Study On Constitutive Relationship Of Rockfill Under Simulating Actual Stress Path Of Dam

Rockfill, as a kind of coarse grained soil, is applied widely in high earth-rock dam, roadded of railway and highway, soft foundation of constructions and retaining wall of seaport and so on. Especially in earth-rock dam, as main filling material, its mechnical character plays a critical role in maintaining normal operation and safety of dam. Rockfill has correlation of stress path, but most constitutive models of rockfill do not consider the influence of stress path factor. Duncun-Chang model is based on normal triaxial test under the stress path of confining pressure keeping constant, and the path is different from the actual stress path of dam. The stress and deformation calculated by Duncun-Chang model have some differences with measured datas, and already can not meet the design requirements of high earth-rock dam. Aim at the above-mentioned problems, the paper develops the study on the constitutive relationship of rockfill under the simulating actual stress path of dam. The main work is as follows:(1) The stress paths of some different representative points inside Nuozhadu core-wall rockfill dam are studied by FEM numerical calculation. The results show that all points in different position of the dam have stress path of constant stress ratio in construction stage, and during the impounding period the path turns to different direction and becomes complex. Analysis is also done about the change law and influencing factors of the stress path slope.(2) Triaxial concreting drainage tests of rockfill are introduced, which are done under both loading paths of constant stress ratio to simulate the constrution stage and complex paths to simulate the impounding stage. Stress-strain relationship curves are collated according to test datas. Strength and deformations properties of rockfill under all the test paths are analyzed in detail.(3) Based on the test results under the simulating actual stress path of dam, a new simple constitutive model of rockfill is introduced, which is convenient for finite element calculation, and in which the influence of stress path is taken into full consideration. The simulating results with test curves show that the new model can well describe the behavior of rockfill under the two kinds of test stress paths.(4) According to simplify the dam metarial partion and program composition of the new model, Nuozhadu dam is calculated with two schemes. The results compared with E-B model show that stress distribution and arch effect of core-wall do not change significantly, but horizontal displacements and settlements with new model decrease with different degrees, which are more close to the change law of observation datas. The new model has higher accuracy than E-B model and can well predict the deformation characteristics of rockfill under the stress path of dam.