scholarly journals Experimental Study of Slurry Flow in Mining-Induced Fractures during Longwall Overburden Grout Injection

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Dayang Xuan ◽  
Jian Li ◽  
Kaidan Zheng ◽  
Jialin Xu
Keyword(s):  
Longwall Mining ◽  
Injection Pressure ◽  
Theoretical Concept ◽  
Experimental Simulation ◽  
Slurry Flow ◽  
Grout Injection ◽  
Design And Optimization ◽  
Strike Direction ◽  
Degree Of Consolidation ◽  
Induced Fractures

Slurry flow in mining-induced overburden fractures is an important theoretical concept for the grouting design of longwall overburden grout injection engineering. In this study, a visual experimental simulation system of longwall overburden grouting was designed to study the flow, pressure distribution, consolidation, and fill thickness of fly ash slurry in overburden bedding separation. Experiments showed that the slurry generates a radial and bidirectional flow during nonpressure grouting and presents itself as an approximately elliptical dominant flow channel under pressure injection. This channel expanded horizontally along the strike direction and gradually became tabular. The slurry pressure increased as the grouting time increased. Although the pressure curves at different locations exhibited similar trends, their values did not decrease as the distance from the borehole center decreased during observations. Bleeding and consolidation occurred in the slurry as soon as it flowed out of the borehole to the fracture, and the degree of consolidation increased as a function of the distance from the injection borehole. The bleeding water gathered continually to the boundary of the bedding separation fracture and was then seeped to and stored by the underlying strata based on the injection pressure. The final injection fill is manifested as a half pace with a large thickness at the center. This research provides a theoretical basis for the design and optimization of overburden grout injection in underground longwall mining.

scholarly journals 3D FEM Model on the Parameters’ Influence of EPB-TBM on Settlements of Single and Twin Metro Tunnels During Construction

2021 ◽  
Author(s):  
Masoud Forsat ◽  
Mohammad Taghipoor ◽  
Masoud Palassi
Keyword(s):  
Three Dimensional ◽  
Injection Pressure ◽  
Effective Parameters ◽  
Grout Injection ◽  
3D Fem ◽  
Supporting Pressure ◽  
Epb Tbm ◽  
The Face ◽  
Clear Distance ◽  
Twin Tunnels

AbstractThe present research exposes the investigation on three-dimensional modeling of the single and twin metro tunnels for the case of the Tehran metro line. At first, simulation implemented on the comparison of the ground movements in the single and twin tunnels. Then the simulation has been performed on the influence of effective parameters of EPB-TBM on the surface settlements throughout excavation. The overcutting, shield conicity, grouting, and the final lining system modeled and the influence of face supporting pressure, grout injection pressure, as well as the clear distance of the tunnels, has been analyzed. The initial results showed a valid ground settlement behavior. The maximum settlements occurred at the end of the shield tail and it was higher in the single tunnel. The face supporting pressure had more effect on the surface settlement in comparison to the grout injection pressure. By increasing the face pressure in the single tunnel, the place of maximum settlement moved back while the grout pressure is insignificant for decreasing the settlements. Furthermore, the influence of the clear distance in the twin tunnels led to zero after the length of 30 m. Accordingly, for more distances, the tunnels must be examined independently and as two different single tunnels.

scholarly journals Field Investigation on Limestone Treatment using Fissure Grouting Method

2018 ◽  
Vol 7 (4.35) ◽  
pp. 338
Author(s):  
Prakash Ananthan ◽  
Leong Sing Wong
Keyword(s):  
Hydrostatic Pressure ◽  
Injection Pressure ◽  
Field Investigation ◽  
Grout Injection ◽  
Exposed Rock ◽  
Grouting Pressure ◽  
High Injection Pressure ◽  
Ultimate Outcome ◽  
Line Loss ◽  
Limestone Rock

This paper documents a field study on fissure grouting for limestone with a specific aim to investigate grout injection into the rock in order to reduce its permeability. The study focused on grouting in advance of excavation and it is applicable to grouting carried out to seal exposed rock surfaces. Investigation concentrated on the need to carry out fissure grouting to seal off excessive water entering the excavation through fractured rocks. In this case, the grout mixtures involved a combination of Ordinary Portland cement (OPC) and bentonite with appropriate amount of water. The grouting was performed at each stage until the grout flow rate and pressure reached a constant level for the last five minutes. If the stage of grouting in a borehole required more grout, this implies that there exist more fissure and cracks in the rock. The ultimate outcome of the rock fissure grouting was to obtain a good feed into limestone rock fissures, and thus, the process involved high injection pressure. The minimum grouting pressure was indicated as the hydrostatic pressure plus line loss pressure. To ensure that the outcome was achieved, it was recommended for an additional two bar pressure to be maintained as hydrostatic pressure. 

scholarly journals Stable Balance Adjustment Structure of the Quadruped Robot Based on the Bionic Lateral Swing Posture

2020 ◽  
Vol 2020 ◽  
pp. 1-10
Author(s):  
Jian-Hua Qin ◽  
Jie Luo ◽  
Kai-Chi Chuang ◽  
Tian-Syung Lan ◽  
Lie-Ping Zhang ◽  
...  
Keyword(s):  
Static Stability ◽  
Quadruped Robot ◽  
Experimental Simulation ◽  
Upright Posture ◽  
Design And Optimization ◽  
Generalized Coordinates ◽  
The Stability ◽  
Leg Kinematics ◽  
Peak Value ◽  
Robot Body

