scholarly journals Mining-Induced Failure Criteria of Interactional Hard Roof Structures: A Case Study

Energies ◽  
2019 ◽  
Vol 12 (15) ◽  
pp. 3016 ◽  
Author(s):  
Shen ◽  
Wang ◽  
Cao ◽  
Su ◽  
Nan ◽  
...  
Keyword(s):  
Mechanical Behavior ◽  
Longwall Mining ◽  
Underground Mining ◽  
Failure Criteria ◽  
Normal Operation ◽  
Analysis Model ◽  
Plane Stress Condition ◽  
Field Case ◽  
Hard Roof ◽  
Soft Interlayer

Due to the additional abutment stress, interactional hard roof structures (IHRS) affect the normal operation of the coal production system in underground mining. The movement of IHRS may result in security problems, such as the failure of supporting body, large deformation, and even roof caving for nearby openings. According to the physical configuration and loading conditions of IHRS in a simple two-dimensional physical model under the plane stress condition, mining-induced failure criteria were proposed and validated by the mechanical behavior of IHRS in a mechanical analysis model. The results indicate that IHRS, consisting of three interactional parts—the lower key structure, the middle soft interlayer, and the upper key structure—are governed by the additional abutment stress induced by the longwall mining working face. The fracture of the upper key structure in IHRS can be explained as follows: Due to the crushing failure, lower key structure, and middle soft interlayer yield, the action force between the upper and lower key structures vanishes, resulting in fracture of the upper key structure in IHRS. In a field case, when additional abutment stress reaches 7.37 MPa, the energy of 2.35 × 105 J is generated by the fracture of the upper key structure in IHRS. Under the same geological and engineering conditions, the energy generated by IHRS is much larger than that generated by a single hard roof. The mining-induced failure criteria are successfully applied in a field case. The in-situ mechanical behavior of the openings nearby IHRS under the mining abutment stress can be clearly explained by the proposed criteria.

scholarly journals Study on the Fracture Law of Inclined Hard Roof and Surrounding Rock Control of Mining Roadway in Longwall Mining Face

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5344
Author(s):  
Feng Cui ◽  
Shuai Dong ◽  
Xingping Lai ◽  
Jianqiang Chen ◽  
Chong Jia ◽  
...  
Keyword(s):  
Energy Release ◽  
Longwall Mining ◽  
Coal Pillar ◽  
High Energy ◽  
Mechanical Analysis ◽  
Engineering Practice ◽  
Analysis Model ◽  
Hard Roof ◽  
Working Face ◽  
The Stability

In the inclination direction, the fracture law of a longwall face roof is very important for roadway control. Based on the W1123 working face mining of Kuangou coal mine, the roof structure, stress and energy characteristics of W1123 were studied by using mechanical analysis, model testing and engineering practice. The results show that when the width of W1123 is less than 162 m, the roof forms a rock beam structure in the inclined direction, the floor pressure is lower, the energy and frequency of microseismic (MS) events are at a low level, and the stability of the section coal pillar is better. When the width of W1123 increases to 172 m, the roof breaks along the inclined direction, forming a double-hinged structure, the floor pressure is increased, and the frequency and energy of MS events also increases. The roof gathers elastic energy release, and combined with the MS energy release speed it can be considered that the stability of the section coal pillar is better. As the width of W1123 increases to 184 m, the roof in the inclined direction breaks again, forming a multi-hinged stress arch structure, and the floor pressure increases again. MS high-energy events occur frequently, and are not conducive to the stability of the section coal pillar. Finally, through engineering practice we verified the stability of the section coal pillar when the width of W1123 was 172 m, which provides a basis for determining the width of the working face and section coal pillar under similar conditions.

scholarly journals Surface Subsidence Prognosis above an Underground Longwall Excavation and Based on 3D Point Cloud Analysis

Minerals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 82 ◽  
Author(s):  
Andrej Pal ◽  
Janez Rošer ◽  
Milivoj Vulić
Keyword(s):  
Rock Mass ◽  
Longwall Mining ◽  
Underground Mining ◽  
Point Clouds ◽  
Surface Subsidence ◽  
Protection Measures ◽  
Engineering Research ◽  
3D Point Clouds ◽  
Research Activities ◽  
And Control

Impacts of underground mining have been reduced by continuous environmental endeavors, scientific, and engineering research activities, whose main object is the behavior and control of the undermined rock mass and the subsequent surface subsidence. In the presented Velenje case of underground sublevel longwall mining where coal is being exploited both horizontal and vertical, backfilling processes and accompanying fracturing in the coal layer, and rock mass are causing uncontrolled subsidence of the surface above. 3D point clouds of the study were acquired in ten epochs and at excavation heights on the front were measured at the same epochs. By establishing a sectors layout in the observational area, smaller point clouds were obtained, to which planes were fitted and centroids of these planes then calculated. Centroid heights were analyzed with the FNSE model to estimate the time of consolidation and modified according to excavation parameters to determine total subsidence after a certain period. Proposed prognosis approaches for estimating consolidation of active subsidence and long term surface environmental protection measures have been proposed and presented. The C2C analysis of distances between acquired 3D point clouds was used for identification of surface subsidence, reclamation areas and sink holes, and for validation of feasibility and effectiveness of the proposed prognosis.

Reliability-Based Factors of Safety for Vortex Induced Vibration Fatigue Using Field Measurements

2013 ◽  
Vol 135 (4) ◽  
Author(s):  
Michael Tognarelli ◽  
Emmanuel Fontaine ◽  
Pierre Beynet ◽  
Mikhail Santosa ◽  
Hayden Marcollo
Keyword(s):  
Prediction Models ◽  
Deterministic Model ◽  
State Of The Art ◽  
Limit State ◽  
Field Measurements ◽  
Failure Criteria ◽  
State Function ◽  
Analysis Model ◽  
Vortex Induced Vibration ◽  
Vibration Fatigue

The development of a vortex induced vibration (VIV) fatigue factor of safety (FoS) consistent with state-of-the-art industry design practice is cast within the coherent framework of reliability analysis. The proposed methodology consists of the following steps: (i) define the failure criteria or limit-state function (ii) setup a deterministic analysis model (iii) characterize the uncertainties involved in the problem (iv) propagate the uncertainties through the deterministic model and assess the probability of failure due to VIV fatigue and (v) calculate the FoS required to achieve a given failure probability. The proposed methodology is demonstrated by determining the FoS associated with using state-of-the-art VIV prediction models to attain varying reliability levels (probabilities of failure) in a hypothetical design scenario. Prediction uncertainty is based herein on measured flow and response data for several full-scale drilling risers working in the field. Results indicate that depending on the reliability level required of a particular design, different FoS than those that currently appear in guidance may be appropriate. Results also indicate the sensitivity of the FoS to the riser and prevailing current type, analysis program and input parameters, and accumulation of conservatism in aggregate versus single-event damage predictions.

scholarly journals Analysis of different failure criteria to evaluate bauxite tailings mechanical behavior through numerical modelling

2021 ◽  
Vol 44 (1) ◽  
pp. 1-10
Author(s):  
Giovani Jordi Bruschi ◽  
Fernando Fante ◽  
Mariana Tonini de Araújo ◽  
Gustavo Dias Macedo ◽  
Cesar Alberto Ruver
Keyword(s):  
Numerical Modelling ◽  
Mechanical Behavior ◽  
Failure Criteria ◽  
Bauxite Tailings

scholarly journals Assessments of land subsidence along Rizhao-Lankao High-speed Railway at Heze, China between 2015 and 2019 with Sentinel-1 data

