Rockfall

A rockfall happens when mountain rocks fall freely from a high level in to a lower level. Rockfalls often occur as a result of climate change which causes a change in the internal force pattern induced in rocks. Increase in the water pore pressure, corrosion of the soil around the rock pieces due to heavy rain, the process of freezing and melting, and deterioration of mechanical characteristics of the soil due to weathering are some of the changes directly or indirectly related to the climate effects. Of course the places which are mechanically active and have road or facilities being built in their vicinity have higher potential for rockfall and are more sensitive to climate effects. It is all because the induced stress by the construction of new structures increases the forces on the rock pieces.

 

Rockfall happens by multiple mechanisms. The most important ones are sliding, overturning and toppling, depending on the situation of terrain and joint set condition.

Unsuitable condition of rock mass, severity of joints, distance between the joints and the angle of joints are important factors in instability and falling of the rocks, that can increase the chance of rockfall due to climate change and construction.

When rockfall occurs in places with a human population it can lead to heavy and irrecoverable damages. Actually, the ability of controlling and safeguarding rockfall is the key point in saving the lives of many people and securing the infrastructures like mines and roads. Even in low volume, falling of the rocks can disrupt the performance of an infrastructure and cause heavy financial costs.

What is Rockfall and what is its application?

The need for saving peoples’ lives and preventing high damage costs to valuable facilities has raised the requirement for introducing products called Rockfall, to prevent the damages caused by falling of the rocks, avalanche, and landslide on residential and industrial areas, public centers, roadways, railways, and other infrastructures. These products can also be used to prevent the entrance of flood sediments into the aqueducts. Actually, the geotechnical engineers have found them as the most effective solution for reducing dangers caused by falling of the rocks. Other less efficient solutions are building tunnels, avalanche protection structures, and deviating structures above the places with the high potential for rockfall. It is worth mentioning that these options are highly expensive and not economically justifiable in comparison to Rockfalls.

According to the statistics about 45 percent of all the soil slope instabilities in the world are related the rockfalls, which shows the noticeable effect that Rockfall can have in reducing the risks.

Characteristics of Rockfall

Rockfalls are specifically designed to withstand the impact of large falling stones and avalanche. These products are made of weaving cables; these cables are themselves made of galvanized strands. The cables act totally flexible at the intersection point in the web which makes the Rockfall protection system highly flexible and capable of dissipating high level of energy. Besides absorbing impact energy, Rockfalls have to hold stone parts in them so that these parts won’t fall on lower parts.

The most important characteristics of these products are as follows:

  • Absorption of impact energy by elastic and plastic deformation
  • Easy and fast installation even in severe topographic situations due to high flexibility
  • Easy replacement of the damaged parts with new ones
  • Easy transportation due to proper packaging
  • High strength against corrosion due to deep galvanization
  • Not needing additional web because of the small size of the web meshes
  • Capability of away inspection which reduces the costs

Design of Rockfall

In order to design and choose suitable Rockfall for each project the probable location of slide surface and the volume of slide should be recognized and only then the appropriate Rockfall can be assigned.

The process of design and manufacturing of Rockfall should be in order to make it possible to stop large stones and landslides with high impact energy. Large scale falls moves large amounts of stones with vertical and horizontal displacement components of 1000 and 5000 meters. Their moving speed are usually about 25 meters per second on average, which by considering the high density of soil and stone produces large impact energy.