Threaded truss foundations and related systems, methods, and machines

1. A screw anchor driving assembly comprising:

a mast;

a rotary driver operable to travel along the mast and to impart torque and downforce to construct a foundation by embedding a screw anchor into underlying ground, wherein embedding comprises screwing the screw anchor into the ground with a combination of torque and downforce so that external threads on the screw anchor engage the ground substantially without augering it;

a screw anchor attached to an output of the rotary driver;

a tool driver on the mast operable to travel along the mast above the rotary driver; and

a tool rod attached to the tool driver and extending through the rotary driver and the screw anchor, wherein the tool driver is operable to independently impart torque and axial force to the tool rod through the screw anchor while the rotary driver embeds the screw anchor into underlying ground, and to withdrawal the tool rod leaving the screw anchor embedded in the underlying ground.

2. The assembly according to claim 1 , wherein the screw anchor has at least one driving feature at the second end for engaging with the output of the rotary driver.

3. The assembly according to claim 1 , wherein the mast is rotatably attached to a piece of heavy equipment.

4. The assembly according to claim 3 , wherein the mast is operable to rotate relative to the piece of heavy equipment to a first angle to drive a first screw anchor into supporting ground, to rotate to a second angle, and to drive a second screw anchor into supporting ground at the second angle without moving the machine, wherein the first and second screw anchors form part of a single truss foundation.

5. The assembly according to claim 1 , further comprising a rock drill bit at one end of the tool rod, wherein the tool driver is operable to drill a cavity in subsurface rock through the screw anchor with the rock drill bit.

6. The assembly according to claim 1 , wherein the tool driver is a hydraulic drifter.

7. An assembly for a screw anchor driving attachment for constructing screw anchor foundations with heavy equipment comprising:

a screw anchor driver operable to construct a foundation by embedding a screw anchor into underlying ground, wherein embedding comprises screwing the anchor into the ground with a combination of torque and downforce so that external threads on the anchor engage the ground to increase the anchor's resistance to pull-out;

a screw anchor attached to an output of the screw anchor driver;

a tool driver positioned above the screw anchor driver; and

a tool rod coupled to the tool driver, wherein the tool driver is operable to independently actuate the tool rod through the screw anchor while the screw anchor driver embeds the screw anchor into underlying ground.

8. The assembly according to claim 7 , further comprising a rock drill bit attached to an end of the tool rod, wherein the tool driver is operable to drill through and ahead of a screw anchor while the screw anchor driver embeds the screw anchor into underlying ground.

9. The assembly according to claim 7 , wherein the driving attachment comprises a mast, and the screw anchor driver and tool driver are attached to and operable to travel along the mast.

10. The assembly according to claim 9 , further comprising a separate motor on the mast that is operable to pull down on the screw anchor driver to transfer downforce to the screw anchor through the screw anchor driver.

11. The assembly according to claim 9 , wherein the mast is rotatably coupled to a piece of heavy equipment.

12. The assembly according to claim 7 , wherein the tool driver is a hydraulic drifter operable to apply torque and a hammering force to the tool rod.

13. A method of embedding a screw anchor for a foundation comprising:

embedding a threaded screw anchor into underlying soil with a screw driver, wherein embedding comprises applying a combination of torque and downforce to a head of the threaded screw anchor so that the threads engage the soil substantially without augering;

at substantially the same time, actuating a tool driver to drive a tool into the underlying soil through the screw driver and the threaded screw anchor to assist embedment; and

withdrawing the mandrel and screw driver while leaving the embedded screw anchor in place.

14. The method of claim 13 , wherein actuating the tool driver comprises applying an axial hammering force to the tool with the tool driver.

15. The method according to claim 13 , wherein if continued application of torque and downforce to the screw anchor fails to result in further embedment:

removing the tool from the screw anchor while leaving the partially driven screw anchor in-situ;

attaching a rock drill bit to the tool;

inserting the tool and drill bit through the partially driven screw anchor;

actuating the tool driver to drill a cavity below the screw anchor with the drill bit; and

embedding the screw anchor into the cavity.

16. The method according to claim 15 , wherein embedding the screw anchor into the cavity further comprises:

inserting a coupling into the cavity through the open screw anchor so that it extends from the cavity into the screw anchor and injecting pressurized fluid around the coupling, wherein the pressurized fluid is selected from the group consisting of grout, cement, resin, and epoxy.