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The rock and ice mechanics lab at Lamont-Doherty is led by PIs Heather Savage, Christine McCarthy and Ben Holtzman. We are in the process of growing our lab and building our experimental program. Along with a team of postdocs, undergrads, grads, and longtime staff engineer Ted, we are rehabilitating and revamping some of the old equipment and building new rigs for exciting new experiments on both rock and ice. You can follow along with our progress here.

Monday, 19 December 2011

(mini-) Earthquake!

Ladies and gentlemen, the Biax is now fully operational! We can now make earthquakes in our lab!
The main cause for the delay was this pesky guy below. The chassis is the component that handles the flow of all that data coming from the rig (10 strain gauges, 2 load cells, an LVDT measuring displacement, and anywhere from 1 to 4 transducers measuring the seismic signal) and going to the computer (for immediate feedback) and to the RAID (for short-term storage). Although the data all come in as basic voltage signals, the rate of data streaming for the different components varies, making it difficult, for some reason, to get the optimal combination of cards and cords for the chassis. While I was away, Heather worked with the manufacturer to get us the right combination. The card on the far left gets the signal from the BNC, the card protruding gets the high speed signal from the transducers, and the wide middle card is a built-in RAID. 
It took a little while to get here, but we now are able to load up the sample and, by monitoring the voltage on the LVDT, watch it creep along until we hear the "Crack" and "Pop" of little earthquakes. Success! Now we get to start systematically varying things to be able to predict the onset of the earthquakes and, in particular, try to understand the transitional period that is believed to occur between the creeping and the earthquake. 

Friday, 2 December 2011

soldering up a storm

Now, in order for the confining pressure and pore fluid pressure intensifiers to respond and "stop on a dime", if you will, the hydraulics have to have something to push against. So we needed to rig up pipes that will carry compressed air from the air compressor in the room next door. In addition, there needs to be a reservoir of air on the ready in case a large volume is needed. Thus the big yellow buoy-looking thing on the left. So, armed with about 50 feet of 3/4" copper tubing, tube cutters, miscellaneous tees and elbows, solder, and a blowtorch (!!), we got to work. 

Often times that meant one of us jumping up on top of the rig itself and soldering into the existing pipes in the wall/ceiling. This was my first time soldering pipes, so I can't say I was very meticulous at the job. I road home on the subway just filthy, completely covered with a thin layer of hydraulic fluid and probably bits of wall insulation and flux. But I have to say, it was pretty darn fun!
Check out our handiwork below.