The San Jacinto Monument Case History - CEProfs Jacinto Monument Lecture... · The San Jacinto Monument Case History ... of the study I talked to several people who had helpful comments

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Jean-Louis Briaud – Texas A&M University

The San Jacinto Monument Case History

Picture obtained from http://www.laanba.net/photoblog/ January05/sanjacinto.jpg

Jean-Louis BRIAUD, PhD, P.E.Professor and Holder of the Buchanan Chair

TEXAS A&M UNIVERSITY

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First of all, I wish to thank two of my PhD students: Jennifer Nicks and Keunyoung Rhee who made most of the calculations. I also wish to thank Fugro for sharing this very valuable data; in particular Phillip King, Greg Stieben, John Juenger, and Joe Cibor. This study was sponsored by the Buchanan Chair at Texas A&M University. During the course of the study I talked to several people who had helpful comments. I wish to thank Ralph Peck, Ken Tand, Ed Ulrich, John Focht, Carl Fenske, Roy Olson, Wayne Dunlap, and Steve Wright for their input. The Monument and this unique geotechnical data are part of our State Heritage and part of Texas geotechnical history and I suggest that the proper place for this data is in the museum at the base of the Monument. I am very happy to see that the University of Texas, Fugro, Texas A&M University and many others have in essence cooperated in various ways to generate, safeguard, and enhance this precious data. I also wish to recognize the vision of Raymond Dawson who helped our profession by instrumenting a major structure. We hope that such vision can be carried on by newer generations. The pay off may not be immediate but it is often very valuable……………………………………………………………………….

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• History• Structural Dimensions• Construction• Loading• Soil Borings & Stratigraphy• Soil Properties• Increase in Stress• Depth of Influence• Settlement Calculations• Settlement Observations• Discussion• Conclusions

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History

• March 2, 1836: Independence declared• March 6, 1836: The Battle of The Alamo • April 21, 1836: The Battle of San Jacinto

– Led by General Sam Houston, the Texan Army overwhelmingly defeated the Mexican Army led by General Santa Anna

– Ensured Texas’ independence from Mexico– Considered by some historians as the sixteenth most

decisive battle in world history

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History

– Alfred C. FinnArchitect

– Robert C. CumminsStructural Engineer

– Raymond F. DawsonGeotechnical Consultant

Picture of Alfred Finn obtained from SloaneGallery.comPicture of Robert Cummins obtained from (Cummins, 1944)Picture of Raymond Dawson provided by Steve Wright, UT (2005)

1936: For the Centennial of the Battle of San Jacinto, Texas and the United States government decided to erect a memorial on the battlegrounds to honor the victory:

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From the Air

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SAN JACINTO MONUMENTHOUSTON (1936)

WASHINGTON MONUMENTWASHINGTON DC (1887)

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Structural Dimensions

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Construction

• Excavation began on September 19, 1936

• A 76.2 mm thick, 17.2 MPa compressive strength concrete slab was poured over leveled soil

• Construction on the foundation began on October 26, 1936 - 4587 m3 of concrete were poured

Reinforcement in the Foundation( Bullen, 1938)

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Construction

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Loading• Gross pressure = 224 kPa• Max pressure (dead + wind) = 273 kPa• Excavation = -83 kPa• Net pressure = 141 kPa• Net pressure after mat poured = 10 kPa• Pressure from Terraces = 34 kPa and 85 kPa

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Unknown date and locationMcClelland47.61Unknown (>1946)

Study of the movementsMcClelland2.1 to 6.131980

For new construction around the reflection poolMurillo Eng.3 to 12131976

For repairs to the MonumentGolemon & Rolfe4.5 to 6.181964

Likely used by Dawson for teaching purposesUnknown6111953

Location unknownUnknown44.211948

Location unknown, water wellUnknown198.211938

No. and location unknownLayne Texas6.111936

CommentsCompanyBoring Depth (m)

No. of BoringsBoring Date

Soil Borings

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Location of Soil Borings

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Stratigraphy

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Soil Index Properties

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Consolidation Characteristics

