Problems encountered in pipe jacking construction and their prevention

Categories:Technical Services
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Time of issue:2019-12-25 16:16
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(Summary description)Pipejackingconstructionisanundergroundpipelineconstructionmethoddevelopedaftershieldconstruction.Itdoesnotrequireexcavationofthesurfacelayer,andcanpassthroughroads,railways,rivers,groundbuildings,undergroundstructuresandvariousundergroundpipelines,etc.Itismoreandmorewidelyusedintheconstructionofpipelinessuchaswatersupplyanddrainage,gas,electricity,andcommunication.However,theconstructionequipment,technology,andmanagementlevelofthepipejackingconstructionunitareuneven,andsomeproblemsoftenoccurintheconstruction,whichaffecttheconstructionquality.Thisarticletakestheconstructionofpipejackingwithmud-waterbalancemethodasanexample,analyzestheproblemsandcausesoftenencounteredinpipejackingconstruction,andproposessomepreventionmeasures.1.Characteristicsandtechnologyofpipejackingconstruction1.Pipejackingconstructioncharacteristics(1)Duringtheconstructionofadvancedpipejacking,thereisnoneedtoclosetheroadforconstruction.Theselectedworkingwellsandreceivingwellsarelocatedinidleplaces,andthetrafficontheroadwillcontinuetoflowduringthejackingprocess.(2)Thereisnoneedforexcavation,backfillingandpavementrepair,socomparedwithlarge-scaleexcavationconstruction,itcanreducethetotalprojectcost.(3)Themud-watercirculationmethodconstructionavoidstheundesirablephenomenaofmud-wateroverflowandloosemudstacking,ensuringthatthenaturalenvironmentisnotpolluted,andenablingcivilizedconstruction.(4)Theadvancedpipejackingmethodisfullyautomaticandremotecontrol,andworkersarenotrequiredtoworkinthepipeline.Thisnotonlyeliminatestheheavymanuallaboroftheworkers,butalsoprovidessufficientguaranteeforthesafetyoftheworkers.(5)Duringtheadvancedpipejackingprocess,thediggingmachineandthepipesurroundingsarebetweentheactiveearthpressureandthepassiveearthpressure,sothereisverylittleinterferencetotheoriginalsoil,soitwillnotcauseroadsettlementorevencracks,andavoidroadrebuilding.2.PipejackingconstructiontechnologyPipejackingconstructiontechnologyisapipelinepavingtechnologythatdoesnotneedtoexcavatetheground.Ahydraulicjackwithlargethrustcanbeusedbehindthepipejackingmachinewithremotecontroldevice,sothatthetunnelingmachineandthepipelineimmediatelyafteritcanpassthroughthesoillayer.,Toreachthepre-designedposition,thisiscalledpipejackingproject.Theexcavationtakesplaceinfrontofthepipejackingmachine,andtheexcavatedmaterialisdischargedbyapumpthroughthemudcirculationsystemandreachesthesurface.Thebasicprincipleofpipejackingconstructionis:excavatetwofoundationpitwellsfromtheground,andthenplacethepipejointsfromtheworkingwell,andpushthepipejointstobereservedfromtheworkingwellthroughthejackingjackofthemainjackorthejackingmachineryintherelayroom.Passthroughthesoillayertoreachthereservedopeningofthereceivingwell,andthenpassthroughthereservedopeningofthereceivingwelltoformtheconstructionofthepipeline.Atpresent,thecommonlyusedconstructionmethodsforpipejackingaredividedintoopenmanualhand-dugandsealedmechanicalpipejackingmethods.Amongthem,thecommonlyusedconstructionmethodsformechanicalpipejackingincludemud-waterbalanceandearthpressurebalance.Commonlyusedpipematerialsforpipeconstructionincludeconcretepipe,steelpipe,andglasssandsteelpipe.Nowadays,themostcommonlyusedpipejackingconstructionmethodisthemud-waterbalancepipejackingconstructionmethod.Theconstructionprincipleis:thesoil,sand,andstonearebrokenbythecuttingandturningfunctionoftheguidehead.,Theslurryisplacedinacentrifugeforcentrifugaldewatering,andthenthedrysoilisunloadedtotheplacewherethesoilisremovedinthebucket,andtheseparatedwaterisreturnedtothewaterstoragetankforrepeatedrecycling.Themainequipmentusedintheconstructionisinformatizationandfullyautomatedmud-waterbalancepipejackingmachine.2.Frequentlyencounteredproblemsandpreventionmeasuresinpipejackingconstruction1.ExcessivedeviationofpipelineaxisThedeviationbetweenthejackingaxisofthepipelineandthedesignaxisistoolarge,causingthepipelinetobend,evencausingdamagetothepipesectionandleakageoftheinterface.　(1)Causeanalysis.①Thefrontalresistanceoftheformationisuneven,whichmakesthetooltubereceiveunevenforceandleadstodeviationofguidance.②Displacementorunevennessofthebackofthejackingpipemakestheresultantlineofjackingforcedeviate.　　③Thejacksarenotsynchronized,orthejack-to-jackjackingforcediffersgreatly,ortheinstallationaccuracyisinsufficient,resultingindeviationofthejackingforceresultantline.(2)Preventivemeasures.①Beforepipejackingconstruction,thegeologicalconditionsofthepipelinepassingareashouldbecarefullyinvestigated,andforcemeasuringdevicesshouldbeinstalledtoguidedeviationcorrection.Correctionshouldbecarriedoutinaccordancewiththeoperationmethodoffrequentmeasurement,frequentcorrection,andsmallamountcorrection.②Hydraulicjacksofthesamespecificationareusedtomakethejackingforce,strokeandspeedconsistent,andkeepthetotaljackingforcelinecoincidentwiththepipelinecenterline.③Strengthenthecontroloftheconstructionqualityofthebackofthejackingpipetoensurethatthebackdoesnotmove,andthebackshouldbeflattoensuretheinstallationaccuracyofthejackingequipment.④Thejackingcurveshouldbedrawnatanytimeduringthejackingprocessto

