| As a dam protection project under the dam,the apron plays an important role in the scour and stability of the dam.Through the investigation of the operation of 206 retaining dams in 66 debris flow gullies in Wenchuan earthquake area,81 retaining dams have different degrees of damage,and the damage rate is as high as 39.3%.The main damage modes are rock impact damage,water erosion and erosion damage.ABAQUS numerical simulation is used to simulate the impact of overturned debris flow on the apron under the dam.Based on SPH smooth particle hydrodynamics principle,fluid-solid coupling theory and impact dynamics theory,the impact effect and damage of debris flow and large stones on the apron under the dam are simulated.The main conclusions of the study are as follows:1.Study on erosion of apron surface and erosion depth of apron leading edge(1)Study on the surface erosion of the apron,analyze the influence of concrete strength and dam height,the stress value of the apron under the four dam heights is less than the ultimate compressive strength of the concrete,and the C30 concrete apron has better erosion resistance.The influence of debris flow scale is analyzed.In the four dam high schools,the three scale debris flows are not easy to destroy the apron,and the damage unit of large-scale debris flow apron accounts for more than 338.5 % compared with small-scale debris flow apron,up to 375.0 %.(2)The scour depth of the front edge of the apron is studied,and the influence of debris flow scale and dam height is analyzed.The scour depth of medium and large-scale debris flows exceeds 1.0 m,and the scope of the scour pit expands,and increases significantly with the increase of dam height.The relationship between scour depth and dam height and scale is established by binary regression model,and the hoe ditch is used as an example to verify the error rate of 9.2 %.Finally,according to the scouring characteristics of debris flow slurry to apron,the corresponding optimization countermeasures of apron are put forward.2.Study on impact effect of block stone on apron(1)The influence of rock particle size and dam height,20 m dam particle size 2m and above rock,15 m dam particle size 3m and above rock,10 m and 5m dam particle size 4m rock,the stress is greater than the standard value of concrete compressive strength,resulting in greater damage;the regression model is established to predict the relationship between the damage area and the dam height and the stone particle size.(2)The influence of concrete strength,in addition to 5m dam,C20 concrete,C25 concrete apron damage is relatively heavy,high dam C20 concrete,C25 apron damage area up to 8.4m2,7.2m2,depth up to 0.36 m,0.31m;finally,a multiple regression model is established to predict the relationship between damage area and concrete strength,dam height and stone particle size.(3)The influence of the thickness of the apron,it can be seen that under the 5m dam,the damage degree of the apron thickness between 0.5m and 0.8m is not much different,but it is greatly affected by the impact of the large stone impact.The thickness of the apron can be selected at 1.0m,10 m,15m,and 20 m dam heights.Finally,the relationship between the damage area of the apron and the dam height,the thickness of the apron and the particle size of the rock is predicted by the multiple regression model.(4)Taking Chutou gully 1 # retaining dam as an example,the impact effect of large stones on the retaining dam apron is verified by numerical simulation.The results show that the fragmentation area of the apron can reach 33.7 m2,the actual fragmentation area can reach 39.0 m2,and the error rate is 13.7 %.Finally,according to the impact effect of block stone on apron,the corresponding optimization suggestions of apron are put forward. |
