Hello, I’m Troy Schmidt from Geoprobe®. Today we’re going to talk about anchoring the 3230 for CPT pushing.
The 3230 is unique to the industry in that it can do direct push work, can do rotary work, and we can switch to do CPT as well. In may applications in the field, there is a case where we could push CPT a distance and then we have to do some augering to clear a hole before we can continue pushing CPT. This is the only rig in the industry that is like that. Many other rigs don’t have the down-force or the capability to push CPT and do the drilling. So it’s a very unique feature we have here on the 3230.
So to push CPT with the 3230 we need some reaction, so we have some static weight in the rig, in the head itself that accomplishes part of that weight force. But we also need earth anchors to get more reaction. In order to do that, we’ll use some screw anchors to screw into the ground and that will give us the reaction that we need.
The next element is an anchor itself - common anchor with a pinning bracket that we use for all of our rigs for anchoring. The last item is the anchor bridge and that is used to hold the foot to the ground as we begin to do our push. We have extensions to add on as well to get deeper if necessary, a beam that goes across the toes to tie the rig to the platform , a couple anchor pinning brackets that will hold it to the anchors, and then an adapter that is used for corded CPT that is attached to the head.
To set the anchors and do pushing with CPT on the 3230, we have an adapter from the spindle down to 1 ⅝” . With that we can screw the anchors in and we also have a push / pull cap for pushing seismic or CPT with a cable that we’ll put into place to perform that operation.
To begin anchor setup, the drill mast is extended and swung to the operator side. A 10 inch diameter anchor is advanced to depth using the standard auger drive on the 3230DT. The rig is then tracked back and over slightly and the mast is swung towards the helper side to advance a second anchor.. The second 10 inch diameter anchor is installed approximately 30 inches from the first anchor. The drill mast is then positioned over the anchors using the tracks and drill mast swing and extend functions.
Next, the anchor bridge beam is placed over the anchors and onto the drill mast foot. Two anchor pinning brackets are connected to the anchors to hold the drill mast to the ground for pushing.
Once anchoring is complete, the CPT logging equipment is setup. A stringpot tracks vertical movement of the head to record logging depth. The end of the string is secured to the drill mast. A seismic CPT push / pull cap is attached to the spindle adapter.
The rig is now setup to begin pushing the CPT cone. Automatic head feed rate control advances the cone at the steady 2 centimeters per second specified by ASTM Standard D5778. Rods are added until the desired logging depth is reached. A rod bushing is placed on the rod guide to to keep the rod centered while pushing. The 3100GT has 25 tons of push and 40 tons of pull.
Once logging is complete, the CPT system is ready to be retrieved from the subsurface. A pull cap is placed on the top of the rod string. This allows for pulling each rod interval. The string pot attached to the drill head can be removed at this point. Next, the pinning brackets are removed from the anchors. The anchor bridge beam is then removed. Using the tracks, swing, and extend functions, the two anchors are removed using the auger drive function. This completes CPT logging with the 3230DT.
We showed you today how easy it is to setup the 3230 with earth anchors to push CPT. The 3230 is unique to the industry in that it can do direct push work, can do rotary work, and we can switch to do CPT as well. If you need any more information about this rig please call us at Geoprobe®.