The phrase "heaps of ash" is correct and can be used in written English.
It refers to a large amount or pile of ash, usually from burned materials. This phrase is typically used in more informal or descriptive writing, rather than in a formal or professional context. Example: After the fire, all that remained of the old cabin were heaps of ash scattered across the forest floor.
At the town's western edge, we approached desolate, gravelly foothills of the sort that John Muir might have seen in 1878, when he described Nevada's ridges as "gray and forbidding and shadeless, like heaps of ashes dumped from the blazing sky".
Half an hour later, his home of 33 years had been reduced to a smoldering heap of ash and twisted metal. .
Below them the town of Engadda [Engedi] once stood in its palm groves and general fertility second only to Jerusalem, but now a heap of ashes like it.
Verbal threats from North Korea, which has at various points vowed to turn South Korea into a "sea of fire" and a "heap of ashes," are a recurring feature of postwar relations between the two countries.
By staring expressionlessly into the middle distance and shaking my head, maintaining my stride, I hope to convey the message that I know they have a job to do but, should they attempt to talk to me, a plague of locusts will rain down on their heads and their houses will be reduced to a heap of ashes.
But now, I am prepared to accept that we will all have to be more closely monitored Under this government, British values boil down to economic whoredom, monetary privilege and the bottom line You see brown and black-skinned Britons on Question Time whose views would make Nigel Farage blush How do you measure rekindled imaginations - hope grown in a heap of ashes?
To counter the objection that cremation would interfere with resurrection, the Reverend O. B. Frothingham assured Americans that "to recover a shape from a heap of ashes can be no more difficult than to recover it from a mound of dust".
"The nuclear warmongers should bear in mind that if they show the slightest sign of aggression, it would turn the stronghold of provocation into a heap of ashes through a Korean-style preemptive nuclear strike".
