FACULTY OF CIVIL AND ENVIRONMENTAL ENGINEERING DEPARTMENT OF INFRASTRUCTURE AND GEOMATIC ENGINEERING Subject Code Practical Name Course Code Practical Date Group Section Group Leader
Group Members
Lecturer Name/ Instructor/ Tutor Marks
Comments
BFC 20703 Two Peg Test, Leveling (Establish TBM) 2 BFF 10/10/14 5 1 1. Kok Hui Li (AF130195) 2. Loke Hoong Kee (AF130190)
3. Nadzirah Afiqah binti Abdullah (DF120021) 4.Muhammad Ammar bin Nasaruddin (BF130001) 5. Mohd Shafiq Imran bin Abdul Aziz (AF130109) Sir Saifullizan Mohd Bukari Introduction / 5% Objective / 5% Theory / 10% Instrument / 5% Procedure / 5% Data/ Table / 10% Data analysis / 20% Discussion / 15% Presentation/Plotting / 10% Conclusion/Recommendatio / 10% n Reference / 5% Total mark / 100% Accepted Seal
STUDENT CODE OF ETHIC (SCE) DEPT.OF WATER RESOURCES & ENVIRONMENTAL ENG. FACULTY OF CIVIL & ENVIRONMENTAL ENGINEERING UTHM
I, hereby confess that I have prepared this report on my own effort. I also admit not to receive or give any help during the preparation of this report and pledge that everything mentioned in the report is true.
Student Signature :___________________________ Name : ………………………………………… Matric No. : ………………………………………… Date : ………………………………..……… Student Signature :___________________________ Name : ………………………………………… Matric No. : ………………………………………… Date : ………………………………..……… Student Signature :___________________________ Name : ………………………………………… Matric No. : ………………………………………… Date : ………………………………..……… Student Signature :___________________________ Name : ………………………………………… Matric No. : ………………………………………… Date : ………………………………..……… Student Signature :___________________________
Name : ………………………………………… Matric No. : ………………………………………… Date : ………………………………..……… 1.0 INTRODUCTION PART 1 (TWO PEG TEST) Two peg tests is a surveying operation carried out to determine whether the leveling bubble and telescope line of sight are parallel. PART 2 LEVELLING (ESTABLISH TBM) Vertical Control is the general term applied to any of the various processes by each elevation of point or differences in elevation are determined. It is a vital operation in producing necessary data for mapping, engineering design, and construction.
2.0 OBJECTIVE PART 1 (TWO PEG TEST) a) To determine if the levelling bubble (bubble axis) and telescope line-of-sight (line of collimation) are parallel. PART 2 LEVELLING (ESTABLISH TBM) a) To fly reduced level from known point (Benchmark or Temporary Benchmark) to unknown point.
3.0 THEORY PART 1 (TWO PEG TEST) If m = m’, we can conclude that the instrument is ok. If m ≠ m’, the instrument does not ok and we must do some correction. The error is called collimation error which is, e = (S1 – S2) – (S1’ – S2’) / L mm/m Acceptable error is 1mm per 20m.
PART 2 LEVELLING (ESTABLISH TBM) i) Rise and fall method is being used in this report to determine the heigh and elevation of TBM. The terms that are used in this method are: BS=Backsight FS=Foresight IS=Intermediate Sight RL=Reduced Level D=Total Distance(meter) ii) The distance between the automatic level and the BS and FS should be equal. iii) The substraction of the BS and FS was being obtained for the RISE in the positive value and FALL in the negative value. iv) The RL of the TBM 1 is being assumed. v) The following RL is eaual to the sum of the previous RL and the value of RISE or FALL. vi) Page check is being carried out after we obtained the reading of the measurement. ƩBS – ƩFS = ƩRISE – ƩFALL = RLBOTTOM - RLTOP vii) The end closure = RLBOTTOM – RL of TBM 1 D viii) The end closure should be in the range of the allowable closure. Allowable closure = ± 20 mm ix) The correction of the RL was being calculated by the sum or substraction of the end closure and RL.
