scholarly journals Process of overburden failure in steeply inclined multi-seam mining: insights from physical modelling

2021 ◽  
Vol 8 (5) ◽  
pp. 210275
Author(s):  
Hai Wang ◽  
Yan Qin ◽  
Hanbin Wang ◽  
Yu Chen ◽  
Xuancheng Liu
Keyword(s):  
Rock Mass ◽  
Failure Process ◽  
Ground Surface ◽  
Physical Modelling ◽  
Surface Damage ◽  
Small Scale ◽  
Physical Model Test ◽  
Displacement Effect ◽  
Movement Mechanism ◽  
Seam Mining

Ground surface damage caused by steeply inclined coal seam mining is widely distributed in China, but there is little research on the failure process and movement mechanism of strata induced by steeply inclined multi-seam mining. In this paper, a physical model test is carried out to study the failure process and movement mechanism of overburden in steeply inclined multi-seam stepwise mining. The results show that at the initial stage, the main failure of the rock mass is the small-scale collapse at the initial cut and the roof (stability stage of the rock mass). After the roof is exposed over a certain range, the rock mass in the downhill direction slips into the goaf and gradually destroys the interburdens of the goaf, similar to the displacement effect of dominoes (severe failure stage of the rock mass). When the structure of the goaf fails, the overburden subsides, causing extensive damage to the ground surface. The surface damage directly above the goaf is mainly caused by serious subsidence deformation, while the surface damage in the downhill direction is dominated by cracks.

scholarly journals Strata Movement and Fracture Propagation Characteristics due to Sequential Extraction of Multiseam Longwall Panels

2018 ◽  
Vol 2018 ◽  
pp. 1-17 ◽  
Author(s):  
Xiangyang Zhang ◽  
Behrooz Ghabraie ◽  
Gang Ren ◽  
Min Tu
Keyword(s):  
Longwall Mining ◽  
Water Inrush ◽  
Ground Surface ◽  
Fracture Propagation ◽  
Physical Modelling ◽  
Propagation Characteristics ◽  
Gas Drainage ◽  
Strata Deformation ◽  
Seam Mining ◽  
Vertical Subsidence

Multiseam longwall mining-induced strata deformation and fracture propagation patterns are different from those of single-seam mining. This difference is due to interaction of the caved zones as a result of longwall mining activity at different coal seams, which severely impacts formation of subsidence and permeability of the strata after multiseam mining. Understanding this phenomenon is of great importance in order to predict the multiseam subsidence reliably, evaluate the risk of water inrush and take suitable preventive measures, and determine suitable locations for placing gas drainage boreholes. In this study, scaled physical modelling techniques are utilised to investigate strata deformation, fracture propagation characteristics, and vertical subsidence above multiseam longwall panels. The results show that magnitude of the incremental multiseam subsidence increases significantly after multiseam extraction in comparison with single-seam mining. This increase occurs to different extent depending on the multiseam mining configuration. In addition, interstrata fractures above the abutment areas of the overlapping panels propagate further towards the ground surface in multiseam extractions compared with single-seam extractions. These fractures increase the risk of water inrush in presence of underground/surface water and create highly permeable areas suitable for placing gas drainage boreholes.

scholarly journals Changes in ground deformation prior to and following a large urban landslide in La Paz, Bolivia revealed by advanced InSAR

2018 ◽  
Author(s):  
Nicholas J. Roberts ◽  
Bernhard T. Rabus ◽  
John J. Clague ◽  
Reginald L. Hermanns ◽  
Marco-Antonio Guzmán ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Ground Surface ◽  
Slope Instability ◽  
Small Scale ◽  
Spatial And Temporal Patterns ◽  
La Paz ◽  
Fine Grained ◽  
Measured Displacement ◽  
Optical Satellite Images ◽  
Displacement Patterns

Abstract. We characterize and compare creep preceding and following the 2011 Pampahasi landslide (∼ 40 Mm3 ± 50 %) in the city of La Paz, Bolivia, using spaceborne RADAR interferometry (InSAR) that combines displacement records from both distributed and point scatterers. The failure remobilised deposits of an ancient landslide in weakly cemented, predominantly fine-grained sediments and affected ∼ 1.5 km2 of suburban development. During the 30 months preceding failure, about half of the toe area was creeping at 3–8 cm/a and localized parts of the scarp area showed displacements of up to 14 cm/a. Changes in deformation in the 10 months following the landslide are contrary to the common assumption that stress released during a discrete failure increases stability. During that period, most of the landslide toe and areas near the headscarp accelerated, respectively, to 4–14 and 14 cm/a. The extent of deformation increased to cover most, or probably all, of the 2011 landslide as well as adjacent parts of the slope and plateau above. The InSAR-measured displacement patterns – supplemented by field observations and by optical satellite images – indicate that kinematically complex, steady-state creep along pre-existing sliding surfaces temporarily accelerated in response to heavy rainfall, after which the slope quickly achieved a slightly faster and expanded steadily creeping state. This case study demonstrates that high-quality ground-surface motion fields derived using spaceborne InSAR can help to characterize creep mechanisms, quantify spatial and temporal patterns of slope activity, and identify isolated small-scale instabilities. Characterizing slope instability before, during, and after the 2011 Pampahasi landslide is particularly important for understanding landslide hazard in La Paz, half of which is underlain by similar, large paleolandslides.

