Analysis Of Damage Failure And Reinforcement Measures Of Masonry Structure Under The Impact Of Debris Flow

Debris flow is a global disaster problem that often occurs in mountainous areas with low vegetation coverage and abundant rainfall.With the continuous accumulation of the global greenhouse effect,extreme weather such as heavy rains frequently occur and often cause large-scale debris flow.Therefore,the probability that the building structure will be impacted by mudslides will increase,which will cause damage to buildings and even casualties.At present,most of the research on this problem is concentrated on the genesis and dynamic characteristics of debris flow,while the research on the damage caused by the impact of debris flow on the structure is relatively rare.Most of the buildings in the mountainous areas are built on the ground,that is,they are built in the form of blocks such as stones or homemade bricks.They are relatively rigid,but the mudslides usually carry large stones and have the same speed as the fluid.The impact damage effect on masonry buildings in mountainous areas is quite large.In-depth study is needed to give a quantitative evaluation of the impact resistance and damage of masonry buildings under the action of debris flow,and the characteristics of interaction between debris flow and structure are obtained.The damage and failure characteristics of the masonry structure provide the basis for the repair and reinforcement of the building.Based on this,this paper establishes a finite element model of two masonry structures in the mountainous area impacted by debris flow,to simulate the dynamic damage behavior of masonry structure under the impact of debris-bearing debris flow,and obtain the impact time history curve and different fluid impact velocity.The strain distribution and propagation characteristics of the lower masonry structure,the discrete characteristics of the block damage and the damage range.Finally,a safe solution is proposed for two different masonry structural features and their effectiveness is verified.The main work and conclusions are as follows:The basic concepts and general characteristics of debris flow are introduced.The motion parameters affecting the impact of debris flow are studied and summarized in detail.It is pointed out that the existence of stones in debris flow is an important factor in the damage of masonry walls.The calculation model of discretized masonry structure is established by LS-Prepost,and the contact algorithm replaces the mortar bonding effect.Compared with the integral calculation model,it simulates the mutual displacement between the blocks and the crack distribution when the mortar fails.The dynamic responses of two masonry structures with or without ring beam structure under different flow velocity debris flows are compared.The stress distribution and propagation of masonry structures under the impact of large rocks are studied.The results show that when the pure masonry structure is impacted by the high velocity debris flow,the impact wall loses its weight bearing effect,and the bottom house is destroyed first,causing the upper structure to lose support and tilt down.When the masonry structure with the ring beam structure column is subjected to the impact of the high velocity debris flow,only the local damage occurs to the collision wall,the structure does not collapse as a whole,and the critical speed of local failure is higher.It is indicated that the reasonable arrangement of the ring beam and the structural column can significantly improve the structure’s resistance to continuous collapse,thereby reducing the loss in the debris flow disaster.For a column masonry structure with a ring beam structure,the critical failure speed is between 4.5 and 5 m?s,and the critical impact force is between 1000.57 kN and 1021.17 kN.For the frameless masonry structure,the critical impact velocity is between 4 m?s and 5 m?s,and the critical impact force is between 953 and 1051 kN.Based on the above research results,this paper proposes a corresponding protection and reinforcement scheme,that is,adding a protective wall around the wall of the structure facing surface or implanting steel bars in the wall facing the flow wall,and separately calculating and analyzing the results.It shows that the proposed scheme has a good effect.Among them,the reinforced concrete protection structure can withstand the flow of debris flow with a flow rate of 7~8 m?s,and the critical impact force can reach 2357 kN.The C40 concrete is larger than the C30,but the C50 is not much better than the C40 concrete,and the protection performance and economy are recommended.The protective structure uses C40 concrete.For the method of planting ribs,this paper compares the effect of two planting ribs.For the outside of the wall facing the wall,a row of vertical HRB400 three-stage steel bars with a diameter of 22 mm,five equidistant rows and a spacing of 700 mm are used.5~6 m?s is the critical impact velocity,and the critical impact force is between 1209.75~1248.07 kN.The critical speed of the unreinforced masonry structure is increased by about 30%,and the critical impact force is increased by about 23%.For the inner and outer sides of the upstream wall,the vertical HRB400 three-stage steel bar is uniformly implanted with a diameter of 18 mm and a spacing of 130 mm.The critical speed can reach 7~8 m?s and the critical impact force is about 1536.43 kN.The critical speed of the masonry structure is increased by 60% and the critical impact force is increased by about 50%.