Consolidation characteristics of the turfy soil in seasonally frozen area
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摘要:
季冻区草炭土的工程性质很差，具有高压缩性的同时蠕变特性明显，路基工后沉降量大。目前针对季冻区草炭土固结压缩蠕变特性的研究仍相对匮乏，亟需对其固结压缩及蠕变特性进行深入研究，为季冻区草炭土路基的沉降预测提供参数依据。选取吉林省敦化市江源镇典型季冻区草炭土为研究对象，通过一维固结压缩试验和一维固结蠕变试验，获得草炭土压缩系数、固结系数和次固结系数分布范围及纤维含量对草炭土主、次固结特性的影响规律。试验表明：分级加载下，草炭土纤维含量越大，压缩性越强，两者呈正相关性；固结系数（Cv）范围为1.00×10−3~8.39×10−3 cm2/s，固结系数随固结压力增大而减小，当固结压力超过200 kPa之后基本稳定。次固结系数（Cα）范围为0.022~0.095，次固结系数随固结压力增大而增大，到达峰值后逐渐减小，峰值时所对应的固结压力介于50~100 kPa之间；当固结压力一定时，纤维含量越大固结蠕变越明显，次固结系数越大。吉林敦化草炭土的次固结系数和压缩指数具有一定的相关性，纤维质量占比为21%、34%、48%、59%、73%的草炭土对应的次固结系数与压缩指数比值（Cα/Cc）分别为0.0452，0.0331，0.0303，0.0246，0.0245。
Abstract:The turfy soil in seasonally frozen regions has very poor engineering properties, with high compressibility and obvious creep characteristics. The settlement of roadbed after construction is large. Therefore, it is urgent to conduct in-depth researches due to the lack of consolidation compression and creep characteristics researches of turfy soil in seasonally frozen regions, so as to provide parameters for the settlement prediction of the turfy soil roadbed in seasonally frozen regions. The typical turfy soil in seasonally frozen region near the Jiangyuan town of the city of Dunhua in Jilin Province is selected as the research object. Through 1D consolidation compression test and 1D consolidation creep test, the distribution range of the compression coefficient, consolidation coefficient and secondary consolidation coefficient of the turfy soil and the influence of fiber content on the primary and secondary consolidation characteristics of the turfy soil are obtained. The experimental results show that under graded loading, the greater the fiber content is, the stronger the compressibility of turfy soil is, showing a positive correlation. Consolidation coefficient (Cv) ranges from 1.00×10−3 to 8.39×10−3 cm2/s. Cv decreases with the increase of consolidation pressure. When the consolidation pressure exceeds 200 kPa, Cv is basically in a stable range. The secondary consolidation coefficient (Cα) ranges from 0.022 to 0.095. Cα increases with the increasing consolidation pressure, then decreases gradually after reaching the peak value when the corresponding consolidation pressure varies between 50 kPa and 100 kPa. When the consolidation pressure is constant, the higher the fiber content is, the more obvious the consolidation creep is, and the higher Cα is. There is a certain correlation between the secondary consolidation coefficient and compression index of the Dunhua turfy soil in Jilin Province. The Cα/Cc numerical values corresponding to the turfy soil with the fiber content of 21%, 34%, 48%, 59% and 73% are 0.0452, 0.0331, 0.0303, 0.0246 and 0.0245, respectively.
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Key words:
- turfy soil /
- consolidation compression /
- consolidation creep /
- fiber content /
- Cα/Cc
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表 1 吉林敦化草炭土不同深度有机质质量分数（Wu）和纤维质量分数（Wf）
Table 1. Organic matter content and fiber content of the turfy soil at different depths near Dunhua in Jilin
深度/m Wu/% Wf /% 0.0~1.0 53.28~81.35 40.99~73.78 1.0~2.0 36.25~65.81 30.83~49.12 2.0~2.4 38.37~55.25 19.83~37.65 
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表 2 吉林敦化草炭土样基本物理指标
Table 2. Basic physical indexes of the turfy soil samples near Dunhua in Jilin
深度/m 取样编号 密度ρ/（g·cm−3） 含水率w/% 比重Gs 初始孔隙比e0 有机质质量分数Wu /% 纤维质量占比Wf /% 0.0~0.5 K1-1 0.99 416.83 1.31 8.88 79.43 73 0.5~1.0 K2-1 1.05 392.92 1.62 7.11 67.12 59 1.0~1.5 K3-1 1.09 306.08 1.68 5.33 65.81 48 1.5~2.0 K4-1 1.14 242.18 2.09 4.50 50.88 34 2.0~2.4 K5-1 1.17 198.27 1.96 2.91 39.10 21
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表 3 云南滇池土样[18]和云南大理土样[19]基本物理指标
Table 3. Basic physical indexes of Yunnan Dianchi Lake soil samples and Yunnan Dali soil samples
土样
名称深度/
m取样
编号含水率
w/%比重
Gs初始
孔隙比e0有机质
质量分数Wu/%滇池
泥炭土2.5~3.0 CT1-1 64.6 2.4 1.4 15.7 7.5~8.0 CT2-1 203.4 2.1 4.4 48.1 1.0~2.0 CT3-1 406.3 1.5 6.4 69.3 大理
泥炭土1 S1 171.7 41.8 1 S6 162.1 32.1 1 S7 118.0 34.8
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表 4 试验方案
Table 4. Test schemes
试验名称 试验目的 Wf/% 加荷序列/
kPa加荷比 历时/d 固结
压缩
试验先期固结
压力分析21 2.4-3.9-6.3-
12.5-25-50-
100-200-400
（12.5 kPa
开始每级1 d）— 7 34 48 59 73 固结
压缩
试验（1）压缩特性分析
（2）主固结特性分析21 12.5-25-50-
100-200-400
（每级1 d）1 6 34 48 59 73 固结
蠕变
试验固结蠕变
特性分析21 12.5-25-50-
100-200-400
（每级7 d）1 42 34 48 59 73
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表 5 不同纤维含量草炭土的Cv-p经验关系表达式
Table 5. Cv-P empirical relationship expression of the turfy soil with different fiber contents
Wf/% 拟合公式 相关系数 21 Cv=15.09p0.48 R2=0.96 34 Cv =19.43p0.50 R2=0.97 48 Cv=18.05p0.47 R2=0.94 59 Cv =21.72p0.49 R2=0.96 73 Cv =19.82p0.43 R2=0.93
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