Rockfall Barriers Research Articles

A Combined Methodology for Landslide Risk Mitigation in Basilicata Region by Using LIDAR Technique and Rockfall Simulation

Rockfalls represent a significant geohazards along the SS18 road of Basilicata Region, Italy. The management of these rockfall hazards and the mitigation of the risk require innovative approaches and technologies. This paper discusses a hazard assessment strategy and risk mitigation for rockfalls in a section of SS118, along the coast of Maratea, using LIDAR technique and spatial modelling. Historical rockfall records were used to calibrate the physical characteristics of the rockfall processes. The results of the simulations were used to define the intervention actions and engineering strategy for the mitigation of the phenomena. Within two months, 260 linear meters of high-energy rockfall barriers for impact energies up to 3000 kJ were installed. After that, according to road authority, the SS18 road was opened in a safe condition. The results represent a valid cognitive support to choose the most appropriate technical solution for topography strengthening and an example of good practice for the cooperation between innovative technologies and field emergency management.

Nonlinear explicit analysis and study of the behaviour of a new ring-type brake energy dissipator by FEM and experimental comparison

The aim of this paper is to comprehensively analyse the performance of a new ring-type brake energy dissipator through the finite element method (FEM) (formulation and finite element approximation of contact in nonlinear mechanics) and experimental comparison. This new structural device is used as a system component in rockfall barriers and fences and it is composed of steel bearing ropes, bent pipes and aluminium compression sleeves. The bearing ropes are guided through pipes bent into double-loops and held by compression sleeves. These elements work as brake rings. In important events the brake rings contract and so dissipate residual energy out of the ring net, without damaging the ropes. The rope’s breaking load is not diminished by activation of the brake. The full understanding of this problem implies the simultaneous study of three nonlinearities: material nonlinearity (plastic behaviour) and failure criteria, large displacements (geometric nonlinearity) and friction-contact phenomena among brake ring components. The explicit dynamic analysis procedure is carried out by means of the implementation of an explicit integration rule together with the use of diagonal element mass matrices. The equations of motion for the brake ring are integrated using the explicit central difference integration rule. The presence of the contact phenomenon implies the existence of inequality constraints. The conditions for normal contact are λ ⩾ 0 , g ⩾ 0 and g λ = 0 , where λ is the normal traction component and g is the gap function for the contact surface pair. To include frictional conditions, let us assume that Coulomb’s law of friction holds pointwise on the different contact surfaces, μ being the dynamic coefficient of friction. Next, we define the non-dimensional variable τ by means of the expression τ = t / μ λ , where μ λ is the frictional resistance and t is the tangential traction component. In order to find the best brake performance, different dynamic friction coefficients corresponding to the pressures of the compression sleeves have been adopted and simulated numerically by FEM and then we have compared them with the results from full-scale experimental tests. Finally, the most important conclusions of this study are given.

Flexible Rockfall Barriers Subjected to Extreme Loads

Flexible rockfall barriers are proven protection systems to mitigate the hazard of rocks falling on people and infrastructure. To assure that such systems are able to dynamically stop falling rocks in reality, several guidelines with full-scale tests were introduced worldwide. These guidelines consider very standardized and repeatable load cases but cannot take possible extreme loads into account. Two examples of extreme loads were investigated, high-speed rockfalls where the impact velocity is well above 25 m/s as described in the testing guidelines, and a tree trunk strike with the same weight as a falling rock but with a much smaller impact area. Finally, an overview of the performance of flexible barrier subject to dynamic area loads, such as debris flow, shallow landslides or snow avalanches is given.

Choosing a rockfall barrier with the Precautionary Principle: a quantitative approach

The paper illustrates an approach for implementing the Precautionary Principle in risk management, exemplified by a procedure aimed at choosing the height of a rockfall barrier protecting a railway stretch. Risk is expressed by the frequency f of blocks hitting the railway—i.e. by the ratio between the number of blocks reaching the railway and the number of blocks falling from the slope—assessed through software simulation of the falling of the blocks. The height from which a block may fall is considered to be the main uncertainty factor in risk estimation, which translates into uncertainty as to the level of risk, as every simulation shows that more than one impact frequency is possible. Such uncertainty justifies the precautionary approach to the design of the barrier, and is represented mathematically by means of possibility and probability distribution functions. The distributions make it possible to express the degree of precaution related to a barrier as the level of confidence, in terms of necessity or probability measures—that can be placed on the fact that, because of the barrier, the impact frequency, although uncertain, will not exceed what is acceptable. It will be shown that the degree of precaution takes quite different values if possibility theory is used instead of probability theory. Finally some simple cost/benefit analyses, that explicitly and quantitatively consider the degree of precaution, are exemplified.

