主应力轴循环旋转下原状软黏土临界性状研究

Critical properties of intact soft clay under cyclic principal stress rotation

针对在交通、波浪等动荷载下土体所受应力状态具有主应力轴循环旋转的特征,对杭州地区典型原状软黏土开展不排水模拟试验.主应力轴双幅循环旋转的试验结果表明,试样扭剪、轴向应变发展受主应力轴旋转角度的影响,当转角大于一定值时,破坏应变以扭剪应变占主导,反之则要考虑扭剪和轴向等应变的共同影响.在同一旋转频率下,随着剪应力提高,试样破坏应变同步提高,且与破坏振次对数值成线性关系;若剪应力幅值不变,随旋转频率提高,临界破坏应变同步减少,破坏振次大幅提升,两者在对数曲线上亦可用线性关系表示.与等剪应力幅值的主应力轴双幅循环旋转试验结果相比,当单幅循环旋转破坏时扭剪应变很大,且受频率或剪应力幅值影响小,同时最小破坏剪应力也有显著提高.

A series of undrained tests on typical Hangzhou intact soft clay were conducted to investigate the influence of cyclic principal stress rotation induced by traffic or wave loads on soil＇s properties. Test resuits of two-amplitude cyclic principal stress rotation show that the induced torsional shear strain and axial strain are greatly influenced by the angle of principal stress rotation. If the angle is larger than a certain value, the torsional shear strain is dominating; if smaller than that value, the torsional shear strain and axial strain are at the same magnitude and should be considered together. At the same frequency, the critical failure strain increases with the shear stress level, and has a linear relationship with the logarithmic cycles. At the same shear stress level, the critical strain decreases with increasing frequency, while the critical rotation cycles increase greatly. The logarithmic strain and logarithmic cycles have linear relationship. Compared with the results of two-amplitude cyclic principal stress rotation tests at the same shear stress level, the critical torsional shear strain in one-amplitude cyclic rotation tests is much larger and influenced neither by frequency nor shear stress level, moreover the minimum failure shear stress level.