Accurate determination of rock mass properties is a critical part of open-pit mine planning activities to enable more prescriptive blast designs to achieve improved loading and hauling and downstream process efficienc...Accurate determination of rock mass properties is a critical part of open-pit mine planning activities to enable more prescriptive blast designs to achieve improved loading and hauling and downstream process efficiency. Better and more accurate blast practice that delivers enhanced outcomes(better fragmentation, improved diggability, less dilution, etc.) is a critical and fundamental element of being able to achieve an effective Mine-Mill approach at a mining operation. Based on previous work, it has been demonstrated that an accurate representation of the rock mass properties can be obtained from the analysis of variations in blasthole drill performance as derived from measurement while drilling(MWD) systems when using tricone bits. This paper further investigates how monitored rate of penetration,pulldown force, rotary torque, rotary speed and bailing air pressure responses can be used to determine the presence of open and partially open fractures having varying dip angles. Based on a correlation of geophysically measured fracture logs and monitored drill performance variables in the same blastholes, the results show that the latter responses can accurately determine open versus closed fractures. The results also identified that variations in rate of penetration and rotary torque show the most sensitivity in the presence of open fractures that intersect a vertical blasthole at near orthogonal angles.展开更多
It is important to understand the behaviour of voussoir beams in the design of underground excavations.There are a large number of discrepancies between the re sults obtained by differe nt researchers so far.To resolv...It is important to understand the behaviour of voussoir beams in the design of underground excavations.There are a large number of discrepancies between the re sults obtained by differe nt researchers so far.To resolve these discrepancies,physically testing the stress distribution at the mid span and abutment of voussoir beam is the key.In this paper,a simple two-block voussoir beam was built with loading system.The displacement and strain of the voussoir beam were measured by a digital image correlation system.The strain distribution along the joints of voussoir beams was firstly revealed.Then,the relationship between transverse load and midspan displacement of voussoir beam was presented.It is found that the stress distributions at the midspan and abutment are different both in shape and depth.The stress distribution is changing as the loading changes as well.展开更多
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文摘Accurate determination of rock mass properties is a critical part of open-pit mine planning activities to enable more prescriptive blast designs to achieve improved loading and hauling and downstream process efficiency. Better and more accurate blast practice that delivers enhanced outcomes(better fragmentation, improved diggability, less dilution, etc.) is a critical and fundamental element of being able to achieve an effective Mine-Mill approach at a mining operation. Based on previous work, it has been demonstrated that an accurate representation of the rock mass properties can be obtained from the analysis of variations in blasthole drill performance as derived from measurement while drilling(MWD) systems when using tricone bits. This paper further investigates how monitored rate of penetration,pulldown force, rotary torque, rotary speed and bailing air pressure responses can be used to determine the presence of open and partially open fractures having varying dip angles. Based on a correlation of geophysically measured fracture logs and monitored drill performance variables in the same blastholes, the results show that the latter responses can accurately determine open versus closed fractures. The results also identified that variations in rate of penetration and rotary torque show the most sensitivity in the presence of open fractures that intersect a vertical blasthole at near orthogonal angles.
文摘It is important to understand the behaviour of voussoir beams in the design of underground excavations.There are a large number of discrepancies between the re sults obtained by differe nt researchers so far.To resolve these discrepancies,physically testing the stress distribution at the mid span and abutment of voussoir beam is the key.In this paper,a simple two-block voussoir beam was built with loading system.The displacement and strain of the voussoir beam were measured by a digital image correlation system.The strain distribution along the joints of voussoir beams was firstly revealed.Then,the relationship between transverse load and midspan displacement of voussoir beam was presented.It is found that the stress distributions at the midspan and abutment are different both in shape and depth.The stress distribution is changing as the loading changes as well.
