水泥掺量和颗粒级配对碎石基床冻融特性影响的试验研究

基于水泥稳定碎石在寒区高速铁路路基基床中应用的工程背景,借鉴公路行业水泥稳定碎石工程性能评估方法并结合寒区高速铁路路基基床的特点,通过一系列室内试验,深入研究和分析了水泥掺量、颗粒级配对碎石基床压实效果、冻胀性能、渗透性能、冻融耐久性能和温干缩指标的影响规律。研究结果表明:试验配比条件下,水泥稳定碎石基床各项压实指标均满足或超过高铁路基基床压实标准。较大粒径土颗粒的缺失,削弱了水泥稳定碎石试样的冻胀敏感性,提高了渗透性,降低了强度和水稳定性;水泥的掺加有效地弥补了粒径缺失导致的强度降低现象,但却增大了温缩、干缩变形;抗压强度随冻融次数的增加呈现整体衰减的趋势,并在经历10次冻融后趋于稳定。工程实践中,建议选用细粒土含量3%、水泥掺量3%的级配碎石作为非渗水性基床填料,去除0.5 mm以下颗粒、水泥掺量3%的级配碎石作为渗水性基床填料。

Freeze-thaw characteristics of subgrade macadam fillings influenced by cement content and grain-size composition

Motivated by the practical application of cement-stabilized macadam to high-speed railway subgrade in cold regions, a series of tests are conducted using an integrated method learnt from an evaluation system used for semi-rigid highway foundations considering the characteristics of high-speed railway subgrade in cold regions. The compaction results, frost-heave property, permeability, freeze-thaw durability and shrinkage property of subgrade macadam fillings influenced by cement content and grain size composition are deeply studied and analyzed. The following results are obtained. The compaction indexes of cement-stabilized macadam subgrade are satisfied or exceed the compaction standard under the tested compositions. The lack of large-sized soil particles weakens the frost-heave sensibility, improves the permeability, and reduces the compressive strength and moisture stability of cement-stabilized macadam samples. In addition, a mixture of cement effectively compensates for the reduction in compressive strength and increases the shrinkage deformation of cement-stabilized macadam samples. The compressive strength decreases with every increment of freeze-thaw cycles, and then levels off after 10 freeze-thaw cycles. For the engineering practice of high-speed railway subgrade in cold regions, the cement-stabilized macadam with 3% of fines and 3% of cement addition is suitable for the subgrade without any demand for permeability, and the cement-stabilized macadam with grains greater than 0.5 mm in size and 3% of cement addition is suitable for the required permeability of subgrade.