三种粗粒土强度非线性描述方法的对比研究

Comparison of Three Nonlinear Expressions for Peak Strength of Coarse Grained Soils

为比较三种粗粒土强度非线性描述方法的优缺点及适用性,通过三轴试验研究了初始孔隙比和围压对粗粒土峰值强度的影响,并对三种常用的强度非线性描述方法进行了对比分析。结果表明,粗粒土的峰值强度随着初始孔隙比、围压的增大而减小,表现出显著的非线性;邓肯—张模型中的内摩擦角非线性公式和基于临界状态应力比的峰值应力比公式只能描述围压对峰值强度的影响,扩展后的公式能够同时反映初始孔隙比和围压对峰值强度的影响,且描述效果较好、稳定性较高;基于状态参量的峰值应力比的描述方法,理论清晰,效果较好,但对于粗粒土临界状态的描述还需进一步深入。研究成果可为公式选用提供参考。

The impacts of initial void ratio and confining pressure on the peak strength of rockfill material were studied through triaxial test,and three common used nonlinear expressions of the peak strength were analyzed to compare the advantage and applicability of three methods.The main conclusions are as follows.The peak strength of coarse-grained soil shows significant nonlinearity,which decreases with the increasing initial void ratio and confining pressure.The peak internal frictional angle equation in Duncan-Chang model and the expression of peak stress ratio based the critical stress ratio were two expressions which can only reflect the impact of the confining pressure on the strength.In addition,their parameters were found to be related to the initial void ratio.The mentioned two expressions were,therefore,extended to reflect the impact of the initial void ratio simultaneously.The description of peak stress ratio based on state parameter has its own advantage,and the theory is clear.However,the disadvantage was thought to be that the stability is not so satisfactory,and the critical state of coarse grained soil is needed to be improved.The research results can provide reference for selection of the formulae.