[crazygringo]

A++ for creativity! (But still no.)

It makes me wonder: all underground power lines are still laid by digging up the ground, laying them down, and then filling the dirt back in. Which is super-expensive. Right?

Are we trying to develop any technology for "microboring" in tunnels through dirt and clay, and maybe bedrock when occasionally necessary? E.g. just a two-inch diameter tube or something, that's even able to go underneath rivers and things? Solely for laying underground wires?

I dream of a world without electricity pylons...

[toast0]

I don't follow trends for electrical lines, but directional drilling/boring is definitely a thing for fiber optic communications cabling, and trenchless pipe bursting is pretty common for sewer replacement projects.

Underground electrical lines are a lot harder to access for maintenance and monitoring though; that expense isn't going to go away if you install without a big trench. It's usually a good idea to ensure access above the underground run, and if you're going to clear the land to ensure access, it's not that big of an additional step to do traditional trenching for installation.

[quickthrowman]

> I don't follow trends for electrical lines, but directional drilling/boring is definitely a thing for fiber optic communications cabling,

I run electrical work and sometimes use directional boring to run underground conduits, it really depends on the pathway your conduit is taking. It boils down to whichever costs less, digging and restoring two pits and directional boring, or ripping up and restoring a surface so you can trench and backfill. If it’s all green space, plowing/trenching wins every time. Once you start crossing sidewalks and driveways and so on, directional boring tends to be cheaper.

[quickthrowman]

Directional boring exists but it’s even more expensive than trenching and backfilling. It’s typically only used when disturbing the concrete/asphalt/subsurface utilities and then restoring them is more expensive than directional boring.

https://en.m.wikipedia.org/wiki/Directional_boring

[ortusdux]

I've wondered if there was some way to replace sidewalks with pre-cast sections that would allow for utility runs. Maybe something the size of septic tanks, with a removable lid that doubles as a sidewalk. I'm sure there are some significant practical limitations I am ignorant of.

[quickthrowman]

> I'm sure there are some significant practical limitations I am ignorant of.

Yes, the steel framing or reinforced concrete panels that would be needed to hold up the precast concrete sidewalk would be very expensive. You don’t need the entire conductor accessible anyways, that’s what tuggers and mule tape are for, pulling wire.

Also, all of the pipes would need to be supported from the underground concrete/steel structure and you would also need a lot of (expensive) expansion joints. Laying pipes in the ground and burying them lets the earth support them instead of pipe hangers.

There are some colleges/institutions to do use tunnels to run steam pipes through a campus, and they tend to build purpose-built tunnels for those. I’m not a pipefitter, so I’m unsure why steam pipes get their own tunnels, perhaps a MechE or pipefitter can weigh in!

Underground electrical feeder conduits (on customer premises, I only deal in the electrical world beyond the utility transformer secondary) are typically run in concrete encased ‘duct bank’, with manholes every so often. Electrical vaults/manholes are available as precast pieces that you simply lower into place.

Precast electrical vaults: https://www.ecbabbert.com/utility/electric-structures/electr...

[bunabhucan]

The big ones get cooled with oil and are typically in ducts in concrete. You need to insulate from the voltage and cool it. Air does both, albeit with lots of distance for higher voltages.

[crote]

Horizontal directional drilling. It's already being widely used in urban areas, but digging a trench through some farmer's field is still vastly cheaper.

[pram]

Google uses “microtrenching” to lay fiber, so it’s definitely already a thing in places where there’s already infrastructure.