Using Excavator as Resource in Primavera

Easy, excavators shall be resource leveled [a no brainer], production rate and volume of work shall determine activity duration [a no brainer], can be shared to work as independent teams if there is room for more than one excavator working on the same activity at the same time [a no brainer].  It is how it is done at the jobsite so your model shall mimic this and more complex assignments; it is just a matter of knowing how to use your software.

As always good advice from Rafael which works if the spoil is disposed in stockpiles within reach of the excavator.

If otherwise an excavator can only dig as fast as the disposal trucks/scapers/conveyor belt etc can take it away.

For a large earthmovement operation this requires the calculation of an average mass haul matrix and there are not many of us left who know how to do that.

Mike you are 100% correct.

The model is simplified for illustration purposes.

Earthmoving resources work as a team and the production rate is frequently that of the resources as group [multi-resource], not as a sum of the individual resources.  You shall model each team [group of resources] as a multi-resource within a Skill, each with its own production rate rate as a group [a no brainer].  In this way the available resource group [multi-resource] will be assigned based on common skill and the activity duration adjusted accordingly.

Among the variables to consider are the production rate of the excavator(s), the size and number of trucks, the hauling distance, space considerations at loading area as well as at unloading area and a few other considerations. Any person with basic knowledge of earthmoving would be able to balance the work and correctly determine the production rate of the crew(s).  Ideally there shall be no over/under capacity of any resource.

In the case of the Retention Pond each team [team 1 and team 2] shall consist of the excavator, operator, trucks, drivers and spreading plus compaction equipment at the haul site.  In this way when the second team becomes available to join the first one all resources will move with it and the resource leveling will take into consideration the availability of each individual resource that make up each team.  No scheduler, no matter how rookie will delay such an activity if it can start with only one team. No scheduler will not add the second team when available, a no brainer no matter how rookie the scheduler is.

If the whole crews are not shown the model is incomplete, will not be transparent and might be in error because of potential omissions when resource leveling. Keep in mind that for a schedule to be feasible all resources must be leveled.

Shortcuts are no excuse, good planning and resource modeling require all relevant resources to be loaded and leveled.

Modern scheduling software shall allow you to model this scenarios as well as more complex, it is a matter of knowing how to use your software.

I consider mass diagrams good for the slide rule era, not good enough for the computer era where 3D earth modelers can be run on a laptop and are superior.  Mass diagram is better suited for road construction. There are many road construction situations for which the mass diagram is not suitable. These include situations when haul costs are not directly proportional to distance, and situations when soil characteristics vary along the highway.   

For scheduling earth moving a practical approach is to divide the area into smaller cut/fil/waste/borrow areas and plan for the sequence and direction of the hauls. For road construction stations are used for identification of cut/fil/waste/borrow areas while for other scenarios some identification of the areas must be defined.

Carlson Takeoff is a cut/fill volumes and data prep (for layout or machine control) program that can estimate jobs using paper plan digitizing, PDFs, or electronic CAD files.

Carlson Takeoff Cut/Fill Movement command optimizes earth movement from cut to fill between existing and design surfaces. The earth movement is reported separately by haul ranges which is useful when using different types of earth movers such as dozers and truck/shovel.

http://www.carlsonsw.com/solutions/construction-excavation/takeoff/

http://files.carlsonsw.com/mirror/manuals/Carlson_Takeoff_R9.pdf

Even if you just have a single cut area and a single fill area, no unsitable materia  to be disposed, the volumes are balanced, the slope and soil characteristics the same the haul distances still do matter. Sometimes you just push the dirt with the bulldozer. The economic haul or push distance for a bulldozer with a straight blade is from 17 to 90 meters depending on grade. Pushing dirt up-grade is not efficient.  As the haul distance increases/decreases the number of trucks must be increased/decreased to keep efficient use of the resources.  If you do not increase the number of trucks when required the earth moving will slow down.

There are no shortcuts to good planning, moving of dirt is no exception.