I wanted to run this by some of you old "pipe hands" out there. Specifically, i'm interested in the cost/benefit related to excavations for pipe work (eg, water, sewer, storm drain). Do you guys have a rule of thumb (or preference even) to your backfill operations? The following scenarios are most common in my mind (i'm not recognizing the "push dirt in trench and drive over with machine tires" method for purposes of this thread!): 1. compaction of backfill via excavator or backhoe with plate or sheepsfoot 2. compaction of backfill via trench roller or possibly ride on roller for larger , wider excavations. I recognize other systems, but wanted to get feedback on the above two situations if possible. Specifically, do your firms have a break point when usings system 1 vs. system 2? Tons of variables related to this i realize. In my minds' eye, if i can get an excavation wide enough for a given depth, i'd like to get a sheepsfoot ride on roller in the trench (for high PI material) in lieu of the backfill trackhoe as i expect that the cost of a second excavator for backfill work is pricey. Also begs the question: Have you ever placed a ride on roller in a trench deeper than the 5' OSHA shoring requirement w/o sloping sides or benching?
We use method 2 almost exclusively. The pipe crews have an excavator, track loader with forks and a small roller - 48". The excavator and ditch man plus helper opens trench and lays pipe. The loader operator keeps stone in the box and backfills the trench. Either the loader operator or helper runs the roller in the trench for backfill. Usually the excavation is 6' or less so it makes sense production wise to lay the trench walls back instead of using shoring. The loader operator can get into the trench and cut what he needs to get the loader and the roller into the trench. Most specs call for a stone bedding 6" under and 12" over so usually backfilling is easy - unless is it very rocky soil. I have seen a rock be driven through 12" of #57 stone and damage C900. System 2 seems to work better for us without adding another excavator for backfill and compaction because you still need a machine to load the stone box and carry pipe/manholes.
We use a wireless remote trench roller. We are only a 3 man crew. One excavator trenching, another backfilling and helping the pipelayer and a pipelayer. We are able to run a small crew yet be effective. The pipelayer just runs the trench roller from inside the box while I am digging the next section of pipe. At 12' deep with a 200 size hoe, we are getting about 10 pipes a day.
I use a backhoe or excavator with a compactor depending on the depth of the pipe. The deepest main I have done was 25 feet deep. I always found the backhoe or excavator compactor to be better.
We have always used a loader for backfilling and had a the helper do compaction with a reversable plate compactor. When the loader isnt backfilling it would be staging pipe with the forks so the hoe could just sling it and swing it in the trench. Sorry Ive never done option 1 before so Im not really able to compare the two. If you were going to use the plate on a hoe I imagine you would want a plate and bucket set up that one guy could swap between very easily. One way around that would be using a hoe with the remote trench roller it seems like it would work really well. That way the guy in the hoe could backfill and compact with out having to switch between a plate and a bucket.
we've always pulled boxes, kept excavation as narrow as possible, and compacted w/2nd excavator with either sheepsfoot/vibrator plate. we're so busy, that we added a 2nd crew putting in nothing but 17000' of water main at an ethanol plant, deepest cut being 8' deep. we decided we'd try the widen the ditch out, and run a combo of a ride on roller, and wheel loader to backfill. we've only been at it a week, but my conclusion so far production wise is, keep it narrow, used 2nd excavator
For clarification, we leave our trench narrow and come perpendicular to the trench with the loader and backfill from the side.
At the company I work for we typically use two hoe's one digs and one backfills. Lets the track loader keep pipe and structures ready for the 345 and the box full. Course it does back fill the last lift or two and grade off. Our pipe excavators (in this case and in most cases a Cat 345) have long sticks with quick couples to switch out buckets, rippers, stingers, etc and keep the trench moving, while the backfill excavators use a felco tamper bucket (as seen on the 228 below), it's really a good attachment for this work.
here's a pic of us putting in water main at our ethanol plant project. we're using a bomag ride on roller. so far, i wish we had a 2nd excavator, vibe plate.
let's try the pic thing again
We did it the same way as Dayexco
we usually run 2 hoes, one with a hoepack bucket, and a loader on a pipe job. we'll use the hoepack to compact the trench while back filling and then bring a roller every 1000 ft or so
anyone here flood tamp? in concert with a plate tamper mounted on a 20 ton excavator it's hard to beat. I like flood tamping myself gives the boys something to do on a rainy day.
OK - I will be the first one to ask- what is flood tamping?:beatsme
I'll be the second to ask what flood tamping is?
We use a diesel plate here since useually on a water/sewer job one machine is the primary digger the second is a rock breaker and a loader with a side dump bucket as this area is nothing but rock or swamp. Only 1 guy here has a tamper mounted on a Hitachi EX 100 Typical crew round here is 2 operators,pipelayer,2 labourers.
