Total Runout Research Articles

Computer Study of Snow Avalanche Startup Dynamics

The startup dynamics of three wet snow avalanches in central Japan were evaluated by computer modeling the occurrences and comparing leading edge position-time data. Results were compared between three finite difference based computer codes, which were used to model the startup transients. Two of the computer codes use equations of uniform flow hydrodynamics, the third uses transient viscous fluid mechanics. The latter two codes also incorporate a material description of snow as a locking material. Results show a general increasing of frictional and/or viscous coefficients in the avalanche startup zones in order to match the kinematics of startup. Differences in results between the codes is attributed to the shape of the startup zones, whether convex or concave. The results indicate the magnitude of perturbation of startup on total avalanche runout time, which is likely to be negligible on long-duration avalanche occurrences.

Computer Study of Snow Avalanche Startup Dynamics

The startup dynamics of three wet snow avalanches in central Japan were evaluated by computer modeling the occurrences and comparing leading edge position-time data. Results were compared between three finite difference based computer codes, which were used to model the startup transients. Two of the computer codes use equations of uniform flow hydrodynamics, the third uses transient viscous fluid mechanics. The latter two codes also incorporate a material description of snow as a locking material. Results show a general increasing of frictional and/or viscous coefficients in the avalanche startup zones in order to match the kinematics of startup. Differences in results between the codes is attributed to the shape of the startup zones, whether convex or concave. The results indicate the magnitude of perturbation of startup on total avalanche runout time, which is likely to be negligible on long-duration avalanche occurrences.

A System for Mounting End Caps on Ice Specimens

AbstractThis short note describes the equipment and procedures we have developed to mount end caps on ice-core specimens. The system typically achieves end-plane parallelism within 0.5 μm/mm of specimen diameter (i.e. a total indicator run-out of 0.002 in for a 4.0 in diameter specimen). The essential elements of the system are a holder and an alignment fixture. The holder firmly grips the ice core about its circumference by the compression of two series of O–rings. The alignment fixture clamps the holder to align the ice core precisely with the end caps. To bond the ice to the end cap we form a layer of 0°C water on the end cap; the water freezes immediately upon contact with the ice and forms a strong intimate bond. To date, we have used this system to install phenolic end caps on 101.6 mm diameter cores and aluminum end caps on 76.2 mm diameter cores of saline ice. We obtained a somewhat better tolerance with the aluminum caps (0.33 μm/mm of end-cap diameter), due primarily to the geometric stability of that material under the prevailing conditions. These specimens have been successfully tested in uniaxial and triaxial compression, and we expect that with appropriate end caps the system will be suitable for preparing tension specimens as well.

THE OPTIMAL DIVISION OF A CONTAINER INTO N COMPARTMENTS BY CONVEX PROGRAMMING

SUMMARY This paper develops a method for computing the optimal division of a container into any number (N) of compartments when each compartment contains an item which is subjected to an independent demand over some time period. Each of the N compartments is filled at the beginning of the period and the objective is to minimise total runout cost during the demand period.