I have been requested to write an article on Woosung Forts in Shanghai for a Chinese magazine. While going through the photos I have collected, I found this interesting photo apparently showing some small caliber guns(compare with the soldier).
Accroding to some sources in late 1890s(or early 1900s, can't remember), Woosung Forts were equipped with a number of "Armstrong 5.7cm QF guns",so I guess these may be the 57mm piece.
The guns referred to as Armstrong QF 57mm may be the Armstrong-Mitchell 6 Pounder gun (Hotchkiss 6 Pounder built under licence). This gun started out as a naval gun used in the anti-torpedo boat role in the 1880-90s. By the latter part of the 1890s the 6 Pounders were obsolete in their intended role but many of them were deployed in coastal defences and on small ships. The same gun was recycled in WW1 as the gun in the Male tanks.
The image in the post seems to be of guns bigger than the 6 Pounder - although there are similarities to the 6 Pounder - possibly they are 12 Pounder guns.