scholarly journals Mechanism of Coal Bursts Induced by Horizontal Section Mining of Steeply Inclined Coal Seams and Application of Microseismic Multiparameter Monitoring in Early Warning

2020 ◽  
Vol 2020 ◽  
pp. 1-14
Author(s):  
Sheng-Chuan Wang ◽  
Lin-Ming Dou ◽  
Zheng-Yi Wang ◽  
Jin-Zheng Bai ◽  
Yan-Jiang Chai
Keyword(s):  
Seismic Tomography ◽  
High Sensitivity ◽  
Propagation Distance ◽  
Static Stress ◽  
Dynamic Loads ◽  
Coal Seams ◽  
Horizontal Section ◽  
Static Loads ◽  
Coal Bursts ◽  
Precursory Information

Coal bursts occurring in steeply inclined coal seams (SICSs) are increasingly severe. To solve this problem, a mechanical model for the distribution of static stress on coal-rock masses along panels and the distribution of dynamic load induced by the breakage of thick and hard roofs with propagation distance was established. The stress characteristics after a superposition of dynamic and static loads on the roof and floor roadways (Rr and Rf) were determined. In addition, precursory information characteristics and index sensitivities of four indices for dynamic loads and the CT index for static loads based on seismic tomography were separately analyzed. The monitoring and warning indices for SICSs and flat seams were compared. The results showed that the static stress of Rr was significantly higher than that of Rf, which provided a basis for the stress-triggering coal burst behaviors. Three indices for dynamic loads and seismic tomography results exhibited remarkable precursory information and high sensitivity. However, the performance of lack of shock index is poor. The continuous anomaly and the contradiction of indices at Rr and Rf can be considered as precursory information for predicting coal bursts.

scholarly journals Mechanisms of Rock Burst in Horizontal Section Mining of a Steeply Inclined Extra-Thick Coal Seam and Prevention Technology

Energies ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 6043
Author(s):  
Jinrong Cao ◽  
Linming Dou ◽  
Guangan Zhu ◽  
Jiang He ◽  
Shengchuan Wang ◽  
...  
Keyword(s):  
Distinct Element ◽  
Field Measurements ◽  
Field Studies ◽  
Static Stress ◽  
Dynamic Loads ◽  
Horizontal Section ◽  
Thick Coal Seam ◽  
Rock Bursts ◽  
Universal Distinct Element Code ◽  
Distinct Element Code

Rock bursts have recently become a serious problem in the horizontal section mining of steeply inclined extra-thick coal seams (SIETCSs). However, few studies have been carried out to investigate their mechanisms and prevention. In this study, numerical simulation and field measurements were carried out to investigate the mechanism of rock bursts in the horizontal section mining of an SIETCS. A Universal Distinct Element Code (UDEC) Trigon model was built, based on the Yaojie No.3 Coal Mine, and calibrated through laboratory tests and RQD methods. The results demonstrate that the coal in the elastic zone around the roof is in a high static stress state, due to the asymmetric clamping and squeezing of the roof and floor. Strong dynamic loads are formed by breakage of the roof and the failure of multiple hinged beam structures during the evolution process of the overlying strata. Rock bursts occur on the roof side when the superimposition of the static stress σs and stress increment σd induced by such dynamic loads is greater than the critical stress σmin of the coal and rock. We propose a technical prevention scheme for the considered mine. Field studies suggest that the proposed technology can effectively prevent and control rock bursts in the horizontal section mining of SIETCSs.

scholarly journals Coal Burst Induced by Horizontal Section Mining of a Steeply Inclined, Extra-Thick Coal Seam and Its Prevention: A Case Study from Yaojie No. 3 Coal Mine, China

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Zhengyi Wang ◽  
Linming Dou ◽  
Guifeng Wang
Keyword(s):  
Coal Mine ◽  
Dynamic Load ◽  
Abutment Pressure ◽  
Static Load ◽  
Horizontal Section ◽  
Static Loads ◽  
Thick Coal Seam ◽  
Working Face ◽  
Limiting Load ◽  
Coal Bursts

