ORIGINAL:
I have about 1900 Linear Feet of perimeter around relatively flat farmland that I want to make it impossible for off-road vehicles to go through.
Installing over 380 bollards (at $300 each) would cost over $114,000.
One option I'm seeing is simply digging a ditch around the entire perimeter. A standard V trench probably won't be enough, so I was thinking of creating an "anti-tank ditch" instead which consists of using two bulldozers.
One bull dozer is inside the trench, and when it angles up with the excess dirt, the other dozer pushes the excess dirt toward one side. They alternate going front and back. You can see a demo video by googling "AEBV Kodiak's making anti tank ditch."
I thought of using HESCO barriers, but those are pretty expensive too and don't hold up well over long periods of time. Jersey, Concrete Barriers could be an option, but they are super expensive as well when including transportation.
Are there alternative options that I'm not thinking of? Do you see problems with creating a mini "anti-tank ditch"?
By 'off-road' vehicles do you mean 4x4 trucks or tracked vehicles; APCs and tanks?
For 4x4s, pour your own concrete bollards.
Dig a big post hole two feet deep, put knee high formwork over it, fill with concrete with 2-4 bits of rebar in it. About a foot square would do it. Space them every 4-5 feet.
Reuse the formwork, hold it together with ratchet chains.
Or use a backhoe to dig a trench and leave the spoil piled next to it. A trench on its own is easily bridged. Having a spoil pile the other side makes it more difficult.
Any ditch will need stabilizing long-term.
Looks like I could even purchase these Fast-Tube Concrete Columns, and then have a mixing truck come by and pour all the bollards at once. (I'll probably have to charge extra for the truck).
However depending on how bad local conditions are you might consider the old stand by of putting in a good fence. Yeah fences occasionally get cut of run down, but not commonly in most places.
An even older solution is to research how the farms used hedge as fencing before barbed wire was invented. In America Osage Orange was a favorite and the new growth would be woven Into the next tree each year until nothing can get through outside of large equipment!
I second the Osage Orange. It will not look out of place. If you have a row of concrete pillars in the middle of a field it will stand out. And for standard wood fence posts I go down 3 feet just for cattle fencing. If you pour any diameter concrete only 2 feet deep that can be pulled out with a winch or tow strap. Maybe even with a hi lift jack and straps between a few of the posts. All it takes is someone removing or smashing with a sledge hammer one of the posts. You can slow people down but you will not be able to stop them. Maybe a ditch and make a mound and plant a row of Osage Orange on the top of the mound.
So, probably need to have rebar that goes 3' into the ground, and a form that goes up 3'. To what width, I'm not entirely certain. Concrete Bollards sold online are about 10" in diameter.
These is no official bollard design - we use 4” PVC with concrete and a #8 rebar to protects transformer and mounting frames. Bthis is just to greate a crunch the driver will feel. If you want to stop vehicles you have to have a design basis threat - usually expresses as speed and gross vehicle weight- though you have to assume a bumper height as well. You also have to decide if you want to stop the vehicle or just disable it.. In the extreme, I know one facility that uses 10x10x 5/8” rectangular tubing concrete filled on 3’ centers. Lowest cost for is actually going to be highway dividers poured in place. Next lowest cost is to support Aircraft cable off fence posts ( 1-2 1/2 or 5/8 cables) tired to buried concrete anchors- this has the advantage of securing a gate with the same treat resistance. It’s not tamperproof though. It works even better on a chain link fence where the bottom of the fence is set in concrete.
Bollards are mostly useD when you want not to block pedestrian Or small vehicle traffic ( or flood water/ debris), or Want them removable. However they are highly tamperproof. Designing a single bollard to stop say a 40 mph dump truck Is very challenging.
Barbed wire fence and security system is the absolute cheapest, unless you own an excavator and can put in a trench.
But no barrier is effective if unmonitored. All barriers, from a simple to fence to the great wall, simply slow, and discourage intruders. Its the job of the defenders to actually STOP intruders.
And a trench can create its own hazard....depending on how its formed, you can end up with a fortified fighting position for attackers surrounding YOUR place. The same goes for walls, hescos, etc. Ff don't have a way to defend the wall itself it becomes THEIR wall, rather than yours.
I've put a great deal of work and though into designing my perimeter defenses. I use elevation and angles to my advantage so my walls and trenches give defenders cover but not attackers. Having a central tower helps a lot with this:
A simplification of the principle of my defenses, I'm on a hillside so obviously it would be different on flat ground but I hope you get the idea of how walls and trenches can work both with and against you depending on how you angle them.
Assuming each bollard is 10" in diameter and 3 feet high, that makes it 0.06060171010802469 cubic yards for each. Multiplied by 374 Bollards = 22.67 Cubic Yards, or 3 trucks.
So far, I'm calculating $16,984.50 in 13 Concrete trucks. This does not include Rebar, and the forms and Labor.
But considering that I will be bringing in the trucks one at a time, I can space out the project in 13 sections and do my own labor. That would be about 28 bollards per day. Assuming 5' distance between each Bollard, that would be a little under 50 yards per day.
I could drill the 3 foot, 18" diameter holes, preset the concrete forms in advance. Pour. Remove the forms after drying, and repeat 12 additional times on different days.
