Hi Jane
Nant y calch is a farm not to far from where I live and still in existence today (T.L Evans, Nantycalch Farm, Caerphilly CF83 1HQ). You say your relative Evan Evans was killed near Nantycalch so not necessarily related to the Evans' family of Nantycalch Farm but just in case you do find a connection I have burial details of former inhabitants of the farm namely transcribed off gravestones at St Martin's Church, Caerphilly:
1. Thomas Edward Evans (1874-1931) and his wife Gertrude (1877-1961)
2. Hubert Leslie Evans born at Nantycalch Farm 23 April 1919, died at Crudewell, Wiltshire 7 Aug 1977 and Leonard Courtney Evans of Nantycalch Farm 14 Feb 1912-29 Oct 1985.
3. Thomas & Joan Evans Nantycalch Farm
Edith Lille Maude, daughter, died 27 March 1881 aged 1 year old
Arthur John, son, died July 20, 1881, aged 9 weeks
Florence Louisa Joan, daughter, died 24 Jan 1884, aged 8 months
Mildred, daughter, died 19 Dec 1888, aged 19 months
Bertie, son, died 10 April 1903 aged 13 years
Regards
Roy