红石岩堰塞坝新堆积体动三轴试验研究

Dynamic triaxial experimental study on new deposit body of Hongshiyan barrier dam

牛栏江上的红石岩堰塞坝新堆积体以石灰岩和白云岩为主,级配和密度离散性较大。同时,已有研究结果表明,红石岩新堆积体具有黏性粗粒土性质,静力参数具有明显的离散性,需开展其岩土料的动力参数研究,以为将其利用改建为水利枢纽提供基础材料数据。采用GDS动三轴仪,对红石岩新堆积体进行了动剪切模量比与阻尼比试验,研究新堆积体动应力应变特性及其影响因素。试验结果表明:随着剪应变的不断增大,新堆积体动剪切模量比不断减小,阻尼比随之增大。新堆积体动力特性受围压影响较为明显,最大动剪切模量随着围压的增大而增大。在相同剪应变条件下,随着围压、干密度、粗颗粒含量的增大,动剪切模量比逐渐增大,阻尼比逐渐减小。另一方面,新堆积体细粒含量较多,颗粒岩性复杂,风化程度差异明显,导致其动力特性具有一定的离散性,与人工筑坝堆石料存在明显差异。

The new deposit body of Hongshiyan barrier dam is mainly composed of limestone and dolomite,and the gradation and density are very discrete.Meanwhile,results show that the new deposit body has the properties of viscous coarse-grained soil,and the static parameters show obvious dispersion,so it is necessary to study its dynamic properties to provide material data for transforming the barrier dam to a hydraulic project.In this paper,the dynamic shear modulus and damping ratio tests of the new accumulation were carried out by using the GDS dynamic triaxial instrument to study the dynamic stress-strain characteristics and its influencing factors.The test results showed that the dynamic shear modulus of the new deposit body decreased and the damping ratio increased with the increasing of shear strain.The dynamic characteristics of the new deposit were obviously affected by the confining pressure.The maximum dynamic shear modulus increased with the augment of confining pressure.Under the same shear strain,with the increase of the confining pressure,the dry density,the coarse particle content respectively,the dynamic shear modulus ratio all increased and the damping ratio all decreased.However,the new deposit body had more fine grain content,complex grain lithology and showed obvious difference in weathering degree,so it led to discrete dynamic characteristics that is obviously different from the artificial dam rockfill material.