well don't get in the things for God's sake...if it's more than a few feet deep (not slope back) stay out of it. make observations or do testing from the top. if you must get in there, step the sides back, tie off, have ladders available, evaluate the excavation, etc etc...don't be stupid just to save a dime, time and/or effort (i've seen my fair share of people almost killed in trenches---me included).
The point I was trying to make out - the consequence has taken the bar to a level associated with a test pit that, well, it would be very expensive (shoring) or, in other cases too large a footprint at the surface to make digging one viable as an investigative tool - get it and out quickly and safely but . . . Obviously the attached picture that I found in a mining magazine might not be so well thought of now from a risk point of view (company and partner/senior staff).
Yes and no. Having to have equipment to lower in the box, etc. shoves the price of the work up and up ($100/hr??). That is why I was saying that economically, we may be losing the battle. I've done 10 to 15 pits per day in the past (we had clayey soils that were going to stand) - how many can we do if we have to "steel box" it or shore it? It's not like China where we can hire 25 workers per pit and still be less than $100/day.
We do test pits quite often in clayey soils and urban fills in the mid west US. Our policiy is to cut vertical side slopes and make the ends as vertical as possible, however, NO one enters the test pit after it is over 2 to 3 feet deep. There are no exceptions to this, period.
Any testing and sampling that is to be done is done on intact pieces of material removed from the test pit. The geologist or engineer can watch the excavation from the surface, know where the piece came from, take a sample and make the log without entering the pit. Yes it takes a little longer, but not much.
We can easily excavate and backfill 10 test pits to 10 feet in a day.
GPT - agree that is a way to do it and the safest. My problem was that unless you had a good backhoe operator, the "intact" piece was always getting mixed up with slough, and stuff. Still, the criminality makes me wonder!!!! (We had loess in China stand up 6 to 8 m vertically with no distress for weeks (until we finished the excavation).
Being in the UK and the same field as the Guy who died, this all hit us hard as many of our own Engineers are same age and experience. However going back to some of the comments above, if there is a risk then don't get in the pit!.
As soon as this occured, the AGS website published a statement and included a photo from Costwold Geotechs own website with the owner Peter Eaton in the pit with only his sholders and head showing above the ground and with a ladder included to show access to the pit. Very inciminating and I am sure this will feature in the case.
For many years now the practice of getting into pits to log samples has been avoided at all cost becase of the risk of collapse, especially in the UK with our history of glacial relic slip surfaces. As soon as this happened, and with the inciminating evidence of the photos from Costwolds own website, it was conjectured that they would be hit hard.
We have had to develope practices which either eliminate the need to enter excavations, or where we do full and approrpaite protection must be taken. I would say all Geotech Companies in the UK follow this procedure, however given this sad case it does show there are still some exceptions out there. All very very sad.
I don't know the UK. In US, the rule is there, case likes this shouldn't lead to prohibition, or causing more than it is now for firms that follow the rule.
What is the size of typical test pit?
I am thinking can a steel barrel, or box, be dropped into it to provide protection, similar to that used in underground pipe line construction.
We are covered by the Health & Safety at Work Act, responsibility of employer not to put employee at risk, no such things as accidents, if there is any way it could have been avoided then it should have been, cost is way down the list of considerations and words like reasonably precautions spring up all the time.
As mentioned previously, now very uncommon to get into pits because of the known risk of collapse so when the Guy dies in a trial pit and web shows owner/employer in trial pit doing same thing it all becomes very damning. This is the first case of it leading to a prosecution case, and I am sure this is because of the liklihood of a conviction [dare I say it, as an example case?]. We do know some of the ex-emloyees of this Company, and it would appear that their Engineers were often required to enter pits to log samples, which is at odds with how most other Companies have done this for many years. As mentioned above, there are ways of avoiding the need to enter test pits, so it should have been avoided. The area where the incident [note not accident] happened is widely know for slope stability problems, well documented and noted on the geological maps, the trial pitting was also being undertaken in heavy rainfall which added to the instability, took the resuce people over a day to get him out apparently. Given the known ground conditions and likley prevailing weather [in the UK it always seems to rain], he should not have been required to enter the pit, however with the damning evidence which is now commonly know about, the Employer is found to be at sufficient fault to bring the case against him.
Hi Guys: This old guy almost learned the hard way 14 feet down in apparently stiff clay. Trouble is that clay had shrinkage cracks making it just a series of clay blocks sitting on each other. Since then nothing over 4 ft.
As BigH points out, we know there is a risk and that should be sufficient proof in court. Sort of like mountain climbing or maybe sky jumping.
Working from the top can be done accurately, especially if well experienced.
kslee1000 - as you know, by being able to go down into the pit, one can gain, in my view, a better handle on the microstructure that may be there - say orientation of layerings if present, and the like. So, while in homogenous soils, it can be done from the top - there are reasons that one may need to enter the pit - only need to do it safely (and hence, additional costs). Also, if one is doing a test pit for borrow purposes, as given in the USBR Earth Manual and other locations, they like one to collect a "column" of material for purposes of knowing the "average". I've entered many pits - never as deep as what oldestguy did - but one must be fully aware . . . One thing you get, too, in construction - you can forego the requirements of shoring, etc. if a geotechnical engineer deems the open cut safe (or cut at whatever angle). I think that we, as geotechnical engineers, might be quite hesitant to say it is "okay" - yet construction managers push. Interestingly a safety guy I know says - you have to shore/slope, etc. but all the geotechs have said it is okay so it is done . . . Gets to pass the buck.
As a geologist, I enter test pits and large-diameter borings all the time. BigH is correct, though I don't know about the term microstructure... The test pit and large-diameter boring (24" or greater) is critical as an investigative tool in many of the areas where I work, where large translational landslides can/have moved as a cohesive block (i.e. the old slide doesn't look like slide debris). I'm looking for slide plane(s) and gouge-zones, often times these can be quite thin (think 1/2 an inch thick or less). Faults, critical joint sets, bedding attitues, good luck getting an orientation or a critical soil/rock sample simply from a boring.
Safety is paramount to me. There are both borings and test pits that I've refused to enter. Key to this is to be on-site while said test pit or boring is being excavated to be able to get a visual of the materials coming out.
"kslee1000 - as you know, by being able to go down into the pit, one can gain, in my view, a better handle on the microstructure that may be there - say orientation of layerings if present, and the like."
Your reasoning exactly matches that I was taught in school. Thanks. Wish this tragic event won't lead to outright ban, but better, stricker rules on safety planning before jeopardize someone's life.
There are already strict enough rules in the uk for safety (in my opinion much stricter than the US) it is simply that they did not appear to follow them.
Why people ignore the rules?
Because lack of enforcement, and sometimes the punishment for such violation is a pat on the back (cost-wise).
In my work area, the rule is simple, one strike put you (the contractor) in the penalty box (stop work) until the end of the penalty period that fits the severity of offense. The second, you are out (terminated for certain amount of time). Third, will never see you again (terminated forever).
The result, the management is less likely to push before consult with safety, the contractor has learned to say "no", incident does occur, but has been drastically reduced in number, frequency, and sevirity.
Until we all can safely say no without worring been picked on for reprieve, the rule isn't strick enough.
