scholarly journals Numerical Simulation of Nanosilica Sol Grouting for Deep Tunnels Based on the Multifield Coupling Mechanism

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Dongjiang Pan ◽  
Kairong Hong ◽  
Helin Fu ◽  
Zhiguo Li ◽  
Limeng Zhang ◽  
...  
Keyword(s):  
Physical Properties ◽  
Transition Region ◽  
Molecular Diffusion ◽  
Initial Permeability ◽  
Silica Sol ◽  
Water Diversion ◽  
Coupling Mechanism ◽  
Mechanical Dispersion ◽  
Grouting Pressure ◽  
Geological Conditions

Grouting is an effective technical way for the construction of deep tunnels in unfavorable geological conditions. The fluid-solid-chemical coupling mechanism of grouting process is analyzed from the following three aspects: influence of physical properties of silica sol on permeability coefficient, dynamic changes of porosity and permeability of geotechnical media with seepage pressure, and governing equations for flow and mass transfer characteristics. A dynamically changing model for nanosilica sol grouting in deep tunnels is established, considering the changing physical properties of grout and surrounding rock. Based on the Xianglushan Tunnel of Yunnan Water Diversion Project, the temporal and spatial evolution of silica sol grout is studied. The effect characteristics of grouting pressure and initial permeability are clarified. The rationality of this model is verified by classical Newtonian fluid grouting theory. The main conclusions: with the molar concentration as the index, the grout range can be divided into the raw grout region and the transition region; with the decrease of the grouting pressure, the growth rate of the normal grouting radius and the axial grouting radius will gradually decrease; due to the mechanical dispersion and molecular diffusion, the range of the transition region will gradually increase with time. The ratio of the transition region to grouting radius fluctuates slightly with time under the initial permeability of 5 D. The fluctuation increases with the decrease of initial permeability, and the average ratio increases with the decrease of grouting pressure. This study can provide theoretical guidance for grouting design of deep tunnel engineering.

NILOMAG 77

Alloy Digest ◽  
1995 ◽  
Vol 44 (10) ◽  
Keyword(s):  
Physical Properties ◽  
Tensile Properties ◽  
Heat Treating ◽  
Initial Permeability ◽  
Magnetic Alloy ◽  
Soft Magnetic ◽  
Soft Magnetic Alloy ◽  
High Level

Abstract NILOMAG ALLOY 77 is a 77 Ni soft magnetic alloy with a high level of initial permeability. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on heat treating. Filing Code: Ni-488. Producer or source: Inco Alloys International Inc.

scholarly journals A Comprehensive Coal Reservoir Classification Method Base on Permeability Dynamic Change and Its Application

Energies ◽  
2020 ◽  
Vol 13 (3) ◽  
pp. 644 ◽  
Author(s):  
Xinlu Yan ◽  
Songhang Zhang ◽  
Shuheng Tang ◽  
Zhongcheng Li ◽  
Yongxiang Yi ◽  
...  
Keyword(s):  
Coalbed Methane ◽  
Dynamic Change ◽  
Initial Permeability ◽  
Gas Production ◽  
Gas Desorption ◽  
Reservoir Permeability ◽  
Geological Conditions ◽  
Production Stages ◽  
Productivity Potential ◽  
Coal Reservoir

Due to the unique adsorption and desorption characteristics of coal, coal reservoir permeability changes dynamically during coalbed methane (CBM) development. Coal reservoirs can be classified using a permeability dynamic characterization in different production stages. In the single-phase water flow stage, four demarcating pressures are defined based on the damage from the effective stress on reservoir permeability. Coal reservoirs are classified into vulnerable, alleviative, and invulnerable reservoirs. In the gas desorption stage, two demarcating pressures are used to quantitatively characterize the recovery properties of permeability based on the recovery effect of the matrix shrinkage on permeability, namely the rebound pressure (the pressure corresponding to the lowest permeability) and recovery pressure (the pressure when permeability returns to initial permeability). Coal reservoirs are further classified into recoverable and unrecoverable reservoirs. The physical properties and influencing factors of these demarcating pressures are analyzed. Twenty-six wells from the Shizhuangnan Block in the southern Qinshui Basin of China were examined as a case study, showing that there is a significant correspondence between coal reservoir types and CBM well gas production. This study is helpful for identifying geological conditions of coal reservoirs as well as the productivity potential of CBM wells.

scholarly journals 1-D Air-snowpack modeling of atmospheric nitrous acid at South Pole during ANTCI 2003

