《安全員》課件-03基坑工程檢測

《安全員》TheSecurity第三節(jié)基坑工程檢測Section3FoundationPitWorksInspection基坑支護結構監(jiān)測的主要手段，是安排專業(yè)施工監(jiān)測人員對基坑現(xiàn)場及周圍建筑物進行監(jiān)測，根據(jù)基坑開挖期間監(jiān)測到的基坑支護結構或巖土變位等情況，比照勘察、設計的預期性狀，動態(tài)分析監(jiān)測資料，全面掌握位移變化的大小、方向、變化頻率，對照報警標準，預測下一階段工作的動態(tài)，及時對施工中可能出現(xiàn)的險情進行預報，超過位移設定的預警值時，應及時采取有效的應對措施，確保工程安全。Themainmeansofmonitoringthefoundationsupportstructureistoarrangeforprofessionalconstructionmonitorstomonitorthefoundationpitsiteandsurroundingbuildings,andtoanalysethemonitoringdatadynamicallyaccordingtothefoundationsupportstructureorgeotechnicaldisplacementsandotherconditionsmonitoredduringtheexcavationofthefoundationpit,comparedtotheexpectedtraitsofthesurveyanddesign,tofullygraspthesize,directionandfrequencyofdisplacementchanges,topredictthedynamicsofthenextphaseofworkagainstthealarmcriteria,toforecastthepossibledangerinconstructioninatimelymanner,andtotakeeffectivecountermeasuresinatimelymannerwhentheearlywarningvaluesetfordisplacementisexceededtoensureprojectsafety.深基坑支護結構工程監(jiān)測的主要內容有：支護結構頂部水平位移；支護結構沉降和裂縫；臨近建筑物、道路的沉降、傾斜和裂縫；基坑底隆起的觀測等,并根據(jù)支護結構條件、基坑周邊環(huán)境的重要性及地質條件的復雜性確定檢測點部位及數(shù)量。Themaincontentsofthedeepfoundationpitsupportstructureengineeringmonitoringare:horizontaldisplacementofthetopofthesupportstructure;settlementandcracksofthesupportstructure;settlement,tiltandcracksoftheadjacentbuildingsandroads;observationoftheriseofthefoundationpitbottom,etc.,andaccordingtotheconditionsofthesupportstructure,theimportanceofthesurroundingenvironmentofthefoundationpitandthecomplexityofthegeologicalconditionstodeterminethepartsandnumberofdetectionpoints.通過對圍護墻（坡）頂水平位移和豎向位移監(jiān)測，可以掌握圍護墻（坡）體在基坑挖土施工過程中的平面和豎向變形情況，用于同設計比較，分析對周圍環(huán)境的影響。而圍護墻頂沉降值對掌握支護墻下臥層變形情況、防止整體滑移以及“兩墻合一”逆作法施工中分析差異沉降對主體結構影響都有很大意義。Bymonitoringthehorizontalandverticaldisplacementofthetopoftheretainingwall(slope),thehorizontalandverticaldeformationoftheretainingwall(slope)duringtheexcavationofthefoundationpitcanbegraspedandusedforcomparisonwiththedesignandanalysisoftheimpactonthesurroundingenvironment.Thesettlementvaluesatthetopoftheretainingwallareofgreatsignificanceinordertograspthedeformationofthelowerlayeroftheretainingwall,topreventoverallslippageandtoanalysetheimpactofdifferentialsettlementonthemainstructureduringtheconstructionofthe"twowallsinone"inversemethod.1.支護結構頂水平位移和豎向位移

1.Horizontalandverticaldisplacementofthetopofthesupportingstructure

支護結構在基坑挖土后，基坑內外的水土壓力平衡要依靠圍護墻體和支撐體系。圍護墻體在基坑外側水土壓力作用下，會發(fā)生變形。要掌握圍護墻體的側向變形，即在不同深度上各點的水平位移，需要通過對圍護墻體的測斜來實現(xiàn)，以便掌握支護結構的整體狀況。這是較深基坑工程監(jiān)測中一項重要的基本內容。

