The paper is a summary of discussions on four topics in rockburst and dynamic ground support.Topic 1 is the mechanisms of rockburst.Rockburst events are classified into two categories in accordance with the triggering...The paper is a summary of discussions on four topics in rockburst and dynamic ground support.Topic 1 is the mechanisms of rockburst.Rockburst events are classified into two categories in accordance with the triggering mechanisms,i.e.strain burst and fault-slip burst.Strain burst occurs on rock surfaces when the tangential stress exceeds the rock strength in hard and brittle rocks.Fault-slip burst is triggered by fault-slip induced seismicity.Topic 2 is prediction and forecasting of rockburst events.Prediction for a rockburst event must tell the location,timing and magnitude of the event.Forecasting could simply foresee the probability of some of the three parameters.It is extremely challenging to predict rockbursts and large seismic events with current knowledge and technologies,but forecasting is possible,for example the possible locations of strain burst in an underground opening.At present,the approach using seismic monitoring and numerical modelling is a promising forecasting method.Topic 3 is preconditioning methods.The current preconditioning methods are blasting,relief-hole drilling and hydrofracturing.Defusing fault-slip seismicity is difficult and challenging but has been achieved.In very deep locations(>3000 m),the fracturing could extend from the excavation face to a deep location ahead of the face and therefore preconditioning is usually not required.Topic 4 is dynamic ground support against rockburst.Dynamic ground support requires that the support system be strong enough to sustain the momentum of the ejecting rock on one hand and tough enough on the other hand to absorb the strain and seismic energies released from the rock mass.The current dynamic support systems in underground mining are composed of yielding tendons and flexible surface retaining elements like mesh/screen and straps.Yielding props and engineered timber props are also used for dynamic support.展开更多
This work presents a study on the behaviors of diatomaceous soils. Although studies are rarely reported on these soils, they have been identified in Mexico City, the Sea of Japan, the northeast coast of Australia,the ...This work presents a study on the behaviors of diatomaceous soils. Although studies are rarely reported on these soils, they have been identified in Mexico City, the Sea of Japan, the northeast coast of Australia,the equatorial Pacific, and the lacustrine deposit of Bogota(Colombia), among other locations. Features of this kind of soil include high friction angle, high initial void ratio, high compressibility index, high liquid limit, and low density. Some of these features are counterintuitive from a classical soil mechanics viewpoint. To understand the geotechnical properties of the diatomaceous soil, a comprehensive experimental plan consisting of more than 2400 tests was performed, including physical tests such as grain size distribution, Atterberg limits, density of solid particles, and organic matter content; and mechanical tests such as oedometric compression tests, unconfined compression tests, and triaxial tests.Laboratory tests were complemented with scanning electron microscope(SEM) observations to evaluate the microstructure of the soil. The test results show that there is an increase in liquid limit with increasing diatomaceous content, and the friction angle also increases with increasing diatomaceous content. In addition, several practical correlations were proposed for this soil type for shear strength mobilization and intrinsic compression line. Finally, useful correlations were presented, such as the relationship between the state consistency and the undrained shear strength, the friction angle and the liquid limit, the void ratio at 100 kPa and the liquid limit, the plasticity index and the diatomaceous content, among others.展开更多
The Southern Irumide Belt(SIB)is an orogenic belt consisting of a number of lithologically varied Mesoproterozoic and Neoproterozoic terranes that were thrust upon each other.The belt lies along the southwest margin o...The Southern Irumide Belt(SIB)is an orogenic belt consisting of a number of lithologically varied Mesoproterozoic and Neoproterozoic terranes that were thrust upon each other.The belt lies along the southwest margin of the Archaean to Proterozoic Congo Craton,and bears a Neoproterozoic tectonothermal overprint relating to the Neoproterozoic-Cambrian collision between the Congo and Kalahari cratons.It preserves a record of about 500 million years of plate interaction along this part of the Congo margin.Detrital zircon samples from the SIB were analysed for U-Pb and Lu-Hf isotopes,as well as trace element compositions.These data are used to constrain sediment-source relationships between SIB terranes and other Gondwanan terranes such as the local Congo Craton and Irumide belt and wider afield to Madagascar(Azania)and India.These correlations are then used to interpret the Mesoproterozoic to Neoproterozoic affinity of the rocks and evolution of the region.Detrital zircon samples from the Chewore-Rufunsa and Kacholola(previously referred to as Luangwa-Nyimba)terranes of the SIB yield zircon U-Pb age populations and evolvedε(Hf)(t)values that are similar to the Muva Supergroup found throughout eastern Zambia,primarily correlating with Ubendian-Usagaran(ca.2.05-1.80 Ga)phase magmatism and a cryptic basement