General:
* Persistent blockade
* Prolonged blockade
* Indefinite blockade
* Unbroken blockade
* Sustained blockade
* Ongoing blockade
* Tight blockade
More specific:
* Siege (implies a complete encirclement and often a military context)
* Embargo (refers to a prohibition on trade)
* Lockdown (suggests a strict restriction on movement and access)
* Stranglehold (emphasizes the suffocating effect)
* Confinement (focuses on the restriction of movement)
The best choice will depend on the specific context and the desired nuance. For example, "siege" would be appropriate if you are discussing a military blockade, while "embargo" would be more suitable for a trade-related blockade.