| Earth-rock dam is one of the major development dam types at home and abroad, which has many advantages such as less investment, short construction period and wide adaptability to geological conditions. In recent years, the height of earth-rock dam has a significant progress, realizing to transform the stage of high dam from150m level to300m level. Such as Shuangjiangkou (312m), Lianghekou (293m), Nuozhadu (261.5m) etc.Gravel soil is usually used as seepage proof material for the core wall of high earth-rock dam. This manual gravel admixture has wide gradation and considerable clay content. It owns a high dry density because the pore of large particles is filled sufficiently with small particles, and has a good property of seepage proof. Besides, it has high shear strength and elastic modulus as the skeleton is formed by coarse particles. If gravel soil is used as core wall material in high earth-rock dam, it not only plays an anti-seepage role but also bears the load preferably, improves the stress condition and reduces the likelihood of hydraulic fracture as the strength-deformation between gravel soil and both sides of the dam shell materials is small.The deformation of high earth-rock dam shell materials has a development trend towards out, which can decrease the stress of core wall. In the event of an earthquake, it is likely to cause the problem of insufficient dynamic strength, cracks, even lead to instability of the dam slope when the earthquake is stronger. Gravel soil core wall can improve its seismic dynamic strength. It can bear more shear stress caused by earthquake than clay core wall because the stiffness of core wall with gravel soil and dam shell has a few small differences. Therefore further studies would be needed to find if the dynamic strength of gravel soil core wall can meet requirement. In this paper a series of saturated static and dynamic tests under low confining pressure are conducted through the GDS triaxial apparatus, the dynamic strength characteristics of gravel soil core wall at the top of dam body are studied. The main works is as follows:(1) By the consolidated undrained static tests, the curves of stress-strain, pore pressure, effective stress path are plotted, and the indexes of static constitutive model are calculated.(2) Based on the triaxial test of dynamic characteristics, the fitting curves for dynamic modulus and damping ratio are plotted, and its corresponding parameters are obtained. (3) The dynamic strength tests are performed and the results show that:â‘ The dynamic strength of sample under the same confining pressure generally increases firstly then reduces with the consolidation ratio increasing.â‘¡The dynamic strength increases with the gravel proportion increasing, and this trend is more significantly with the increase of confining pressure. Dynamic friction angle increases but dynamic cohesive decreases with gravel proportion increasing. That gravel proportion changes the dynamic indexes is similar to the static conditions.â‘¢The curves of dynamic strain versus vibration times is related to the ratio of dynamic stress versus consolidation undrained strength. The curves of dynamic strain versus vibration times have a turning point. The curves of dynamic strain versus vibration times change slowly before reaching the turning point, but dynamic strain grows sharply after it.â‘£Through three groups of different consolidation ratio of dynamic strength tests, the total seismic stress shear strength curves are drawn and its total stress parameters are obtained. |
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