High Joule Net (high energy absorption type rock fall prevention fence)
The High Joule Net is a high energy absorption type rock fall prevention fence construction method developed focusing on the following three characteristics:
- 1. Capable of absorbing predefined rock fall energy with support intervals of 5 m.
- 2. Capable of absorbing predefined rock fall energy with an effective fence height complying with domestic standards.
- 3. Can be repaired locally such that it retains the predefined functionality.
High Joule Net technology is employed extensively not only in Japan but around the world.
High Joule Net applies cable nets where a single wire rope is shaped into a lattice grid using a special procedure and each lattice point of the wire grid is secured with a clip fastener.
The brake elements (shock absorbing component) reliably absorb substantial rock fall energy.Performance of 250kJ up to 3000kJ has been certified in tests conducted at WSL in Switzerland (Swiss Federal Institute for Forest, Snow and Landscape Research).
The length of the anchors is calculated based on experiment data conforming to ground conditions.
Even after catching falling rock, full functionality can be restored by simple repairs on the spot.There is no need to replace a damaged net entirely.
Fence height and post interval can be selected depending on the rock fall conditions.
The fixing part of the posts is a pin structure, so the overall flexible structure can sustain the system by shearing of the pin bolt even when a support is directly impacted by falling rock.
There is no need to build an extensive foundation on the slope face.Tree cutting can also be kept to minimum, so the net can be installed without changing the current state of the slope, blending in with the surroundings.
Various types are available depending on rock fall energy.
Conventional standby type rock fall prevention fences have a maximum energy absorption capability of about 100kJ. For higher energy levels, rock fall barriers (concrete continuous retaining walls) are used. However, High Joule Nets have the following energy absorption:
|Energy Absorption capacity (kJ)||Type||Effective fence height (H)||Net dimensions|
|250||HJN-250||3.0 m to 4.0 m||300 x 300 x (9/10)|
|500||HJN-500||3.0 m to 5.0 m||200 x 200 x (9/10)|
|1000||HJN-1000||3.0 m to 6.0 m||200 x 200 x (9/10)|
|1500||HJN-1500||3.0 m to 6.0 m||150 x 150 x (9/10)|
|2000||HJN-2000||4.0 m to 7.0 m||140 x 140 x (10/12)|
|3000||HJN-3000||4.0 m to 7.0 m||140 x 140 x (10/12)|
Energy absorption system
The system’s flexible structure features a shock-absorbing mechanism consisting of a special brake element positioned between anchors and cables, or between cables themselves, which allows the system to absorb the energy from large-scale rock falls by enveloping falling rocks.
- Cable net
- Brake element
- Redundant parallel cables
- Support base plate
- Support head