Protect the Dam!
: Real-time management of the embankment dams using GPS
 Exterior deformation measurement using GPS of Embankment dams |
 GPS sensor installed on survey target foundation |
 Backfill type GPS sensor installed a dam crest manhole |
Among measurements now performed for safety management of embankment dams, measurements of behaviors that indicate the overall state of a dam are most important. Exterior deformation of an embankment dam is measured by forming a grid of appropriately spaced measurement lines on the crest and slopes of the dam and establishing measurement use targets at each grid intersection point, to measure the exterior deformation by surveying the quantity of displacement in the horizontal and vertical directions.
However, by using the above method, rapidly responding after an earthquake or in other emergencies is difficult.
The Dam Structure Research Team of PWRI is considering introducing Global Positioning System (GPS) -based embankment dam exterior deformation measurement as a technique to solve these challenges.
The system used for this research was a compact, lightweight, and low cost GPS measurement device newly developed for the measurement in geotechnical engineering field and a monitoring center established based on the Internet. the GPS measurement system used for this research can measure exterior deformation of embankment dams in nearly real time with precision that is equal to or superior to conventional methods.
The methods of GPS-based embankment dam exterior deformation measurement, which are currently being researched, are as follows.
(1) GPS sensor installed on survey target foundation
A GPS sensor is installed on survey target foundation to measure the slope of the embankment dam body. Installation on survey target foundations permits cross-checking of the GPS measurement results with the conventional survey results.
(2) Development of backfill type GPS sensor
(Backfill type GPS sensor installed a dam crest manhole)
A backfill type GPS sensor was developed so that GPS sensors can be installed inside dam crest manholes. Even when a backfill type GPS sensor is installed inside a manhole on an embankment dam crest, it provides measurement precision after error correction in the vertical direction that is equal to that obtained if it were installed outside the manhole, because the steel cover of the manhole is replaced with one made of FRP (Fiber Reinforced Plastic) that is easily penetrated by radio waves.
The dam structure team proposes a scenario for replacing the conventional measuring methods for exterior deformation of embankment dams: either with an exclusively GPS based system or with a combined system with GPS as the principal method.
(Contact: Dam Structure Research Team)
Protect the Bridge during Extreme Earthquake!
: Development of Technologies for Quick Detection and Rapid Repair of Damaged Bridges
 Quick earthquake damage detection system |
 Earthquake damage of Reinforced concrete bridge pier |
 Repaired by quick drying mortor |
 Carbon fiber sheet jacketing with quick drying materials |
Structures such as roads and bridges, which are fundamental infrastructure facility that supports daily life, are designed and constructed considering the effects of big earthquakes that would potentially occur in the future. However, it is still difficult to predict the intensity of the shaking and the effects on structures with current technologies. In addition, structures that were constructed in old age and have not yet been retrofitted are likely to have insufficient seismic performance and thus, it would not be easy to prevent damage during an extreme earthquake. For this reason, it is important to prepare for damage that may occur due to earthquakes.
When an extreme earthquake occurs, roads and bridges have an important
role in emergency response such as rescue and evacuation of the affected
people and transportation of the emergency equipment and materials. For
these emergency responses, it is essential to evaluate the structural safety
and serviceability of such structures immediately after the event, and
to conduct repair works as soon as possible if the structural damage affects
the performance of the structures. This study features technological development
related to detection of bridge damage caused by an earthquake and the rapid
repair of the damaged bridge column.
To assist the emergency response of road administrators, a "quick earthquake damage detection system" has been proposed. This is a system intended to be used by road administrators during an emergency patrol after the big event. The main components of the system are an intelligent sensor unit and a personal computer. The intelligent sensor unit detects and evaluates the damage using change of dynamic response properties of a bridge column. The results are wirelessly transmitted from the sensor unit to the personal computer that indicates the results. This system enables road administrators to gather information on the damage and safety of structures in a running patrol car during an emergency patrol. The accuracy of this system has been verified by results from shake table tests of reinforced concrete bridge column models.
When considerable damage is detected, repair work is needed. This study also proposes a method that can complete repair works, which needs several days by means of a conventional method, within a day by taking advantage of
· quick-drying materials and
· simple repair devices
The effectiveness of the proposed method was verified through a series of shake table tests of reinforced concrete bridge column models.
Further studies are needed to improve the accuracy of the quick earthquake damage detection sensor and develop more rapid and efficient repair technology for application of actual bridges.
(Contact: Earthquake Engineering Research Team)