At present, coal bursts in working faces of steeply inclined coal seams (SICSs) have rarely been investigated, and current research focuses on the influences of roof breaking and instability of overlying structures in goaf on coal bursts; however, the stress state of coal masses in working faces being subjected to coal bursts is rarely researched. To overcome the above defects, a model for analysing stresses on coal masses in horizontal section of SICSs was established based on the coal burst that occurred in LW5521-20, Yaojie No. 3 Coal Mine, Lanzhou, Gansu Province, China. Moreover, the mechanism underpinning such a coal burst in SICSs was analysed based on the superposition mechanism of dynamic and static loads. The results show that the side abutment pressure near the roof and floor under the horizontal sections of SICSs is asymmetrically distributed in the vertical direction in which the peak of side abutment pressure near the roof is closer to the working face and therefore is taken as the source of static loads for coal bursts in working faces. When the superimposed dynamic load caused by hanging roof breaking and high static load borne in the coal masses is larger than the critical load for coal burst inception, a coal burst will occur. Furthermore, the superimposed dynamic load induced by coal bursts on the support and the initial static load on the supports are larger than their limiting load, which leads to support collapse and eventually causes dynamic failure of the working face. The coal burst in working faces in horizontal sections of SICSs can be prevented by using deep-hole presplit blasting in a hard roof, destress blasting in coal masses, and support optimisation of working faces, showing a favourable preventative effect.

scholarly journals Study on Roof Breakage-Induced Roadway Coal Burst in an Extrathick Steeply Inclined Coal Seam

2019 ◽  
Vol 2019 ◽  
pp. 1-14 ◽  
Author(s):  
Sheng-chuan Wang ◽  
Lin-ming Dou ◽  
Zong-long Mu ◽  
Jin-rong Cao ◽  
Xu-wei Li
Keyword(s):  
Coal Seam ◽  
Dominant Role ◽  
High Energy ◽  
Static Stress ◽  
Dynamic Loads ◽  
Response Characteristics ◽  
Hard Roof ◽  
Model And Simulation ◽  
Before And After ◽  
Coal Bursts

In view of the coal burst induced by roof breakage in the steeply inclined coal seam (SICS) roadway and its mechanism, a mechanical model was established to investigate the distribution of dynamic and static stresses in the coal seam before and after the breakage of a thick hard roof. The aim of this research is to study failure laws of SICS roadways under the superposition of dynamic load induced by roof breakage and asymmetric static load. For this purpose, response characteristics including acoustic emission (AE), static stress, and acceleration were analyzed by applying different dynamic loads to different horizontal slices with a self-made similarity simulation test apparatus under combined dynamic and static loads. The theoretical model and simulation results were verified by analyzing characteristics of coal burst occurrence in the field, microseismic (MS) events, and tomographic imaging of microseismic waves. The study demonstrates the following: (1) The abutment pressure of the roof plays a dominant role in stress distribution of the coal seam slice before the breakage of the thick hard roof with the stress of the roof roadway (Rr) being obviously higher than that of the floor roadway (Rf). (2) High-energy MS events and AE events are concentrated on the roof side after the breakage of the thick hard roof, and coal bursts are more easily induced by the superposition of high dynamic and static stresses on the roof side. Coal burst in the roadway is jointly determined by dynamic and static stresses. Under the same static stress, response characteristics increase with the rise of intensity of dynamic loads. When dynamic stress is the same, coal burst easily occurs in the roadway with high static stress.

