Explosive users should take steps to minimize vibration and noise from blasting and protect themselves against damage claims.

Vibrations caused by blasting are propagated with a velocity V, ft/s (m /s), frequency f, Hz, and wavelength L, ft (m), related by

L = V / f

Velocity v, in/s (mm/s), of the particles disturbed by the vibrations depends on the amplitude of the vibrations A, in (mm):

v = 2 p f A

If the velocity v₁ at a distance D₁ from the explosion is known, the velocity v₂ at a distance D₂ from the explosion may be estimated from

v₂ ? v₁ ( D₁ / D₂ ) ^1.5

The acceleration a, in/s² (mm/s²), of the particles is given by

a = 4 p² f² A

For a charge exploded on the ground surface, the overpressure P, lb/in² (kPa), may be computed from

P = 226.62 (W^1/3 / D ) ^1.407

Where
W = maximum weight of explosives, lb (kg) per delay

D = distance, ft (m), from explosion to exposure.

The sound pressure level, decibels, may be computed from

dB = ( P / ( 6.95 X 10^-28) )^0.084

For vibration control, blasting should be controlled with the scaled-distance formula:

V = H ( D / Ö W )^-b

Where
b = constant (varies for each site)

H = constant (varies for each site).

Distance to exposure, ft (m), divided by the square root of maximum pounds (kg) per delay is known as scaled distance.

Most courts have accepted the fact that a particle velocity not exceeding 2 in/s (50.8 mm/s) does not damage any part of any structure. This implies that, for this velocity, vibration damage is unlikely at scaled distances larger than 8

Production is measured in terms of tons or bank cubic yards (cubic meters) of material a machine excavates and discharges, under given job conditions, in 1 h.

Production, bank yd³/h (m³/h) = load, yd³ (m³) X trips per hour

Trips per hour = working time, min/h / cycle time, min

The load, or amount of material a machine carries, can be determined by weighing or estimating the volume. Payload estimating involves determination of the bank cubic yards (cubic meters) being carried, whereas the excavated material expands when loaded into the machine. For determination of bank cubic yards (cubic meters) from loose volume, the amount of swell or the load factor must be known.

Weighing is the most accurate method of determining the actual load. This is normally done by weighing one wheel or axle at a time with portable scales, adding the wheel or axle weights, and subtracting the weight empty. To reduce error, the machine should be relatively level. Enough loads should be weighed to provide a good average:

Bank yd³ = weight of load, lb(kg) / density of material, lb/bank yd³ (kg/m³)

Equipment Required

To determine the number of scrapers needed on a job, required production must first be computed:

Production required, yd³ /h (m³/h) = quantity, bank yd³ (m³) / working time, h

No. of scrapers needed= production required, yd³/h (m³/h) / production per unit, yd³/h (m³/h)

No. of scrapers a pusher can load= scraper cycle time, min / pusher cycle time, min

Because speeds and distances may vary on haul and return, haul and return times are estimated separately.

Variable time, min= (haul distance, ft /88Xspeed, mi/ h) + (return distance, ft/88Xspeed, mi/h)

Or
= (haul distance,m/ 16.7Xspeed,km/ h) + (return distance, m/16.7Xspeed,km/ h)

Haul speed may be obtained from the equipment specification sheet when the drawbar pull required is known.

When soils are excavated, they increase in volume, or swell, because of an increase in voids:

V_b = V_b L = ( 100 / ( 100 + % swell ) ) V_L

where
V_b = original volume, yd3 (m3), or bank yards

V_L = loaded volume, yd3 (m3), or loose yards

L = load factor

When soils are compacted, they decrease in volume:

V_c = V_b S

where
V_c = compacted volume, yd³ (m³)
S = shrinkage factor.

Bank yards moved by a hauling unit equals weight of load, lb (kg), divided by density of the material in place, lb (kg), per bank yard (m³).

External forces offer rolling resistance to the motion of wheeled vehicles, such as tractors and scrapers. The engine has to supply power to overcome this resistance; the greater the resistance is, the more power needed to move a load. Rolling resistance depends on the weight on the wheels and the tire penetration into the ground:

R = R_f W + R_p PW

where
R = rolling resistance, lb (N)

R_f = rolling-resistance factor, lb/ton (N/tonne)

W = weight on wheels, ton (tonne)

R_p = tire-penetration factor, lb/ton in (N/tonne mm) penetration

p = tire penetration, in (mm)

R_f usually is taken as 40 lb/ton (or 2 percent lb/lb) (173 N/t) and R_p as 30 lb/ton in (1.5% lb/lb in) (3288 N/t mm).

Hence,the above equation can be written as

R = (2% + 1.5 % p ) W’ = R’ W’

where
W’ = weight on wheels, lb(N)
R’ = 2% + 1.5%p.

Additional power is required to overcome rolling resistance on a slope. Grade resistance also is proportional to weight:

G = R_g s W

where
G = grade resistance, lb(N)

R_g­ = grade-resistance factor = 20 lb/ton (86.3 N/t) = 1% lb/lb (N/N)

s = percent grade, positive for uphill motion. Negative for downhill

Thus, the total road resistance is the algebraic sum of the rolling and grade resistances, or the total pull, lb ( N ), required:

T = (R’ + R_g s ) W’ = (2% + 1.5%p + 1%s)W’

In addition, an allowance may have to be made for loss of power with altitude. If so, allow 3 percent pull loss for each 1000 ft (305 m) above 2500 ft (762 m).

Usable pull P depends on the weight W on the drivers:

P = f W

where
f = coefficient of traction.

A wide variety of equipment is used to obtain compaction in the field. Sheepsfoot rollers generally are used on soils that contain high percentages of clay. Vibrating rollers are used on more granular soils.

To determine maximum depth of lift, make a test fill. In the process, the most suitable equipment and pressure to be applied, lb/in² (kPa), for ground contact also can be determined. Equipment selected should be able to produce desired compaction with four to eight passes. Desirable speed of rolling also can be determined.

Average speeds, mi/h (km/h), under normal conditions are given in Table below

Compaction production can be computed from
yd³/h (m³/h) = 16WSLFE / P

where
W = width of roller, ft (m)

S = roller speed, mi / h (km / h)

L = lift thickness, in (mm)

F = ratio of pay yd³ ( m³) to loose yd³ ( m³)

E = efficiency factor ( allows for time losses, such as those due to turns); 0.90, excellent; 0.80, average; 0.75, poor

P = number of passes