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.