Characteristics of viscous debris flow in a drainage channel with an energy dissipation structure

A new type of drainage channel with an energy dissipation structure has been proposed based on previous engineering experiences and practical requirements for hazard mitigation in earthquakeaffected areas.Experimental studies were performed to determine the characteristics of viscous debris flow in a drainage channel of this type with a slope of 15%.The velocity and depth of the viscous debris flow were measured,processed,and subsequently used to characterize the viscous debris flow in the drainage channel.Observations of this experiment showed that the surface of the viscous debris flow in a smooth drainage channel was smoother than that of a similar debris flow passing through the energy dissipation section in a channel of the new type studied here.However,the flow patterns in the two types of channels were similar at other points.These experimental results show that the depth of the viscous debris flow downstream of the energy dissipation structure increased gradually with the length of the energy dissipation structure.In addition,in the smooth channel,the viscous debris-flow velocity downstream of the energy dissipation structure decreased gradually with the length of the energy dissipation structure.Furthermore,theviscous debris-flow depth and velocity were slightly affected by variations in the width of the energy dissipation structure when the channel slope was 15%.Finally,the energy dissipation ratio increased gradually as the length and width of the energy dissipation structure increased;the maximum energy dissipation ratio observed was 62.9%(where B = 0.6m and L/w = 6.0).

Engineering practice of seismic isolation and energy dissipation structures in China

The concepts of seismic isolation and energy dissipation structures emerged in the early 1970s.In China,the first seismic isolation structure was finished in 1993,and the first energy dissipation structure was built at about the same time.Up to 2007,China had more than 600 seismic isolation and about 100 energy dissipation building structures.In 2008,the huge Wenchuan earthquake hit the southwest of China,which triggered a bloom of new seismic isolation and energy dissipation structures.This paper presents the development history and representative applications of seismic isolation and energy dissipation structures in China,reviews the state-of-the-practice of Chinese design,and discusses the challenges in the future applications.Major findings are as follows:Basic design procedures are becoming standardized after more than ten years of experiences,which mainly involve determination of design earthquake forces,selection of ground motions,modeling and time-history analyses,and performance criteria.Nonlinear time-history analyses using multiple ground motions are the characteristic of the design of seismic isolation and energy dissipation structures.Regulations,standardization and quality control of devices,balance between performance and cost,comparison with real responses,and regular inspection are identified as the issues that should be improved to further promote the application of seismic isolation and energy dissipation structures in China.

Spatial relationship between energy dissipation and vortex tubes in channel flow

The spatial relationship between the energy dissipation slabs and the vortex tubes is investigated based on the direct numerical simulation（DNS） of the channel flow. The spatial distance between these two structures is found to be slightly greater than the vortex radius. Comparison of the core areas of the vortex tubes and the dissipation slabs gives a mean ratio of 0.16 for the mean swirling strength and that of 2.89 for the mean dissipation rate. These results verify that in the channel flow the slabs of intense dissipation and the vortex tubes do not coincide in space. Rather they appear in pairs offset with a mean separation of approximately 10η.