Manure compost newspaper grass clippings and other organic materials can be good for this purpose.
How to fix erosion under concrete steps.
Use an ax handle or whatever and pack it up in there.
Mulching makes use of organic materials to do just this while adding nutrients back into the soil.
How to fill voids under a concrete slab.
Concrete is a very heavy material in addition to being unable to generate any upward pressure on the slab the added burden on the soil often speeds settling.
Drill at least four holes through the slab at a point that s centered on the void beneath.
Mix the concrete to a thicker consistency.
You can fill it with gravel or sand checking and repacking every few months or do what another poster said and call a mud jacking company to do it.
It looks like the problem is just that it was poured on top of the ground instead of being dug out a few inches and then being back filled after.
Bury an aluminum flashing or redwood or other suitable material a couple of inches deep and about an inch from the concrete edge allowing it to extend above the bottom edge of the concrete approximately an inch.
Use a hoe or fabricate a pushing stick and stuff the concrete into the crevice.
So the concrete is buried by a few inches.
Properly installed gutters and downspouts will effectively channel rainwater away from building foundations thereby minimizing erosion under concrete slab foundations.
Recommendations for installing downspouts state that they should channel water 5 to 10 feet from the base of the building.
Use a drill equipped with a masonry bit to bore.
It s surprising how many basement water leaks erosion issues and other drainage problems can be fixed by simply redirecting water from gutters and downspouts away from the house.
Connect a hose to a slabjacking pump then run the hose to the holes leading to the void.
Without the right support concrete will crack sink and cease to be the sturdy solid surface you can count on.
Erosion under concrete is serious whether it s your foundation driveway patio or sidewalk that s affected.
Sometimes a splash block or a short run of horizontal pipe drain pipe or pvc along the ground is all that is needed.
I would suggest packing dirt rock under as well as you can.
These simple methods can help you revitalize your soil repair damaged areas and prevent soil erosion in the future.
I would fill the area with concrete stone mix.
It s imperative to fix erosion under concrete as soon as possible but first you need to know what to look for.
To repair you ll need a form.
The grass will eventually fill in.
Then back fill a little bit with soil.
Shrub and tree roots excel in preventing erosion way better than grass roots.
The loose fill is susceptible to settling over time especially if it gets and stays dry which it will do under concrete sidewalks and porches.