2020 ◽  
Author(s):  
Chuanguang Zhu ◽  
Wenhao Wu ◽  
Mahdi Motagh ◽  
Liya Zhang ◽  
Zongli Jiang ◽  
...  
Keyword(s):  
Land Subsidence ◽  
High Speed ◽  
Underground Mining ◽  
Ground Deformation ◽  
Ground Subsidence ◽  
Normal Operation ◽  
Monthly Precipitation ◽  
High Speed Railway ◽  
Subsidence Area ◽  
Under Construction

Abstract. The Heze section of Rizhao-Lankao High-speed Railway (RLHR-HZ) has been under construction since 2018 and will be operative by the end of 2021. However, there is a concern that land subsidence in Heze region may affect the normal operation of RLHR-HZ. In this study, we investigate the contemporary ground deformation in the region between 2015 and 2019 by using more than 350 C-band interferograms constructed from two tracks of Sentine-1 data over the region. The Small Baselines Subset (SBAS) technique is adopted to compile the time series displacement. We find that the RLHR-HZ runs through two main subsidence areas: One is located east of Heze region with rates ranging from −4 cm/yr to −1 cm/yr, and another one is located in the coal field with rates ranging from −8 cm/yr to −2 cm/yr. A total length of 35 km of RLSR-HZ are affected by the two subsidence basins. Considering the previous investigation and the monthly precipitation, we infer that the subsidence bowl east of Heze region is due to massive extraction of deep groundwater. Close inspections of the relative locations between the second subsidence area and the underground mining reveals that the subsidence there is probably caused by the groundwater outflow and fault instability due to mining, rather than being directly caused by mining. The InSAR-derived ground subsidence implies that it's necessary to continue monitoring the ground deformation along RLSR-HZ.

scholarly journals A Comprehensive Method for Subsidence Prediction on Two-Seam Longwall Mining

Energies ◽  
2019 ◽  
Vol 12 (16) ◽  
pp. 3139 ◽  
Author(s):  
Bin Zhang ◽  
Jiacheng Ye ◽  
Zhongjian Zhang ◽  
Liang Xu ◽  
Nengxiong Xu
Keyword(s):  
Longwall Mining ◽  
Underground Mining ◽  
Surface Subsidence ◽  
Orthogonal Experimental Design ◽  
Parameter Inversion ◽  
Subsidence Prediction ◽  
Reliable Assessment ◽  
Seam Mining ◽  
Subsidence Monitoring ◽  
Overlying Strata

The purpose of mining subsidence prediction is to establish a reliable assessment for surface subsidence resulting from underground mining. In this study, a new method for predicting subsidence in two-seam mining is proposed. First, the surface subsidence due to mining the upper seam is monitored. Then, taking the subsidence data as indicators, the optimal mechanical parameters of overlying strata can be obtained by orthogonal experimental design and inverse analysis of numerical simulation. Finally, further subsidence is calculated and predicted by the numerical model. A case of two-seam underground mining is studied using this methodology. This coal mine is located in the Dongsheng coal field in Inner Mongolia, China. Based on GPS surface subsidence monitoring and parameter inversion, the subsidence induced by two-seam mining is estimated and predicted. This study shows that the ratio of the height of overlying strata to mining thickness (H/M), mining configuration and adjacent mining have a significant effect on the surface subsidence caused by two-seam mining. By parameter inversion, the proposed optimal parameters can be applied to predict the subsidence of a nearby mine with similar stratigraphic conditions. Furthermore, this methodology can also be used to predict the subsidence caused by mining of more than two seams.

Mechanical Behavior Evaluation of a Nickel-Aluminum Bronze Alloy Weld with Micro Indentation Method

2017 ◽  
Vol 734 ◽  
pp. 293-300
Author(s):  
De Lin Rao ◽  
Yin Zhong Shen
Keyword(s):  
Mechanical Behavior ◽  
Calculation Model ◽  
Aluminum Bronze ◽  
Nickel Aluminum ◽  
Analysis Model ◽  
Bronze Alloy ◽  
Base Materials ◽  
Nickel Aluminum Bronze ◽  
Micro Indentation ◽  
Alloy Weld

In this research, the mechanical behavior of a multi-pass nickel-aluminum bronze alloy weld joint is investigated. Macro-tensile testing shows the mechanical behavior difference of the weld and base materials. Micro indentation data is applied to calculate the local mechanical properties in a multi-pass weld and base materials. The indentation loading-unloading cycle and stress-strain calculation model are introduced in the paper. It shows that the micro indentation results are in good agreement with the macro-tensile test data. Both the micro structure and uncertainties within the analysis model affect the discrepancy of two testing methods.

