Research On Reinforcement Measures Of Earth-rock Dam Foundation On Deep Overburden

The southwest region of China is rich in hydropower resources.Scientific and reasonable development of hydropower resources will promote the growth of national economy,regional unity and stability,energy structure adjustment and environmental protection.However,the complex geological structure,deep and uneven riverbed overburden,many active faults and frequent and strong earthquakes in southwest China have brought many problems to water conservancy construction.With the continuous development of my country’s hydropower industry,the construction and analysis methods of earth-rock dams have made great progress,but the construction of earth-rock dams on deep overburdens is still in is still in its infancy.The safety of earth-rockfill dam on deep overburden is seriously affected by the large difference in properties of overburden,complex deformation characteristics,obvious dynamic nonlinearity and wide distribution of liquefiable soil layer.The foundation treatment is the primary problem to be solved when constructing earthrock dam on deep overburden.Vibroflotation gravel pile is a commonly used foundation reinforcement measure at present,but the existing engineering practice and research are mostly focused on low-rise structures such as embankment and stockpile yard,and few on large hydraulic structures such as earth-rock dam.In view of this,based on the improved generalized plastic constitutive model of coarse-grained soil,combined with effective stress theory and dynamic consolidation theory,the numerical simulation of reinforcement measures of earthrock dam foundation on deep overburden is carried out in this paper.(1)Firstly,several simplified numerical calculation models often used in the treatment of poor foundation by gravel piles are introduced,and the characteristics and application of each model are summarized,and the generalized plastic constitutive model of coarse grained soil is briefly introduced.(2)The sensitivity analysis of the simplified model is used to determine the appropriate pile-soil element grid,and the finite element analysis of the earth-rock dam built on the soft foundation with deep overburden layer and the earth-rock dam built after the foundation reinforced with gravel piles is carried out by using the grid.The finite element results of earthrock dam reinforced foundation are compared with the monitoring results of similar projects to verify the results presented in this paper.(3)Study on the treatment effect of gravel piles in the foundation of face rockfill dam which can liquefy deep overburden layer.The deformation of dam-foundation system on natural foundation and gravel pile reinforced foundation during construction and operation of the dam is analyzed.The dynamic response,the liquefaction of sand and the permanent deformation of the dam-foundation system after the earthquake are analyzed.The reinforcement effect of vibroflotation gravel pile for the construction of earth-rock dam on the liquefiable deep overburden foundation is discussed.