Two construction workers killed at Brisbane's Eagle Farm racecourse managed to escape one falling concrete wall only to be killed by a second, police have alleged, after the builder in charge of the site was arrested at the international airport.

Claudio D'Alessandro, 58, appeared in the Brisbane Magistrates Court on Wednesday on two counts of manslaughter, after being charged on Tuesday.

D'Alessandro was arrested at Brisbane international airport, where he was embarking on a spur-of-the moment, four-day holiday to the Philippines.

The prosecution conceded D'Alessandro had not broken any law by attempting to take the trip.

He was granted bail but was required to surrender his passport and must report to police twice a week as part of his bail conditions.

Ashley Pengana Morris and Humberto Ferraira Leite were killed on October 6 by a falling concrete slab while they were working on a major redevelopment of the stables.

The court was told the men were helping to install a four-walled "foul water settling tank" consisting of four individual walls, each about four square metres and weighing about 10 tonnes.

The walls were lowered individually onto the floor with a crane, with the first three walls, once in place, being "tied" to each other across the top corner by use of adjustable temporary bracing.

Workers 'jumped onto' collapsing wall

A police affidavit stated that the men were working in a "pit" under D'Alessandro's instructions trying to lower the concrete walls when they began to collapse.

The pair managed to "ride down" one concrete slab as it fell but were crushed after the wall's failure caused a second slab to topple forward.

The affidavit stated:

At about 3:40pm, D'Alessandro was in charge of two workers in the pit and to manually assist the correct positioning of the fourth wall as it was lowered into position. The only means of entrance and egress was a steel ladder to the top of one of the walls (panel 2). The pit was only slightly larger than the box made by the walls and the workers had no means of escape other than the ladder. Panel 2 began to fall forward and the two workers managed to scale the ladder on that wall and ride down and jumped onto its back as it fell. The failure of this wall caused another wall (panel 1) to immediately fall forward as it was no longer supported. The two workers were unable to escape the second wall falling and were crushed to death in between the two panels.

The two men were underneath a concrete slab when it fell. ( ABC News )

Ashley Morris raised issues via text, court hears

The court was told Mr Morris had previously commented on a construction issue, and it had been discussed with D'Alessandro via text message.

Police prosecutor Tammy Durre-Bauer said that early in the process of installing one of the panels, "it was identified by one of the deceased - Mr Morris - that the panel did not fit on the concrete pads", and that had been conveyed to D'Alessandro via a text message.

"A series of timber and plastic packers were utilised on top of the gravel base in an attempt to overcome the inaccuracies on the concrete levelling pad," Durre-Bauer said.

"The system in fact had no bracing integrity and was not designed or adopted by an engineer in any manner whatsoever."

The court heard D'Alessandro was an experienced concreter who had worked across the country and internationally.

The prosecutor said D'Alessandro was the sole person issuing instructions and protocols on the site.

D'Alessandro 'shocked by the charges'

His lawyer, Michael Purcell, said his client did not intend to flee and had been free to travel, given he was not under arrest and had been cooperating with the police investigation.

Outside court, Mr Purcell said D'Alessandro intended to plead not guilty.

"He's shocked by the charges. We think that they're premature because the investigation has got a long way to go," he said.

"He's looking forward to getting out on bail and getting back to work."

The case will return to court next month.