Study On Dynamic Strength Characteristics Of Filter Material Of High Earth-rock Dam

In order to protect the core material of earth-rock dam, usually set filter layer at upstream and downstream of the core wall. The role of the filter layer is filtered the soil and drainaged, to prevent hydraulic structures from suffered the canal gush, soil flow and other seepage damage. If the core wall cracks during the earthquake, the fine particle of the filter material can fill and repair the cracks under the action of penetration. To overcome the arching effect on the core wall, the density of filter material can be kept slightly loose. But the looser filter material will liquefy under earthquake, this will lead to break away between shell and core wall, thus undermine the integrity of the dam. Therefore it is of great importance to make sure that it works properly by studying the dynamic strength property and accurately determining whether the liquefaction occurs.In this paper, K0consolidation tests, K0CD triaxial test, isotropically CD triaxial test and dynamic tests are performed by filter material of Nuo Zhadu Dam with British GDS dynamic and static triaxial tester. Static and dynamic characteristics of the filter material has been conducted in-depth research, which includes:(1) The variation law of strain-stress relationship and coefficient of earth pressure at rest is obtained from the Ko consolidation tests. During loading stage, the relationship between the average principal stress and the volumetric strain as well as the relationship between generalized shear stress and generalized shear strain agree with power function.(2) Through Ko CD triaxial test and isotropically CD triaxial test, it can be found that the shear stress-strain curve shows a strain-softening phenomenon and the volumetric strain curve shows obvious dilatation characteristics. The drained shear strength of them is at the same level and the stress history has little effect on the softening stage of the filter material. The initial elastic modulus Ei and bulk modulus obtained from the K0CD triaxial tests are greater than those obtained from the isotropically CD triaxial tests under the same stress condition.(3) Carried out the modulus and damping tests of saturated filter material, fitting the experiment data and obtained the parameters.(4) Through the dynamic triaxial tests, the effect of initial stress condition and various failure criteria on the dynamic strength is studied. The research shows that:①under a certain failure criterion, the initial stress condition of soil has a significant effect on dynamic strength; under the same consolidation ratio, as the confining stress increases, the dynamic strength increases; under the same confining stress, as the consolidation increases, the dynamic strength increases.②the failure criterion affects the dynamic strength greatly. And under the same consolidation ratio, the dynamic strength under liquefaction criterion and strain failure criterion is greater than that under criterion of limit equilibrium.③the shear strength of total earthquake stress under criterion of limit equilibrium is less than that under liquefaction criterion and strain failure criterion. And as the consolidation increases, the shear strength increases.(5) According to the results of four kinds of permanent deformation model to fit the permanent deformation data of filter material, getting parameters and the results were analyzed and compared.