重载铁路水泥改良膨胀土工程特性与路用性能

为了探究重载铁路水泥改良膨胀土路基填料的工程特性及路用性能，采用室内动三轴试验、微观结构试验、路基原位动力试验相结合的方法，揭示了膨胀土掺入水泥3%～5%改良前后静态指标与动态指标的变化特征，分析了水泥掺量5%和3%改良膨胀土分别用作重载铁路基床底层及以下路堤填料建设期的工作性能，评估了服役期列车动载作用下路基的动力稳定性. 研究结果表明:膨胀土掺入3%～5%水泥改良后，强度提高同时胀缩性显著降低，水稳定性提高3～4倍；相比重塑素膨胀土，水泥掺量3%～5%改良膨胀土临界动应力提高5～6倍；检测路基压密程度与强度指标满足规范且有较大富裕，监测路基中线地基沉降在铺轨前处于稳定状态；原位动力测试表明列车动载作用下路基的动应力沿深度逐渐衰减，在基床表层与基床底层范围内最大衰减量分别可达40%和80%以上，动应力影响深度是基床设计厚度的1.4～1.8倍，动应力影响深度范围内路基的动应力值远小于同位置填料的临界动应力，运营期路基动力稳定性满足安全服役要求. 研究成果能够为重载铁路水泥改良膨胀土路基精细化建设养修提供理论参考. 

Engineering Characteristics and Road Performance of Cement-Stabilized Expansive Soil for Heavy Haul Railways

In order to explore the engineering characteristics and road performance of cement-stabilized expansive soil filler when it used as the subgrade filler of heavy haul railways, the dynamic triaxial tests, micro-structure tests and in-situ dynamic tests of subgrade were combined to reveal the variation characteristics of static and dynamic indexes when 3%?5% cement was added into expansive soil. The 5% and 3% modified expansive soil was analyzed in terms of their working performances when used as filler of subgrade bottom and embankment of heavy haul railways, and the dynamic stability of the subgrade in service period was evaluated under dynamic train load. The results show that the mix of 3%?5% cement can increase the strength of expansive soil, significantly reduce the swelling and shrinkage, and increase the water stability by 3?4 times. Compared with remolded expansive soil, the critical dynamic stress of the improved expansive soil with 3%?5% cement is increased by 5?6 times. The compaction degree and strength index of the test subgrade meet the standard with moderate margin. The foundation settlement of the middle line for the test subgrade is in the stable state before rail laying. In-situ dynamic tests show that the dynamic stress of subgrade gradually decreases along with the depth under the action of dynamic train load. The maximum attenuation can reach 40% and 80% respectively in the range of the surface layer and the bottom layer of the subgrade. The influence depth of dynamic stress is 1.4?1.8 times the design thickness of the subgrade. The dynamic stress value of roadbed in the influence depth of dynamic stress is far less than the critical dynamic stress of the filler at the same position, demonstrating that the dynamic stability of the subgrade meets the requirements of safe service.