Invading bamboo

Five years ago my husband planted a green bamboo which is now totally invading our garden. He didn't put it in a pot even though I told him to! In the meantime it's 12 feet tall, going under a path to reach the opposite side of the garden and creating havoc in my flower bed popping up all over the place. The problem is that he planted it and then put a 10 inch gravel layer on top of the section where the bamboo is. Despite this, it's also growing thru the gravel and even protruding from my rockery. How can I now either kill it off or get it under control without digging up all the gravel? I'm desperate. Any suggestions are very welcome.