Causing failure prior to actual construction of Embankment
Causing failure prior to actual construction of Embankment
(OP)
An embankment of 3.0m height is to be built on a thick (10m from ground level) marine clay layer whose N=0.It is failing in stability (deep-seated), bearing capacity and naturally the settlement is also abnormally high - so a combination of ground improvements are required.
I am thinking to construct the embankment upto 6.0m i.e preloading with 3.0m surcharge over 3.0m height and wait for 3-4 months and let the embankment fails in shear. After that the entire embankment will be removed and new construction of 3.0m high embankment will be taken up.
Is this a technically correct approach?
I am thinking to construct the embankment upto 6.0m i.e preloading with 3.0m surcharge over 3.0m height and wait for 3-4 months and let the embankment fails in shear. After that the entire embankment will be removed and new construction of 3.0m high embankment will be taken up.
Is this a technically correct approach?





RE: Causing failure prior to actual construction of Embankment
The approach you indicate is the displacement technique which can be and has been used. Some of your surcharge can become part of your embankment. If the material was peat or muskeg I would tend to go along with the approach as the displaced material could be re utilized. With soft clay this could pose a problem but I am not sure in your case if it would.
Depending on the extent of construction and cost considerations one could examine other options such as leaving clay in place and modifying ground using deep soil mixing etc.
It seems to me that you have examined the alternatives.
On one project I witnessed muskeg being displaced as fill was dozed in (quite a nice peel). The original intent was not to displace the muskeg but it occurred as the bottom of the peat was fairly competent and fill advanced with a D9. In hindsight it could have been the contractor's intent.
Fill was brought in as the dozer moved ahead. Some failures occured in the new embankment and the concern was whether peat was trapped in isolated areas. This was the case as was suspected. I think you anticipate this hence your decision to completely remove surcharge and displaced material.
I would appreciate learning a bit more of the project if you do not mind to see if there are other alternatives. However, if failure has already occurred as you have noted then your approach seems plausible.
RE: Causing failure prior to actual construction of Embankment
RE: Causing failure prior to actual construction of Embankment
Just curious.
What year were you involved in Guyana. I remember John Huntley (I hope I have his last name correct, it has been a long time) from Guyana graduating at Queens U, Canada with a mining degree in 1975/76 undertaking an undergrad thesis on displacement methods related to work at the bauxite mine. I was doing graduate work at the time and had some discussions on his topic. I probably still have a copy of his work. Have to do a search. He had the blasting method as well as a technique. At that time a lot of work was being done in Guyana by Geocon monitoring tailings dams etc.
I spent the summer of 69 in the GED locating pipelines in the bauxite and alumina plants.
RE: Causing failure prior to actual construction of Embankment
RE: Causing failure prior to actual construction of Embankment
Thanks for info. Small world indeed. Should have an XM on that. I am sure that you partied a lot in Wismar and Mac City.
RE: Causing failure prior to actual construction of Embankment
Actually I have already done the calculations with band drain and staged construction. But I am not sure about the efficacy of stone column in such very soft marine clay formation.
Frankly speaking, this is the first time probably I will be doing this displacement technique. So, I really need the references for analysis and how actually it works.
Thanks once again
RE: Causing failure prior to actual construction of Embankment
Treatment of Soft Foundations for Highway Embankments NCHRP Synthesis of Highway Practice No 29.
Treatment of Problem Foundations for Highway Embankments NCHRP Synthesis No 147.
No 147 is an update to No 29.
I read the Rainy Lake Causeway that Big H is talking about but cannnot put my hand on the paper. He may be able to provide the Journal reference otherwise run a search or check the Canadian Geotechnical Society journals around 1960's.
Just as a thought, have you looked at using hogfuel, sawdust encapsulation as lightweight fill. This technique works well also as the materials have a low density. You can possibly use 2m of sawdust or blend of hogfuel and sawdust and a metre of clay on top. As well geofoam etc are techniques re use of lightweight fill. However, there is a cost as well and performance depends on loading conditions, intent of structure etc but they have been used successfully Dr. Horvath of Manhattan College has done work in this area and you will probably obtain references using civldept@manhattan.edu.
Best of luck. Let us know how you finally proceed, and results.
RE: Causing failure prior to actual construction of Embankment
I will look up Fred's paper - it is at the office; don't have it here. Will post, enshala, later this week; decided it is time, after a year, to take the family to Calcutta and stay in a luxury hotel - one with full time aircon!!
As I indicated, too, earlier, check out Tschebetarioff's book - he has a nice section near the end on this; also I saw something in a more recent book but don't have handle on the book - just the chapter (given to me). Michigan also used this technique and it was almost known as the Michigan Method!! (1946)
Best to all.
Howard
RE: Causing failure prior to actual construction of Embankment
But BigH, you are really coming to Calcutta - basically I from Calcutta (Kolkata) but based at New Delhi.
RE: Causing failure prior to actual construction of Embankment
RE: Causing failure prior to actual construction of Embankment
RE: Causing failure prior to actual construction of Embankment
it's good to note that u have been involved in a project in Guyana. I'm from Guyana (Georgetown) and would like some details of what was actually done on the project.
@ VAd: where can i locate the paper: "Treatment of Soft Foundations for Highway Embankments NCHRP Synthesis of Highway Practice No 29.", from
RE: Causing failure prior to actual construction of Embankment
Correct me if I'm wrong 1967pradyot, but it sounded like you were telling us the 3m embankment by itself might have been nearly stable, but when you analysed it with a surcharge (to take care of the settlement) you got an FoS<<1. If this is the case then you should do whatever it takes to AVOID causing a deep seated failure. Once you fail the foundation you'll be dealing with a remolded zone of even lower strength beneath your embankment. Depending on the properties of the clay, it could take months or even years for the pore pressures to dissapate. There are many methods you could use here, which VAD and BigH touched on -- i.e. stabilizing berms, lightweight fills, ground improvements (deep mixing or stone columns). Depending on the timeline for you project, maybe one of the cheapest is to use staged construction with peizometers to monitor the strength gain. Use wick drains if you need speed things up.
So am I too late?
RE: Causing failure prior to actual construction of Embankment