TS-LV Snow Net

Area of Application

Snow nets are static defense structures installed on steep slopes to prevent the initiation of avalanches. They are most often used for protecting urbanized areas and linear infrastructure such as roads, pipelines and other utility corridors that pass through mountainous terrain. Snow nets are similar to larger steel structures such as snow bridges but are more cost effective for snow depths up to 4.5 m and have a smaller constructive and aesthetic impact.

Net Position

The nets are supported by a post and bearing rope structure, with the net sprung between the post head and lower bearing rope located upslope of the system. Downslope retaining ropes lock the post into position. Typical post spacing is approximately every 4 m. Fence rows are installed in series, blanketing the initiation zone. Dimensioning of the system, including fence row spacing is dictated by design methods according to the Swiss or Austrian guidelines.

Snow Retention

During the winter, the net fills with snow as it accumulates on the slope. As the net deforms, the load is transferred to the post and bearing ropes system and led into the ground. When the snow begins to melt, the structure relaxes and returns to its original state.

Upslope Anchorage

The lower bearing rope is led through a series of anchors on the upslope side of the system. A variety of solutions exist for these anchors including wire rope anchors, wire pack anchors, and systems using standard rock or soil anchors.

Lateral Anchorage

To maximize the efficiency of the system, triangular nets are installed at the lateral anchorage points to help capture as much snow as possible. All connections are made using shackles and thimbles to ensure a technically correct linkage and for ease of maintenance.

Base Plate

There is a variety of base plate configurations available. The solution uses a single tension anchor on the upslope side of the plate. The same plate can also be used for a “floating foundation” where no anchor is installed and instead retaining ropes are led from the plate to the upslope anchors used for securing the lower bearing ropes.

Post Head and Foot

The post head is designed to allow the deflection of the bearing rope while at the same time locking it into position using U-bolts. The connection between the post and base plate is with a ball-and-socket coupling.

Installation Packages

Snow net systems are designed with ease of installation in mind. Since installation sites are normally difficult to access, net and post packages are prepared at a lay-down site and delivered by helicopter. By preparing the packages in this way it eliminates the need for heavy machinery as the system can be installed by hand.

Classification
ModelTS-LV Snow Net
StyleHinged
Design Pressure
[kN/m2(lbf/ft2)]
up to 150
(3133)
Available Heights
[m (ft)]
up to 4.5
(14.8)
VerificationAnalytical
(site-to-site)
Primary Net
ModelOmega-Net 6.0/135Omega-Net 7.5/135
TypeSteel Wire CableSteel Wire Cable
Rope Diameter
[mm (inch)]
6.0
(0.24)
7.5
(0.30)
Rope Construction1 x 7 Spiral1 x 7 Spiral
Single Wire Diameter
[mm (inch)]
2.0
(0.08)
2.5
(0.10)
Corrosion ProtectionZn/ZnAl (Class A)Zn/ZnAl (Class A)
Mesh Size
[mm (inch)]
135 x 135
(5.3 x 5.3)
135 x 135
(5.3 x 5.3)
Unit Weight
[kg/m2(lb/ft2)]
3.6
(0.73)
5.6
(1.15)
Mesh Tensile Strength
calculated [kN/m (lbf/ft)]
246
(16,856)
386
(26,449)
Connection to Main RopesThreadedThreaded
Connection to Adjacent Panel5/16" Shackle3/8" Shackle
Omega-Net

The primary net material used in Trumer systems is called the Omega-Net. It is a steel cable net made from spiral rope that has thick individual wires to resist abrasion. The strands of rope are pre-bent into arcs resembling an omega shape and then woven together to make the net. This process yields an extremely strong net with high flexibility and energy absorption characteristics.

Bearing Ropes
Quantity
per fence segment
2
Max. Rope Diameter
[mm (inch)]
24
(0.945)
Corrosion ProtectionZn or ZnAl (Class A or B)
Brake Element
per rope
n/a
Brake Element Typen/a
Retaining Ropes
Quantity
per post
2
Max. Rope Diameter
[mm (inch)]
24
(0.945)
Corrosion ProtectionZn or ZnAl (Class A or B)
Brake Element
per rope
n/a
Brake Element Typen/a
Support Structure
Post TypeHEA/HEB
Post-Base Connection Hinged
Integrated LadderRungs every 0.5 m (19")
Rope GuidesIntegrated
Base Plate ConnectionBall and Socket
Anchors
per base plate
1
Post Base Support
Base Plate Layout
Net Seams

Lateral anchorage can be directly to a steep slope (e.g. gully embankments, as shown) or similar to a standard rockfall catchment fence. This allows the system to be used for protection against both confined or unconfined flows.

Typical Cross Section
Post Heads
Typical Layout (Front View)

NOTE: All data is taken from an example of an existing project. Every avalanche structure is custom designed for a specific site and loading conditions and so the exact details of the system will very from site to site. This is an important aspect of avalanche mitigation since standardized (e.g. CE marked systems) cannot address site specific requirements.

Top of Page