顶管施工中遇到的问题及防治

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Problems encountered in pipe jacking construction and their prevention

(Summary description)Pipejackingconstructionisanundergroundpipelineconstructionmethoddevelopedaftershieldconstruction.Itdoesnotrequireexcavationofthesurfacelayer,andcanpassthroughroads,railways,rivers,groundbuildings,undergroundstructuresandvariousundergroundpipelines,etc.Itismoreandmorewidelyusedintheconstructionofpipelinessuchaswatersupplyanddrainage,gas,electricity,andcommunication.However,theconstructionequipment,technology,andmanagementlevelofthepipejackingconstructionunitareuneven,andsomeproblemsoftenoccurintheconstruction,whichaffecttheconstructionquality.Thisarticletakestheconstructionofpipejackingwithmud-waterbalancemethodasanexample,analyzestheproblemsandcausesoftenencounteredinpipejackingconstruction,andproposessomepreventionmeasures.1.Characteristicsandtechnologyofpipejackingconstruction1.Pipejackingconstructioncharacteristics(1)Duringtheconstructionofadvancedpipejacking,thereisnoneedtoclosetheroadforconstruction.Theselectedworkingwellsandreceivingwellsarelocatedinidleplaces,andthetrafficontheroadwillcontinuetoflowduringthejackingprocess.(2)Thereisnoneedforexcavation,backfillingandpavementrepair,socomparedwithlarge-scaleexcavationconstruction,itcanreducethetotalprojectcost.(3)Themud-watercirculationmethodconstructionavoidstheundesirablephenomenaofmud-wateroverflowandloosemudstacking,ensuringthatthenaturalenvironmentisnotpolluted,andenablingcivilizedconstruction.(4)Theadvancedpipejackingmethodisfullyautomaticandremotecontrol,andworkersarenotrequiredtoworkinthepipeline.Thisnotonlyeliminatestheheavymanuallaboroftheworkers,butalsoprovidessufficientguaranteeforthesafetyoftheworkers.(5)Duringtheadvancedpipejackingprocess,thediggingmachineandthepipesurroundingsarebetweentheactiveearthpressureandthepassiveearthpressure,sothereisverylittleinterferencetotheoriginalsoil,soitwillnotcauseroadsettlementorevencracks,andavoidroadrebuilding.2.PipejackingconstructiontechnologyPipejackingconstructiontechnologyisapipelinepavingtechnologythatdoesnotneedtoexcavatetheground.Ahydraulicjackwithlargethrustcanbeusedbehindthepipejackingmachinewithremotecontroldevice,sothatthetunnelingmachineandthepipelineimmediatelyafteritcanpassthroughthesoillayer.,Toreachthepre-designedposition,thisiscalledpipejackingproject.Theexcavationtakesplaceinfrontofthepipejackingmachine,andtheexcavatedmaterialisdischargedbyapumpthroughthemudcirculationsystemandreachesthesurface.Thebasicprincipleofpipejackingconstructionis:excavatetwofoundationpitwellsfromtheground,andthenplacethepipejointsfromtheworkingwell,andpushthepipejointstobereservedfromtheworkingwellthroughthejackingjackofthemainjackorthejackingmachineryintherelayroom.Passthroughthesoillayertoreachthereservedopeningofthereceivingwell,andthenpassthroughthereservedopeningofthereceivingwelltoformtheconstructionofthepipeline.Atpresent,thecommonlyusedconstructionmethodsforpipejackingaredividedintoopenmanualhand-dugandsealedmechanicalpipejackingmethods.Amongthem,thecommonlyusedconstructionmethodsformechanicalpipejackingincludemud-waterbalanceandearthpressurebalance.Commonlyusedpipematerialsforpipeconstructionincludeconcretepipe,steelpipe,andglasssandsteelpipe.Nowadays,themostcommonlyusedpipejackingconstructionmethodisthemud-waterbalancepipejackingconstructionmethod.Theconstructionprincipleis:thesoil,sand,andstonearebrokenbythecuttingandturningfunctionoftheguidehead.,Theslurryisplacedinacentrifugeforcentrifugaldewatering,andthenthedrysoilisunloadedtotheplacewherethesoilisremovedinthebucket,andtheseparatedwaterisreturnedtothewaterstoragetankforrepeatedrecycling.Themainequipmentusedintheconstructionisinformatizationandfullyautomatedmud-waterbalancepipejackingmachine.2.Frequentlyencounteredproblemsandpreventionmeasuresinpipejackingconstruction1.ExcessivedeviationofpipelineaxisThedeviationbetweenthejackingaxisofthepipelineandthedesignaxisistoolarge,causingthepipelinetobend,evencausingdamagetothepipesectionandleakageoftheinterface.　(1)Causeanalysis.①Thefrontalresistanceoftheformationisuneven,whichmakesthetooltubereceiveunevenforceandleadstodeviationofguidance.②Displacementorunevennessofthebackofthejackingpipemakestheresultantlineofjackingforcedeviate.　　③Thejacksarenotsynchronized,orthejack-to-jackjackingforcediffersgreatly,ortheinstallationaccuracyisinsufficient,resultingindeviationofthejackingforceresultantline.(2)Preventivemeasures.①Beforepipejackingconstruction,thegeologicalconditionsofthepipelinepassingareashouldbecarefullyinvestigated,andforcemeasuringdevicesshouldbeinstalledtoguidedeviationcorrection.Correctionshouldbecarriedoutinaccordancewiththeoperationmethodoffrequentmeasurement,frequentcorrection,andsmallamountcorrection.②Hydraulicjacksofthesamespecificationareusedtomakethejackingforce,strokeandspeedconsistent,andkeepthetotaljackingforcelinecoincidentwiththepipelinecenterline.③Strengthenthecontroloftheconstructionqualityofthebackofthejackingpipetoensurethatthebackdoesnotmove,andthebackshouldbeflattoensuretheinstallationaccuracyofthejackingequipment.④Thejackingcurveshouldbedrawnatanytimeduringthejackingprocessto

