Section IIApplications of Measurements

2. Earthwork كمیات الحفر و الردم

Profile Levelingالقطاعات الطولیة

• To collect data about topography along a reference line.

• Mainly to compute volumes of cut and fill و الحفر

الردم for a proposed linear structure, such as: highways, railroads, transmission lines, canals. Then the best route can be chosen.

• The result: elevations at definite points (stations) along a reference line, usually the center line.

Field Procedures

Profile leveling

• First a backsight at a BM is observed.

• Then, a number of intermediate sights are observed at the locations needed, do not have to be at equal distances.

• When the distance becomes too long, or readings become hard to observe, a turning point نقطة دورا ن is constructed.

• You cannot keep the backsight distance equal to the foresight distance.

• Elevation computation:

– Elevation of line of sight (LS) = EBM + BSBM.

– Elevation of any intermediate point = ELS - ISIP.

– Elevation of point at FS = ELS - FSPOINT

– Handle new level positions as in differential leveling, construct a turning point and knowing BS and FS readings, compute a new elevation of line of sight.

ExamplePoint Backsight

(BS)مؤخرة

Intermediate sight (IS)

متوسطة

Foresight (FS)مقدمة

Elevation ofline of sight (HI)منسوب خط النظر

Elevation

BM 09

1.573 20.00

1 1.472

2 1.718

3 1.352 1.551

4 1.181

5 1.492

6 2.101

1.212

AnswerPoint Backsight

(BS)مؤخرة

Intermediate sight (IS)

متوسطة

Foresight (FS)مقدمة

Elevation ofline of sight (HI)منسوب خط النظر

Elevation

BM 09

1.573 20.00

1 1.472

2 1.718 19.885

3 1.352 1.551

4 1.181

5 1.212 1.492

62.101

21.573

20.101

20.02221.374

20.193

19.88221.094

18.993

Drawing and Using Profiles• Drawn using a software now.

• To manually draw a profile and compute earthwork:– Assume the horizontal axis is the distance and the

vertical axis is the elevation.

– Use a larger scale for the elevation than the scale of the distance, usually 10 times larger.

– Draw the design line at the proposed grade المیل .

– Compute the areas of cut and fill.

– Multiply area by width to get volumes.

– Gradient المیل (percent grade) is the rise or fall in m per 100.

Horizontal scale 1: 2500 Vertical scale 1: 250

ExampleThe table below shows ground elevations along the centerline of a proposed pipeline. If the bottom of the trench to be excavated is at elevation (+115m) at point (A) and slopes -1%, and the the trench is 2m wide, compute the volumes of cut and fill. {Answer is given in lecture}

Point Distance (m) Elevation (m)

A 0.0 115.0

B 100 117.2

C 200 116.0

D 300 112.0

E 400 110.5

F 500 110.0

Borrow-Pit Method المیزانیة الشبكیة• Not suitable for linear features, very useful for construction

sites.

• The site is divided into equal squares. Elevations are then measured at the corners of the grid الشبكة , which are given names that correspond to the corner coordinates in the grid, ex: 3-D, 4-A, etc. Then heights of cut or fill (hij) over design elevation are computed. Where is the height at the intersection of axes i with axis j, then:

V = (hijn) A yd3

4*27

• The idea is to multiply each height by the number of complete squares it is common to (n), the product is then multiplied by (A/4) where A is the area of one of the squares

( )

The volume on any square, or part of a square is equal to the average height(elevation difference) at the corners, times the area.To compute the volume: 1- draw a line between the cut and the fill areas

2- compute the total volume of all the complete cut squares,do the same for the fill, use the previous formula

3- Compute the incomplete squares separately and add them to thesquares.

4- Compute the difference between the cut and the fill., pay attention to the expansionfactor.

A B C

V1 = A *(hA1 + hB1 + hA2 + hB2) / 4

V2 =A *(hB1 + hC1 + hB2 +hC2) / 4

V3 = A* (hA2 + hB2 + hA3 +hB3) / 4

Total volume V = A* {(hA1 + hB1 + hA2 + hB2) / 4} + A*

{(hB1 + hC1 + hB2 +hC2) / 4} + {A*(hA2 + hB2 + hA3 +hB3) / 4} =

(hA1 +2 hB1 + hC1 + 2 hA2 + 3 hB2 + hC2 + hA3 + hB3) / 4

hA1 hB1 hC1

hA2 hB2 hC2

hA3 hB3

1

2

3

Example

The table below shows the heights of cut and fill in meters at the corners of a 20m grid. Compute the volume of soil to be imported or disposed. Assume 25% expansion factor for the fill. ( + is cut, - is fill)

Corner A-1 B-1 C-1 D-1 A-2 B-2 C-2

Height +3.1 +2.8 +2.0 +4.0 +2.8 +2.2 +1.5

Corner D-2 A-3 B-3 C-3 D-3 A-4 B-4

Height +1.2 +2.0 +1.7 +1.0 0.0 +1.5 +0.8

Corner C-4 D-4

Height 0.0 - 3.00