Machine Foundation on Rock

[nevsam12]

The machine (motor and generator 40,000 lb each) will sit on a concrete mat approximately 3 ft x 16 ft x 26 ft. The pad will be sitting and doweled to the rock. 600 RPM each. High rocking torque but not much vertical/horizontal unbalanced forces. Actually, I plan to excavate rock 6 - 12" so that the mat footing can be locked into the rock for incresed damping. Resonamce should not be of concern because the rock natural frequency would be very high. Am I on the right track? Please comment and set me on the right track if I am making wrong judgments.

 

[msquared48]

I don't see anything shaky with your solution. Do it.

Mike McCann
MMC Engineering

 

[concretemasonry]

Should be no problem for the frequency and type of loads.

Even the foundation for a measly block making machine weighing only 35,000#, it is common use a 16x16x4 foundation because of the weight, relatively low frequency that varies on a 10 second cycle has been common used internationally unless there are unusual soil conditions (bearing strength and water table).

If you are anchored well, no problem.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[nevsam12]

Hi msquared48 and concretemasonry,

Thanks a lot for your taking time and answering. It means a lot to me because I do not any other resource with this type of background. This machinery was going to be located above a sandy soil with 65 - 85% moisture (quick sand condition), which was discovered only after boring was done. Rock was encountered at about 20 ft refusal. So all of the soil will be removed and machinery placed on a pad sitting on the rock.

Thanks again for your help.