The invention discloses an active and passive
instability teaching demonstrator of a shield excavation face. An opened model box is formed by a
front panel made of
organic glass, three shield body sections are hollow semi-cylinders with same
diameter, plane parts of the three shield bodies are sequentially parallel to a bottom plate from top to bottom and are clung to the inner side face of an
organic glass plate of the model box, pressure bearing baffle plates, barrels and mobile brackets are sequentially coaxially arranged in the hollow semi-cylindrical surfaces of the right sides of the three shield bodies; lead screws on one ends of three step-shaped long shafts respectively penetrate through respective mobile brackets to be threaded with the barrels, left sides of the three shield bodies are abutted with a left side plate, the other ends of the three step-shaped long shafts penetrate through the left side plate, a
metal substrate, gear inner gear baffle gaskets, gears and gear outer gear baffle gaskets to be threaded with nuts on respective shaft ends; and the three gears are fixed on respective shafts by using respective location screws. According to the active and passive
instability teaching demonstrator, the deformation and damage process of soil bodies before the pressure bearing baffle plates under three depths can be demonstrated, and the damage condition of the soil bodies can be statically observed under any displacement. The active and passive
instability teaching demonstrator can meet the classroom teaching demand.