双向循环荷载作用下饱和红土的动变形强度特性

Dynamic strength and deformation behaviors of saturated laterite under bidirectional cyclic loads

【目的】探究双向循环荷载耦合作用下饱和红土的动变形强度特性,为红土地区工程的抗震设计和性质评估提供理论支持。【方法】采用SDT-20型电脑控制电液伺服双向土动三轴试验机,对饱和红土试样施加了不同的应力路径,模拟横波和纵波在不同相位差下耦合的情况,分析不同应力路径下饱和红土的动变形和动强度特性。【结果】径向循环应力幅值和相位差的变化对饱和红土的动变形和动强度有较大影响。在相位差为180°时,轴向应变发展速度最快,动强度最小;当相位差为0°时,轴向动应变发展最慢,动强度最大。径向循环应力较大且相位差为180°时的耦合情况对土体的稳定最为不利,此种组合下饱和红土的动强度衰减率可以达到90%以上。【结论】随着径向循环应力幅值的变化,不同应力路径下动应变发展速度不同,应力路径斜率越大动应变发展越缓慢。在实际工程的抗震设计时,应充分考虑双向动荷载相位差为180°且径向动荷载较大的组合情况。

[Objective] This study investigated the dynamic strength and deformation characteristics of saturated laterite under bidirectional cyclic loads to provide theoretical support for seismic design and engi- neering properties evaluation in laterite area. [Method] Computer-controlled （SDT-20） electro-hydraulic servo dynamic triaxial tester was used to exert different stress paths on saturated laterite samples to imitate coupled shear wave and tensile-compressive wave under different phase differences. Then, the dynamic de- formation and dynamic strength of saturated laterite under different stress paths were analyzed. [Result] The variation of radial cyclic stress amplitude and phase difference had great influence on dynamic deforma- tion and dynamic strength of saturated laterite. When the phase difference was 180~,the development speed of axial dynamic strain reached the peak while the dynamic strength was the lowest. When the phase differ- ence was 0°, the dynamic strain and the development speed was the slowest while dynamic strength was the largest. When radial cyclic stress coupled with phase difference of 180~,the soil stability would be in dangerand the attenuation rate of dynamic strength of saturated laterite would be 90%. [Conclusion] The pace of development of dynamic strain under different stress paths varied with the radial cyclic stress amplitude, and the dynamic strain developed slower as the slope of stress path increased. Fully consideration is needed for the load combination when the phase difference of bidirectional dynamic loads is 180° and radical dy- namic load is large in seismic design of practical engineering.