PASI has been the professional point of reference for those working on the territory, and has needed to continuously expand its field of action as a result of new methods of investigation and reliable and complete monitoring solutions. For this reason, we now offer a full range of instruments and software for Geophysics, Geology, Environmental and Geotechnical Monitoring, Non-Destructive Testing and Structural Controls.
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Our experience and expertise are the result of the on-going development of the company, which has origins far back in time and space: the first PASI instruments originated in India in the 1940s, in the great laboratory at the Geophysical Survey in Calcutta, where Applied Geophysics took its first steps thanks to the talent of an Italian, a true pioneer of modern electronics. And it was India that also saw the start of PASI's international vocation, which - cultivated year after year - now enables us to meet the needs of the global market, exporting all over the world - with pride and determination - “Made in Italy” products that set us apart. We have always believed that Italian Creativity and Design can converge into a product with a pleasant image: this principle is reflected in the “look” of our instruments, much appreciated also abroad.
Since 1956, PASI has been manufacturing seismographs for 'active seismic' surveys: these are instruments capable of measuring the seismic perturbations produced artificially in the ground by a sledge hammer or an explosive charge and measured by a type of sensor known as a geophone. A certain number of geophones (min. 3, more often 12, 24 or more) are driven into the ground, arranged along a rectilinear profile (seismic spreading) with a certain spacing (e.g. 12 geophones at 10m spacing covering a profile that is 110 m long). The most common acquisition methods include:
This geophysical method is based on measuring the arrival times of seismic waves refracted by the interfaces between layers of ground, characterised by different propagation speeds. The energy source is represented by an impact on the surface. The energy radiates from the 'shot point' - travelling both directly in the uppermost layer (direct arrivals), and deep down and laterally along layers at a higher speed (refracted arrivals) - then returning to the surface, where it is measured through the spreading of geophones geophone spreading (10 Hz frequency). Energising in different positions on the surface, it will be possible to deduce information about the geometry of the deep refractor layer, in many cases coincident with the bedrock.
This geophysical survey is based on measuring the outbound/inbound travel times of the seismic waves transmitted from the surface and reflected towards the surface of geological horizons with different characteristics. The energy transmitted is only reflected when there is a contrast of acoustic impedance (the product of the speed x the density of the material) between two superimposed layers. The scale of the contrast in the acoustic impedance between the two layers determines the amplitude of the reflected signal, which is measured on the surface thanks to a spreading of high frequency geophones (40 Hz, 100 Hz). As in the case of seismic refraction, the energy is produced by a ¨shot¨ or impact on the surface. For surface applications, this involves the use of a sledge hammer and a striking plate, a dropping weight, a seismic energiser or an explosive charge.
Down Hole & Cross Hole
In this type of seismic survey, the source and/or geophones are located in a hole prepared especially in the ground. One of the most common methods involves down hole testing (the source is on the surface, the sensor on the other hand is a 3D borehole geophone (P- & S-waves) or a chain of hydrophones (P-waves only, in a hole filled with water or drilling fluid). The down hole test aims to determine the profiles of the seismic compression waves (P-waves) and shear waves (S-waves) with the depth. It consists of producing a perturbation on the ground surface by means of a mechanical source and measuring the arrival time of the P- and S-waves at various depths in the hole prepared for the purpose. This technique is also used for calculating the Vs30 as an alternative to surface methods (e.g. MASW). Cross hole seismic tests, on the other hand, involve measuring the speed of the seismic waves between two survey holes, one for energisation (normally made with a borehole energiser or explosive) and the other for measurements (with a three-dimensional borehole geophone clamped at a certain depth). For each acquisition, the energisation depth and measuring sensor depth in the two holes should be the same. In this case, therefore, there must be two separate survey holes whose reciprocal distance from all the measurement levels must be known.
