Themechanical behaviour of joints plays a key role in concrete dam engineering since the joint is the weakest point in the structure and therefore the evolutionary crack process occurring along this line determinesthegloballoadbearingcapacity. Thereferencevolumeinvolvedintheabovementionedprocessisso large that it cannot be tested…
Themechanical behaviour of joints plays a key role in concrete dam engineering since the joint is the weakest point in the structure and therefore the evolutionary crack process occurring along this line determinesthegloballoadbearingcapacity. Thereferencevolumeinvolvedintheabovementionedprocessisso large that it cannot be tested in a laboratory: a numerical model is needed. The use of the asymptotic expansions proposed by Karihaloo and Xiao 2008 at the tip of a crack with normal cohesion and Coulomb friction can overcomethenumericaldifficulties that appear in large scale problems when the Newton-Raphson procedure is applied to a set of equilibrium equations based on ordinary shape functions (Standard Finite Element Method). Inthiswayitispossibletoanalyseproblemswithfrictionandcrackpropagationundertheconstantloadinduced by hydromechanical coupling. For each position of the fictitious crack tip, the condition K = K =0allows 1 2 us to obtain the external load level and the tangential stress at the tip. If the joint strength is larger than the value obtained, the solution is acceptable, because the tensile strength is assumed negligible and the condition K1 =0 is sufficient to cause the crack growth. Otherwise the load level obtained can be considered as an overestimation of the critical value and a special form of contact problem has to be solved along the fictitious process zone. For the boundary condition analysed (ICOLD benchmark on gravity dam model), after an initial increasing phase, the water lag remains almost constant and the maximum value of load carrying capacity is achieved when the water lag reaches its constant value.