4.0 APPARATUS 1. Level and tripod ( 1 set )
Figure 1 : Automatic level
Figure 2 : Tripod
2. Staff ( 2 sets )
Figure 3 : Level Staff 3. Staff bubble ( 2 sets )
Figure 4 : Staff bubble
4. Tape ( 1 set )
5.0 PROCEDURE
PART 1 (TWO PEG TEST) 1. A peg test was performed by each group to check the instrument.
2. The result of the peg test was recorded by each person in the group in their own field book. 3. The ground was set out and marked two points some 30m apart (marked with wooden pegs driven into the earth or roofing nails in tar). 4. The instrument was set up in the middle between two pegs. 5. Staff on each pegs (back sight and foresight) was read and height difference was calculated. 6. The instrument was moved about L/10 = 3m beyond one of the pegs (normally for staff position). 7. Staff on each peg was read again and height difference was calculated.
PART 2 LEVELLING (ESTABLISH TBM)
FIELD PROCEDURES a) Observation Procedures i. A series of measurements of level loop as shown in Figure 3.3 was ii.
considered and applied to the field work. During the field work, the levelling survey started at TBM 5, the first reading measurement from Setup 1 was a back sight to TBM
5, and the second reading was a foresight to CP1 known as a iii.
Change Point. The levelling staff then remained at CP1, while the instrument moved to Setup 2. Back sight reading to CP1 was taken, and foresight reading to CP2 was taken, and so on until designated
iv.
TBM 6 was reached. The process continued until eventually, a Setup N (the last setup before closing the loop) was made, back sight reading to the
v.
previous CP was taken and foresight reading to TBM 5 was taken. The traverse was closed and a check on the booking date was made.
Figure 5.1: A sample of levelling loop
b) Booking Procedures The Rise and Fall Method The terms that were commonly used in the Rise and Fall Method are: BS = Back sight FS = Foresight IS = Intermediate Sight, and RL = Reduced Level c) Reduction (Calculation) Procedures i. The survey’s accuracy was checked for tolerances limit. This check was applied before leaving the job. ii. The following arithmetic check was done to the survey’s level reductions: ΣBS −¿ ΣFS = ΣRise – ΣFall (BS) – (FS) = RL (last BM) – RL (start BM)
iii. Misclosure was checked by comparing its value with ±(20√K) mm, where K is the length of the traverse in km. If greater than ±(20√K) mm, it is unacceptable. Otherwise, the value is acceptable. iv. For example, miclosure is +30mm and the length of the loop is 0.7 km. Hence the miclosure limit is 20√0.7= ±17mm. Therefore, the misclosure of +30 mm is too big (means that the levelling work is not accepted).
6.0 DATA AND ANALYSIS PART 1 (TWO PEG TEST)
First set up
Second set up
Reading Staff B ( S1)
Reading Staff A ( S2 )
Height Difference = m
1.292
1.289
0.003
Reading Staff B ( S1’ )
Reading Staff A ( S2’ )
Height Difference = m’
1.300
1.299
0.001
Difference ( m – m’ )
30m
60m
0.003
0.001
DATA ANALYSIS 1. From the result in the table above, we clearly see that the m ≠ m’. 2. That’s mean the instrument is not ok because based on the theory, the instrument will be nearly perfect when m = m’. 3. Unfortunately, we got m = 0.003mm for the first set up while we got m’= 0.001mm with the second setup. The difference between m-m’ = 0.002. 4. From the observation, the error is calculated by e = (S1 – S2) – ( S1’ – S2’) / L mm/m e = (0.003-0.001)* (10³) / 60 mm/m = 2 / 60 mm/m = ±0.0333 mm/m
5. The error is called collimation error. 6. The error was acceptable which 1mm per 20m was.
PART 2 LEVELLING (ESTABLISH TBM) Turn to the next page.
DATA ANALYSIS i.
