There are various measures to prevent a landslide disasters, because landslides occur by various combined causes such as topographic and geological features, geological structures and groundwater. These measures have two types called structural measures by building of countermeasure equipment and nonstructural measure by establishment of early warning system. The structural measures also have two types called control works and restraining works, and the both works are combined to get efficient effects.

As a landslide control work in Yui, we have been providing drainage wells and tunnels, carrying out horizontal boring, and providing caisson piles to stop landslide movements directly.

In order to remove deep groundwater, 23 drainage wells (about 17 m to 61 m in length, and 3.5 m in diameter) were provided.

Horizontal boring (about 80 meters long) is being carried out in 21 places so as to remove groundwater that is relatively close to the ground.

In Yui, 61 caisson piles (about 37 m to 88 m in length, and 5.0 m or 6.5 m in diameter), which stop directly the movement of landslide with the help of resistance force of structures, are being installed.

A drainage tunnel (768 meters in length at Yamanaka and 712 meters in length at Okubo) is being constructed in the solid strata below the slip surface. The tunnel will remove deep groundwater through pipes running from the tunnel.