Use of Inclinometers to prove slope stability
Use of Inclinometers to prove slope stability
(OP)
I am in a situation where counsel from an opposing side wants to use inclinometers to prove/disprove a slope stability problem. Is the following statement defendable?
Using inclinometers over short periods of time(i.e. 3 months) does not indicate the true extent of movement.
A brief background, a contractor dumped fill on a virgin slope (over 100 years with heavy tree growth)took down the trees, buried them at the base of the slope and dumped fill on top of the organics. This happened three years prior to the request to use inclinometers to monitor the slope. I maintain that using it now for three months will not show the true extent of movement because the majority of movement would happen immediately after the fill was placed and then taper off over time. The decomposition of organics would cause this movement to extend over a longer period of time. Can anyone shoot any holes in this argument?
Using inclinometers over short periods of time(i.e. 3 months) does not indicate the true extent of movement.
A brief background, a contractor dumped fill on a virgin slope (over 100 years with heavy tree growth)took down the trees, buried them at the base of the slope and dumped fill on top of the organics. This happened three years prior to the request to use inclinometers to monitor the slope. I maintain that using it now for three months will not show the true extent of movement because the majority of movement would happen immediately after the fill was placed and then taper off over time. The decomposition of organics would cause this movement to extend over a longer period of time. Can anyone shoot any holes in this argument?





RE: Use of Inclinometers to prove slope stability
RE: Use of Inclinometers to prove slope stability
RE: Use of Inclinometers to prove slope stability
Right off, I can't think of any way to use the inclinometers in your favor unless something were to destabilize the slope slightly, like a long spell of wet weather, or an excavation at the toe of the slope to get the trees out or verify their presence. It's possible that the movement is generalized strain distributed over a large thickness, rather than a distinct sliding surface. If the former, it's even less likely that inclinometers would see much. You may get more benefit from reporting the timing and location of the settlement, any signs of a scarp or more general vertical offset at the top of slide, etc. Without knowing details of the geology or geometry, I can't say much more.
Were any of the old trees tilted or curved in such a way that they might show movements of the slope prior to the work on the slope? Too bad there's no way to post pictures here.
If the garage is on the fill, the poor compaction could explain it pretty easily.
Rephrasing some of what I said before, data from the inclinometers would mean nothing about previous movement of the slope UNLESS they show movement again, in which case they are on your side. If no movement is detected, the data are neutral. Inclinometers often show very small generalized tilting movements (as opposed to local shearing) when they are first installed, before they stabilize. If that happened, I suppose they could end up testifying falsely for your side if the tilt was downslope.
RE: Use of Inclinometers to prove slope stability
Your comment about the trees is great! I will forward that to my attorney. The house was built in 1911, the garage was built in the 1940's. There were cracks in the garage before this. But they have been there for decades(according to prior owner who lived there for 50 years). Now there are new cracks in the cinder block of the garage. (The entire garage is block) The garage was approximately 15' away from the edge of the slope, which then fell approx. 25' to the bottom. The bottom is another flat area before reaching a creek some 150' away. The new cracks appeared approx. 2-3 months after they did their work, and have become larger since. All of this info points to a favorable conclusion for me. I think opposing counsel, who has done numerous trials like this, is trying to pull something. Thank you for your comments, they definitely help.
RE: Use of Inclinometers to prove slope stability
RE: Use of Inclinometers to prove slope stability
My soil engineer expressed that this added weight alone could cause a slope failure, but is more than likely a supporting cause.
I'm in the middle of depositions for this problem. They are trying to build a case against me. My initial reaction to now placing inclinometers was that it was an inappropriate timeline. Placing them three years after and for only three months won't prove anything, but it may be considered as reduced damages because the movement has stopped. Unfortunately, I am not dealing with other engineers in this case. So I'm sure someone will think that just because it stopped(or reduced to negligible movement), that everything is ok.
I am looking for a hard fact as to why inclinometers are inappropriate at this juncture. Two sets of soil bore tests were performed, one by me and another by the defendants. Their results mirrored mine. What other tests would be 'fair'? And what other facts are there to search for?
Thank you for responding.
