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Tunnel Job?

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  • Tunnel Job?

    When I first moved to Texas and heard of all of the foundation problems, I couldn't believe it. After living and Plumbing here for almost 10 years, I still can't believe it. The Ground moves so much. Most houses are Slab with Post tension cables. It is not a matter of if you will have foundation issues, but when. There are a lot of companies that Tunnel from the outside in. I thought this was crazy and I have not been offering the service, but after talking to several engineers, I have started to come around. I have been in a few tunnels, dug by other companies, but have never dug one myself to the extent of this job I just got. We have an engineer involved, permits, and everything. Both are required here whether tunneling or Jackhammering now. I wanted to jackhammer, but the homeowner doesn't want it and has several friends that have had the tunnel done. Any thoughts or Questions? Have you done this before? It is a Sewer repair on a 3x2 fitting 10 feet under house. Pictures and video to follow. Should start next week.
    "don't put that in your mouth, you don't know where it's been"

  • #2
    Re: Tunnel Job?

    Never heard of tunneling under a house...it's a different approach I guess. Not sure how you can backfill in 6" lifts when you're under the problem, unless I'm not understand your premise.

    However, I'm not sure I would ever entertain that idea regardless if there is an engineer involved or not.

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    • #3
      Re: Tunnel Job?

      funny you mentioned this today. i just had a call from a manufactures web link about a blind bore for a 2'' waste and 2- water lines about 10' inside a kitchen on slab. spoke to the caller for about 20 minutes and told him to saw cut if it's not post tension. plus he's about 60 miles away and i'm not interested.

      several years ago i did a blind bore with 2% grade at a medical center and nailed it. got lucky and worked great. water jetted to bore and set grade. then pulled it back with the hydro drill and paddles.

      rick.
      phoebe it is

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      • #4
        Re: Tunnel Job?

        There are a couple of ways of doing it. You can use a powder puff (air stick tamp) or I found out I can buy a tamp to go on the end of my Hilti 1000. The other way is to leave the void and install a pump. The engineers say that there are always voids under slabs. If the tunnel is started in the approved area and maintains the 3 foot square, that there is no need to backfill. It is the craziest thing I have ever seen. I will post a video when we are done. I plan on compacting dirt back under. I don't like the idea of leaving a tunnel. Seems weird to me.
        "don't put that in your mouth, you don't know where it's been"

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        • #5
          Re: Tunnel Job?

          We use our air tampers a lot and they are designed for vertical operation they do not hit very hard on a horizontal. But some compaction is better than none lol
          Seattle Drain Service

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          • #6
            Re: Tunnel Job?

            will a slurry mix pumped in work?

            rick.
            phoebe it is

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            • #7
              Re: Tunnel Job?

              Originally posted by PLUMBER RICK View Post
              will a slurry mix pumped in work?

              rick.
              God damn rick is on the mark again.

              Liqid-fill. 2% fly-ash, supposedly cheaper than stab-sand. Easy to break out too. just lag your pipes for expansion.

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              • #8
                Re: Tunnel Job?

                We own an Eichler home,slab on grade. One side had settled down 3 1/2" . This was the result of broken clay tiles not carrying away roof water. I excavated full length under under
                grade beam. Put in temp. mud sill slowly jacked up level with My 50 ton jacks. drove chance helicals to refusal. welded them to 3/8s x 3"x6" angle epoxied into footer. Then cranked up radiant boiler. Using My ray tech. lazer therm. located 3/8" copper in slab. core drilled between and pumped in Fly ash grout. House level. Structual Eng.that signed off on it said " If I didn.t see this ,I wouldn't believe it " I had a good education in Pile Drivers Local 37 .Hope this helps someone. Tool
                I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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                • #9
                  Re: Tunnel Job?

                  Engineer says that we need to compact dirt with tamp. He is looking for %90 of the dirt to go back in. I have looked into the slurry before and unless you are going to use a foundation company that has a large pump system (called mud jacking) then it is pretty much useless. Several engineers have argued that the slurry is in effective, because it will still shrink. We start Tuesday and I will try to have video and pictures up as fast as I can.
                  "don't put that in your mouth, you don't know where it's been"

                  Comment


                  • #10
                    Re: Tunnel Job?

                    Originally posted by Plumbingbyjay View Post
                    Engineer says that we need to compact dirt with tamp. He is looking for %90 of the dirt to go back in. I have looked into the slurry before and unless you are going to use a foundation company that has a large pump system (called mud jacking) then it is pretty much useless. Several engineers have argued that the slurry is in effective, because it will still shrink. We start Tuesday and I will try to have video and pictures up as fast as I can.
                    from My person experience , I don't agree . Our floor is nuts on no cracks after 10 years. I Had a pumping co. pump all the fly ash grout in ! Most Engineers are heavy on theory and Light on practical experience.
                    I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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                    • #11
                      Re: Tunnel Job?

                      If slurry shrank it would not be allowed by cities as the approved backfill for excavation in streets.

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                      • #12
                        Re: Tunnel Job?

                        Originally posted by drtyhands View Post
                        If slurry shrank it would not be allowed by cities as the approved backfill for excavation in streets.
                        New Engineer. You may have to use a heavier stabilised sand or otehr but generally we havent seen shrinkage with slurry. When we want to p-off the council when they are doing the reinstate of the pavement we crank up the % and they get p-ed chipping out. LAst one the lazy bs' were lucky to mix 75mm concrete to replace 180mm we pulled out. Need to get the right Engineer who actually knows his game

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                        • #13
                          Re: Tunnel Job?

                          Look for an Eng. with calloused Hands !
                          I can build anything You want , if you draw a picture of it , on the back of a big enough check .

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                          • #14
                            Re: Tunnel Job?

                            Slurry is heavy and as a result I have seen some occasions when a jacked slab has sunken again. Usually they didn't fix the real cause of the original problem. Now days Special polyurea Foam is being used to jack concrete and fill voids. Helical piers are just plain badass!
                            Seattle Drain Service

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                            • #15
                              Re: Tunnel Job?

                              Ok, We finished the Tunneling job. Everything went as planned except the Backfill. We got it to 94% compaction, but it took a lot longer than we expected. In regards to the slurry shrinking comments. I agree with the slurry not sinking. It is the dirt below the slurry that they says shrinks. The compaction under houses is not the same as for a street. Most of the house here, the dirt is just pushed up with a skid steer and ran over a few times. Foundation problems are everywhere, because I see no one doing them right. Engineered post tension slabs work best, when the Engineers instructions are followed. Click here for the Video of our tunneling job:Tunneling job www.plumbingbyjay.com - YouTube
                              "don't put that in your mouth, you don't know where it's been"

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