粉煤灰与动载耦合作用下黄土震陷试验研究

Experimental study of loess seismic subsidence under the coupling effect of fly ash and dynamic loading

为了探讨粉煤灰与动载耦合作用下黄土的震陷问题,找出粉煤灰改良黄土的最佳配比,通过动三轴震陷试验,定性分析了黄土在不同粉煤灰掺量下的震陷特性。研究了粉煤灰掺量对黄土震陷性的定量影响规律,建立了黄土的震陷曲线方程,得到了粉煤灰掺量与残余应变的定量关系。研究结果表明:(1)粉煤灰掺量增加、动载作用均会引起黄土震陷性发生改变,即随着粉煤灰掺量的增大,土的残余应变逐渐减小,动应力幅值逐渐增大;(2)当动应力幅值相同时,残余应变随动载振次的增多而增大,其增长速率随动载振次的增多而减小,粉煤灰掺量越大,残余应变随动载振次的增长越缓慢;(3)在不同动载振次下,黄土的震陷临界动应力曲线随粉煤灰掺量的增加均经历了一个从平稳、快速、再收敛至最大震陷临界动应力的发展过程;(4)震陷试验得到的最佳粉煤灰掺量为20%。

In order to discuss seismic subsidence problem of loess under coupling effect of fly ash and dynamic loading,and determine the best ratio of fly ash improved loess,seismic subsidence behavior of loess with different fly ash amount are quantitative analyzed based on dynamic triaxial tests.Furthermore,quantitative influence of fly ash amount on seismic subsidence behavior of loess are studied,seismic subsidence curve equation of loess is established,and quantitative relationship between fly ash amount and dynamic residual deformation is proposed.The results show that：（1） the increase of fly ash amount and dynamic loading can change seismic subsidence behavior of loess,in other word,with the increase of fly ash amount,the dynamic residual deformation is reduced gradually,and the dynamic amplitude is mounting.（2） When the dynamic amplitude being equal,dynamic residual strain increase with the number of cyclic loads increase,whereas the growth rate of it is decreased.The more the fly ash amounts,the slower the growth of dynamic residual deformation with increase of cyclic number.（3） Under different cyclic numbers,the critical dynamic stress of the loess seismic subsidence,with the increase of fly ash amount,goes through a process which contain smooth development,sharply increase and converging to the maximum critical dynamic stress of loess seismic subsidence;（4） The best ratio of fly ash amount is 20%.