DRY DENSITY OF SOIL BY CORE CUTTER METHOD

TO DETERMINE DRY DENSITY OF SOIL BY CORE CUTTER METHOD

Theory:

A cylindrical core cutter is a seamless steel tube. For determination of the dry density of the soil, the cutter is pressed into the soil mass so that it is filled with the soil. The cutter filled with the soil is lifted up. The mass of the soil in the cutter is determined. The dry density is obtained as

Where M= mass of the wet soil in the cutter

V= internal volume of the cutter

w= water content.

Equipment:

1. Cylindrical core cutter, 100mm internal diameter and 130mm long

2. Steel rammer, mass 9kg, overall length with the foot and staff about 900mm.

3. Steel dolley, 25mm high and 100mm internal diameter

4. Weighing balance, accuracy 1g.

5. Palette knife

6. Straight edge, steel rule etc

Procedure

1. Determine the internal diameter and height of the core cutter to the nearest 0.25mm

2. Determine the mass (M1) of the cutter to the nearest gram.

3. Expose a small area of the soil to be tested. Level the surface, about 300mm square in area.

4. Place the dolley over the top of the core cutter and press the core cutter into the soil mass using the rammer. Stop the pressing when about 15mm of the dolley protrudes above the soil surface.

5. Remove the soil surrounding the core cutter, and take out the core cutter. Soil soil would project from the lower end of the cutter.

6. Remove the dolley. Trim the tip and bottom surface of the core cutter carefully using a straight edge.

7. Weigh the core cutter filled with the soil to the nearest gram (M2).

8. Remove the core of the soil from the cutter. Take a representative sample for the water content determination.

9. Determine the water content.

Observation and calculations:

Sl. No.	Observations an Calculations	Determination No.
		1	2	3
Observation
1	Core cutter No.
2	Internal diameter
3	Internal height
4	Mass of empty core cutter (M1)
5	Mass of core cutter with soils (M2)
Calculations
6	M=M2 – M1
7	Volume of cutter V
8	Water content
9	Dry density using formula

Result:

Dry density of the soil= ________g/ml.

Measurement of distance with tapes

Precisions for different methods of measuring distances are given below:-

Pacing (ordinary terrain): 1/50 to 1/100

Taping (ordinary steel tape): 1/1000 to 1/10,000.

Baseline (invar tape): 1/50,000 to 1/1,000,000

Stadia: 1/300 to 1/500

Subtense bar: 1/1000 to 1/7000

Now with technological advances, a technique called Electronic distance measurement or EDM is replacing the use of steel tapes as they are much more precise then steel tapes.

Ranging and Fixing Of Survey Station

The object of this experiment is to set up a survey station. This is the basic step of surveying but this is also the one which has the maximum number of errors.

The Equipments used for this are :-

1. Ranging rod …………5 Nos. (min).
2. 30 m Chain…………..1 Nos.
3. Arrow…………………5 Nos. (min.)

The Procedure to conduct is as follow :

(Ranging by eye)
1. First of all first ranging rod is established at known point A and its ranging rod should be fixed at point A up to completion of work.

2. Second ranging rod is established at known point B (or at known object) and a ranging rod should be fixed at point B up to completion of work.

3. Third ranging rod established at point P (or any) approximately on the line of point AB (by judgment) and it’s not greater than one chain length from point A.

4. Measure the distance of AP by chain and move ranging rod at point P to its next position and establishing a wooden peg or arrow at point P.

5. Third ranging is established at point Q (or any) approximately on the line of point AB (by judgment) and it’s not greater than one chain length from point P.

6. Measure the distance of PQ by chain and move ranging rod at point Q to its next position and establishing a wooden peg or arrow at point Q.

7. Its procedure repeats up to reaching point B.

8. Third ranging rod is established at known point C (or at known object) and a ranging rod should be fixed at point C up to completion of work.

9. Fourth ranging rod established at point P’ (or any) approximately on the line of point BC (by judgment) and it’s not greater than one chain length from point B.

10. Measure the distance of BP’ by chain and move ranging rod at point P’ to its next position and establishing a wooden peg or arrow at point P’.

11. Fourth ranging is established at point Q’ (or any) approximately on the line of point BC (by judgment) and it’s not greater than one chain length from point P’.

12. Measure the distance of P’Q’ by chain and move ranging rod at point Q’ to its next position and establishing a wooden peg or arrow at point Q’.

13. Its procedure repeats up to reaching point C.

14. Fifth ranging rod established at point P” (or any) approximately on the line of point CA (by judgment) and it’s not greater than one chain length from point C.

15. Measure the distance of CP” by chain and move ranging rod at point P” to its next position and establishing a wooden peg or arrow at point P”.

16. Fifth ranging is established at point Q” (or any) approximately on the line of point CA (by judgment) and it’s not greater than one chain length from point P”.

17. Measure the distance of P”Q” by chain and move ranging rod at point Q” to its next position and establishing a wooden peg or arrow at point Q”.