terrane that has been suggested to underlie the Bangweulu Block and Irumide Belt.These data suggest that the SIB was depositionally connected to the Congo Craton throughout the Mesoproterozoic.The more eastern Nyimba-Sinda terrane of the SIB(previously referred to as Petauke-Sinda terrane)records detrital zircon ages andε(Hf)(t)values that correlate with ca.1.1-1.0 Ga magmatism exposed elsewhere in the SIB and Irumide Belt.We ascribe this difference in age populations to the polyphase development of the province,where the sedimentary and volcanic rocks of the Nyimba-Sinda terrane accumulated in extensional basins that developed in the Neoproterozoic.Such deposition would have occurred following late-Mesoproterozoic magmatism that is widespread throughout both the Irumide and Southern Irumide Belts,presently considered to have occurred in response to collision between a possible microcontinental mass and the Irumide Belt.This interpretation implies a multi-staged evolution of the ocean south of the Congo Craton during the mid-Mesoproterozoic to late-Neoproterozoic,which ultimately closed during collision between the Congo and Kalahari cratons.展开更多
This paper presents the mechanical behaviors of the lacustrine deposit,a representative soil in Bogota,Colombia.Initially,the physical characterization of the deposit is performed via laboratory tests (grain size dist...This paper presents the mechanical behaviors of the lacustrine deposit,a representative soil in Bogota,Colombia.Initially,the physical characterization of the deposit is performed via laboratory tests (grain size distribution,scanning electron microscopy,Atterberg limits and water content).This characterization intends to explain the special characteristics of the mechanical behaviors of this soil.Then,various triaxial tests are carried out with controlled loading path,strain rate change,relaxation,extensile stress,and cyclic loading.The test results reveal the shape of the yield curve for Bogotá soil (in a natural state),and also show that an increasing effect of the strain rate depends on the liquid limit.This effect is also preserved with extensile stresses (which are poorly studied in soil mechanics).Finally,other effects,such as the loss of structure in the reconstituted samples and the effect of shear modulus at low strains,are studied for Bogota soil.展开更多
On July 19,1985,at Stava near Tesero(Italian Alps),two reservoirs collapsed,causing the death of 268 people and the destruction of many buildings.The two adjacent basins were constructed for the decantation and storag...On July 19,1985,at Stava near Tesero(Italian Alps),two reservoirs collapsed,causing the death of 268 people and the destruction of many buildings.The two adjacent basins were constructed for the decantation and storage of fine-grained waste material,which was pumped from a nearby fluorite mine.The consequence of the failure was a vast flowslide that found its way downstream along the Stava valley destroying many houses in the village of Stava,eventually reaching Tesero,where more property was wrecked or severely damaged.The Stava valley disaster was one of the most tragic of its kind.This paper aims to give a contribution on the technical aspects related to the causes of this catastrophic event.It also describes alternative technical solutions for the proper management of mining waste disposal and environmental protection proposed by the Stava 1985 Foundation for disseminating knowledge and awareness on how to make these geotechnical structures safer and more profitable and avoid other similar disasters that still keep occurring every year around the world.展开更多
文摘The paper is a summary of discussions on four topics in rockburst and dynamic ground support.Topic 1 is the mechanisms of rockburst.Rockburst events are classified into two categories in accordance with the triggering mechanisms,i.e.strain burst and fault-slip burst.Strain burst occurs on rock surfaces when the tangential stress exceeds the rock strength in hard and brittle rocks.Fault-slip burst is triggered by fault-slip induced seismicity.Topic 2 is prediction and forecasting of rockburst events.Prediction for a rockburst event must tell the location,timing and magnitude of the event.Forecasting could simply foresee the probability of some of the three parameters.It is extremely challenging to predict rockbursts and large seismic events with current knowledge and technologies,but forecasting is possible,for example the possible locations of strain burst in an underground opening.At present,the approach using seismic monitoring and numerical modelling is a promising forecasting method.Topic 3 is preconditioning methods.The current preconditioning methods are blasting,relief-hole drilling and hydrofracturing.Defusing fault-slip seismicity is difficult and challenging but has been achieved.In very deep locations(>3000 m),the fracturing could extend from the excavation face to a deep location ahead of the face and therefore preconditioning is usually not required.Topic 4 is dynamic ground support against rockburst.Dynamic ground support requires that the support system be strong enough to sustain the momentum of the ejecting rock on one hand and tough enough on the other hand to absorb the strain and seismic energies released from the rock mass.The current dynamic support systems in underground mining are composed of yielding tendons and flexible surface retaining elements like mesh/screen and straps.Yielding props and engineered timber props are also used for dynamic support.
