# ENAC12005 Geology and Geomechanics

Document Sample

Show working in order to provide evidence of your detailed understanding of the problem, provide
complete hand-written calculations, sketches and explanations and/or complete details of Excel
working. CAD based solutions alone are not acceptable but may be provided as evidence of checking.

Assessment is based mainly in the evidence provided in answers of well structured ideas and detailed
understanding of concepts and procedures, correct results are only a minor requirement in
assessment.

Question 1

Levels were taken to prepare cross sections for road construction. Levels were obtained at the road
centerline, and at 20m left and right of the centerline. The following table shows the cross section
reduced levels obtained at two locations 20 metres apart, at Chainage 320.00m and at Chainage
340.00m.

Position             20m Left              Centreline        20m Right         Formation
Design RL

Ch. 320.00m           RL 29.95 m            RL 30.41 m        RL 33.46 m        RL 32.50 m
Ch. 340.00m           RL 30.28 m            RL 31.42 m        RL 31.57 m        RL 33.00 m

The design formation width is 10 metres, and the batter slopes are 1 vertical to 2 horizontal. The
formation design RL for each chainage is shown in the table.

(a) Compute the cross-section area of fill at Ch 320.00.

(b) Compute the cross-section area of fill at Ch 340.00.

(c) Calculate the volume of fill required between these two cross-sections.

Page 1 of 6
Question 2
2(a) A triangular area of land is defined by Stations with the following coordinates, compute the area
(in hectares) of the land enclosed by these points.

Station       Easting (m)       Northing (m)
P               330.00             360.00
Q               390.00             400.00
R               420.00             320.00

2(b) Reduced Levels shown on the 10 metre grid below indicate the existing surface level of an area
of land to be leveled with imported fill as a base for a carpark. A vertical retaining wall has been
built to retain the fill; the outside grid levels have been taken just inside the retaining walls.

If the average finished level of the fill is RL86.50 metres, calculate the volume of fill required.

Question 3
In your own words, and with the aid of sketches where appropriate,

(a) describe the ellipsoid, the geoid and the Earth centered Cartesian coordinate system used with
GPS

(b) explain why these different reference systems have developed, and how they relate to each
other, in particular explain how GPS data obtained in the field for engineering projects refers
to all three reference systems.

Page 2 of 6
Question 4
The diagrams following show pages 2, 3 and 4 from a Field Book that records a tape detail survey in
which detail is measured from a triangular control survey along lines AB, BC and CA.
The line AB has a magnetic bearing of 298o, the line BC has a bearing of 62o, and line CA has a bearing
of 179o.
Use data recorded in the field books to hand-draw a plan of the area at a scale of 1:1000. [Note: CAD
drawings will receive no marks for this question.]
The Field Books show directions to other stations (i.e. D, E, F and G). These need not be shown on the
drawing.

Page 3 of 6
Question 5
Prepare a curve set-out table (see Schofield p. 374) to give to a survey party which can use the table to set
out a circular curve using the ‘tangential angle’ method with a theodolite and a tape. The specifications for
the curve are as follows:

Curve radius R = 300 m
Peg interval = 20 m
IP Chainage = 3466.78 m
Curve lead in straight bearing = 30o00’00”
Curve exit straight bearing = 60o00’00”

Question 6
The following diagram shows a grid indicating the required alignment of columns in a building under
construction.
The building requires three columns with centres 9 metres apart in the North-South direction.
There are four columns with centres 9 metres apart in the East-West direction.

The ground slab of the building has been laid, and the positions of the centres of the corner columns at
p, q, r and s need to be marked on the slab (at the intersection of the grid lines shown) to provide 4
physical reference marks on the slab that will be used by the contractor to set out the position all other
columns.

Two survey control stations A and B are available, they have the following coordinates.
Coordinates of A: 397.76 E; 224.68 N
Coordinates of B: 429.34 E; 224.92 N

The reference marks are to set out with a total station and distances are to be checked with a steel
tape. Prepare a set-out table for project records showing:
 The deflection angles from the line AB to required marks p, q, r and s
 The distance from A to the required marks p, q, r and s
 The deflection angles from the line BA to required marks p, q, r and s
 The distance from B to the required marks p, q, r and s

B

A

218.000 N
p                                       q

209.000 N

s                                      r
200.000 N

400.000 E    409.000 E     418.000 E    427.000 E

Page 4 of 6
Question 7
(a) Discuss the role and responsibilities of the Mine Surveyor.

(b) Describe (with sketches) and compare methods of transferring bearings and coordinates from
the surface to depths in mines or tunnels.

Question 8
The following figure shows a survey conducted to transfer bearings from the surface to a tunnel using
two plumb wires hanging in two vertical shafts as references.

The coordinates of the wires on the surface at Station A and at Station B have been determined
accurately and checked. The coordinates are:
Station A: 1510.231E; 420.879N          (based on local coordinate datum)
Station B: 2243.035E; 428.396N
The floor of the tunnel is 35 metres below the ground surface. The ground surface between A and B is
relatively flat and the tunnel has a small grade. Measured distances are horizontal. Altitude correction
for this depth is approximately 1mm, and can be ignored for this project.

The tunnel was surveyed from the plumb wire at A and the Bearing for line AX could not be
determined accurately so it was estimated to be 151 degrees. This bearing was used to begin the
traverse from A to B within the tunnel. Using this procedure, the misclose at B is computed for the
underground portion of the traverse from the wire at A to the wire at B. Then the misclose is adjusted
to close on the wire at B, and the coordinates of X, Y and Z are adjusted accordingly so the bearing AX
can be determined more accurately.

The bearings and distances obtained for the initial traverse were:
Line                Bearing                 Distance (m)
AX      151o00’00”(Initial estimate)         230.000
XY               106  o00’00”                230.000
YZ                76o00’00”                  230.000
ZB                41o00’00”                  270.000

(a)     Using the coordinates of the plumb wire at A as a starting point, compute the coordinates of
Stations X, Y, Z and B from the traverse data.

(b)     Calculate the misclose to the plumb wire at Station B

(c)     Adjust the misclose at B to zero, and adjust the initial traverse coordinates of Stations X, Y and Z

(d)     From the adjusted coordinates for Station , determine the corrected bearing and distance for the
line AX.

Page 5 of 6
Question 9
Section 1.2 of Schofield outlines five ‘principles of surveying’. Write a basic explanation of each
principle, describe a short a practical example of how it may be applied in surveying, and indicate how
your study has contributed to your understanding of each principle and its application.

Question 10
Investigate mass methods or use of digital technologies in engineering surveying. Identify one specific
application and prepare a one page description indicating briefly
 how it works,
 how it is used
 how it assists the project team to achieve project objectives
 how it may change engineering practices .

You may use the following websites to choose and investigate an application, but feel free to
investigate other paths.

www.topconpositioning.com
www.trimble.com
http://www.gpsandmachinecontrol.com/
http://www.positionpartners.com.au/
http://mining.leica-geosystems.com
http://www.leica-geosystems.com/en/index.htm

END

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