Here is the deal, this particular area of this abandoned strip pit has stood solid since the late 40's about 10yrs ago the spoil pile slid, so the fix for it was 1200 ton of shot rock, it held up ok for a year but then this year we went to put another 1000 ton on it and it only held about 850ton.....Yesterday I left to let the trucks stack a few loads and I was going to be back in the morning to place the rock. but when I got there I seen this, (pictures) My opinion is this, The soil under the waterline has became saturated and has sheared off, and with every ton of rock we place it's just making it worse. the fix,......(this is the part I am curious about) 1. Drive sheet pilings at or near the waterline and backfill up against them 2. Drive pier's in the active slide area 3. ShotCrete 4. Several Layers of concrete and riprap from roadway to several feet into the water. This is an engineered deal so my opinions arent really welcomed but I will do anything they decide. Any Q's? or Ideas? Pj
Looks like classic case of shear failure to me. Adding more rock will make it worse. #1 & 2 will be expensive. I would recommend removing material. Cut the road down to the top of the slide, once the slide stops moving. We had a bank fail similar to this on a paved non-motorized trail. The bank had been cut about 8 years ago when the freeway was built and we put the trail on top of the bank. We paved the trail in the fall and over the winter the bank slid. We left the bank alone, cut the grade down to match the slide and repaved a couple hundred feet of the trail. Still holding up good 2 years later
cut steps to hold rock and add filter cloth to stabilise the slope, been there before, let us know what happens
We have a few slides like that in my area powerjoke.They happen mostly where the road is close to a riverbank.Flooding & water current weaken the edge of the riverbank & half of the road ends up in the river.County highway department will move the road away from the slide when possible & let mother nature take its course.Allot more cost effective to move the roadbed over 20 feet then try to fight a never ending battle with the river.Dont know If thats an option on your job.
1. I too think that removing some of the weight would be a good thing, 2. I'm affraid that the slide is actually taking place at or near or below the waters edge, so im not for sure if we can bench the highwall.....Int the second picture you can actually see that little tree leaning towards the road....it was straight yesterday, (oh and also another 5' higher too) 3. Road movement to me also seemed like the most logical solution but for some reason was not an option?....still dont know why tho lol.. Pj
the sheeting will cause a lot of vibration. and you may end up with a rock dam... my guess is they want this fixed before it chokes the river down and creating more flooding in the area.. I suppose when the junk trailer is part of the river they will move the road.. One thing is for sure... It will over-engineered and underfunded...
Yup, I noticed the tree at water line leaning inward, seen plenty of signs like that in my horizontal drilling days, sure sign there's movement way down low at the waterline. Going to be hard to keep anything on the top when the bottom is falling out from under it. :yup
What's your suggestion? Pj
Oh man, the answer to that question is far above my level of expertise. All I can say is stuff like that is directly related to the geology of the particular site, the way rock and/or soil is laying or interacting with each other. Would more than likely require vertical sample drilling to get a proper feel of the geology of the site to determine the needed course of action to stabilize. Simply speaking, to use an example, slides like that are similar in reaction as a clay dirt fill that's not fully compacted. If you drive a truck across the fill, the tires mash down clay, and it pushes the clay up alongside the tires. So the parallel is when you put the weight of the stone on top of the hill, it simply pushes the material at the water line, material moved, and you got the scarp at the top of the hill. So until someone figures out how to stablise the material at the bottom of the slope, you'll not have good success holding material at the top of the slope.
It's a slope stability problem. It's been over 40 years since I've sat in a soils class but this Wikipedia article will get you in the correct direction for the technical information. http://en.wikipedia.org/wiki/Slope_stability Any attempt to restore the slope to it's original location and hold it in place will be expensive. Heavylift is correct, driving sheeting or piling will most likely send the existing bank further downhill . Move the road further away from the water and cut the grade down to the top of the slid bank (or as close as you can get it) after it stops moving. Sounds like it's still moving according to what you posted
Bring in a couple barges for the rip rap and spoil. Cut in a key way. Put the rip rap back. Do we win anything if we get the right answer?
What we have done before is excavate the slide area to stable ground around it and down below the water hopefully to something stable. Fill the excavation up to above the water level with ~3" minus crush making a bench to build your slope on. Place your spoils back to build the slope. Lose all that shot rock in your rock bench. I agree with ATCOEQUIP though.
I agree with Dozerboy.