Research On Characteristics Of Hydrodynamic Pressure By Earthquake In Buried Water Supply Pipeline

Earthquake hydrodynamic pressure is one of the main hydraulic factors as an effect of underground water supply pipeline operation.Through the research on the variation characteristics,the earthquake resistance design of underground water supply pipeline can be provided.The research on this issue has great meaning both in theory and reality.The paper presents methods of earthquake hydrodynamic pressure at the present stage and fluid solid coupling theory,By conducting research based on a combination of structure dynamics,fluid mechanics,modal superposition theory,seismic response spectrum theory,the computational method is applied to the method of earthquake hydrodynamic pressure to make sure the influence factors in changing variables of earthquake hydrodynamic pressure.Then using the finite element software ADINA influence of seismic loading direction,length,earthquake peak acceleration,pipe diameter,wall thickness,pipe,pipe flow velocity,soil rigidity,buried depth of pipe and pipe bending of hydrodynamic pressure by earthquake in buried water supply pipe.The results are as follows:(1)When the earthquake load acts on the tube axis direction,the earthquake hydrodynamic pressure of the pipe flow is mostly affected by the earthquake acceleration,and the variation of pressure is the most obvious;(2)When the pipe length is less than 100m,with the increase of pipe length,the hydrodynamic pressure of pipe flow increases linearly.The 100m-pipe has a maximum hydrodynamic pressure up to 0.43MPa,is 71.67%of the minimum design value of municipal water supply pipeline.(3)The maximum value of water pressure pipe flow solid coupling is significantly greater than the flow of water pressure using the additional mass method and ratio of PFSI to Padded mass method increases with the length increase.When the length is 100m,the flow tube water pressure using the added mass method is 50.5%.of the value only considering the fluid elastic by fluid solid coupling method.(4)The change of the earthquake peak acceleration has a significant effect on the dynamic pressure of the pipe flow,and the dynamic pressure increases with the increase of PGA with a linear trend.The maximum value is significantly greater than the flow water pressure using the added mass method the value of water pressure pipe using the flow solid coupling method,and with the increase of PGA,ratio of the PFSI to Padded mass method increases,when ap=-0.56g,using the fluid-solid coupling method is 2.18 times the maximum hydrodynamic pressure using additional mass method.(5)With the changes of pipe diameter of pipeline,the maximum value of the dynamic water pressure will decrease with the increase of the pipe diameter and pertain to the linear trend.The maximum earthquake dynamic water pressure of the pipe diameter is 0.4m is 1.29 times the dynamic water pressure of the pipe diameter of 0.8m.(6)With the thickness of pipe of the underground water supply pipeline changes,the maximum value of the dynamic water pressure increases with the increase of the wall thickness and pertain to the linear trend.The maximum earthquake dynamic water pressure of the thickness of 0.06m is 1.08 times the dynamic water pressure of thickness of pipe of 0.02m.(7)When the orientation of flow internally in underground water supply pipeline is consistent with the orientation of the seismic velocity,the velocity of pipe flow has amplifying function acting on the earthquake hydrodynamic pressure,within limits,the scaling effect of the earthquake hydrodynamic pressure is advanced with the growth of the flow velocity.Under the condition that the orientation between the seismic velocity and the pipe internally in underground water supply pipeline is the same,at the representative moment for the earthquake hydrodynamic pressure of 3.9s,the earthquake hydrodynamic pressure increases with the increases of the pipeline flow velocity,and the maximum value of the earthquake hydrodynamic pressure when the initial velocity of pipe flow is 1m/s attain to 75.5%of the condition that the initial velocity of pipeline flow is 4m/s.When the initial velocity is over than 4m/s,the trend growth of the earthquake hydrodynamic pressure has decelerated remark and tends to be stable.The obverse of earthquake hydrodynamic pressure when the initial velocity of pie flow is 6m/s is 99.3%of the condition that the initial velocity of pie flow is 7m/s.(8)When the pipeline material of underground water supply pipeline is changed,the maximum earthquake hydrodynamic pressure decreases with the increase of the elastic modulus of the pipeline material,when the elastic modulus is relatively small,the maximum calculated earthquake hydrodynamic pressure of concrete pipe model was 94.8%of that using PE model.The maximum value of the dynamic water pressure calculated of the steel pipe model is 98.6%of the maximum value of the copper pipe model.Moreover,by comparing the maximum hydrodynamic pressure of the steel pipe model and the high Poisson ratio steel pipe model,the pressure increases with the increase of Poisson.(9)When the rigidity of soil mass of roughing-in space is small,the hydrodynamic pressure will decrease rapidly with the increase of the elastic modulus of soil and the increasing the elastic modulus of soil,the decrease of earthquake hydrodynamic pressure is tending to be gentle.When the elastic modulus of the soil is 44GPa,the dynamic pressure of the pipe flow tends to be gentle.When elastic modulus of soil is 5.7GPa,the maximum value of dynamic water pressure of pipe flow is 1.16 times of the maximum value of dynamic water pressure of water flow when the elastic modulus of soil is 44GPa.(10)With the increasing of embedded depth of pipeline,the earthquake hydrodynamic pressure has a minor decrease,the decrease tend is a linear trend.The hydrodynamic pressure of which the embedded depth of pipeline is 2.5m is 97.5%of the maximum hydrodynamic pressure in the pipeline with an embedding depth of 0.5m.The influence of embedded depth is less.When the underground water supply pipeline is bending,the hydrodynamic pressure in elbow pipe apparently has a greater earthquake hydrodynamic pressure than that in straight pipe at the targeted location.And by calculating,the maximum value of hydrodynamic pressure in elbow pipe is 2.19 times the hydrodynamic pressure in straight pipe.