Page check:
ΣBS – ΣFS
= 9.781 – 9.783 = -0.002 m
ΣRISE – ΣFALL = 0.608 – 0.610 = -0.002 m RLB - RLT
= 3.590 – 3.592 = -0.002 m
ii.
End Closure:
TBM 5 - RLB
= 3.592-3.590 = 0.002 m
iii.
Allowable Closure:
Allowable closure = ±20√D = ±20√0.228 = 9.55mm Note: Since allowable closure is 9.55 mm, the error of 0.002mm is accepted with the condition of adjustment is needed. iv.
Adjustment:
End closure / ΣFS
= 0.002 / 8
= 0.00025 per FS
7.0 DISCUSSION PART 1 (TWO PEG TEST) 1. Two Peg Test is a surveying operation carried out to determine if the leveling bubble and telescope line of sight are parallel. 2. Level staff readings that would have been obtained if the line of collimation was horizontal where there is the error in each reading due to the collimation error and the effect of which is to tilt the line of sight by an angle. 3. Two pegs are placed 30m apart and the level midway between two pegs has been set up. Then, calculate the true height difference that is m=
s1
-
s2
4. From the result, it showed that there is no difference in height between the two peg. If there is a difference, it is the error which called collimation error. We calculate it by s1 e= ¿
-
s2
'
)-
s1 ¿
' - s2 )
L
PART 2 LEVELLING (ESTABLISH TBM) 1. When setting up the tripod, be sure to spread the legs until the tripod head is approximately horizontal and they should be far enough apart to prevent the instrument from being blown over by a gust of wind, and they should be pushed into the ground far enough to make the level stable. However, in cases of setting up on roads or sidewalks or pavements, do not push the legs’ sharp tips into the ground or else, the tripod legs will spoil and lose its vertical balance. 2. When taking readings using the level instrument, be sure to eliminate parallax error before reading the staff. Parallax error exists whenever the vision of the staff is blurry or shaky. By adjusting the focusing screw until vision is clear and vivid, then only readings can be taken at the cross hairs. Make sure readings are taken at a
constant line of sight within the cross hairs and always compare the reading on the left and right of the staff whenever a doubt pops up. 3. When calculating the distance for each setup, bear in mind that for levelling, the distance between the level setup and a level staff should not exceed 30 m. One should also make sure the line of sight between these two elements is clear through and not blocked by physical features of the surroundings. For example, a tree, a pillar or a signboard. 4. During levelling work, errors are bound to occur. The principal sources of error in levelling are instrumental defects, faulty manipulation of the level or staff, settling of the level or staff, errors in sighting, mistakes in reading the rod or in recording or computing, errors due to natural sources and personal errors. Each and every one of these errors has a precaution that can be taken to ensure the minimisation of these errors. 5. In order to cancel out instrumental and natural occurring errors, the distances between BS and FS have to be kept equal. However in certain situations such as a river or valley crossings, it is not always possible to balance it out. Thus, the reciprocal levelling technique can be applied here. This is because the averaging process in this technique will eliminate instrumental and natural errors, such as curvature. Errors due to refraction can be minimised by ensuring that the elapsed time for the process is kept to a minimum. For refraction, do not take readings on the level staff less than 0.5 m.
8.0 CONCLUSION PART 1 (TWO PEG TEST)
From the two peg test, we got 0.00003m. So the, the error is acceptable because from the theory,
an
acceptable error must 1mm per 20m.
PART
2
LEVELLING (ESTABLISH TBM) A temporary benchmark (TBM) has been established at the desired location. The objective has been achieved. The reduced level of the point TBM is 3.592 m.
9.0 REFRENCE
Lab sheet given by Sir Saifullizan Mohd Bukari, University Tun Hussein Onn Malaysia, Faculty of Civil & Environmental Engineering.
Map of TBM 5 and TBM 6 in UTHM campus Figure 10.1 : The map of TBM 5 ,TBM 6 and TBM 1 in UTHM campus
