The phrase “a scrabble of rocks” is a rather unique and vivid description. Here are some possible synonyms:
“A jumble of rocks” implies a disorderly heap or mixture. For example, “We came across a jumble of rocks at the bottom of the hill.” It gives the sense of chaos and disarray similar to “a scrabble of rocks”.
“A clutter of rocks” also suggests a disorganized collection. “The path was blocked by a clutter of rocks.” The word “clutter” emphasizes the untidiness and randomness.
“A heap of rocks” is a simpler description but still conveys the idea of a pile. “There was a large heap of rocks by the quarry.” It doesn't have the same sense of activity as “a scrabble of rocks” but still indicates a quantity of rocks in one place.
“A pileup of rocks” can be used to suggest a more chaotic accumulation, perhaps as if rocks have collided and piled on top of each other. “The landslide left a pileup of rocks on the road.”