[Kash2212]

Hi

Last August I set about laying my own driveway using block paving. The lawn area was excavated with a mini digger, 4-6 inches crushed rock was used as sub-base and compacted several times, before 1 inch sharp sand screed (compacted) to lay block pavers on. I using paver sand to lock pavers into place.

9 months on and there is some sinking visible on the side where the car is usually parked. It is not so bad when looking at it at any time other than when light falls on the area from a point close to the ground.

Could I have done anything differently to prevent this?

Is there a way I can rectify and set it straight

Photo attached day and night

Thanks

 

[Half-fast eddie]

That looks bad. Clearly a sign of base or sub-base failure. Is it wet there? Washing away the sand?

 

[Kash2212]

The area of max sinking corresponds to where the front of the car usually sits. Just your average hatchback, not even an 4x4

The drive is sloped towards the house with channel drains. Water doesn't particularly pool on the drive itself so im unsure why its sinking so much

 

[Nealtw]

Did you remove all the top and questionable soil? Or were you just going that depth and good enough?

 

[Kash2212]

Did you remove all the top and questionable soil? Or were you just going that depth and good enough?

The sod and top soil was removed down to the firm clay soil before sub-base was put down and compacted

 

[huesmann]

Exactly what materials did you use?

 

[notnew2diy]

The sod and top soil was removed down to the firm clay soil before sub-base was put down and compacted

Was the clay compacted?
Did you use a fabric over the clay before you added the crushed rock?
Did the crushed rock contain fines?

Good luck...Don.

 

[3onthetree]

I would expect a sort of "wave depression" for each tire track, not a "pothole" kind of sinking it looks like you have. So if you widened the driveway from before where you had to remove some sod, then maybe the clayey subbase you thought you dug down to was not undisturbed soil, but just some fill for the yard that was not compacted. So if you didn't compact the subbase, then this. The other things to investigate is the type/size/fines of gravel, whether the sand was coarse ("sharp"?), and whether your concrete haunch is failing to keep washout from happening.

 

[huesmann]

It doesn't sound like there is a concrete haunch.

 

[3onthetree]

It doesn't sound like there is a concrete haunch.

I see it in the photo holding in the left side.

 

[stuart44]

					Did the crushed rock contain fines? Good luck...Don. He probably used MOT type 1, which is 40mm to dust. Used as a sub base on roads. MOT stands for Ministry of Transport. It's usually a good sub base but it depends what's underneath.

 

[Thom Paine]

Caused by improper compaction.
which includes ..
product removed
product replacement
type of compaction equipment.

One should consult a soil engineer before attempting... saves time and money .

 

[huesmann]

I see it in the photo holding in the left side.

Hmm you could be right, or he could have piled up some of the gravel base along the edge. 🤷‍♂️

 

[Kash2212]

Process i used as follows:

• sod and top soil removed to about 6 inches. The clay soil was rather firm hence wasn't compacted at this stage.
• I put down landscaping membrane at this stage
• 4-6 inches of rock heavily compacted with compactor plate. I used MOT Type 1 which is approx 40mm used for roads.
• 1 inch coarse (sharp) sand screeded
• finally pavers placed in position

The free edges were haunched with mortar

It does rain 80% of the year here, situated on top of a hill approx 400m above sea level...

If you look at the photo taken during the day, or indeed at the problem area in person, you do see slight wave depressions and not a sink hole. The photo taken in the night accentuates the problem and makes it appear a pothole. But I wanted to check with people nevertheless to see whether they think this is 'normal' settling - it appears it is not!!

Below is the photo of the same area taken during the day...

 

[Thom Paine]

Process i used as follows:

• sod and top soil removed to about 6 inches. The clay soil was rather firm hence wasn't compacted at this stage.
• I put down landscaping membrane at this stage
• 4-6 inches of rock heavily compacted with compactor plate. I used MOT Type 1 which is approx 40mm used for roads.
• 1 inch coarse (sharp) sand screeded
• finally pavers placed in position

The free edges were haunched with mortar

It does rain 80% of the year here, situated on top of a hill approx 400m above sea level...

If you look at the photo taken during the day, or indeed at the problem area in person, you do see slight wave depressions and not a sink hole. The photo taken in the night accentuates the problem and makes it appear a pothole. But I wanted to check with people nevertheless to see whether they think this is 'normal' settling - it appears it is not!!

Below is the photo of the same area taken during the day... View attachment 695709

You need 90%+ compaction.. It appears you did not achieve that.