Multichannel Analysis of Surface Waves (MASW)
MASW is the acronym for Multichannel Analysis of Surface Waves. This indicates that the phenomenon being analysed is the propagation of surface waves. More specifically, the analysis focuses on the dispersion of surface waves (i.e. the fact that different frequencies – with different wavelengths - travel at different speeds). The basic principle is quite simple: the various components (frequencies) of the seismic signal that is being propagated travel at a speed that depends on the characteristics of the medium. More specifically: the larger wavelengths (i.e. the lower frequencies) are influenced by the deepest layers, while the small wavelengths (the highest frequencies) depend on the characteristics of the layers nearest the surface. As, typically, the speed of the seismic waves increases with depth, this will be reflected in the fact that the lowest frequencies of the surface waves will travel at a higher speed than the higher frequencies. MASW is traditionally performed by analysing Rayleigh waves, which are recorded using common 4.5Hz vertical component geophones - those used also for refraction in compressional waves - and considering a very common source with vertical impact, i.e. the classic sledge hammer. This occurs for at least two reasons: 1. these geophones (and this acquisition method) are by far the simplest and most common. 2. the propagation and dispersion of Rayleigh waves occurs without any problems even in low speed channels (speed reversals) which, as we know, are invisible for refraction. On the other hand, exploiting the dispersion of Love waves (together with that of Rayleigh waves) is an exciting new frontier for MASW analysis (see the winMASW manual for more information) (please note that the use of Love waves is only possible with the MASW technique and not with the ReMi – Refraction Microtremors - technique). In summary: as the dispersion of the surface waves depends on the characteristics of the sub-soil (mainly on its vertical variations), by determining the dispersion curves, it is possible to deduce the characteristics of the medium (the essential parameters are the speed of the shear waves and the thickness of the layers) and all the parameter requested by the new seismic regulations introduced in most Countries all over the world.
In light of the new seismic legislation, the measurement of environmental seismic vibrations or seismic noise has acquired considerable importance. The analysis of seismic noise measurements can be conducted using three methods: Fourier spectra Spectral ratios H/V spectral ratios The latter, which provides the most reliable results, is also known as the HVSR (Horizontal to Vertical Spectral Ratio) method or the Nakamura method. The H/V spectral ratio technique consists of calculating the ratio of the Fourier spectra of the noise in the horizontal plane H (generally the spectrum H is calculated as the average of the Fourier spectra of the horizontal components NS and EW) and the vertical component V. The acquisition of HVSR data, obtained using low frequency triaxial (3D) geophones, make it possible to determine with accuracy the characteristic frequency of resonance of the site, an essential parameter for the correct dimensioning of earthquake-resistant buildings. During the design, it is important to build structures with different resonant frequencies to the ground, thereby preventing the ¨double resonance¨ effect which is extremely dangerous for structural stability. Seismic microzonation studies using the HVSR measurement method have therefore become an integral, essential instrument in the design of earthquake-resistant buildings.
Despite starting from the basic principles of geoelectrics, electrical imaging or electrical tomography (ERT) has opened a new chapter in the history of geophysical surveys. Instead of using only 4 electrodes, as in 'traditional' vertical electrical surveys, the investigation on the ground is carried out using a set of electrodes (from a minimum of 16 up to several hundred), distributed along a profile with an interdistance of few metres. Using a special system - based on one or more multi-electrode cables and related 'switching boxes' - these electrodes are connected to the data acquisition unit/energiser so as to be able to operate alternately as current electrodes or measuring electrodes. In this way, the measurements along a profile can proceed in an automatic manner according to the desired sequence (the most commonly used spreadings include Wenner, Wenner-Schlumberger, Dipole-Dipole), returning apparent resistivity values at different depths and locations along the profile itself. The result of processing this data is a real two-dimensional cross-section which represents the distribution of the resistivity values ??of the ground. By combining several parallel ground resistivity profiles, it is possible to obtain a 2.5D high definition display. With a greater number of electrodes, it is even possible to perform real 3D tomography investigations, suitably interpreted by means of sophisticated processing software.
