2.2 Rock Deformation And Defects Flashcards
What is a Crustal Deformation?
Rock deposits deformed due to earth processes
What are the types of Crustal Deformation
Tectonic movement - Gradual and rapid (rupture earthquake)
Plutonic deposits and volcanic
Change in loading (gravity effects)
What are the different stresses rock deposits under go? (Crustal deformation)
Compressive, tensional, shearing forces
What are the DUCTILE crustal deformation?
Folding, stretching and thinning, shearing
What are the BRITTLE Crustal Deformation?
Faulting
What is folding affected by?
Temperature, pressure, strain rate, rock type
What are the types of fold structures?
Monocline, Syncline, Anticline
Describe the monocline structure
Step like
Describe the Syncline structure
Trough (sag curve)
Describe the Anticline structure
Crest curve
What is bedding?
Interface where each rock layer meets
Engineering aspects of direction of bedding
Stability of structures and slopes
Movement of water
Tunnels and underground structures
What should the orientation of the ground (sedimentary rock) be for a DAM?
Undisturbed - horizontal
Perpendicular
NOT in line with the resultant force of damn and water pressure
What Engineering Aspects on fold structures in TUNNELS
Consider the heterogeneous forces being applied at all times
Different depths into the hill may have different conditions (anticline, Syncline)
What are the types of defects?
Planar, zonal
Classification (covered later)
What are the planar defects?
Fracture and joints, cleavage, bedding, lithologic boundaries
What is cleavage?
Foliation in metamorphic rock depositions
(Foliation: splitting into thin sheets)
What is Bedding?
Layering of sedimentary rocks deposits
What are Lithologic boundaries?
Interface between rock deposits
What are joints?
Fractures developed with no displacement
How are tectonic joints formed?
Formed by deformation of rock due to tectonic stress
Within folds, tensile folds and develops slowly overtime
What are the types of joints?
Hydraulic, sheeting/unloading and cooling
How are hydraulic joints formed?
Due to the increase pressure of water within deposits
How are sheeting/unloading joints formed?
Reduction of load
How are cooling joints formed?
Developed during cooling of IGNEOUS rocks
What does Bedding represent?
Change in deposition environment
Layers of sedimentary rock with different characteristics are what?
Bedding
What does the direction of defects affect?
Stability of slope, Tunnels and underground structures
What are the types of zonal defects?
Crushed seam, sheared zone, infill, voids/cavities
What are defects the result of ?
Movement
How are faults developed?
Due to relative movement through deposits, i.e tectonic activity propagates through material
What are the classifications of faults?
Strike slip, normal, reverse, thrust, oblique
What is a strike-slip fault?
Shearing response due to tectonic forces, Horizontal movement in strike of fault plane, no vertical movement
What is a normal fault?
Extensional response due to tectonic forces, horizontal movement perpendicular to strike of fault plane, vertical movement - hanging in dip direction
What is a reverse fault?
Compressional response due to tectonic forces, horizontal movement perpendicular to strike of fault plane, vertical movement - hanging wall opposite to dip direction
What are voids/cavities influence on strength?
Loss of capacity when present
What are the potential engineering aspects of deformation and defects?
Strength, Stability, Water movement, and gradual or rapid movement
