Basement Wall - Adjacent Construction - Urban Area - Concrete Wall Deflection Measurements

[clemsonCMT]

Hello all. I have a question about obtaining vertical and horizontal movement on an existing basement wall (2 stories underground). A new building will be constructed about 15' away from this existing building. The new building will have 3 stories underground and the excavation will be below the basement walls (2 stories underground) and the footings for the existing building. Another consultant has determined the excavation from the existing building should start about 6 feet from the top of the existing basement footing and extend at a 1:1 slope down to the proposed footing bottom of the new building.

My question is: what would be the best (most accurate) way to measure the movement of the existing basement wall during construction to help make sure it is not damaged or is not moving because of the adjacent construction. Something wireless with an alarm would be great, but I am just not sure what is out there. I am aware of LVDTs, dial gauges, a good yard stick, straight edge, inclinometers, etc. We will also have a surveyor shoot a couple points around the building periodically. I want to be able to measure the vertical and horizontal movements in the wall with real-time data.

Any advice would be appreciated. Thanks everyone!



Jason Vaughn
smeinc.com

 

[PEinc]

Fred Tarquinio, Business Development Manager for Nicholson Construction, recently gave a talk where he described a total station system that was programmed to read various monitoring points and then notify people when a movement threshold was exceeded. You could try calling Fred in Nicholson's Cuddy, PA office.

http://www.PeirceEngineering.com

 

[GeoPaveTraffic]

There are also inplace inclinometer systems that could be mounted to the inside of the basement wall. Lots of other options depending on geometery and restrictions.

If you are lucky, you have one of the larger geotechnical companies nearby with lots of instrumentation experience. Give them a call.

Or if you want to keep the work inhouse, give Slope Inclinometer a call. They can help out as well.

Mike Lambert

 

[Ron]

Inclinometers, strain gages and lvdts....properly placed. Surveying equipment, in my opinion, is not accurate enough to detect very small movements. You will be trying to detect very small movements as the next movement could be very large!

Instrumentation can be expensive, but a hell of a lot cheaper than litigation.

 

[oldestguy]

For what it is worth, you can develop your own system using dial gages. I have found that they work quite well measuring between fixed points, such as a nut glued to the movable object, as one point and another nut glued to a fixed object. Between them I used a steel pipe and rods inside each end with fixed stops for adjustment to one rod coming out one end. On the other end another rod on the movable end is, fitted with a dial gage. The points on each end to fit in the nut openings were tapered with a 90 degree angle of the point. Distances between movable and fixed points generally were about 10 feet. On one job I measured the deflection of metal arch large culverts as a railroad train passed above. I didn't get into possible temperature length changes of the pipe, due to the short term of each measurement program. Repeating the readings at any time was easy. For the details of such a rig any machinist can work out how to do it and not throw in errors. On yours, I'd suppose the measurements would be in the neighboring building basement.