Concrete steps that have begun to sink pose a problem when it comes to repair. The reason the steps are sinking is that the subgrade beneath the steps has eroded. This can come from the influence of a high water table or from the subgrade not being properly prepared to withstand the weight of the steps. The problem is that most concrete steps weigh at least a ton, and you have to get underneath the steps to make repairs. It is a doable project, but one that requires the rental of a lifting machine and extreme caution.
Dig out all around the concrete steps with a shovel. You will want to create a trench that is a minimum of 12 inches wide and as deep as it takes to explose the bottom of the concrete steps.
Drill four holes into your concrete steps with a hammer drill. You will want to place two holes on each side of the steps. Imagine that the side of the concrete steps is divided into thirds; measure and mark where these points would be. On the two lines that divide the step into thirds, drill a hole halfway between the bottom of the stairs and the top of the step or landing.
Drive a concrete colt sleeve into each hole. Hold a short piece of 2x4 over the end of the sleeve and strike the wood, not the metal, with a hammer to drive it in. If you strike the metal of the sleeve you could bend the ends of the sleeve and your bolt would not fit.
Screw your eye bolts into the holes you just drilled. Stick a short piece of rebar through the eye of the bolt to form a handle and make it easier for you to screw the bolt clockwise into the hole.
Remove the bolts from your shackles by turning it counterclockwise until it comes free and pulling it from the shackle. Hang the "U" part of the shackle through the eye bolt. Do this on all four eye bolts.
Hold one end of one of your wire rope cables so the eyelet is against the eye of the bolt and pass the bolt of the shackle through the shackle so if you pull the cable forward it is caught on the bolt of the shackle. Tighten the shackle bolt by turning it clockwise. Do this with all four cables.
Lower the rigging on your lifting machine so it is centered on the stairs and all four of your wire rope cables can be connected to the rigging. Connect the cables. Slowly raise the rigging on your lifting machine (consult the operator's manual for the correct procedure) until your concrete stairs lift off the ground. Once the stairs have lifted, pull them out of the ground and swing them away from the area. Lower the stairs onto the ground so they are out of your way--and you out of theirs.
Remove the subgrade that was beneath the concrete stairs by digging it out with a shovel. Dig down an additional 10 inches below the old subgrade.
Shovel 10 inches of pea gravel into the hole so the bottom is evenly filled. This will provide drainage for your subgrade.
Add fill dirt to the hole and use a compactor or hand tamp to compact it. You want to refill the hole so the new subgrade is at the level of where the bottom of the stairs will rest. When this is done, lower your stairs back into place. Remove the wire ropes and then the shackles, unscrew and remove the eye bolts. Mix a small batch of cement and patch the eye bolt holes. Fill back in the earth around the stairs.