Afterthesupportstructureisexcavatedinthefoundationpit,thebalanceofsoilandwaterpressureinsideandoutsidethefoundationpitdependsontheenclosurewallandthesupportsystem.Theenclosurewallwilldeformundertheactionofsoilandwaterpressureoutsidethefoundationpit.Tograspthelateraldeformationoftheenclosurewall,i.e.thehorizontaldisplacementatvariouspointsatdifferentdepths,thisneedstobeachievedbyinclinationmeasurementoftheenclosurewallinordertograsptheoverallconditionofthesupportingstructure.Thisisanimportantandfundamentalelementinthemonitoringofdeeperfoundationworks.

2.支護結構深部水平位移

1.Horizontalandverticaldisplacementofthetopofthesupportingstructure

支護結構設計計算書一般可提供圍護墻體的理論計算結果，如彎矩和剪力等，但實際工程中由于勘察提供的數(shù)據(jù)與實際土體狀況、理論計算和實際受力狀況都存在一定差異，因此對圍護墻體內力監(jiān)測十分必要。工程中主要是針對圍護墻體的彎矩監(jiān)測，通過測試圍護墻體的主筋受力來分析圍護墻體承受的彎矩，以防止圍護墻體因強度不足而導致支護結構破壞。

Thedesigncalculationofthesupportingstructurecangenerallyprovidethetheoreticalcalculationresultsoftheenclosingwall,suchasbendingmomentandshearforce,butinactualengineering,asthedataprovidedbythesurveyandtheactualsoilconditions,theoreticalcalculationsandactualforceconditionsaresomewhatdifferent,soitisnecessarytomonitortheinternalforceoftheenclosingwall.Themainpurposeoftheprojectistomonitorthebendingmomentoftheenclosurewall,andtoanalysethebendingmomentbornebytheenclosurewallbytestingthemainreinforcementoftheenclosurewall,inordertopreventtheenclosurewallfrombeingdamagedbythesupportingstructureduetoinsufficientstrength.

3.支護結構內力

3.Internalforceofsupportingstructure

（1）內支撐體系

Internalsupportsystem內支撐體系的監(jiān)測分為支撐軸力、立柱位移。支撐基本上承受壓力，但也存在偏心荷載和橫向力（如上部的施工荷載等），支撐的彎曲變形或側向變形過大可能引起支撐失穩(wěn)。另一方面，所計算的支撐軸力為理論值，實際工程中，由于溫度影響、施工偏差等引起的附加內力，在計算中難以精確分析，通過監(jiān)測則能了解支撐實際的受力狀況。

Themonitoringoftheinternalsupportsystemisdividedintosupportaxialforceandcolumndisplacement.Thesupportbasicallybearspressure,buttherearealsoeccentricloadsandlateralforces(suchasupperconstructionloads),andexcessivebendingorlateraldeformationofthesupportmaycauseinstabilityofthesupport.Ontheotherhand,thecalculatedsupportaxialforceisatheoreticalvalue.Inpracticalengineering,itisdifficulttoaccuratelyanalyzetheadditionalinternalforcescausedbytemperatureeffects,constructiondeviations,etc.Throughmonitoring,theactualstressstatusofthesupportcanbeunderstood.4.支撐體系4.Supportsystem（2）外拉錨體系

Externalanchorsystem外拉錨體系包括兩類，一類是錨桿支護，主要是監(jiān)測錨桿軸力；另一類是頂部外拉錨，這種坑頂外拉錨的受力特點是依靠錨碇（樁）前的土體，因此監(jiān)測錨碇（樁）的位移就顯得十分重要。Theexternalanchorsystemincludestwotypes:oneisanchorrodsupport,whichmainlymonitorstheaxialforceoftheanchorrod;Anothertypeisthetopexternalanchor,whichreliesonthesoilinfrontoftheanchor(pile)foritsstresscharacteristics.Therefore,monitoringthedisplacementoftheanchor(pile)isveryimportant.4.支撐體系4.Supportsystem（1）地下水位監(jiān)測

