Melbourne: Top global miner BHP Billiton shelved its planned $20 billion (Dh73.5 billion) Olympic Dam copper expansion on Wednesday as it reported a 35 percent slide in second-half profit in the biggest sign of the pain inflicted by the slowdown in China’s economic growth.

BHP reported its first annual profit fall in three years in the face of rising costs and falling commodity prices, wrapping up a torrid earnings season for the world’s biggest miners.

They were all battered by weaker prices for iron ore, copper, coal, nickel and aluminium as economic growth in big-buyer China slows to its weakest pace in a decade.

BHP CEO Marius Kloppers said the company needed to take a fresh look at the massive Olympic Dam expansion, which had been due for a final decision in December, in light of the tough market conditions.

“As we finalised all the details of the project in the context of current market conditions, our strategy and capital management priorities, it became clear that the right decision for the company and its shareholders was to continue studies to develop a less capital intensive option to replace the underground mine at Olympic Dam,” he said in a statement.

The Anglo-Australian giant has also been hurt by lower natural gas prices and industrial action at its coking coal mines, with its bottom line marred by $2.5 billion in writedowns on its shale gas and nickel assets and charges on projects, including Olympic Dam.

BHP’s second-half attributable profit before exceptional items fell to $7.16 billion from $10.98 billion a year earlier, as calculated by Reuters from the full-year results. That was slightly ahead of analysts’ forecasts around $6.96 billion.

BHP’s full-year profit to the end of June fell to $17.1 billion from $21.7 billion a year earlier.

In BHP’s biggest business of iron ore, softening demand growth from China has been particularly painful. The world’s biggest iron ore miner, Brazil’s Vale, last month reported its worst quarterly earnings in two years.

With sharp falls in commodity markets this year, analysts and investors had been looking for signs of future capital spending cuts. Although there has been spending restraint at the fringes, none of the heavyweight miners has yet cut back on core growth projects.

BHP flagged in May it was putting the brakes on an $80 billion plan to expand its operations, and investors were keen for an update on whether it was going to delay three major projects -- Olympic Dam and the Outer Harbour iron ore development, both in Australia, and the Jansen potash project in Canada.

All three were due to go to the board for final approval by December 2012.

Construction contractors are already getting nervous about an end to the mining construction boom, although they say it should help ease cost pressures on existing projects for workers and materials as demand growth slows.

“I think that we are close to the current peak of construction work,” Nick Bowen, managing director of mining services company Macmahon, told Reuters this week.

Cost cutting at operations will also be a key factor under scrutiny, with BHP having recently flagged it may have to cut jobs at its Australian coal mines due to worsening market conditions.

BHP raised its final dividend by 2 cents to 57 cents, but that was below analysts’ forecasts of around 58 cents, which was seen as a sign of caution on the outlook.

As expected, BHP revealed earlier this month it would book a $2.8 billion writedown on the US shale business it had bought last year and $450 million on its Australian nickel division, which led Kloppers and petroleum head Mike Yeager to forgo their bonuses this year.