An experimental study of dynamic parameters of unit cell of deep mixed column-reinforced soft clay under dynamic loading
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摘要:
水泥土桩被广泛应用于软土路基加固工程中。然而，人们对水泥桩与桩间土形成的加固体的动力特性尚缺乏认识，无法合理评价水泥土桩复合地基的长期性能。基于此，本文开展水泥土桩复合体大型动三轴试验，研究围压、静偏应力、置换率及分级加卸载路径对其动力参数的影响，并分析了动力参数的波动性。试验结果表明：随着静偏应力增加，复合单元体的动弹模量减小，阻尼比增大，临界动应力比减小。随着置换率增加，动弹模量略有增加，阻尼比略有减小。逐级卸载造成复合单元体的动力参数劣化。阻尼比具有较强的波动性，复合单元体阻尼比的变异系数是动弹模量的2.8～7.0倍。相比于软土，复合体动弹模量提高了2～6倍，静偏应力越大，提高系数越大。
Abstract:Composite soil with deep mixed column is widely used in strengthening soft soil subgrade. However, there is still a lack of understanding the dynamic characteristics of composite soil with deep mixed column and evaluating unreasonably the long-term performance of composite soil with deep mixed column. Based on above, this study conducted a series of large-scale triaxial test to investigate the influence factors of static deviator stress, replacement ratio and incremental loading/unloading on the dynamic parameters of unit cell of deep mixed column-reinforced soft soil. The results show that with the increase of the static deviator stress, the dynamic elastic modulus increases, the damping ratio decreases, and the critical dynamic stress ratio decreases. With the increase of the area replacement ratio, the dynamic elastic modulus increases slightly and the damping ratio decreases slightly. The staged unloading can deteriorate the dynamic properties of the unit cell. The damping ratio is of strong volatility, and the variation coefficient of damping ratio is 2.8 to 7.0 times that of the dynamic elastic modulus. The dynamic elastic modulus of the unit cell of the composite soil is 2 to 6 times that of the soft soil, and the improvement factor increases with the increase of the static deviator stress.
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表 1 试验方案
Table 1. Test scheme
项目 试验编号 围压
/kPa动应力比 置换率
/%静偏应力
/kPa水泥土桩复合体
（大型动三轴试验）DC1 80 0.25～0.45 11.1 5 DC2 80 0.25～0.45 11.1 24 DC3 80 0.25～0.45 11.1 32 DC4 80 0.25～0.45 11.1 40 DC1 80 0.25～0.45 11.1 5 DC5 80 0.25～0.45 16.0 5 DC6 80 0.25～0.45 21.7 5 DC7 40 0.25～0.45 11.1 5 DC8 60 0.25～0.45 11.1 5 DC1 80 0.25～0.45 11.1 5 DC9 80 0.45～0.25 11.1 5 水泥土（动三轴试验） DC10 80 0.25～0.45 100 5 DC11 80 0.25～0.45 100 24 DC12 80 0.25～0.45 100 32 DC13 80 0.25～0.45 100 40 软土（动三轴试验） DC14 80 0.15 0 5 DC15 80 0.15 0 24 DC16 80 0.15 0 32 DC17 80 0.15 0 40 
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表 2 不同材料的动力参数取值范围
Table 2. Value ranges of dynamic elastic modulus of different materials
试验材料 试验内容 动力参数 动弹性模量Er/MPa 阻尼比Dr 软土 静偏应力−5kPa 53 ~ 70 0.056 ~ 0.070 静偏应力−24kPa 30 ~ 60 0.064 ~ 0.068 静偏应力−32kPa 25 ~ 455 0.084 ~ 0.090 静偏应力−40kPa 15 ~ 25 0.086 ~ 0.093 复合体
m=11.1%静偏应力−5kPa 100 ~ 22 0.050 ~ 0.079 静偏应力−24kPa 95 ~ 120 0.056 ~ 0.075 静偏应力−32kPa 100 ~ 115 0.062 ~ 0.085 静偏应力−40kPa 90 ~ 110 0.065 ~ 0.100 复合体
m=16.0%静偏应力−5kPa 110 ~ 125 0.052 ~ 0.075 复合体
m=21.7%静偏应力−5kPa 120 ~ 135 0.027 ~ 0.059 水泥土 静偏应力−5kPa 100 ~ 108 0.032 ~ 0.075 静偏应力−24kPa 110 ~ 120 0.039 ~ 0.069 静偏应力−32kPa 114 ~ 123 0.049 ~ 0.054 静偏应力−40kPa 118 ~ 126 0.040 ~ 0.055
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