Bilangan Pengunjung

Tuesday, March 2, 2010

Tahukah Anda Apa Itu kerja-kerja 'Geotechnical Instrumentation & Monitoring"?

1. Purpose of monitoring

Every instrument on a project should be selected and placed to assist in answering a specific question: if there is no question, there should be no instrumentation.. (Dunnicliff, 1999).
  • Maintain safe operational practices.
  • Provide advance notice of instability.
  • Provide additional geotechnical information regarding embankment behaviour.
  • Settlement profile – quantity of settlement, thickness of fill.
  • Surface settlement
  • Limit of permissible lateral movement
  • Ground water profile
  • Heave of excavation
  • Pore Water pressure
  • Vertical settlement at determination depth

1.1 Benefits

  • Safety and construction control
  • Observational method
  • Verification and provide legal protection
  • Measurement for claim

2. Parameter to be monitored

  • Vertical deformation / settlement or heave
  • Horizontal deformation
  • Pore water pressure and water table
  • Vertical settlement at determination depth

2.1 Measurements of deformation:

  • Excess pore water pressures in ground that will dissipate over time and cause movement.
  • Drawdown of groundwater that may cause movements over time.
  • Date of weathering, erosion or clogging to detect deterioration of materials from physical causes.
  • Change in forces, stresses or strains to detect unexpected loading.
  • Construction processes that likely effects on materials properties and hence future performance.

3. Planning for monitoring

  • Establish of datum for reference point
  • Trigger limits
  • Selection of instruments for its ranges sensitivities or accuracies.
  • Method of data collection, manual or automatic, real time or periodic?
  • Indication on the need for remedial actions.
  • Compare measured performance with predicted, performance to get differences.
  • Indicate for future performance

4. Planning of remedial action

  • Devise action for each hazard warning level and ensuring the necessary manpower, machinery and materials will be available.
  • Line of communication for emergency respond plan.
  • Review frequency of monitoring to suit the warning level.

5. Selection of instrumentation locations

  • Identify zones of influence. (high risk sites, catchments areas and topographical maps).
  • Where predicted behaviour is representative of behaviour as a whole.
  • Instrumentation based on cluster.
  • Plan for data continuity in case of damage.
  • Arrange locations at predicted and critical area.
  • Arrange locations to provide cross-checks or comparative behaviour.

6. Selection of Instrumentation System

  • Use simple type of instrumentation system that will enable the desired data to be obtained.
  • Reliability is the most important when the instrumentation project is located in remote area.
  • Consider the ease of data acquisition and processing.
  • Consider cost (processing, calibration, installation, maintenance, monitoring and data.
  • Cost of procuring, calibration, maintenance, installation, monitoring and data processing.
  • Good past performance record.
  • Environmental and operational condition.

7. Calibration and Installation

  • Calibration certificate which are traceable to the National Standards.
  • Installation and Method Statement to follow drawing, specification and manufacturer’s recommendation.
  • Plan installation schedule.
  • Checklist should be used.
  • Plan for field function test.
  • Prepare installation record sheets.
  • Plan simple numbering system for case of identification.
  • Plan installation schedule.
  • Plan protection from damage and vandalism.
  • Plan calibrations during services life.
  • - readout units
  • - embedded components
  • Plan maintenance.
  • - Readouts units
  • - Field terminals
  • - Embedded components

8. Data collection, processing and presentation

8.1 Data Collections

  • Recording factors that may influence measured data.
  • Frequency of monitoring
  • Visual observation of the behaviour, for correlation with measured data.
  • Record format, Logbook or Field Data Sheet.
  • Data screening, comparing the latest reading.
  • Alert the Engineer when the magnitude of data change exceed predetermined critical magnitude.
  • Lookout for damage of instruments.

8.2 Initial Readings

  • A minimum of two readings will be taken immediately after installation.
  • Initial values should be based on a minimum of two reading and repeatability satisfy the expected tolerance.
  • Daily readings should be taken daily until data are stable.

8.3 Data collection frequency

  • Should be related to the rate at which the reading are changing.
  • Relation to construction activity.

8.4 Data Processing and Presentation

  • Manually, reading to be recorded in the field data sheets. Contain previous readings for immediate comparisons.
  • Format for data processing and presentation.

8.5 Report

  • Reporting requirements, contents
  • Frequency of data submission
  • Submission date

9. Installation & Datasheet

  • Borehole Log
  • Settlement Marker
  • Settlement Gauge
  • Deep Levelling Datum
  • Standpipe Piezometer
  • Pneumatic Piezometer
  • Inclinometer

9.1 Borehole Log Record

9.2 Installation record of Road Settlement Marker

9.2.1 Spread Sheet Settlement Marker

9.2.3 Graph Settlement Marker

9.2.4 Installation of Settlement Marker

9.3 Installation Record Settlement Gauge

9.3.1 Spread Sheet Settlement Gauge

9.3.2 Graph Settlement Gauge

9.3.3 Installation of Road Settlement Gauge

9.4 Installation Record Deep Levelling Datum

9.5 Installation Record of Standpipe Piezometer

9.5.1 Spread Sheet Standpipe Piezometer

9.5.2 Graph Standpipe Piezometer

9.5.3 Installation of Standpipe Piezometer

9.6 Installation Record Pneumatic Piezometer

9.6.1 Spread Sheet Pneumatic Piezometer

9.6.2 Graph Pneumatic Piezometer

9.6.3 Installation of Pneumatic Piezometer

9.7 Installation Record Inclinometer

9.7.1 Spread Sheet Record Inclinometer

9.7.2 Graph Inclinometer

9.7.3 Installation of Inclinometer

10. Effective Monitoring Program

Action Levels and responses must be established
Data must be reliable.
Measurements must be taken with sufficient frequency to capture unexpected performance as earliest as possible.
Measurements must be evaluated in a timely manner.

Sumber dari : CSL(Soil CentralLab Sdn Bhd)

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