Experimental Investigation of Water-Rich Fully Weathered Granite on Water Bursting and Mud Bursting

Frontiers in Earth Science ◽

10.3389/feart.2021.658855 ◽

2021 ◽

Vol 9 ◽

Author(s):

Suping Zheng

Keyword(s):

Particle Concentration ◽

Power Index ◽

Water Pressure ◽

Confining Pressure ◽

Significant Feature ◽

Weathered Granite ◽

Water Bursting ◽

Factor Variable ◽

Particle Size Gradation ◽

Critical Reason

In order to investigate the mechanism of water-rich and fully weathered granite on the water bursting and mud bursting, the single-factor variable method is adopted in this study. The particle size gradation, initial porosity, water pressure, confining pressure, and anti-outburst thickness are chosen to determine each factor on the evolution of sand gushing, porosity, permeability, fine particle concentration, and water gushing velocity. Results indicate that a particle loss is the most critical reason for the water bursting and mud bursting of water-rich and fully weathered granite. The transition of water bursting from the linear to the nonlinear stage is the most significant feature. Soil particles with a larger Talbol power index are more likely to lead to water bursting. In addition, there is a critical water pressure to control the occurrence of water bursting and mud bursting. It is found that when the confining pressure reached the soil yield strength, the evolution of water bursting and mud bursting is independent of the increase in confining pressure. The increase in anti-outburst thickness can also effectively limit the risk of water bursting and mud bursting.

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Dynamic Experimental Study on Highly Weathered Granite

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.518.132 ◽

2014 ◽

Vol 518 ◽

pp. 132-137

Author(s):

Lei Niu ◽

Quan Jie Song ◽

Shuang Xu ◽

Xiao Ming Guo

Keyword(s):

Shear Modulus ◽

Shear Strain ◽

Pore Water ◽

Effective Stress ◽

Pore Water Pressure ◽

Water Pressure ◽

Damping Ratio ◽

Confining Pressure ◽

Response Analysis ◽

Weathered Granite

The shear modulus and damping ratio are two important index in equivalent nonlinear model which is widely used in seismic response analysis. GDS resonant-column is used to study the shear modulus and damping ratio of highly weathered granite by controlling the consolidation confining pressure and pore water pressure. Variation of resonant frequency, shear modulus and damping ratio can be observed when different effective stress which is changed with confining pressure and pore water pressure applied on the sample. Hadin-Drnevich fitting curves are given on the basis of experimental data, and damping mechanism of highly weathered granite is discussed by making use of frictional theory. We can conclude from the results that there is a positive correlation between resonance frequency and shear strain, while there is a negative correlation between samples damping ratio and shear strain. The effective stress impact both samples shear modulus and damping ratio. However, pore water pressure can only act on damping ratio.

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Expulsion of particles from a buoyant blob in a fluidized bed

Journal of Fluid Mechanics ◽

10.1017/s0022112094003617 ◽

1994 ◽

Vol 278 ◽

pp. 63-81 ◽

Cited By ~ 15

Author(s):

G. K. Batchelor ◽

J. M. Nitsche

Keyword(s):

Fluidized Bed ◽

Fluidized Beds ◽

Particle Concentration ◽

Small Concentration ◽

Numerical Calculations ◽

Significant Feature ◽

Average Particle ◽

Remarkable Property ◽

Gas Fluidized Beds ◽

Secondary Instabilities

It is a significant feature of most gas-fluidized beds that they contain rising ‘bubbles’ of almost clear gas. The purpose of this paper is to account plausibly for this remarkable property first by supposing that primary and secondary instabilities of the fluidized bed generate compact regions of above-average or below-average particle concentration, and second by invoking a mechanism for the expulsion of particles from a buoyant compact blob of smaller particle concentration. We postulate that the rising of such an incipient bubble generates a toroidal circulation of the gas in the bubble, roughly like that in a drop of liquid rising through a second liquid of larger density, and that particles in the blob carried round by the fluid move on trajectories which ultimately cross the bubble boundary. Numerical calculations of particle trajectories for practical values of the relevant parameters show that a large percentage of particles, of such small concentration that they move independently, are expelled from a bubble in the time taken by it to rise through a distance of several bubble diameters.Similar calculations for a liquid-fluidized bed show that the expulsion mechanism is much weaker, as a consequence of the larger density and viscosity of a liquid, which is consistent with the absence of observations of relatively empty bubbles in liquid-fluidized beds.It is found to be possible, with the help of the Richardson-Zaki correlation, to adjust the results of these calculations so as to allow approximately for the effect of interaction of particles in a bubble in either a gas- or a liquid-fluidized bed. The interaction of particles at volume fractions of 20 or 30 % lengthens the expulsion times, although without changing the qualitative conclusions.

