How to use an NRCS design
NRCS refers to Natural Resouce Conservation Service for our non North American customers.
One of our clients had some data picked up and a design done by NRCS and wants to know how to recreate the design in Ezigrade. Get an indicative volume calculation for how much dirt he needs to move. He also wants to create a control file for his grading machine.
Getting the surveyed data into Ezigrade:
|
On the right we have a portion of the data that has been surveyed. You can see we have a point number, Northing, Easting a height and a code. The data has been picked up along the channel so we have some points codes L for left and R for right.
It would be better if points were codes L1 and L2 as an example below:
|
|
If they were done this way then we could automatically string the points using the feature code library in CDS. However we have all the points on the left coded with an L so I will show you the more manual procedure to follow.
The first thing we need to do is to import the data. From Ezigrade got to Import -> Variable Ascii. If you like videos then you can view this
video of import variable ascii
Otherwise here is a quick run down.
(1) Create a new job. Make sure the units are appropriate. Probably US Survey feet.
(2) Click on Import -> Variable Ascii
(3) Browse to job and untick retrieve a previously saved format
(4) Next and 5 fields
(5) Next and set fields with data types
(6) Click Finish and we get:
Now the user needs to look at the triangulated surface and the contours to check that this is the result they are after. As the points were coded I would expect the L points would lie along features as per the right points coded with an R. It would be better if we created break lines along these points as it would represent the actual ground model better. However it comes back to the user whether it is important. It wont affect the finished result but will have an effect on volumes of dirt reported.
Using the same procedure I created some strings in the "discon1" folder and have this:
In this case not a lot has changed but in other examples it may make a practical difference.
Copy the Drain Design
For this job we have been supplied with a cut-sheet
If you look at the second last screen shot you can see the station points coded as 1000, 1100 etc At present we click in the nodes making up the drain from the screen. So the alignment will only be an approximation but will be OK for this sort of Civil Engineering structure. We normally tell everyone to click in the alignment from the outlet to the source. However in this case we are not doing any design so it may be less confusing to follow the NRC cutsheet and click in from source to outlet.Go to Drain -> Import Drain and click in the alignment joining the points with codes 1000, 1100 to 1620. Finish with an "Enter" key.
We get this:
Now we want to copy the profile of what has been designed for us. Click on the Drain -> Profile menu item and we have this:
In this case I would suggest that we use the Table option. Look towards the right of the profile view window: and type in the following data from the cut-sheet.
and the profile looks like this:
We now need to put in a section. From the cut sheet we can see that each section is 42' wide and extends left 21' and right 21'. The depth is 1.2' feet in the middle. We also know it is a parabella.The equation of a parabella is y = a x2 at x = 21 y = 1.2 thus a = .00272. Lets split into 3 bits but you can do as many as you want
x y
0 0
10.5 0.3
15.75 0.67
21 1.2
Close down the profile view and click on drain -> sections
Now click on Drain -> Recalculate and we have:
As a check we can get a value for amount of dirt to move. Click on Drain -> Volumes
and we have a cut volume of 665 cubic yards.
As a rule you should always check the volumes manually. The drain is 620 feet long, 42 feet wide and an average depth of about 0.8
ie vol = 620 * 42 * 0.6 / 27 = 580 So volume looks OK.
Creating a control file
to be continued.
