I want to place a permanent anchor for a slackline in my parents' backyard. I looked around at the different options, but I don't have access to some of them (e.g. no duckbill anchors), so I think I will go for the deadman anchor option as in this video.
I also found a diagram for what it should look like, but I am taken aback at the suggested trench depth of 3-4 foot.
I will be digging with a hoe and my own two hands. The soil where we live gets quickly into compacted clay, after maybe only 2 feet of something more humuslike - my father tells me he once rented an excavator to make a posthole and it needed over half an hour for that hole (operated by somebody experienced, not by my father).
So, I wonder if the diagram I found is not overly sturdy, and if I could get away with a shallower trench. Especially since this diagram also foresees getting concrete poured into the ground, and the person in that video gets away with just a buried length of pipe.
I found a slackline calculator and it says that the normal load will be in the 7-8 kN range, and possibly up to 11 kN under some circumstances (e.g. if it gets tightened a lot and somebody heavy tries to walk on it). So let's say I want the whole line to hold up to 15-17 kN just in case (that's breaking load, not nominal load). There is a tree to hold one side up. For the second side, if I bury a 3 feet long pipe with maybe 2 inches diameter, what depth should I choose?