破碎带软岩流变力学试验与参数辨识研究

STUDY OF RHEOLOGICAL TESTS AND ITS PARAMETERS IDENTIFICATION OF SOFT ROCK IN FRACTURED BELT

某大型水电工程处发育有较多的挠曲破碎构造,其岩性为完整性较差的软弱砂岩,并呈现孔隙式胶结接触,长期荷载作用下流变力学特性对坝基变形和稳定存在巨大影响。基于破碎带岩石组织结构疏松、含水率较高、物理力学性能较差等特点,首先开展流变力学试验研究,结果表明,长期荷载作用下岩石表现出显著的流变力学特性,流变曲线主要分为衰减和稳态流变两阶段;流变变形随偏应力增加呈加剧趋势;岩样破坏表现出显著的压缩和延性扩容变形以及稳态流变速率较大等特点。其次,采用三维应力状态下的Burgers流变本构关系对试验曲线进行描述,并结合Quasi-Newton优化算法对流变参数开展辨识和分析,所选模型可准确地对破碎带软岩流变特性进行描述。研究成果对类似工程具有重要参考价值。

Some fractured structures which compose of soft sandstone have been developed in a hydropower project. It has poor integrity and pore cementation contact,and the creep properties producing a significant impact on the deformation and stability of the dam under long term load. Based on the characteristics of loose organizational structure,high moisture content,poor physico-mechanical properties,the triaxial creep tests were carried out first. The results show that the soft rock has a significant creep property,and the creep curve is mainly divided into transient and steady creep. Increasing stress can aggravate the creep deformation,and the finally failure of the specimen shows the characteristics of large axial compression deformation,obvious volumetric ductility dilation and large steady creep rate. Secondly,the creep curves are described by taking three dimensional Burgers creep model. The parameters are identified with combination of Quasi-Newton optimized algorithms method. The selected model can describe the creep properties of soft rock correctly. The research results have important reference value for similar projects.