scholarly journals Liquid CO2 Phase-Transition Rock Fracturing: A Novel Technology for Safe Rock Excavation

2021 ◽  
Vol 12 (1) ◽  
pp. 68
Author(s):  
Haoyue Sui ◽  
Tianming Su ◽  
Ruilin Hu ◽  
Ke Yang ◽  
Yaxing Cheng
Keyword(s):  
Phase Transition ◽  
Rock Mass ◽  
Processing System ◽  
Field Tests ◽  
Fractal Dimensions ◽  
Dominant Frequency ◽  
Rock Breaking ◽  
Rock Breakage ◽  
Rock Fracturing ◽  
Liquid Co2

In order to determine the applicability of liquid CO2 phase-transition fracturing technology in rock mass excavations, the principles of CO2 phase-transition fracturing were analyzed, and field tests of liquid CO2 phase-transition fracturing were performed. An “Unmanned Aerial Vehicle (UAV) camera shooting + Microstructure Image Processing System (MIPS) analyzing” method was used to acquire the rock mass characteristics. Further, the Hilbert–Huang Transform (HHT) energy analysis principle was adopted to analyze the characteristics of fracturing vibration waves. The experimental results showed that during the process of fracturing, there were both dynamic actions of rock breakage due to excitation stress wave impacts, and quasi-static actions of rock breakage caused by gasification expansion wedges. In semi-infinite spaces, rock-breakage zones can mainly be divided into crushing zones, fracture zones, and vibration zones. At the same time, under ideal fracturing effects and large volumes, the fracturing granularity will be in accordance with the fractal laws. For example, the larger the fractal dimensions, the higher the proportion of small fragments, and vice versa. Moreover, the vibration waves of the liquid CO2 phase-transition fracturing have short durations, fast attenuation, and fewer high-frequency components. The dominant frequency band of energy will range between 0 and 20 Hz. The liquid CO2 phase-transition fracturing technology has been observed to overcome the shortcomings of traditional explosive blasting methods and can be applied to a variety of rock types. It is a safe and efficient method for rock-breaking excavations; therefore, the above technology effectively provides a new method for the follow-up of similar engineering practices.

Numerical Simulation of Rock Fragmentation Process for TBM Cutters Based on Three-Dimensional Dynamic Fracturing Method

2012 ◽  
Vol 472-475 ◽  
pp. 2033-2036
Author(s):  
Gang Li ◽  
Li Da Zhu ◽  
Jian Yu Yang ◽  
Wan Shan Wang
Keyword(s):  
Rock Mass ◽  
Three Dimensional ◽  
Element Model ◽  
Rock Breaking ◽  
Disc Cutter ◽  
Material Strength ◽  
Rock Breakage ◽  
Joint Spacing ◽  
Geological Conditions ◽  
Cutter Spacing

The rock breakage process is the interaction process between TBM and rock mass, which is affected by TBM specifications, such as thrust force, cutter tip width and profile, cutter spacing, RPM, and torque, and rock mass properties mainly including rock material strength, rock brittleness, joint spacing and orientation. In this study, based on the systematic study of the existed rock constitutive model achievements and introduction of rock breaking mechanism, main failure mode of rock in the breaking process of disc cutter is added and revised in order to meet the actual situation. The method of establishing finite element model of disc cutter breaking process using ANSYS AUTODYN-3D software is introduced. After the dynamic simulation, we can obtain that geotechnical interface disturbance insulted by disc cutter. Based on plenty of experiments, it confirms reliability of numerical methods and provides a method to study cutting performance for different geological conditions.

scholarly journals Analysis of fracture mechanism for surrounding rock hole based on water-filled blasting

2020 ◽  
Vol 7 (4) ◽  
pp. 704-713
Author(s):  
Jun Wang ◽  
Jingxuan Yang ◽  
Fengfeng Wu ◽  
Tengfei Hu ◽  
Shams Al Faisal
Keyword(s):  
Field Testing ◽  
Rock Breaking ◽  
Stress Waves ◽  
Surrounding Rock ◽  
Water Medium ◽  
Rock Breakage ◽  
Rock Fracturing ◽  
Fracture Dynamics ◽  
Fracture Development ◽  
Combined Action

