| Levee seepage control is the key technique of water-retaining structure which built on permeable foundation.The quality of seepage control is related to the safety of the project.Nowadays,the seepage control technique of cutoff wall combine with foundation curtain grouting is applicated in deep overburden karst foundation.This seepage control technique integrated the advantages of cutoff wall and curtain grouting,it can solve the problem of unfavorable geology.However,the cutoff wall is located in dam body or deep overburden foundation,its stress condition is extremely complex.In addition,cutoff wall is a kind of concealed work,reasonable evaluation of cutoff wall performance is important for dam stable operation.Since the cutoff wall is widely used in water conservancy construction,it is necessary to system analysis the permeability characteristics and load-bearing behavior of the cutoff wall which built on deep overburden karst foundation.With the reasonable selection of soil constitutive model and interface element between cutoff wall and soil,and based on seepage-stress coupling theory,using Tonggan levee engineering of Xiajiang water control project as an example,the nonlinear mathematic model of seepage field and stress field coupling analysis in porous medium materials is built by using ABAQUS and its secondary development function in this paper.Besides,Studying the stress-strain and permeability characteristics of cutoff wall built on deep overburden karst foundation.The main research contents are as follows:(1)The control mechanism of seepage deformation of levee foundation has been given a fair summary.It is pointed out that the joint cutoff wall and curtain grouting impervious is the main measure to solve the problem of seepage in deep and complex overburden karst foundation.(2)The hydro-mechanical coupling action mechanism and coupled equations are researched based on the study of mathematical analysis model and governing differential equations of seepage and stress.In addition,the subprogram of Duncan-Chang E-B constitutive model and Goodman Contact element is developedby using the secondary development function of ABAQUS.(3)Using Tonggan levee engineering of Xiajiang water control project as an example,built the three-dimensional finite element model depending on hydro-mechanical coupling action.On this basis,the interaction between cutoff wall and overburden layer under karst cave grouting,cutoff wall construction,levee filling and retaining water process is simulated,especially the effect of karst cave grouting on the engineering.The results show that the cutoff wall is subjected the typical bending moment,and the karst cave will cause stress concentration.After grouting,the pressure of the wall is reduced effectively,and the wall bears a large stress.(4)The sensitivity analysis of cutoff wall elasticity modulus,cutoff wall permeability coefficient and overburden mechanical parameter influence on cutoff wall stress and deformation are implemented.The results show that the water load is the main cause of the wall deformation,the horizontal displacement is mainly determined by the support condition behind the wall and the plastic cutoff wall can maintain a good stress state. |
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