Categories:Technical Services
Author:
Origin:
Time of issue:2019-12-25 16:16
Views:

Pipe jacking construction is an underground pipeline construction method developed after shield construction. It does not require excavation of the surface layer, and can pass through roads, railways, rivers, ground buildings, underground structures and various underground pipelines, etc. It is more and more widely used in the construction of pipelines such as water supply and drainage, gas, electricity, and communication. However, the construction equipment, technology, and management level of the pipe jacking construction unit are uneven, and some problems often occur in the construction, which affect the construction quality. This article takes the construction of pipe jacking with mud-water balance method as an example, analyzes the problems and causes often encountered in pipe jacking construction, and proposes some prevention measures. 1. Characteristics and technology of pipe jacking construction

1. Pipe jacking construction characteristics

(1) During the construction of advanced pipe jacking, there is no need to close the road for construction. The selected working wells and receiving wells are located in idle places, and the traffic on the road will continue to flow during the jacking process.

(2) There is no need for excavation, backfilling and pavement repair, so compared with large-scale excavation construction, it can reduce the total project cost.

(3) The mud-water circulation method construction avoids the undesirable phenomena of mud-water overflow and loose mud stacking, ensuring that the natural environment is not polluted, and enabling civilized construction.

(4) The advanced pipe jacking method is fully automatic and remote control, and workers are not required to work in the pipeline. This not only eliminates the heavy manual labor of the workers, but also provides sufficient guarantee for the safety of the workers.

(5) During the advanced pipe jacking process, the digging machine and the pipe surroundings are between the active earth pressure and the passive earth pressure, so there is very little interference to the original soil, so it will not cause road settlement or even cracks, and avoid road rebuilding.

2. Pipe jacking construction technology

Pipe jacking construction technology is a pipeline paving technology that does not need to excavate the ground. A hydraulic jack with large thrust can be used behind the pipe jacking machine with remote control device, so that the tunneling machine and the pipeline immediately after it can pass through the soil layer. , To reach the pre-designed position, this is called pipe jacking project. The excavation takes place in front of the pipe jacking machine, and the excavated material is discharged by a pump through the mud circulation system and reaches the surface. The basic principle of pipe jacking construction is: excavate two foundation pit wells from the ground, and then place the pipe joints from the working well, and push the pipe joints to be reserved from the working well through the jacking jack of the main jack or the jacking machinery in the relay room. Pass through the soil layer to reach the reserved opening of the receiving well, and then pass through the reserved opening of the receiving well to form the construction of the pipeline.

At present, the commonly used construction methods for pipe jacking are divided into open manual hand-dug and sealed mechanical pipe jacking methods. Among them, the commonly used construction methods for mechanical pipe jacking include mud-water balance and earth pressure balance. Commonly used pipe materials for pipe construction include concrete pipe, steel pipe, and glass sand steel pipe.

Nowadays, the most commonly used pipe jacking construction method is the mud-water balance pipe jacking construction method. The construction principle is: the soil, sand, and stone are broken by the cutting and turning function of the guide head. , The slurry is placed in a centrifuge for centrifugal dewatering, and then the dry soil is unloaded to the place where the soil is removed in the bucket, and the separated water is returned to the water storage tank for repeated recycling. The main equipment used in the construction is informatization and fully automated mud-water balance pipe jacking machine.

2. Frequently encountered problems and prevention measures in pipe jacking construction

1. Excessive deviation of pipeline axis

The deviation between the jacking axis of the pipeline and the design axis is too large, causing the pipeline to bend, even causing damage to the pipe section and leakage of the interface.