AbstractThe principles of fracture development during underwater blasting are examined based on explosion and impact dynamics, fluid dynamics, fracture dynamics, and field testing. The research reveals that the fracturing of the surrounding rock during underwater blasting is due to the combined action of shock and stress waves for the initial rock breakage and subsequent water expansion. The fracture development model for the surrounding rock of a drilling hole during underwater blasting is established. The rock fracturing range under the combined action of shock and stress waves is developed, as well as the fracture propagation rules after the wedging of the water medium into the fractures. Finally, the results of deep-hole underwater blasting tests on large rocks confirm the efficient utilization of explosive in the hole to improve the safety conditions. Accordingly, safe and static rock breaking under the detonation of high-effect explosive can be achieved. In addition, super-dynamic loading from the explosions and static loading from the water medium in the hole can be adequately combined for rock breaking.

General concept of determining the parameters of non-mining walls of ultra-deep diamond deposits development open pits

2021 ◽  
pp. 48-53
Author(s):  
I. V. Zyryanov ◽  
A. N. Akishev ◽  
I. B. Bokiy ◽  
N. M. Sherstyuk
Keyword(s):  
Rock Mass ◽  
Structural Relaxation ◽  
Slope Angle ◽  
Field Tests ◽  
Friction Angle ◽  
Strength Properties ◽  
Strength Characteristics ◽  
Open Pit ◽  
Open Pit Mining ◽  
Relaxation Coefficient

A specific feature of open pit mining of diamond deposits in Western Yakutia is the construction of the open pits in the zone of negative ambient temperatures, which includes thick permafrost rock mass, and which is at the same time complicated by the influence of cryogenic processes on deformation of pit wall benches. The paper presents the comparative analysis of strength characteristics in frozen and thawed rocks, stability of benches during mining, the general geomechanical approach to the determination of parameters of non-mining walls of the ultra-deep open pit diamond mines, and the parameters of nonmining walls and benches. Optimization of open pit wall configuration should primarily be based on the maximum utilization of the strength properties of frozen rocks in combination with the development of new approaches, calculation schemes and methods for assessing stability of open pit walls and benches of unconventional design, including the non-mining vertical benches. The main design characteristic that determines the parameters of open pit walls is the structural tectonic relaxation coefficient, which specifies the calculated value of cohesion in rock mass. For the diamond deposits, the values of the structural relaxation coefficient were obtained in a series of field tests and back calculations. Full-scale tests were carried out both during exploration operations in underground mines and in open pits. The accuracy of determining the values of the structural relaxation coefficient in the range of 0.085–0.11 is confirmed by the parameters of non-mining walls in an open pit mine 385–640 m deep, with overall slope angles of 38–55° and a steeper H 0.35–0.5 lower part having the slope angle of up to 70° with average strength characteristics of 7.85–11.84 MPa and the internal friction angle of 28.1–37.4°. Using the natural load-bearing capacity of rock mass to the full advantage, which the values of the structural relaxation coefficient of deposits show, allows optimization of open pit wall slope design and minimization of stripping operations.

scholarly journals Mathematical modelling of thermal stresses within the borehole walls in terms of plasma action

2021 ◽  
Vol 15 (2) ◽  
pp. 63-69
Author(s):  
Anatolii Bulat ◽  
Valentyn Osіnnii ◽  
Andrii Dreus ◽  
Nataliia Osіnnia
Keyword(s):  
Mathematical Model ◽  
Thermal Stresses ◽  
Plasma Jet ◽  
Rock Breaking ◽  
Heating Time ◽  
Borehole Wall ◽  
Heated Layer ◽  
Rock Layer ◽  
Rock Fracturing ◽  
Temperature Plasma

