Research results

Realization of a Recycling-Oriented Society
- Technology for Recycling of Asphalt Paving in Cold Snowy Regions -

Recycling of asphalt paving materials

Paving cracks in low-temperature conditionsl

Flexural strength test of asphalt paving materials in low-temperature conditions

Environmental conservation has become a major topic on an international level, and research has been conducted in a variety of fields to promote a recycling-oriented society. Road paving is included among such considerations, and asphalt paving materials have been recycled in Japan since 1980. In the cold, snowy region of Hokkaido, such recycling began in 1998. Previously recycled materials are expected to be recycled again in the future, and there is concern over the possibility of material quality deterioration as a result of repeating recycling.

Previous studies on the recycling of paving materials have focused on examining the durability of recycled asphalt in high-temperature conditions and chemical analysis of asphalt components. No research has been performed on their durability in low-temperature conditions that can cause paving to crack and lead to problems in cold snowy areas. Accordingly, the physical properties of asphalt paving materials in low-temperature conditions need to be clarified in order to enable their repeated recycling in such areas.

The current quality standards for asphalt recycling materials were determined from the results of tests on asphalt used in mainland Japan (Honshu) and other regions. However, the environments in which paving is laid and the characteristics of the materials used vary significantly in cold snowy areas such as Hokkaido, and the same quality standard values are not considered effective enough to prevent transverse cracking in low-temperature conditions.

The Road Maintenance Research Team, clarified the extent to which repeated recycling in cold snowy areas affects the state of recycled asphalt materials in low-temperature conditions and evaluated the suitability of the recycled asphalt materials currently used in cold snowy areas.

The results clarified that frequent recycling of paving under the current quality standards would reduce its strength, causing a tendency for brittleness or cracking. It was also found that these standards provided extremely strict conditions with recycling in cold snowy areas in mind. We therefore proposed new standard values for the levels of quality required to enable long-term ongoing recycling of asphalt paving materials in cold snowy areas.

(Contact: Road Maintenance Research Team, CERI)

Quickly and Safely Estimating the Shape of the Slip Plane of a Landslide!

Figure 1. Image of the Method

Photo 1. Landslide which was verified

Figure 2. Results of Calculation of Slip Plane

Characteristics of a landslide include cracks accompanying a level difference at the top of the landslide or cracks forming in roads or retaining walls. When such characteristics have appeared, it is vital to clarify the scale of the landslide as quickly as possible and take emergency measures such as counterweight embankments in order to prevent expansion of damage.
It is also necessary to clarify the slip plane underground, or in other words, to determine at what depth slipping occurs, in order to clarify the scale of a landslide. So generally holes with diameter of about 10cm are bored in the ground to investigate the state of the soil and rock underground and to make measurements in order to clarify at what depth the slip plane . But, it takes time to take these steps. It is also dangerous to work where a landslide is moving.
So a method of estimating the shape of the slip plane based on the direction and length of the movement of the ground surface of a landslide and a program to implement the method have been prepared. Figure 1 shows the image of this method.
The method, which is grounded on the supposition that the quantity of deformation of multiple landslide blocks, which move on the slip plane while an almost constant positional relationship is maintained between them inside the landslide ground, is smaller than the quantity of movement, is based on the concept that the track of the motion of measurement points on the ground surface are almost parallel to the shape of the slip plane vertically below it.
One example of the application of the method is introduced below. Photo 1 shows a view of the landslide studied. Moving piles installed at six points along the main survey line shown in Photo 1 measure how much the location of each one has moved. The measurement results are inputted to the program, and the calculation results are shown in Figure 2. The shape of the slip plane estimated by the calculation is similar to the shape of the slip plane hypothesized based on a later boring survey, etc.
At the present time, engineers must judge how to set lines dividing the blocks, but after the method has been employed by many engineers and the results of their use have been verified, we wish to improve the method making it easier to use.

(Contact:Landslide Research Team)