bought my box when pvc pipe manufacturers were making 12 1/2' lengths....16' box, things were cool....now, they're making the pipe 14'...hate buying new box, been thinking about putting 2' extension on back of box, any of you done this?
I dont think this is a battle you want to take on. It will require a structural engineer to design, a certified welder to build it, and then someone is going to have to test it. It will probably be easier on the wallet to buy a new box. I say this because if something happens with the box where someone gets hurt, the lawyer is going to go after the trench box company first. When the trench box company sees what was added to the box, they are going to say, not us, we didnt add that on, then its you whos on the hook. That being said, something ive seen done in bad ground is to weld a plate on the back of the box. It would keep anything the collapses around the back of the box out. Not sure how much it will help you though
just get a 8 by 20 or a 8 by 24 and be done with it...
Be cheaper than all the certified engineering and welding. My unions training center has two boxes. 4x16s. They flip one over and pin it to the other to practice "stacked boxes." One of our wonderfull "brothers" used the bucket of a 320 to bash the box to the bottom of his ditch. Trashed the knife edges on the box. The training center found out it is cheaper to buy a new box than it is to fix the broken one