scholarly journals Experimental Study on the Influence Mechanism of the Structural Plane to Rockbursts in Deeply Buried Hard Rock Tunnels

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Guangtan Cheng ◽  
Jian Zhang ◽  
Qiang Gao ◽  
Chuanxiao Liu
Keyword(s):  
Physical Simulation ◽  
Influence Factors ◽  
Biaxial Stress ◽  
Image Correlation ◽  
Major Influence ◽  
Small Scale ◽  
Structural Plane ◽  
Shear Rupture ◽  
Mining Projects ◽  
Rock Tunnels

During the excavation of a large number of deeply buried tunnels and mining projects, rockburst disasters occur frequently due to the complex geologic environment in deep underground, including high initial geostress, adverse tectonic actions, and excavation disturbance. Many rockbursts have been found to be induced by some small-scale structural planes in the area around the tunnels during the construction of Jinping II hydropower station. In order to study the influence mechanisms of the structural plane to rockbursts, the physical simulation tests of rockbursts under biaxial stress conditions are carried out using marble samples by considering different relative positions of the structural plane with tunnels, namely, in tunnel spandrel, in tunnel sidewall, and at the intersection with the tunnel. The digital image correlation (DIC) technique is used to trace the evolution of the deformation on the surface and the rockburst process of the marble sample. The results reveal that three types of rockbursts are identified, namely, fault-slip rockburst, split bulking rockburst, and shear rupture rockburst, and their evolution processes are reproduced. The presence of small-scale structural planes in the vicinity of deep tunnels could be one of the major influence factors in triggering rockbursts. The findings could provide helpful references for predicting the development process and the design of burst-resistant measures for this type of rockbursts.

Algicidal and Bactericidal Effect of Potassium Monopersulfate Compound on Eutrophic Water

2014 ◽  
Vol 707 ◽  
pp. 259-262 ◽  
Author(s):  
Ming Song Wu ◽  
Xin Yang Xu ◽  
Xun Xu ◽  
Yue Ting Zeng ◽  
Jing Nan Zhang ◽  
...  
Keyword(s):  
Contact Time ◽  
Influence Factors ◽  
Bactericidal Effect ◽  
Major Influence ◽  
Treatment Efficiency ◽  
Compound A ◽  
Eutrophic Water ◽  
Landscape Water ◽  
Algae And Bacteria

Algae and bacteria blooms in eutrophication in summer have made the quality of landscape water degradation. Treatment efficiency of potassium monopersulfate compound, a new kind of oxidation reagent, on killing algae and bacteria has been valued and the effect of influence factors, such as dosage, contact time and temperature are also discussed. The results indicated that potassium monopersulfate is appropriate for killing algae and bacteria in landscape water, dosage and contact time are the major influence factors. The contact time should be longer than 20min and the algicidal rate is higher when the temperature is above 20°C.

A New Heat Transfer Correlation for Supercritical RP-3 Flowing in Vertical Tubes

2017 ◽  
Author(s):  
Longyun Wang ◽  
Zhi Tao ◽  
Jianqin Zhu ◽  
Haiwang Li ◽  
Zeyuan Cheng
Keyword(s):  
Heat Transfer ◽  
Influence Factors ◽  
Hydrocarbon Fuel ◽  
Operating Conditions ◽  
Major Influence ◽  
Absolute Deviation ◽  
New Correlation ◽  
Vertical Tubes ◽  
Correction Terms ◽  
Good Agreement

A new empirical correlation for upward flowing supercritical aviation kerosene RP-3 in the vertical tubes is proposed. In order to obtain the database, numerical simulation with a four-component surrogate model on RP-3 and LS low Reynolds turbulence model in vertical circular tube has been performed. Tubes of diameter 2mm to 10mm are studied and operating conditions cover pressure from 3MPa to 6MPa. Heat flux is 500KW/m2, mass flow rate is 700kg/(m2·s). The numerical results on wall temperature distribution under various conditions are compared with experimental data and a good agreement is achieved. The existing correlations are summarized and classified into three categories. Three representative correlations of each category are selected out to evaluate the applicability in heat transfer of supercritical RP-3. The result shows that correlations concluded from water and carbon-dioxide do not perform well in predicting heat transfer of hydrocarbon fuel. The mean absolute deviation of them is up to 20% and predict about 80% of the entire database within 30% error bands. So a new correlation which is applicable to different working conditions for supercritical RP-3 is put forward. Gnielinski type has been adapted as the basis of the new correlation for its higher accuracy. In consideration of major influence factors of supercritical heat transfer, correction terms of density and buoyancy effect are added in. The new correlation has a MAD of 9.26%, predicting 90.6% of the entire database within ±15% error bands. The comparisons validate the applicability of the new correlation.

scholarly journals A Comparison of Isolated and Ducted Fixed-Pitch Propellers under Non-Axial Inflow Conditions

Aerospace ◽  
2020 ◽  
Vol 7 (8) ◽  
pp. 112
Author(s):  
Michael Cerny ◽  
Christian Breitsamter
Keyword(s):  
Flow Field ◽  
Unmanned Aerial Vehicles ◽  
Systematic Investigation ◽  
Major Influence ◽  
Small Scale ◽  
Highly Efficient ◽  
Strong Interest ◽  
Aerial Vehicles ◽  
Inflow Conditions ◽  
Fixed Pitch

