软土的次固结
Secondary consolidation of soft soils
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摘要: 计算软土次固结的常用方法没有反映荷载变化的影响,实际上只适用于正常固结土。而工程中所遇到的大都是超固结土。笔者所做试验表明,当荷载不大时,即处于超固结状态,次压缩明显与荷载有关。本文在Bjerrum等时e-lgp曲线理论的基础上,提出了相对时间坐标系与绝对时间坐标系的概念,建议在次压缩计算中采用绝对时间坐标系,即以正常固结状态的加荷时刻为时间零点的坐标系,从而建立了一种新的次固结计算方法。通过等时e-lgp曲线建立起时间与荷载的关系,使次压缩不仅仅与时间有关,而且也与荷载有关。它可以用于正常固结土和超固结土。这一计算方法可以清楚解释许多试验现象和工程问题,如次压缩随荷载的变化,超载预压后的次压缩,反复荷载对次压缩的影响等。该方法更符合次压缩的变形机理。Abstract: The conventional method to compute secondary consolidation of soft soils does not reflect the influence of load.It is only applicable to the normally consolidated soils actually.However,we often deal with overconsolidated soil in engineering problems.The tests performed by the authors show that secondary compression obviously relates to load on the overconsolidated soil.In this paper,the concept of absolute and relative time coordinate systems is proposed,and it is suggested to use the absolute time coordinate system in computation of secondary compression.In absolute time coordinate system, the beginning of loading on normally consolidated soil is taken as the origin of time.Based on Bjerrum’s theory of equitime e-lgp curve and the absolute time coordinate system,a new method to compute secondary compression is developed.Through the equitime e-lgp curve,the relationship between time and load is set up.Then the secondary compression varies not only with time,but also with load.It can be used for both normally consolidated soil and overconsolidated soil.The proposed model of secondary consolidation can explain many tested phenomenon and engineering problems,such as influences of preloading and repeat of loading and unloading on secondary consolidation.