Math question for any engineers out here

[trcothorn]

I’m in the process of building a parking pad in this spot. I ran a string line to measure my retaining wall height. If I have the line 3 feet above the ground and check the line for level, it is still just barely sloped back. I do not want to build a wall taller than 3 ft due to increase chance of the wall leaning or giving way. So I went inside the trailer with my 4ft bubble level and measured, if I rise the back of the bubble level 9.5 inches it shows level.

So my question is, for every 4ft there is a 9.5 inch drop. My trailer is 30ft. So do I divide 30 by 4, and times that by 9.5 to figure how to get level? Doing that tells me I need a 71 inch wall to get level. Am I doing this all wrong or over thinking it? Really would appreciate input on this my brain is hurting.

[DrewE]

It might be worth looking at building a strong deck/platform rather than putting in enough fill and retaining wall to make a level spot.

[schlep1967]

d3500ram wrote:
Thought experiment #3 with tongue dropped such that trailer is level.
All dimension are approximate:

Using this diagram, Back where the post is at the rear of the trailer build your 3 foot wall.
Then fill in to level.
Then put another wall behind the axles.
After the second wall is built you could fill in behind that wall at a moderate slope down to the first wall so you have something to put stabilizers down on.

[blt2ski]

I built my last RR/Treat lumber wall over 20 years ago. SInce then I have installed 1000's of sq ft of concrete walls. Including for a Class A RV parked closer to the walls you are doing.
As mentioned, even for that 4' wall, I used geo grid, every two layers of Allan Block wall in that case. #0K lbs Type A went thru the Nisqually quake here locally a year or two later.
There are lots of ways to do what you are trying to do. Even a 3 or 4' wall frankly needs some engineering help other than tire backs etc.

Marty

[coolmom42]

trcothorn wrote:
This is the set up I’m going for. Gravel base for drainage, deadman tee anchors for support. All that.

Not to be discouraging.... But in TN, those crossties will be termite homes pretty quickly.

[JaxDad]

wapiticountry wrote:
Harbor Freight will sell you a laser level for less than $30.00. Set the level at the front of the rig and using a two by four set perpendicular to the ground behind the rear tires measure how high the rear of the pad needs to be, skip the math.

Easier still. Take length of garden hose and fill it with water, holding one end of the hose a couple feet up against a board (the base end) at a known height (2 feet, 3 feet, etc) walk around with a tape measure and the other end of the hose (the roving end). Lower the roving end until the water is up to the open end of the hose. Measure from the end of the hose down to the ground. That length minus the height of the base end is the difference in elevation.

Water will always find its own level.


BTW, terracing the wall, go up 3’ feet, go in 3’, go up another 3’, etc, etc, and leaning the wall back into the slope will allow you to go up a lot more than a single height wall will.

[fred42]

This somewhat obvious suggestion may not be an option in your case. Can you rotate the pad 90 degrees to have its length across the slope instead of falling with the slope? This would turn a 72" problem into a 20" problem.

[time2roll]

Consider paving two strips for the tires down to some wheel stops and leave it on a slope. This will give traction for the tow vehicle and a positive stop for the trailer. +1 for doing this with some type of stone vs wood.

[d3500ram]

Thought experiment #3 with tongue dropped such that trailer is level.
All dimension are approximate:

[wr1032]

If I was doing this I would put two strings of perforated plastic tile up grade from parking area. dry ground will not move as fast as saturated ground. My two cents.

[wapiticountry]

Harbor Freight will sell you a laser level for less than $30.00. Set the level at the front of the rig and using a two by four set perpendicular to the ground behind the rear tires measure how high the rear of the pad needs to be, skip the math. Your photo seems to indicate about a two to three foot rise, not seven. That would make a pad easy to construct. Just use concrete "Windsor Wall" type blocks and fill in the space with road base.

[theoldwizard1]

If you are going to use 6x6 timbers, they had better be pressure treated. The key to your design is how are you going to anchor the deadmen into the exiting hill and how many are you going to install ! My guess is that you will need about 4 PER TIMBER !

One thing I did not see mentioned anywhere is a FOOTING ! Even with timbers, you should have at least 2 timbers BELOW GRADE. Driving large rebar through all of the timbers will help the deadmen.

Good luck !

[DougE]

Two thoughts - To level the trailer your pad doesn't need to be level (and it only needs to be long enough to get under the tires). Once the trailer is in place you can probably lower the front by at least a foot to level the trailer as most tongues are 18" high at the top of the ball (so you can reduce the height of the rear wall by 12"). If you do go for a pad that is sloped, put permanent wheel stops at the tires to ensure you don't back too far and go off the pad.

[Ivylog]

trcothorn wrote:
This is the set up I’m going for. Gravel base for drainage, deadman tee anchors for support. All that.

No way are going to back that long a trailer onto that pad on that slope. Maybe if you drop the hitch to the ground.
Agree something like Versalock wall blocks will last longer and can be built as high as you want to go.

[NRALIFR]

I would recommend checking out Versalock wall blocks as well. Used ties aren’t a permanent material like wall blocks are. I have several feet of retaining wall around my house made from these. The tallest one is about 7’.

For the height of the wall you’re considering, you should use the large size blocks that are about twice the size of what Lowe’s and Home Depot carry. The block face is 8” x 18”, and they weight about 90 lbs each. The caps are 4” x 18”. One of the nicest things about this type of retaining wall is that no special drainage pipe is needed behind it. Because it’s dry-stacked, the wall is porous to water.

:):)