Hefty write-downs bruised an otherwise strong profit for the year to June 30 by BHP, the world’s biggest mining company.Before writing down $2.7 billion on its mothballed nickel business and providing a charge of$3.8 billion for the 2015 failure of the Samarco dam at a Brazilian iron ore mine, BHP’s underlying profit was up 2% at $13.7 billion.But after the write-offs the full year profit was down 39$7.9 billion, earned from a 3% increase in revenue at $55.7 billion.The Australian-based miner also tri ...