Purpose is the development of a mathematical model to study and describe thermal processes within the borehole wall in terms of plasma-based rock breaking. Methods. The following has been applied: theoretical analysis in the framework of a theory of brittle thermoelasticity breaking, methods of mathematical modeling, and computational experiment. Findings. Brief information on the results of the development of advanced plasma-based technology for borehole reaming for hard mineral mining has been represented. The results of industrial tests of plasma plant of 150-200 kW·s power with plasma-generating gas in the air for hard rock breaking have been represented. The plant and plasma-based technology of borehole reaming were tested in underground conditions of Kryvbas mines while reaming a perimeter hole to drive a ventilation rise in silicate-magnetite quartzites. A mathematical model has been proposed to analyze heat and mechanical fields in the rock during the plasma-based action on the borehole walls. Numerical studies of the temperature dynamics and thermal stresses within the borehole-surrounding rock layer have been carried out. It has been demonstrated that if low-temperature plasma is used (Т = 3500-4000°С), thermal compressing stresses are induced within the thin rock layer; the stresses may exceed the boundary admissible ones. It has been identified that plasma-based effect on the borehole wall makes it possible to create the conditions for intense rock fracturing and breaking. Originality. Solution of a new problem of thermoelastic state of a borehole wall in terms of plasma action has been obtained. The proposed mathematical model has been formulated in a cylindrical coordinate system and considers convective and radiation heat exchange between a plasma jet and a borehole wall. Practical implications. The obtained results make it possible to assess the rock state depending on the plasma jet parameters. The proposed methods of calculations will help carry out research to evaluate breaking parameters (the required heating time, thickness of the heated layer, and approximate spall dimensions) and develop different methods for the breaking process control.

scholarly journals Gas Jet Coal-Breaking Behavior: An Elliptical Crushing Theoretical Model

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-16
Author(s):  
Gongda Wang ◽  
Yuanyuan Wang ◽  
Xin Yang ◽  
Xin Song
Keyword(s):  
Theoretical Model ◽  
Coalbed Methane ◽  
Clean Energy ◽  
Rock Breaking ◽  
Gas Jet ◽  
Rock Fracturing ◽  
Efficient Technology ◽  
Methane Drainage ◽  
Experimental Values ◽  
The Impact

Coalbed methane (CBM) is a source of clean energy and has been recovered in past decades all over the world. Gas dynamic disaster is the primary disaster in outburst coal, and methane drainage plays a key role in eliminating this danger. As an efficient technology, a gas jet is widely used in CBM development and methane drainage. In this work, the full impinging process of coal and rock fracturing by a supersonic gas jet was studied. To understand how jet parameters affect coal and rock fracturing results, an elliptical crushing theoretical model was proposed. In addition, a laboratory experiment was designed to examine the proposed model, and four key parameters affecting the fracturing results were studied. The results show that different from the monotonic variation of theoretical values, there is a turning point in the variation of experimental values under some parameters. Considering the influence of the depth and radius of the erosion pit, the rock-breaking effect is better when the nozzle size is 2.75 Ma. The optimal target distance is 30 mm, and the impact pressure of a gas jet should be continuously increased in order to achieve certain rock-breaking effects under the impact of the jet.

20 Years Experience Burning Heavy Fuels in Heavy Duty Gas Turbines

1973 ◽  
Author(s):  
A. O. White
Keyword(s):  
Gas Turbines ◽  
Processing System ◽  
Operating Experience ◽  
Field Tests ◽  
Early Experience ◽  
Liquid Fuels ◽  
Heavy Duty ◽  
Fuel Processing ◽  
Wide Range ◽  
Heavy Fuels

This paper covers the early experience of the author’s company in burning residual oils in their gas turbines and the problems that occurred. The laboratory invesgations and field tests that resulted in a fuel processing system that permitted satisfactory operation on a wide range of liquid fuels are described. The operating experiences, where residual fuels were successfully burned in a large number of units, are described. The most recent operating experience with residual and crude oils and heavy distillates is also covered. A list of the various installations with dates and hours of operation is included and it is concluded that heavy duty gas turbines burning heavy fuels will be established as the up-to-date source of economical power in many applications.

