Landslide Early Warning System

Wyatt Bartlett- UH ManoaJohn Nihi- UH Manoa

Melia Iwamoto - Graduate Student AdvisorPhillip Ooi - Faculty Advisor

UH Mānoa Geotechnical Engineering Lab

Overview1. Objectives

2. Project Locations

3. Field Instrumentation

4. Lab Methods

5. Results

6. Discussion of Findings

7. Summary & Conclusions

Objectives1. Soil Characterization

• Hydrometer (standard) vs. Laser Diffraction (new)

2. Suction Characterization• SWCC = w% vs. suction• Theoretical vs. Lab vs.

FieldCreate more accurate slope stability models for Hawaii DOT

Project Locations

Likelike Highway Pali Highway

Monitoring Instruments

• Inclinometer – Lateral Displacement• Tensiometer – Suction• Water content sensors – Water content• Rain gage - Precipitation

Datalogger

• Program collection frequency• Collects data remotely• Powered by solar energy

Lab Methods1. Grain Size Distribution

• Wet Sieve and Hydrometer (Conventional)

• Laser Diffraction (New and being studied)2. Soil Water Characteristic Curve

• Pressure Plate - Lab• VSA (Vapor Sorption Analyzer) - Lab• Tensiometers - Field• SoilVision - Theory

Grain Size DistributionHydrometer Laser DiffractionWet Sieve

4 days 15 minutes1 day

Suction in the LabPressure Plate Vapor Sorption Ana-

lyzer

Suction in the Field• Tensiometer to measure suction

Results - Grain Size Distribution

0.000010.00010.0010.010.11100

10

20

30

40

50

60

70

80

90

100

Wet Sieve and Hydrometer vs. Laser Diffraction

Horiba4 Hydrometer4

Diameter (mm)

%Pa

ssin

g

Discussion of FindingsHydrometer vs. Laser Diffraction

• Compared to Di Stefano, et al. (2010)

Di Stefano, C., et al. (2010) Comparison between grain-size analyses using laser diffraction and sedimentation methods. Biosystems Engineering 106 (2010) 205-215

Results - Suction

1 10 100 1000 10000 100000 10000000%

5%

10%

15%

20%

25%

30%

35%

40%

45%

50%

Soil Water Characteristic Curve

Soil Vision (B2-11)

Measured (Field MPS-6)

Measured (Lab - VSA)

Measured (Lab - PP)

Suction (kPa)

Gra

vim

etri

c W

ater

Con

tent

Summary and Conclusions

Grain Size Analysis• Laser diffraction provides a reasonable estimate of

the soil grain size distribution compared to wet sieve and hydrometer tests

Soil Water Characteristic Curve• Suction measurements in the lab matches well with

those in the field• They also match well with theoretical curves

These findings will be useful in development of the LEWS

Acknowledgements• Special thanks to:• NSF SEE 3 Program• Melia Iwamoto• Marica Ottorogram

• Phillip Ooi• Yogi Kwong Engineers• HDOT

Q & A

References• Di Stefano, C., et al. (2010) Comparison

between grain-size analyses using laser diffraction and sedimentation methods. Biosystems Engineering 106 (2010) 205-215

• Jotisankasa, A. and Vathananukij, H. (2008) Investigation of soil moisture characteristics of landslide-prone slopes in Thailand. International Conference on Management of Landslide Hazard in the Asia-Pacific Region