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I need to design temporary shoring for a 30' diameter, 36' deep circular shaft. I'm thinking of using rolled steel beams with wood lagging. Any comments or other ideas?

Geopave (and anyone else), thanks for your interest and help. The specific project is for an engineering justification for a shoring system that had been installed, functioned acceptably, and was cited by OSHA as not meeting the OSHA requirements found in 29CFR1926 Subpart P Appendix C. The...

I am trying to determine the load that the brace must support. I am sure that the brace will not have to support the entire load between supports due to the arching effect of soil between braces, but I am not sure how to account for the arching effect.

How do you account for the arching effect of relatively stable (OSHA - Type B) soils between vertical braces in a shallow (less than 8' deep) braced cut with vertical braces spaced from 4' to 8' apart?

Do I need reinforcing in the top of a continuous grade beam where the moment is negative at the piles for a grade beam with a linear loading rate of 3000 lbs/lf?

I have to design a residential foundation (slab on grade) on a site where peat is located from 5' to 15' below grade. 1. Do the gradebeams have to be below the frost line? 2. Can the slab itself bear on granular material compacted on the existing inorganic material with the peat below? Thanks.

The manhole in question is a water valve manhole with the penetrations sealed with a rubber boot. The manhole was tested with three different monitors and the only gasses that were abnormal were O2 and CO2. Any other ideas?

The manhole in question was a sealed watervalve manhole, ie no effluent. The manhole was tested with three different monitors and the only gasses that were abnormal were O2 and CO2. Thanks for your input. Any other ideas?

Is Oxygen used in the concrete curing process? I am trying to determine the cause of low oxygen concentration in a new concrete manhole. Oxygen concentration was 2% and C02 concentration was 8% in a manhole that was three weeks old.

Is oxygen used in the curing of concrete? I'm looking for a cause of low oxygen levels in a new manhole. Oxygen was measured at 2% and CO2 8% in a manhole that was 3 weeks old.

Does anyone know of a manufacturer of a skid steer or track loader mounted Geotechnical Drill Rig?

The last post by dicksewerrat fits with the facts of the case if it is in fact possible for CO2 and O2 to be transferred through the concrete manhole. The initial installation was in an area of organic soils and did require dewatering during construction. It is also very possible that...

Thanks to all who have participated in this forum. Sadly, I am no closer than before to a satisfactory explanation for the depletion of the oxygen in the manhole. I will post any further factual developments as they become available. Regards, Hairman

A sample of the 2" of standing water at the bottom of the manhole will be tested on 8/28/03 for organics and CO2. I will post results as soon as possible. Question: Is it possible for gasses to pass through the walls of a precast concrete manhole? Thank-you all for your input...

I have further factual information regarding the atmosphere in the water valve manhole. On August 21, 2003, several safety experts returned to the scene of the accident with gas monitors including a CO2 monitor that had been factory calibrated. Readings were as follows: 2' below the cover...

Regarding the Dissolved Oxygen in the standing water: Today I took samples of the water at the bottom of the manhole. What should I test for with respect to disolved oxygen, and what other characteristics should I test for to find clues to the mechanisms for depletion of the oxygen...

Thursday August 14 at 12:00 a laborer entered a 17'6" deep by 6'diameter water valve manhole to operate the valve. He entered without checking the atmosphere and died despite heroic efforts of his coworkers. Background: The manhole had been installed three weeks ago as part of a new...

Everyone seems to be pointing to an active shoring system, however, it seems as if a sloped system may be appropriate. The excavation is a building excavation approximately 200 feet across. The slope is a homogeneous simple slope in clay with an unconfined compressive strength of 4 TSF...

I need to determine a safe slope for a very stiff clay (Unconfined Compressive Strength - 4 tons per square foot) for a 14 foot cut. The exposure will be short term. I know that OSHA allows a 3/4:1 slope (53 degrees) for an "A" soil, but I need to slope at a steeper angle due to...