　(1) Cause analysis.

①The frontal resistance of the formation is uneven, which makes the tool tube receive uneven force and leads to deviation of guidance.

② Displacement or unevenness of the back of the jacking pipe makes the resultant line of jacking force deviate.

　　③The jacks are not synchronized, or the jack-to-jack jacking force differs greatly, or the installation accuracy is insufficient, resulting in deviation of the jacking force resultant line.

(2) Preventive measures.

①Before pipe jacking construction, the geological conditions of the pipeline passing area should be carefully investigated, and force measuring devices should be installed to guide deviation correction. Correction should be carried out in accordance with the operation method of frequent measurement, frequent correction, and small amount correction.

②Hydraulic jacks of the same specification are used to make the jacking force, stroke and speed consistent, and keep the total jacking force line coincident with the pipeline center line.

③Strengthen the control of the construction quality of the back of the jacking pipe to ensure that the back does not move, and the back should be flat to ensure the installation accuracy of the jacking equipment.

④ The jacking curve should be drawn at any time during the jacking process to guide the jacking correction work.

2. Land subsidence and uplift

During or after pipe jacking construction, ground subsidence or swelling occurs within a certain range on both sides of the pipeline axis, which affects the buildings around the pipeline, road traffic and public facilities such as the pipeline, and even endangers normal use and safety.

　(1) Cause analysis.

① Settlement and uplift caused by the imbalance of earth pressure on the front of the roadheader. From the principle of the earth pressure balance roadheader, when the roadheader passes through sufficient cutting and mixing, a soil body with greater plasticity and fluidity is formed in the soil silo. When the frontal earth pressure is controlled between the passive earth pressure and the active earth pressure, the ground will sink or rise. In fact, due to the large changes in soil quality, there are often large differences in the control based on theoretical calculations, which can not be accurately grasped, resulting in soil pressure imbalance and settlement. In addition, because some earth pressure balance roadheaders have insufficient adaptability to the soil, such as the cutting area of the cutter head is too small, the advancing speed or the speed of the screw conveyor cannot be adjusted, which makes the control of the earth pressure unfavorable or inconvenient, resulting in instability of the earth pressure and settlement. And bulge.

② Settlement and swelling caused by the gaps in the outer circumference of the pipeline. The voids on the periphery of the pipeline are caused by the roadheader's deviation correction or curve advancement, because the cross-sectional area of the pipeline formed during the deviation correction and curve advancement is larger than the pipeline cross-section, and the voids are filled by the surrounding soil and cause settlement. Nowadays, thixotropic mud anti-friction technology is generally used for pipe jacking. The outer diameter of the roadheader is 2 to 3mm larger than the outer diameter of the pipe in order to form a slurry sleeve. If the grouting is not timely, it will cause settlement.

③ Settlement and uplift caused by friction between the pipeline and the surrounding soil. There is friction between the pipeline and the surrounding soil when it is pushed. This friction often causes the soil to be sheared and disturbed, causing the soil to move and cause the ground to settle. In the case of irregular pipe joints, uneven joints or irregular pipes, this shear disturbance will be aggravated, increasing ground subsidence and uplift.

④ Settlement and uplift caused by leakage of pipe joints. When the sealing ring of the pipe joint is improperly placed or the pipe end is damaged by uneven force, and the pipe joint is excessively bent and the sealing is not good, it is more likely that joint leakage will occur, and the water and soil will be lost. This kind of soil loss will inevitably cause the ground. Settlement and uplift. In addition, the leakage of pipe joints also causes the loss of thixotropic mud, and the effect of supporting the soil and reducing friction is greatly reduced. It may also cause the settlement and uplift of the above two reasons.

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Problems encountered in pipe jacking construction and their prevention

顶管施工中遇到的问题及防治

Problems encountered in pipe jacking construction and their prevention