Abstract: Firstly, based on the basic characteristic curves and revealed by the results of the soil dynamic tests, the rules of adjustable double-parabola constitutive curves of reverse unload after load process or reverse load after unload process in irregular load history are established, and function implementation and implement of A type and B type parabola are expounded for the characteristics of reverse load or unload curves sometimes change more flatly at first and then acutely. Secondly, by comparisons of 9 methods simulated results of soil test damping, the load and unload rules of double-parabola model accord with the test results, especially accord with the value of soil test damping, and they can be regarded as the simplification and practicality of generalized Masing rule. Because of the adjustment coefficient can be changed, the model has more powerful capability of simulation the shape of constitutive relationship curves. At last, using the borehole array records of Taiwan Lotung DHB field test, the nonlinear seismic response of DHB site are analyzed by equivalent linear method SHAKE91, LSSRLI-1, nonlinear method in time domain- DESRA-2, Pyke model, Non-Masing rule model ONE, implicit stress damping equivalent model, damping degradation coefficient model, Non-Masing rule model TWO and double-parabola constitutive model respectively. After compared all the synthesizing acceleration ground motions with the observation records, we found the PGA of double-parabola model are almost equal to the observation value, the comparative size relations of waveform, subsequence waveform are agree well with the records. As a result, the rationality of double-parabola constitutive model and the feasibility in practical engineering application are manifested.

Key words: double-parabola, constitutive relation model, soil test damping, comparisons of methods, engineering application