铁路路基膨胀土工程特性指标试验研究

Experiment Study on Engineering Property Indexes of Expansive Soil for Railway Subgrade and Its Improvement Measures

为改善路基原状土的工程特性,以西安至南京铁路试验段为工程背景,进行了膨胀土填料工程特性的系统试验研究.采用室内土工物性基本试验、直剪试验以及动静三轴试验,对膨胀土的物理力学参数进行测定,针对工程改良土实际特性提出用掺石灰的方法改良原状土,分析对比了改良前后的颗粒分布、物理性质、水理性质、强度和膨胀性指标.结果表明:弱膨胀土及中等膨胀土经石灰改良处理后,土的颗粒组成、物理性质、胀缩特性均有明显改善,力学强度和水稳特性大大提高;根据物理与力学性质、胀缩性、水稳性等试验结果,推荐采用的最佳掺灰比为5%.

In order to improve the engineering properties of undisturbed subgrade soil,systematic indoor experiments were made to study the expansive soil for the railway subgrade filling in Xi＇an-Nanjing railway subgrade project.Physical and mechanical parameters of the expansive soil were measured by the basic tests of geotechnical properties,such as the direct shear test and tri-axial test.According to the actual engineering properties of the expansive soil,a soil improvement measure using lime was put forward.Parameters such as the particle size distribution,physical properties,waterphysical properties,strength,and expansibility of the expansive soil were tested and compared before and after improvement.The test results show that the weak-middle expansive soil gets an obvious improvement in particle composition,physical properties,and swelling behavior; and the mechanical strength and water stability are also enhanced greatly.According to the test results of mechanical and physical properties,the optimal ash mixing rate for the expansive soil is determined to about 5％.