Research On Evaluation Of Shock Resistance Performance Of Flexible Shed Tunnel Structure Based On Support Vector Machine

As an efficient rockfall protection structure,flexible shed caves are often used for rockfall protection along railways and highways.At present,there is no relevant standard to explain the impact resistance evaluation of flexible shelters.At the same time,the impact resistance evaluation of the flexible protection net system only relies on the protection energy level as the structural performance index,ignoring the diversity and complexity of the impact load of falling rocks.Based on this,this article has carried out in-depth research on the evaluation of the impact resistance of the flexible shed.The main research results are as follows.(1)With reference to the evaluation method of the passive flexible protective net system,the performance evaluation of the normal working energy level,the maximum test energy level and the ultimate energy level was carried out for the designed flexible shed.The study found that the force transmission path of the intercepting mesh is "X"-shaped.When the falling rock hits the mesh,the mesh and the energy dissipator are the main components that absorb the impact energy of the falling rock.(2)The rockfall propagation trajectory simulation is introduced,and the dynamic response of the flexible shed tunnel is studied by sampling from the probability distribution of six rockfall motion parameters as an impact load.Based on the deformation and impact characteristics of the mesh,four typical failure modes of the flexible shed tunnel are summarized.When the falling rock hits the steel arch frame,the most unfavorable position of the falling rock impact is the top of the steel arch frame;when the falling rock hits the tie rod,the tie rod is prone to damage,which is a weak link in the structure;the angle between the velocity and the tangent vector impacts the falling rock After the mesh rebounds,the state of motion has an important impact;within the maximum test energy level,the traditional evaluation method is more radical.(3)The 6 types of rockfall motion parameters are used as characteristic variables and their corresponding flexible shed failure states are made into a data set,and the data set is divided into a test set and a verification set to train and verify the model separately through a cross-validation grid search method,and finally a third-degree polynomial is selected The kernel function constructs a flexible shed element model based on support vector machine.The prediction results of the meta-model are conservative,and the current evaluation of the impact resistance of passive flexible protection structures is not safe.Therefore,the meta-model can be used as a supplement to the full-scale test to evaluate the impact resistance of the flexible shed.At the same time,the meta-model can assist engineers carry out flexible shed design work.