The Mechanical Properties Comparative Analysis for Socked and Non-Socketed Composite Pile

2014 ◽  
Vol 1061-1062 ◽  
pp. 748-750
Author(s):  
Heng Chen ◽  
Ke Sheng Ma
Keyword(s):  
Mechanical Properties ◽  
Comparative Analysis ◽  
Seismic Performance ◽  
Dynamic Loads ◽  
Vertical Load ◽  
Interlayer Thickness ◽  
Static Loads ◽  
Soil Stress ◽  
Composite Pile ◽  
Static And Dynamic Loads

For socked and non-socketed piles in the different mechanical behavior under static and dynamic loads, the paper use ABAQUS to model, simulate the pile , the soil interlayer thickness between the bottom of the pile and bedrock are 2m, 4m under vertical load and Earthquake, cushion cap, pile and pile soil stress situation found non-socketed piles when the soil interlayer thickness within a certain range, the composite pile small subside under dynamic, static loads, the non-socketed piles can better take advantage of the pile soil has a good seismic performance in the earthquake.

The Specific Characteristics of Shock and Blast Impacts on Construction Sites

2021 ◽  
pp. 81-88
Author(s):  
A.A. Komarov ◽  
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Dynamic Loads ◽  
Potential Hazard ◽  
Construction Sites ◽  
Static Loads ◽  
Equivalent Static Loads ◽  
Plane Crash ◽  
Nuclear Plants ◽  
The Impact

The practices of hazardous and unique facilities’ construction imply that specific attention is paid to the issues of safety. Threats associated with crash impacts caused by moving cars or planes are considered. To ensure safety of these construction sites it is required to know the potential dynamic loads and their destructive capacity. This article considers the methodology of reducing dynamic loads associated with impacts caused by moving collapsing solids and blast loads to equivalent static loads. It is demonstrated that practically used methods of reduction of dynamic loads to static loads are based in schematization only of the positive phase of a dynamic load in a triangle forms are not always correct and true. The historical roots of this approach which is not correct nowadays are shown; such approach considered a detonation explosion as a source of dynamic load, including TNT and even a nuclear weapon. Application of the existing practices of reduction of dynamic load to static load for accidental explosions in the atmosphere that occur in deflagration mode with a significant vacuumization phase may cause crucial distortion of predicted loads for the construction sites. This circumstance may become a matter of specific importance at calculations of potential hazard of impacts and explosions in unique units — for instance, in the nuclear plants. The article considers a situation with a plane crash, the building structure load parameters generated at the impact caused by a plane impact and the following deflagration explosion of fuel vapors are determined.

The Improvement of the Micro Torsional Mirror by a Reinforced Folded Frame

2000 ◽  
Author(s):  
Hung-Yi Lin ◽  
Weileun Fang
Keyword(s):  
Thin Film ◽  
Residual Stresses ◽  
Film Thickness ◽  
Experimental Results ◽  
Dynamic Loads ◽  
Inertia Force ◽  
Optical Performance ◽  
Thin Film Thickness ◽  
Static Loads ◽  
Dynamic Inertia

Abstract Stiffness of micromachined structures is limited by thin film thickness. Hence, static loads such as thin film residual stresses, or dynamic loads such as the inertia force could significantly deform the thinness micromachined torsional mirror. This work aims to stiffen the thin film micromachinined torsional mirror. The proposed torsional mirror exploits a reinforced frame to improve the stiffness of the mirror plate. Consequently, the mirror plate has less deformation no matter subject to the residual stresses or to the dynamic inertia force. In addition the reinforced frame stiffen the mirror without increasing the mass significantly. In application of this technique, the micro torsional mirror was fabricated through the integration of DRIE, conventional bulk and surface micromachining processes. The experimental results demonstrated that the proposed design significantly improves the flatness of the mirror plate in both static and dynamic conditions. Consequently, the optical performance of the micro torsional mirror was improved.

