PSN-L Email List Message

Subject: Re: floor slab pier
From: Karl Cunningham karlc@.......
Date: Wed, 02 Aug 2000 13:20:56 -0700

Sean-Thomas --

Did the tar work well for isolating noise?  I'd think it might not be very
good above some freqeuncy.  I've thought about digging out a section of
garage floor and pouring a pier down to bedrock (<10 ft down).  But then
how to prevent things from falling into the gap, yet not couple noise from
the surrounding slab?  How about thin rubber sheeting across the gap?
Other materials?


At 12:46 PM 8/2/2000 -0500, you wrote:
>Regarding sawing up the slab floor: our experience:
>But serious horizontal tilt noise was still a problem for the STS-1
>seismometers operating at 360 seconds. So we got $5k from IRIS and
>had the slab pier removed, and dug a pit 6 ft deep to a more consolidated
>clay layer (bedrock is 30 ft down), and filled the pit with concrete
>back up to the floor level. THe gap between the pier and the floor
>was filled with tar (a bad idea!: we had to cover it with ethofoam
>to keep it off of everything). The new pier reduced the horizontal
>noise by greater than a factor of 10.


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Larry Cochrane <cochrane@..............>