Mechanism of Sinkhole Formation Above the Retsof Salt Mine
POSTULATED SINKHOLE MECHANISMS
• Piping
• Dissolution
PIPING CONCEPT
• Rock Remained in Place• Rock Fractured• Water Flow Downward through Fractures• Glacial Sediment Piped through Fractures• Voids in Glacial Sediment• Periodic Collapse of Voids
INITIAL EVIDENCE OF PIPING
• Episodic Sinkhole Growth
• Glacial Sediment Deep in Rock
• Excessive Drop of Surface
DISSOLUTION CONCEPT
• Dissolution of Salt Below Rock
• Loss of Rock Support
• Drop of Rock and Glacial Sediment
DISSOLUTION EVIDENCE
• Abundant Soluble Material
• Seismicity Related to Rock Breakage
INVESTIGATION OBJECTIVES
• Assess Collapse of Rock
• Determine Soluble Material Thickness
• Determine Source of Sediment in Rock
• Assess Strength of Glacial Sediment
INVESTIGATION OF ROCK COLLAPSE
• Drilling Data
• Seismic – Reflection Surveys
• Correlation of Subsidence Data
2YS
11YW
SCALE IN FEET
4000
9448
9446 9428
9568
94069410
9416
94279407
9426
94179430A94329431
94199425
94189430
94209421
94099413
9404
942394229424
9433
940594119412
9415 9414
94049408
N
SCALE IN FEET0 300
SCALE IN METERS91
.
.
Rock SurfacePrior to 3/12/94
March 12, 1994
N
-0.1
-0.5
1.0
-0.1
Surface SubsidenceAs of 3/28/94
SCALE IN FEET0 300
SCALE IN METERS91
N
Rock SurfaceAfter 3/12/94 and Before
4/6/94 Sinkhole
0 500
152
SCALE IN FEET
SCALE IN METERS
N
Rock Surface Drop 3/12/94 – 4/6/94
0 500
152
SCALE IN FEET
SCALE IN METERS
N
Seismic Survey Results (3/22 – 3/23/94)
N
0 500
152
SCALE IN FEET
SCALE IN METERS
Surface SubsidenceAs of 4/6/94
SCALE IN FEET0 300
SCALE IN METERS91
N
Rock Surface After 4/6/94
Sinkhole Formed
0 500
152
SCALE IN FEET
SCALE IN METERS
N
Rock Surface Drop After 4/6/94 Sinkhole Formed
0 500
152
SCALE IN FEET
SCALE IN METERS
N
Surface SubsidenceAs of 4/14/94
0 500
152
SCALE IN FEET
SCALE IN METERS
N
Surface SubsidenceAs of 6/13 and 6/15/94
0 500
152
SCALE IN FEET
SCALE IN METERS
N
Seismic SurveyResults 7/6 – 7/10/94
=
400 8000600
400
200
-200
0
-400
-600
GENESEE VALLEYFILL
SCALE IN FEET
CARBONATES
SHALE
SYRACUSE SHALE &DOLOMITE
UNIT D
VERNONSHALE
MINEOPENING
YIELD-PILLARPANEL
WATER MOVEMENT
CARB O NA T E S
S H A L E
SY RA CUS E S H A L E &DO LO MI T E
VERNONS H A L E
UNIT D
MINEOPENING
YIELD-PILLARPANEL
= W A TE R MOVE MENT
G ENE S EE VA LLE YFI LL
SCALE IN FEET0 400 800
600
400
200
-200
0
-400
-600
G ENE S EE VA LL EYF ILL
CARB O NAT E S
S H A L E
SY RA CUS E S H A L E &DO LO MI T E
VERNONS H A L E
UNIT D
MINEOPENING
YIELD-PILLARPANEL
= W ATER MOVE MENT
SCALE IN FEET0 400 800
600
400
200
-200
0
-400
-600
POSTULATED SINKHOLE MECHANISMSPIPING CONCEPTINITIAL EVIDENCE OF PIPINGDISSOLUTION CONCEPTDISSOLUTION EVIDENCEINVESTIGATION OBJECTIVESINVESTIGATION OF ROCK COLLAPSE