Centrifuge Testing to Evaluate Seismic Soil Structure Interaction and Lateral Earth Pressures Near Buried Water Reservoir Structures in Southern California

Miguel FriasDr. Shideh Dashti, Ph.D.Department of Geological EngineeringUniversity of Wisconsin-Madison

What do you think of when you hear the following three places: San Francisco, Tokyo, Istanbul?

?

Big

Large Cities

Engineering

Very Popula

ted

Lots of People

Modern

Why care?“You have to build in a way that allows the earthquake energy to be absorbed. Our objective as engineers is to increase the absorption” Professor Oral, PhD Civil and Environmental Engineering, MIT

Backgroundhttp://www.ladwpnews.com/external/content/document/1475/1333039/1/Headworks%20Fact%20Sheet%202012.pdf

Objective Evaluate the reliability of

different types of pressure sensing technologies in capturing lateral earth pressures imposed by the backfill of Nevada Sand.

Centrifuge Box Modifications

Strain Gauges

Strain Gage # 1-16

Sand Side (orange)

No Sand (orange/white)

Both (blue)

1 122 Ω 120 Ω 240 Ω2 120 Ω 120 Ω 240 Ω7 120 Ω 121 Ω 240Ω8 121 Ω 121 Ω 240 Ω15 120 Ω 120 Ω 240 Ω16 ? ? ?

• Measure bending moment distributions acting on retaining wall

• Resistance range between 118-123 ohms

Pressure SensorsPressure Sensor

Input Test Ω

Expected Input Test Ω

Output Test Ω

Expected Output Test Ω

1 230 223 2611 2609

2 231 219 2921 2911

3 222 219 2622 2605

4 230 225 2925 2924

5 228 217 2664 2654

6 234 220 3126 3027

7 230 217 3025 3004

8 228 216 2980 2972

9 237 225 3080 3074

10 231 201 3060 298811 303 287 3570 3548

13 305 289 3910 3853

15 304 284 4230 4212

Measure total amount of pressure distributed along sand face wall

Pressure sensors 12, 14, and 16 not included

Volt meter measured resistance higher than expected

Sieve Analysis

Specific Gravity TestObject Mass (g)Filter .5Filter + Sand 60.5 Empty dry 500 mL volumetric flask 180.2 Flask + Sand from filter 240.3 Flask with water + sand after de-airing process

715.3

Flask with water up calibration mark (water only)

677.9

Calculation: Gs= Ws/Ws+Wfw-WfwsWhere…Weight of the soil (Ws)Weight of the flask + water (Wfw) Weight of flask + water+ soil (Wfws)

*Gs=60g/60g+677.9g-715.3g = 2.65 %

Specific Gravity, Gs, of various soil typesSand 2.63-2.67Silt 2.65-2.7Clay & Silty Clay

2.67-2.9

Organic Soils

<2.0

Pluviation TestingOur Densities:40% at .50m60% at 1.0m80% at 1.45m

What’s Next?

• Spinning• Analyze Final

Results

Acknowledgements Shideh Dashti, PhD Min Zang, PhD SMART Program University of Colorado University of Wisconsin-Madison

Thank You