陈余, 李传勋. 连续排水边界下考虑起始坡降的软黏土固结解[J]. 工程力学, 2021, 38(9): 161-170. DOI: 10.6052/j.issn.1000-4750.2020.09.0656
引用本文: 陈余, 李传勋. 连续排水边界下考虑起始坡降的软黏土固结解[J]. 工程力学, 2021, 38(9): 161-170. DOI: 10.6052/j.issn.1000-4750.2020.09.0656
CHEN Yu, LI Chuan-xun. CONSOLIDATION ANALYSIS OF SOFT CLAY CONSIDERING THE THRESHOLD HYDRAULIC GRADIENT AND A CONTINUOUS DRAINAGE BOUNDARY[J]. Engineering Mechanics, 2021, 38(9): 161-170. DOI: 10.6052/j.issn.1000-4750.2020.09.0656
Citation: CHEN Yu, LI Chuan-xun. CONSOLIDATION ANALYSIS OF SOFT CLAY CONSIDERING THE THRESHOLD HYDRAULIC GRADIENT AND A CONTINUOUS DRAINAGE BOUNDARY[J]. Engineering Mechanics, 2021, 38(9): 161-170. DOI: 10.6052/j.issn.1000-4750.2020.09.0656

连续排水边界下考虑起始坡降的软黏土固结解

CONSOLIDATION ANALYSIS OF SOFT CLAY CONSIDERING THE THRESHOLD HYDRAULIC GRADIENT AND A CONTINUOUS DRAINAGE BOUNDARY

  • 摘要: Terzaghi一维固结理论中边界条件和初始条件相矛盾的逻辑问题以及软黏土中水的渗流在低水力坡降下可忽略均已逐渐被认识。但在连续排水边界条件下能考虑起始水力坡降的黏性土一维固结理论,尤其是固结模型的解析解还鲜见报道。基于此,该文引入了连续排水边界,并同时考虑黏性土中渗流存在的起始水力坡降,建立了均质地基的单面排水一维固结模型。采用有限傅里叶变换方法求解了所建立固结模型的孔压、固结度以及沉降解析解答,分析了土层在恒载下同时考虑连续排水边界和起始水力坡降的一维固结性状。结果表明:考虑起始水力坡降后,连续排水界面参数b对固结性状的影响与达西定律下相同,即b值越大,排水面透水情况越好,孔压消散速率越快,固结完成时间越短;相反b值越小,排水面透水情况越差,孔压消散越慢,固结完成时间越长。连续排水条件下无量纲R(起始水力坡降、水的重度与土层厚度的乘积除以外荷载)对固结性状影响与完全透水边界下相比无明显改变。R值越大,渗流前锋到达土层底部的时间越长,固结完成时土中超静孔压残留值越大,土层按孔压定义的平均固结度越小,最终沉降量也越小。

     

    Abstract: The logical problem in Terzaghi's one-dimensional consolidation theory between boundary conditions and initial conditions and the phenomenon that the velocity of water in soft clay can be negligible under low hydraulic gradient have been gradually recognized. However, under a continuous drainage boundary condition, the one-dimensional consolidation theory considering both the continuous drainage boundary condition and the threshold hydraulic gradient, especially the analytical solution for this model of consolidation, is rarely reported in the literature. It introduces a continuous drainage boundary and develops a single-sided drainage consolidation model of homogeneous soil layers considering the threshold hydraulic gradient in clay soil. The finite Fourier transform method was adopted to obtain solutions for excessive pore pressure, average degree of consolidation and settlement. Furthermore, the influence of continuous drainage boundary condition and initial hydraulic gradient on the consolidation behavior is analyzed when a constant load is applied to a soil layer. The results show that the effect of the continuous drainage interface parameter b on the consolidation behavior of soil with initial hydraulic gradient is the same as that with Darcy's law. The larger the b, the better the permeability of the drainage surface, and the faster the dissipation rate of the pore pressure, and the shorter the consolidation time. On the contrary, the smaller the b, the worse the permeability of the drainage surface, the less the dissipation rate of the excess pore pressure, and the longer the consolidation completion time. When the continuous drainage condition is considered, the influences of the dimensionless variable R (the product of initial hydraulic gradient, specific weight of water and the thickness of the soil layer divided by external load) on the consolidation behavior considering the continuous drainage boundary are not significantly different from that with a fully permeable boundary. The larger the R, the longer the time for the seepage front to reach the bottom of the soil layer. The larger the R, the greater the residual value of the excess pore water pressure in the soil layer when the consolidation is completed. The larger the R, the smaller the average consolidation degree defined by the pore pressure, and the smaller the final settlement.

     

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