The RockDelta Technical Notes bring high-level, dedicated articles on theory and practice of stone wool based vibration isolation, important stone wool material characteristics and in-situ/in-vitro functional performance of stone wool to track owners, track design engineers, acousticians and others with an interest in detailed knowledge related to stone wool based anti-vibration mats.
The RockDelta Technical Notes are available upon request. Please click here for further information.
Technical Note 1/2006
Experiences from Norway: Long-term Behaviour of Stone Wool in a Ballasted Track under Harsh Climatic Conditions.
Practical experiences with stone wool as high-efficiency, low damping, sheet type elastic bearing for high-performance track vibration isolation goes back a long time.
In 1978, with the knowledge, of course, that the climatic conditions would be rather extreme, the Norwegian National Railways (NSB) decided for stone wool based anti-vibration mats when isolating a 200 meters tunnel track section. The tunnel track section was located right beneath the Oslo Cathedral.
In 1996, as part of a preliminary investigation to determine the optimum method for vibration isolation for the “Gardermobanan” (railway connection between the Oslo city centre and the airport), NSB decided to conduct extensive research into the “total” behaviour of stone wool taking into account several key factors, including: total cost structure, vibration isolation efficiency, spring and damping characteristics, environmental friendliness and – not least – experiences gained from the 1978 Oslo Cathedral tunnel track.
This RockDelta Technical Note describes some of the major findings related to the 18 years of practical experiences from this tunnel track.
Technical Note 2/2006
Functional Performance and Dissolution Resistance of Stone Wool Fibres under Severe Environmental Conditions: Water, Frost, Acid Rain and Ion-exchanged Water.
At first visual encounter with high-resilience RockXolid® and RockBallast® anti-vibration mats, stone wool may appear somewhat fragile and delicate. However, in reality, nothing could be further away from the truth as stone wool fibres actually exhibit outstanding resistance to mechanical stress fatigue and resistance to influences from the environment in which the track is located. Concerning the latter, of special interest is the fact that this includes a uniquely high degree of resistance to dissolution and functional performance degradation when in contact with or even when fully submerged in a liquid for short or long periods of time.
From acid rain to pH neutral liquids stone wool fibres are durable to a degree that is hardly matched by any other sheet-type, full-contact elastic material for track vibration mitigation treatment.
This RockDelta Technical Note examines the dissolution resistance characteristics of stone wool fibres – as they are found for example in the RockXolid® and RockBallast® product lines – in water, acid rain and ion-exchanged water, and discusses the important practical, long term implications of the unsurpassed longevity stemming from this unique dissolution resistance. Last but not least, the resistance of stone wool fibres to sub-zero temperatures is examined and discussed.
Technical Note 3/2006
Dynamic Stiffness and Water: Resilience of Stone Wool and PUR Based Anti-vibration Mats After Being Submerged in Water.
It is well known that the passing of rolling stock with irregular wheel geometries on imperfect rail running surfaces generate dynamic forces that set the rail track structure and sub-soils into motion.
As a result, ground-borne vibrations will propagate from the rail tracks into the surroundings creating not only potential damage to the track but also, especially in urban areas, possibly causing everything from human discomfort and building damage to mal-function of delicate instruments located inside buildings.
An effective means by which to mitigate the propagation of ground-borne vibration is the use of resilient mats positioned deep in the track structure. The key function of this resilient element – regardless of the type of track – is that of introducing a known spring-damper into the construction, resulting in a mass-spring-damper system that significantly aids the attenuation of ground-borne vibrations.
Obviously, in a “real world” situation where the conditions may be far from an ideal and well-controlled laboratory environment, the effectiveness of the mass-spring-damper solution will depend heavily upon a number of factors related to the chosen resilient element, e.g. fatigue resistance, form stability, Poisson’s Ratio, dissolution resistance and working point on the load-deflection curve. However, perhaps even more important is the immediate – and often more dominate – threat to the prescribed level of Insertion Loss performance: the presence of water.
This Technical Note examines the influence from water on the most important parameter related to Insertion Loss: The Dynamic Stiffness Frequency Response Function (Dynamic Stiffness FRF). With a special focus on RockDelta stone wool and non-RockDelta polyurethane (PUR), Dynamic Stiffness FRF curves for samples based upon these two basic materials are shown and the results are discussed.
Technical Note 4/2006
Advanced Fire Protection with RockDelta Stone Wool: CEN Classification of RockXolid® and RockBallast®.
Within rail-based transport, fire safety is – for obvious reasons – a vitally important topic with special consequences related not least to tunnel tracks. Accordingly, for every build-ing component in the tunnel structure, accurate knowledge of the components resistance to fire and reaction to fire – not least, toxic smoke generation – is of the utmost importance.
A new EU fire classification system replaced old national systems by the year 2001. This affected all decision-makers in the building industry and all building users – and provided for a modern, elaborate and precise means of determining whether a material fuels a fire or provides resistance to the fire.
This new fire classification system consists of seven categories as follows: A1, A2, B, C, D, E and F. RockDelta stone wool based track anti-vibration mats do not only exhibit out-standing functional performance under even the most extreme climatic conditions, but also, stone wool comes with inherent and unique fire safety features as evidenced by the fact that all RockDelta stone wool based products fall into Euroclass A2 (s1, d0). RockDelta stone wool thus helps to ensure an effective fire safety with enhanced protection against loss of life, structural damage and financial losses.
This Technical Note looks at the details related to RockDelta stone wool and the new EU fire classification based upon EN 13823 and EN 13501-1.