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Effect of Variable Confining Pressure on Cyclic Triaxial Behavior of K0-consolidated Soft Marine Clay

Civil Engineering Journal ◽

10.28991/cej-0309130 ◽

2018 ◽

Vol 4 (4) ◽

pp. 755

Author(s):

Lei Sun

Keyword(s):

Pore Water ◽

Pore Water Pressure ◽

Axial Strain ◽

Water Pressure ◽

Confining Pressure ◽

Stress Path ◽

Cyclic Stress ◽

Marine Clay ◽

Stress Ratios ◽

Variable Confining Pressure

The effect of variable confining pressure (VCP) on the cyclic deformation and cyclic pore water pressure in K0-consolidated saturated soft marine clay were investigated with the help of the cyclic stress-controlled advanced dynamic triaxial test in undrained condition. The testing program encompassed three cyclic deviator stress ratios, CSR=0.189, 0.284 and 0.379 and three stress path inclinations ηampl=3,1 and 0.64. All tests with constant confining pressure (CCP) and variable confining pressure (VCP) have identical initial stress and average stress. The results were analyzed in terms of the accumulative normalized excess pore water pressure rqu recorded at the end of each stress cycle and permanent axial strain, as well as resilient modulus. Limited data suggest that these behavior are significantly affected by both of the VCP and CSR. For a given value of VCP, both of the pore water pressure rqu and permanent axial strains are consistently increase with the increasing values of CSR. However, for a given value of CSR, the extent of the influence of VCP and the trend is substantially depend on the CSR.

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Experimental Study on the Variation Law of Excess Pore Water Pressure at the Bottom of the Foundation Pit for Excavation

Advances in Materials Science and Engineering ◽

10.1155/2020/9478725 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Qizhi Hu ◽

Qiang Zou ◽

Zhigang Ding ◽

Zhaodong Xu

Keyword(s):

Pore Water ◽

Pore Water Pressure ◽

Water Pressure ◽

Soft Soil ◽

Confining Pressure ◽

Deep Foundation ◽

Foundation Pit ◽

Excess Pore Water Pressure ◽

Accurate Expression ◽

Excess Pore

The excavation unloading of deep foundation pits in soft soil areas often produces negative excess pore water pressure. The rebound deformation of soil on the excavation surface of the foundation pit can be predicted reliably through the accurate expression of relevant variation laws. In combination with the principle of effective stress and the general equation of unidirectional seepage consolidation, an equation for calculating the rebound deformation from the bottom in the process of foundation pit excavation unloading was obtained. Additionally, a triaxial unloading test was adopted to simulate the excavation unloading processes for actual foundation pit engineering. After studying the variation law of the excess pore water pressure generated by excavation unloading, it was found that the negative excess pore water pressure increased with increasing unloading rate, while the corresponding peak value decreased with increasing confining pressure. The equation for rebound calculation was verified through a comparison with relevant measured data from actual engineering. Therefore, it is considered that the equation can reliably describe the rebound deformation law of the base. This paper aims to guide the design and construction of deep foundation pits in soft soil areas.

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Experimental Study on Mechanical Behavior of a New Backfilling Material: Cement-Treated Marine Clay

Advances in Materials Science and Engineering ◽

10.1155/2019/1261694 ◽

2019 ◽

Vol 2019 ◽

pp. 1-8 ◽

Cited By ~ 4

Author(s):

Nan Zhou ◽

Shenyang Ouyang ◽

Qiangqiang Cheng ◽

Feng Ju

Keyword(s):