文摘This work presents a study on the behaviors of diatomaceous soils. Although studies are rarely reported on these soils, they have been identified in Mexico City, the Sea of Japan, the northeast coast of Australia,the equatorial Pacific, and the lacustrine deposit of Bogota(Colombia), among other locations. Features of this kind of soil include high friction angle, high initial void ratio, high compressibility index, high liquid limit, and low density. Some of these features are counterintuitive from a classical soil mechanics viewpoint. To understand the geotechnical properties of the diatomaceous soil, a comprehensive experimental plan consisting of more than 2400 tests was performed, including physical tests such as grain size distribution, Atterberg limits, density of solid particles, and organic matter content; and mechanical tests such as oedometric compression tests, unconfined compression tests, and triaxial tests.Laboratory tests were complemented with scanning electron microscope(SEM) observations to evaluate the microstructure of the soil. The test results show that there is an increase in liquid limit with increasing diatomaceous content, and the friction angle also increases with increasing diatomaceous content. In addition, several practical correlations were proposed for this soil type for shear strength mobilization and intrinsic compression line. Finally, useful correlations were presented, such as the relationship between the state consistency and the undrained shear strength, the friction angle and the liquid limit, the void ratio at 100 kPa and the liquid limit, the plasticity index and the diatomaceous content, among others.
基金funded by Australian Research Council Future Fellowship#FT120100340 to A.Collinssupported by a Research Training Program scholarship
文摘The Southern Irumide Belt(SIB)is an orogenic belt consisting of a number of lithologically varied Mesoproterozoic and Neoproterozoic terranes that were thrust upon each other.The belt lies along the southwest margin of the Archaean to Proterozoic Congo Craton,and bears a Neoproterozoic tectonothermal overprint relating to the Neoproterozoic-Cambrian collision between the Congo and Kalahari cratons.It preserves a record of about 500 million years of plate interaction along this part of the Congo margin.Detrital zircon samples from the SIB were analysed for U-Pb and Lu-Hf isotopes,as well as trace element compositions.These data are used to constrain sediment-source relationships between SIB terranes and other Gondwanan terranes such as the local Congo Craton and Irumide belt and wider afield to Madagascar(Azania)and India.These correlations are then used to interpret the Mesoproterozoic to Neoproterozoic affinity of the rocks and evolution of the region.Detrital zircon samples from the Chewore-Rufunsa and Kacholola(previously referred to as Luangwa-Nyimba)terranes of the SIB yield zircon U-Pb age populations and evolvedε(Hf)(t)values that are similar to the Muva Supergroup found throughout eastern Zambia,primarily correlating with Ubendian-Usagaran(ca.2.05-1.80 Ga)phase magmatism and a cryptic basement terrane that has been suggested to underlie the Bangweulu Block and Irumide Belt.These data suggest that the SIB was depositionally connected to the Congo Craton throughout the Mesoproterozoic.The more eastern Nyimba-Sinda terrane of the SIB(previously referred to as Petauke-Sinda terrane)records detrital zircon ages andε(Hf)(t)values that correlate with ca.1.1-1.0 Ga magmatism exposed elsewhere in the SIB and Irumide Belt.We ascribe this difference in age populations to the polyphase development of the province,where the sedimentary and volcanic rocks of the Nyimba-Sinda terrane accumulated in extensional basins that developed in the Neoproterozoic.Such deposition would have occurred following late-Mesoproterozoic magmatism that is widespread throughout both the Irumide and Southern Irumide Belts,presently considered to have occurred in response to collision between a possible microcontinental mass and the Irumide Belt.This interpretation implies a multi-staged evolution of the ocean south of the Congo Craton during the mid-Mesoproterozoic to late-Neoproterozoic,which ultimately closed during collision between the Congo and Kalahari cratons.
基金Universidad Nacional de Colombia and Los Andes University in Colombia for their technical and financial support
文摘This paper presents the mechanical behaviors of the lacustrine deposit,a representative soil in Bogota,Colombia.Initially,the physical characterization of the deposit is performed via laboratory tests (grain size distribution,scanning electron microscopy,Atterberg limits and water content).This characterization intends to explain the special characteristics of the mechanical behaviors of this soil.Then,various triaxial tests are carried out with controlled loading path,strain rate change,relaxation,extensile stress,and cyclic loading.The test results reveal the shape of the yield curve for Bogotá soil (in a natural state),and also show that an increasing effect of the strain rate depends on the liquid limit.This effect is also preserved with extensile stresses (which are poorly studied in soil mechanics).Finally,other effects,such as the loss of structure in the reconstituted samples and the effect of shear modulus at low strains,are studied for Bogota soil.
文摘On July 19,1985,at Stava near Tesero(Italian Alps),two reservoirs collapsed,causing the death of 268 people and the destruction of many buildings.The two adjacent basins were constructed for the decantation and storage of fine-grained waste material,which was pumped from a nearby fluorite mine.The consequence of the failure was a vast flowslide that found its way downstream along the Stava valley destroying many houses in the village of Stava,eventually reaching Tesero,where more property was wrecked or severely damaged.The Stava valley disaster was one of the most tragic of its kind.This paper aims to give a contribution on the technical aspects related to the causes of this catastrophic event.It also describes alternative technical solutions for the proper management of mining waste disposal and environmental protection proposed by the Stava 1985 Foundation for disseminating knowledge and awareness on how to make these geotechnical structures safer and more profitable and avoid other similar disasters that still keep occurring every year around the world.