2008 ◽  
Vol 8 (23) ◽  
pp. 7087-7099 ◽  
Author(s):  
W. Liao ◽  
D. Tan
Keyword(s):  
Liquid Layer ◽  
Molecular Diffusion ◽  
Volume Ratio ◽  
Critical Factor ◽  
Snow Surface ◽  
High Concentration ◽  
Nitrite Concentration ◽  
Mechanical Dispersion ◽  
Quasi Liquid Layer ◽  
D Model

Abstract. A 1-D air-snowpack model of HONO has been developed and constrained by observed chemistry and meteorology data. The 1-D model includes molecular diffusion and mechanical dispersion, windpumping in snow, gas phase to quasi-liquid layer phase HONO transfer and quasi-liquid layer nitrate and interstitial air HONO photolysis. Photolysis of nitrate is important as a dominant HONO source inside the snowpack, however, the observed HONO emission from the snowpack was triggered mainly by the equilibrium between quasi liquid layer nitrite and firn air HONO deep down the snow surface (i.e. 30 cm below snow surface). The high concentration of HONO in the firn air is subsequently transported above the snowpack by diffusion and windpumping. The model uncertainties come mainly from lack of measurements and the interpretation of the QLL properties based on the bulk snow measurements. One critical factor is the ionic strength of QLL nitrite, which is estimated here by the bulk snow pH, nitrite concentration, and QLL to bulk snow volume ratio.

scholarly journals 1-D air-snowpack modeling of atmospheric nitrous acid at South Pole during ANTCI 2003

2008 ◽  
Vol 8 (3) ◽  
pp. 9731-9759
Author(s):  
◽  
D. Tan
Keyword(s):  
Liquid Layer ◽  
Molecular Diffusion ◽  
Volume Ratio ◽  
Critical Factor ◽  
Snow Surface ◽  
High Concentration ◽  
Nitrite Concentration ◽  
Mechanical Dispersion ◽  
Quasi Liquid Layer ◽  
D Model

Abstract. A 1-D air-snowpack model of HONO has been developed and constrained by observed chemistry and meteorology data. The 1-D model includes molecular diffusion and mechanical dispersion, windpumping in snow, gas phase to quasi-liquid layer phase HONO transfer and quasi-liquid layer nitrate and interstitial air HONO photolysis. Photolysis of nitrate is important as a dominant HONO source inside the snowpack, however, the observed HONO emission from the snowpack was triggered mainly by the equilibrium between quasi liquid layer nitrite and firn air HONO deep down the snow surface (i.e. 30 cm below snow surface). The high concentration of HONO in the firn air is subsequently transported above the snowpack by diffusion and windpumping. The model uncertainties come mainly from lack of measurements and the interpretation of the QLL properties based on the bulk snow measurements. One critical factor is the ionic strength of QLL nitrite, which is estimated here by the bulk snow pH, nitrite concentration, and QLL to bulk snow volume ratio.

Analysis of Crack Initiation and Treatment in the South-to-North Water Diversion Suining Two Station Project

2013 ◽  
Vol 368-370 ◽  
pp. 1123-1127
Author(s):  
Ze Jun Liu ◽  
Jun Hao Wang ◽  
Qing Shan Zheng ◽  
Yue Xin She ◽  
Yi Jiang
Keyword(s):  
Crack Initiation ◽  
Large Scale ◽  
Water Diversion ◽  
Regulatory Requirements ◽  
Substantial Impact ◽  
Geological Conditions ◽  
Project Construction ◽  
Long Time ◽  
North Water ◽  
Better Than

For projects, especially large-scale projects, due to the long time of project construction, the construction of the complexity of the geological conditions, sometimes inevitably lead to quality defects.How scientific and reasonable quality defects hidden works to take remedial measures, or effective correction to restore the loss of time, cost, quality, safety,become an important engineering problem.Some cracks, will not have a substantial impact on the project, you can take measures to deal with to ensure proper implementation of the project.The article takes the analysis of crack initiation and Treatment in the Suining two station project.There are a lot of reference in processing defects in the country's large projects.Statistical indicators from the implementation of the results, analysis shows that to achieve even better than the regulatory requirements, and achieved the expected results.