Coal Mine ◽

Water Pressure ◽

Confining Pressure ◽

Secant Modulus ◽

Marine Clay ◽

Stress Strain ◽

Strata Control ◽

Strain Behavior ◽

Versus Strain ◽

Overlying Strata

Backfilling mining method is an overlying strata control way, which is widely used in underground coal mine. This method is effective in preventing and controlling geological disasters such as surface subsidence, mine water inrush, rock burst, and other disasters. Cement-treated marine clay (CMC) is a typical porous media, which has abundant reserves and can be used as a new backfilling material. Therefore, the mechanical characteristics of CMC are very important for overlying strata control in coal mine. To investigate stress-strain behavior of CMC, isotropic consolidated drained (CID) triaxial test and isotropic compression test (ICT) were conducted with different confining pressures in the range of 50–800 kPa. Stress-strain behavior was found similar to those of the overconsolidated stress-strain behavior as well as the pore water pressure versus strain. Stress versus strain curves under lower confining pressure 50–250 kPa presented shear dilatancy. The result shows that the peak strength increased linearly with increasing confining pressure. The internal friction angle and cohesion are 48° and 590 kPa, respectively. Before the confining pressure reaches 727 kPa, which is the primary yielding point, the secant modulus E1 (the secant modulus at 1% axial strain) and the secant modulus E50 (corresponding to the 50% of the peak point) increase initially and decrease afterwards with the increasing of confining pressure. Afterwards, the two parameters increased with increasing confining pressure. The yielding stress occurred in the stage, generating a dramatic decrease in tangent modulus. This study can be a theoretical basis for engineering application of this new backfilling material.

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Study on Damage Model and Damage Evolution Characteristics of Backfill with Prefabricated Fracture under Seepage-Stress Coupling

Advances in Materials Science and Engineering ◽

10.1155/2020/3642356 ◽

2020 ◽

Vol 2020 ◽

pp. 1-11

Author(s):

Jifeng Hou ◽

Zhongping Guo ◽

Weizhen Liu ◽

Hengze Yang ◽

WenWu Xie

Keyword(s):

Mechanical Properties ◽

Damage Evolution ◽

Coupling Effect ◽

Water Pressure ◽

Damage Model ◽

Confining Pressure ◽

Seepage Water ◽

Confining Pressures ◽

Initial Fracture ◽

Total Damage

Aiming at the backfill with prefabricated fracture under seepage-stress coupling, the concepts of fracture macrodamage, loaded mesodamage, seepage mesodamage, and total damage of backfill were proposed. Based on the macroscopic statistical damage model, the coupling effect of seepage, stress, and initial fracture was considered comprehensively and the damage model of backfill with prefabricated fracture under seepage-stress coupling was established. The mechanical properties of backfill with prefabricated fracture under different seepage water pressures and confining pressures were tested and the rationality of the model was verified. The research shows that the mechanical properties of backfill with prefabricated fracture under the seepage-stress coupling are determined by the seepage water pressure, the load, the initial fracture, and the coupling effect. Fracture and seepage have significant effects on the damage of the backfill. When the seepage water pressure is low, the fracture damage dominates; however, when the seepage water pressure is high, the seepage damage dominates; the total damage under the coupling action is more serious than the single factor. The development laws of the total damage evolution curves under different seepage water pressures and confining pressures are basically the same, and they show the S-shaped distribution law with the increase of the axial strain. With the increase of confining pressure, the damage effect of fracture and seepage on the backfill is weakened, indicating that the confining pressure has a certain inhibitory effect on the damage evolution of the backfill. The research results can provide a theoretical basis for the study of the stability of backfill with geological defects such as joints and fractures in deep high-stress and high-seepage water pressure coal mines.

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Hydraulics of subglacial outburst floods: new insights from the Spring–Hutter formulation

Journal of Glaciology ◽

10.3189/172756503781830728 ◽

2003 ◽

Vol 49 (165) ◽

pp. 299-313 ◽

Cited By ~ 94

Author(s):

Garry K. C. Clarke

Keyword(s):

Water Temperature ◽

Water Pressure ◽

Potential Gradient ◽

Confining Pressure ◽

Hydraulic Roughness ◽

Outburst Floods ◽

Natural Streams ◽

Flood Magnitude ◽

Manning Roughness ◽

Fluid Potential

AbstractUsing a slightly modified form of the Spring–Hutter equations, glacial outburst floods are simulated from three classic sites, “Hazard Lake”, Yukon, Canada, Summit Lake, British Columbia, Canada, and Grímsvötn, Iceland, in order to calibrate the hydraulic roughness associated with subglacial conduits. Previous work has suggested that the Manning roughness of the conduits is remarkably high, but the new calibration yields substantially lower values that are representative of those for natural streams and rivers. The discrepancy can be traced to a poor assumption about the effectiveness of heat transfer at the conduit walls. The simulations reveal behaviour that cannot be inferred from simplified theories: (1) During flood onset, water pressure over much of the conduit can exceed the confining pressure of surrounding ice. (2) Local values of fluid potential gradient can differ substantially from the value averaged over the length of the conduit, contradicting an assumption of simple theories. (3) As the flood progresses, the location of flow constrictions that effectively control the flood magnitude can jump rapidly over large distances. (4) Predicted water temperature at the conduit outlet exceeds that suggested by measurements of exit water temperature.

