Path of the Earth Breaker

Note:
The goal is to give the barbarian area denial and disruption, allowing them to feel like a strong initiator, and give them a presence in the fight, outside of pure damage.
All saving throws for effects are 8 + your proficiency bonus + your strength modifier.

Shockwave

Starting when you choose this path at 3rd level, when you rage, choose whether or not to stomp the ground, destroying the earth around you in a 20ft radius. The ground becomes difficult terrain, any enemies that are touching the ground in this area take bludgeoning damage equal to your rage bonus. Creatures hit by shockwave must succeed on a strength saving throw or be knocked prone, the dc is equal  to 8 + your strength modifier + your proficiency bonus. Creatures that are huge or larger have advantage, while creatures small or smaller have disadvantage.

Additionally:
Beginning at 7th creatures hit by shockwave must succeed on a strength saving throw or be knocked prone, the dc is equal  to 8 + your strength modifier + your proficiency bonus. Creatures smaller than you have disadvantage, and creatures larger than you have advantage on this saving throw.
You may use your Instinctive Pounce feature to move up to half your movement speed before activating Shockwave.

Unhindered Stride

Beginning at 3rd level, you are immune to the affects of difficult terrain, while on land.

Heave Shrapnel

Beginning at 6th level, while you are standing on difficult terrain, you can use your action to propel shards of earth in a 15ft cone. Any creature in this cone takes 4d4 slashing damage, and must succeed at a dex saving throw or be blinded until the start of your next turn, on a successful save a creature takes half damage and is not blinded.

You can use this feature a number of times equal to your proficiency bonus. Regain all expended uses on a long rest.

Terrain Mastery

Beginning at 10th level, while you are attacking a creature, and that creature is standing on difficult terrain your attack will crit on a 19 or 20.

Fissure

Beginning at 10th level, you can use your bonus action to split the earth with your might,  at a point within 5ft of you, create a 15ft wide and 20ft long rectangle. This area becomes difficult terrain, and any creature within this area when you activate this feat must succeed a strength saving throw or take bludgeoning damage equal to 3d6 + your rage bonus and be knocked prone, on a successful save the creature takes half damage and is not knocked prone.

If a creature targeted by this feature is standing on difficult terrain (This feat cannot benefit from its own difficult terrain until the start of your next turn) the damage becomes 6d6 + your rage bonus. 

You can use this feature a number of times equal to half your rage charges (rounded down), regain all expended uses on a long rest. 

Earthquake

Beginning at 14th level, while raging you can use your action to crush the earth beneath you, in a 30ft radius, any creature within this radius when you activate this feature takes bludgeoning damage equal to 2d8 + your strength modifier + your rage bonus damage. If a creature is standing on difficult terrain when they are hit by this feature double the damage they take. Additionally creatures in this area make are forced to make a strength saving throw or be restrained until the start of your next turn.
The area affected by this feature becomes difficult terrain (this does not activate the double damage thing unless you use this twice in a turn).

You may use this feature a number of times equal to half your proficiency bonus (rounded down).