被动防护网系统强冲击作用下的传力破坏机制

DAMAGE MECHANISM OF ROCKFALL BARRIERS UNDER STRONG IMPACT LOADING

为了研究被动防护网系统在落石冲击作用下的抗冲击力学行为,基于实际工程调查,进行了系统破坏特征的统计与研究,结合现行各国技术现状,分析了关键结构部件的破坏机理,构建了相应的力学模型,开展了750 k J^5000 k J共计5组系统足尺模型冲击试验,针对系统破坏机理、传力变形、耗能原理进行了研究,揭示了系统的破坏演化机制与破坏模式。研究表明:系统的冲击力学行为具有三阶段特征,第二阶段与第三阶段构成了系统的主要耗能机制并对结构整体抗力产生决定性影响;系统结构具有明显的自适应变刚度特征,且该特征与三阶段受力演化过程相互制约;系统的支撑结构、绳索与耗能器布置均是制约系统结构破坏的主要因素,不恰当的配置可导致支撑柱屈曲、绳索破断等现象;提出了新型高性能被动防护网体系,研究表明该体系具备较高的落石拦截能力。研究结果可为被动防护网系统的结构设计提供理论指导。

To study the mechanical behavior ofrockfall barriers under the effect ofrockfall impact, statistics and studies of the system failure characteristics were carried out based on the survey of actual projects. Working mechanisms of the main structure components were analyzed and mechanical models were built. Impact tests of 5 full scale models ranging from 750 kJ to 5000 kJ were carried out. The failure mechanism, mechanism of force-transfering and deformation, principle of energy consumption were emphatically analyzed in combination with the tests and numerical simulations. Damage evolution mechanism and failure mode of barriers were revealed. The results showed that the impact mechanical behavior of the barriers had three stages of evolution under the impact of rockfall. The main energy dissipation of the system was constituted by the second and thirdstages, and the last two stages had decisive effects on tile performance of the system. The mechanical properties of the barriers were similar to tensegrity systems at macro level, but barriers had the characteristic of sell-adaptive variable tension obviously, and it was restricted with the third stage of the evolution. The supporting structure, interception structure and arrangement of the ropes were the main lectors to decide the performance of the barriers hnproper system configurations might trigger destruction of the barriers such as buckling of the steel column, breakdown of the intercepting net, breakage of the rope and so on. At last, a new type of high-performance barriers which had a higher capacity of rockfall interception was put forward. The research results could provide theoretical guidance for the design of rockfall barriers.