Analytical solution for one-dimensional consolidation in layered filled soil based on continuous boundary conditions
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摘要:
新近吹填地基的固结效应十分显著，地基土内超静孔隙水压力的消散将引起地表的整体沉降，对吹填地基上基础工程的稳定性产生不利影响。基于连续排水边界，综合考虑吹填土的自重和下伏原状海床的成层特性，建立了吹填土自重驱动下的吹填地基-原状海床一维固结方程，并基于本征函数法推导了孔隙水压力响应、固结度等的解析解。通过边界条件和模型的退化，验证了解答的正确性。利用该解答讨论了吹填土自重、成层地基模量、时间因数、地表附加荷载等时空条件对吹填地基固结沉降的影响。研究结果表明：①吹填土自重是吹填地基固结的驱动因素，在实际工程中不可忽略；②土体渗透系数对超静孔隙水压力的影响较为复杂，某一层土的渗透性改变后，对其上覆和下伏土层的超静孔隙水压力将产生相反的影响；③土层的体积压缩系数对超静孔隙水压力的影响十分显著，且深部土体的体积压缩系数影响更大；④地表堆载等引起的附加荷载会减缓超静孔隙水压力的消散。
Abstract:The newly filled soil in reclamation areas shows a significant consolidation effect, resulting in severe ground settlements and inducing extremely adverse impacts on the stability of foundations on site. Based on the continuous boundary conditions, this paper establishes a one-dimensional filled soil-native seabed consolidation theory with consideration of the self-weight of the filled soil and the bedding characteristics of the seabed simultaneously, and derives an analytical solutions to the response of the excess pore water pressure and the consolidation degree through the eigenfunction method. The proposed solution is subsequently verified through the degradation of the boundary conditions and mathematical models. By virtue of the proposed solution, a parametric study is conducted to investigate the influence of the spatio-temporal impact factors (including the self-weight of the filled soil, moduli of the filled soil, time factor, and additional load at ground) on the consolidation. The main conclusions can be drawn as follows: ①The self-weight of the filled soil drives the consolidation of the newly filled ground and should not be ignored in practical engineering. ②The effect of the permeability coefficient on the dissipation of the excess pore water pressure is relatively complicated. In case of change in the penetrability of a certain soil layer, it will have opposite influences on the excess pore water pressure of the overlying and underlying soil layers. ③The volume compressibility of the soil has a significant influence on the excess water pressure. And the influence of the volume compressibility of the deeply buried soil is more significant. ④The additional load caused by, for instance, the stacking at the ground, will slow down the consolidation of the site.
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图 1 首个填海造陆机场——大连金州湾国际机场[1]
Figure 1. First sea reclamation airport: Dalian Jinzhou Bay International Airport
图 2 成层陆域吹填地基数学模型
kvi和mvi分别为第i层土的渗透系数和体积压缩系数；H和hi分别表示地基总厚度和第i层土的厚度；zi为第i层地基距离土体表面的厚度；γ′为吹填土的有效重度；σ(x)为x处土体的有效应力分布；x为土体距离土体表面的深度
Figure 2. Mathematical model of layered soil in reclamation area
图 3 连续排水边界退化后超静孔隙水压力和土体沉降曲线
Figure 3. Excess pore water pressure and soil settlement curve after degradation of continuous drainage boundary
图 4 不同吹填土有效重度(γ′)的超静孔隙水压力(a)和土体沉降(b)曲线(α, a, b均为无量纲参数; q为均布荷载；γ′为有效重度；Tv为时间因数；图 5同
Figure 4. Influence of effective weight of filled soil: excess pore water pressure (a) and soil settlement (b)
图 5 不同吹填土厚度(h1)的超静孔隙水压力(a)和土体沉降(b)曲线
Figure 5. Influence of height of filled soil: excess pore water pressure (a) and soil settlement (b)
图 6 不同渗透系数(kvi)时超静孔隙水压力曲线
Figure 6. Influence of permeability on excess pore water pressure
图 7 不同渗透系数(kvi)和时间因数(Tv)时超静孔隙水压力曲线
Figure 7. Influence of permeability and time factor on excess pore water pressure
图 8 不同压缩系数(mvi)时超静孔隙水压力曲线
Figure 8. Influence of compressibility on excess water pressure
图 9 不同时间因数(Tv)时超静孔隙水压力曲线
Figure 9. Influence of surcharge loads on excess pore water pressure
图 10 不同界面参数(α)时平均固结度(Us)曲线
Figure 10. Influence of interface parameters on average degree of consolidation
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