RE: Use of Inclinometers to prove slope stability
Inclinometers tell you where the slip plane is (if there is slippage). Frankly, I've never heard of anyone in their right mind who would propose using a set of inclinometer readings over a three month period to prove a slope is safe. I don't care what the past history of the slope is - it's ridiculous. There are so many unknowns: 1) Where to place the inclinometers to get readings of what is really happening in the subsurface? 2) What frequency of readings is appropriate (one reading at the beginning and one reading 3 months later, or?, 3) What is an insignificant reading for this type of case in the limited time frame?, 4) Will the weather effects during the 3 month test period mirror that of the next 50 years (which is a typical engineering design period)?
You could challenge opposing council to produce evidence of three other projects where inclinometers were used over a limited time period (three months) in a similar manner as your site to prove that a hillside slope was safe for a design life of 50 years. That will probably send them scampering.
The fact is the contractor, who destroyed the slope while most probably ignoring every applicable code, and then backfilled with who knows what while meeting none of the regulatory requirements, has to prove to you that the slope is safe. Perhaps, as a good-faith measure, he could take out a fifty-year hillside slope insurance policy to insure your property against any slope failure due to his crass stupidity...
Zoom
RE: Use of Inclinometers to prove slope stability
RE: Use of Inclinometers to prove slope stability
It occured to me today that the IMs would, with at least partial validity, support the case against you if the settlements and building distress continue and the IMs don't show movement. (I say "partial" here because they would have to be located right to measure deformation.) Then, you would have to be looking at other mechanisms for the damage. If no further distress occurs in the 3 months, then you're back to zero net value from the IMs.
Bon chance!
RE: Use of Inclinometers to prove slope stability
This begs the next question, is there anything that can be measured after the fact that would be of any use to this lawsuit?
RE: Use of Inclinometers to prove slope stability
New or old tilting of trees, associated with new movements caused by the recent work or older ones that could have been reactivated by the excavation.
Old photos you might have that can be compared against new photos to show ground movements.
That's about all I can think of.
RE: Use of Inclinometers to prove slope stability
RE: Use of Inclinometers to prove slope stability
I don't know if this work was done for you on your property or done for someone else on downhill property that is causing an affect on your siutation. This would be interesting to be filled in on this.
If the latter, then you should be pushing the opposing side to show that the slope is in fact stable by investigation, site characterization and stability analysis and what kind of factor of safety that you have - even in the best of time, you want to have a computed factor of safety of at least 1.3 (assuming no risk of life, etc.). And, better yet, that he did the necessary homework to confirm this prior to starting the work. If the former, it might be trickier.
RE: Use of Inclinometers to prove slope stability
A contractor signs a waste agreement with me to bring the spoils of a school project across the street to me(in exchange for some work around my home, no money exchanged). I live at the top of a 35' slope (approx. 2:1) My house was built in 1911, garage built in 1940's. Garage is cinder block and was about 12' from slope edge before work began. The slope was heavily wooded. Basically virgin ground for at least 50 years, no signs of dumping on the slope. In 2000 I bought the house, inspected the structure, found old cracks in the garage. The prior owner stated that they were there for decades. (Prior owner lived there for 50 years). The fill was to be placed on the vacant lot next to me. The school project had a mistake which required 2' more excavation over the entire footprint. The contractor began filling closer to my home. Our agreement stated that a wrap around drive was to be installed around the back of my house(between slope edge and garage) Without my approval, contractor bulldozed the slope, trees and all, and placed the brush and trees at the toe, then proceeded to fill on top of it. I caught them at the end of the workday and told them that the organics must be removed from the toe or my drive would fail. I was told they would. Next day, everything is finished. I invite the owner of the contracting co., to come out and inspect before I pour my concrete drive. I repeat the question of whether or not the organics were removed from the toe of the slope, he said they were. Approx. 6 months after concrete is poured, and after rains, the slope has visibly moved, with a 'belly' protruding from the lower third(just above the trees).
This is occuring in 2003, the house was completely painted in 2001. It went from white to gray. The old cracks were filled completely on the garage and then painted. Now, those cracks have opened up and there are new cracks all around the garage. They are very visible due to the white paint through the gray.
I told the contractor verbally before the project, during the project, and after, that the area under my drive needed to be compacted. I was assured it was.
SPT test right at the top of the slope resulted in between 2-6 blows per foot for about 10 feet. Split spoon from the deeper bore had large chunks of tree.