Interaction of flexible rockfall barriers with avalanches and snow pressure

Abstract Rockfall barriers are optimized to absorb high punctual impact energies. In mountain areas the barriers are also loaded by avalanches and snow pressure. Snowpack forces and dynamic avalanche pressures act over a much larger area and over longer time periods. Thus, if not properly designed, rockfall barriers can be damaged. In winter 2003–2006 we investigated the interaction of flexible rockfall barriers with avalanches and snow pressure on a study site in Fieberbrunn, Austria and in other areas. In several locations the barriers successfully stopped small wet snow avalanches. However, the main problem turned out to be the insufficient retention capacity during the whole winter and the structural behaviour. The weakest points are the retaining ropes and the post foundations. For an appropriate design of the barrier the main input factors determining snow pressure and avalanche pressure have to be assessed.

Corrosion behaviour of steel ropes for snow and rockfall barriers

During service, steel ropes can suffer from corrosion, which can reduce their mechanical properties. This degradation is particularly important in the case of structural ropes, or barriers, for snow and rockfall protection because it is not easy to detect any significant degradation over time due to the locations of these structures, which are often difficult to reach. Moreover, rockfall barriers are frequently used in marine environments to reduce the instability of rocks and cliffs, where corrosive attack by chlorides can be very dangerous. This study has characterised the effects on corrosion of the geometrical configurations of the strands and wires in the ropes, and the benefits of zinc and zinc alloy protective coatings on the wires for reducing the degradation of structural ropes. The aim of the research was to obtain information useful for the design of high durability barriers and the selection of an appropriate rope and coating. An approach based on an electrochemical testing has been compared with one based on classical tests involving the exposure of ropes in aggressive environments (salt spray, humidity chamber, etc.) in order to find an electrochemical method able to distinguish the performance of different materials as well as to monitor the corrosion degradation of barriers in the field.Using electrochemical techniques it was possible to quantify the corrosion rate and demonstrate the better behaviour of ropes coated with zinc–aluminum alloys in comparison with pure zinc. Moreover it was possible to evaluate the actual reactive area, and therefore the protective geometry effect when comparing two ropes with different geometries. This approach should be extended to further kinds of ropes in order to improve basic corrosion understanding of this important structural component.

Steel-net rockfall protection - experimental and numerical simulation

The design of todays state-of-the-art rockfall barriers is currently based on experience and time consuming experimentation. Advanced simulation models are now under development to reduce prototyping time and development costs and will also provide a better understanding of complex mechanical systems under impact. In order to develop the models, extensive field testing was carried out. The individual components of the barriers were dynamically tested on a specially designed field apparatus, High energy full-scale tests on instrumented multi-span systems were additionally performed. The newly developed finite element program simulating the barriers is based on an explicit time step algorithm combined with special-purpose elements with large deformations and nonlinear material behavior for the netand brake-rings. For the interaction of rock and elements it also considers contact and sliding effects as well as friction.

Investigation on current states of design for ring-nets rock-fall barrier

Investigation on current states of design for ring-nets rock-fall barrier

Development of Effective Rockfall Barriers

As a part of the construction of Interstate 70 through Glenwood Canyon, in Colorado, three new types of barriers for protection against rockfall were developed through a program of prototype testing, numerical simulation of rockfall events, and analysis of barrier response to impact by boulders. New barriers include a suspended pendulum system that attenuates the kinetic energy of falling boulders, a flexibly mounted fence of steel cables and mesh, and a free-standing mechanically stabilized earth wall. The capacity of rockfall barriers, stated as a limiting translational kinetic energy of falling boulders, ranges from 41 kJ (30,000 fts˙lb) for light fences to more than 1,400 kJ (1,000,000 fts˙lb) for mechanically stabilized earth walls. Earth walls can halt falling boulders that weigh as much as 13,700 kg (30,100 lb). The three barriers reported here are useful as options to ditches, berms, rigid fences, and rigid walls of rockfall protection for highways. This paper provides a summary of barriers develo...