandreadings;③全部卸載后，當(dāng)測讀到半小時回彈量小于0.01mm時，即認(rèn)為達(dá)到穩(wěn)定。

③Afterallunloading,whenthemeasuredreboundamountislessthan0.01mminhalfanhour,itisconsideredstable.巖基承載力的確定

Determinationofbearingcapacityofrockfoundation巖基載荷試驗

Rockfoundationloadtest6.現(xiàn)場檢測

6.Fieldtest巖石地基承載力特征值的確定應(yīng)符合下列規(guī)定:

Thedeterminationofcharacteristicvalueofbearingcapacityofrockfoundationshallmeetthefollowingrequirements:①對應(yīng)于p-s曲線上起始直線段的終點(diǎn)為比例界限。符合終止加載條件的前一級荷載為極限荷載。將極限荷載除以3的安全系數(shù)，所得值與對應(yīng)于比例界限的荷載相比較，取小值。

①Theendpointcorrespondingtothestartingstraightsectiononthep-scurveistheproportionlimit.Theloadofthepreviousstepmeetingtheloadingterminationconditionsistheultimateload.Thevalueobtainedbydividingtheultimateloadbyasafetyfactorof3iscomparedwiththeloadcorrespondingtotheproportionlimit,whicheverissmaller.巖基承載力的確定

Determinationofbearingcapacityofrockfoundation巖基載荷試驗

Rockfoundationloadtest取該比例界所對應(yīng)的荷載值

TheproportionallimitshallbetakenCorrespondingloadvalue對應(yīng)的荷載下，巖基變形尚處于彈性狀態(tài)，如此取值偏于安全

Underthecorrespondingload,thedeformationofrockfoundationisstillinanelasticstate,sothevalueissafe取極限荷載值的1/3

Takeultimateload1/3ofvalue體現(xiàn)了對巖石地基承載力較高安全儲備的要求

Reflectingtherequirementofhighsafetyreserveforbe