"Normal" suggestions: earmuffs or earplugs; soundproof your bedroom (IIUC certain types of window roller shutters can mitigate noise); move :/
Insane suggestion: record the dump trucks every night (using good microphones - maybe even hire some), build up a compendium of recordings, get a really good speaker and amp setup (absolutely no buzzing/hissing/hum etc), then play the recordings in a loop progressively increasing the playback volume throughout the night so it's as loud or even louder than the actual dump truck when it arrives. In this way you may be able to acclimatize (exposure therapy). It's quite reasonable that you might need to raise the volume very slowly to begin with (maybe even have the playback volume effectively muted at the start of the night) such that it's still very quiet by 4am and you might still get woken up by the dump truck and then need to stop the playback for the night to get back to sleep; the idea/hope is that you would be(come) able to increase the volume to the necessary level by 4am and stay asleep, this may take a few goes. It's also possible that quality of sleep might not be absolutely 100% to begin with (perhaps turn down the volume/progression if this is the case). It might work though? (I wonder if this would fall within the 2-week habit-forming period, such that you'd acclimatize within a fortnight...)
Insane suggestion: record the dump trucks every night (using good microphones - maybe even hire some), build up a compendium of recordings, get a really good speaker and amp setup (absolutely no buzzing/hissing/hum etc), then play the recordings in a loop progressively increasing the playback volume throughout the night so it's as loud or even louder than the actual dump truck when it arrives. In this way you may be able to acclimatize (exposure therapy). It's quite reasonable that you might need to raise the volume very slowly to begin with (maybe even have the playback volume effectively muted at the start of the night) such that it's still very quiet by 4am and you might still get woken up by the dump truck and then need to stop the playback for the night to get back to sleep; the idea/hope is that you would be(come) able to increase the volume to the necessary level by 4am and stay asleep, this may take a few goes. It's also possible that quality of sleep might not be absolutely 100% to begin with (perhaps turn down the volume/progression if this is the case). It might work though? (I wonder if this would fall within the 2-week habit-forming period, such that you'd acclimatize within a fortnight...)