著者

木下 尚樹 安原 英明 矢田部 龍一 加賀山 肇

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.133, no.3, pp.45-52, 2017-03-01 (Released:2017-03-31)

参考文献数

17

被引用文献数

1

---

Rockfall is an important geo-hazard of mountainous area in Japan and has gained greater attention and recognition due primarily to the severe accidents and mortalities happening in roadways and railways. Rock fall countermeasures are classified into preventive works and protectors. In rock protectors that have high rigidity, there are rock protecting fence, rock protecting wall and rock shed, etc. On the other hand, there is a pocket type rock net which excels in the application condition of the topography and absorbs energy by deforming itself. The standard absorbable energy of the pocket type rock net is 100 kJ. Then, the rock net is designed so that the absorbed energy exceeds the falling rock energy. However, in recently, many types of rock net such as high energy type and long span type have been developed, and there are cases where conventional design methods cannot be applied. In this study, the performance of a long span pocket type rock net was evaluated by dynamic analysis. Firstly, the physical properties of the rock net members were identified by comparing the results of the real scale field experiments with the dynamic analyses. Then, the relationships between the displacement of the net and the net width, the maximum tensional force of a horizontal rope and the rope position, etc. were evaluated by the dynamic analyses. Typically, these evaluations by conventional design methods are laborious and are carried out using the results of real scale field experiments. However, the current study revealed that the predictions by the dynamic, numerical analyses showed the validity of the performance evaluation by this means.

著者

木下 尚樹 安原 英明 矢田部 龍一 加賀山 肇

出版者

一般社団法人 資源・素材学会

雑誌

Journal of MMIJ (ISSN:18816118)

巻号頁・発行日

vol.138, no.6, pp.70-83, 2022-06-30 (Released:2022-06-30)

参考文献数

19

---

It is obligatory to verify the performance of high-energy-absorbing pocket-type rockfall protection nets by full-scale experiments. While the performance verification by full-scale experiments can provide a practical evaluation, it requires a lot of cost and time because it is necessary to conduct the experiments under several conditions depending on the structure of the rockfall protection net. Therefore, the performance verification by combining full-scale experiments and numerical analysis may be a useful tool. In this study, a full-scale experiment of a high-energy-absorbing pocket-type rockfall protection net was conducted to evaluate the net performance with respect to the required capability, and reusability and repairability of the components by understanding the behavior of the net under the action of heavy weights. Throughout the experiment, the deformation of the net, the change of the wire rope tension with time, and the displacement of the top of the net and the top of the pillar were measured in detail. Moreover, it was confirmed that it is possible to evaluate the performance verification based on the performance requirements. Then, the full-scale experiment was replicated by numerical simulations to examine the effects of the rock shape on the behavior and performance of the simulated net. Through the thorough investigations on the deformation of the net, the relation between the maximum tension of the wire rope and the slip length of the shock absorber, the temporal change of the tension of each wire rope, and the absorbed energy of each structural member, it was judged that the reproducibility of the model predictions is adequately high. Specifically, when the impact energy is constant, the effect of the rock shape on the behavior and performance is considered to be small.