Analysis of Dip and Strike
DIP AND STRIKE PROBLEM
Type – I : Date given – Amount and direction of true dip and apparent dip direction.
To determine – Amount of apparent dip.
Example : A bed of Shale is dipping maximum of 32o along S-E Find the amount of its inclination along S80° E.
Note: CI = 2.5 cm . Scale: 1 unit= 1 cm.
Graphical method
Procedure : Draw N-S and E-W lines. Let them intersect at O. Draw a vector circle (2.5 cm. ie. radius). Draw true dip directional line A along S-E. Draw a perpendicular to OA at O. It cuts the circle at B. Construct complementary angle to true to dip (90°-32°) =58° at B. It cust OA line at C. Draw a perpendicular to OA at C. It is true strike direction (TSD). Draw apparent dip direction to OA at O. It cuts TSD line at R. Draw perpendicular to OP at O. It cuts the circle at Q. Join QR measure angle LORQ and it is 26° .
Type-II : Data given -2 apparent dips, amount and direction.
To determine- True dip amount, direction.
Example: A bed of Sandstone dips 30o along N60° W and 38° along S 25°W.Determine its true dip and strike.
Scale: 1 unit= 1cm.
Procedure : Draw N-S and E-W lines. Let them intersects at O. Draw a vector circle O as its centre with radius (CI = 2.5) 2.5 cm. Draw OA along apparent dip direction S25° W (AD1). Draw a perpendicular to it at O. It intersects the circle at B. Construct complementary the given apparent dip (90°-38°) =60° at B. It OA at C. (CB). Similarly draw OP along apparent dip direction N 60° W (AD2). Draw a perpendicular to it at O.
It cuts the circle at Q. Construct complementary the given apparent dip (90°-38°)= 52° at Q. It cuts OP line at R.It forms the True strike direction (TSD). To determine angle for the direction of true dip, draw a perpendicular to TSD from O. It cuts the TSD line at X. OX is the direction of true dip. Measure angle LSOX. It is S 88° W. To determine the amount of true of true dip along OX deaw a perpendicular to it at O. It cuts the circle at Y. Join xy. Measure LOXY, It is 42°.
Type III:Data given –True dip amount & direction and Apparent dip amount.
To determine- Apparent dip directions.
Example : A coal seam is overlying Sandstone and has a maximum dip of 42° towards South. Two inclined tunnels are proposed on the upper bedding plane of Sandstone to have an inclination of 30°. Determine the directions of the tunnels.
Scale: 1 unit=1 cm.
Procedure: Draw N-S & E-W lines. Let them intersects at O. Draw the vector circle (2.5 cm. as radius).Draw the true dip directional line along OS. Draw a perpendicular to at O. It intersects the circle at P.Construct complementary angle of the true dip (90°-30°) =60° at P. It cuts OS line at Q. Draw perpendicular to OS at Q. It forms true strike direction (TSD). To Plot the direction of apparent dip, select ordinarily any suitable direction. Let us take OW.
Draw perpendicular to ON. It cuts the circle at X. Construct the complimentary angle of apparent dip (90°-30°) =60° at X. It cuts OW line at Y angle LOYX is 30°. With O as centre and OY as radius. Draw a Circle to cut TSD line at A and B. Join OA & OB. Measure angle LSOA and LSOB. They are S 55°W & S 55° E.
