POINTE DU HOC.

Transcription

1 POINTE DU HOC Jean-Louis Briaud - Texas A&M University

2 2 CREDITS American Battle Monument Commission Departement du Calvados Congressman Chet Edwards Professor Bob Warden, Professor Mark Everett, Texas A&M University Efforts have been made to give credits for illustrations and text obtained from other sources. If you find credit missing on this document, please contact us so we can address the issue. Jean-Louis Briaud - Texas A&M University

3 POINTE DU HOC 3 Jean-Louis Briaud - Texas A&M University

4 HEAVY BOMBARDEMENT OF POINTE DU HOC 4 25 APRIL MAY MAY JUNE JUNE JUNE

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6 CLIMBING THE CLIFFS AT LOCATIONS OF BOMB IMPACT 6 General Earl Rudder and 225 Rangers. Only 90 survived

7 POINTE DU HOC TODAY 7

8 Approximately 10 m of erosion since 1945 Average cliff erosion rate = m/yr 8

9 Maximum Wave Height (m) Sandown Bay in Isle of Wight south of UK (2003 ~ 2006) Maximum Wave Height Hmax (m) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month

10 10 Fluctuation of high and low tide level from April to September, 2006 at Pointe du Hoc Tide Levels Level (m) Maximum daily tide level 4 Minimum daily tide level Apr-06 1-May May Jun Jul Aug Sep-06 Date

11 Sketch cross section of the cliff and Observation Post 11

12 Drilling Rig 12

13 13 Silty Clay Fractured Limestone Very hard Sandstone

14 14 STRATIGRAPHY

15 General stratigraphy near Observation Post. 15

16 16 ELECTRICAL RESISTIVITY PROFILES

17 17 EFA - EROSION FUNCTION APPARATUS V WATER FLOW τ SOIL PISTON PUSHING AT RATE (mm/hr) τ (N/m 2 )

18 Silty Clay (surface soil) erosion function 50 mm/hr for 1 m/s or 438 m/yr 18

19 Rock erosion rates mm/hr at 3.6 m/s or 0.22 m/yr 19 Limestone Sandstone Marly limestone Velocity (m/sec) Shear stress (P a ) Erosion Rate (mm/hr)

20 Caverns below the Observation Post 20 Erosion of cliff base

21 CLIFF BASE EROSION 21

22 Overhang with separation of the rock block from the rock mass 22

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24 Rock block removal analysis 24

25 25 JUNE 2006 MARCH 2008

26 Required Wave Head (H wave ) to Move a Rock Block Wave Head (m) f=30 f= Rock Block Size (m)

27 FINITE ELEMENT MESH TO OBTAIN STRESSES IN ROCK NEAR CLIFF 27

28 Horizontal stress distribution in rock mass Maximum tensile stress = 1/10 th of intact rock tensile strength H o riz o n tal S tress D istrib u tio n 28 Co m p re ssio n 30 T e n sio n 25 E levatio n fro m S ea L evel (m ) m E ros ion 2m E ros ion 5 3m E ros ion 4m E ros ion 5m E ros ion Ho riz o n ta l S tre ss (kp a )

29 29 TENSILE STRENGTH TEST

30 30 AVERAGE TENSILE STRENGTH AND TEST RESULTS Sample (MPa) (kn/m 3 ) (%) (kn/m 3 ) s t g t w c g dry Limestone Sandstone Marly Limestone

31 CANTILEVER BEAM ANALYSIS 31 22m P L H s t s t P H L

32 Massive collapse about 300m west of the Observation Post Block length (cavern depth or cantilever length) is about 4 m 32

33 Proposed remediation to reopen the Observation Post 33

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