Groundwaterlevelmonitoring地下水是影響基坑安全的一個重要因素。降低地下水位一般或多或少會造成周邊地表沉降、臨近管線或房屋下沉等影響。在采用止水帷幕的工程中，也有可能因為帷幕施工質量問題而發(fā)生滲漏，或者因為帷幕埋深不足而發(fā)生繞滲。滲流的后果往往會引起土層的顆粒被帶走，造成坑外水、土流失。降水和水、土流失對周圍環(huán)境的沉降影響范圍較大，有時可達到數(shù)倍基坑開挖深度以外。進行地下水位監(jiān)測可以預報地下水位不正常下降，控制地下水位變化，防止周邊地表沉降。此外，承壓水在深基坑中往往會造成基底突涌，因此承壓水的監(jiān)測也是一項重要內容。Groundwaterisanimportantfactoraffectingthesafetyoffoundationpits.Loweringthegroundwaterlevelgenerallycausesmoreorlesssurfacesubsidenceinthesurroundingarea,aswellassubsidenceofadjacentpipelinesorhouses.Inprojectsthatusewaterproofcurtains,itisalsopossibleforleakagetooccurduetoqualityissuesincurtainconstruction,orforleakagetooccurduetoinsufficientburialdepthofthecurtain.Theconsequencesofseepageoftencausetheparticlesinthesoillayertobecarriedaway,resultinginwaterandsoillossoutsidethepit.Precipitationandwaterandsoilerosionhaveasignificantimpactonthesettlementofthesurroundingenvironment,sometimesreachingseveraltimestheexcavationdepthofthefoundationpit.Monitoringgroundwaterlevelscanpredictabnormaldropsingroundwaterlevels,controlchangesingroundwaterlevels,andpreventsurroundingsurfacesubsidence.Inaddition,confinedwateroftencausesbasementsurgeindeepexcavations,somonitoringofconfinedwaterisalsoanimportantaspect.5.周邊環(huán)境

5.Surroundingenvironment（2）地面沉降

Groundsettlement

地面沉降雖然不是直接對建筑物和地下管線進行測量，但它的測試方法簡便，可以根據(jù)理論預估的沉降分析規(guī)律，較全面地進行測點布置，以全面地了解基坑周圍地層的變形情況，有利于對建筑物和地下管線等進行監(jiān)測分析。

Althoughgroundsettlementisnotadirectmeasurementofbuildingsandundergroundpipelines,itisasimpletestmethodthatallowsforamorecomprehensivearrangementofmeasurementpointsbasedontheoreticallypredictedsettlementanalysislawstoprovideacomprehensiveunderstandingofthedeformationofthestrataaroundthepitandfacilitatemonitoringandanalysisofbuildingsandundergroundpipelinesetc.

5.周邊環(huán)境

5.Surroundingenvironment（3）土壓力

Soilpressure

目前水、土壓力理論計算值同實際水、土壓力值還存在一定差異，特別是水土壓力在不同土質、不同支護結構變形下的差異更難以確定，而水土壓力的分布是支護結構設計以及引起基坑支護結構實際內力和變形的關鍵技術因素，因此對圍護墻體內外側的水土壓力進行監(jiān)測能全面分析和掌握支護結構的受力情況。Atpresent,thereisacertaindifferencebetweenthetheoreticalcalculationofwaterandsoilpressureandtheactualwaterandsoilpressure,especiallythedifferenceofwaterandsoilpressureindifferentsoilqualityanddifferentsupportstructuredeformationismoredifficulttodetermine,andthedistributionofwaterandsoilpressureisakeytechnicalfactorinthedesignofthesupportstructureandtheactualinternalforceanddeformationcausedbythefoundationpitsupportstructure,therefore,themonitoringofwaterandsoilpressureinsideandoutsidetheenclosurewallcanfullyanalyseandgraspthesupportThemonitoringofthesoilandwaterpressureinsideandoutsidetheretainingwallcanthereforeprovideacomprehensiveanalysisa