Comprehensive Assessment Method for Health Status of Subgrade in Existing Line Speed-Raising Reconstruction

To deal with the speed-raising reconstruction for an existing railway line, the health status of the subgrade of the line need to be assessed first. On the basis of a field investigation of the subgrade damage, the subgrade was divided into 24 segments to be tested according to the severity of subgrade damage, filling material, and the structure of subgrade bed. A total of 754 groups of compaction tests, 345 groups of dynamic elastic modulus tests, and 1 311 groups of light dynamic penetration tests on different positions were conducted, and the test results were analyzed. The analysis indicates that the comprehensive assessment method for health status of subgrade, which combines light dynamic penetration and compaction tests with dynamic elastic modulus tests based on a field investigation, can adequately reflect the strength, rigidity, and durability of subgrade. This method is proved to be reliable, and the test results by it can be directly applied to the design of the technical scheme of subgrade reconstruction.