The extreme versatility and measuring accuracy makes this method of investigation suitable for the widest areas of application. Here are just some examples of the most common applications: - Environmental monitoring: in dumping areas, using electrical tomography it is possible to display the presence or absence of leaks in the waterproof insulating substrate quickly and clearly. The method can be also applied in also lends itself greatly to medium- to long-term monitoring of the dispersion of pollutants in the ground in cases of environmental accidents. - Hydrogeology: the creation of electrical tomographic cross-sections allows the highly precise identification of lithological discontinuities, water accumulation zones, rock fracturing zones and circulation of fluids inside the discontinuity. - Archaeology: identification of artefacts and remains by measuring the difference in resistivity between the materials - Geotechnics, surface geology, geomorphology: identification of possible causes of subsidence, locations and structures of underground cavities and tunnels, detailed investigations of mineral deposits and quarry areas, identifying breakaway surfaces in landslide areas.
Among the first methods to be used in the history of applied geophysics, geoelectrical methods have evolved greatly over nearly a century. In earth resistivity prospecting, the physical parameter that is determined is the electrical resistivity of the formations which make up the sub-soil and which can vary according to the lithotype, the degree of homogeneity, the degree of alteration and fracturing, the content in water and salts, the particle size etc. To measure the resistivity of the sub-soil where stratification is flat and parallel, the Vertical Electrical Sounding (VES) technique is used. This includes a series of resistivity measurements carried out with a gradually increasing distance between the current electrodes (A-B) and the potential electrodes (M-N), according to a device with four electrodes (the most commonly used include the Wenner four-pin and the Schlumberger four-pin spreadings). Through the two current electrodes (A and B), a direct current (normally supplied by rechargeable accumulators or a generator), switched periodically to prevent polarisation phenomena on the electrodes, is introduced into the ground. The two measuring electrodes (M and N) measure the difference in potential generated in the sub-soil when the current passes between A and B. The measurements of the potential difference (AV) and current intensity (AI) are carried out using instruments called earth resistivity meters. To extend the resistivity measurements to gradually deeper layers, the distance between the A-B and M-N electrodes is increased. In this way, the current lines cross portions of the sub-soil that become increasingly deep. Plotting the apparent resistivity values on a bi-logarithmic diagram builds the apparent resistivity curves in which the values ?? of AB/2 on the abscissa are expressed in metres, while the resistivity values, on the ordinates, are expressed in Ohm/m. Using suitable inversion software, the apparent resistivity curves obtained in this way can be traced back to the true resistivity values and the thicknesses of the electro-coating electro-strata, thus obtaining valuable information especially when searching for groundwater.
Video inspections in wells can detect the construction characteristics of the well: the blind and filter pipes, the respective installation depths and any variations in diameter in the hole. The television probe – which must be waterproof and resistant to the pressure generated by the water column above it – is equipped with a special wide angle lens that allows detailed diagnosis of the coating. Any anomaly may not only be highlighted at a certain depth from ground level but may also be photographed or even filmed during the investigation. Performing a video inspection can determine the causes of the most common problems that can affect a well in the course of its productive life, such as the presence of sand and a decrease in water flow. Furthermore, it can detect abnormalities such as deterioration, deformation, corrosion, cracks and excessive deposit on the bottom. The well TV camera can assess situations of risk from degradation and the appropriate measures needed to repair the well. Maintenance can therefore be conveniently scheduled according to the typical characteristics of the groundwater and resulting problems. It will also be possible to rapidly complete the missing documentation for existing wells (total depth, depth of installation of the filtering features, type of pipes and efficiency) and to check the actual conditions before performing costly repair work.
In the case of applications in boreholes or other kinds of holes, characterised by horizontal rather than vertical development, it is necessary to use borehole TV cameras with even more compact dimensions, especially those equipped with a 'push-rod' system: this is a special fibreglass cable wound around a special roller reel which – mounted on the head of the TV camera via an adapter - provides a thrust to the camera which allows it to move progressively into the hole.
If visual inspections are carried out in small holes in buildings and constructions in general, the smaller size becomes indispensable. It is then important to use miniature instruments called endoscopes, characterised by a head with a diameter of just a few millimetres and fibre optic cables for transmitting the image that are no more than a few metres long.
