The ornamental design for a T-shaped ground jaw, as shown and described.
FIG. 1 is a top right isometric view of a T-shaped ground jaw showing my design, the tubing sealer shown in dashed lines illustrates the environment of my invention and forms no part of the claimed design;
FIG. 2 is a top front right isometric view thereof;
FIG. 3 is a top rear left isometric view thereof;
FIG. 4 is a top plan view thereof;
FIG. 5 is a front elevational view thereof;
FIG. 6 is a bottom plan view thereof;
FIG. 7 is a rear elevational view thereof;
FIG. 8 is a left side elevational view thereof; and,