The Mechanics Performance Of Passive Flexible Protection Structure

The past 30 years, China has become one of the world’s most serious geological disasters countries. For a wide range of geological disasters, such as large rockfall avalanches and other scholars, engineers have proposed a variety of measures and methods to deal with. Passive flexible protection is an important rockfall interception structure. However, the use of passive flexible protection indicates that in practical engineering, systems frequently appear damaged, problems such as the failure to intercept, The reason is that the current domestic work have not a clear understanding of the structure, the lack of effective technical control, coupled with its own behavior has a very complex structure, very little research. For the above, take passive protection systems for study, by adopting the combination of full scale test and theoretical calculation method, Full-scale experiment with using a combination of theoretical analysis of its impact test methods, computational theory, structure and design of the mechanical behavior issues such as research methods, the main research contents and results as follows: First,carried out the original size of the passive flexible system rockfall impact integrity test, The overall structure deformation characteristics obtained after rockfall impact through high-speed video cameras to be deconstructed, got movement characteristics of each component, clear all force characteristics by members.Second, establish a framework for the overall calculation of numerical simulation of passive flexible protection. Experimental studies combined with domestic research on each of the components, and flexible working conditions based on the structure of the passive flexible protection,based on the actual working conditions of the structure, the force and deformation characteristic features of constituent members are summarized and analyzed, a two-stage restoring force model of the rope net and a three-stage nonlinear model of the energy dissipating device were proposed and the large displacement slip simulation phase. Based on this, the numerical analysis can reproduce the structure to intercept rockfall impact behavior of the whole process. Test results compared to verify the correctness and validity of theoretical calculations, has laid a solid theoretical foundation for further expansion of the study.Third, reveals the three-stage movement and deformation mode of passive flexible protection. Specific performance:the impact of rockfall, net initial tensioning stage; net mass movement and energy system startup, the system corresponding interception slip stage; movement of the support structure, the yaw drive overall system stage. Each deformation stage movement, there are corresponding force structure, force transmission characteristics match.Fourth, propose a theoretical definition of adaptive variable tension structural system, defining the structural properties of passive flexible protection. The theory can be a complete description of the stiffness variation in impact action process. Rockfall impact of pre-exposure to the weak state of tension, stiffness degrees only to maintain the initial shape; certain period of time after the occurrence of rockfall impact on the growth of tension state; the energy subsystem starts, whichever is the steady state of tension; energy system startup is completed before the transition to tension grew status; finally the breaking state. Based on the performance curve get the normalized model.Finally, the establishment of a design approach based on energy match, the set design to match the energy based on reasonable proportion of the component parts. For each component, the theoretical analysis, to complete its energy configuration design, engineering design method to form a passive flexible protection, to achieve a "to design" and "simple design." Relevant experimental data and numerical results of the comparison proved the reliability of the method.