高填方粗粒土干湿循环及蠕变特性三轴试验研究

Triaxial Tests on Dry-wet Cycle and Creep Behavior of High-fill Coarse-grained Soil

白鹤滩水电站库区蓄水后,其高填方场地将长期经历水位升降,对于场地的变形和稳定来说十分不利。依托于白鹤滩水电站库区移民安置区消落带高填方场地稳定性研究项目,通过大型常规三轴剪切试验和蠕变试验分析了粗粒土在干湿循环作用和饱水条件下的应力应变关系、剪切形态特征、长期强度、变形规律等,得到主要结论如下:①粗粒土的强度随着干湿循环次数的增加逐渐降低;②干湿循环次数n≤3时,粗粒土试样先剪缩后剪胀,n>3时,粗粒土只有剪缩变形;③粗粒土的峰值偏应力随着干湿循环次数的增加逐渐降低,围压越高干湿循环作用对粗粒土抗剪强度损伤劣化的影响越大;④粗粒土的长期强度较剪切破坏强度有所降低,在低围压下降幅较小,一般情况下可达到剪切破坏强度的80%甚至更高,在高围压下由于颗粒破碎严重粗粒土的长期强度损伤较大。

After the Baihetan Dam reservoir area is impounded,the high fill site will experience the rise and fall of water level for a long time,which is very disadvantageous to the deformation and stability of the site.This paper focuses on the stability of high-fill sites.It is part of the Baihetan Dam project in the water-level-fluctuating zone of the resettlement area in the reservoir area.The research examines the effects of wet-dry cycles and saturation on coarse-grained soil.Methods include large-scale triaxial shear and creep tests.The investigation assesses stress-strain relationships and shear morphology.It also evaluates the long-term strength and deformation laws.Key conclusions are presented as follows:①The strength of coarse-grained soil gradually decreases with an increase in the number of dry-wet cycles.②When the number of dry-wet cycles n≤3,coarse-grained soil samples first shrink and then dilate;when n>3,coarse-grained soil only undergoes shear deformation.③The peak deviating stress of coarse-grained soil decreases gradually with the increase in the number of dry-wet cycles,and the higher the confining pressure,the greater the effect of dry-wet cycles on the damage and deterioration of the shear strength of coarse-grained soil.④The long-term strength of coarse�grained soil is lower than that of shear failure strength.The drop range of low confining pressure is smaller,generally reaching 80%or even higher of shear failure strength under normal circumstances;under high confining pressure,the long-term strength damage of coarse-grained soil is greater because of particle breakage.