| The material parameters of asphalt concrete core wall dam-overburden foundation system have spatial variability,which often have a great influence on the liquefaction and seismic response of overburden and dam body.Firstly,a random finite element analysis method for liquefaction and response of asphalt core wall dam-overburden foundation considering pore pressure-response coupling is established,secondly,the effects of spatial variability of overburden materials on liquefaction and seismic response of liquefied fine sand interlayer in the case of no overlying dam and overlying dam body are analyzed,and finally the effects of pore pressure-response coupling and spatial variability of overburden and dam materials on the pore pressure characteristics and seismic response of the upstream dam body of asphalt concrete core wall dam are studied.The variation of soil pore pressure and the seismic response characteristics of core wall dam in saturated overburden were revealed.The main research contents and conclusions are as follows:(1)A pore pressure-response coupled effective stress analysis method is established,which considers the process of pore water pressure growth and shear modulus decreasing with the decrease of effective stress under the vibration load of soil.The influence of spatial variability of overburden parameters on liquefaction and seismic response without overlying dam was analyzed.The analysis results show that the fine sand interlayer in the saturated overburden is prone to liquefaction failure under the action of earthquake,and the pore pressure ratio of a large area in the middle of the fine sand interlayer reaches 0.7 at 6 seconds of earthquake,and the liquefaction failure area penetrates the entire fine sand interlayer at 14 s,compared with the dynamic response analysis results without considering the pore pressure-deformation coupling,the horizontal acceleration amplification coefficient at the top of the overlay layer is reduced by 10.98%and the vertical acceleration amplification coefficient is reduced by 28%.After considering the spatial variability of the overburden material parameters,the distribution of liquefaction failure areas of fine sand interlayer was discontinuous,and there was a 30.5%probability that the pore pressure ratio value in the most serious liquefaction failure area in the middle of fine sand interlayer exceeded the determined value.(2)A two-dimensional finite element model of the overburden-asphalt concrete core wall dam system was established,and the influence of spatial variability of overburden materials on the liquefaction law of fine sand interlayer and the dynamic response of core wall dam under the condition of overlying dam body was analyzed based on the effective stress analysis method of pore pressure-response coupling.The analysis results show that due to the large initial compressive stress provided by the overlying dam body,the pore pressure ratio at the fine sand interlayer of the dam foundation below the axis of the asphalt concrete core wall dam is 0.32 after the earthquake,and no liquefaction failure occurs,and the liquefaction failure is the most serious in the absence of the overlying dam body,indicating that the pressure weight above the soil body will effectively increase the liquefaction resistance of the soil.Compared with the dynamic response analysis results without considering pore pressure-deformation coupling,the horizontal and vertical acceleration amplification coefficients of asphalt concrete core wall dam top decreased by 21.7%and 6.2%,respectively,indicating that after considering the pore pressure-deformation coupling of the overburden layer,the soil will absorb seismic energy,and its acceleration response results will decrease.After considering the spatial variability of overburden materials,the deterministic analysis results of soil at feature points were larger than the average value of the random results of materials,and 30.5%of the random calculation results of the areas with the most serious liquefaction failure exceeded the deterministic calculation results,and the liquefaction failure range was distributed in blocks,indicating that ignoring the spatial variability of soil materials would lead to a large range of liquefaction failure.(3)Considering the coupling of pore pressure-deformation of the upstream rockfill body,the influence of spatial variability of overburden and dam material on system liquefaction was studied,and the results showed that the pore pressure growth process of upstream rockfill had little effect on the development of the pore pressure ratio of the fine sand sandwich layer of the overburden layer,and the maximum pore pressure ratio at the foot of the upstream rockfill body was 0.37,and no liquefaction failure occurred,while after considering the spatial variability of the overburden-core wall dam material,the random calculation result of 43.5%of the pore pressure ratio at the area with the most serious liquefaction failure in the upstream exceeded the deterministic calculation result.Compared with the mean value of the random analysis results of pore pressure coupling considering the overburden and upstream pore pressure-response coupling of the soil in the area with the most serious liquefaction failure upstream,the mean value of the random analysis result of pore pressure that only considers the pore pressure-deformation coupling of the overburden increased by 8.74%,indicating that the pore pressure-response coupling of the upper cover layer and the dam body made the upstream fine sand interlayered soil more prone to liquefaction failure.(4)Considering the pore pressure-response coupling of the upstream rockfill body of the dam body,the spatial variability of the overburden and dam material parameters on the dynamic response of the system was studied,and the results showed that considering the influence of the pore pressure-response coupling of the rockfill body upstream of the dam body on the dynamic response of the system,the horizontal and vertical acceleration amplification coefficients decreased by 9.01%and 2.89%,the horizontal permanent deformation increased by 7.02%,and the vertical permanent deformation increased by 19.09%,respectively.The results show that considering the process of pore pressure growth of rockfill upstream of the dam body,the energy generated by the earthquake is absorbed,but the soil deformation increases,resulting in the permanent deformation of the dam body.Considering the spatial variability of overburden soil and dam materials,the minimum horizontal acceleration amplification coefficient was reduced by 9.96%,the maximum value was increased by 2.74%compared with the determined value,the minimum vertical acceleration amplification coefficient was reduced by 5.85%compared with the determined value,the maximum value was increased by 4.35%compared with the determined value,and the random calculation result of horizontal permanent deformation of the dam top was reduced by 5.46%compared with the deterministic analysis result.The vertical permanent deformation results were reduced by 10.80%,and the maximum reduction was close to 10%,indicating that the spatial variability of materials had a great influence on the dynamic response of asphalt core wall dam-overburden.Compared with the mean of the response stochastic analysis results considering the pore pressure-response coupling of the overburden and the upstream pore pressure-response coupling,the average result of the response stochastic analysis considering only the overburden pore pressure-response coupling has a weakening effect on the acceleration amplification coefficient and permanent deformation of the dam body.The average horizontal acceleration amplification coefficient of dam top decreased by 2.13%,the average vertical acceleration amplification coefficient decreased by 4.26%,the average horizontal permanent deformation of dam top decreased by 3.13%m,and the average vertical permanent deformation decreased by 2.34%m,indicating that considering the pore pressure growth process of the soil upstream of the dam body,it would absorb seismic energy and weaken the dynamic response. |
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