Road foundation capacity under trailer load

[USER10]

Hello folks

i was checking if a road segment recently built can carry the loading of a temporary trailer (100000 pounds) without problems. The road is : Asphalt concert layer over granular base layer and sandy Subgrade materials both compacted to min of 95% Modified Proctor.

From the configuration of the trailer, i found that the worst loading scenario (highest surface pressure on the road) corresponds to a load of 50000 pounds over 2 foot by 2 foot concert pad, resulting in contact pressure of 100 psi.

My recommendation was( based on judgment) that the bearing capacity of the asphalt concert layer and the compacted granular base and sand subgarde underneath are likely much higher than the contact pressure of 100 psi. The settlement under such pressure should be small (less than 10 mm) and mostly elastic.

Just want to make sure that i did not miss anything . Any inputs please?
Thank you very much for your help

 

[Ron]

Pavements are designed for repetitive loading, so a "one off" loading can often be tolerated. How thick are the layers of each section? Since this is a temporary loading, I would check the stresses in each layer using elastic layer analysis.

 

[USER10]

Actually.. i am more concerned about the bearing capacity and deflection under the heavy trailer load ( which is supposed to be very occasional). Load repetitions from the trailer or other traffic should be very small sine this is only short term ( couple years ) road. Hope i did not miss anything in my above assessment.

 

[oldestguy]

Those loads do not sound particularly bad. Many a truck has 100 psi in the tires.

 

[USER10]

thanx oldestguy ..please note that the contact pressure may be the same as what we see under heavy wheel truck but the contact area here is almost double ( the magnitude of the load is almost double)

 

[Ron]

Wheel load on the pavement and tire pressure are not the same. You can have a wheel load on the pavement of 5000 lbs and a wheel load of 10,000 lbs, both with the same tire pressure.

Unless the trailer will be sitting idle on the pavement, I would not be greatly concerned about bearing. You do need to be concerned about two parameters....lateral strain at the bottom of the asphalt layer and vertical deflection at the top of the subgrade. The lateral strain parameter controls fatigue cracking in the asphalt, while the vertical deflection in the subgrade controls rutting.

You have not provided the wheel loading, the wheel spacing, and the layer thicknesses of each layer along with a characterization of the materials. Without those, any advice we give will be speculative and perhaps not accurate.

 

[USER10]

Ron.. Yes the fully loaded trailer will be sitting idle on the pavement and from the configuration i could see that the worst loading was not the the wheel but a pad (one foot by one foot) that will be loaded with 50000 pounds.

 

[Ron]

Check each layer for shear failure. Also check the rheology of the asphalt layer as this will be an issue during warm or hot weather.

You will need to provide dolly pads under the foot to spread out the load. You could also consider replacing a strip of asphalt pavement with a concrete dolly strip.

 

[EireChch]

USER10 - 50000 pounds over 1' x 1' pavement is an applied pressure of 2470kPa (358psi). Are you sure thats right?

As Ron has said, I think you need to spread that load over a larger area as it will likely cause shear failure and ruin your pavement.

You may need to look at a 3' 4" (1m) square concrete pad to get the applied pressure down to about 222kPa (32psi), or something where you will not be concerned with damaging the pavement

 

[USER10]

Thx EireChch
50000 pounds over 2 foot by 2 foot concert pad, resulting in contact pressure of 100 psi