Dynamic micromechanical models are used to analyze crack nucleation and propagation in brittle rock. Models of rock created by bonding together thousands individual particles at points contact. The feasibility using these bonded particle reproduce mechanical behavior is explored comparing model results from actual laboratory tests on different types. two granite examined detail study cracking failure patterns that occur during compressional loading. Because discontinuum being used, the free...

The aim of this study is to better understand the mechanics fracture development and propagation during hydraulic fracturing. This paper presents some applications discrete particle modeling problem. A discontinuum approach idealizes material as separate particles bonded together at their contact points utilizes breakage individual structural units or bonds represent damage. numerical models are correlated with existing hydrofracture laboratory experiments, which presented in other...

Abstract A digital seismic network was installed at Atomic Energy of Canada Limited9s Underground Research Laboratory in Manitoba to monitor seismicity induced by the excavation a shaft granite between 324 and 443 m depth. The extension shaft, with design diameter 4.6 m, monitored from January August 1988 several sensors four boreholes ensure good spatial coverage mining faces. Source parameters 155 tremors, selected over 1500 located events, moment magnitude −3.6 −1.9 are studied. corner...

The physical processes generating seismicity within volcanic edifices are highly complex and not fully understood. We report results from a laboratory experiment in which basalt Mount Etna volcano (Italy) was deformed fractured. monitored with an array of transducers around the sample to permit full-waveform capture, location, analysis microseismic events. Rapid post-failure decompression water-filled pore volume damage zone triggered many low-frequency events, analogous long-period...

A stick‐slip event was induced in a cylindrical sample of Westerly granite containing preexisting natural fault by loading at constant confining pressure 150 MPa. Continuously recorded acoustic emission (AE) data and computer tomography (CT)‐generated images the plane were combined to provide detailed examination microscale processes operating on fault. The dynamic event, considered be laboratory analog an earthquake, generated ultrasonic signal that as large‐amplitude AE event. First...

Abstract In this paper we present results from a series of laboratory hydraulic fracture experiments designed to investigate various components the energy budget. The involved cylindrical sample Westerly granite being deformed under triaxial stress states and fractured with distilled water, which was injected at range constant rates. Acoustic emission sensors were absolutely calibrated, radiated seismic estimated. found 7.02E−8% 1.24E−4% injection is consistent values for induced seismicity...

Understanding different seismic signals recorded in active volcanic regions allows geoscientists to derive insight into the processes that generate them. A key type is known as Low Frequency or Long Period (LP) event, generally understood be generated by fluid types resonating cracks and faults. The physical mechanisms of these have been linked either resonance/turbulence within fluids, a result fluids ‘sloshing’ due mixture gas being present system. Less well understood, however, effect...

Abstract In this paper, we revisit acoustic emission (AE) data from an in situ rock fracture experiment conducted at the Underground Research Laboratory (URL) Manitoba, Canada. The Mine‐By experiment, a large‐scale excavation response test, was undertaken depth of 420 m and involved mechanical cylindrical tunnel. During small array 16 Panametrics V103 AE sensors enclosed 0.7 × 1.1 rectangular prism Lac du Bonnet granite located tunnel wall. were later calibrated laboratory, source parameter...

Concurrent ultrasonic tomography and acoustic emission monitoring were employed to study thermally induced microfracturing in an unconfined, 15‐cm cube of Lac du Bonnet granite from Atomic Energy Canada Limited's Underground Research Laboratory. An electrical resistance cartridge heater, placed a central vertical borehole, was used cycle the sample progressively higher peak temperatures between 75°C 175°C. Tomography data collected, at room temperature, before after each thermal cycle....

To assess objectively the source mechanism of mining‐induced seismic events, we developed an algorithm to invert for moment tensor components. From this inversion, ratio isotropic/deviatoric component in is obtained. We are applying method microseismic events (−4<M<−2) recorded at Underground Research Laboratory (URL) Pinawa, Manitoba, where a tunnel being excavated 420 m depth. monitor activity induced by opening array 16 triaxial accelerometers was installed around planned tunnel....

We have deformed basalt from Mount Etna (Italy) in triaxial compression tests under an effective confining pressure representative of conditions a volcanic edifice (40 MPa), and at constant strain rate 5 × 10 −6 s −1 . Despite containing high level pre‐existing microcrack damage, retains strength 475 MPa. monitored the complete deformation cycle through contemporaneous measurements axial strain, pore volume change, compressional wave velocity change acoustic emission (AE) output. been able...

The interaction between hydraulic and natural fractures is of great interest for the energy resource industry because can significantly influence overall geometry effectiveness fractures. Microseismic monitoring provides a unique tool to monitor evolution fracturing around treated rock reservoir, seismic source mechanisms yield information about nature deformation. We performed numerical modeling study using 2D distinct-element particle flow code ([Formula: see text]) simulate realistic...

Abstract This study presents an example illustrating the role of in situ 3D stress path method simulating roof damage development observed Mine-by tunnel at Underground Research Laboratory (URL) located Manitoba, Canada. The path, point 1 cm crown tunnel, was applied to a cubic Lac du Bonnet (LdB) granite sample further understand process and associated seismicity. After careful calibrations, numerical model used reproduce experiment, which produced similar seismicity processes source...

To investigate laboratory earthquakes, stick‐slip events were induced on a saw‐cut Westerly granite sample by triaxial loading at 150 MPa confining pressure. Acoustic emissions (AE) monitored using an innovative continuous waveform recorder. The first motion of each stick slip was recorded as large‐amplitude AE signal. These source locate onto the fault plane, implying that they represent nucleation sites dynamic failure events. precise location varied between and probably controlled...