SOME UNRESOLVED PROBLEMS IN EMBANKMENT DAM SAFETY
EVALUATION AND RISK MITIGATION
Although not directly focused on ground improvement technologies, there are
several aspects of embankment dam seismic safety evaluations that impact mitigation
strategies and the choice and implementation of ground improvement methods for any
project. These include:
􀂃 Assessing the liquefaction potential of soils with cobbles and gravel
􀂃 Assessing the liquefaction potential of silty soils
􀂃 Assessing the post-liquefaction residual strength
􀂃 Interpreting the results of a risk analysis
􀂃 Deciding the acceptable level of risk
􀂃 Selecting and implementing, through the choice of representative properties
and parameters, the appropriate constitutive model for liquefaction and
dynamic deformation analyses
􀂃 Assessing the reliability and accuracy of the results of dynamic deformation
analyses
􀂃 Assessing and controlling conservatism
􀂃 Assessing compliance with specifications
CONCLUDING COMMENTS
Dam stability during and after an earthquake is a critical life safety issue.
Although the basic concepts and approaches to soil stabilization and ground
improvement – densification, drainage, cementation, reinforcement, removal and
replacement – are very old, new ways to implement them for mitigation of
liquefaction risk to embankment dams continue to be developed. As a result, many
strategies and methods for improving the ground at existing dams are possible.
Different ground improvement methods are likely to be the most suitable for different
soils, different purposes, and different site and project constraints. Optimal designs
may justify use of more than a single method of ground treatment for a project.
Whatever the methods chosen, success is largely dependent on accurate
characterization of the existing embankment and subsurface conditions, and this
characterization may be the most challenging part of a project.
Predictions of liquefaction and post-liquefaction deformations should be based on
realistic (unfactored) loads and best estimates of average soil properties. More
conservative estimates of loading conditions and properties should be used when
predicting the probable deformations and displacements after ground improvement.
Full-scale field tests yield the most reliable verification that the needed ground
improvement can be obtained and that the design is feasible. Such tests should be a
required part of all major projects. Once feasibility has been established, a QC/QA
program should be designed that verifies the most critical aspects of the work.
Evaluating the results of the QA/QC testing may be challenging.
Soil improvement will continue to play an important role in the mitigation of seismic
risk to existing dams. Current trends and recent experiences support the “simpler is
better” approach to ground improvement designs.
。。。哥哥姐姐们，这论文翻译好是要交给导师的，直接用软件翻译出来的根本就读不通啊！~~o(>_<)o ~~
|