You would think that I have a strong case. All of my verbal warnings to the contractor can not be proven. Only the results from the soil bore tests in conjunction with the new cracks in the garage prove any movement. Some additional evidence includes a detailed topo. done before the work and then an asbuilt after. This only proves where fill went. Photos from before of the garage and slope from before and after. (I have these photos because I have been restoring this 1911 house for the last five years and have been documenting it)
Some more info, the toe of the slope is my property line, the slope is sliding onto my neigbors property now. My structural engineer and soil engineer determined that caisons are what would be necessary to remedy this at a tune of $800,000. (Gravity retaining wall would move too much and not support immediately the current structure) I do not want a lottery ticket here. I want the costs for pursuing this and someone to either determine or insure the slope from future failure. They sent a soil engineer out and he found the same results as mine did.
I am $20K out of pocket so far, and depositions are next week. This is why I am responding to this at 1am!
Thank you for taking the time to read this.
RE: Use of Inclinometers to prove slope stability
RE: Use of Inclinometers to prove slope stability
If you slope is still sliding into the neighbours property then movement is still occuring. Since it's surface movement, repeated topo surveys should prove slippage.
Cheaper and more effective than inclinometers would be a series of monitoring points on the slope that could be surveyed in on a monthly basis over a one - two year period.
As for remedying the slope chlharry is getting at it there - forget engineering, what you need is nature. Roots to hold the soil together and also to dry out the slope. They worked before and they'll work again.
RE: Use of Inclinometers to prove slope stability
You gave him verbal warnings and you say that your case is weaker because you've no records of them. That's not true.
The contractor has an obligation to carry out work that will not damage you home.
He has, so it's he's been negligent. Doesn't matter whether you told him or not.
RE: Use of Inclinometers to prove slope stability
I have read your history of March 3 and from what you have said I would think that you are to be blamed rather than the Contractor. Sorry to be so blunt. In fact, I would submit that the Contractor could be vindicated if the judge is on the ball and the Contractor has a good lawyer.
First you made an agreement for him to place fill between the garage and top edge of a 35 ft deep slope. In order for him to place fill at the location he needs to place material along the slope as he has to attain a sideslope. What he did would be what any earthmover would want to do. He denuded the slope and probably benched same to get the new fill to bond. His equipment operator could care less about slope instability. How much fill was to be placed to create this roadway. This would have dictated whether he had to place fill on the slope.
You have erred in my opinion by agreeing to this roadway especially that it is within a zone that I am sure is within the setback distance of the property. In fact, your garage is likely within the setback distance i.e distance from top of slope within which no structure should be placed.
You cannot assume that because the building was built in 1911 when such an aspect(setback)was not considered that the building would maintain its integrity throughout its life. This is not the case in geotechnical practice today. It does not matter whether the building was performing well over the last 50 years.
The fact is that your building is likely in a high risk zone and you should have been aware of this as sufficient information is available from your local building permitting office for constructing buildings adjacent to slopes.
The Contractor does not have to know about that unless he has been advised accordingly. It should have been your call to have the scheme of placing fill on the slope checked by a geotechnical engineer before agreeing to building a road in exchange.
As for your remedy of $800,000, I think this is on the high side and that both your structural and geotech are using the CYA approach as if anything goes wrong they will be sued as well. I do not blame them. Some freestanding drilled piles reinforced with h-beams between the top edge of slope and the garage with removal of the additional roadway fill could suffice. I am guessing here as I do not know the stratigraphy. I presume that you have a borehole extending below a depth of 35 feet.
Another solution is to create a toe berm at the toe of slope using fill placed for driveway/roadway. What constraints are existing on your neighbour's property to creating a berm at the toe of slope.
In summary, I think you have a weak case.
RE: Use of Inclinometers to prove slope stability
The fact is, I specifically told the contactor to stay away from this area for the very same reasons you stated and more. As a civil engineer with sitework experience and enough geotechnical knowledge to be dangerous, I know to stay away from something that could prove to be a major problem, and made them aware of this before, during, and after the project.