That seems quite manageable. and not too expensive.
Once set, there will be minimal upkeep, and I can keep those forms should I ever want to create more bollards for whatever other reason in the future.
When thinking about concrete costs, also consider that if the driver cannot just offload the concrete and has to wait or reposition his truck multiple times he will be charging by the minute to be there.
Have you thought about large rocks? Sometimes construction sites need to get rid of them. Sometimes landscape companies buy them other times they have to pay to dispose of them.
Another thought for stone is baskets. They make great wall/barrier structures. Have to consider the cost of stone but it will be less than forms and concrete for bollards.
For freestanding concrete bollards, they would need to be substantial if not encased in pipe. The concrete needs to be thick enough that moisture cannot penetrate to the rebar. It will rust, expand and blow out the concrete.
I understand that these concrete bollards I create, with the higher density concrete won't fully withstand a 50 mph car blasting through entirely, but it will give them a really bad time.
I may be able to go with a 2' footing instead due to the fact that the weakest point will most likely be the concrete above, rather than the footing itself.
For stopping potential, the circular metal tubes will win, hands down. I just don't know what reinforced concrete column, shear strength is.
The pictures of cars vs concrete columns looks promising.
Another option is perhaps for me to get a bunch of steel beams cut into 5'9" sections and then just plant them with a 3" brick to prevent them from touching the ground. Though, I think this won't work either due to overall rust issues.
how about a ww2 hedgerow? Some large rocks and a chain link fence down the middle. Hedgerows also had a earth berm component.
It could be argued that a hedgerow allows the enemy cover. That's true but in most real world sites there is always cover somewhere that can't be removed so a hedgerow can be constructed to minimize its usefulness to the enemy.
A hedgerow planted with very dense thorny and high plants would still provide the enemy cover but they could not fire from those positions.
A Hedgerow can be defeated with specialized equipment but it would be a slow process. It could be burned but that would still slow vehicles. Defeating a hedgerow would give up the element of surprise allowing the defenders time to mount a defense.
A side benefit is that a sniper would not have a clear shot into the compound. It would also slow unmounted infantry.
I have about 1900 Linear Feet of perimeter around relatively flat farmland that I want to make it impossible for off-road vehicles to go through.
Installing over 380 bollards (at $300 each) would cost over $114,000.
One option I'm seeing is simply digging a ditch around the entire perimeter. A standard V trench probably won't be enough, so I was thinking of creating an "anti-tank ditch" instead which consists of using two bulldozers.
One bull dozer is inside the trench, and when it angles up with the excess dirt, the other dozer pushes the excess dirt toward one side. They alternate going front and back. You can see a demo video by googling "AEBV Kodiak's making anti tank ditch."
I thought of using HESCO barriers, but those are pretty expensive too and don't hold up well over long periods of time. Jersey, Concrete Barriers could be an option, but they are super expensive as well when including transportation.
Are there alternative options that I'm not thinking of? Do you see problems with creating a mini "anti-tank ditch"?
Depending on the climate if try some trees and maybe a combination of wall / fence / trench. The trees provide cover to shield things from view. And they are useful later. Plus they look nice.
Even small trees and hedges can stop vehicles esp if you bury spikes in the ground in between the trees/ in the hedges or string wire etc. would you rather your enemy have to take his time going around an obstacle OR take his time fixing a tire or wheel then going around the obstacle.
Why not do something a bit more visually appealing and providing visual coverage for your property?
TREES! All kinds of dif lines can grow in a wide range of soils. When you look at digging basically a moat it could need major maintence and is going to cost thousands to put in. It also dosnt give a visual break from the outside in.
I bought 50 spruce trees this spring for $1.25 each. The more you buy the cheaper they are. The longer there in the ground the less maintenance they need. The best time to plant a tree was 20yrs ago..because they would be mature now.
How about 3" fence posts every 3' angled up o about 24" high with barbed wire, then plant the grass and don't cut it I don't know many trucks,atvs with more than about 18" clearance
Go to your local rig shop and order 2k' of 3/4+" galvanized cable. Pour some concrete "posts" every 20' or so (or closer if you want to do the extra work) and tension the cable between them at waist height. Without a grinder or cutting tools, they wont be driving through it and it could be done relatively cheap.
Spray the cable down with waste oil a couple times a year and it'll last forever.
Build a barb wire fence using used electric poles as posts. Space the posts so they are narrower than a typical vehicle. Put up as many strands of wire as you see fit/can afford.
Check out craigslist/marketplace for deals. Locally there is a guy selling 5/8 cable $25 for at least 80 feet but when unrolled the shortest roll was 120 feet. With some searching and imagination you could probably find deals like that to build your fence.
Hire a bulldozer to dig a ditch and put the dirt in a mound on one side of the ditch, start planting trees on the mound. Eventually the trees will grow and provide a pretty substantial stopping ability, In the mean time put a fence on the mound or store your scrap iron there.
As long as I put some spacing between the cyclone fence and the wire barrier, it looks like it should work pretty effectively. I don't know just how fast a car driving over farmland can get to.
They are saying "Up to 30 ft. Post Spacing" So this could be very cost effective.
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