My drain pipe is under the driveway. After failing to remove the blockage in the drain, my plumber is going to cut a hole in the driveway and do the necessary repair. And he suggested a new driveway afterward.

My driveway is cracked into several pieces and sunk in one area. Water forms a puddle there instead of sloping away from the garage. According to him, the drain pipe is damaged because the driveway gave in to the weight of the vehicles, resulting in the soil movement. This is where I would like to get your advice.

Question 1: Which is more likely reason for drain pipe damage, uneven settling of soil or the vehicle load? Had the existing pad been thick 6" with rebars (assuming existing 4" non-rebar), would it withstand vehicle load even if the substrate soil settled unevenly?

Question 2: If I do not put a new driveway, will the cracked pieces continue to sink under vehicle load, causing more damage to the drain pipe underneath? I will build up the low spot for good water drainage. This is the more pressing question for me.

By the way, there was a large oak (trunk diameter more than 1 foot) that I cut down last year. Puddle in the driveway was noticed earlier than the tree removal.

I cursorily checked the driveways in the neighborhood. None showed sinking. I am going to ask all my neighbors if they have experience a sunken driveway.

I live in Dallas. Soil is expanding clay type, I was told. Our vehicles are an SUV and a pickup. Thank you.

 

Thicker concrete is almost always better along with rebar. Most residential driveways are only 3.5"-4" thick, many don't have rebar or wire mesh.

I suspect your driveway was poured over unpacked fill which caused it to sink/crack. The odds are your driveway has sunk all it will be it's hard to say for sure. You'll probably know more once your plumber has cut out a section to make his repair.