"No dig" Trench-less Technology

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I hadn't heard this term before so I looked it up: https://en.wikipedia.org/wiki/Trenchless_technology. Now that I know what we are talking about:

I did a job where we used horizontal boring to run under a very wide driveway. We dug out both ends of the pulled in pipe so we could direct it into buildings on both ends. The inspector looked down into the (small) trench and saw how deep the ends were and assumed (as I did) that the bored pipe was the same depth.
 
I was asked to recommend a company to inspect an underground feeder installation that's about a 150' run, they're using a trench-less boring machine and I was curious how they'll confirm the depth. I was guessing that the machine logs some sort of a gps report of the install, but I'm just guessing and thought I would ask.
 
Directly behind the cutting head of the directional drill is a transmitting sonde. The locator on top of the ground receives this pitch and roll information and is able to calculate the location of the cutting head. There is a continuous readout on the drill. Newer rigs have a computer program that will produce a finished plot of the bore. Older rigs have to plot the bore manually. But the depth can be calculated within an inch or so. A standard sonde is good to about 35 feet of depth. A high powered sonde is good to about 75 feet of depth.

i use a digitrack mark 3 system on my Vermeer 7-11 drill. I bought it used. Paid more for the locating system than I did for the drill itself.
 
Dzboyce said:
Directly behind the cutting head of the directional drill is a transmitting sonde. The locator on top of the ground receives this pitch and roll information and is able to calculate the location of the cutting head. There is a continuous readout on the drill. Newer rigs have a computer program that will produce a finished plot of the bore. Older rigs have to plot the bore manually. But the depth can be calculated within an inch or so. A standard sonde is good to about 35 feet of depth. A high powered sonde is good to about 75 feet of depth.

i use a digitrack mark 3 system on my Vermeer 7-11 drill. I bought it used. Paid more for the locating system than I did for the drill itself.
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So there is a report to show the inspector or it depends on your equipment?
 
As mentioned they have tracing abilities on the boring machine, not only for depth but horizontal location as well. They are constantly monitoring where the head is and "steer" it up, down, left, right as they bore the path.

As far as inspector goes, they need to learn to trust these guys to some extent. Give them the benefit of the doubt until you do have verification they are dishonest. If not you are going to have to be there to witness install, and even then you only can see readings on their instruments and not actually see the item itself.

Guys that do this kind of install show up with $1M or more worth of equipment and have a lot of overhead costs, they are not same caliber of contractor as unlicensed and dishonest trunk slammers for the most part. They can make mistakes but generally are not trying to deceive anyone.

Depth can be verified after the fact with locating devices if absolutely necessary.
 
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Here’s info on DCI’s borepath logging software

https://digital-control.com/log-while-drilling

with my older system, I record the depth manually. My drill rods are 6 ft long. While I have a continuous readout at the rig of pitch and roll, I have to use the walk-over receiver to get depth. That is done at each rod connection, which for me is every 6 feet. The walkover receiver gives me Actual location of the sonde and depth to the 1/10th of a foot.

if the ground conditions are the same, it’s actually easier to bore deeper than it is only 3 feet deep. I’m more likely to bore and install conduit 10 feet deep instead of 3 feet deep.

My size machine is ideally suited for the 50-250 foot bores. Like from an alley to the house, or across a parking lot. Or across a road. I’m usually going to bore a 4 1/2” hole and pull 2” or smaller conduit back thru it. Don’t know if I could bore a 10-12” hole to pull 6”. I’d be better off subbing that out to someone with a bigger machine.
 
It’s interesting though. My electrical inspector says I can’t backfill an open trench with conduit in it until after he’s inspected it, and approved it for cover. But if I bore it, all he can see is each end, and he’s happy.
 
RAKocher said:
I was asked to recommend a company to inspect an underground feeder installation that's about a 150' run, they're using a trench-less boring machine and I was curious how they'll confirm the depth. I was guessing that the machine logs some sort of a gps report of the install, but I'm just guessing and thought I would ask.
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Just a random thought, we could run our locator over it when the inspector was on site, since it gives depth readings.
 
Cow said:
Just a random thought, we could run our locator over it when the inspector was on site, since it gives depth readings.
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And he can only assume what it displayed is correct, and that you are using it properly.

Some inspectors are drunk on authority is the bottom line. Somebody that seems to do things correctly, you have to give them some trust on some things. Once they prove they are deceptive then you can ask to see everything - just my thoughts on how it should work in most instances.

You want to inspect something I buried in some of the sandy soil around here, you better be there when it gets placed, sometimes the trench caves in within minutes after placing it in the trench, sometimes it caves in before you even get it placed in the trench and you need to dig it out again. Still want to measure depth, in the sand is easy to push a probe into the ground and feel for the item you are measuring depth of, though you kind of need to know location of where to push probe into the ground.
 
181128-2248 EDT

What is the theory of operation of the depth measuring system? I assume it is a sonic method, but what is the basic mechanism?

If you insert a conduit is it usually plastic?

I believe sound propagates thru the earth at about 6 to 8 kilometers per second. 3280 ft = 1 kilometer, or about 23000 ft/sec for velocity. Thus, 1 foot of travel is 43 microseconds.

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Fulthrotl said:
i've seen it verified when they hit an 12" fire main, 4' deep.

the water squirts up between the asphalt and the curbing,
all around the parking lot, as it floats the asphalt, and turns
the ground under it to mud.

it's a pretty clear indicator.
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California version of a Chinese ? drill. Or fire main drill.
 
181129-1113 EST

A comparison of sound wave propagation is provided at:
https://en.wikipedia.org/wiki/Speed_of_sound
Sound travels much faster in earth than air.

I take naps flat on my living room floor with just the padding, carpet, and an overlay rug under me. Side point --- I think this has greatly reduced my back problems.

There are times when I think I feel the floor shake, could be imagination, but I don't think so. So am I sensing a far away earthquake, or local construction? We are not in an earthquake zone.

I was at the Yokohama naval base one night and woke up to the windows shaking. Quite obviously an earthquake.

I need to attach an accelerometer to my floor and record vibrations.

When you have a change in medium, earth to air, or air to glass, and a wave propagates to that interface a reflection will occur. Some energy passes thru and some is reflected. Radar, sonar, and your image in a mirror are examples. So is the device in the boring tool sending a sound pulse and measuring time to a received reflected signal, or is the signal receptor at the earth's surface?

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