Mechanical Analysis Of Pile Structure Under Impact Of Massive Debris Flow

Debris flow is a common geological hazard in mountainous and hilly areas.The debris flows in the southwest of China usually carry large amounts of large blocks of stone,which carry huge energy in the middle and lower reaches of the middle and lower reaches,and cause serious damage to various blocking structures in the middle and lower reaches.The pile and forest retaining dam has been more and more applied in the engineering practice of blocking large rock.However,due to the lag of related theoretical research and the non-standard design of debris flow disaster prevention and control,the use of pile and forest structure can not be effectively guaranteed at the technical and economic level.In view of this,the dynamic response of pile forest structure under the impact of debris flow rock mass is analyzed,numerical calculation and corresponding experimental research are carried out,and its structure size is optimized and analyzed.The main work and results are as follows:1.The mechanical model of the impact of pile and forest structure is established.According to the lateral movement equation of pile body and the relationship between pile body and foundation strength,the critical conditions formula of three kinds of failure types are given,which are the overall overturning failure,the bending failure of the fixed section and the bending and shear failure of the impact position.2.Considering the elastic and plastic characteristics of the cantilever end of the pile and the energy loss caused by the bending deformation,according to the mechanical model of the impact of the pile forest structure,from the moment of collision and the energy conservation in the collision process,the impact of the debris flow on the simple supported beam model and the plastic hinge model of the pile and forest structure is derived.The formula for calculating the strike force.3.Based on the above mechanical models,we set up the three pile structure numerical model of pile forest structure.The Ansys Explicit Dynamics software is used to simulate and analyze the dynamic response of three piles with different load positions,pile spacing and different row spacing.The results of numerical analysis are in good agreement with the results of mechanical model analysis.After summarizing and analyzing the results,the influence of pile spacing,pile spacing and load location on the bearing mechanism of pile forest structure is obtained.4.In order to verify the accuracy of the mechanical model and the credibility ofthe numerical results,an experimental study on the dynamic response of the pile forest structure under the impact of the debris flow rock mass was carried out.The strain time history curves of several monitoring points under different working conditions were obtained experimentally.The experimental results are analyzed and summarized,and the obvious discrete data are eliminated.The time history curves obtained from the obtained results agree well with the numerical simulation results.The test pile is consistent with the mechanical model in terms of the strain transfer process and the load distribution mechanism.5.The field observation data of the retaining dam of the qi pan gully pile and forest structure in Wenchuan county are analyzed,and the impact process of the pile and forest structure is speculated and retrieved.In this paper,the three-dimensional finite element numerical simulation analysis of the dynamic impact of the pile retaining dam is carried out,and the stress and strain transfer process and the load distribution of the piles in the pile and forest structure are thoroughly investigated.The related results are in good agreement with the data collected from the field observation.The analysis results can be used to further optimize the structure size of the retaining dam with pile and forest structure,and provide the basis for the strength and stiffness design of pile and tie beam,and can provide reference for similar engineering analysis.