Question

How many trips would one rubber-tired Herrywampus have to make to backfill a space with a geometrical volume of 5400 cubic yard? The maximum capacity of the machine is 30 cubic yard (heaped), or 40 tons. The material is to be compacted with a shrinkage of 25% (relative to bank measure) and has a swell factor of 20% (relative to bank measure). The material weighs 3,000 lb/cu yd (bank). Assume that the machine carries its maximum load on each trip. Check by both weight and volume limitations

Answer 1

If analyzed by volume capacity, more trips are needed to fill the space, thus the required trips are 288

Step-by-step explanation:

a) By volume.

The shrinkage factor is:

`(5400cu-yd)/(1-0.25) =7200cu-yd`

The volume at loose is:

`V_(loose) =V_(bank) (1+swell-factor)=7200(1+0.2)=8640cu-yd`

If the Herrywampus has a capacity of 30 cubic yard:

`(8640cu-yd)/(30cu-yd/trip) =288trip`

b) By weight

The swell factor in terms of percent swell is equal to:

`pounds-per-cubic-yard-loose=(pounds-per-cubic-yard-bank)/((percent-swell)/(100)+1 )`

`pounds-per-cubic-yard-loose=(3000)/((20)/(100) +1) =2500lb/cu-yd`

The weight of backfill is:

`8640cu-yd*2500(lb)/(cu-yd) *(1ton)/(2000lb) =10800ton`

The Herrywampus has a capacity of 40 ton:

`(10800)/(40ton/trip) =270trip`

If analyzed by volume capacity, more trips are needed to fill the space, thus the required trips are 288