Construction Problem help

[jenni179]

Hey guys,

I'm having difficulty with an earthwork construction problem (see attachments). The solution says I should use the Prismoidal Method for STA 519+00 thru 520+00 and STA 524+00 thru 525+00, and the average end area method in between. I first calculated the problem using ONLY End Area method, and I got answer C which is not correct, apparently.

I have 3 questions:

1.)The CERM says I should apply the Prismoidal method when the areas differ greatly. Since the first two and last two areas differ greatly from each other, is that why the Prismoidal method was used?

2.) If so, then should I apply this theory to ALL earthwork problems whose areas differ greatly from one another?

3.) On my second attachment (the Solution), for the Volume from STA 524+00 and 525+00, why do they divide it by 81? The CERM Eq 79.10 has V = (L/6)*(A1+ 4*Am + A2). When looking at the CERM, I don’t understand how this equation is applied in this problem.

I would greatly appreciate any assistance. I know this isn’t a difficult problem but I’m trying to understand the difference between Average End Area and Prismoidal Method and how to correctly use these equations.

Thanks so much,

Jen

Problem.pdf

Solu.pdf

 

[civilized_naah]

Hey guys,
I'm having difficulty with an earthwork construction problem (see attachments). The solution says I should use the Prismoidal Method for STA 519+00 thru 520+00 and STA 524+00 thru 525+00, and the average end area method in between. I first calculated the problem using ONLY End Area method, and I got answer C which is not correct, apparently.

I have 3 questions:

1.)The CERM says I should apply the Prismoidal method when the areas differ greatly. Since the first two and last two areas differ greatly from each other, is that why the Prismoidal method was used?

2.) If so, then should I apply this theory to ALL earthwork problems whose areas differ greatly from one another?

3.) On my second attachment (the Solution), for the Volume from STA 524+00 and 525+00, why do they divide it by 81? The CERM Eq 79.10 has V = (L/6)*(A1+ 4*Am + A2). When looking at the CERM, I don’t understand how this equation is applied in this problem.

I would greatly appreciate any assistance. I know this isn’t a difficult problem but I’m trying to understand the difference between Average End Area and Prismoidal Method and how to correctly use these equations.

Thanks so much,

Jen

1. The prismoidal method is to be used when one end area is zero or nearly zero. That's true for 519 to 520 and 524 to 525

2. When the end area at one of the stations is zero, you should use the Prismoidal formula for the volumes adjacent to that station.

3. The formula for volume of a pyramid is AL/3. The factor '3' in the denominator combined with the '27' factor to convert cu ft to cu yd is the 81

 

[jenni179]

Hey guys,
I'm having difficulty with an earthwork construction problem (see attachments). The solution says I should use the Prismoidal Method for STA 519+00 thru 520+00 and STA 524+00 thru 525+00, and the average end area method in between. I first calculated the problem using ONLY End Area method, and I got answer C which is not correct, apparently.

I have 3 questions:

1.)The CERM says I should apply the Prismoidal method when the areas differ greatly. Since the first two and last two areas differ greatly from each other, is that why the Prismoidal method was used?

2.) If so, then should I apply this theory to ALL earthwork problems whose areas differ greatly from one another?

3.) On my second attachment (the Solution), for the Volume from STA 524+00 and 525+00, why do they divide it by 81? The CERM Eq 79.10 has V = (L/6)*(A1+ 4*Am + A2). When looking at the CERM, I don’t understand how this equation is applied in this problem.

I would greatly appreciate any assistance. I know this isn’t a difficult problem but I’m trying to understand the difference between Average End Area and Prismoidal Method and how to correctly use these equations.

Thanks so much,

Jen

1. The prismoidal method is to be used when one end area is zero or nearly zero. That's true for 519 to 520 and 524 to 525

2. When the end area at one of the stations is zero, you should use the Prismoidal formula for the volumes adjacent to that station.

3. The formula for volume of a pyramid is AL/3. The factor '3' in the denominator combined with the '27' factor to convert cu ft to cu yd is the 81

Thank you so much civilized_naah!