The dynamic rheological mechanics characteristic of soft rock soil is tested, the dynamic viscoelastic-plasticity rheological model and rheological equation are established; the expressions of dynamic rheological mechanics parameters are deduced. The dynamic rheological mechanics parameters of soft rock soil are tested under dynamic shear action, the influence characteristic is analyzed that the factors such as dynamic shear frequency、shear strain、rate of water content of soft rock soil and so on effect dynamic rheological mechanics parameters of soft rock soil. The research results have theoretical and actual signification for us to open out the influence disciplinarian of rheological mechanism characteristic and rheological parameters of soft rock soil under dynamic loading. It also has important academic signification for us to find out rheological dynamic mechanics of soft rock-soil bursting out geotechnical engineering disaster and geologic disaster.
Most of projects are established on soft rock-soil foundation in our country, such as industrial and civil buildings、road and bridge、geotechnical and underground engineering、irrigation works and hydropower project 、coastal defense and dike. The practical investigation and theoretical analysis indicate that the soft rock-soil has rheological characteristic, while under static load the soft rock-soil has slow rheological characteristic, not enough to cause serious deformation in a short time. but when under dynamic load, vehicles passing 、 various vibration caused by human activities, etc. the soft rock-soil will accelerate rheological action, and cause hazard of geotechnical Engineering, such as rock and soil slide instability 、settlement declination of foundations、crack and collapse of construction engineering 、embankment collapse[1 、2]. The dynamic loads become the inducing factors and the external power which accelerate rheological action of soft rock-soil and induce geotechnical engineering disaster and geological disaster. Therefore, it has more theoretical and practical significance to carry through fundamental researches in such respects as dynamic rheological properties of soft rock-soil、rheological parameter and its related factors、the rheological dynamic mechanism of geological disaster by combining with dynamic force that often occur in nature.  Soft rock-soil has certain viscosity and initial shear stress. When the exterior shear stress is less than initial shear stress, the soft rock-soil does not change, on the contrary, it began to plastic flow when the exterior shear stress is more than initial shear stress. Viscosity exists not only in elastic region before yielding, but also in plastic deformation region when the soft rock-soil is yield. The test indicates that soft rock-soil has viscoelastic properties under dynamic loading. It can be regarded as viscoelastic plasticity body. Flow deformation of the soft rock-soil does not occur before yielding, and behaves as the characteristic of viscoelasticity solid body; therefore, in the model the elastic element and viscous element with parallel connection are used to form the viscoelasticity solid model.