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Stress History

• Consolidation curves show preconsolidation pressures as high as 1000 kPa (Casagrande construction)

• Geologists estimate the maximum overburden at the site, however, was 4.6 m of the same clay found presently

• Joints and fissures within the Beaumont clay can lead to high internal pressures

• Pre-consolidation by desiccation seems to be a more reasonable explanation

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Modulus of Elasticity• A modulus, E, for the soil at the site was

determined by using several references:– University of Houston – O’Neill (2000)– Baytown Bridge – Little, Briaud (1988)– Downtown Houston – Williams, Focht (1978?)– Deer Park – Kenneth E. Tand & Associates in Houston– Consolidation data

Picture obtained from Google.com, 2005

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Modulus of Elasticity

• Using the elastic settlement equation,s = 0.88(1-ν2)pB/E

the Modulus (E) at the site was back-calculated to be 12.3 MPa based on the last known settlement observation (s) of 0.329 m. – ν = 0.35– p = 138.9 kPa (net pressure)– B = 37.8 m

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Modulus of Elasticity

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Stress Distributions

• Stress Distributions under the center of the foundation were found using ABAQUS.– Δσexc.– Δσmat (for both rigid and flexible

foundation)– Δσmnt.– Δσterraces (assumes it is flexible)

• It is recommended that the stress distribution due to the flexible foundation be used for this analysis.

18.9 m

37.2 m

55.5 m

2 B (B=37.8m)

2.5 B (B=37.8m)

ACE

OBD

ACE

OBD

18.9 m

37.2 m

55.5 m

2 B (B=37.8m)

2.5 B (B=37.8m)

ACE

OBD

ACE

OBD

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Stress Distributions

1 8 .9 m

3 7 .2 m

5 5 .5 m

2 B ( B = 3 7 . 8 m )

2 .5 B ( B = 3 7 . 8 m )

ACE

OBD

ACE

OBD

1 8 .9 m

3 7 .2 m

5 5 .5 m

2 B ( B = 3 7 . 8 m )

2 .5 B ( B = 3 7 . 8 m )

ACE

OBD

ACE

OBD

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Depth of Influence

• Two definitions for the depth of influence:– Depth at which the pressure has decreased to 10%

of the applied surface pressure– Depth at which the settlement is 10% of the

settlement at the surface• The zone of influence depends on which

definition is used and on the modulus profile of the soil

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Depth of Influence

Using Stress Criterion

Using Settlement Criterion

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Depth of Influence

Zi/B vs E1/E0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.001 0.01 0.1 1 10 100 1000

E1/E0

Z i/B

E=0.1Z+400

E=Z+350

E=3.13Z+250

E=12.5Z+150

E=25Z+100

E=37.5Z+50

E=75Z+10

E=150Z+3

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Dawson’s Predicted Settlement (1936)

Time (yr) Settlement (m) Settlement (%)

1 0.065 35

5 0.093 50

100 0.140 75

800 0.187 100

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2006 Calculations

• Cases:– 1: No water, no fill, no rebound from excavation– 2: No water, no fill, rebound from excavation– 3: Water at base of foundation, no fill, no rebound

from excavation– 4: Water at base of foundation, no fill, rebound from

excavation– 5: No water, added fill, no rebound from excavation– 6: No water, added fill, rebound from excavation– 7: Water at base of foundation, added fill, no

rebound from excavation– 8: Water at base of foundation, added fill,

rebound from excavation

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• Sub-Cases:– a - Using the void ratios from the

consolidation curves → Δe/(1+eo))*H

– b - Using the estimated σ'p and Cc,Cr• UNLOAD – Cr chosen as the slope of the rebound curve • LOAD - Cr chosen as the slope of the initial

recompression/loading on the consolidation curve

– c - Using σ'p from the consolidation curves and Cc,Cr• UNLOAD – Cr chosen as the slope of the rebound curve • LOAD - Cr chosen as the slope of the initial

recompression/loading on the consolidation curve

2006 Calculations

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Case 1• Assumptions:

