Web Magazine: Issuance of the Engineering Manual on External Displacement Measurement of Embankment Dams Using GPS
Figure 1 Engineering Manual on External
Displacement Measurement of
Embankment Dams Using GPS
Figure 2 Displacement monitoring of
an embankment dam using GPS
Photo 1 GPS sensor installed on
a moving-target on the
exterior of the dam
In December 2014, the Japan Society of Dam Engineers (JSDE) issued the Engineering Manual on External Displacement Measurement of Embankment Dams Using GPS（∗） (hereinafter referred to as "the Manual"), shown in Figure 1. The Manual was developed by the Measurement Management Study Subcommittee (Committee Chairman: Yoshikazu YAMAGUCHI, director of geological research, PWRI) established as part of JSDEs′ Investigation and Research Committee. As part of its research on dam safety management, the Dam and Appurtenant Structures Research Team studied GPS displacement measurement of dams, and obtained a great deal of information on methods for assessing the results of measurement, and selecting the location for installing a GPS device. Toshihide KOBORI (researcher of the Dam and Appurtenant Structures Research Team) participated in the Measurement Management Study Subcommittee as manager of the committee, and was deeply involved in the development of the Manual.
Currently, involving displacement measurement of the surface of the body of an embankment dam for dam safety management is based on a survey by personnel. In some cases, the survey-based measurement is complicated and involves high labor costs. Moreover, in emergency inspections after earthquakes or other disasters, it is often difficult to find workers to conduct such surveys in the disaster area; and displacement measurement of the surface of the dam body in such emergencies involves risk to the measurement personnel. Therefore, it is desirable to measure displacement of the surface of the body of an embankment dam safely and promptly.
In recent years, safety management employing GPS technology for exterior displacement measurement (as in Figure 2 and Photo 1) has been actively implemented as a means of addressing these issues. Proper installation and inspection of such GPS devices, assessment of the measurement results, and maintenance of the equipment, are each important, both in introducing GPS technology in such contexts, and in achieving the desired results in an efficient manner. At the moment, these activities are performed individually at each dam. As GPS-based displacement measurement systems are expected to be introduced into more dams in future, it will be necessary to apply GPS displacement measurement technology in an efficient and effective manner from a cost perspective.
To apply such technology to dams, and refine it as a tool to aid in safety management in an appropriate way, it is necessary to integrate technologies for the modification of GPS equipment, for the installation of such equipment, and for assessing measurement results with the accuracy required for dam safety assessment. To enable GPS technology to be smoothly introduced into dam safety management, and to optimize its effectiveness, the Manual identifies and discusses issues related to selecting measurement positions for GPS sensors, installment methods, and the operation and maintenance of the sensors; and outlines principles for addressing these issues in an appropriate way. The Manual is expected to promote the introduction of GPS technology into many dams, and lead to refinement and streamlining of dam safety management.
The Manual can be purchased from the website of the Japan Society of Dam Engineers. Please download the application form from the following URL, fill it out, and send it back:
(∗)A‘embankment dam’is the general term for an dam built with rock and sand.
(Contact: Concrete and Metallic Materials Research Team)
Development of new types of antifreeze pavement
Figure 1 Antifreeze pavement crushing
snow ice under vehicular traffic
Figure 2 Rubber particle-containing coarse
surface antifreeze pavement(iCESTOPPER)
Figure 3 Rubber chip-containing
antifreeze pavement(Ice Crush Pave)
Photo 1 Antifreeze effect(iCESTOPPER)
Photo 2 Antifreeze effect(Ice Crush Pave)
Different types of antifreeze pavement have been developed, to ensure the safety of road traffic in winter. However, specific measures to prevent road surfaces from freezing, assist in removing and compacting snow, and remove compacted snow from road surfaces, are typically only effective in specific locations and conditions, and have issues in terms of durability and duration of effectiveness.