Model Test Study on Influences of Layered Rock Mass Dip Angle on Stability of Deep-Buried Tunnel

2011 ◽  
Vol 90-93 ◽  
pp. 2363-2371
Author(s):  
Bin Wei Xia ◽  
Ke Hu ◽  
Yi Yu Lu ◽  
Dan Li ◽  
Zu Yong Zhou
Keyword(s):  
Rock Mass ◽  
Physical Model ◽  
Model Test ◽  
Physical Models ◽  
Physical Model Test ◽  
Stress Distributions ◽  
Failure Characteristics ◽  
Layered Rock ◽  
Layered Rock Mass ◽  
Dip Angle

Physical models of layered rock mass with different dip angles are built by physical model test in accordance with the bias failure characteristics of surrounding rocks of layered rock mass in Gonghe Tunnel. Bias failure characteristics of surrounding rocks in thin-layered rock mass and influences of layered rock mass dip angle on stability of tunnel are studied. The research results show that failure characteristics of physical models generally coincide with those of surrounding rocks monitored from the tunnel site. The failure regions of surrounding rock perpendicular to the stratification planes are obviously larger than those parallel to. The stress distributions and failure characteristics in the surrounding rocks are similar to each physical model of different dip angles. The stress distributions and failure regions are all elliptic in shape, in which the major axis is in the direction perpendicular to the stratification planes while the minor axis is parallel to them. As a result, obvious bias failure of surrounding rocks has gradually formed. The physical model tests provide reliable basis for theoretical analysis on the failure mechanism of deep-buried layered rock mass.

Type of Slope Failure Identified from Pore Water Pressure and Moisture Content Measurements

2015 ◽  
Vol 744-746 ◽  
pp. 690-694
Author(s):  
Muhammad Rehan Hakro ◽  
Indra Sati Hamonangan Harahap
Keyword(s):  
Moisture Content ◽  
Pore Pressure ◽  
Slope Failure ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Failure Process ◽  
Small Scale ◽  
Content Increase ◽  
Sudden Increase ◽  
Model Slope

Rainfall-induced landslides occur in many parts of the world and causing a lot of the damages. For effective prediction of rainfall-induced landslides the comprehensive understanding of the failure process is necessary. Under different soil and hydrological conditions experiments were conducted to investigate and clarify the mechanism of slope failure. The failure in model slope was induced by sprinkling the rainfall on slope composed of sandy soil in small flume. Series of tests were conducted in small scale flume to better understand the failure process in sandy slopes. The moisture content was measured with advanced Imko TDR (Time Domain Reflectrometry) moisture sensors in addition to measurements of pore pressure with piezometers. The moisture content increase rapidly to reach the maximum possible water content in case of higher intensity of rainfall, and higher intensity of the rainfall causes higher erosion as compared to smaller intensity of the rainfall. The controlling factor for rainfall-induced flowslides was density of the slope, rather than intensity of the rainfall and during the flowslide the sudden increase in pore pressure was observed. Higher pore pressure was observed at the toe of the slope as compared to upper part of the slope.

Numerical Study on Influence of Joint Characters on Rock Mechanical Parameters

2011 ◽  
Vol 201-203 ◽  
pp. 2909-2912
Author(s):  
Yan Feng Feng ◽  
Tian Hong Yang ◽  
Hua Wei ◽  
Hua Guo Gao ◽  
Jiu Hong Wei
Keyword(s):  
Rock Mass ◽  
Compression Strength ◽  
Numerical Study ◽  
Process Analysis ◽  
Failure Process ◽  
Deformation Modulus ◽  
Rock Joints ◽  
Structured Surfaces ◽  
Trace Length ◽  
The Impact

Rock mass is the syntheses composed of kinds of structure and structured surfaces. The joint characters is influencing and controlling the rock mass strength, deformation characteristics and rock mass engineering instability failure in a great degree. Through using the RFPA2D software, which is a kind of material failure process analysis numerical methods based on finite element stress analysis and statistical damage theory, the uniaxial compression tests on numerical model are carried, the impact of the trace length of rock joints and the fault throws on rock mechanics parameters are studied. The results showed that with the gradual increase of trace length,compression strength decreased gradually and its rate of variation getting smaller and smaller, the deformation modulus decreased but the rate of variation larger and larger; with the fault throws increasing, the compression strength first increases and then decreases, when the fault throw is equal to the trace length, the deformation modulus is the largest. When the joint trace length is less than the fault throw, the rate of the deformation modulus is greater than that of trace length, but the deformation modulus was not of regular change.

scholarly journals Changes in ground deformation prior to and following a large urban landslide in La Paz, Bolivia, revealed by advanced InSAR