PASI best sellers all over the world, water level indicators measure the piezometric level of a liquid (usually water) intended for fast measurements in wells and tanks by a single operator, who can work comfortably on the surface. It is a portable instrument, easy to use and simple to maintain, ideal for monitoring the variations in level of groundwater within piezometers, often used as the first instrument of monitoring for dams, for areas surrounding dumps and also in areas with high levels of groundwater drainage. The measurement is made using flexible probe with a diameter of just 10 mm. Water level indicators are also essential for monitoring wells and checking for contamination between groundwater at different depths and crossed by a single well. Sometimes, in addition, it can also be interesting to measure the temperature of the water inside the well. Similarly, in alluvial ground, it will be important to periodically check the bottom depth from the surface in order to check for silting up of the well itself, at the base of which the finer sediments not retained by the casing windows may accumulate.
Oil Water Interface
Oil water interface meters are portable instruments suitable for measuring the thickness of the supernatant (hydrocarbons, foam, trichloroethylene etc...) that may be floating on the surface of the water in wells and/or tanks. The instrument indicates the presence of water by means of two stainless steel spikes and an electronic circuit that measures the electric current circulating through the water. The instrument identifies the product by means of a special prism system. A beam of IR light is emitted by the sensor, hits the prism with an angle of 45 degrees and is refracted internally according to Snell´s Law. If the prism is immersed in a liquid with an optical index similar to that of the prism itself, the light beam will not be refracted internally, but will emerge from the prism. The absence of the pulse indicates that the prism is immersed in a liquid. A microprocessor determines that if the prism is in conductive fluid, this should be water. Lowering the probe into the well, the IR sensor determines the presence of the product (usually a hydrocarbon) at the depth indicated on the special millimetre-marked cable, while a conductivity sensor detects the water level below. The transition between the two media is indicated by the change from an intermittent tone and flashing light (product) to a continuous tone (water). Through a double adjustment of the sensitivity (one for the IR sensor and one for the conductivity sensor) these meters can also be used in the presence of very viscous oils or very saline water. The probe is pressurised and the oil/water interface will be found whether the product floats or tends to sink.
Non-Destructive Testing on Concrete
Non-destructive tests are the first investigation method to check the actual conditions of a structure, whether under construction or existing. As also indicated by the new anti-seismic legislation, the use of non-destructive investigation methods dramatically reduces the number of specimens needed for laboratory analysis, resulting in benefits not only in terms of the time needed to complete the investigation, but also from an economic viewpoint.
Rebound Hammer Sclerometer Tests
The mechanical sclerometer rebound hammer - the 'original Schmidt hammer' invented by Ernst Schmidt in the early 1960s and produced by the Swiss company Proceq - was one of the first instruments designed for concrete testing and is still recognised as the reference standard for fast diagnosis of a reinforced concrete structure. The rebound value (R) measured on site with the rebound hammer sclerometer test is closely related to the compressive strength value of the concrete obtained from breaking tests on specimens in the laboratory. The digital rebound hammer sclerometer represented the next step, with the introduction of the digital readout, data storage and statistical calculation, facilitating data reporting by the specialist professional. More than 50 years after the debut of the 'original Schmidt hammer', it was the same Swiss company, Proceq that took another definitive step forward with the new integrated digital Proceq SilverSchmidt rebound hammer sclerometer. Its revolutionary measuring system, greater precision in the result and the practical, intuitive user interface make it an instrument that truly stands out. Thanks to its measuring range extended from 10 to 100 N/mm2, this revolutionary instrument can work on both standard and HPC concrete, providing direct, immediate results, regardless of the testing angle.
The mapping of the reinforcing bars is crucial not only for monitoring the condition of the structure, but also for the subsequent rebound hammer test sclerometric and ultrasonic investigations. As established by legislation, in fact, the rebound hammer sclerometric test is not valid if carried out near reinforcing bars, whose presence has a significant effect, distorting the compressive strength value of the concrete. Modern cover meters rebar locators use the induced current (Eddy current) technique, i.e. they measure the variation of the electromagnetic field induced by the presence of the reinforcing bar in articles made using reinforced concrete. By analysing the intensity of the signal, it is possible to reach a very precise definition of the thickness of the concrete cover and calculate with a good approximation also of the diameter of the rebar, without drilling or demolishing.
The propagation speed of the ultrasonic pulse in a medium depends on its density and its elastic properties, which in turn are closely linked to the quality and strength of the material itself. Ultrasonic investigations therefore make it possible to determine the characteristics of the concrete: uniformity of the material, presence of cavities or honeycombs, identifying damage caused by fire or frost, modulus of elasticity, strength of the material. In analysing reinforced concrete hardened as a result of surface carbonation phenomena, it is useful to perform measurements using the SONREB (SONic + REBound) method: ultrasounds + rebound test sclerometer) which gives a precise correlation between the two methods. Using this combined method, the influence of the particle size of the aggregates, the dosage, the type of cement and any additives used for casting the concrete is reduced compared to a simple ultrasonic investigation. Moreover, the SONREB method cancels out the effect that the moisture content and degree of curing of the concrete may have on the results of the analyses.
Corrosion of the Reinforcement
Although the reinforcement bars in reinforced concrete are immersed in the cement matrix, they may be subject to corrosion. This occurs when, following the carbonation process triggered by the diffusion of carbon dioxide inside the cement paste, there is a reduction in the pH which creates the ideal environment for corrosion of the reinforcing bars. The corrosion of the reinforcing bars involves the following degrading phenomena: the reduction of the resistant cross-section of the rebar bar with a consequent reduction in its load-bearing and fatigue strength; the cracking of the concrete cover with consequent expulsion when the tensions generated in the concrete due to the expansive phenomena accompanying the formation of rust exceed the tensile strength of the material. The expulsion of the concrete cover naturally causes the complete exposure of the bars to the aggressive effects of the environment, which are therefore accelerated. The phenomenon can be evaluated and monitored over time using sensors able to measure - in a totally non-destructive manner - the difference in electrical potential generated between the reinforcement and the surface of the reinforced concrete, indicating the areas where the gradient of potential is indicative of corrosion. Resistive methods using a Wenner probe are also used to supplement this type of investigation.
Extraction Test for Anchors and Eyebolts
Extraction testers are specific instruments for measuring the clamping strength of bolts and anchors. The extraction test is carried out by tightening the adapter to the element to be extracted (for example an anchor) and starting the traction manoeuvre. When the anchor starts to slip off, the pressure gauge will indicate the force applied to overcome the sealing strength.
The Pull-Off technique allows the measurement of the tensile strength of a given material or the determination of the adhesion strength between two different materials (typically the adhesion value of mortars and plasters on the walls). The test consists of fixing a circular aluminium element to the surface of the material to be tested using specific two-component resins and, after having isolated the test surface, with an incision made using a dedicated core barrel, removing it using a special instrumented extractor, measuring the last tensile strength value.
Tests on foundation piles:
The ¨Cross Hole Ultrasonic Monitor¨ CHUM uses the sonic ¨cross-hole¨ (CSL) method to make an accurate, high-resolution assessment of deep foundations. An ultrasonic wave is sent from a transmitter to a receiver, moved along the entire length of the pile inside pipes ¨embedded¨ inside it during casting. The wave velocity and its energy are strongly influenced by the quality of the cement itself. Other methods supported by CHUM are ¨Single Hole Ultrasonic Testing¨ (SHUT) and tomography (2D and 3D).
Pet – Pile Echo Test
The Pile Echo Test is another measuring method used in assessing structural integrity in the load-bearing elements of a building. This method of measurement is based on the measurement of a wave reflected inside the pile. The wave generated manually using a hammer propagates inside the structural element; and, using the measuring sensor to analyse, analysing the spectrum of the emitted signal, it is possible to determine the length of the pile being examined and see whether it is intact.
Humidity and Temperature Test
The presence of humidity within a structure is often among the first direct causes or the trigger for many forms of degradation. Proper assessment of humidity is also essential for all those involved in laying coverings of any kind, as well as woodworking. The range of instruments distributed by PASI aims to satisfy any requirement with specific instruments for each individual application or modular and expandable ones. Humidity meters (hygrometers and moisture meters) are pocket instruments that enable immediate assessment of the water content inside a structure quickly and in a completely non-destructive manner on all types of material (plaster, concrete, brick, wood). Systems are also offered for continuous measurement of environmental parameters, suitable for monitoring any kind of internal environment.
Thermography is a remote sensing technique, performed by acquiring images in the infrared range. A thermographic camera is an instrument able to measure the temperatures of the bodies analysed by measuring the intensity of infrared radiation emitted by the body in question. Below is a list of possible applications of thermography: - Construction: searching for leaks in the plumbing system, checking for roof seepage, displaying energy losses to plan actions aimed at improvement, identifying structural defects, identifying thermal bridges, preventing plaster detachment, identifying dangerous condensation spots with mould, checking the adherence of facade elements, preventive electrical maintenance on low, medium and high voltages: identifying hot spots in cabinets, circuits, electrical systems, terminal blocks, fuses, motor windings and consequently preventing dangerous overheating and fires. - Restoration of cultural heritage: identifying traces of previous remediations restorations, identifying possible detachment points on frescoes, determining the wall texture and previous cladding. In the field of restoration, thermography allows very precise analysis of what can be found under the layer of plaster and means that the intervention can be planned more carefully. - Fire Brigade and Civil Protection (fire detection and prevention): detecting gas leaks, determining the point of ignition of the fire, detecting hot spots on stacked flammable materials. - Preventive mechanical maintenance. - Checking valves and pipes.
Wireless Data Acquisition Systems
For all cases where continuous monitoring is required, it is necessary to use a digital data acquisition system based on the combination of transducers and control units for data acquisition and storage. Data acquisition is the starting point for understanding, measuring, monitoring and managing the mechanism of each phenomenon or process. With the aid of one or more sensors, the information, converted into electrical pulses, is transmitted to an instrument which conditions, amplifies, measures, processes, displays and stores the signals themselves. PASI is able to offer a full range of electronic control units for geotechnical monitoring, environmental monitoring and microclimatic monitoring, managing analogue and digital measurements from one or more external transducers. The wireless WINECAP control units are particularly versatile and easy to install and can be used in a wide range of fields: - structures and buildings - groundwater - meteorological parameters (climate and microclimate) - inclinometric measurements - geotechnical parameters
Water Quality Monitoring
Monitoring the main physical and chemical parameters is critical in order to keep water quality under control, regardless of what it is used for: water analysis is, in fact, essential in many areas of environmental monitoring, ranging from control of the sources and mineral water to aquaculture, fish farming and monitoring industrial discharges, wastewater etc. Geotechnical monitoring, especially for controlling dams, landslides, watercourses and reservoirs, also involves continuous monitoring of changes in piezometric level, which can be decisive in preventing hydrogeological instability which is now unfortunately a frequent occurrence. Another chapter of groundwater monitoring involves well flow tests, essential in order to check the efficiency of the pumping system: also in this case a water level sensor which stores data during the test is an important instrument for checking and optimising production.
Water monitoring requirements are mainly divided into two categories: continuous monitoring (for which it is necessary to store the data measured automatically at predetermined intervals by a fixed probe equipped with a data acquisition unit or 'data logger') and time–to–time monitoring (where the operator goes periodically to take the measurements from samples taken at the site, using portable instruments).
Monitoring of Cracks on Structures and Buildings
Crack meters are the most simple and immediate instruments used to check damage to buildings or structures. Available in different models (for walls, corners, floors etc.), they are all made up of two overlapping plates. The upper one is transparent and has a grid engraved on it, while the lower one is graduated in millimetres both horizontally and vertically, with the zero located at the intersection of the median lines. The crack meter is positioned so that it straddles the crack, with the zeros on the grids coinciding. The direction and magnitude of the mutual displacement of the parts (in millimetres) are read directly on the graduated plate and can then be observed and monitored over time. If measurement accuracy superior to millimetric accuracy is required, devices (removable crack-meters) must be used that can monitor the evolution of the distance between two or more references linked to the structure (bar or disk datum point) by taking measurements using an analogue or digital comparator. It then becomes possible to achieve accuracy of a hundredth or a thousandth of a millimetre, which allows the user to evaluate the trend of developments in the crack pattern in question (accelerated, delayed, steady, stable progression). In support of these instruments is the MOSES software, able to handle the data acquired on site, collecting it immediately in the test reports accompanied by the most appropriate photographic documentation and graphs.
Environmental monitoring also extends to issues related to site safety. Special regulations ?? refer specifically to noise and vibration due to construction activities and the working environment in general, where structures and individuals may be subject to stress that is sometimes unacceptable or difficult to put up with over time. Increased sensitivity to these issues is reflected in increased attention from workers and citizens in those situations that can easily trigger proven discomfort and long, tedious litigation. In accordance with the DIN 4150-3 standard (Vibration in Buildings, part 3: Effects on structures, 1999), UNI 9916 (Criteria for the measurement of vibrations and the assessment of their effects on buildings, 2004) and UNI 9614 (Vibration measurement in buildings and annoyance evaluation, 1990), blasting activities can be designed, used and monitored so that the vibrations produced in homes nearby are under the threshold at which damage can be caused to buildings and disturbance to residents. To document compliance with the conditions relating to safety and tolerability established by the law, it is advisable to monitor the explosions using one or more vibration monitors, appropriately positioned within the site. Similarly, the vibrations caused by construction activities in urban areas can also create a disturbance for people or even cause or aggravate damage to existing buildings. In this case the vibration monitor can be suitably positioned by the structure to be monitored to check whether the vibrations caused exceed the threshold indicated by the legislation.
Noise in the Working Environment
Noise in the working environment has become one of the most important issues related to hygiene in the workplace. The continuous mechanisation of production with the introduction of continuous technological processes has led to the proliferation of noise sources and an increase in the percentage of workers exposed to this risk factor. Noise as the transmission of sounds is a vibratory phenomenon. The most important parameters for measuring the sound wave are the amplitude (representing the value assumed by the pressure) and the frequency (number of oscillations performed by the vibration in one second). The sound is measured in decibels as regards the sound pressure and in hertz and as regards the frequency. The exposure time and the sound pressure are key factors in defining the biological effect of the noise itself. Given the complexity of the biological effect of the noise phenomenon, other parameters may influence its effect, such as the distribution of the frequencies or the individual characteristics of individuals. The instruments with noise can be monitored are called noise meters. These are divided into Class 1 noise meters (suitable for certification) and Class 2 noise meters (normally suitable for internal monitoring). Pocket-sized personal dosimeters that can be attached directly to the clothing of the worker at risk of exposure have recently been introduced. Where noise exposure exceeds 80 decibels, the employer must provide workers with hearing protection devices.
Vibrations on the Human Body
The repetitive oscillatory motion of a body over time (vibration) can be transmitted to humans by contact. The risk from vibration can occur in a variety of circumstances such as driving vehicles, using industrial machinery, using tools powered by electricity or compressed air with striking movements (pneumatic hammers, milling cutters, drills, rock hammers).The obligation to assess the risk and implement the appropriate preventive, protective and health surveillance measures, also applies to exposure to vibrations in the workplace. Vibrations are normally classified according to the type of energy transmission: localised, generally through the hand, and generalised, through the surface in contact with the operator´s body, in both a standing and sitting position. The first are associated with a series of symptoms commonly referred to as ¨Hand-arm vibration syndrome¨. The effects of vibrations on the whole body, on the other hand, can involve various internal organs and systems (gastrointestinal, urinary and genital, vertebral column, visual system, neuropsychological system). Vibrations involving the whole body (¨whole body vibrations¨), on the other hand, are linked to various sources, such as transportation, self-propelled machines, stationary systems.
Together with the geologist´s hammer, a geological compass is an indispensable tool for getting started with any investigation on the ground. A geological compass, which must always feature a sight, flat side edge, level and clinometer, allows geologists to collect essential information which – transferred onto a detailed topographic map - enables the geological survey of an area. Progress has been made in recent years in geo-referencing of field measurements thanks to GPS (Global Positioning System), with which it is possible to ¨mark¨ points of measurement on digital topographic maps quickly, economically and efficiently, added increasingly precise, accurate date to technical reports. A pocket GPS is now an indispensable tool for orientation and navigation, for geo-referencing points in the field, for memorising waypoints and routes and for calculating distances and areas automatically. Further information may be collected from the ground by the geologist performing geomechanical tests on the surface layer of the ground under consideration using pocket vane testers and pocket penetrometers.