Case study - Example of railways

The present case study analyzes a situation of earth moving in the case of a railroad.

The example is a real project.

For the purpose of analysis, open the mvp04.Ddm

In the project for the distribution of earthmoving of this segment of railroad, studies are initially made for the dimensioning of the railway superstructure, defining the thickness of the layers:

In order to determine maximum loads to the body of the projected landfills and also to validate the bearing capacity of the subgrade in the sections in court.

Because loads are high, some stretches may not have adequate support capacity, and replacement is required.

Cutting materials also have varied characteristics, which direct the cut material to one demand or another.

At the end of the day what is important is to minimize the moment of transport, since cuts and landfills should be meet geometry.

In the example, we are designing a railroad in a location with a high occurrence of material, which corresponds to more or less half of the total earthmoving volume. This forced the decision to build landfill with third material, separately from the landfill body in soil, because the inclination of the slopes of the sidewalks in soil or in rock are different and the stability of the landfill body was compromised.

Also cuts in third material have a high index of fractures and have been recommended that you make benches every 5.00 m:



In general, the superstructure is constant, only varying the reinforcement / final layer. I will not go into the merits of this design.

The result sizing of the superstructure that is also a function of the results of probes, you need:

The ISF 207 - Geotechnical Studies, provides the necessary guidance for the geotechnical study:

The first step is to get the survey data. Example:

 From it, the statistical study is done, to determine the homogeneous segments with the data of CBR and Expansion will have something like this:

Here we notice that there are intervals of the segment whose material is not so good, for example, in the interval 186 + 200 to 186 + 600, the CBR of the material is low, about 3.1. Therefore, by sizing the body of the landfill, it must be replaced.

Third-category material at the beginning should not need this segmentation. But cases may occur where it is easier to use this feature also in material of third. See the Allow third category Segmentation. In this case study, we will allow the use of segmentation so that we can CBR, Expansion, and Permeability values that inhibit used in landfill. The values adopted shall be Segmentation tab for Third Category, Cut and Undercut Sources:

In the dimensioning of the railway superstructure, we adopt constant thicknesses for the layers, varying only the height of the reinforcement when necessary. This reinforcement will be necessary whenever the subgrade presents inferior characteristics to those of the final layer of the body of embankment. We can have several section compositions:

Taking the project axis, the typical sections, the finished ground and the surfaces (after cleaning), second and third categories, we sample the sections, taking care to show the body of the landfill, the cuts, final layer, refill, etc. See the Material List of the project axis:

Below, lined sections showing the various materials to be listed in the DDM program later:



Now, to model the earthworks distribution in the DDM program, we use the command DDMLINK and we selected the project axis:

Now, we fill in the data for each source and demand:

Note the Equation column in the sources tab. In it, double click with the mouse to open the equation editor. Notice that the word in braces is the same as that in Material List:

Note the equation. Note that I put a formula to avoid waste, so if the section area is insignificant, it does not count to the volume and also does not mask the initial and final station of the classified volumes.

There are situations where we model the hatches of the overlapping list material, for example:

Note that the Landfill hatch overlaps with the final layer hatch. This is because in the list material, the hatch definition does not take these surfaces into account, as it would be very difficult to do "Paste Surface" for each item:

Thus, to calculate the landfill area in Soil, we can simply, in the column of the equation Landfill:

See how the equation is: IF ({SLG-1:ATERRO GERAL} < 0.05,0, {SLG-1:ATERRO GERAL} - {SLG-1:CAM FINAL} - {SLG-1:ATERRO CAT3})

So, I eliminate the residual areas, which do not generate significant volume and also calculate the landfill area in soil.

The next step is to get the value of the areas of the lodged sections. By using the DDMLINK , is available at the top of the program screen, the button Update Areas. Important: Section Viewdoes not need to be drawn, but the styles of the materials has to be in visible styles:

Wait for the program to finish importing the areas. Once this is done, click the Rank Items button. Click the Validate button to check for errors in input data.

Now consider the steps to calculate.

Initially, we do not know if we will have more cut or more landfill. We do not know much how much bad stuff will we have.

Step 1 - Determining the volume of Dump Site

The first step in the calculation is to know how much we have cuts and landfills as well as how much of the cut material should be discarded.

This information can already be collected only by classifying the sources and demands. So do it. In the example provided, you have deleted the dump site and borrow pit, being only with the cuts, recesses and embankments obligatory, see:

Now note that when you click Rank Items, a message may appear stating that there is a problem with ranges. This error occurs because some source ranges destiny. In the case, as I have not defined where the dump site will be, these sources do not display values in the Ranges column:

And how to solve this? Begin by defining dump site as close to these sources as possible. Look at the start and end columns for the locations and look at the Volume column to know how much material will be discarded. Note that you should look at each source what the ranges are disposable.

After prospecting the dump site with compatible capacity, recalcule the areas with DDMLINK , click the button again Classify:

Note, the dump site may not always be in the position that the program defines. We can have several factors interfering, such as domain strip, preservation area strips, the topography itself, etc. Then choose the closest possible places. The ISF 211 - Earthworks Project has the indications of how prospect boot:

Particularly, I prefer the first option because it has very little influence on the landfill of the railroad. The second option calls for a study of additional stability, but may be more appropriate in cases where there is a service road for example.

There is no error message, but a undefined source appears:

Step 2 - Determining the Borrow Pit

In this step, after knowing where the dump site will be, it may be necessary to define the loans. Again the ISF 211 - Earthworks Project, has indications of how to look for Borrow pits:

The second option suits me better, if the required volumes are smaller. The second may be necessary if the requested volume is larger. But in this case, we must keep in mind that the "false embankment" will not have the compaction control of the typical landfill body. Then further stability studies can be requested.

In the design of this example, I used the first option, being careful to prospect loans where CBR and Expansion were acceptable and had no material in third category, since excavation is more expensive.

First, uncheck the Inhibit Indef / Fixed option. This will set zero cost (or DMT) between any demand and undefined sources.

Another consideration that must be made is that there are materials that, despite may not be used in some circumstances. For example, the material third, has high CBR and low expansion. It could be used in the final layer, but we do not want this and can not prevent the program from defining this because the CBR, the Expansion and Permeability of the third material is not editable (if we set the Allow third category Segmentation).

Click the Calculate Distribution button. You may need to click Rank Items before. The results will be shown but not yet finalized, as there will be demands with undefined sources. The next step is to do a analysis of the results.

Step 3 - Analysis of results

After the calculation is finished, look at the results sheet and see where there are indefinite sources:

By the Stepping Stone algorithm itself, the demands that are satisfied at zero cost, by balancing supply and demand. Then consider that the loans should be as close as possible to these demands in order to maintain the DMT low.

For a full review, see the analysis of results topic.

Step 4 - Reports

Finally, you need to generate reports. These reports need to show the worksheets with the areas of the sections, they need to show the distribution chart and also the summary table of the distribution. These reports are on the File menu:

For example, the cross-sectional area chart:

And also the distribution table, or QDT:

Finally we have the summary distribution table, or QRT: