scholarly journals Study of the Mechanism of Fracture Grouting in Deeply Buried Rock Strata Based on Bingham Fluid Slurry

2019 ◽  
Vol 2019 ◽  
pp. 1-10 ◽  
Author(s):  
Xiangyang Liu ◽  
Hua Cheng ◽  
Jian Lin ◽  
Chuanxin Rong ◽  
Mingjing Li ◽  
...  
Keyword(s):  
Flow Rate ◽  
Pressure Coefficient ◽  
Single Fracture ◽  
Time Varying ◽  
Grouting Pressure ◽  
Fracture Grouting ◽  
Material Fracture ◽  
Rock Mechanical Properties ◽  
Engineering Practices ◽  
Rock Strata

In view of the fact that the theory of fracture grouting in deeply buried rock strata seriously lags behind engineering practices, a circular fracturing diffusion model of a single fracture was established by considering numerous influencing factors of deeply buried rock strata, such as the crustal stress characteristics, rock mechanical properties, and time-varying characteristics of the serous viscosity. By setting the stress intensity factor KI equal to the material fracture toughness KIC at the fracture tip as the criterion for fracturing, the diffusion equation for the fracture grouting was derived and verified experimentally. Theoretical analysis shows that the fracture grouting pressure P0 is linearly proportional to the depth of the strata H and the lateral pressure coefficient k. The time-varying characteristics of the serous viscosity have an important influence on the grouting pressure and the diffusion radius. Its early impact is small, while its later impact is large. The diffusion radius of the grouting is indirectly proportional to the grouting pressure and the grouting flow rate. In order to increase the diffusion radius of the grouting, the grouting pressure and the grouting flow rate should be increased simultaneously. In order, the main factors influencing the diffusion radius of the fracture grouting are the time-varying characteristics of the serous viscosity, the grouting pressure, the grouting flow rate, and the depth of the strata.

scholarly journals Study on Fracturing and Diffusion Mechanism of Nonslab Fracturing Grouting

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Hua Cheng ◽  
Xiangyang Liu ◽  
Jian Lin ◽  
Liangliang Zhang ◽  
Mingjing Li ◽  
...  
Keyword(s):  
Rock Mass ◽  
Coupling Effect ◽  
Fractured Rock ◽  
Diffusion Mechanism ◽  
Channel Width ◽  
Single Fracture ◽  
Time Varying ◽  
Rock Layer ◽  
Validity And Reliability ◽  
Grouting Pressure

The coupling effect of a slurry and the fractured rock layer controls a spatial attenuation of the fracture channel width and grouting pressure from a grouting hole to the slurry top of fracture diffusion. This paper comprehensively considers the influencing factors such as the mechanical properties of the injected rock mass and the time-varying characteristics of the serous viscosity and introduces the control equation of the fracture channel width to establish a single-fracture nonslab fracturing grouting model. Combining the motion law of the slurry with the extension form of fracture, the equation of slurry diffusion motion, considering the fracture geometry and the time-varying characteristics of the serous viscosity, is derived. Comparing this equation with the existing theories and experiments, the validity and reliability of the theory are verified. In this paper, the effects of rock elastic modulus, slurry viscosity, and grouting rate on the fracturing grouting diffusion law of rock mass are analyzed. It is pointed out that when fracturing grouting in deep rock layers, a larger initial grouting rate and grouting pressure should be selected in the early stages of grouting to generate or penetrate fractures in the rock layer. Also, when the grouting pressure is stable, it is appropriate to increase the viscosity so that the slurry can quickly gel in the fractures thus sealing the fractures.

Influences of Splitter Blades on the Centrifugal Fan Performances

1989 ◽  
Author(s):  
Lichuan Gui ◽  
Chuangang Gu ◽  
Hongshou Chang
Keyword(s):  
Solution Method ◽  
Pressure Coefficient ◽  
Internal Flow ◽  
Experimental Result ◽  
Centrifugal Fan ◽  
Fan Performance ◽  
Load Distributions ◽  
Result Show ◽  
Engineering Practices ◽  
Approximate Solution Method

Centrifugal fan and compressors with splitter blades are widely utilized in engineering practices. A detail investigation of the influences of splitter blades on a forward-curved centrifugal fan performances is presented in the paper. The study includes two parts: experiment and numerical calculation. The experiments were produced in a specific impeller with adjustable splitter blades in order to get the performances in different conditions. The internal flow field in the impeller was calculated by means of FEASM (Finite Element Approximate Solution Method, Gu, 1984). The experimental result show that changing the circumferential positions of the splitter blades has a noticeble influence on the fan performance, the incidence of splitter blades also has a certain effect on it, and properly lengthened splitter blades can raise the total pressure coefficient. The velocity and load distributions on the blade surfaces calculated can be used to analyse the phenomena above satisfactorily.

scholarly journals Experimental Investigation on the Law of Grout Diffusion in Fractured Porous Rock Mass and Its Application

Processes ◽  
2018 ◽  
Vol 6 (10) ◽  
pp. 191 ◽  
Author(s):  
Donghai Jiang ◽  
Xianzhen Cheng ◽  
Hengjie Luan ◽  
Tongxu Wang ◽  
Mingguang Zhang ◽  
...  
Keyword(s):  
Rock Mass ◽  
Permeability Coefficient ◽  
Pressure Coefficient ◽  
Porous Rock ◽  
Cement Ratio ◽  
Coal Resources ◽  
Water Cement Ratio ◽  
Grouting Pressure ◽  
Study Results ◽  
Residual Coal

Because of the limitation of mining techniques and economic conditions, large amounts of residual coal resources have been left in underground coal mines around the world. Currently, with mining technology gradually developing, residual coal can possibly be remined. However, when residual coal is remined, caving areas might form, which can seriously affect the safety of coal mining. Hence, grouting technology is put forward as one of the most effective technologies to solve this problem. To study the grouting diffusion in fractured rock mass, this paper developed a visualization platform of grouting diffusion and a three-dimensional grouting experimental system that can monitor the grout diffusion range, diffusion time and grout pressure; then, a grouting experiment is conducted based on this system. After that, the pattern of the grouting pressure variation, grout flow and grout diffusion surface are analyzed. The relationship among some factors, such as the grouting diffusion radius, compressive strength of the grouted gravel, porosity, water-cement ratio, grouting pressure, grouting time, permeability coefficient and level of grout, is quantitatively analyzed by using MATLAB. The study results show that the flow pattern of the grout in fractured porous rock mass has a parabolic shape from the grouting hole to the bottom. The lower the level is, the larger the diffusion range of the grout is. The grouting pressure has the greatest influence on the grouting diffusion radius, followed by the grouting horizon and water-cement ratio. The grouting permeability coefficient has the least influence on the grouting diffusion radius. The grout water-cement ratio has the greatest influence on the strength of the grouted gravel, followed by the grouting permeability. The grouting pressure coefficient has the least amount of influence on the grouting diffusion radius. According to the results, the grouting parameters are designed, and a layered progressive grouting method is proposed. Finally, borehole observation and a core mechanical property test are conducted to verify the application effect. This grouting technology can contribute to the redevelopment and efficient utilization of wasted underground coal resources.

GPC Control on Exhaust Gas in Regenerative Furnace Based on Feedforward of Hearth Temperature and Air Flow

2013 ◽  
Vol 364 ◽  
pp. 294-298
Author(s):  
Xue Gang Sun ◽  
Zheng Gan Zhou
Keyword(s):  
Predictive Control ◽  
Flow Rate ◽  
Air Flow ◽  
Generalized Predictive Control ◽  
Exhaust Gas ◽  
Time Varying ◽  
Important Indicator ◽  
Exhaust Temperature ◽  
Rate Of Combustion ◽  
Regenerative Furnace

Exhaust temperature is an important indicator in regenerative furnace with characteristics of nonlinearity, time-varying and large inertia. Also, it is affected by the hearth temperature and flow rate of combustion air, which makes it hard to be well controlled by traditional methods, such as PID and etc. In this paper, a strategy of generalized predictive control (GPC) integrated with feedforward of hearth temperature and air flow is presented to optimize the exhaust temperature control. Practices show that the control index is more stable and errors are obviously narrowed.

Fluid Flow and Solute Transport though a Fracture Intersecting a Canister - Analytical Solutions for the Parallel Plate Model

2003 ◽  
Vol 807 ◽  
Author(s):  
L. Liu ◽  
I. Neretnieks
Keyword(s):  
Fluid Flow ◽  
Solute Transport ◽  
Flow Rate ◽  
Analytical Solutions ◽  
Parallel Plate ◽  
Spent Nuclear Fuel ◽  
Volumetric Flow Rate ◽  
Single Fracture ◽  
Plate Model ◽  
Specific Scenario

ABSTRACTIn this paper, we are concerned with a specific scenario where a large fracture intersects, at its center, a canister that contains spent nuclear fuel. Assuming that a nuclide is free to release from the canister into groundwater flowing through the fracture, a detailed formulation of the volumetric flow rate and the equivalent flow rate are made for the parallel plate model. The formulas proposed have been validated by numerical examinations; they are not only simple in forms but also universal in applications where the flow may be taken normal, inclined or parallel to the axis of the canister. Of great importance, they provide a convenient way to predict the average properties of fluid flow and solute transport through a single fracture with spatially variable apertures.

scholarly journals DEVELOPMENT OF AERODYNAMIC DIAGRAMS OF HIGH-LOADED REVERSE AXIAL FANS

2020 ◽  
Vol 2 ◽  
pp. 72-81
Author(s):  
Pavel V. Kosykh
Keyword(s):  
Flow Rate ◽  
Total Pressure ◽  
High Speed ◽  
Guide Vane ◽  
Pressure Coefficient ◽  
Aerodynamic Characteristics ◽  
Inlet Guide Vane ◽  
Ansys Software ◽  
Axial Fans ◽  
Limiting Values

Present-day achievements in the field of strength calculation and structural optimization allow creating main mine fans with higher tip speed than in currently used machines. The paper considers the features of calculating the aerodynamic diagrams of mine reverse axial fans with a tip speed over 200 m/s. It is shown that at such speed it is possible to obtain high-flow fans with significantly smaller dimensions than their existing counterparts. Aerodynamic diagrams with high reverse characteristics (flow rate of more than 0.7 from the direct mode for the network of the same aerodynamic characteristics as in direct mode) are developed. The aerodynamic characteristics of the developed diagrams are calculated in the ANSYS software package. It is shown that an increase in the tip speed contributes to an increase in reverse properties of fans compared to less high-speed machines designed for the same total pressure. The limiting values of axial velocity coefficient and pressure coefficient are determined, at which it is possible to obtain a fan without an inlet guide vane, with a monotonic dependence of total pressure on flow rate.

scholarly journals Research on Performance Evaluation of Tidal Energy Turbine under Variable Velocity

Energies ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 6313
Author(s):  
Chuhua Jiang ◽  
Xuedao Shu ◽  
Junhua Chen ◽  
Lingjie Bao ◽  
Hao Li
Keyword(s):  
Performance Evaluation ◽  
Flow Velocity ◽  
Flow Rate ◽  
Tidal Current ◽  
Evaluation System ◽  
Average Power ◽  
Tidal Energy ◽  
Time Varying ◽  
Practical Applications ◽  
Sea Area

Aiming at the performance evaluation problem of tidal energy turbines in the application of periodic time-varying flow velocity, with the goal of maximizing the efficiency of energy harvesting in practical applications, an evaluation system combining the characteristics of flow velocity changes in practical applications is proposed. After long-term monitoring of tidal current flow velocity in the applied sea area, the actual measured tidal current periodic flow velocity is divided into several flow velocity segments by using statistical segmentation, and the evaluation flow velocity of each flow velocity segment and its time proportion in the tidal current cycle are obtained. A test device with constant torque regulation is built, and capture power tests of different torque loads are carried out under each evaluation flow rate. After comparison, the maximum captured power at each evaluation flow rate is determined. We calculate the weight based on the time proportion of each evaluation flow velocity and obtain the turbine average power of the tidal cycle, thereby evaluating the overall energy capture performance of the turbine under the periodic time-varying flow velocity. Finally, the application test of the turbine in the actual sea area shows that the thin-walled airfoil turbine is more suitable for the sea area, which is the same as the pool evaluation result. The result shows that the evaluation system is reliable and effective and has significance for guiding practical engineering.

