Study On The Application Of Subgrade Detecting Methods For Existing Railway

China’s existing railway lines are long and distribute widely. And there are quite a few already existing and potential diseases in railway track substructure, which poses a threat to the security of the trains in operation. Therefore, how to carry out subgrade detection quickly, reliably and comprehensively in existing railway has become an urgent problem.Current detecting methods, however, are difficult to obtain the strength and deformation indicators of the railway roadbed. Based on the "863" Program’Research on the Detection and Reinforcement Techniques for the Subgrade and Bridge of Heavy Haul Railway’, thed, K30, and Ev2tests have been proposed to be adopted in existing railway subgrade detection. In order to carry out K30and Ev2tests for existing railway, an effective set of counter-force device and test bed have been proposed in this paper, which can not only provide adequate counter-force for K30and Ev2tests, but also be for the convenience of installating equipment on the slope. Then, the engineering properties of subgrade filling have been investigated by conventional soil tests and static triaxial test. In order to investigate the subgrade condition before reinforcement and evaluate the reinforcement effect by using inclined jet grouting piles, a subgrade detecting scheme of Shuo-Huang heavy haul railway has been designed. The detection methods mianly include compaction coefficient (K) test, light dynamic penetration (N10) test, dynamic modulus of deformation (Evd) test, subgrade reaction coefficient (K30) test, second modulus of deformation(Ev2) test, ground penetrating rada detection and exploration by using elastic wave. Based on the test results, the correlation among the five test parameters have been analyzed and the effect of reinforcement has been evaluated. The research presents that inclined jet grouting pile technique is an effective reinforcement method for railway subgrade. There is a good linear relationship between the basic foundation bearing capacity before and after the reinforcement. And there is also a good linear relationship between K30and Ev2test results after the reinforcement. Finally, the guidelines for subgrade detection in existing heavy hual railway have been put forward in this paper.