– No water– No Fill– No Rebound from excavation

0.960.89c L0.280.13b L1.040.94c0.350.19b0.260.18as (m)s (m)Sub-Case

(FLEXIBLE Foundation)(RIGID Foundation)

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– No water– No Fill– Rebound from excavation



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– Water at base of foundation– No Fill– No rebound from excavation



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– Water at base of foundation– No Fill– Rebound from excavation



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– No water– Added Fill– No rebound



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– No water– Added Fill– Rebound from excavation



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– Water at base of foundation– Added Fill– No rebound



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– Water at base of foundation– Added Fill– Rebound from excavation



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Reference Points• Dawson established 50 reference points

around the foundation

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Benchmarks-6.7 m deep

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Actual Settlement

• Dawson established the elevations of the benchmarks and reference points on November 9, 1936 – two weeks after the base was poured → Net soil pressure = 10.4 kPa

• Dawson took 26 settlement readings between 1937 and 1966

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Actual Settlement

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Actual Settlement

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Actual Settlement

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Dawson’s Explanations

• Dawson had a few hypotheses concerning the divergence of his prediction and the actual settlement:– It might be due to secondary consolidation, but

highly unlikely as one would not expect the end of primary for several hundred years

– Another possibility is the vibrations resulting from pulsating winds during tropical storms – not enough data

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Subsidence

Picture obtained from www.ruf.rice.edu/ ~leeman/aNR.html

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Subsidence

• The areas that have the greatest groundwater extraction have subsided about 3 m.

• The rate of subsidence in the Houston area ranges from 31 to 76 millimeters per year.

• Assuming uniform subsidence around the San Jacinto Monument, the benchmarks and reference points would not see differential settlement.

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Equivalent Drainage Length

• Knowing the settlement vs. time curve, the drainage length for time rate of settlement calculations can be found by matching that curve.– Hdr ≈ 15 m

• Knowing Dawson’s predictions for time rate of settlement, the drainage length that he used can also be found by back-calculation.– Hdr = 10.2 m

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Settlement Curve

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Summary of Settlement

0.329Measured Settlement

0.187Dawson's Prediction

0.370Case 7a

0.607Case 8a

s (m)Description

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Conclusions• Stress increase with depth:

– For rigid mats, use flexible stress increase solutions. The soil redistributes the pressure in the long term.

– Go to a depth of 2B– Divide that depth in about 10 layers– Calculate the decrease in stress due to

excavation in each layer– Calculate the increase in stress due to the

mat in each layer– Calculate the increase in stress due to the

structure in each layer

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• Consolidation Testing:– Think about what the soil will go through in

the field.– Upon extrusion from the Shelby tube the

sample is unloaded. Consolidation tests start as reloading tests

– Apply loading up to the initial vertical stress, σ’

ov, for the sample– Unload the sample by an amount equal to the

pressure removed due to excavation– Reload the sample in steps up to at least σ’

ov+ Δσload

Conclusions

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Conclusions

• Settlement calculations:– Perform calculations for the center of

each layer– Use the void ratios from the

consolidation curves s = H Δe/(1+eo)– Calculate separately the rebound during

excavation, the settlement of the mat, the settlement of the structure.

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Conclusions• Settlement calculations:

– For long term settlement, E/su ≈ 250 or 123 ?. 123 more likely

– If available, use a 3-D numerical method to determine settlement. In this fashion, the stress increase and the stiffness profile are automatically taken care of.

– Which settlement is important? After the mat is poured, after a few floors, after completion of the structure? Should the recompression settlement be included?

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THANK YOU

http://http://ceprofs.civil.tamu.edu/briaudceprofs.civil.tamu.edu/briaud//

Documents

The San Jacinto Monument Case History - CEProfs Jacinto Monument Lecture... · The San Jacinto Monument Case History ... of the study I talked to several people who had helpful comments