scholarly journals Grouting Reinforcement Technique in Wind Oxidation Zone by Power Law Superfine Cement Slurry Considering the Time-Varying Rheological Parameters

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Dengxing Zhu ◽  
Yu Guo ◽  
Wei Wang ◽  
Gangye Guo ◽  
Tieliang An
Keyword(s):  
Power Law ◽  
Coal Mine ◽  
Effective Diffusion ◽  
Oxidation Zone ◽  
Rheological Parameters ◽  
Time Varying ◽  
Cement Slurry ◽  
Permeability Characteristics ◽  
Grouting Pressure ◽  
Roof Strata

With the recovery of the wind oxidation zone in 13116 working face of Gubei Coal Mine as the engineering background, the occurrence condition of coal seam and the bedrock wind oxidation zone characteristics were analyzed. On this basis, the time-varying rheological parameters of superfine cement slurry and the permeability characteristic parameters of roof strata in wind oxidation zone were measured; then, a grout diffusion equation was established with the parameters obtained previously for the permeability characteristics of roof strata in the wind oxidation zone of Gubei Coal Mine. The grouting design was applied in actual engineering projects and its engineering effect has been proved to be satisfactory. The results indicate that superfine cement slurry whose water-cement ratio is 0.6 is a typical power-law slurry consistent with time-varying rheological parameters. It has better rheological properties during pumpable period, and its rheological parameters can be controlled by highly dispersive nano-SiO2 and polycarboxylate superplasticizer. For grouting in wind oxidized zone, comprehensive consideration must be given to effective permeability Ke, porosity  ∅ , and time-varying rheological parameters c0, k, and n. To realize effective diffusion of grouting in coal and rock mass, grouting pressure and diffusion time must be reasonably designed rather than excessively increased.

scholarly journals Instabilities in the Flow of a Boiling Liquid

1964 ◽  
Vol 86 (2) ◽  
pp. 213-217 ◽  
Author(s):  
A. H. Stenning
Keyword(s):  
Heat Transfer ◽  
Flow Rate ◽  
Oscillatory Flow ◽  
Density Ratio ◽  
Critical Value ◽  
Time Varying ◽  
Boiling Liquid

The time-varying flow of a boiling liquid through a series of ducts and heaters is considered for the case where the flow rate is controlled by a downstream orifice. It is shown that oscillatory flow will exist for a variety of configurations, provided that the density ratio across the system exceeds a critical value which depends on the geometry and the heat-transfer relationship.

scholarly journals A new approach for the fracture grouting pressure in soil mass

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401878643
Author(s):  
Zhi-bin Wang ◽  
Jin-feng Zou ◽  
Hai Yang
Keyword(s):  
Large Deformation ◽  
Failure Criterion ◽  
Deformation Theory ◽  
Small Deformation ◽  
Soil Mass ◽  
Parameter Analysis ◽  
Strength Failure ◽  
Grouting Pressure ◽  
Fracture Grouting ◽  
Coulomb Failure Criterion

This study focuses on analytical solutions of the fracture grouting pressure. Based on the cavity expansion and fracture grouting mechanism, the small deformation in the elastic zone, large deformation in the plastic zone, and non-associated flow rules are assumed. The solutions of the fracture grouting pressure based on the Unified Strength failure criterion, spatial mobilized plane criterion, Mohr–Coulomb failure criterion, and modified Cambridge model (MMC) are proposed for the large-deformation and small-deformation assumptions, respectively. A parameter analysis was conducted to analyze the differences between large-deformation and small-deformation theories. A comparison of the local test data with theoretical results reveals that the Cambridge model is more suitable for weakly consolidated soil and that the Mohr–Coulomb theory is suitable for over-consolidated soil. For all yield criteria in the study, the analysis indicates that the large-deformation theory has more reliable results than the small-deformation theory. The results in this study can direct the design and operation of fracture grouting.

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