18. Its procedure repeats up to reaching point A.

19. Finally complete a triangle and position of point A, B, and C is known respect to each other.

Precautions: – 
1. The ranging rod should be established correctly state at all points.
2. The judgment of line should be taking correctly during established ranging rod at a point.
3. Distance between surveyor’s eye and reference station (eg. A, B and C) should be minimum one meter.

What is Orthometric Correction?

We know that earth flattens in the polar direction and this curvature of earth is responsible for the departure of horizontal line from a level surface. To counter this error, orthometric corrections is applied.

This departure in feet, C_f is calculated as
C_f= 0.667M²=0.0239F²

This departure in meters, C_m is calculated
C_m =0.0785K ²

where M = distances in miles from the point of tangency to the earth.
F= distances in thousands of feet from the point of tangency to the earth.
K = distances in kilometers from the point of tangency to the earth.

What are the Corrections Applied in Surveying?

For surveying, we need to have some prerequisite conditions. If these conditions are not met we can have a huge variation in result. Therefore we have to apply corrections to get the true result.

Ideal Conditions
1) A tape accurate to 0.00305m or 0.01 ft should be used.
2) Tension of the tape should be about 66.7N or 15 lb.
3) Temperature should be determined within 5.56°C or 10°F
4) The slope of the ground, should be within 2 percent

On ground these are nearly impossible to achieve and thus corrections need to be applied.

Corrections Applied for Temperature
The correction applied on steel tape is C_t=0.0000065s(T-T₀)
where
C_t= temperature correction to measured length, ft (m)
T=temperature at which measurements are made, F ( C)
T₀= temperature at which tape is standardized, F ( C)
s= measured length, ft (m)

Correction Applied to Measurements on Slope
C_h= s (1-cos@) [exact]
or = 0.00015s@²[approximate]
or = h²/2s
where
C_h= correction to be subtracted from slope distance, ft (m)
s= measured length, ft (m)
@ =slope angle, degree
h= difference in elevation at ends of measured length, ft (m)

Correction Applied for Tension 
C_p=s[P_m-P_s]/SE

Correction Applied for Sag when not Fully Supported
C_s=w²L³/24P_m²

where
C_p= tension correction to measured length, ft (m)
C_s = sag correction to measured length for each section of unsupported tape, ft (m)
P_m actual tension, lb (N)
P_s tension at which tape is standardized, lb (N) (usually 10 lb) (44.4 N)
S=cross-sectional area of tape, in² (mm²)
E= modulus of elasticity of tape, lb/in² (MPa) (29 million lb/in²(MPa) for steel) (199,955 MPa)
w= weight of tape, lb/ft (kg/m)
L= unsupported length, ft (m)

What are Slope Corrections?
We know that the horizontal distance H= Lcos@, where L slope distance and @=vertical angle, measured from the horizontal.

For slopes of 10 percent or less
C_s=d²/2L

For a slope greater than 10 percent
C_s=d²/2L+d⁴/8Ld³

What are Temperature Corrections in terms of length?
C_t=(actual tape length-nominal tape length)L/nominal tape length

For nonstandard tension:
C_t(applied pull-standard tension)L/AE
where A= cross-sectional area of tape, in² (mm²)
E=modulus of elasticity29,000,00 lb / in² for steel (199,955 MPa).

For sag correction between points of support, ft (m):
C= -w²L³_s/24P²
where
w = weight of tape per foot, lb (N)
L_s= unsupported length of tape, ft (m)
P=pull on tape, lb (N)

Units of Measurement

Units of measurement used in past and present surveys are

For construction work: feet, inches, fractions of inches (m, mm)
For most surveys: feet, tenths, hundredths, thousandths (m, mm)
For National Geodetic Survey (NGS) control surveys: meters, 0.1, 0.01, 0.001 m

The most-used equivalents are
1 meter=39.37 in =3.2808 ft
1 rod =1 pole=1 perch=16.5ft(5.029 m)
1 engineer’s chain =100 ft =100 links (30.48 m)
1 Gunter’s chain= 66 ft (20.11 m) =100
Gunter’s links(lk)=4 rods=0.020 km

1 acre=100,000 sq (Gunter’s) links=43,560ft²= 160 rods²=10 sq (Gunter’s) chains=4046.87m²=0.4047 ha

1 rood=1011.5 m²=40 rods²

1 ha= 10,000 m²=107,639.10 ft²=2.471 acres

1 arpent=about 0.85 acre, or length of side of 1 square arpent (varies) (about 3439.1 m²)

1 statute mi=5280 ft=1609.35 m

1 mi²=640 acres (258.94 ha)
1 nautical mi (U.S.)= 6080.27 ft= 1853.248 m

1 fathom=6 ft (1.829 m)

1 cubit=18 in (0.457 m)

1 degree=0.01745 rad=60 min =3600 s
sin 1 =0.01745241
1 rad = 57.30 degree