The global stability of high arch dam is one of the key problems in the safety study of arch dams, but no feasible method with theoretical basis is available. In this paper, based on the stability theory of mechanical system, it is demonstrated that the global failure of high arch dams belongs to a physical instability starting from local strength failure, which is the extreme point instability according to the characteristics of load-displacement curve obtained from the failure process of dam-foundation system. So the global failure of dam-foundation system should be studied with the stability theory of mechanical system. It is also pointed out that the current stability analysis methods used in engineering are consistent with the stability theory, but not established according to the mechanical system stability theory directly. A perfect method can be obtained through the study of physical disturbance equations. high arch dam, global stability, physical instability, extreme point instability Citation:Ren Q W, Li Q, Jiang Y Z, et al. Theory and methods of global stability analysis for high arch dam.

To get the actual ultimate bearing capacity of concrete dam, the effect of geometric nonlinearity and strain softening on it, which appears in the failure process of concrete dam, is studied. Overload method is adopted to obtain the bearing capacity of a concrete dam by taking into consideration strain softening in the material constitutive law, geometric nonlinearity in geometric equation and equilibrium differential equation. Arc-length method is used to find the extreme point and descending branch of the load-displacement curve of the dam. The results present that the effect cannot be ignored. And geometric nonlinearity of structure and strain softening of materials should be considered for numerical analysis of ultimate bearing capacity of a concrete dam.concrete dam, ultimate bearing capacity, finite deformation, geometric nonlinearity, strain softening Citation:Ren Q W, Jiang Y Z. Ultimate bearing capacity of concrete dam involved in geometric and material nonlinearity.

A general initial water penetration (seepage) fracture criterion for concrete is proposed to predict whether or not harmful water penetration (hydraulic fracturing), other than microcracking, will occur in concrete structures in a severe high water pressure environment. The final regression, of the different macroscopic failure types in concrete to microscopic Mode cracking, a Ⅰ llows the use of only one universal criterion to indicate the damage. Thus, a general initial water penetration fracture criterion is approximately defined as a strain magnitude of 1000×10 6 , based on the concept of tensile strain derived from experimental results in the relevant literature. Then, the locations of harmful water penetration fracture (hydraulic fracture) in the high arch dam mass of the Jinping first class hydropower project are analyzed using the nonlinear finite element method (FEM) according to the proposed criterion. The proposed criterion also holds promise for other concrete structures in high water pressure environments.concrete, initial water penetration fracture criterion, hydraulic fracture, tensile strain, Jinping high arch dam Citation:Jiang Y Z, Ren Q W, Xu W, et al. Definition of the general initial water penetration fracture criterion for concrete and its engineering application. Sci

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