考虑土石混合体“颗粒破碎-剪切参数-含水率”相关性的力学特性研究

Study on mechanical properties of soil-rock mixture considering thecorrelation of “particle breakage-shear parameters-water content”

抽水蓄能电站建设产生大量土石混合料堆积形成弃渣坝,渣体结构松散、级配差、重度大、透水性强,若遇强降雨,将严重影响其安全稳定性。现以弃渣坝土石混合体为研究对象,探究其在不同应力状态下应力-应变发展规律、变形强度特性,以及剪切前后颗粒级配定量研究。试验结果表明:随着含水率增加,混合体试样的抗剪强度降低,应力-应变曲线整体呈现硬化趋势,含水率的增加降低了非线性内摩擦角,黏聚力呈现先减小后增大的趋势;随着试样含水率增大,表征其变形特性的相变应力比减小,体变量减小,剪胀特性影响减弱,随着围压增大,结果与上述一致。通过对混合体剪切前后颗粒级配测定,引入颗粒破碎指标探究土石混合体颗粒破碎-剪切参数-含水率相关性分析,结果表明,当含水率增加且颗粒破碎增大时,抗剪强度减小幅度变大,对坝体的安全影响更为明显;当含水率和破碎程度减小时,结果反之。最后,通过引入破碎参数进行了邓肯-张模型修正,并基于试验结果论证了模型的适用性,以期为后续弃渣坝结构安全稳定提供借鉴。

The construction of pumped storage power station produces a large amount of earth-rock mixture to form a waste dam,which has loose structure,poor grading,heavy weight and strong water permeability.If it encounters heavy rainfall,its safety and stability will be seriously affected.Taking the soil-rock mixture of waste dam as the research object,the development law of stress and strain,the characteristics of deformation strength and the quantitative study of particle gradation before and after shearing are explored.The test results show that with the increase of water content,the shear strength of the mixture sample decreases,the stress-strain curve shows a hardening trend as a whole,the nonlinear internal friction angle decreases with the increase of water content,and the cohesion first decreases and then increases.With the increase of water content,the phase change stress ratio,the volume variable and the dilatancy effect decrease.With the increase of confining pressure,the results are consistent with the above.By measuring the particle gradation of the mixture before and after shearing,the correlation analysis of particle breakage-shearing parameters-water content of the soil-rock mixture is explored by introducing the breakage index.The results show that when the water content increases and the particle breakage increases,the shear strength decreases greatly,which has a more obvious impact on the safety of the dam.When the water content and breakage degree decrease,the result is the opposite.Finally,the Duncan-Chang model is modified by introducing breakage parameters,and the applicability of the model is demonstrated based on the test results,so as to provide reference for the safety and stability of the follow-up waste dam structure.