Been working on formulas to find catch points. I came up with some formulas i thought i was happy with but my horizontal distance seemed to get farther off the more parrallel the slope were. example (-slope - -slope) take the difference and divide it into my vertical fill rate. i found an exact method by converting my angles to gradian and using sine law thats a little more complicated. and ive ran across a few other formulas by carrusing through various D.OT. manuels. so anyay just curious if any one was familiar with this or had a fool proof formula to find the catch point with nothing more than a proposed vertical fill rate, a propsed slope ratio and a existing % of fall or rise
Being inexperienced more than most. i'll ask. What do you mean by catchpoint? Explain please Thanks you -Michael-
a catch point is were two slopes with diifferent rates of fall catch each other. say your existing ground is falling at a 25% (4:1) grade and your proposed vertical fill rate was say 15'. basicaly 15' above the edge of the road is proposed subgrade. and it will also fall chasing yer existing ground at a 33.33% or a (3:1). so a catch point is the horizontal distance in wich it takes for both exisitn and propsed slopes to connect. when starting a fill like this it important to know where that catchpoint point is because thats where yer scrapers are going to start filling to get proper compaction and to bring the fill up in even lifts.
Thanks i had to ask If not i wouldnt be the only one wondering what it was after someone else replied later -Michael- Questions= Learning
I used to set slope stakes out on Forest Service roads using a rag tape, 25' rod, clinometer, and a helper. The cut or fill slope ratio was known, but since the existing ground varied on each cross section, the "catch point" had to be calculated and measured simultaneously. It was a bit of a guessing game, with some math done in your head, but it worked well once you got the hang of it. As far as trying to pinpoint the exact horizontal distance to the catch point using a known fill/cut ratio and a supposed existing ground slope, your location will only be as good as the design survey was.
Catch Point ? A Catch Point is where the design slope grade and actual existing grade match . " It Catches " Also that is where the cut or fill starts . Cut and Fill stakes , usually denote whether the fill or cut is FAT, or SHY. Grade Checkers use + or - to indicate. A ribbon on the crowfoot indicates it is on grade. No further work is needed.
This has more to do with the bigger companys with GPS,do they still have grade checkers or is it all done with GPS. I know the smaller companies like me still will be doing the grade checking,i have at least gone with the laser system.Still have to do measuring and set stakes. The old days it was grade stakes,tape,hachet,handlevels,and helper. If you have design stakes or even just to get a idea of the lay of the ground quickly the hand level is still a handy tool for checking rough grade at least. How many still have or use eyelevel is what i would like to know:beatsme :usa
We teach with hand levels constantly. in the advanced road building class we sometimes even have them build thier own banjos, to speed up thier grade checking. I always get nervous when the blade is coming and the student grade checker is still standing out in the middle of the road trying to level up his hand level. We are partnering up with Volvo and trimble laser and GPS. and next month sometime they are supposed to send a few of us to california to become certified G.P.S instructors. Im kind of excited even though i have a little natural born resentment towards GPS. Ive always believed that its the last little bit is what seperates extraordianry for ordinary. Even with all the positives of GPS it sure seems like it makes some of us way to interchangeable with all those guys who should be pushing up bulk material rather than finishing anything.
In my experience GPS is only a tool to help an operator. It wont replace a good operator by any means. If anything, we have had a very positive response from our best operators. Like any other tool it is limited in its capabilities and is no replacement for a good hand only an assistant.