In your second paragraph, you give this contractor way too much credit, he denuded the slope from top to bottom in order to facilitate his dumping, not for anything as noble as doing his job properly! I am curious to know what contractors you deal with and what part of the country?! They certainly sound more ethical than those in my area. (Do you have a need for inspectors in your neck of the woods?!)
Futhermore, any competent operator wouldn't disturb a slope unless told to do so by the project foreman, otherwise receive the wrath of the boss.
I am curious to know what philosophy of embankment includes 'benching' with trees, stumps, brush, and other organics? The last I checked these were considered deleterious materials to be removed from structural supporting areas.
Now your third paragraph, the dirt driveway existed, for 50+ years, so did the garage. I didn't propose it there, it was there. What I proposed was a continuation of the drive on the adjacent parcel where the grade difference was only 4 feet. This was some 20-30 feet away from the slope and garage. I beg to differ on whether or not 50 years of history carries any weight. Are you suggesting that this is a coincidence? Is it possible? Sure, is it a competent assessment of the situation with the known facts described herein? Hardly. You are ignoring select evidence that suits your argument, that would be shot down with a handful of cross exam questions.
I am not dismissing your opinion completely, but as I am sure you are aware, we have to defend our professional opinions with sound engineering principals, not "the operator could care less". Well guess what, the operator is required to care more per our laws. It is called "workmanlike" manner. Even a contract that simply says, 'dump there' carries numerous implied responsibilities, inlcuding but not limited to "don't bury organics under sructural entities"!
Perhaps you could answer this question if proposed to the contractor; What projects have you buried organics under roadway or foundation areas and not compacted under the same? (Assuming you say none) Then the next question would be "Why did you bury them under the plaintiff's driveway? Now if you have examples of projects where you purposely buried trees and the like under areas you knew were going to bear structural entities, then you are welcoming a slew of additional lawsuits.
Not to burst your contractor friendly bubble, but this is a simple case of contractor greed. All contractors who do a substantial amount of earthwork projects know that their 'shortcuts' will not be noticed until a substantial time afterwards, usually when the project is over and proving that they are at fault is virtually impossible. This contractor treated me like an average Joe, unfortunately for him, I know what would cause these problems and I stopped them while they were doing these things. They promised to fix the problem the next day, and they didn't and lied about it. Contractor greed.
Finally, the constraint on the neighbors property is taking up extremely valuable real estate for a retaining structure. The toe of the slope was approximately my property line. Now the toe is 15 feet into the adjoining property. Don't you think that owner has a worthy argument agains't me?
Thank you Vad, you helped me realize that I have a stonger argument then I originally thought.
RE: Use of Inclinometers to prove slope stability
Nice counter arguments.
You are fortunate to have seen the trees being buried. Denuding vegetation and pushing same down slope is often standard practice on such projects. Very often snake pits are used at the toe to bury the trees so that they do not have to burn or remove to a disposal site.
You will be amazed to know that may of the highways we drive on and are performing well have a variety of so called deleterious matter below them. It is standard practice for Contractors to do things of the sort when no one is around. Do you really think that the operators get heck from the boss. It is also amazing to find out that some of what we think is poor practice works well very often.
I have seen enough trees, so called topsoil and the like under roadways that have performed well. There is a depth of burial where some of these so called deleterious materials are of no concern. Contractors have that experience better than engineers.
Contractors take chances on roadway work but are careful on grading that would receive a building structure because inspectors are present and a building site can be readily reviewed being apoint location. Not the same on highway projects.
I guess I do not know all the details of your site and discussions with the contractor. If the instructions were not in writing then you will have a difficult time defending same as it is your word against his.
I have seen too many cases where contractors make a convincing case that nothing was told to them etc. You do not have a binding contract with the contractor. He is not using any specifications except perhaps what you have told him to do.
Was there any supervisor on site. If you were there all the time then surely this would not have occurred. I am not sure that you can expect a contractor to be responsible for a problem unless you have a contract in writing that makes him responsible for defects. You have invoked a method specification which requires supervision. You do not put dracula to be in charge of the blood bank.
I am taking the position of the devil's advocate because you will be amazed at how articulate a contractor is and how easy it is for him to win the battle. Unfortunately sound engineering principles are not what the judge or arbitrator concerns himself with in such cases. As a layperson he will think like one and would have expected you as a professional to have taken more care especially when you did not put what you wanted in writing.
