主应力比对超固结软黏土平面蠕变的影响研究

THE EFFECT OF PRINCIPAL STRESS RATIO ON CREEP BEHAVIOUR OF OVER-CONSOLIDATED CLAY UNDER PLANE STRAIN CONDITIONS

通过对原状软土进行平面变形蠕变实验,研究平面变形条件下主应力比对超固结软土蠕变特征的影响。研究表明,平面变形条件下,以广义剪应力定义超固结剪应力比OCR_q,包含了前期固结应力数量和主应力比特征,能全面地反映软土的超固结特性,相对于超固结球应力比OCR__p能更直接反映超固结软土平面蠕变变形的特征;平面变形超固结软土的蠕变系数与超固结剪应力比OCR_q具有一一对应的关系,OCR_q越大对应的蠕变系数越小。OCR_q相同时前期固结过程主应力比小的土体具有较大的蠕变系数。在不同主应力比下构成的超固结应力历史,使得平面变形超固结软土相对于正常固结状态具有较小的广义剪应力,一定条件下主应力比越小广义剪应力越大,对应的超固结状态下土体具有较大的长期蠕变变形。

The effect of principal stress ratio on creep behaviour of over-consolidated soil was studied through tests on undisturbed soft clay samples under plane strain conditions. The over-consolidation shear stress ratio (OCRq), defined with the generalized shear stress, was found to be a function of the principal stress ratio and the pre-consolidation pressure. OCRqcan provide a better and more direct description of the creep behaviour of over-consolidated soft clay under plane strain conditions compared with the over-consolidation spherical stress ratio(OCRp). There is a one-to-one relationship between the creep coefficient and the OCRq: as the OCRqincreases, the corresponding creep coefficient decreases. For the same OCRq, over-consolidated soils with smaller principal stress ratios will have larger creep coefficients. For different principal stress ratios, the over-consolidated soft clays will have smaller generalized shear stress than normally consolidated ones. Under certain conditions, the generalized shear stress increases with decreasing principal stress ratio and the corresponding over-consolidated soil will have greater long-term creep deformation. © 2015, Science Press. All right reserved.