2019 ◽  
Vol 19 (3) ◽  
pp. 679-696 ◽  
Author(s):  
Nicholas J. Roberts ◽  
Bernhard T. Rabus ◽  
John J. Clague ◽  
Reginald L. Hermanns ◽  
Marco-Antonio Guzmán ◽  
...  
Keyword(s):  
Ground Deformation ◽  
Ground Surface ◽  
Small Scale ◽  
Spatial And Temporal Patterns ◽  
La Paz ◽  
Fine Grained ◽  
Measured Displacement ◽  
Optical Satellite Images ◽  
Displacement Patterns ◽  
Spaceborne Radar

Abstract. We characterize and compare creep preceding and following the complex 2011 Pampahasi landslide (∼40 Mm3±50 %) in the city of La Paz, Bolivia, using spaceborne radar interferometry (InSAR) that combines displacement records from both distributed and point scatterers. The failure remobilized deposits of an ancient complex landslide in weakly cemented, predominantly fine-grained sediments and affected ∼1.5 km2 of suburban development. During the 30 months preceding failure, about half of the toe area was creeping at 3–8 cm a−1 and localized parts of the scarp area showed displacements of up to 14 cm a−1. Changes in deformation in the 10 months following the landslide demonstrate an increase in slope activity and indicate that stress redistribution resulting from the discrete failure decreased stability of parts of the slope. During that period, most of the landslide toe and areas near the head scarp accelerated, respectively, to 4–14 and 14 cm a−1. The extent of deformation increased to cover most, or probably all, of the 2011 landslide as well as adjacent parts of the slope and plateau above. The InSAR-measured displacement patterns, supplemented by field observations and optical satellite images, reveal complex slope activity; kinematically complex, steady-state creep along pre-existing sliding surfaces accelerated in response to heavy rainfall, after which slightly faster and expanded steady creeping was re-established. This case study demonstrates that high-quality ground-surface motion fields derived using spaceborne InSAR can help to characterize creep mechanisms, quantify spatial and temporal patterns of slope activity, and identify isolated small-scale instabilities; such details are especially useful where knowledge of landslide extent and activity is limited. Characterizing slope activity before, during, and after the 2011 Pampahasi landslide is particularly important for understanding landslide hazard in La Paz, half of which is underlain by similar large paleolandslides.

Model Testing and Analysis Study on Shear Strength of Rock Mass Containing Multiple Cracks under Compression-Shearing Loading

2008 ◽  
Vol 33-37 ◽  
pp. 617-622
Author(s):  
Wei Shen Zhu ◽  
Bin Sui ◽  
Wen Tao Wang ◽  
Shu Cai Li
Keyword(s):  
Shear Strength ◽  
Rock Mass ◽  
Rock Sample ◽  
Failure Process ◽  
Jointed Rock ◽  
Multiple Cracks ◽  
Test Results ◽  
Failure Model ◽  
Two Phase ◽  
Bridge Failure

Two-phase modelling testing was performed to study the shear strength of rock bridges of jointed rock mass in this paper. The failure process of rock sample containing multiple collinear cracks was observed. Based on theory of fracture mechanics and analytical method, a rock-bridge failure model was proposed and the expression of shear strength was derived. Comparison of calculated shear strength and the model test results was made and they agree well.

Microstructure Evolution During Alternating-Current-Induced Fatigue

Materials ◽  
2004 ◽  
Author(s):  
R. R. Keller ◽  
R. H. Geiss ◽  
Y.-W. Cheng ◽  
D. T. Read
Keyword(s):  
Electron Backscatter Diffraction ◽  
Failure Process ◽  
Low Frequency ◽  
Surface Damage ◽  
Alternating Current ◽  
Fiber Texture ◽  
Electrical Failure ◽  
Damage Process ◽  
Current Densities ◽  
Interconnect Lines

Subjecting electronic interconnect lines to high-density, low-frequency alternating current creates cyclic thermomechanical stresses that eventually cause electrical failure. A detailed understanding of the failure process could contribute to both prevention and diagnostics. We tested unpassivated Al-1Si traces on the NIST-2 test chip; these are 3.5 μm wide by 0.5 μm thick by 800 μm long, with a strong (111) as-deposited fiber texture and an initial average grain diameter of approximately 1 μm. We applied rms current densities of 11.7 to 13.2 MA/cm2 at 100 Hz. Resistance changes in the lines indicated that such current densities produce temperature cycles at 200 Hz with amplitude exceeding 100 K. Open circuits occurred in under 10 minutes, with substantial surface damage seen after only one minute. A few failures initiated at lithography defects initially present in the lines, but most were produced by the current alone. In one detailed example presented in this paper, we monitored the damage process by interrupting the current at 10, 20, 40, 80, 160, and 320 s in order to characterize an entire line by scanning electron microscopy and automated electron backscatter diffraction (EBSD); failure took place after 697 s. Results are described in terms of deformation, grain growth, and orientation changes.

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