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Technology
Assessment & Research (TA&R) Program
| Project Number |
556 |
| Date of Summary |
March 9, 2007 |
| Subject |
Risk Assessment of
Submarine Slope Stability - Hydroplaning |
| Performing Activity |
Offshore Technology
Research Center |
| Principal Investigator |
Dr. Stephen Wright |
| Contracting Agency |
Minerals Management Service |
| Estimated Completion |
Completed March 2007 |
| Description |
Prior research on submarine slides performed by
OTRC has consisted of numerical and physical modeling and the
development of both empirical and numerical models to predict the
initiation and movement of slides. Research shows that under
certain conditions a moving slide mass can hydroplane on a layer
of water that becomes trapped between the moving slide mass and
the underlying soil. One of the most important aspects of
hydroplaning is the interaction between the moving slide mass and
surrounding fluid. Project 556 builds on research conducted under
Project Number 491, Phases I & II which focus on modeling the
interaction between a moving slide mass and surrounding fluid.
That modeling led to an improved understanding of the
characteristics of the fluid-slide mass interaction. In project 556, OTRC incorporated
the understanding of the fluid-mass interaction into a numerical
model that includes the moving and deforming soil slide mass. This
model is intended to aid in predicting the movement of submarine
slides, with emphasis on slides that travel large distances once
they are initiated. In particular the research seeks to develop a
numerical model for predicting the initiation of hydroplaning of a
slide mass and the subsequent motion of the mass once hydroplaning
is initiated. The numerical model developed in this project is applicable to subaqueous slides of any scale, and is
expected to determine if hydroplaning is likely to be
initiated as well as the magnitude of movements once
hydroplaning is initiated. The sliding process was
simulated based on the initial geometry of a slope failure, the
geology of the nearby seafloor, and the mechanical properties of
the slide material (including shear strength, stress-deformation
properties and unit weight). The model describes
(1) the variation of the velocity of the slide mass in time and
space, and (2) the eventual run out distance and geometry of the
slide mass. This information is
beneficial in judging the potential risk associated with
submarine slides. |
| Progress |
Hydroplaning is believed to be
one of the major reasons why some submarine slides travel large distances. To
study this, a “block” model was developed
to simulate the process of sliding. Research focused
on the verification and calibration of the block model using data from
laboratory experiments conducted by Mohrig, et al. (1998, 1999). Once
validated the block model was
applied to simulate the movement of actual slides reported in the
literature. After preliminary studies with the model it was modified to
allow the actual conditions of Mohrig’s experiments to be simulated
correctly. In the experiments, the soil mass was dumped from a soil tank at
the head of a sloping channel. The soil mass remaining in the soil tank
pushed the dumped mass down the channel. The original block model only
represented the soil mass that is already in motion down a slope or channel.
Thus, to simulate the experiments, an additional force was added to the end
of the block in the block model to simulate the thrust applied by the soil
behind the block. Mohrig et. al. (1998, 1999) also reported that the soil
mass in their experiments could be highly viscous. Accordingly, a strain
rate effect on soil resistance was added in the block model.
Research study completed in March 2007. |
| Reports |
|
AA (1559
KB; 140 pages) |
Risk Assessment of Submarine Slope Stability - Hydroplaning, Final
Report prepared by Stephen G. Wright and Hongrui Hu of the University of
Texas at Austin, February 2007. |
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