LABORATORY TESTS ON DYNAMIC MODULUS AND DAMPING RATIO OF CEMENT-STABILIZED EXPANSIVE SOIL AS SUBGRADE FILLING OF HEAVY HAUL RAILWAY
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摘要: 动弹模量与阻尼比是土动力学分析中的重要力学参数，考虑重载铁路荷载特征定量分析水泥改良膨胀土的动模量和阻尼比的较少。依托蒙西至华中地区铁路煤运通道(简称蒙-华铁路)工程为背景，采用南阳邓州市大山寨膨胀土，通过在不同频率、围压、固结比及动应力幅值下的持续振动三轴试验，研究了水泥掺量3%和5%水泥改良膨胀土的动弹模量及阻尼比，并与膨胀土素土进行对比分析。结果表明：水泥掺量3%和5%改良膨胀土的最大动弹模量约为膨胀土素土的3~4倍；在动弹模量-应变曲线中，动应变小于0.002时表现为陡降段，动弹模量随动应变增长降幅达70%，而动应变大于0.002时降幅较小，动弹模量随动应变增长趋于稳定；动弹模量随围压、频率、水泥掺量增加而增大，阻尼比随围压、固结比增加而减小；低应变水平下，固结比与动模量成正相关关系，高应变水平下，固结比与动弹模量成负相关关系。同时，对动弹模量及阻尼比进行了归一化分析，建立了估算动弹模量及阻尼比的经验公式。Abstract: Dynamic elastic modulus and damping ratio are important mechanical parameters in soil dynamics analysis. Considering the characteristics of heavy-duty railway loads, the dynamic modulus and damping ratio of cement-stabilized expansive soil are less. Based on the background of the railway coal transportation channel(hereinafter referred to as Meng-Hua Railway) in the central area of the city of Tolemon and the central China, the dynamic modulus and damping ratio of 3% and 5%cement reinforced expansive soils were studied and compared with the expanded soil from Dashanzhai expansive soil in Dengzhou City, Nanyang, under the consolidation with different frequencies, confining pressure, ratio and dynamic stress amplitude. The results were compared with expansive soils. The results show that the maximum dynamic modulus of cement modified with 3% and 5%modified expansive soil is about 3-4 times that of expansive soil. When the dynamic strain is less than 0.002, the dynamic elastic modulus has a steep drop and decreases by 70%. In the dynamic elastic modulus-strain curve, when the dynamic strain is greater than 0.002, the decrease is small, and the dynamic elastic modulus tends to be stable with the dynamic strain. The dynamic elastic modulus increases as the confining pressure, the frequency and the cement content increase. Damping ratio decreases as the confining pressure and consolidation ratio increase. At low strain levels, the consolidation ratio is positively correlated with the dynamic modulus. At high strain levels, the consolidation ratio is inversely related to the dynamic modulus. At the same time, the dynamic modulus and damping ratio are normalized and analyzed, and an empirical formula for estimating the dynamic modulus and damping ratio is established.
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Key words:
- Heavy haul railway /
- Cement-stabilized expansive soil /
- Dynamic modulus /
- Damping ratio
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图 2 水泥(3%)改良膨胀土(f=1，kc=1)
a. Ed~εd曲线；b. 1/Ed~εd曲线
Figure 2. Cement(3%)-stabilized expansive soil(f=1, kc=1)
图 3 水泥(5%)改良膨胀土(f=1，kc=1)
a. Ed~εd曲线；b. 1/Ed~εd曲线
Figure 3. Cement(5%)-stabilized expansive soil(f=1, kc=1)
图 4 阻尼比λ~εd变化曲线
a.素膨胀土(f=1，kc=1)；b.水泥掺量3%改良膨胀土(f=1，kc=1)；c.水泥掺量5%改良膨胀土(f=1，kc=1)
Figure 4. Damping ratio λ~εd curve
图 5 动弹性模量归一化曲线(膨胀土素土)
Figure 5. Dynamic modulus of elasticity normalized curve(expansive soil)
图 6 动弹性模量归一化变化曲线(3%水泥改良膨胀土)
Figure 6. Dynamic modulus of elasticity normalized curve (3% cement-stabilized expansive soil)
图 7 动弹性模量归一化变化曲线(5%水泥改良膨胀土)
Figure 7. Dynamic modulus of elasticity normalized curve (5% cement-stabilized expansive soil)
表 1 大山寨膨胀土基本物理力学参数
Table 1. Basic physical and mechanical parameters of expansive soil in Dashanzhai
天然含水率/% 天然密度/g·cm-3 液限/% 塑限/% 塑性指数 液性指数 内摩擦角/(°) 黏聚力/kPa 压缩系数/MPa-1 压缩模量/MPa 自由膨胀率/% 蒙脱石含量/% 阳离子交换量/mmol·kg-1 膨胀力/kPa 无荷膨胀量 20.0~27.5 1.75~2.01 36.9~50.3 23.7~27.9 13.2~21.4 0.04~0.31 18~22 38~46 0.19~0.23 7.22~9.01 55~73 22~28 276~390 27~129 15~30 
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表 2 水泥改良膨胀土基本物理力学参数(平均值)
Table 2. Basic physical and mechanical parameters of cement-stabilized expansive soil(average value)
掺量/% 最佳含水量/% 液限/% 塑限/% 内摩擦角/(°) 黏聚力/kPa 自由膨胀率/% 膨胀力/kPa 无侧限抗压强度/kPa 3 14.9 42.4 27.9 27.6 139 32 14 335(饱和样) 4 15.2 41.6 28.8 31.8 204 28 10 512(饱和样) 5 15.3 41.4 29.5 41.8 244 23 1 852(饱和样)
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表 3 试验参数
Table 3. Test parameters
试验工况 频率/Hz 固结比 固结围压/kPa 素膨胀土 1、5 1.0 15，30 2.0 15，30 3%水泥改良膨胀土 1、5 1.0 15，30，60 2.0 15，30，60 5%水泥改良膨胀土 1、5 1.0 15，30，60 2.0 15，30，60
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表 4 最大动弹性模量Edmax
Table 4. Maximum dynamic modulus Edmax
频率
/Hz固结比 围压
/kPa素膨胀土
/MPa3%改良土
/MPa5%改良土
/MPa1 1 15 68.68 184.84 243.90 30 84.53 207.47 270.27 60 / 234.74 285.71 1 2 15 78.99 235.29 338.98 30 117.51 239.23 347.22 60 / 280.11 357.14 5 1 15 79.11 215.05 270.27 30 102.25 238.10 297.62 60 / 242.72 322.58 5 2 15 95.60 289.02 358.42 30 141.64 320.51 398.41 60 / 336.70 454.55
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表 5 最大阻尼比λmax
Table 5. Maximum damping ratio λmax
频率/Hz 固结比 围压/kPa 素膨胀土 3%改良土 5%改良土 1 1 15 31.21 25.16 26.77 30 27.33 21.73 22.55 60 / 17.56 18.76 1 2 15 20.33 14.48 15.32 30 18.76 12.36 13.47 60 / 10.39 10.78 5 1 15 38.21 29.14 28.15 30 36，87 25.37 25.32 60 / 19.33 17.59 5 2 15 25.77 20.15 21.39 30 23.49 18.44 19.63 60 / 12.47 13.56
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