Question

A shovel with a 3-cy heaped capacity bucket is loading well blasted rock on a highway project. The

average face height is 22 ft. The shovel has a maximum rated digging height of 30 ft. Most of the cut will

require a 140-degree swing of the shovel to load the haul units. Use efficiency factor 45-minues per hour.

What is an aggressive production estimate in bank cubic yards? Show all the calculations

Answer 1

Given :- • Capacity of shovel bucket = 3- cy;

• The average face height = 22 ft;

• Maximum rated digging height of shovel = 30 ft ;

• Swing of the shovel = 140° ;

• Efficiency factor = 45 min per hour;

• Shovel bucket is loaded with well-blasted rock of highway project.

To find :- Production of shovel in bank cubic yards (bcy)

Solution:- The whole solution is shown in below images. The following steps are followed to calculate required production in (bcy per hour).

1. Step 1: Calculate optimum height = 0.5 times the maximum rated digging height = 0.5 × 30 = 15 ft

2. Step 2: Find Fill factors for front shovel buckets according to the material type given which is loaded into the bucket. Here, well-blasted rock material is used, for which fill factor is between 100 to 110%. Take Fill factor = 100%.

3. Step 3: Find Cycle Time according to the 3-cy capacity bucket of shovel. Cycle time is calculated by the equation given as:- Cycle time = Load + Swing loaded + Dump load + Swing empty.

For 3-cy capacity bucket, Load bucket = 9sec; swing loaded = 4 sec; Dump load = 4sec; Swing empty = 4sec

Cycle time = 9+4+4+4 = 21 sec = 0.35 min.

4. Step 4: Calculate ideal production (lcy/hr) which is equal to multiplication of fill factor with the capacity of shovel bucket (lcy) which is divided by the cycle time(hr).

Ideal production = (60/0.35) × 3 × 1.0 = 514 lcy/hr

5. Step 5: Calculate Percent Optimum height which is found out by dividing average face height by the optimum height calculated in step 1.

Percent optimum height = 22/15 = 1.47 = 147%

6. Step 6: Calculate height swing factor by interpolation which is shown in below images. Height swing factor is dependent on angle of swing and percent optimum height (%). The obtained height swing factor for 140° swing angle and at percent optimum height of 147% is 0.735.

7. Step 7: Calculate adjusted Ideal production by multiplying the height swing factor with the ideal production calculated in step 4.

Adjusted Ideal Production = 514 × 0.735 = 377.79 lcy/hr

8. Step 8: Calculate percent swell which depends on the material type used to load the shovel bucket. For well-blasted rock, the value of percent swell = 60% = 0.6

9. Step 9: Estimate the production in (bcy/hr) calculated by dividing the Adjusted Ideal production (obtained in step 7) by the ( 1 + percent swell).

Production = 377.79 / (1 + 0.6) = 236.12 bcy/hr.

10. Step 10: Given efficiency factor = 45min per hour.

Final production is calculated by multiplying the efficiency factor with the production (obtained in step 9).

Production (bcy) = (45/60) × 236.12 = 177.09 bcy/hr

The required value of production in bank cubic yards in 177.09 bcy/hr.