Can human activity affect volcanoes?
I think you have drawn the 'short straw'! As disasters go, volcanoes have about the least to do with human activity. Basically, volcanoes are the product of plate tectonics, which operates on a scale vastly greater than human impacts on the planet. At least one book has been written about earthquakes, volcanoes and human impacts, but the linkage is tenuous at best. The argument goes something like this: Humans modify the water table by pumping, diverting water, building dams, etc. Also by human-induced climate change contributing to rising sea levels. Increased hydrostatic pressure in the ground 'lubricates' fault planes causing lesser but more frequent earthquakes. In and around volcanoes, there is more groundwater which increases water vapour in/near magma chambers, and hence increases the activity of volatiles, contributing to volcanic eruptions. 

This is all speculative, and most geologists doubt whether these effects are significant, or even if they exist at all. I think you will have a hard task trying to provide supporting evidence for any of this.

On the other hand there is passive interaction in that many terrestrial volcanoes in wet climates produce vast quantities of volcanic ash that weathers rapidly to produce fertile soil. This fertility attracts farming communities who put themselves in harms way, being at risk from hot ash clouds, hot lava, volcanic bombs and mudflows. The latter are produced by hurricane level rainfall mobilizing the loose ash, such that mudflows (or 'lahars') kill far more people than the volcanoes themselves - we have seen many examples in the news in recent decades - in South and Central America, Indonesia, Philippines, etc. 

The Mount St. Helens eruption was caused by the Juan de Fuca tectonic plate subducting under North America. It's a 100% natural process, with no human causation whatever. 

There are no known cases of fracking having any impact upon volcanoes. Can you imagine any fracking company taking the legal risk of setting off a volcanic eruption? In any case, the basic geology of volcanoes and hydrocarbon bearing sediments is quite different.