scholarly journals The Hydrodynamic Dispersion Characteristics of Coral Sands

2019 ◽  
Vol 7 (9) ◽  
pp. 291 ◽  
Author(s):  
Xiang Cui ◽  
Changqi Zhu ◽  
Mingjian Hu ◽  
Xinzhi Wang ◽  
Haifeng Liu
Keyword(s):  
Particle Size ◽  
Porous Media ◽  
Flow Velocity ◽  
Molecular Diffusion ◽  
Dispersion Coefficient ◽  
Hydrodynamic Dispersion ◽  
Dispersion Characteristics ◽  
Factors Affecting ◽  
Mechanical Dispersion ◽  
Freshwater Aquifers

Dispersion characteristics are important factors affecting groundwater solute transport in porous media. In marine environments, solute dispersion leads to the formation of freshwater aquifers under islands. In this study, a series of model tests were designed to explore the relationship between the dispersion characteristics of solute in calcareous sands and the particle size, degree of compactness, and gradation of porous media, with a discussion of the types of dispersion mechanisms in coral sands. It was found that the particle size of coral sands was an important parameter affecting the dispersion coefficient, with the dispersion coefficient increasing with particle size. Gradation was also an important factor affecting the dispersion coefficient of coral sands, with the dispersion coefficient increasing with increasing d10. The dispersion coefficient of coral sands decreased approximately linearly with increasing compactness. The rate of decrease was −0.7244 for single-grained coral sands of particle size 0.25–0.5 mm. When the solute concentrations and particle sizes increased, the limiting concentration gradients at equilibrium decreased. In this study, based on the relative weights of molecular diffusion versus mechanical dispersion under different flow velocity conditions, the dispersion mechanisms were classified into five types, and for each type, a corresponding flow velocity limit was derived.

A self-learning propotional–integral–derivative control of grouting pressure using the back-propagation model

2018 ◽  
Vol 232 (8) ◽  
pp. 1090-1099
Author(s):  
Fengling Li ◽  
Zhixiang Hou ◽  
Juan Chen
Keyword(s):  
Control Method ◽  
Tracking Error ◽  
Back Propagation ◽  
Propagation Model ◽  
Test Method ◽  
Iteration Algorithm ◽  
Grouting Pressure ◽  
Geological Conditions ◽  
Self Learning ◽  
Derivative Control

For the security of grouting process of dam foundation, grouting pressure control is one of the most important problems. In order to avoid dangerous grouting pressure fluctuation and improve the control precision, a feedback propotional–integral–derivative control method was presented for the whole grouting system. Because the grouting pressure is affected by many factors such as grouting flow, grouts density, and geological conditions, the parameters of propotional–integral–derivative must be tuned. In this article, the adaptive tuning method is presented. The back-propagation artificial neural networks model was proposed to simulate the grouting control process, and sensitivity analysis algorithm based on orthogonal test method was adopted for the selection of input variables. To obtain the optimal propotional–integral–derivative parameters, an iteration algorithm was used in each sampling interval time and the discrete Lyapunov function of the tracking error. The simulation results showed that self-learning propotional–integral–derivative tuning was robust and effective for the realization of the automatic control device in the grouting process.

Research of Coupling Mechanism between Dynamic Damage of Fault Rock-Pillar and Gas Outburst in Front of Roadway

2014 ◽  
Vol 1078 ◽  
pp. 134-138 ◽  
Author(s):  
Zhi Rong Wang ◽  
Ya Kun Li ◽  
Zhong Yang Han
Keyword(s):  
High Pressure ◽  
Surface Damage ◽  
Layered System ◽  
Coupling Mechanism ◽  
Tunnel Face ◽  
Fault Rock ◽  
Gas Outburst ◽  
Rock Pillar ◽  
Geological Conditions ◽  
Structural Surface

For the particularity of rock and gas outburst in layered composite rock mass, taking the large outburst accident of the 21st down slope at +0 horizon in Zhengzhou Daping coal mine for example, we study the dynamic response characteristics of layered system and the whole process of rock and gas outburst under explosion load based on secondary development of ABAQUS user subroutine, and then innovatively put forward the new pattern “structural surface damage reinforcement” and “ribbon outburst of rock and gas”. The results are well consistent with 10.20 accident, which indicate the coupling relationship between rock damage and gas outburst under complicated geological conditions: (1) The weak structural surface damages dramatically and easy to form high pressure and high gradient of gas enrichment zone near the tunnel face under conditions of gas damaging erosion and blasting vibration; (2) The gas will break through the rock impedance and flow rapidly which result in rock burst once high pressure gas along structural face breakdown the safe rock pillar between fault and tunnel face.

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