Test on Dynamic Characteristics of Phosphogypsum Cement Improved Loess
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摘要: 为了改善黄土路基的动力特性，同时实现磷石膏的资源化利用，对不同配比下的磷石膏–水泥改良黄土进行了动三轴疲劳特性试验。试验结果表明：磷石膏–水泥改良黄土的动力特性较素土有较大改善，随着水泥掺比的增大，黄土的动弹性模量越大，阻尼比越小，震陷变形量也越小；在低动应力下，黄土在10000次振次内仅经历硬化阶段，随着动应力的增大，黄土开始产生振动损伤，且随着水泥掺比的增大，黄土的破坏方式由延塑性向脆性转变；随着动应力的增大，动弹性模量先增大后减小，阻尼比先减小后增大；经Hardin-Drnevich双曲线模型计算，磷石膏–水泥改良黄土的初始最大弹性模量有较大的提高，而初始动应力改变不明显；提出以等振次应力–应变曲线确定疲劳动应力门槛值，并得出磷石膏–水泥能有效提高黄土疲劳动应力门槛值的结论。研究结果可为黄土路基改良工程提供新的方法和思路，也可为实现磷石膏的资源化利用提供参考。Abstract: In order to improve the dynamic characteristics of loess subgrade and realize the resource utilization of phosphogypsum, the dynamic triaxial fatigue test of loess improved by phosphogypsum-cement with different proportion was carried out. The test results show that the dynamic characteristics of the loess improved by phosphogypsum-cement are better than that of the plain soil. With the increase of the cement ratio, the greater the dynamic elastic modulus of the loess, the smaller the damping ratio and the smaller the seismic subsidence deformation. Under the low dynamic stress, the loess only experiences the hardening stage in 10000 vibration times. With the increase of the dynamic stress, the loess begins to produce the vibration damage, and with the increase of the cement ratio, the failure mode of loess changes from ductility to brittleness; with the increase of dynamic stress, the dynamic elastic modulus increases at first and then decreases, and the damping ratio decreases at first and then increases. According to the Hardin-Drnevich hyperbolic model, the initial maximum elastic modulus of the loess improved by phosphogypsum-cement increased
greatly, but the change of the initial dynamic stress is not obvious. It is proposed to determine the threshold value of the fatigue dynamic stress by the stress-strain curve of equal vibration times. Phosphogypsum cement can effectively improve the threshold value of the fatigue dynamic stress of loess. The research results can provide new methods for the loess subgrade improvement project, and also provide reference for the realization of phosphogypsum resource utilization. -
表 1 试验方案
试验组 （水泥+磷石膏）/黄土 水泥/磷石膏 A 0 B 0.2 1∶4 C 0.2 1∶3 D 0.2 1∶2 E 0.2 1∶1 注：（水泥+磷石膏）/黄土、水泥/磷石膏均表示质量比。 
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表 2 Hardin-Drnevich双曲线模型参数计算结果
试验组 a b Edmax/MPa σdmax/kPa 相关系数R A 0.0244 3.200 40.98 312.5 0.984 B 0.0150 3.034 66.67 329.6 0.992 C 0.0127 3.036 78.70 329.4 0.990 D 0.0112 3.020 89.29 331.1 0.992 E 0.0089 3.179 112.2 314.6 0.983
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