Aiming at the problem that the stability of the quadruped robot is decreased as its leg momentum is too high, a stable balance adjustment structure of the quadruped robot based on the bionic lateral swing posture is proposed. First, the leg structure of the quadruped robot is improved and designed by using the mechanism of the lateral swing posture of the leg of the hoof animal. Then, the D-H method is used to construct the corresponding leg kinematics model and determine the generalized coordinates of the leg joints in the lateral swing posture. The torque expression of the quadruped robot when it is tilted is established. Based on the differential equation of momentum of the hip joint and its static stability analysis, the static stability conditions in the upright posture and the bionic lateral swing posture are given. Finally, the experimental simulation and comparative analysis of the upright posture and the lateral swing posture of the quadruped robot are proposed by using the Adams virtual prototype technology. The simulation results show that as the angle of lateral swing increases, the peak value of the positive flip torque of the quadruped robot body increases accordingly, while the degree of tilt decreases accordingly, which shows that the bionic lateral swing posture of the quadruped robot has higher static stability than the traditional upright posture. This research provides a technical reference for the design and optimization of the offline continuous gait of the robot and the improvement of stability.

Design and Optimization of the Exhausting-Flowing Remover in Fully-Mechanized Top-Coal Caving Mining Face

2011 ◽  
Vol 347-353 ◽  
pp. 2666-2671 ◽  
Author(s):  
Guo Dong Zhai ◽  
Zhi Feng Dong ◽  
Sheng Ming Yan
Keyword(s):  
Longwall Mining ◽  
Coal Dust ◽  
Dust Control ◽  
Testing System ◽  
Technological Problem ◽  
Dust Extraction ◽  
Design And Optimization ◽  
Removal Technology ◽  
Mining Face ◽  
High Output

Because of its high output，much more dust is produced in fully-mechanized Longwall mining with top-coal caving (LMTC) mining faces than in conventional mechanized mining faces without top-coal caving. Now dust control in fully-mechanized LMTC mining faces has become a key technological problem needed to be solved. Baced on the ejected dust removal technology, this paper developed a coal dust extraction which used in the fully mechanized LMTC mining face. For the optimization of the extraction’s property, measure systems are designed. By amounts of assembled experiment, the best structure of the extraction is found. In this paper, the research of the spray characteristic on the water nozzle was carried out by using the jet parameter testing system. Some important result can be gotten such as the velocity of spray particle, the distribution of the velocity, the diameter of spray particle, the spread of the spray particle etc. The study was helpful to optimizing the exhausting-flowing remover and improving the dust remover’s efficiency. From the industry examination, the coal dust extraction’s performance has greatly improved.

scholarly journals A General Review on Longwall Mining-Induced Fractures in Near-Face Regions

Geofluids ◽  
2019 ◽  
Vol 2019 ◽  
pp. 1-22 ◽  
Author(s):  
Qingsheng Bai ◽  
Shihao Tu
Keyword(s):  
Rock Mass ◽  
Longwall Mining ◽  
Safety Evaluation ◽  
Global Perspective ◽  
Small Scale ◽  
Underground Structures ◽  
Successful Operation ◽  
Advantages And Disadvantages ◽  
Induced Fractures ◽  
Feasible Solutions

It is believed that underground longwall mining usually produces fractures in the surrounding rocks. On the one hand, mining-induced fractures not only degrade the strength of the rock mass but also serve as main channels for fluids (e.g., water and methane). Fractures facilitate the failure of the rock mass and fluid inrush into working spaces. Therefore, mining-induced fractures are significant for the safety evaluation of underground structures and finding feasible solutions. On the other hand, the fractures are also beneficial for methane collection and coal fragmentation, which are essential for the successful operation of longwall top coal caving mining. Therefore, determining the characteristics of induced fractures is significant for underground longwall mining. From a global perspective, longwall mining-induced fractures in the overburden have been well studied, which improves the understanding of the mining pressure and ground control. However, induced fractures near the longwall face, which have more significant effects on mining activities, have not been summarized. The goal of this review paper is to provide a general summary of the current achievements in characterizing mining-induced fractures in near-face regions. The characteristics of mining-induced fractures in the coal wall, chain pillar, immediate roofs and top coal, and floors are reviewed and summarized. Remarks are made on the current progress of, fundamental problems with, and developments in methodologies for characterizing mining-induced fractures using methods such as field observations, small-scale laboratory tests, physical modeling, and numerical modeling. Based on a comprehensive analysis, the advantages and disadvantages of each method are discussed, and the ideal conditions for applying each of these methods are also recommended.

HREM observation of dislocations near room temperature fractures in silicon

1988 ◽  
Vol 46 ◽  
pp. 892-893
Author(s):  
M. H. Rhee ◽  
W. A. Coghlan
Keyword(s):  
Cross Section ◽  
Room Temperature ◽  
Single Crystal Silicon ◽  
Dislocation Nucleation ◽  
Back Side ◽  
Ion Milling ◽  
Crystal Silicon ◽  
Flat Surfaces ◽  
Induced Fractures ◽  
Vicker’S Microhardness

Silicon is believed to be an almost perfectly brittle material with cleavage occurring on {111} planes. In such a material at room temperature cleavage is expected to occur prior to any dislocation nucleation. This behavior suggests that cleavage fracture may be used to produce usable flat surfaces. Attempts to show this have failed. Such fractures produced in semiconductor silicon tend to occur on planes of variable orientation resulting in surfaces with a poor surface finish. In order to learn more about the mechanisms involved in fracture of silicon we began a HREM study of hardness indent induced fractures in thin samples of oxidized silicon.Samples of single crystal silicon were oxidized in air for 100 hours at 1000°C. Two pieces of this material were glued together and 500 μm thick cross-section samples were cut from the combined piece. The cross-section samples were indented using a Vicker's microhardness tester to produce cracks. The cracks in the samples were preserved by thinning from the back side using a combination of mechanical grinding and ion milling.

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