Classifications

• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D31/00—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution
  • E02D31/08—Protective arrangements for foundations or foundation structures; Ground foundation measures for protecting the soil or the subsoil water, e.g. preventing or counteracting oil pollution against transmission of vibrations or movements in the foundation soil

Definitions

• the object of the present finding is an anti-vibration system for insulating a receiver from the vibrations emitted by a source and which are propagated in the ground.
• the vibrations which travel in the ground are propagated both inside the medium in the form of compression waves and shear waves, and on the surface of the same in the form of compression waves, shear waves and above all in the form of Rayleigh waves.
• Vibration removal systems are also known, positioned between the emitting source and the receiver. These are based on the known principle according to which a vibrational wave upon meeting a barrier is partly reflected and partly transmitted beyond the barrier itself. There is total reflection and zero transmission when there is a maximum difference of rigidity between the barrier and the medium from which the vibrations arise. This signifies that an ideal barrier would be that composed of an open trench or by an extremely rigid medium.
• the open trench solution is not feasible for most applications, since it creates conditions of instability in the long term both for the walls of the excavation and for the ground adjacent to the trench.
• the finding, object of the present invention is to provide a solution to the technical problem of vibration insulation which is at the same time both effective and economically sustainable.
• the finding, object of the present invention is therefore an anti-vibration system according to the characteristics specified in claim 1, whose installation process is specified in claim 12. More in particular, the system is based on the fact that it interposes between the vibration source and the external receivers, in a ground excavation, a barrier consisting of a panel of suitable shape in order create an air interspace which is impermeable to the fluids present in the ground, such as water, and remains impermeable over time.
• Fig. 1 schematises an application example of the anti- vibration system in the railway field
• Fig. 2 is an axonometric view of a slat according to the invention.
• Fig. 3 is a section of the slat of Fig. 2;
• Fig. 4 is a panel, as a result of the assembly of several slats
• Fig. 5 is a detail which illustrates a possible connection between two adjacent slats
• • Fig. 6 is a cross section of the single slat
• Fig. 7 illustrates an alternative embodiment of the liquid- resistant/waterproofing system of the panel of Fig. 4, with a detail (Fig. 7a) and overall (Fig. 7b) view;
• Fig. 8 schematises an embodiment of the anti- vibration system in case of rocky terrain.
• the anti-vibration system according to the invention can be applied in order to actively insulate any type of source that interacts with the ground or in order to passively insulate the potential receivers reachable by the vibrations.
• a receiver building or plant to be protected from the vibrations which are propagated through the ground is indicated with 1
• 2 is the source which generates vibrations, according to a non-limiting example two trains
• 3 is a schematisation of the vibrations that are propagated on the ground surface, essentially composed of Rayleigh surface waves
• 4 is the flat countryside
• 5 generally represents the anti-vibration system according to the invention
• 6 is the temporary excavation subsequently filled with the same excavated earth, making up part of the manufacturing process of the anti- vibration system.
• a slat which represents the modular element of the system
• 8 and 9 are respectively the upper and lower portions of the aforesaid slat made impermeable to liquids
• 10 is the liquid-resistant/waterproofing foam (or equivalent device)
• 11 is the stiffening separator of the slat
• 12 indicates a connection example between adjacent slats.
• the finding consists of the installation, in the ground, of a barrier 5 with an air interspace made impermeable to possible liquids present in the ground, positioned vertically or horizontally according to the system of vibrations to be intercepted (undulatory, sussultatory, etc.) made by means of several panels 13 adjacent to each other.
• Each panel 13 is composed of elementary units called slats 7, which have a limited thickness and are formed by two flat, thin and parallel faces of any material, for example plastic, cement or metal, connected with each other through transverse stiffening separators 11 of suitable section and placed at an appropriate interaxis.
• liquid-resistant/waterproofing foam 10 or equivalent device is inserted in the upper 8 and lower 9 portions of the single slat, for a limited height.
• the liquid- resistant/waterproofing foam has the functioning of blocking the infiltrations of water or another liquid inside the interspace, a drawback which would increase the equivalent mass density of the barrier and reduce its effectiveness.
• the installation process of the anti-vibration system comprises the following phases: excavation of a trench at an appropriate distance from the vibrating source and at an appropriate depth; insertion of a barrier constituted by the assembly of a plurality of panels; filling the trench with soil or another appropriate material.
• the panel has a width of 2.3 m - 2.4 m, a thickness of about 4 cm and an appropriately sized depth H; the panel is composed of several 20 cm - width slats, held together by taping carried out with 1 m pitch along the depth of the panel.
