STABILITY OF RUBBLE-MOUND BREAKWATER MP JETTY TOES; 

 SURVEY OF FIELD EXPERIENCE 



PART I: INTRODUCTION 

 Background 



1. Failure of rubble-mound breakwater and jetty toes is a problem whose 

 solution has plagued the majority of the US Army Corps of Engineers (Corps) 

 divisions and districts responsible for designing, constructing, and main- 

 taining these structures. Instability of a rubble-mound structure's toe 

 directly impacts on the primary armor stability and overall performance of a 

 structure. In most instances, instability (failure) of a structure's toe does 

 not become evident until it has resulted in damage to the primary armor which 

 has progressed up to or above the still-water level (swl) . This observable 

 damage can range from a minor slumping or reorientation of a few armor units 

 around the swl to the total disappearance of large numbers of armor units. 

 Left unattended, this type of damage could propagate upslope at a rate depen- 

 dent upon incident wave conditions and severity of the toe and lower slope 

 armor damage. In many cases, it will result in either localized or widespread 

 failure of the structure. 



2. No guidance presently exists for the preparation of adequate repair 

 and/or rehabilitation designs for damaged or failed rubble-mound structure 

 toes. A concentrated effort to better understand the various types of toe 

 stability problems and to develop and document effective repair methods is 

 urgently needed. Through the development of sound design guidance, the need 

 for frequent repair work will be minimized which will result in substantial 

 dollar savings. 



Authority, Purpose, and Approach 



3. Under the Repair, Evaluation, Maintenance, and Rehabilitation (REMR) 

 Research Program, the US Army Engineer Waterways Experiment Station's (WES's) 

 Coastal Engineering Research Center (CERC) has been authorized and funded to 



