Experimental Study on the Influence of Consolidation Time on Dynamic Characteristics of Soft Soil
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摘要: 固结试验是研究软土动力特性的重要环节，固结时间是影响软土动力特征参数的重要因素。围绕岩土工程及科研工作中对动三轴试验中固结时间影响规律的认识较为模糊的问题，拟对天津滨海软土开展动三轴平行试验，分别采用8h、12h、24h、48h进行固结，针对软土的最大动剪切模量Gmax、最大阻尼比λmax及动剪切模量比Gd/Gmax和阻尼比λ随动剪切应变γd的变化规律，分析固结时间对软土动力特性参数的影响。试验结果表明：Gmax、λmax、Gd/Gmax-γd曲线、λ-γd曲线受固结时间的影响较为显著。Gd/Gmax-γd曲线随着固结时间的增加而减小。阻尼比试验结果表明动剪切应变存在明显的分界点，分界点以下，中长期固结时间所得阻尼比较大，而分界点以上，短期固结时间所得阻尼比较大。Abstract: The consolidation test is an important step of dynamic characteristic test for soft soil, and the consolidation time is an important factor affecting the dynamic characteristic parameters of soft soil. To address the uncertainty of the consolidation time in triaxial test for engineering and scientific research work, the parallel triaxial tests of soft soil will be carried out in this paper, by using the 8 hours, 12 hours, 24 hours and 24 hours to finish the consolidation test. The influence of consolidation time on dynamic characteristics of soft clay is analyzed through the test results of characteristic parameters, such as Gmax, λmax, G/Gmax-γ curve, λ-γ curve. The results show that dynamic characteristics parameters of soft soil are significantly affected by consolidation time. The values of G/Gmax-γ decrease with the increase in consolidation time. The damping ration test results show that there is a clear boundary point for dynamic shear strain. Below the boundary point, the damping obtained at the mid-to-long term consolidation time is relatively large, while above the point, the damping obtained at the short-term consolidation time relatively large.
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Key words:
- Coastal soft soil /
- Consolidation time /
- Dynamic shear modulus /
- Damping ratio
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图 3 动应力-动应变滞回曲线
Figure 3. Stress-strain hysteresis loop by different consolidation time
图 4 动剪切模量和阻尼比的拟合结果对比
Figure 4. Comparison of fitting result for dynamic modulus and damping
图 5 Gmax、λmax与固结时间的关系
Figure 5. The relationships between consolidation time and Gmax, λmax
图 6 Gd/Gmax –γd和λ-γd曲线
Figure 6. The curve of G/Gmax –γ and λ-γ under different consolidation time
表 1 试验用土物理力学性质指标
Table 1. Physical and mechanical properties of test soft soil
指标 量值 指标 量值 深度/m 5 天然密度/(g·cm-3) 1.8 含水量/% 39.8 液限/% 30.7 比重 2.52 塑限/% 18.1 孔隙比 1.09 
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表 2 动三轴试验特征参数拟合值
Table 2. Characteristic fitting parameters of dynamic triaxial test
固结时间 8h 12h 24h 48h a 0.041 0.038 0.025 0.023 b 0.167 0.190 0.232 0.255 Gmax 24.6 26.5 39.5 43.4 λmax 0.258 0.236 0.210 0.179 τulb 5.99 5.26 4.31 3.92
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表 3 典型动剪切应变下的动剪切模量比与阻尼比
Table 3. The values of shear modulus and damping ratio by typical shear strains
γd(×10-4) 固结时间 8h 12h 24h 48h Gd/Gmax λ Gd/Gmax λ Gd/Gmax λ Gd/Gmax λ 100 0.1974 0.2568 0.1667 0.2329 0.0975 0.2010 0.0826 0.1722 50 0.3298 0.2550 0.2857 0.2305 0.1776 0.1998 0.1525 0.1701 10 0.7110 0.2440 0.6667 0.2180 0.5192 0.1900 0.4737 0.1660 5 0.8311 0.2307 0.8000 0.2103 0.6835 0.1843 0.6429 0.1616 1 0.9609 0.1903 0.9524 0.1700 0.9153 0.1560 0.9000 0.1404 0.5 0.9801 0.1452 0.9756 0.1355 0.9558 0.1307 0.9474 0.1196 0.1 0.9960 0.0295 0.9950 0.0450 0.9908 0.0561 0.9890 0.0659 0.05 0.9980 0.0083 0.9975 0.0217 0.9954 0.0324 0.9945 0.0372
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