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Investigation on the Fracturing Permeability Characteristics of Cracked Specimens and the Formation Mechanism of Inrush Channel from Floor

Shock and Vibration ◽

10.1155/2021/8858733 ◽

2021 ◽

Vol 2021 ◽

pp. 1-12

Author(s):

Jianning Wang ◽

Weitao Liu ◽

Jianjun Shen

Keyword(s):

Crack Initiation ◽

Crack Propagation ◽

Formation Mechanism ◽

Water Pressure ◽

Water Inrush ◽

Confining Pressure ◽

Crack Initiation And Propagation ◽

Initiation And Propagation ◽

Final Failure ◽

Cracked Specimens

To study the fracture characteristics and the permeability change law of the cracked specimens during the complete stress-strain process, a mechanical model was constructed, from which different types of crack initiation angles were obtained. The crack inclination angles under uniaxial compression, confining compression, and confining tension, and the influence of confining pressure and pore water pressure on the crack propagation and permeability of rock mass were investigated and simulated with RFPA-Flow software using prefabricated crack models with crack initiation angles of 30°, 45°, and 60°. Furthermore, the formation mechanism of inrush channel from floor was qualitatively analyzed. The results indicated that the theoretical initiation angles of wing cracks, secondary coplanar cracks, and secondary inclined antiwing cracks were found to be 70.53°, 0°, and 123.8°, which were consistent with the simulation results. The crack propagation was mainly concentrated at the postpeak stage of the complete stress-strain curve, causing the peak of seepage velocity to lag behind the stress peak. For the case with a constant confining pressure, the rate of crack initiation and propagation to final failure was positively correlated with the internal pore pressure. For the case with a constant water pressure, the speed of crack initiation and propagation to final failure decreased first and then increased as the confining pressure increased. In addition, the longitudinal propagation of wing cracks and the increase in permeability were prone to occur in the low confining pressure zone, which induced the formation of water inrush channels. The research result provides an improved understanding for predicting and preventing water inrush disasters.

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The Undrained Characteristics of Tengger Desert Sand from True Triaxial Testing

Advances in Civil Engineering ◽

10.1155/2021/6320397 ◽

2021 ◽

Vol 2021 ◽

pp. 1-10

Author(s):

Xuefeng Li ◽

Weinan Lu ◽

Zhigang Ma ◽

Ni Tuo

Keyword(s):

Critical State ◽

State Transition ◽

Water Pressure ◽

Confining Pressure ◽

The State ◽

Transition Line ◽

Aeolian Sand ◽

True Triaxial ◽

Dense Sand ◽

High Confining Pressure

Aimed at the characteristics of aeolian sand under rapid construction conditions in desert geotechnical engineering, a series of the true triaxial undrained test were carried out on the GDS apparatus. The 3D deformation, failure, and other characteristics of the dense sand are obtained. Under the condition of same p c , the state transition point where the void water pressure changes from increasing to decreasing appears earlier and leads to enhanced dilatancy with the increase of b, which means the enhanced dilatancy of dense sand caused the increase in strength. The results of the same b shows that the void water pressure generally indicates a decrease at low confining pressure and an increase at high confining pressure, indicating that the aeolian sand shows dilatancy at low confining pressure and contraction at high confining pressure. The state transition point increases with the increase of p c , but all points tend to the same critical state line and state transition line. When b = 0, the critical state line is q = 1.57 p ′ , and the state transition line is q = 1.23 p ′ . When b = 1, the critical state line is q = 1.24 p ′ , and the state transition line is q = 1.04 p ′ . The results at same b obtained the unified critical state line and the state transition line. Therefore, the true triaxial test can obtain the unified relationship of void ratio, p c and b, which overcomes the fact that the existing test cannot consider the influence of b. The test results provide a basis data for the design, construction, and maintenance of geotechnical engineering in Tengger Desert.

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