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Video Summary:

With the 3126GT, you can efficiently complete CPT testing with integrated CPT head-feed rate control, including cone overload protection.

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3126GT geotechnical drill features centerline head side shift

3126GT Geotechnical Drill Rig


Hi, I’m Doug Koehler with Geoprobe Systems® and today we’re going to show you pushing CPT with our 3126GT. Some unique features of this machine are the CPT functionality that’s built into this machine right from the factory. You can turn on the CPT function and it controls your head rate at 2 cm / sec and you can also limit the hydraulic downforce of the machine at 40%, 60%, 80% or 100% of total hydraulic downforce.

Some of the components we’ll be using today are our new 10/12 anchor system. So you can see you’ve got a 10” flight at the leading edge with a 12” flight half way up the extension. This gives you almost double the reaction force. We also have a rod guide - that provides lateral support for the rod string as you get into tougher pushing conditions. We have a bridge that slides onto the toes of the machine and that’s what the anchor pulls against. And then a pinning bracket, and then when we go to pull, we’ll use a rod grip pull handle just like many of you are used to on any traditional Geoprobe® machine.

Setup begins with the drill mast already extended out from the rig. A dual flight anchor is advanced using the standard auger drive on the 3126GT. The first flight is 10” followed by the second 12” flight.

The anchor bridge is then slid onto the foot and the drill mast is retracted back towards the rig. A pinning bracket is then connected to the anchor to hold the foot to the ground for pushing.

Next, a rod guide is attached between the toes to keep the tooling centered as it is advanced.

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 head. The CPT microphone also attaches to the drill head. This is used for pushing the cordless CPT system. A corded CPT system can also be run with the 3126GT by using a seismic CPT push / pull cap. CPT data is recorded into the field laptop.

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. This provides hands-free operation during advancement of each rod. Rods are added until the desired logging depth is reached. A rod bushing is placed on the rod guide to keep the rod centered while pushing. The 3126GT has 15 tons of push and 24 tons of pull.

Once logging is complete, the CPT system is ready to be retrieved from the subsurface. The string pot and microphone attached to the drill head can be removed at this point as well as the rod guide. The head is side-shifted over and a rod grip pull handle is used to pull each rod. Next, the pinning bracket is removed from the anchor. The drill mast is then extended to remove the anchor bridge from the foot. Using the rotary drive, the anchor is removed. This completes CPT logging with the 3126GT.

So there you saw just how quickly and easily you can setup the 3126 to push CPT. Some of the other unique features of this saw the side shift head of this machine, to go from rotary to pushing cone underneath the microphone. When you’re doing your traditional geotechnical borings, you’re not moving the foot of this machine. You’re using the side shift of the head to transition from your auto drop hammer, to your rotary head, or the direct push head if you’re using our traditional Geoprobe® tooling.

Also unique features of this machine for Geoprobe® are the hands-free controls on this machine. You saw I was using this for when I was running the cone system. That controls your head feed and then you’ve also got hands free controls for the rotation of this machine. So if you’re doing rock coring or mud rotary, you can use the hands-free controls. Very nice when you’re doing long runs.

Another feature of this machine is the 7-inch breakout that you saw us using during this video. We swung that in and we clamped the rod to keep it from sliding back down the hole. Very important when you’re running always want to bring your tools back out of the hole.

Another option available for the 3126 is the CPT package. With that you get the computer tray up here at your control panel for easy mounting of your laptop that you’re running your acquisition software on. And then you also get this third toolbox which holds the interface, microphones, cone, stuff like that for when you’re in the field.

If you have any additional questions or would like to see a demonstration of this machine, please don’t hesitate to give a call. Thank you.