循环温度荷载引起的饱和粉质黏土的超固结效应

The Over-consolidation Effect of Saturated Silty Clay Caused by Cyclic Thermal Loading

对正常固结的饱和粉质黏土试样进行升温-降温过程的室内热固结试验,温度变化过程为25℃→75℃→25℃→75℃….温度循环变化过程中不允许试样排水,而当温度稳定后进行排水固结,进而得到整个温度循环过程中的孔隙水压力消散以及固结体应变变化过程.在初始温度下（25℃）,对另外一些试样施加较大的固结压力完成初始固结,然后再卸荷至较小的固结压力,形成不同超固结比土样（OCR=1,2,3,4）,并进行升温-降温（25℃→75℃→25℃）的热固结试验.基于以上试验,建议了一个循环温度荷载作用下正常固结土和超固结土样的似超固结比的估算方法.研究表明,无论是正常固结土样还是超固结土样,在经过多次温度循环荷载作用后,会呈现为明显的超固结效应.而在相同的循环次数下,温度荷载作用引起的超固结效应随围压的减小而更为明显.

The thermal consolidation characteristics of a normally consolidated saturated silty clay were experimentally studied by heating-cooling cycles,and the investigated temperature range was from 25℃ to 75℃（ i. e.,25℃ →75℃ →25℃ →75℃ …）. During heating or cooling,the specimens were not allowed to drain; while the dissipation of pore pressure and the evolution of consolidation volumetric strain were examined when the temperature reached a required value under drainage conditions. On the other hand,for some other specimens,the primary consolidation was completed under higher confining pressures at an initial temperature of 25℃.Then,the specimens were unloaded to smaller confining pressures to form over-consolidated specimens with various over-consolidation ratio（ OCR = 1,2,3,4） and afterwards experienced a thermal consolidation process of heating-cooling cycle（ i. e.,25℃ →75℃ →25℃）. Based on this,an evaluation method of quasi-over-consolidation ratio was proposed,which shows that both normally consolidated and over-consolidated specimens take on an obvious over-consolidation effect after several heating-cooling cycles. Furthermore,the over-consolidation effect caused by cyclic thermal loading is more obvious with the decrease of confining pressure when the cycle number is same.