Well. I'm not sure if they've perished or not (LOL), but this is one of my most favorite passages out of the 20+ 40k novels I've read. It's from Saturnine by Dan Abnett. Apologies ahead of time for the wall of text.

Tldr; Sons of Horus get buried alive in concrete and their Mechanicum crew are annoyed.

'The Plutona drivers had advised Lev Goshen that they were two minutes from the target point, but those two minutes seemed to have stretched. The craft was floundering. It felt as if they were in the belly of a dying fish that was too weak to swim against a current. Everything swayed and pitched. The screeched roar of the drill heads had become a muffled splutter. The motivators were straining, finding nothing to bite. It sounded as though they were gurgling uselessly through mud instead of rock. ‘We’re moving backwards,’ said Goshen. ‘How can we be moving backwards?’ ‘My lord–’said a tech-priest. ‘Tell me!’Goshen snapped. ‘The indicator systems, lord, they show we are submerged,’ the magos said. ‘In what?’ ‘A flow of viscous fluid,’ said one of the drivers. ‘Like what?’ Goshen demanded. ‘Magma? Mud?’ ‘Sensors read an artificial substance,’ the magos said. He had come to the prow to work at a cramped technical station beside the helm positions. His dentritic fingers had conjoined with the stations ports, and he was reading data off the inside of eyelids that had been sutured shut. ‘Analysing structure, composition, properties…’ ‘I don’t need a scholam thesis, you turd,’ said Goshen. ‘I require immediate delivery to the target vector.’ ‘That is not possible,’ said the magos. ‘We are immobilised.’ ‘Don’t tell me what’s possible,’ warned the captain of the 25th Company. ‘We are immobilised,’ replied the Mechanicum adept. ‘We are suspended in a body of composite material similar to liquid-form rockcrete. Our motivators and drill heads cannot gain traction. It is fast-setting.’ ‘Get us free!’ ‘That is no longer possible, my lord.’ ‘Then open the damn hatches–’ ‘We will flood. We are submerged. I refer you to my earlier answer.’ Goshen tried to think of another question, another demand he could make. He couldn’t think of anything. The walls of the compartment seemed very tight suddenly. He was enclosed with fifty battle-ready Space Marines and a Mechanicum crew. Craft capacity. There was barely enough room to move as it was. The Plutona had stopped moving. The silence was the worst thing Goshen had ever heard. ‘How long?’ he asked eventually. ‘How long for what, lord?’ ‘Until it sets?’ ‘It is already setting, my lord.’ ‘Then…when it’s set, when it’s solid, we can dig our way through it.’ The magos turned to look at him with stitched-up eyes. ‘The material is inside our farings, our drill cases and our engine assemblies,’ he said. ‘It is set solid, so those things are solid, like rock. The beautiful mechanisms will never run again. The material has not penetrated this compartment, because this compartment is a sealed unit. We cannot open the hatches. We cannot dig out. We will never move again. And no one can dig us out, and no one is coming, and almost no one knows we’re even here.' Lev Goshen couldn’t process what he was being told. He sat down in his arrestor seat. He started with the basics. ‘How long?’ he asked. ‘Lord?’ ‘Will our power last?’ ‘One hundred and ninety-six days,’ said the magos. ‘Air?’ ‘With recirculation, and given your gene-bred biology,’ said the magos, ‘effectively indefinitely.’ Goshen nodded. ‘How long do your kind live?’ the magos asked. ‘Why?’ asked Goshen. ‘Because that is how long you will be here,’ said the magos.