Rockfall protection is designed to control and/or prevent debris, rocks and/or avalanches from falling from slopes or banks alongside man-made construction such as municipal projects, highways, railways, waterways, utility plants and tourist sites. Either passive mitigation or active mitigation measures are employed in rockfall protection systems. Passive measures are used to hold the earth when previous steps have been taken to stabilize the earth along the area in question. Active or covering measures are utilized to prevent rocks from falling and the subsequent damage caused by the impact. The use of wire mesh and high energy absorption (HEA) panels are considered passive mitigation or intervention, while rockfall soil embankments are active measures.
Standard Types of Rockfall Protection
Active Mitigation utilizes the safety netting system (SNS) which is appropriate to cover a wide range of terrain. It maintains the lands original form allowing for its complexity and variation. These systems allow for the planting of trees, the growth of vegetation, a clear view of the land and environmental conservation. These systems work well in all areas because the view of the terrain undergoes barely noticeable alterations.
The Rockfall Protection Systems
• Hexagonal Mesh
• High Energy Absorption Panel
• Rock Soil Embankments
Hexagonal Mesh Rockfall Protection
Hexagonal mesh or wire netting can be used like a curtain, draped over the spalling rock and secured in the rock strata or used to create a catching wall that harmlessly traps falling debris as it reaches the escarpment’s base. This type of rockfall protection system needs vertical or horizontal cabling to secure the mesh to the surface and to the adjacent sheets of netting.
High Energy Absorption Panel Rockfall Protection
High energy absorption panel s are used under specific conditions. In situations where punctures might result from falling debris and the strain would be low, though the load could still be heavy. A case study cited the success of the Otira Gorge Site in New Zealand through the mountainous terrain of Arthur’s Pass. HEA panels were employed to secure the rock face on a 50-60 degree bluff. The high energy panel was strong enough to resist the impact of rocks descending at great speed. Its construction was nearly invincible to damage caused by cutting and puncturing.
Rock Soil Embankments- Rockfall Protection
Rock soil embankments are usually all-weather materials used as to insure settlement and stability of a steep incline. Durable granular material that is non-moisture density testable and coarse grain is used as fill. The material used can be selected from the immediate area or imported from afar. Upon selecting the fill material, the proper equipment must be used to properly compact it. Fine-grained sandstone and siltstone tend to be unstable materials resulting in excess long-term settlement, generating settlement problems over time. Granular all-weather materials tend to be the most easily compactable materials for embankment fill construction. The finished project should be graded based on stability, safety, strength and settlement.
Successful Rockfall Protection Systems
Along the Salem Karur Railway route in Tamil Nadu, India a High Energy Absorption Panel was installed with raised anchorage systems at the top and bottom for greater strength. An additional chain link mesh was added for surface protection. All this insured the panel would perform its job successfully.
In Spain, in the municipality of Buenavista del Norte on the northwest coast of Tenerife, Canary Islands a road runs through a mountainous area. It has high slopes of basaltic castings, slag and volcanic materials. Much of the slope is eroded by rain and wind and other material simply falls. As a result the road has experienced frequent road closures. It was determined that two rockfall barriers would be used to stabilize the area. Construction crews installed ring nets reinforced by hexagonal double twist wire mesh 459 foot long by 23 foot high formed barriers secured by posts, bracing cables and interception structures.
Rockfall protection serves to preserve man-made construction all over the world. It protects roadways, railways, utility sites and communities. These efforts enable the longevity of our handiwork and the preservation of our limited financial resources. Due to scientific discovery of how earth responds to outward pressures we have evolved to take full advantage of our surroundings. Rockfallprotectionisoneshiningexample of thatevolution.
