Value of Instrumentation Systems and Real-Time Monitoring: An Owner s Perspective

Transcription

1 Value of Instrumentation Systems and Real-Time Monitoring: An Owner s Perspective

2 FHWA NATIONAL GEOTECHNICAL PROGRAM

3 Why Geotechnical Instrumentation? Provide warning of impending failure Evaluate/verify critical design assumptions Protection of adjacent structures Control construction operations Provide data for remediation solutions Document geotechnical feature performance Advance state of knowledge

4 Why Automated Real-Time Monitoring? Immediate notification of potential issues and problems Cost effective for remote or difficult to access locations Allows for increased reading frequency No overhead for labor to read and reduce data Reduced data can be easily communicated to Stakeholders

5 Longwall Mining at I-79 and I-70 Washington, PA

6 Geotechnical Issues Longwall mining operations several hundred feet below I-70 and I-79 Far more costly to purchase coal supports (~$40 million) than to repair highway damage (~$2 million) Primary focus is automated, real-time monitoring with alarms for protection of driving public Significant surface subsidence affecting roads and structures Pavement subsidence and cracking Underpinning or abandonment of bridges Removal of overhead sign structures Monitor performance of box culverts

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13 I-70 Instrumentation Plan

14 Owner Benefits Monitoring of deformations and changes in highway conditions allowed PennDOT to make rational decisions on speed limits and temporary maintenance on I-70 and I-79 Alarms were triggered at when anticipated movements were exceeded Alarms automatically notified PennDOT personnel to the problem

15 I-235 over University Avenue Des Moines, IA

16 Geotechnical Issues Two stage widening of I-235 over University Avenue 20 ft approach embankment constructed over a soft silty clay (~ 46 ft thick) DOT wanted to eliminate bump at end of bridge and downdrag on piles from phase 1 construction New Technologies and Development of Specifications Objectives of Instrumentation Program Evaluate/verify beam theory design methodology Evaluate larger spacing between columns Column spacing 3.0 m LTP thickness 1.2 m Four (4) layers of geosynthetic reinforcement

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28 kpa kn/m3 * 8 m = 163 kpa 94.6 kpa 64.5 kpa PCB-3P PCB-2P 89.6 kpa PCB-1P kpa kpa Pressure Cell Results Research Section 20.4 kn/m3 * 8 m = 163 kpa kpa kpa m PCB-1R PCB-2R PCB-3R Pile #4 Pile #8 Pressure Cell Results Production Section 3.00m Pile #1 Pile #5

29 mm Settlement Results Research Section 100 mm mm 226 mm SGB-1P SGB-2P mm mm SGB-2R SGB-5R SGB-6R* 1.75m Pile #3 Pile #7 Settlement Results Production Section Pile #1 3.00m Pile #5 * SENSOR NOT WORKING

30 3.00m 3.00m Pile #1 S1-4(H,V) (H), 0.230(V) %Strain S1-2(H,V) 22 (H), 63 (V) lbs force S1-6(H,V) (H) Sensor Not Active (H), 0.230(V) %Strain (V) %Strain, -20 lbs 22 (H), 63 (V) lbs force Pile Cap (typ.) Pile #5 S1-1(H,V) (H), 0.576(V) %Strain 34 (H), 161 (V) lbs force S1-3(H,V) (H) Sensor Not Active (V) %Strain, 114 lbs S1-5(H,V) (H), 0.792(V) %Strain 8 (H), 209 (V) lbs force 0.60m Pile #2 S1-8(H,V) (H) %Strain, 104 lbs (V) Sensor Not Active S1-7(H,V) (H), 0.357(V) %Strain -239 (H), 103 (V) lbs force Pile #6 PLAN VIEW LEGEND: Strain Gauge On Geogrid RESEARCH SECTION Strain Gage Layout

31 Owner Benefits: IA DOT able to increase pile spacing for second phase of work (reduced number of piles by factor of 3) Total project savings of approximately $500,000 Allowed for evaluation of real-time data acquisition application Data for verification of numerical codes for design of CSE Better understanding of load transfer in beam system

32 I-15 Reconstruction Project - Salt Lake City, UT

33 Geotechnical Issues Large Primary Consolidation Settlement (3 to 5 ft) Time Rate of Consolidation (2 years to end of primary) Creep Settlement (Bump at Bridge) Foundation Stability (Large Embankments on Soft Soils) Schedule Constraints (two 2-year projects) Maintenance of Traffic (Had to be maintained) New Technologies and Development of Specifications

34 Settlement of Soft Clays in Salt Lake Valley Primary Settlement Secondary Settlement

35 Geofoam Light Weight Fill Lime Cement Columns Surcharging PV Drains 2-Stage MSE Walls

36 Geofoam Embankment Buried Utilities Geofoam Embankment from State St. to 200 W. Along Interstate I-80, Salt Lake City, Utah

37 Geofoam Array ROW OF SURVEY POINTS AT FACE OF WALL 25 MM - PVC STAND PIPE ROW OF SURVEY POINTS ALONG INSIDE EDGE OF MOMENT SLAB ROW OF SURVEY POINTS ALONG OUTSIDE EDGE OF EMERGENCY LAN CONCRETE PAVEMENT ROAD BASE LOAD DISTRIBUTION SLAB LEVEL 6 SQUARE PLATE WITH MAGNET RING 6.5 TO 7.3 m HEIGHT VARIES LEVEL 4 GEOFOAM BLOCKS LEVEL 2 GRANULAR BACKFILL LEVEL m BEDDING SAND VIBRATING WIRE TOTAL PRESSURE CELL

38 Geofoam Array Installation Pressure Cell in Base Sand Magnet Extensometer and Pressure Cell Installation Pressure Cell Cast in Bridge Abutment

39 Geofoam Magnet Extensometer Data Settlement (in.) st S Magnet Reed South Level 0 Level 1.5 Level 3.5 Level 5.5 Level 7.5 Level 8.5 Level 9 EC Jul-00 Jul-01 Jul-02 Jul-03 Jul-04 Jul-05 Jul-06

40 Geofoam Magnet Extensometer Data 0.0 Projected Geofoam Creep Time (days) Construction 10 Year 50 Year 0.5 Strain (%)

41 Geofoam Pressure Cell Measurements 11.0 Geofoam Pressure Cells Pressure (psi) Mar-99 Mar-00 Mar-01 Mar-02 Mar-03 Mar-04 Mar-05

42 Owner Benefits Geofoam fills are performing as expected with no major issues Performance monitoring led to the following conclusions: Approximately 1 percent vertical strain occurred during construction Approximately 0.3 percent creep strain (1.3 inches) has occurred in a 4-year post construction period Creep strain in a 10 year post-construction period is expected to be about.4 percent (about 1.7 inches) Instrumentation allowed for additional evaluation of the complex vertical stress distribution that develops in a geofoam wedge fill

43 Thank you! Contact Information: Silas Nichols, Senior Geotechnical Engineer Federal Highway Administration - Resource Center 61 Forsyth Street, SW Suite 17T26 Atlanta, GA Phone: Silas.Nichols@dot.gov Website: