Proučavanje odnosa između statičnog i dinamičnog modula stijena

Non-destructive techniques based on the propagation of ultrasonic wave through the elastic medium were used for determination of dynamic modulus of selected samples of rocks in laboratory. The calculated values of dynamic modulus were compared with values of static modulus determined in laboratory on samples tested by applied loading. A method of estimation of the static modulus in situ conditions, where the measurements cannot be carried out, is discussed.Za laboratorijsko određivanje elastičnog i dinamičnog modula odabranih uzoraka stijena uporabljene su nerazarajuće tehnike temeljene na širenju ultrazvučnih valova kroz elastični medij. Izračunate vrijednosti dinamičkog modula su uspoređene s vrijednostima statičnog modula određenog u laboratoriju na uzorcima testiranim primjenom opterćivanja. Raspravljena je i metoda utvrđivanja statičnog modula u uvjetima “in situ” gdje mjerenja ne mogu biti provedena

Proučavanje odnosa između statičnog i dinamičnog modula stijena

Non-destructive techniques based on the propagation of ultrasonic wave through the elastic medium were used for determination of dynamic modulus of selected samples of rocks in laboratory. The calculated values of dynamic modulus were compared with values of static modulus determined in laboratory on samples tested by applied loading. A method of estimation of the static modulus in situ conditions, where the measurements cannot be carried out, is discussed.Za laboratorijsko određivanje elastičnog i dinamičnog modula odabranih uzoraka stijena uporabljene su nerazarajuće tehnike temeljene na širenju ultrazvučnih valova kroz elastični medij. Izračunate vrijednosti dinamičkog modula su uspoređene s vrijednostima statičnog modula određenog u laboratoriju na uzorcima testiranim primjenom opterćivanja. Raspravljena je i metoda utvrđivanja statičnog modula u uvjetima “in situ” gdje mjerenja ne mogu biti provedena

Fraktalna geometrija i primjena impulsne dinamičke metode u procjenjivanju poremećaja u stijenama

In this paper the fractal geometry, interpreting the size effect was used for evaluation of disturbance of samples of rocks. Fractal geometry offers a possibility to describe the non-regular structure of natural objects by fractal dimension, from which it is possible e.g. to estimate the measure of rock disturbance. The micro-disturbance of rock samples was compared with the results of ultrasonic pulsing method, where the disturbance indexes IQ were calculated from the velocities of exciting ultrasonic waves spreading through the rock medium.U radu je korištena fraktalna geometrija za tumačenje efekta veličine radi procjene poremećaja u uzorcima stijena. Fraktalna geometrija nudi mogućnost da se fraktalnim, dimenzijama opiše neregularna struktura prirodnih objekata iz čega je moguće, npr. utvrditi dimenzije poremećaja u stijenama. Mikropromjene u uzorcima stijena uspoređene su s rezultatima metode ultrazvučnog titranja gdje se indeksi promjena IQ računaju iz brzine širenja pobuđenih ultrazvučnih valova kroz medij stijena

Kontrola akustičnom metodom raspadanja stijena pri rotacionom bušenju

The contribution describes the technical and algorithmic solution of the optimization of rotary drilling. The global optimization criteria express the minimum specific energy on drilling and the maximum speed of drilling. The article presents the first results of research on the utilization of acoustic methods in indirect measurement of criterion function by optimizing these processes.Rad opisuje tehničko i algoritmičko rješenje optimalizacije rotacionog bušenja. Globalna optimalizacija kriterija izražava minimalnu specifičnu energiju bušenja i maksimalnu brzinu bušenja. Članak predstavlja prve rezultate istraživanja primjene akustičkih metoda u neizravnom mjerenju funkcije kriterija optimaliziranjem tih procesa

Experimental study of filling and emptying of a large-scale pipeline

The ¿lling with liquid of an initially empty pipeline and its counterpart, the draining of an initially liquid-¿lled pipeline, are of great interest due to the many practical applications. Several potential problems may occur, of which water-hammer and slug impact are the most important. To investigate the ¿lling and emptying processes, di¿erent mathematical models have been proposed, in which a common assumption is that the water column evolves with unchanged front and/or tail. This is a reasonable assumption for small-scale systems, particularly in cases with relatively high upstream pressure head and low downstream resistance. However, it is not clear whether this assumption is applicable to large-scale systems. This issue is of high importance for the development of air pockets and gravity currents in pipelines during ¿lling and draining processes. This study presents the experimental results of the ¿ow behaviour during the rapid ¿lling and emptying of a large-scale pipeline. The experimental apparatus was designed and built at Deltares, Delft, The Netherlands, as part of the EC Hydralab III project. Di¿erent from other laboratory studies, the scale of this experiment is close to the practical situation in many industrial plants. The test rig includes a variety of components (e.g. tanks, ¿ow meters, valves, pipes of di¿erent materials) and the operation procedure is rather complex. The ¿ow behaviour is measured by various instruments and hence a thorough hydrodynamic analysis is possible. All these features make the current study particularly useful as a test case for real ¿lling and draining situations. In the ¿lling of an initially empty pipeline, the focus was on the overall behaviour of the lengthening water column and the water-air interface evolution. In the emptying of an initially water-¿lled pipeline, together with the hydrodynamics of the shortening water column, the shape and behaviour of the water tail (air-water interface) was investigated. Thirteen di¿erent combinations of initial upstream driving air pressure and downstream valve resistance were tested. The in¿uence of these two factors on the out¿ow rate is clari¿ed. It was con¿rmed that both the in¿ow front in ¿lling and the out¿ow tail in emptying do not entirely ¿ll the pipe cross section. Shape changes occur at both the water-air and air-water interfaces. Although the ¿ow regime transition is a rather complex phenomenon, certain features of the transition pattern are observed and explained qualitatively and quantitatively

Water hammer and column separation due to accidental simultaneous closure of control valves in a large scale two-phase flow experimental test rig

A large-scale pipeline test rig at Deltares, Delft, The Netherlands has been used for filling and emptying experiments. Tests have been conducted in a horizontal 250 mm diameter PVC pipe of 258 m length with control valves at the downstream and upstream ends. This paper investigates the accidental simultaneous closure of two automatic control valves during initial testing of the test rig. The simultaneous closure of both valves has induced upsurge and downsurge at the same time. Large water hammer and column separation have caused failure of pipe supports and leakage at pipe joints. The incident was caused by a fault in an electronic conversion box due to power failure. Afterwards the downstream end automatic valve has been modified to a manually operated valve to avoid the accidental simultaneous closure of the valves. The accidental transient event has been fully recorded with pressures, flow rates and water levels. The measurements of the accident are presented, analyzed and discussed in detail. Photographs show the damages to the system

Water hammer and column separation due to accidental simultaneous closure of control valves in a large scale two-phase flow experimental test rig

A large-scale pipeline test rig at Deltares, Delft, The Netherlands has been used for filling and emptying experiments. Tests have been conducted in a horizontal 250 mm diameter PVC pipe of 258 m length with control valves at the downstream and upstream ends. This paper investigates the accidental simultaneous closure of two automatic control valves during initial testing of the test rig. The simultaneous closure of both valves has induced upsurge and downsurge at the same time. Large water hammer and column separation have caused failure of pipe supports and leakage at pipe joints. The incident was caused by a fault in an electronic conversion box due to power failure. Afterwards the downstream end automatic valve has been modified to a manually operated valve to avoid the accidental simultaneous closure of the valves. The accidental transient event has been fully recorded with pressures, flow rates and water levels. The measurements of the accident are presented, analyzed and discussed in detail. Photographs show the damages to the system

Water hammer and column separation due to accidental simultaneous closure of control valves in a large scale two-phase flow experimental test rig

A large-scale pipeline test rig at Deltares, Delft, The Netherlands has been used for filling and emptying experiments. Tests have been conducted in a horizontal 250 mm diameter PVC pipe of 258 m length with control valves at the downstream and upstream ends. This paper investigates the accidental simultaneous closure of two automatic control valves during initial testing of the test rig. The simultaneous closure of both valves has induced upsurge and downsurge at the same time. Large water hammer and column separation have caused failure of pipe supports and leakage at pipe joints. The incident was caused by a fault in an electronic conversion box due to power failure. Afterwards the downstream end automatic valve has been modified to a manually operated valve to avoid the accidental simultaneous closure of the valves. The accidental transient event has been fully recorded with pressures, flow rates and water levels. The measurements of the accident are presented, analyzed and discussed in detail. Photographs show the damages to the system