持续动荷载作用下基床粗粒土填料累积塑性应变试验研究

Experimental Study on Accumulated Plastic Strain of Coarse Grained Soil Filling in Subgrade Bed under Persistent Dynamic Loading

粗粒土填料在重载铁路基床层广泛应用,其受列车动荷载影响明显,研究基床粗粒土在持续动荷载作用下的累积变形有重要意义。通过制作不同含水率的粗粒土试样,对试样开展不同围压、不同动应力幅值的大型动三轴试验,分析试样在持续动荷载作用下轴向累积塑性应变的增长特点。基于安定理论,划分不同条件下试样的动力行为,探讨含水率对粗粒土试样累积塑性应变的影响,得出不同动力行为之间的临界应力表达式。建立塑性蠕变动力行为累积塑性应变预测模型,模型的准确性验证表明:此模型在动荷载重复次数N≥50 000时有较高准确性。试验结果对重载铁路基床层动力稳定性评价有参考价值。

As coarse grained soil filling,which is widely applied in heavy haul railway subgrade bed,is greatly affected by train-induced dynamic loading,the study of accumulated deformation of coarse grained soil in subgrade bed under the action of persistent dynamic load is of great significance.By making coarse grained soil samples with different moisture content,a series of large-scale dynamic triaxial tests with different confining pressures and dynamic stress amplitudes were carried out to analyze the increment characteristics of axial accumulated plastic strain of the samples under persistent dynamic loading.Based on the shakedown theory,the dynamic behaviors of the samples under different conditions were divided to discuss the influence of water content on accumulated plastic strain of coarse grained soil samples.The empirical formulas of critical stress among different dynamic behaviors were established.A prediction model of accumulated plastic strain for the plastic creep dynamic behavior was also established.The verification of the accuracy of the prediction model proved the high accuracy of the model under the condition that the number of loading repetition Nis greater than fifty thousand.The results of these tests provide reference value in the evaluation of dynamic stability of heavy haul railway subgrade bed.