应力历史对饱和软土固结系数的影响

Influence of Stress History on Consolidation Coefficient of Saturated Soft Soil

为了探究不同固结状态下的饱和软土固结系数的变化规律,在太沙基固结理论的基础上,利用渗透系数和孔隙比的关系、孔隙比和固结应力的关系,分别推导出了在正常固结和超固结状态下固结系数(Cv)随固结应力变化的关系式,将关系式代入Terzaghi方程,进而获得考虑应力历史和固结应力影响的修正Terzaghi一维固结方程;通过室内固结试验和工程应用分析对固结系数关系式和修正的Terzaghi一维固结方程的准确性进行验证.结果表明,对于正常固结的软土,当固结应力小于前期固结应力时,固结系数随应力的增大而增大;当固结应力大于前期固结应力时,固结系数随应力的增大而减小.对于超固结状态的软土,固结系数随应力的增大而增大,最后趋于平缓.当上覆荷载较小时,修正前后的Terzaghi一维固结方程计算结果相近;但当上覆荷载较大时,修正后的Terzaghi一维固结方程计算的固结度明显滞后于修正前的计算结果 .前期的应力历史和后期的固结应力对软土固结系数的影响是不容忽视的,修正后的Terzaghi一维固结方程更能真实反映土体的固结性状.

To explore the changing law of the consolidation coefficient of saturated soft soil under different consolidation states,based on Terzaghi’s consolidation theory, using the relationship between permeability coefficient and void ratio, void ratio, and consolidation stress, the relationship between consolidation coefficient(Cv) and consolidation stress under normal consolidation and over consolidation is derived. The modified Terzaghi one-dimensional consolidation equation considering the influence of stress history and consolidation stress is obtained by substituting the relationship into the Terzaghi equation;The accuracy of the consolidation coefficient relation and the modified Terzaghi one-dimensional consolidation equation were verified by laboratory consolidation test and engineering application analysis. When the consolidation stress is larger,the results show that for normally consolidated soft soil when the consolidation stress is less than the previous consolidation stress, the consolidation coefficient increases with the increase of stress. When the consolidation stress is larger than the previous consolidation stress, the consolidation coefficient decreases with the increase of the stress. For over consolidated soft soil, the coefficient of consolidation increases with the increase of stress and finally tends to be gentle. When the load is small, the calculation results of the Terzaghi one-dimensional consolidation equation before and after the modification are similar;but when the load is large, the consolidation degree of the corrected Terzaghi one-dimensional consolidation equation lags significantly behind the calculation result before the modification. The influence of the previous stress history and the later consolidation stress on the consolidation coefficient of soft soil can not be ignored. The modified Terzaghi one-dimensional consolidation equation can more truly reflect the consolidation behavior of soil.