列车荷载下风积沙填料弹性应变及预测模型

Elastic strain and prediction model of aeolian sand filler under train-induced loading

随着我国沙漠铁路不断向沙漠腹地修建延伸,取得路基填筑所需级配良好填料的运距逐渐增加,导致铁路建设投资大幅提高,因此就地取材采用风积沙填筑路基已成为一种趋势,但在循环荷载作用下风积沙填料的弹性应变规律还不明确。为研究循环荷载作用下风积沙填料的弹性应变规律,结合和若铁路列车运行工况,开展一系列考虑动应力幅值、围压、压实系数、含水率及频率等弹性应变影响因素的循环荷载试验,建立与土体性质、围压及循环动荷载参数相关的风积细砂填料弹性应变预测模型。试验结果表明,细砂填料的弹性应变变化规律与动应力幅值、围压、压实系数、含水率、频率等因素有关:动应力幅值的增加会加剧细砂填料弹性应变的发展;通过提高围压、压实系数可有效改善细砂填料动力性能,减小弹性应变的发展;随着含水率的增加,细砂填料试样的弹性应变先减小后增大,天然含水率和饱和含水率试样的弹性应变较为接近,最优含水率试样弹性应变最小;频率对细砂填料应变的影响与围压有关,围压较小时频率与应变负相关,围压较大时频率与应变正相关。采用弹性应变预测模型对典型试样结果进行预测,取得了良好的预测效果。研究结果可为沙漠铁路风积沙路基结构优化及长期动力稳定性评估提供理论支持。

With the continuous extension of desert railway to the hinterland of the desert,the haul distance to obtain the well-graded subgrade fill materials is gradually increasing,which leads to the increase of railway construction investment.Therefore,it has become a trend to fill subgrade with local aeolian sand,but the elastic strain rule of the aeolian sand packing under cyclic load is not clear.In order to study the elastic strain law of aeolian sand packing under cyclic load,a series of cyclic load tests were carried out considering dynamic stress amplitude,confining pressure,compaction coefficient,water content,frequency and other factors affecting the elastic strain,and a prediction model of elastic strain of fine sand packing related to soil properties,confining pressure and dynamic load parameters was established.The test results show that the elastic strain variation of fine sand packing is related to dynamic stress amplitude,confining pressure,compaction coefficient,water content,frequency and other factors.The increase of dynamic stress amplitude accelerates the development of elastic strain of fine sand packing,and the dynamic performance of fine sand packing can be effectively improved by increasing confining pressure and compaction coefficient,which can concurrently reduce the development of elastic strain.With the increase of water content,the elastic strain of fine sand packing sample first decreases and then increases.The elastic strain responses of specimens prepared at natural water content and saturated water content are close to each other,and the elastic strain responses of specimens prepared at optimal water content are the minimum.The influence of loading frequency on the strain of fine sand packing is related to confining pressure.The frequency is negatively correlated with the strain when the confining pressure is small,and positively correlated with the strain when the confining pressure is large.The elastic strain prediction model is used to predict the results of typical samples,achieving satisfactory results.The results can provide theoretical support for structural optimization and long-term dynamic stability evaluation of aeolian sand subgrade of desert railway.