Failure Mechanism and Control of Geotechnical Structures

Geotechnical structures are characterized by magnificent scale and complicated configurations and working conditions. Reinforcement design is imperative for such complicated geotechnical structures. To make the reinforcement design effective and targeted, structural failure mechanism under certain actions must be analyzed because reinforcement is essentially aimed at failure control. The deformation reinforcement theory (DRT) provides a feasible solution to determine the structural failure mechanism and corresponding reinforcement force for failure control through elastoplastic finite element analysis. The central concept of DRT is the unbalanced force, which is a set of equivalent nodal forces representing the resistance deficiency of the structure to withstand given actions. The principle of minimum plastic complementary energy (PCE) is proposed: elastoplastic structures under given actions deform tending to the limit steady state at which the unbalanced force is minimized in the sense of PCE. At the limit steady state, the minimized distribution of the unbalanced force reflects the structural failure mechanism, including the failure position and pattern, and determines the optimal reinforcement force to prevent such failure. For geotechnical engineering, DRT can realize a quantitative and pinpoint reinforcement design method and suggest the principles for reinforcement effect evaluation and structural safety monitoring and forecasting. The physical meanings of the principle of minimum PCE and the limit steady state are preliminarily discussed in viscoplasticity and thermodynamics. Four numerical examples and one engineering application verified by geomechanical model test are presented to illustrate the major conclusions.