OK.  This is a follow-up.

"chkdsk /f/r" on the QT database drive concluded with no errors found.  This is not proof-positive that the hard drive is OK, but it's a reasonable indication that the problem lies elsewhere.  The drive itself is a high-reliability HP spinning SATA drive for use in servers.  It's almost new.  Odds are good that it's OK.  

Below is the shutdown sequence, from the debug.log.  I had thought it was a clean shutdown.  Note the time stamp at 16:59:34.  This is the time when I tried to restart bitcoin-QT.  The QT app wrote a blank line with a time stamp, followed by about 20 linefeeds. 

Debug log excerpt follows:

------------- ------------- -------------
2018-01-04 09:10:10 UpdateTip: new best=000000000000000003ddd3acef3ffb6e0317bd5787867662cf5be78010451526 height=437675 version=0x20000000 log2_work=85.507452 tx=168627592 date='2016-11-06 23:37:32' progress=0.591994 cache=1247.9MiB(11040514txo)
2018-01-04 09:10:10 UpdateTip: new best=0000000000000000006a8c4ad505c5f706275d2d57c905bbca07a854b9d7b7bc height=437676 version=0x00000004 log2_work=85.507481 tx=168630170 date='2016-11-07 00:00:05' progress=0.592003 cache=1248.0MiB(11041537txo)
2018-01-04 09:10:10 UpdateTip: new best=0000000000000000036dea4c8b425afd7ff0be1b9cb8dbd4adc9cf57b38bcaa1 height=437677 version=0x20000000 log2_work=85.50751 tx=168630220 date='2016-11-07 00:00:50' progress=0.592003 cache=1248.0MiB(11041589txo)
2018-01-04 09:10:10 UpdateTip: new best=00000000000000000262817365e28f5c5e6631f3078d7c5be68f7133464f5dd6 height=437678 version=0x20000000 log2_work=85.507538 tx=168632547 date='2016-11-07 00:03:04' progress=0.592011 cache=1248.2MiB(11042761txo)
2018-01-04 09:10:10 UpdateTip: new best=0000000000000000031e4b68f1591a920f069b2cdc06f4b34a0210fe870105bb height=437679 version=0x20000000 log2_work=85.507567 tx=168633976 date='2016-11-07 00:03:20' progress=0.592016 cache=1248.8MiB(11048687txo)
2018-01-04 09:10:11 UpdateTip: new best=00000000000000000336fb38dc25f841246536540b3a007d67819caccb210d9b height=437680 version=0x20000000 log2_work=85.507596 tx=168634706 date='2016-11-07 00:03:58' progress=0.592019 cache=1249.1MiB(11052010txo)
2018-01-04 09:10:11 UpdateTip: new best=00000000000000000074136a39836a35fdb36a872339d3b036cb10b28b6876ed height=437681 version=0x20000000 log2_work=85.507625 tx=168636123 date='2016-11-07 00:11:23' progress=0.592024 cache=1249.5MiB(11055343txo)
2018-01-04 09:10:35 tor: Thread interrupt
2018-01-04 09:10:35 opencon thread exit
2018-01-04 09:10:35 torcontrol thread exit
2018-01-04 09:10:35 addcon thread exit
2018-01-04 09:10:35 net thread exit
2018-01-04 09:10:35 scheduler thread interrupt
2018-01-04 09:10:35 Shutdown: In progress...
2018-01-04 09:10:35 msghand thread exit
2018-01-04 09:10:35 Dumped mempool: 0s to copy, 0.046998s to dump
2018-01-04 09:14:19 Shutdown: done
2018-01-04 16:59:34