Slope staking on exam

The HI is high probably because the level is setup uphill somewhere. The rod is at 107.67. Design el of 110.31 minus 107.67 is down 2.64 therefore you are in a fill. 28.5 offset minus 12 is 16.5 divided by 2.64 is 1:6.25 therefore the rod needs to move towards centerline about 6 feet. I think that’s what they mean by in but that is a bit ambiguous in my opinion.

Easy to see with a picture

110.31-107.67 = 2.64

2.64/0.25 = 10.56' from road to ground @ 4:1

12.0+10.56 = 22.56 o/s for toe of slope

28.5 (rod o/s) -22.56 = 5.94' to move closer to centerline to find toe

Yeah, everybody is giving me the numbers, like the sample answer. I filled in the diagram after seeing that it was fill. No problem. The numbers are easy once the problem is understood. 

What I'm looking for is an explanation of the thinking that goes on before you crank the numbers, for someone who is stupid, confused by their wording, and has never done slope staking.

Yeah, everybody is giving me the numbers, like the sample answer. I filled in the diagram after seeing that it was fill. No problem. The numbers are easy once the problem is understood. 

What I'm looking for is an explanation of the thinking that goes on before you crank the numbers, for someone who is stupid, confused by their wording, and has never done slope staking.

the natural ground is probably sloping. The task is to find the intersection of the 4:1 slope with the ground through trial and error. The Rodman pulls the tape from centerline to his guess where the intersection is. For purposes of the next trial shot assume the ground is flat, so move in 6 feet and try again. Maybe it’s still less than 4:1 so try again but the question is asking for an estimate of the move in distance for the next try.

you guys are causing a little anxiety here....just kidding.  I'm glad the question on " how do you approach the question" are being asked because they definitely leave room for over thinking and confidence in grasping one item but not fully grasping the whole.

whew.  glad I'm past this and beginning to aim at the next one.

to be sure, make sure you check the updates to the test prep questions, they had to correct about 4 I think recently because they didn't have the correct answer selected.  no I'm not kidding.  

Use the old formula to intersect the two grades.  (the existing ground determined by two shots and the proposed slope). 

Old is the key word here, and I really do not understand why these  examinations focus on ancient knowledge. Do you want your employees to be proficient in ancient techniques, and sacrifice productivity.

The concept of slope staking, and correct me if I'm wrong, is to stake the point at which a proposed grade meets existing grade. We called it the daylight line in one of my classes. That is most easily understood if the cross section is a cut and the side slope is rising out of cut to "daylight" at the existing ground.

It is a simple task with a computer model. It can also be translated by means of an alignment, profile, and cross section template in the field computer.

Since it is a trial and error process, a reading from the prism pole will translate to a cut or fill in the field computer. Once the cut or fill is zero you have achieved the daylight line. There are no stakes on the slope. The stakes are placed at the top or bottom of the slope. Is that correct?

Reliance on hand calculated methods would make the chance of errors greater that the reliance on a computer process.

Ahh, the old slope staking days. 

Things change fast in surveying. 

From the old days of a Brunton, right angle prism, tapes, 3 man crews to today with no stakes, no crews just some machine doing it all. 

Can't say I miss it. 

Even the local small guy is doing one of our subdivisions all on his own, totally machine control. 

I say have at it!!!!

Use the old formula to intersect the two grades.  (the existing ground determined by two shots and the proposed slope). 

Formulas? 

We did it all in our heads, I was younger then but we usually shouted out numbers while the PC was poking his calculator. By the time he had the catch point figured out we had the stake in the ground and marked up as he told us what to write on the lath. Already picking up and shifting to the next station. Slope staking is a feel thing after a while, some people instinctively get it and some just don't catch on. Of course, digging and filling were really helpful.

I only ever set slope stakes one time and I used a total station with data collector with the cross section template set in it, that was at least 25 years ago.  so yes the question is like asking an automotive tech how to put a steel band on a wooden wagon wheel.  The one project I did involved 15 to 20' high cut banks, to do that with a level would've been a lot more difficult.  I don't remember the fill side as much.

-Why would the slopes as given be flatter for fill than for cut?

Very common engineering principle. Fill slopes are always flatter than cut slopes. I'm not certain of the reasoning, but I was told that a 6:1 fill slope is about the maximum a runaway car can handle without flipping, while cut slopes are generally limited by the angle of repose of the material.   

I think that this is an excellent problem from several perspectives.

1) The student has to know whether the test point is above or below the roadbed. In the field that would be obvious, but working backwards from the numbers reinforces the relationship between the numbers and the terrain.

2) The student has to know whether he needs to move the rod closer to or further away from the instrument. This is a fundamental judgement that comes up in many real-world applications. It is a physical problem very much related to whether one value is greater or less than another, something that is sometimes very hard to teach in mathematics.

3) In addition to direction of movement, the student has to determine how far to move.

As to modern vs ancient methodology, we read frequent complaints about button-pushers. The old methods were derived directly from physical and mathematical concepts; the newer ones are one or more iterations away from those.

For a test, it could have been made easier by asking only one question like are you above or below the roadbed. 

But who would vote for easy exams?

Slope staking for me today is usually a pad, but the principle is the same with a road, dam, pad. For a pad site there will be a fill and a cut side along with two grade points. Normally I have the topo data for the pad design so in theory with a perfect topo I could pre calculate all the catches and stake them. I do know of many who "do" that or try to do that. The problem is the accuracy of the underlying topo data which is never perfect on raw ground. So it's better to calculate the catches in the field, and I believe much quicker. 

I will walk around the pad with the catch line inserted into the data collector and if the cut is 3:1, I find the point by wondering 12' from the cut line with a 4' cut and stake the point. It's not like the old days where the station controls the position. Let the station float and catch the even foot points. Basically, you fly through the process. And the dozer guy loves even foot catches, he doesn't care about stations. Same with the fill side usually a 4:1, find the point 16' out with a 4' fill, simple. The GPS drags you right to that point.