To protect the safety and comfort of road structures that make up roads, such as earth structures like embankments and cut earth and associated drainage facilities and culvert boxes for cross roads, we conduct surveys for damage and defects from various perspectives and make improvement proposals as necessary. We also carry out work related to road disaster prevention, such as investigating falling rocks from outside the road area and formulating an action plan for securing traffic as soon as possible in the event of a large-scale earthquake.
Examples of specific businesses are given below.
We visually inspect the heads of the ground anchors and pressure receiving plates installed as a measure against landslides on cut slopes to check whether the ground anchors and pressure receiving plates have the required performance and whether there are signs of landslides on the cut slopes. We are investigating the tension force acting on the ground anchors extracted as samples.
Existing anchors with short extra length of tendons had the problem of being unable to unload or adjust the load. This construction method is the first in the world to solve these problems, and is a renewal technology that enables unloading of overloaded anchors that exceed the allowable anchor force and load adjustment on the increasing side of anchors with a significant load drop. With this construction method, it is possible to recycle existing anchors with a sound tendon and reduce or eliminate the need for new additional anchors, thereby reducing the cost of measures required to ensure the stability of the slope surface.
To confirm the safety against falling rocks, we investigate the slopes outside the road area, targeting the cut sections and around the entrances of tunnels.
During the investigations, if we discover stones or rocks that may fall, the positions are recorded on maps and the impact on roads in the event of rockfall is evaluated.
In cases of earthquake damage to road embankments in plain areas, there are cases in which the ground beneath the embankment loses its strength and the embankment above it cannot maintain its stability. In such cases, we shift our focus to the sandy ground and are examine a method for evaluating stability against ground liquefaction during an earthquake by calculating the subsidence amount of the embankment road surface caused by loss in strength due to liquefaction using liquefaction flow analysis and comparing the result with susceptibility to liquefaction (PL value, etc.).