The PWRI, along with Obayashi Road Corporation and Taisei Rotec Corporation, have conducted collaborative research and developed two new types of antifreeze pavement, which are effective and efficient in keeping road surfaces clear of snow and preventing surface freezing in winter.
The rubber particle-containing coarse surface antifreeze pavement (iCESTOPPER-R), developed by the PWRI and Obayashi Road Corp., is a coarse-surface crushed-stone mastic asphalt pavement with rubber particles mixed in. It can be sprayed and bonded to the surface of pavement, to prevent contact between the road surface and snow ice. The snow ice is crushed by the traffic load from vehicles thus preventing the road surface from freezing (Figure 2). iCESTOPPER-R has been applied to National Road 8 in Toyama Prefecture, National Road 18 in Niigata Prefecture, National Road 377 in Kagawa Prefecture, and other roads.
The rubber chip-containing antifreeze pavement (Ice Crush Pave), developed jointly by the PWRI, Taisei Rotec Corp., and Obayashi Road Corp., has improved deflection capability, achieved by mixing highly elastic rubber chips into the surface and body of pavement. The snow ice is crushed by the traffic load from vehicles and thus the road surface is prevented from freezing (Figure 3). Ice Crush Pave has been applied to National Road 18 in Niigata Prefecture, and other roads.
As shown in Photos 1 and 2, the conventional pavement is frozen, while the antifreeze pavement is unfrozen, in each case.
(Contact:Pavement Research Team)
"Guidelines for Earthworks in Winter in Snowy Cold Regions (Road Edition)(River Edition)" is Published
Photo 1 Deformation of an
embankment constructed in winter
Figure 1 Mechanism of frost
heave in an embankment
(click to enlarge)
Photo 2 Ice lenses in the soil
1.The State of Earthwork Construction in Hokkaido in Winter
In Hokkaido and other snowy cold regions, the construction of earthworks in winter necessitates construction under low outdoor temperatures, and this is particularly true for the embankment construction. The soil in such construction is at risk of freezing, frost-heave and mixing with snow. There is also the problem of shorter sunshine duration in that season. These severe conditions may affect the quality of embankments and other earth structures.
Some rivers require embankment works and sluice gate reconstruction during winter because this is when flood flow does not occur. Winter earthworks are also unavoidable on some roads, due to the limited construction period, the need for disaster-relief or the need for the earliest possible start of service. Additionally, earthworks need to be properly distributed throughout the year in order to stabilize employment.
2."Guidelines for Earthworks in Winter in Snowy Cold Regions (Road Edition)(River Edition)"
In light of the above, the Hokkaido Regional Development Bureau of the Ministry of Land, Infrastructure, Transport and Tourism; the Hokkaido Constructors Association; and the Civil Engineering Research Institute for Cold Region setup the Investigative Commission for the Appropriate Construction of Rivers and Roads in Winter in September 2010, for the purpose of examining appropriate methods of implementing earthworks in winter.
Focusing on earthworks, which face the greatest number of challenges, the commission collated a body of knowledge on earthworks in winter that onsite engineers and operators need to know. The suggested knowledge addresses frost heave* damage and other winter earthworks problems, and it proposes countermeasures. In February 2015, the commission completed the "Guidelines for Earthworks in Winter in Snowy Cold Regions (Road Edition)(River Edition)"(hereinafter:"the guidelines").
The guidelines consist of the following:
2 Factors that affect embankments in winter
3 Discussion of embankment construction in winter
6 Construction management
7 Examples of embankment construction in winter
3.Obtaining a Copy
The guidelines are downloadable from the official website of the Civil Engineering Research Institute for Cold Region (http://jiban.ceri.go.jp/). We hope they will be of help.
(∗)For details on frost heave, please refer to the PWRI Web Magazine Vol. 30: "Research Outline - Frost Heave at Roadside Slopes in Cold Snowy Regions".
(Contact:Geotechnical Research Team,Civil Engineering Research Institute for Cold Region)