The invention relates to a 
visual observation testing 
system for flow characteristics of 
muck in a soil chamber of a single-circle shield. The 
visual observation testing 
system comprises a model soil tank, a 
simulation testing device of a excavation 
system of a reduced-scale single-circle shield, a uniformly distributed load charging device and a PIV 
digital image processing system, wherein transparent soil is contained in the model soil tank, the model soil tank is connected with the uniformly distributed load charging device after an upper cover is removed; one end, provided with a separation plate, of the model soil tank is connected with the 
simulation testing device of the excavation system of the reduced-scale single-circle shield, lasers are distributed above and on the side faces of the model soil tank, a 
CCD camera is used for acquiring images and is connected with a computer for controlling 
image acquisition and analyzing the image data. The invention further discloses a method for performing observation testing by adopting the system. According to the system and the method, visual environment is realized through the transparent soil, the transparent model soil tank, and the transparent 
shield tunneling machine model, and by utilizing the commercial PIV 
digital image processing system, the flow characteristics of the 
muck in the soil chamber and the deformation characteristics of the soil body in front of an excavation face when the 
simulation testing device of the excavation system of the reduced-scale single-circle shield tunnels are directly observed and recorded.