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Lesson 7 & 8Construction Inspection/ Quality Control (QA/QC)
schnabel-eng.com
Load Testing
Learning Outcomes
Identify proper approaches to inspect, monitor and document construction and testing of micropile systemsUnderstand the various load testing andUnderstand the various load testing and interpretation methods for micropiles
Quality Assurance and Quality Control (QA/QC)
Critical importancePlans and specification development stage through final construction
Implementation of all requirementsImplementation of all requirementsEnforcement of qualificationsSubmittal reviewsInstallation
2
Quality Control
Build the production piles like the test piles !Experienced drillers and inspectorsDocument test pile and production pile installation :installation :
drill depth & similar soilgrouted lengthgrout pressure & volumeproblems
Contractor Submittal Requirements
Contractor and employee qualificationsMaterials anticipated to be drilledPerformance criteriaLocation and orientation of the micropiles andLocation and orientation of the micropiles and tolerancesMicropile size and configuration
Contractor Submittal Requirements
Micropile capacityDrilling and grouting equipmentAnticipated equipment loads on structure or adjacent groundadjacent groundGeneral installation planGrout mix design and pressures
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Contractor Submittal Requirements
Reinforcement including size, configuration and corrosion protectionPostgrouting methods (if applicable)Documentation and protection of existingDocumentation and protection of existing utilities and environmentPlans to accommodate low headroom or obstructions
Contractor Submittal Requirements
Testing criteriaTesting and monitoring devicesDetails of connections to existing structuresCriteria for implementing remedial proceduresCriteria for implementing remedial proceduresSpoils handling
Material Handling and Storage
GroutCement
prevent hydration, keep dry, avoid moistureavoid overcompaction by overstackingperform visual inspections (lumps and foreignperform visual inspections (lumps and foreign matter)
Admixturessame as cementcheck shelf life, manufacturer’s recommendations
Waterpotableno impurities
4
Material Handling and Storage
Reinforcing SteelStore in a protected locationInspect steel when delivered pto siteReject steel that exhibits flaky corrosion or pittingExtra care with corrugated protected/epoxy-coated bars
Construction Monitoring
DrillingMinimize ground lossPrevent borehole collapseRemove casing so the reinforcement is not disturbed, damaged or in contact with the soilKeep hole full of grout to minimize hole collapseKeep fluid level in hole above external groundwater level to maintain balance of pressures
Construction Monitoring
Drilling (cont.)Schedule drilling, reinforcement installation and grouting to suit ground conditions (keep process continuous)Plug or cover holes, project casing above the head elevationProvide for proper disposal and containment of the drilling spoilsEnsure tolerances are met
5
Construction Monitoring
Grouting – Mixing and PumpingEnsure continuous grout placementEnsure cement is colloidally mixed and grout is continuously agitatedis continuously agitatedPrevent presence of air in the grout linesDo not draw down the level of grout in the agitation tank below the crown of the exit pipeEnsure exclusion of foreign matter during grout placement
Construction Monitoring
Grouting – Mixing and PumpingFluid tests to confirm proper batching (in real time)Cubes for strength testing (retrospective)Cubes for strength testing (retrospective)
QA/QC via Fluid Grout Tests
6
Use of Cubes as a QA/QC Tool
Construction Monitoring
Grouting – PlacementPrevent heaving or ground distressPrevent soil in bottom of hole from blowing inGrout as soon as possible after drilling the bond zoneUse tremie to ensure complete filling of holeTie tremie tube loose enough for removal during/or after tremie grouting
Construction Monitoring
Grouting – Placement (cont.)Observe suitable grout returnMaintain a positive head at the grout holding tankM t l t th i t fMeasure grout pressures close to the point of injection to account for line lossesMonitor grout pressures and volumes throughout both tremie grouting and pressure grouting (if used) processesTypical postgrouting pressures are 2 to 4 MPa
safety issue
7
Manual Monitoring of Pressure(Type B Micropile)
Construction Monitoring
Installation of ReinforcementInstall either before or after initial grout placement but before temporary casing (if used) is withdrawnRecord the total pile length and bond zone lengthInsert to the prescribed length without the use of forceDo not damage corrosion protection or centralizers during installation
Construction Monitoring
Installation of Reinforcement (cont.)Ensure reinforcement is clean of any surface soil, oil, mud etc.Check attachment and intervals (typically 2.5 ( yp yto 3 meters) of centralizers and spacersCenter reinforcement in boreholeEnsure full engagement of successive bar or pipe sections
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QA/QC Documentation
Pile Load Testing Ultimate and Verification load testingProof load testing
Verifing:design capacitydesign capacity construction processes
Check pile load test setup with the approved working drawingsPerform pile load testing in accordance with the project specifications
Testing Specifications
Number of “sacrificial” piles to be tested (Ultimate vs. Verification)Number of production piles to be testedMagnitude of test loadMagnitude of test loadMethod of load application
Testing Specifications
Duration of load hold steps (especially for extended creep testing)Acceptance criteria (load, movement, creep)Load test set up instrumentation andLoad test set up, instrumentation and measurement
7-25
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Load Testing RequirementsDetermining Factors
Number of production pilesMagnitude and type of loadingSensitivity of structure / consequences of failureGeotechnical conditions and variabilityAccess / headroom / constructability restraintsEngineer / Contractor experienceFactors of Safety
COST7-26
Development of Verification Load Testing Program
Perform load testing in proximity to a soil boringReview critical load combinations for load testingtesting
7-27
Acceptance Criteria
For Verification TestCriteria 1:
Rate of Pile Head Movement at the Test LoadCriteria 2:
Total Pile Head Movement at the Design Load
7-28
Total Pile Head Movement at the Design LoadCriteria 3:
Total Pile Head Movement Under Sustained Load (Creep)
10
Typical Compression Test Set Up
7-29
Set Up – Lateral Test
Lateral Load Test Arrangement (ASTM 3966-90)
Lateral Load Test Setup
Courtesy: Nicholson
11
Total Movement – Cyclic Test(e.g. Ultimate or Verification Test on Sacrificial Pile)
Pile top displacement vs. pile load curve
Partitioning of Cyclic Pile Test Data into Elastic and Permanent Components
Pile top elastic/permanent displacement vs. pile load curve
“Strange Results” or Failure
Clarify possible reasons for “strange results” or failure in real time
Options following failureOptions following failureModify design of individual pileModify constructionReduce unit load requirements/increase number of pilesAdditional testing
12
QA/QC Documentation
Production PilesComprehensive records
basis of payment deviations in future pile performance
Micropile installation logsGrout production and consumption recordsCompressive strength testing of grout samples
(AASHTO T106/ASTM C-109)Specific Gravity measurements of grout w/BaroidMud Balance Test
Typical Micropile Installation Log
Data Management - Micropiles
13
Data Management - Micropiles
Maintaining Good Photographic Records in Real Time
Learning Outcomes
Key elements to be evaluated during constructionFactors that affect development of a load testing programtesting program
14
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