Drop Hammer Dynamic Stiffness Instrument Simulation Analysis And Experimental Study

The coefficient of foundation(K₃₀) is a important index to evaluate the quality of thefilling in railway roadbed in our country. But the plate loading test to get the K₃₀ value isvery time consuming and complex. It needs a large equipment for loading and costing along hime to finish one test. Several new measure instruments which are more convenientand quicky are researched all over the world to replace the plate loading test. A newinstrumend Falling Hammer Dynamic Rigidity Meter is studied by the ChinaAcademy of Railway Sciences, it uses a falling hammer as the dynamic loading sourceinstead of the large static loading equipment, so it is very convenient to bring to anywhereand makes the testing procedure being more quickly. The builder who uses this instrumentto control the filling quality of the roadbed could test much more testing point than theplate loading test and makes the work more efficient.In order to research the working mechanism of the instrument, the author calculatedthe emulationai model of the instrument by using the leading Finite Element ProgramMsc-Dytran, analyzed the influence on the testing result K_d from the instrument parameters(the weigh of the hammer, the diaJneter of the loading p1ate, the rigid of the spring),provided the base of the instrument designing, and confirmed the test influence range ofthe soi1.The author tested lots of points at the Qin-Shen construction site. During the test, theauthr recorded the press and the displacemen of the loading plate all over the testprocedure and calculated out the dynamic rigidity coefficient K_d. Similarly a K₃₀ test hasbech done on the same site to compare with the dynamic rigidity coefficient K_d. Four kindsof K_d calculation method were used to discuss the relativity with the K₃₀. The author foundout the relativity between the dynamic rigidity coefficient K_d and K₃₀ on three kinds of soil(grade gravel, CF, CS). In conclusion the author confirmed that the dynamic rigiditycoefficient K_d has a good relativity to the K₃₀, and it can be used as a new index to evaluatethe qnglity of the filling in tallway roadbed.