There are a number of issues that the contractor can bring up to show that you were responsible. The mere fact that the building had cracks would be one aspect that I, in the contractor's shoe, would indicate that you should have taken care about. Earthmoving is on a different scale and the judge will treat it in that context versus a builder that does a poor job on a building such as poor painting or something of the sort.
I hope that you succeed and would be curious to hear the outcome.
Regards
RE: Use of Inclinometers to prove slope stability
I recognize that you don't know all of the details and I intially was asking a specific question in the beginning of this post. But if you want more background I would like your opinions.
I was assured by the site foreman that the area around my home was going to be dealt with 'properly' (We had numerous discussions of compaction and what not to disturb) This assurance came numerous times before during and after. Up to the day I poured my driveway, I asked the contractor if he performed his work in that area as we had discussed. I was told yes. (Side note, the project foreman was fired 2/3 through the project for reasons I am unaware.)
I was not soliciting anyone to do this work at my home. If the project across the street did not happen, then I would never have had any of this work happen. It was unneccessary. It was supposed to be a win-win situation for everyone. They had a short haul, I got some luxury work that required large equipment to do(How many people have disposable income to dump in their properties?). No money exchanged. Now I don't think it is unreasonable to ask that the property and everything on it would be in at least the same condition or better after the work is performed. Accidents happen to everyone. But this was no accident. I had specific requests and direction, they were ignored. As a result, I have problems. They ignored standard earthworking practices and principles, (organics decompose and allow for continual settling over a period of time, therefore they are not ideal in any base material which will ultimately carry a load.)
Let me change my approach here for a moment. If I hire an electrician to rewire my house and he does things behind the walls that are not up to code, is he responsible for damages that occur if his wiring fails? I can't see what he did, and I wouldn't know if he did anyting wrong unless I open my walls, witnessed it or someting goes wrong. Regardless, he has a responsibility to do his job in a 'workmanlike' manner. This premise was created because no contract can cover every scenario.
Now I know that I am talking about a fantasy world where everyone does things properly, but this isn't a contractor that has never done earthwork before. If he told me he didn't then I would have assumed the responsibility because I am aware of his lack of experience.
The biggest difference between this 'slope/fill failure' litigation and others is that I am an engineer who knows better. This contractor would never have been called on his actions if an average homeowner was in my shoes.
Thanks for your comments and opinions.
RE: Use of Inclinometers to prove slope stability
RE: Use of Inclinometers to prove slope stability
2. Materials exposed in the cuts.
3. Compaction (method, density testing) of the new materials, specified vs used.
("And which ASTM standard is used for the laboratory maximum density of fill containing large trees?" "That would be D 698 modified to use a 20 cubic yard mold and a 20-ton rammer. We've never actually done it because none of our technicians can lift the hammer.")
RE: Use of Inclinometers to prove slope stability
You may disagree with some of the opinions but if you have inspected "dirt" intricately and with much detail you will appreciate that thin lenses of sand and silt within the soil matrix coupled with a particular topographical disposition of your hilllside is all that is required to be blocked thereby disrupting the pattern that the soil was "born with".
Natural slopes are fasinating and we often see them standing at steep angles. However, change their regimen and we have problems. To deal with mother earth we must first understand her as she does not always follow our rules. Unfortunately we do not spend enough time to understand geologic composition of soils/slopes.
Your case of the electrician can be answered through the regulations for having any renovations etc done to a home. Yes, we do not always follow those and we are taking a chance that the electrician is good or we know him personally and he will do a good job. If something goes wrong with the process, both the electrician and yourself would be held responsible. In fact the electrician would be expected to have advised you about a permit for the work that he is doing so that the building reps can inspect the installation to determine if codes etc were followed. I am sure that if something dramatic happenned, you would say that he did not advise you accordingly and he would say he did and you allowed him to go ahead because it was a small thing and no bother. Sometimes you win and others you lose big time. Every home owner must understand the rules of the game and pleading no knowledge is not an excuse these days.
Regarding the site foreman who was fired and is making statements about poor work etc. You have to understand that someone fired always more than often likes to get back at the one who fired him. He may be telling the truth about your situation. However, you have to be clear on the reason why he was fired before deciding that you will use him on your side. This is where your lawyer knows the game better than most Engineers. If not you can be in a worse position by using him. Do not forget that the other side may be expecting that and will be prepared for the rebuttals.
