All of the sites are on the borders of Gansu province and Xinjiang, some less than 100 miles from Jiuquan, the headquarters of China's space programme and the location of its launch pads.
The two reflective rectangles lie 70 miles from the nearest main road and there is no sign of any surrounding activity. However, Ding Xin military airbase, where China carries out its secret aircraft testing programme, is relatively nearby, at a distance of some 400 miles.
400 miles in the other direction is Lop Nur, the salt lakes where China tested 45 nuclear bombs between 1967 and 1995.
It looks like what article says, that they are for testing explosives.
The really interesting thing would be finding out what cities and stuff they resemble. In some of the things you can make out a highlighted target. Disconcertingly, they seem to be designed based on feet rather than meters.
Also, a couple years ago they found a scale model of the Karakoram Range (disputed between Pakistan, China, and India) in northeast China. That was pretty odd too. I forget exactly where that is.