Variations on a theme Hi, Folks. Lotta different ways to do it, huh? I have managed to steer clear of pipelaying for most of my working life, except for some 2 1/2 years on welded steel gas and oil mains back in the 1970's. However, I did work with one company doing almost nothing but pipelaying for a while and their preferred method was to use 2 excavators and a 4wd loader with up to 5 men. One excavator did almost nothing but dig or occasionally unload pipe as it came in. The loader with operator and 2 men ran bedding, usually sand, laid pipe, ran sand cover over pipe, usually 6" to 12" and moved on. The 2nd excavator was doing backfill in layers, placing and spreading with the bucket and compacting with a sheepsfoot roller attachment on the quickhitch after he dropped the bucket. In wider trenches, they would use a ride-on sheepsfoot roller for compaction. This 2nd excavator also did most of the pipe unloading from the delivery trucks and often was also used to level the right of way for the digging excavator or carry trench boxes for deeper trenches. One or the other of the excavators was used for laying the bigger stormwater pipes. They had the machines to run 3 full crews if needed, including a couple of tippers for moving materials longer distances around a site. All sand, screenings, etc. was delivered to the site by contractors. Trench depth varied a bit from about 3' to 19' - deep trench was done in steps - and anything over about 5' was boxed with expanding trench boxes to cope with differing trench widths. Pipe laid could be water, sewer, gas or stormwater and ranged from 4" minimum in the first 3 to 6' in the stormwater pipes with almost all of the smaller pipe being plastic. All stormwater pipe was reinforced concrete. No trench was under 2' wide inside the box if it was deeper than 5'. Down to 5' was usually dug 18"-20" wide for the smaller pipes. Their favoured excavators tended to be Hitachis or Komatsus from 20 to 30 tons. I've always favoured the Hitachis over the Komatsus 'cos they seemed to be better diggers and more reliable, although I did think that the early computerised Hitachis were dogs of things to do anything fiddly with. I have also run a couple of later Cat 330s recently and liked them too, maybe even more than the Hitachis. That said, I still think the smoothest and most powerful excavator for its size that I have ever run was a Kato 1220, Mark 2. It had no computers or any other 'whizz-bang' gadgetry, just pumps and valves and was one magic machine.
Correct me if I am wrong but I think flood tamping is when you literally flood the ditch with water. Then allow the water to settle the ditch. I don't know anyone that uses this method but I have heard of it.
Flood tamping Hi, Beachbum0286. Welcome to the forum and, yes, flood tamping is just about what you said although, in my experience, it is only used with sand and/or manufactured sand/very fine crushed rock.
Welcome to HEF Beachbum0286! :drinkup
That's why I have never heard of it. Around here too much clay - the last thing you would want to do is flood a ditch line with water, I don't think you would ever stabilize it.
Flooding. Hi, CM1995. I've been on jobs in clay where this technique has been used, even in live roadways - where traffic was still running. It doesn't take all that much water to get sand to compact in a trench situation. We used to run a 35 ton euclid dumper converted to a water cart with a monitor on top driving down the trench line at about 5 mph with the monitor spraying into the trench. Did the trick every time as we only had about 6" of sand to settle and that was sitting on top of concrete. Then we were putting crushed rock road base on top of that, compacted up to hotmix level. I've also done a fair bit of sand compaction where the sand was removed down to between 3 and 5 feet and then replaced in 12" layers, flooded with water and track rolled with a Cat track loader, 941, 943 or 953. Compaction on these jobs was always to a specification as they were all building sites, mostly houses but some commercial sites. I never had a failure. It's fairly easy with a little practice to 'read' the compaction by the depth to which the tracks sink into the wet sand. It does a fair bit more water to get compaction in this sort of situation. That is why they call it flood compaction. Hope this helps.
Good info Deas- I was thinking about using the virgin material (clay) as backfill. Did ya'll use sand or gravel as your backfill?
Backfill material. Hi, CM1995. On that gas pipeline job and on a later oil pipeline job, we were required to use sand bedding under plastic coated steel pipe. After the pipe was laid, sand was used to backfill up to the midline of the pipe. Then the pipe was covered with 6" of concrete, after which 6" of sand was placed over the concrete and watered as described earlier. If the pipe was in roadway, the rest of the trench was topped up with 2 layers of crushed rock road base/gravel. If it was away from any roadway, native fill was used and compacted. The materials were written into the job specifications and were not negotiable. On all the other pipelaying jobs I have worked on, the pipe was laid on sand bedding, covered with about 6" of sand with an identifying plastic tape laid on top of that. Then the trench was backfilled with native material to the top unless it was in roadway where it was filled to sub-grade level and compacted to specs. Unless otherwise specified, native material is usually used for backfill, unless it is totally unsuitable. The sand cover over the pipe beneath the native material is to help prevent accidental excavation and damage to the pipe. Road base/gravel is sometimes used for all backfill above the sand in roadways for better compaction and load bearing. Pretty much all backfill must be compacted, even in non-roadway areas, to prevent subsidence. There was a case about 22 years ago where a young girl riding a horse was killed when the horse stepped into a subsidence hole and threw her. The laws governing this sort of work were tightened up in that state (New South Wales) shortly afterwards and it spread to other states from there. Cost the company's insurance company a tidy buck too. Hope this helps.
Compacting ditches, banks & swails With this setup, you can literally compact on just about any angle, from any position, on any grade!