I am unable to say more and again wish you the best.
Regards
RE: Use of Inclinometers to prove slope stability
I say this with the utmost sincerity, your last post is worth at least a couple quarter's worth of geotechnical engineering (amongst other disciplines)coursework. Exploring and analyzing the intricate nature you have described can only be appreciated by few. I do not pretend to grasp the full science of geology and geotechnical engineering and that is why I turned to all of you. I simply received a "pamphlet" worth in my time. I very much appreciate everyone's input and comments. This has been a very good learning experience for me. I hope I will not be paying for it through the litigation.
I only want my costs and the ability to sell my property without losses. I don't think that lumps me into the category of 'McDonalds spilled coffee in the lap' litigation.
I firmly believe that if the contractor simply made an error, I would accept my involvement and this would not have progressed to the point it has. But it has become evident to me that the contractor used me as a vehicle to increase his profits without care of damages to me.
I can not let that go just on the principle.
Thanks again all of you, perhaps I will post again after this is over and let you know what transpires.
Respecfully,
Dlustri
RE: Use of Inclinometers to prove slope stability
Just out of general nosiness, what was the final outcome?
Thanks,
DRG
RE: Use of Inclinometers to prove slope stability
This series of statements and opinions ought to be part of an engineering course on soil mechanics and the practice of Geotechnical engineering. Very useful discussion. Many lessons to learn here from this forum and they apply generally to other engineering subjects.
Both had valid arguments, but lawyers have the final say.
Thanks.
RE: Use of Inclinometers to prove slope stability
The case has settled, but I have not been told what I am allowed to say just yet. As far as the technical aspects, I guess I can talk about those without issue.
The inclinometer was installed but only an initial reading was taken(on the record). I believe that additional readings were taken, but not disclosed. They were required to share any and all findings, but if on the record they didn't take any readings, then they don't have to disclose anything. If they found evidence in their favor, then they would have disclosed it. This is just my paranoid belief. I have no proof of it just strong suspicion beause of disturbance of the testing area a month after initial readings.
I became the target of the defense counsel and their professionals. Their argument was that, as an engineer I should have known better. I never got the chance to defend my position, that I did know better, I told them to stop, they didn't because the contract didn't require them to do so, and as a result there were problems.
My biggest disappointment was that their geotechnical engineer became a "prostitute" to their cause. I had a tremendous amount of respect for the individual before reading his report and finding that it basically mirrored the defense counsels motion for summary judgement. I guess there will always be someone out there who can be had for a price. I didn't expect a professional engineer to sway into such posturing.
The technical aspects of the case were mostly in my favor. Testing proved failure in the fill, not one of the four professionals disagreed to that. (two were mine, two were theirs, structural and geotechnical) The professionals were never cross examined so I believe that more arguments for my cause would have surfaced. The bottom line for technical findings is that there are only so many different ways to read a bore log. The SPT and wildcat tests were indicative of failure in the fill layer.
Their argument would have been heavy in the contract, and my argument would have been heavy in the "workmanlike" manner of construction. There is an inherent responsibility to anyone in their respective business to do things properly. If they are told to do things in a manner that would cause problems, then it is their responsibility to tell the client their position.
Once again, these arguments never had a chance to be argued. The court basically forced us to settle, doing their typical "you have a weak case" argument to both sides individually. The argument that "forced" me to settle was the amount of cost to depose all of the professionals in preparation for trial.
My final feelings on how it would have gone was that I had a better than half of a chance to win, but that doesn't mean that I would get the damages I was looking for. I found myself in a real life "Deal or No Deal" gameshow. I had a bird in the hand, should I gamble for more without any guarantees?
The whole ordeal left me with a bad taste in my mouth and a huge problem in the back of my home. The settlement was better for them than for me. I was told that a good conclusion to a lawsuit is when both parties feel poorly about the results. I guess that was the case.
If anyone has any more technical questions, I would be happy to share more details as soon as I find out what I'm allowed to share. I think I have been vague enough so far and I have not named anyone. I am not intentionally slandering anyone, if I have done so, my apologies.
RE: Use of Inclinometers to prove slope stability