Vertical Load Path Under Static and Dynamic Loads in Concrete Crosstie and Fastening Systems

2014 ◽  
Author(s):  
Kartik R. Manda ◽  
Marcus Dersch ◽  
Ryan Kernes ◽  
Riley J. Edwards ◽  
David A. Lange
Keyword(s):  
Vertical Direction ◽  
Dynamic Loads ◽  
Vertical Load ◽  
Load Path ◽  
Test Program ◽  
Static Loads ◽  
Extensive Field ◽  
Interface Characteristics ◽  
Static And Dynamic Loads ◽  
Insight Into

An improved understanding of the vertical load path is necessary for improving the design methodology for concrete crossties and fastening systems. This study focuses on how the stiffness, geometry, and interface characteristics of system components affect the flow of forces in the vertical direction. An extensive field test program was undertaken to measure various forces, strains, displacements and rail seat pressures. A Track Loading Vehicle (TLV) was used to apply well-calibrated static loads. The TLV at slow speeds and moving freight and passenger consists at higher speeds were used to apply dynamic loads. Part of the analysis includes comparison of the static loads and the observed dynamic loads as a result of the trains passing over the test section at different speeds. This comparison helps define a dynamic loading factor that is needed for guiding design of the system. This study also focuses on understanding how the stiffness of the components in the system affects the flow of forces in the vertical direction. The study identifies that the stiffness of the support (ballast) underneath the crossties is crucial in determining the flow of forces. The advances made by this study provide insight into the loading demands on each component in the system, and will lead to improvements in design.

TRENDS IN STRANDED TANKER SALVAGE1

1985 ◽  
Vol 1985 (1) ◽  
pp. 177-181 ◽  
Author(s):  
John S. Clay
Keyword(s):  
Real Time ◽  
High Stress ◽  
Dynamic Loads ◽  
Time Data ◽  
Static Loads ◽  
New Developments ◽  
Future Needs ◽  
Real Time Data ◽  
Portable Computers

ABSTRACT The electronics revolution has changed many fields. Salvors have been slow to keep up with technology. Historically, salvage masters have relied almost exclusively on their subjective feel to ensure the survival of stranded vessels. Even today the analysis of stranded vessels is based primarily on static calculations. However, dynamic loads add to static loads and may be larger in many situations. This paper outlines traditional salvage calculations, new developments, and future needs. Salvage is in a state of transition, yet its future is gaining definition. Salvage of stranded tankers will be just as challenging as ever. It will still require an experienced salvage master who understands the multitude of factors involved, but dynamics will be accounted for by powerful software running in portable microcomputers at the site of strandings. Some computer inputs will be real-time data from lightweight sensors. The portable computers will provide forecasts on probability of breakup based on projected sea states during periods of high stress (low tide). These new tools will make the salvage masters' decisions more timely, confident, and accurate.

Energy Release Characteristics of Impact-Initiated Energetic Materials

2005 ◽  
Vol 896 ◽  
Author(s):  
Richard Ames
Keyword(s):  
Energy Release ◽  
Energetic Materials ◽  
High Strain ◽  
Polymer Binder ◽  
Dynamic Loads ◽  
Metal Powders ◽  
Static Loads ◽  
Material Classification ◽  
Plastic Deformation Process

AbstractImpact-initiated energetic materials are a class of energetic materials that are formulated to release energy under highly dynamic loads. Under quasi-static or static loads, however, the materials are intended to be inert and carry a material classification of 4.1 flammable solid. In general, these materials are formed by introducing metal powders into a polymer binder but a number of binderless varieties exist (primarily pressed/sintered intermetallics and thermites). Most of the materials are sufficiently insensitive so as not to produce a self-sustaining reaction; as such, they require the mechanical work of a high-strain-rate plastic deformation process to provide the energy required to drive the reaction. Traditional initiation techniques such as exploding bridge wires or flame initiation are not sufficient to maintain a reaction in this class of materials. This paper presents a brief overview of the energy release characteristics of this class of materials, including a discussion of the material formulations, initiation phenomena, and a discussion of the manner in which the material properties affect the energy release characteristics.

Sign in / Sign up

Export Citation Format

Share Document