| Debris flow disasters occur frequently in China,resulting in serious losses of people's lives and property.At present,engineering treatment is the most effective way to prevent debris flow.However,most of the research on control structures only consider the effect of slurry impact on the barrier dam,or only consider the extreme case of boulder impact on the barrier dam,or consider the debris flow slurry as static load and boulder as dynamic load,without considering the coupling dynamic impact effect between the slurry-boulder-barrier dam.The coupling model is also not used to analyze the impact of debris flow velocity decay changes,impact time history,dam key point displacement time history,dam damage and other dynamic behaviors and the impact of blouder shapes on impact force between debris flow control structures in the channel.In order to solve the above problems and reproduce the occurrence and development process of debris flow,firstly establish a three-dimensional model of dynamic coupling of slurry-boulder-barrier dam,and carry out the dynamic behavior of common grille dams and gravity dams under empty and semi-reservoir conditions.Researched.Then the permeable dam and the check dam were combined,and three working conditions of grille-gravity dam,grille-grille dam and gravity-gravity dam were set up to respond to the dynamic response and energy of multilevel fencing dams under the impact of debris flow.Dissipation is analyzed by numerical simulation,and its prevention and control effects are quantitatively judged.The results show that:(1)When the grille dam is empty,the velocity of debris flow slurry and boulder decreases significantly,especially the velocity of boulder decreases almost twice as much as that of half reservoir.In order to reduce the velocity of debris flow passing through the dam,it is necessary to clean up the deposit in front of the grille dam in time.The larger the radius of the primary impact rock is,the greater the impact force is;the size of the secondary impact force has nothing to do with the radius of the rock;the slurry impact force and boulder impact force of the half reservoir are far less than those of the empty reservoir,which indicates that the impact state of the empty reservoir is the most dangerous situation of the grille dam.Therefore,the spatial coordinate interaction between grille columns can be ignored in the analysis of grille columns.The displacement of impact point will appear many times in empty and half storehouse,which is 59% higher than the first peak.Special attention should be paid to in design.The peak displacement of the impact point of block rock(41.2mm)appears in the half reservoir,and the peak displacement of the key point of the grille dam(35.2mm)also appears in the half reservoir.It is indicated that the half reservoir condition is the most dangerous situation of displacement control of grille dam,and the impact of boulder on the grille dam is great.Therefore,the anti scour layer can be set in front of the dam to prevent the boulder from damaging the local impact of the dam body.The peak stress of the grille dam appears at the impact point of the boulder,which indicates that the threat of the boulder to the grille dam is greater than that of the debris flow slurry.The kinetic energy of debris flow slurry and boulder is greater than that of half reservoir,which indicates that the reverse slope of half reservoir has obvious buffer effect on debris flow.The kinetic energy of half reservoir is larger than that of empty reservoir,that is,the displacement of half reservoir grille dam is larger.The internal energy of the dam body under the condition of empty reservoir is greater than that of half reservoir,which indicates that the grille dam under the condition of empty reservoir consumes a lot of energy and is easy to be damaged.(2)The kinetic energy of the debris flow through the gravity dam is large,the slurry will form scour pit in front of the dam,and the boulder is easy to form smash pit.The interaction of the two will form serious scour to the foundation of the gravity dam,leading to the instability of the dam.The second impact threat of debris flow slurry is greater than the first impact,especially in the half reservoir condition;the boulder will impact the dam several times,and the impact times in the empty reservoir condition are more than the half reservoir,and the impact force after the second and second impact is less than the first impact;the peak impact force of debris flow slurry and boulder in the half reservoir condition is greater than the empty reservoir.This shows that the half reservoir is the most dangerous condition of gravity dam in terms of impact force.Gravity dam is not the largest displacement at the top of the dam,because of the impact of boulders,the peak displacement appears in the dam;the half reservoir condition of dam bottom displacement is less than the empty reservoir,and the half reservoir condition is greater than the empty reservoir;this shows that the stop silting in front of the gravity dam controls the displacement at the bottom of the dam and increases the displacement at the monitoring points in the dam and the top of the dam.The maximum stress of the empty reservoir is four times of that of the half reservoir,and all appear at the impact point of the boulder,which indicates that the damage of the boulder impact on the gravity dam is much greater than that of the debris flow slurry.(3)When the primary barrier dam is a gravity dam,the velocity of the debris flow slurry when it contacts the channel after passing the dam is 52% lower than the velocity just after the dam,and the boulder velocity is reduced by 65%.The grille dam has been reduced by 23% and27% respectively.This indicates that the erosion of the foundation of the gravity dam by the debris flow is much greater than that of the grille dam.When the secondary barrier dam is a gravity dam,it can effectively intercept the rocks that have passed the upper barrier dam;when the secondary barrier dam is a grille dam,the boulders passing through the primary grille dam may still pass through the secondary grille dam.Lead to speed up.This shows that when setting up a grille-grille dam multi-level disaster mitigation and prevention project,the spacing between the beams of the secondary grille dam should be smaller than that of the primary grille dam,so as to trap more solid matter in order to achieve the effect of material regulation.(4)When the slurry impacts the grille-grille dam combination dam,the impact force is the smallest and the dam body is safer;when the boulder impacts the gravity-gravity dam combination dam,it is safer.When the first level dam is grille dam,the effect of reducing the reaction force at the monitoring points of the second level barrier dam is better than that of the gravity dam.The maximum von Mises stress of the first gravity dam is 946.23 times of that of the second gravity dam.The energy consumption effect of the first gravity dam is obvious,and the impact damage is easy to occur.The kinetic energy and internal energy of the first and second grille dams are greater than that of the gravity dam,which indicates that the grille dam has good energy consumption and drainage effect. |
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