• the panel is made impermeable to the fluids due to a U-shaped plastic material closure system 14 placed at the two ends, upper and lower; such U-shaped closure system is integrally fixed to the panel by pasting or another suitable system.
• liquid resistance/waterproofing is provided at possible holes, made for binding the panel to a moving system, by means of pasting small plastic material cylinders inside the 4 holes.
• the anti-vibration system by using normal or plastic concrete as trench filling, rather than excavated soil;
• the plastic cement is composed of a mixture of cement, bentonite and water, which is characterised by a specific weight equal to about 1200 kg/me.
• Such expedient is optional and can serve to avoid possible secondary consolidation creep of the soil used for the filling; in reality, such circumstance rarely occurs, only in fact in the presence of soils with particular volume expansion tendencies.
• the anti-vibration system can be made along the designed alignment, according to a "section" procedure and by using normal or plastic cement for the filling of the trenches: a trench is excavated which is 0.6m - 0.8m wide, 2.5m long and H depth, according to appropriate sizing, the panel is inserted and the trench refilled by casting the cement on both sides of the panel. Once the casting is executed, another section of anti- vibration system is made of 2.5 m length, not adjacent to the just-executed section, but leaving 2.5 m of ground free; one then proceeds in an alternating manner. Subsequently, following the setting of the plastic cement, one returns to complete the barrier in the sections of ground left free between the already made sections.
• 4 metal guides can be used, vertically arranged on the sides of the panel, 2 guides for each side; the guides are connected by another horizontal guide.
• the system of 4 vertical guides plus horizontal guide serves to move the panel during the insertion inside the trench and to keep it in centred position inside the trench.
• the guides are immediately recovered after the filling of the trench with the plastic cement.
• the 4 guides are connected with the panel by means of 4 holes placed at the 4 corners of the panel.
• the use of the anti- vibration system, object of the present invention offers the following advantages: •
• the anti-vibration system with cell barriers can be carried out at any time during the useful life of the railway line, even during operation, without having to interrupt the transit of the trains;
• Such system acts as a low-pass filter, attenuating the vibrations above a certain filter frequency, without amplifying any frequency of the train source spectrum; there is therefore no risk of resonance phenomena and/or amplifications of particular frequencies;
• the barriers ensure a lifetime equal to at least the useful lifetime of the works.
• the vibrational impact generated by a moving train is described below on a potential building situated near the railway line.
• such conditions include vibrational impact due to trams, underground trains, vibrating machines of an industrial plant, and generally all those situations which cause vibrations that are propagated through the ground.
• the vertical barrier is composed of a PVC insulating element of about 4 cm thickness, inserted in the ground through an appropriately supported excavation for a depth and a linear extension which depend on various factors: dynamic characteristics of the ground through which the surface vibrations are propagated (essentially Rayleigh waves); dynamic, geometric (length) and velocity characteristics of the train source; dynamic and geometric characteristics of the receiver (building); position of the receiver with respect to the source; maximum levels of vibrational disturbance permitted by law.
• the transfer functions were calculated at the receiver on the basis of experimental tests, in order to carry out a more precise forecast of the vibrational impact of the moving trains on the receiver.
• For the characterisation of the train source reference was made to a design spectrum based on experimental investigations conducted on several train lines.
• the forecast model of the vibrational impact is a complex transfer function, which resulted from the sum of different transfer functions, representative of the different aspects and/or phenomena of the model: a) Dynamic characterisation of the train source; b) Vibration propagation in the ground; c) Vibration propagation in the "ground/foundation” system; d) Vibration propagation between the floors of the building; e) Effects of the mitigation system.
• L 0 reference acceleration spectrum of the source
• Ai amplification created by wheel-rail interface alteration
• a 2 transfer function of the ground
• a 3 transfer function of the "ground-foundations" system
• a 4 transfer function inside the building
• a 5 amplification at the natural frequency of the building (for precautionary reasons assumed to be equal to 5 dB/floor at
• a 6 correction which takes into account the different actual velocity of the train in the investigated section with respect to the maximum running speed
• a 7 beneficial effects of the mitigation system, object of the patent.
• the reference acceleration spectrum of the vibrational source was determined on the basis of: • typology, frequency and velocity of the trains moving on the line
• the MASW seismic tests Multichannel Analysis of Surface Waves
• the MASW tests are specific geotechnical investigations of dynamic characterisation of the soils, which permit determining various aspects of the wave propagation in the soils:
• the MASW test active on site consists of:
• the weighted acceleration was calculated and the corresponding vibrational level was calculated at the different distances from the source. Knowing the vibrational level at the different distances, the transfer functions were calculated of the ground in the various investigated sites.
