﻿ 基于考虑时间效应UH模型的一维固结分析
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1D-consolidation analysis based on UH model considering time effect
HU Jing, YAO Yangping
School of Transportation Science and Engineering, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Abstract:The soil stress-strain relationship under 1D consolidation condition was derived from the unified hardening (UH) model considering time effect. Based on this, a governing differential equation of 1D consolidation was established, which could simultaneously describe the deformation behavior of both primary and secondary consolidation. The one direction drainage consolidation problem was analyzed by the differential method. Since there is the phenomenon of relaxation that the effective stress pressure near the impermeable layer would decrease during the initiation of loading, a formula that can reflect the decrease of effective stress by time was deduced. Then, numerical analysis of the influence of secondary consolidation parameter, over consolidation ratio and the consolidation and swelling index was made and the results prove the conclusion of the formula. Besides, the laboratory tests were used to confirm the numerical prediction results of the governing equation. Depending on the condition that when the primary consolidation was almost finished, the main deformation was produced by secondary consolidation, a relationship between average degree of consolidation and time was deduced, which could be used to predict the time when primary consolidation would be finished.
Key words: unified hardening (UH) model     creep     degree of consolidation     settlement deformation     pore water pressure

1 固结控制微分方程 1.1 软土的一维应力-应变关系

1.2 固结控制方程推导

2 预测及分析 2.1 预测条件

 图 1 差分方法计算示意图Fig. 1 Sketch of calculation of differential method

 参数 Cc Cs Cα R0 M e0(p0=10kPa) 数值 0.0217 0.0131 0.0108 0.95 1.112 0.53
2.2 孔压升高现象探讨

 图 2 孔压随深度分布规律Fig. 2 Distribution law of pore-water pressure in different depths

2.3 模型预测规律探讨

 图 3 平均固结度随时间变化曲线Fig. 3 Variation curves of mean degree of consolidation changing with time

3 试验验证

 图 4 800~1600kPa加载实测与模型预测结果对比Fig. 4 Comparison between test and model prediction results when loading ranges from 800kPa to 1600kPa

 参数 Cc Cs a/kPa-1 e0(p0=800kPa) H/mm 数值 0.356 0.0733 1.34×10-4 0.82 14.8

4 固结时间的确定

4.1 固结时间理论推导

tata0t组成.由式(5)老化时间与超固结参数的关系,可得

4.2 公式验证及讨论

 图 5 近似解析式(20)与模型预测结果对比Fig. 5 Comparison between results of approximate analytic solution Eq.(20) and model prediction

 图 6 Cα/k值对平均固结度的影响Fig. 6 Influence of Cα/k on mean degree of consolidation
5 结 论

1) 加载初期,模型预测结果可能存在孔压上升、有效应力减小的松弛现象,推导了有效应力随时间减小的表达式,给出了出现这一结果的原因.

2) 次固结系数、超固结度、压缩、回弹指数等参数对固结度与沉降变形均有影响,引起土体变形增大的参数往往导致固结时间增加.

3) 通过室内试验验证了本文模型的预测结果,在最终变形相同的情况下,本文模型所得孔压消散快于太沙基固结理论.本文模型可以合理地预测变形随时间发展的规律.

4) 对次固结变形段进行解析分析,推导出固结时间与固结度的关系,可以用于计算固结基本完成需要的时间,方便确定预压固结所需的时间.

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文章信息

HU Jing, YAO Yangping

1D-consolidation analysis based on UH model considering time effect

Journal of Beijing University of Aeronautics and Astronsutics, 2015, 41(8): 1492-1498.
http://dx.doi.org/10.13700/j.bh.1001-5965.2014.0583