1. GEOLOGICAL STRUCTURES
Folds, Faults and Joints

2. Definition of Terms
Bedding Planes: The planes or surfaces which divide on bed from the other.
Dip: The dip of a bed in the angle between the bedding and the horizontal plane.
Strike: It may be defined as the direction of line formed by the intersection of bedding and horizontal plane.
Outcrop: The area of exposure of bed on the earth’s surface is called outcrop.

3. Definition of Terms
Stress: defined as a force applied over an area, and has the dimensions.
Shear: a stress that results from the opposition of forces that are not aligned.
Ductile deformation: when rocks bend or flow, like clay.
Brittle deformation: when a rock breaks.

4. Types of Stresses Compressive →☐← rocks are squeezed Tensile ←☐→
rocks are pulled apart
Shear ↑☐↓
rocks are sheared

5. Responses to Stress Folding
produced by compressive stress on ductile rocks
Joints and Faults produced by any type of stress on brittle rocks

6. FOLDS

7. Parts of Folds
Axial plane or Axial surface: is the plane or surface that divides the folds as symmetrical as possible.
Limbs or Flanks: the sides of a folder.
Crest: the highest point of a fold.
Trough: the lower portion of a fold.

8. Parts of Folds

9. Nomenclature of Folds
Monoclines: Folds in which horizontal or gently dipping beds are modified by simple step like bends.

10. Nomenclature of Folds
Anticline: In which the strata on opposite flanks dip towards the axis in other words the folds that concave upwards.

11. Nomenclature of Folds
Synclines: is a fold with younger layers closer to the center of the structure.

12. Nomenclature of Folds
Over turned Fold: The axial plane is inclined and both limbs dip in the same direction but usually at different angles.

13. FAULTS

14. Parts of Faults
Throw : the vertical component of the displacement between two originally adjacent points of the fault.
Hanging Wall: the block above the fault.
Foot Wall: the underlying block.
Heave: the horizontal component of displacement.
Hade: the angle of inclination to the vertical of the fault.

15. Parts of Faults

16. Types of Faults DIP-SLIP FAULTS
Best seen in cross-section view (vertical offsets)
Normal Faults - upper block slides down (tensional stress)
Reverse Faults - upper block is pushed up (compressional stress)

17. Types of Faults NORMAL FAULTS
In a normal fault the hanging wall is displaced downward relative to the footwall.

18. Types of Faults REVERSED FAULTS
In the reversed faults the hanging wall is displaced upwards relative to footwall.

19. Types of Faults STRIKE-SLIP FAULTS
Result from shear stresses - best seen in map view (horizontal offsets)
Right-lateral vs. left-lateral

20. Types of Faults
STRIKE-SLIP FAULTS

21. Active and Inactive Faults

22. Active and Inactive Faults

23. JOINTS

24. Joints
Joints are planes or surface which intersect rocks, but along which there has been no appreciable displacement parallel to the joint surface. When displacement parallel to the fracture is measureable, the fracture is known as a fault.
Joints result either from tension or shear stress acting on rock mass. Tension joints arise, for instance by drying and resultant shrinkage of sedimentary deposits, or igneous rocks by contraction and cooling. Shear joints may arise from compression of sedimentary or igneous rocks.

25. Examples of Folds

26. Examples of Faults

27. Examples of Joints

28. ENGINEERING SIGNIFICANCE
Because of their almost universal presence, joints are of engineering importance, especially in excavation operations. It is desire able for joints to be spaced closely enough to reduce secondary plugging and blasting requirement to a minimum, but not so closely spaced as to impair stability of excavation slopes or increase breakage in tunnels. Needless to say, the ideal conditions are seldom encountered. Joints oriented approximately at right angles to the working face present the most unfavorable conditions, whereas joints oriented approximately parallel to the working face greatly facilitate blasting operations and ensure a fairly even and smooth break parallel to the face. Joint offer channels for underground water circulation and in working below the ground water table may greatly increase water problems. They also may exert an important influence on weathering.

29. THANK YOU AND HAVE A NICE DAY!
JOHN
CARLO
MAGNAYE
NALUPA