Conc. Pavement Undermining Eval.

[Busman]

I recently performed a general evaluation of a large concrete parking lot (xp joints at 40' 1-way, control joints at 20' e.w.)to determine the cause of cracking/ spalling near expansion joints.

An ~2 sq.ft. collapsed section near (~20') the lot's earth drainage swale revealed an approximate 2-3" soil void under the reinf. 4-5" thick slab (6x6 WWF pretty much placed on the soil with little cover of course). My tape extended at least 5 ft under the slab. Site personnel reported that in the right light, the void continues indefinitely, water can be seen flowing under the slab in this location during storm events, and cracked sections throughout rise and fall during storms.

I know the cause and will propose a full evaluation including multiple cores. Any other creative suggestions for investigating the extent such as sounding, GPR? How about repair methods such as localized grouting under slab, short wall under slab edge along drainage swale?

Suggestions and comments appreciated, just cause I like to learn!

young engineer, soon to take PE exam, finally.

 

[ACtrafficengr]

The first task is to find out where the water is coming from, and use some combination of interceptor drains and cut-off walls to redirect it. The deeper the cut-off wall, the more it will impede water flow.

Good luck with the exam!

 

[dicksewerrat]

You could use 'mudjacking technique' to fill the voids. Neat cement grout is good.