循环荷载作用下硫酸盐渍土路基动力特性试验研究

Experimental study on dynamic behavior of sulphate soil subgrade under cyclic loading

以朔黄重载铁路某区段硫酸盐渍土路基为研究对象,基于GCTS空心圆柱扭剪仪,模拟重载列车运营时正向和水平向循环应力耦合的荷载条件,研究硫酸盐渍土路基在往复荷载作用下的动力特性。试验结果表明,循环围压限制了路基土体变形,使盐渍土累积应变发展速率减小,回弹模量增大;同时路基土体累积应变和回弹特性受循环偏应力影响,随循环偏应力幅值的增大,累积应变增大,回弹模量减小,在较大偏应力幅值下,回弹模量在加载早期下降明显,土体结构破坏较大,实际工程中应增加路基的侧向约束,以提高路基土体的稳定,限制盐渍土路基沉降,同时应严格控制重载列车的载重;试验存在临界加载间歇,累积应变的发展规律在间歇前后差异较大,并随加载间歇的延长而降低,基于此,在实际应用中,应根据重载列车型号的不同,适当控制车速。对试验结果进行拟合,得到了累积应变随循环振次的发展模型,为预测和防治硫酸盐渍土路基沉降提供理论依据。

The sulphate soil subgrade of a certain section of the Shuozhou-Huanghuagang Heavy Duty Railway is studied. Based on the GCTS device, the coupled load conditions of the positive cyclic stress and the horizontal cyclic stress during the heavy-load train operation are simulated to study the dynamic behavior of sulphate soilunder cyclic loading.The results show that, under undrained conditions, the cyclic confining pressure limits the deformation of soil, so that the accumulated strain of saline soil decreases, and the modulus of resilience increases.The accumulated strain and rebound characteristics of the subgrade soil are affected by the cyclic deviatoric stress. As the amplitude of the cyclic deviatoric stress increases, the accumulated strain increases and the modulus of resilience decreases. Under the larger deviatoric stress amplitude, the modulus of resilience drops significantly in the early stage of loading, and the structure damage of the soil is larger.In the actual project, the lateral restraint of the subgrade should be increased to improve the stability of the subgrade soil and limit the settlement of the saline soil subgrade.The load of the heavy-duty train should be strictly controlled.Based on this, in practical applications, the vehicle speed should be properly controlled according to the type of heavy-duty train.There is a critical loading interval, and the accumulated strain is very different before and after the critical loading interval.The test results are fitted to obtain the development model of cumulative strain with cyclic vibration, which provides a theoretical basis for predicting and preventing the settlement of sulfate soil subgrade.