| Due to the influence of topography and monsoon climate,debris flow disasters occur frequently in China.Flexible protective structure system is widely used in debris flow control because of its good energy dissipation capacity.The traditional flexible protective net in China is mainly steel wire rope net,while the research on the flexible protective net of other materials is not very sufficient.In this paper,we use the steel strand as the basic components of the cable-net.Flexible cable-net system is formed by the cable-net and fixed system.The cable-net designed in this paper is mainly square.It is convenient for the cable-net in this shape to realize the multi-span connection of the flexible cable-net system and the prevention and control of large-scale debris flow.In practical application,the size and span of our flexible cable-net system can be designed on the basis of the width of debris flow bed.The research method in this paper is a combination of numerical simulation and experimental research,and we studied the dynamic performance of flexible cable-net system under impact load of larg e rock.The protection capability of the system is preliminarily evaluated from two angles that are the numerical value of protection energy and the maximum size of the blocked rock.The specific research contents mainly include the following aspects.(1)Firstly,we have known about the current situation and progress of debris flow prevention and control project.According to these,we determine our own research direction.Meanwhile,we have a preliminary understanding of the mechanical properties of the ma in constituent materials of the cable-net.(2)In this paper,the original size flexible cable-net system with different specifications is designed,and the dynamic response analysis under the impact of debris flow by large rock is carried out by using fini te element analysis software.At the same time,the protection energy in different conditions of flexible cable-net system is calculated by "dichotomy".Then,the protection ability is preliminarily judged from the two aspects of the system protection ener gy value and the maximum size of the blocked rock.The results show that the smaller the number of joints,the larger the aspect ratio,the larger the protection ability of the system.With the increase of the inward angle,the protection ability of the sy stem is first reduced and then increased.(3)Because the flexible cable-net system can only intercept larger sizes of rock,this paper designs a combined network flexible protection system in order to improve its application range.Composite net is mainly composed of cable-net and ROCCO ring-net,which can be divided into three types: pre-separation type,bonding type and post-separation type.Meanwhile,we studied its dynamic performance and protective ability under the impact of large stones.The results show that the protective performance of the bonded composite mesh is optimal when the distance between the cable-net and the ring-net is small,and for the rear split composite mesh,the protection capability of the system is optimal when the combined spac ing is large.(4)According to the preliminary results of finite element analysis,a scale test model is designed and tested on the impact test platform.Then the displacement,acceleration and strain results of the flexible cable-net system under the impact of large rock are obtained.Meanwhile,the experimental results are compared with the corresponding numerical simulation results.And the results are basically consistent,the conclusions obtained in this paper and the accuracy of mechanical propert ies of steel strands and other materials are verified. |
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