Experimental investigation on the characteristics of the dynamic rail pad force and its stress distribution in the time and frequency domain

2019 ◽  
Vol 234 (2) ◽  
pp. 201-213 ◽  
Author(s):  
Xu Zhang ◽  
Chunfa Zhao ◽  
Xiaobo Ren ◽  
Yang Feng ◽  
Can Shi ◽  
...  
Keyword(s):  
Stress Distribution ◽  
Frequency Domain ◽  
Maximum Stress ◽  
Field Tests ◽  
Service Condition ◽  
Field Testing ◽  
Dominant Frequency ◽  
Test Results ◽  
Parabolic Shape ◽  
Dominant Frequencies

The rail pad force and its stress distribution have critical influences on the performance and fatigue life of the rail, fasteners, and sleepers. The characteristics of the rail pad force and its stress distribution in the time and frequency domain obtained from field tests carried out using matrix-based tactile surface sensor are presented in this paper. The field testing involved rail pads under various axle-loads of running trains at different speeds. The influences that the train axle-load, the operational speed, and the rail pad stiffness have on the rail pad force and its stress distribution are analyzed. The test results indicate that the rail pad stiffness has a remarkable influence on the amplitude of the rail pad force but has little influence on its dominant frequencies. The first dominant frequency of the rail pad force is quite close to the passing frequency of the vehicle length. The stress distribution on the rail pad has a parabolic shape along the longitudinal and the lateral directions with the large stress appearing near the center of the rail pad, and is remarkably affected by the service condition of the rail pad. The maximum stress is about 2.5 to 3 times of the average stress, which is significantly greater than the nominal stress resulting from the assumption of uniform stress distribution.

Experimental Study of Mechanism of Rock Breakage with High-Pressure Cavitating Water Jets

2011 ◽  
Vol 243-249 ◽  
pp. 2130-2137
Author(s):  
Zhao Long Ge ◽  
Yi Yu Lu ◽  
Ji Ren Tang ◽  
Ke Hu ◽  
Wen Feng Zhang
Keyword(s):  
High Pressure ◽  
Confining Pressure ◽  
Rock Breaking ◽  
Pressure Increase ◽  
Rock Breakage ◽  
Bubble Cloud ◽  
Cubic Curve ◽  
Water Jets ◽  
Erosion Efficiency ◽  
Pump Pressure

To explore the relationship among the erosion ability of high-pressure cavitating water jets, hydraulic parameters and rock nature with a series of experiments relating to the efficiency of rock-breaking with cavitating water jets for different porosity of rock under different confining pressures and pump pressures. The results show that the erosion efficiency (erosion mass and erosion depth) of cavitating water jets is fitted a conic curve with pump pressure and confining pressure. It increases with the pump pressure increases while decreases with the confining pressure increases; the length of the bubble cloud decreases with the confining pressure increase and the length increases with the pump pressure increase, which is accorded with cubic curve. The bubble cloud length influences the rock-breaking efficiency by deciding the valid stand-off distance directly. Under the experimental condition, the cavitation happens once the pump pressure reaches 7MPa, and the cavitating water jets can crushing the sandstones which the uniaxial compressive strength is 96MPa. On the other hand, the porosity of rock is another main factor of rock breakage with high pressure cavitating water jets. The higher the porosity of rock is, the easier the rock can be broken.

Elastic Wave Measurement Technology and its Engineering Application

2013 ◽  
Vol 655-657 ◽  
pp. 795-800
Author(s):  
Jin Kui Li ◽  
Lei Zhang ◽  
Wen Hua Yang ◽  
Ming Liang Sun
Keyword(s):  
Rock Mass ◽  
Elastic Wave ◽  
Wave Velocity ◽  
Engineering Application ◽  
Field Tests ◽  
Physical And Mechanical Properties ◽  
Field Work ◽  
Measurement Technology ◽  
Testing Technique ◽  
Underground Chamber

The velocity and amplitude of elastic wave in the rock mass are dependent on the physical and mechanical properties, as well as the structural and stress state of rock mass. The elastic wave testing technique has become one of the most important approaches in geological engineering and rock mechanics. In order to enhance the analysis and application of elastic wave testing technique, the present paper investigates the elastic wave propagation pattern both in laboratory and in field. The lab tests focus on wave velocity in rock mass and the field work focus on the measurement of longitudinal wave velocity by using double-service elastic wave test. The field tests also include the testing of the roadway surrounding rock loose circle on the edge of underground chamber construction site. The study profiles the rock mass’s elastic wave dynamic characteristics, clarifies the rock mass structures, assess the property of the rock mass surrounding the subway. All these are of great significance to the underground chamber and tunneling engineering design and construction.

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