• the transfer functions regarding the propagation of the vibrations from the ground to the receiver and inside the receiver were determined through regression analyses conducted on the average differential spectra measured in the field between a fixed position and a movable position.
• the fixed position was found near the source and the movable position on the ground at various distances from the source.
• the fixed position was situated near the receiver and the movable position at different positions inside the receiver.
• the frequency range considered is in the range of 1 - 80 Hz.
• the movement of the train generates a field of vibrations upon contact between the wheels of the train and the rails of the line that is propagated in the ground, both inside and through the surface, towards the receiver (building).
• the waves which are propagated inside the ground unlike the Rayleigh waves which travel on the surface, are characterised by a lesser attenuation with distance and thus potentially harm the building.
• a 7 representative of the mitigation effects of the anti-vibration system, does not appear.
• the applied anti-vibration system is composed of cell barriers inserted in the ground, in a position comprised between the railway line (source) and the receivers.
• the fundamental aspects in the sizing of the anti-vibration system with cell barriers are reported below:
• the impedance ratio the impedance of a material is equal to the product between mass density and shear wave velocity in the material itself
• the impedance contrast between cell barrier and soil the more effective the mitigation operated by the system: the overall performance of the anti-vibration system therefore depends on the dynamic characteristics (shear wave velocity, mass density and damping) of the material forming the barrier- system and the dynamic characteristics of the soil;
• the height of the anti-vibration system affects the filter frequency of the system itself, above which the barrier- system attenuates the vibratory intensity.
• the attenuation size depends on the dynamic characteristics of the material composing the barrier-system.
• the deeper or higher the barrier the greater the vibratory wavelength intercepted and thus the lower the filter frequency above which the vibrations are attenuated.
• a height of 6-7 m permits intercepting and removing all of the wavelengths less than or equal to 6-7 m and thus intercept and remove all frequencies above about 20Hz.
• the effectiveness and mitigation power of the barrier-system has importance, operating frequency being equal.
• the overall effectiveness of the anti-vibration system in terms of attenuation is the combined effect of its height and its composing material;
• the length of the anti-vibration system is sized so as to project a shadow cone of protection on the receiver and depends on the wavelength of the vibratory motion and on the length of the train;
• the localisation of the anti-vibration system in the space comprised between the source and receiver has a fundamental role for the effectiveness of the mitigation system. If the anti-vibration system is close to the source, then this is an active insulation system; if the anti-vibration system is close to the receiver then this is a passive insulation system.
• the position of the anti- vibration system with respect to the source and receiver significantly affects the insulation power of the anti- vibration system and hence the sizing of the anti- vibration system height.
• the preferable solution is that which provides the anti-vibration system near the source;
• dispersion curve which are essentially composed of surface waves or Rayleigh waves propagated on the ground surface. Conditions (position and size of the anti-vibration system, source type, receiver type) being equal, the propagation velocity of the vibrations as a function of the excitation frequency (dispersion curve) determines the filter frequency of the anti-vibration system and thus its mitigation capacity. This implies that for sizing the anti-vibration system, the dispersion curve of the Rayleigh waves must be measured directly on the ground;
• the distance from the railway line and the receiver size aspects which affect the extension or length of the anti- vibration system, since they affect the minimum shadow cone of protection from the vibrations, projected by the anti- vibration system and inside of which the receiver must be situated.
• a 7 of the formula it was possible to calculate the term A 7 of the formula, in order to evaluate the vibrational impact on the critical receptor in the presence of the anti-vibration system with cell barriers and verify its acceptability with respect to the current laws on the matter.
• the anti-vibration system with cell barrier permits attenuating the vibratory level below the limit thresholds indicated by law.
• the overall length of the anti-vibration system with cell barriers is equal to about 330 m.

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• Engineering & Computer Science (AREA)
• Life Sciences & Earth Sciences (AREA)
• Paleontology (AREA)
• Hydrology & Water Resources (AREA)
• General Life Sciences & Earth Sciences (AREA)
• Mining & Mineral Resources (AREA)
• Environmental & Geological Engineering (AREA)
• Civil Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Structural Engineering (AREA)
• Vibration Prevention Devices (AREA)
• Soil Working Implements (AREA)
• Excavating Of Shafts Or Tunnels (AREA)

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• 2007
  • 2007-01-11 IT ITTO20070015 patent/ITTO20070015A1/it unknown
• 2008
  • 2008-01-10 WO PCT/IT2008/000017 patent/WO2008084510A1/en active Application Filing
  • 2008-01-10 EP EP08720187A patent/EP2104770A1/en not_active Withdrawn

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