Ground surface subsidence as effect of underground mining of the thick coal seams in the Jiu valley basin / Osiadanie gruntów wskutek wybierania pokładów o dużej miąższości w kopalniach zagłębia w dolinie Jiu

2012 ◽  
Vol 57 (3) ◽  
pp. 547-577 ◽  
Author(s):  
Ilie Onica ◽  
Dacian Marian
Keyword(s):  
Surface Deformation ◽  
Longwall Mining ◽  
Underground Mining ◽  
Ground Surface ◽  
Surface Subsidence ◽  
Coal Seams ◽  
Elasto Plasticity ◽  
Ground Surface Subsidence ◽  
Time Dependent Analysis

Abstract In the case of the thick and gentle coal seam no. 3 of the Jiu Valley Coal Basin (Romania), the mining methods are by use of the longwall mining technologies with roof control by caving or top coal caving. In this paper, it is presented the analysis of the complex deformations of the ground surface, over time, as a consequence of the coal mining in certain mining fields of the basin. Also, it is analysed the ground surface subsidence phenomenon using the CESAR-LCPC finite element code. The modelling is made in the elasticity and the elasto-plasticity behaviour hypothesis. Also, the time dependent analysis of the ground surface deformation was achieved with the aid of an especial profile function. The obtained results are compared with the in situ measurements data basis.

scholarly journals Roof Weakening of Hydraulic Fracturing for Control of Hanging Roof in the Face End of High Gassy Coal Longwall Mining: A Case Study

2016 ◽  
Vol 61 (3) ◽  
pp. 601-615 ◽  
Author(s):  
Bingxiang Huang ◽  
Youzhuang Wang
Keyword(s):  
High Pressure ◽  
Hydraulic Fracturing ◽  
Longwall Mining ◽  
Roof Rock ◽  
Water Pressure ◽  
Small Diameter ◽  
Mining District ◽  
Drilling Depth ◽  
Hard Roof ◽  
The Face

Abstract The occurence of hanging roof commonly arises in the face end of longwall coal mining under hard roof conditions. The sudden break and subsequent caving of a hanging roof could result in the extrusion of gas in the gob to the face, causing gas concentrations to rise sharply and to increase to over a safety-limited value. A series of linear fracturing-holes of 32 mm diameter were drilled into the roof of the entries with an anchor rig. According to the theory that the gob should be fully filled with the fragmentized falling roof rock, the drilling depth is determined as being 3~5 times the mining height if the broken expansion coefficient takes an empirical value. Considering the general extension range of cracks and the supporting form of the entryway, the spacing distance between two drilling holes is determined as being 1~2 times the crack’s range of extension. Using a mounting pipe, a high pressure resistant sealing device of a small diameter-size was sent to the designated location for the high-pressure hydraulic fracturing of the roof rock. The hydraulic fracturing created the main hydro-fracturing crack and airfoil branch cracks in the interior of the roof-rock, transforming the roof structure and weakening the strength of the roof to form a weak plane which accelerated roof caving, and eventually induced the full caving in of the roof in time with the help of ground pressure. For holes deeper than 4 m, retreating hydraulic fracturing could ensure the uniformity of crack extension. Tested and applied at several mines in Shengdong Mining District, the highest ruptured water pressure was found to be 55 MPa, and the hanging roof at the face end was reduced in length from 12 m to less than 1~2 m. This technology has eliminated the risk of the extrusion of gas which has accumulated in the gob.

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