Taking a chamber structure on rock foundation for example,we discuss the stress characteristics of the keyway lock chamber and the dock lock chamber.Surface to surface contact element Targe170 and Conta173 are applied to simulate the nonlinear contact of keyway and analyze the stress,moment and foundation stress of the keyway lock chamber under four working conditions:inspection condition,low water condition,finished condition and high water condition,and compare with the dock chamber.It is shown that the stress,moment,and foundation stress rules of keyway chamber are similar to the dock chamber,and its value are small under the inspection condition and low water condition,and the bottom center has a greater negative moment under the inspection condition.While under the finished condition the bottom positive moment of two models is the maximum between four kinds of working conditions,18 016 kN?m,31 163 kN?m respectively,and the value of the dock lock chamber is comparatively large,indicating that the presence of the keyway joints can effectively reduce the positive moment of the chamber bottom.This condition also has the maximum stress foundation.It is also found that under high water condition the two models have the maximum tensile stress on both sides of the top center of bottom,and have congenial value.The middle moment of the keyway lock chamber bottom is smaller than another model’s under this condition.