变荷载下考虑起始比降与连续排水边界的固结解
CSTR:
作者:
作者单位:

1.江苏省地矿局第三地质大队;2.江苏大学 土木工程与力学学院

中图分类号:

TU433


Analytical Solution of Consolidation considering Initial Hydraulic Gradient and Continuous Drainage Boundary under Variable Load
Author:
Affiliation:

1.The Third Geology Group of Jiangsu Geology Mineral Exploration Bureau;2.Faculty of Civil Eng. and Mechanics, Jiangsu Univ.

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    摘要:

    采用连续排水边界的必要性以及软黏土中水的渗流存在着起始水力坡降(i0)的试验现象已逐渐被认识,但变荷载下同时考虑连续排水边界条件和起始水力坡降的一维固结解析解还鲜见报道。基于此,本文针对外荷载随时间逐渐增加的实际,建立了变荷载下同时考虑连续排水边界和起始水力坡降的固结模型。采用傅里叶变换及拉普拉斯变换获得模型的近似解析解,利用该解答分析了动边界移动规律、超静孔隙水压力随时间消散规律以及平均固结度的增长规律。结果表明,在加载速率不变下,起始水力坡降下排水面透水情况对固结性状的影响与其在达西定律下相同,透水情况越好,孔压消散速率越快;透水情况越差,超静孔隙水压力消散速度越慢。连续排水条件下起始水力坡降i0对固结性状影响与完全透水边界下相比无明显改变,i0越大,移动边界到达土层底部的时间越长,固结完成时土中残留的超静孔压越大,按孔压定义的平均固结度越小;i0值越小,移动边界到达土层底部的时间越短,固结完成时土中残留的超静孔压越小,按孔压定义的平均固结度越大。在起始水力坡降和边界排水条件不变的情况下,随着加载时间的增大,超静孔隙水压力峰值越小,超静孔隙水压力达到峰值的时间越长,但加载时间对超静孔压残留值及按孔压定义的最终平均固结度无影响。

    Abstract:

    It has been gradually recognized of the existing of initial hydraulic gradient(i0)during water seepage in soft clay and the necessity of considering continuous drainage boundary is being accepted more and more. However, the analytical solution of one-dimensional consolidation under variable load, considering both continuous drainage boundary condition and initial hydraulic gradient has rarely been reported. Based on this, taking variable load into account, a consolidation model considering both continuous drainage boundary and initial hydraulic gradient is established. The approximate analytical solution of the one-dimensional consolidation model is obtained by using Fourier transform and Laplace transform, from which, the moving law of dynamic boundary, dissipation law of excess pore water pressure as well as the growth characteristics of average consolidation degree are analyzed. The results show that, with the same loading rate, the influence of permeability of drainage surface under initial hydraulic gradient on consolidation behavior is just the same with that according to Darcy"s law. The better the permeability is, the faster the dissipation rate of pore water pressure comes, and conversely, the worse the permeability is, the slower the dissipation rate of excess pore water pressure becomes. The effect of initial hydraulic gradient on consolidation behavior under continuous drainage boundary presents consistent with that under fully permeable boundary, of which the fact is, a larger value of i0 may lead to larger residual excess pore pressure, smaller average degree of consolidation defined by pore pressure, and longer time for the moving boundary reaching to the bottom of soil layer. On the other side, the smaller value of i0 is, the shorter time it takes for the moving boundary reaching to the bottom of soil layer, the smaller the residual excess pore pressure becomes, and the larger the average degree of consolidation defined by pore pressure is. When under the same initial hydraulic gradient case and boundary drainage conditions, the peak value of excess pore water pressure decreases with the growth of loading time, and correspondingly takes longer time for the excess pore water pressure reaching to the peak value. However, the loading time has no influence on the residual value of excess pore water pressure and the final average cohesion defined by pore pressure.

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  • 收稿日期:2021-01-05
  • 最后修改日期:2021-03-27
  • 录用日期:2021-04-27
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