Once all of the piles are stood up in the driving frame, it's time to start putting them into the ground. Sometimes the contractor will start straight away with the diesel hammer. This contractor is using the vibro-hammer, as mentioned earlier. In this photo you can see the first 5 piles on the left have been vibrated partially into the ground. It appears that the hard layer that is stopping this system is dropping off to the right, as you can see by the level that the pile tops are at. The vibro-hammer is seen attached to the top of the 6th pile. The contractor tells me that the process is usually faster than we had here. Each pile took roughly an hour to vibrate into the group. Yes, it makes for a really dull day for the inspector when there is no pile driving to count - but I still had to be around in case they started with the diesel hammer. It's an hour drive from town, or 3 hours from home for me.
Here's what the first set of piles looked like once the vibro-hammering was done:
Soon after the picture above, they setup with the diesel hammer to start driving the piles to their final elevation. This is a much faster process. Each pile took about 15 minutes from setup to completion. The picture below shows the contractor setting the leads and hammer onto the next pile to be driven. You can see the old through-truss in the background. In two years, that bridge will be no more, but it makes for a convenient detour for the time being!
After another couple of hours (plus or minus) we can see the contractor removing the diesel hammer from the piles. Each of these piles are now embedded in the ground just over 8.5 m / 28'. They will constitute the back row of piles for this abutment. The second view shows the same piles from a slightly different viewpoint. This is where I'll leave off until it's time to put in the battered piles. And no, this has nothing to do with baking! (I know someone is thinking about that... come on, you can admit it! ;-D )