If you say that someone has been thrown on thescrapheap, you mean that they have been forced to leave their job by an uncaring employer and are unlikely to get other work.
Miners have been thrown on the scrapheap with no prospects.
2. singular noun
If things such as machines or weapons are thrown on thescrapheap, they are thrown away because they are no longer needed.
Thousands of Europe's tanks and guns are going to the scrap heap.