A strong interest in highly-efficient, small-scale propeller configurations can be recognized, especially due to the currently growing number of and usage possibilities for unmanned aerial vehicles (UAVs). Although a variety of different propulsion concepts already exist on the market or are discussed in the literature, there is still a demand for a systematic investigation to compare such configurations, in particular, small-scale propellers with a fixed pitch, which are analyzed in this work. Therefore, different configurations of small-scale propellers with a fixed pitch are analyzed in this paper. They were operated as isolated single propellers and as ducted propellers in a cylindrical wing. Furthermore, due to their flight envelope, UAVs are likely to operate at highly inclined inflow conditions and even under reverse inflow. These non-axial inflow conditions have a major influence on the flow field around a propeller. In order to investigate this influence, all analyses were performed at a range of inflow angles in relation to the propeller axis from αdisc=0° to 180°.

scholarly journals Riemannian Spatio-Temporal Features of Locomotion for Individual Recognition

Sensors ◽  
2018 ◽  
Vol 19 (1) ◽  
pp. 56 ◽  
Author(s):  
Jianhai Zhang ◽  
Zhiyong Feng ◽  
Yong Su ◽  
Meng Xing ◽  
Wanli Xue
Keyword(s):  
Riemannian Manifold ◽  
Individual Recognition ◽  
Metric Learning ◽  
Influence Factors ◽  
Feature Representation ◽  
Geometric Feature ◽  
Major Influence ◽  
Temporal Features ◽  
Spatio Temporal ◽  
Spatial State

Individual recognition based on skeletal sequence is a challenging computer vision task with multiple important applications, such as public security, human–computer interaction, and surveillance. However, much of the existing work usually fails to provide any explicit quantitative differences between different individuals. In this paper, we propose a novel 3D spatio-temporal geometric feature representation of locomotion on Riemannian manifold, which explicitly reveals the intrinsic differences between individuals. To this end, we construct mean sequence by aligning related motion sequences on the Riemannian manifold. The differences in respect to this mean sequence are modeled as spatial state descriptors. Subsequently, a temporal hierarchy of covariance are imposed on the state descriptors, making it a higher-order statistical spatio-temporal feature representation, showing unique biometric characteristics for individuals. Finally, we introduce a kernel metric learning method to improve the classification accuracy. We evaluated our method on two public databases: the CMU Mocap database and the UPCV Gait database. Furthermore, we also constructed a new database for evaluating running and analyzing two major influence factors of walking. As a result, the proposed approach achieves promising results in all experiments.

Dynamic Response Analysis of Mortar Block under Blast Loading Using Digital Image Correlation

2018 ◽  
Vol 910 ◽  
pp. 161-166 ◽  
Author(s):  
Tei Saburi ◽  
Toshiaki Takahashi ◽  
Shiro Kubota ◽  
Yuji Ogata
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Strain Gauge ◽  
Strain Distribution ◽  
Three Dimensional ◽  
Image Correlation ◽  
Dynamic Strain ◽  
Small Scale ◽  
Response Analysis ◽  
Strain Profile

The dynamic strain distribution behavior of a mortar block blasting was experimentally investigated. A small-scale blasting experiment using a mortar block with well-defined property was conducted and the dynamic strain distribution on the mortal block surface was analyzed using a Digital Image Correlation (DIC) method to establish the effective method for investigating the relationship between blast design and fracture mechanism. The block was blasted by simultaneous detonation of Composition C4 explosive charges with an electric detonator in two boreholes. The behavior of the block surface was observed by two high-speed cameras for three-dimensional DIC analysis and it was also measured by a strain-gauge for comparison. The three-dimensional displacements of the free surface of the block were obtained and dynamic strain distributions were computed. A point strain profile extracted from the analyzed strain distribution data was compared with a directly observed strain profile by the strain gauge.

Response, Localization, and Rupture of Anisotropic Tubes Under Combined Pressure and Tension

2020 ◽  
Vol 88 (1) ◽  
Author(s):  
Martin Scales ◽  
Kelin Chen ◽  
Stelios Kyriakides
Keyword(s):  
Constitutive Model ◽  
Ductile Failure ◽  
Failure Criteria ◽  
Yield Function ◽  
Local Deformation ◽  
Al Alloys ◽  
Biaxial Stress ◽  
Image Correlation ◽  
Element Analysis ◽  
Von Mises

Abstract The inelastic response and failure of Al-6061-T6 tubes under combined internal pressure and tension is investigated as part of a broader study of ductile failure of Al-alloys. A custom experimental setup is used to load thin-walled tubes to failure under radial paths in the axial-hoop stress space. All loading paths achieve nominal stress maxima beyond which deformation localizes into a narrow band. 3D digital image correlation (DIC) was used to monitor the deformations in the test section and successfully captured the rapid growth of strain within the localization bands where they burst. The biaxial stress states generated are first used to calibrate the nonquadratic anisotropic Yld04-3D yield function (Barlat et al., 2005, “Linear Transformation-based Anisotropic Yield Functions,” Int. J. Plasticity, 21(5), pp. 1009–1039). The constitutive model is then incorporated through a UMAT into a finite element analysis and used to simulate numerically the experiments. The same calculations were performed using von Mises (VM) and an isotropic nonquadratic yield function. The material hardening responses adopted were extracted for each constitutive model from the necked zone of a tensile test using an inverse method. The use of solid elements captures the evolution of local deformation deep into the localizing part of the response, producing strain levels that are required in the application of failure criteria. The results demonstrate that the adoption of a nonquadratic yield function, together with a correct material hardening response are essential for large deformation predictions in localizing zones in Al-alloys. Including the anisotropy in such a constitutive model produces results that are closest to the experiments.

A Multiscale Finite Element Framework for Reactive Contaminant Transport in Heterogeneous Porous Media

2008 ◽  
Author(s):  
K. B. Nakshatrala ◽  
A. J. Valocchi
Keyword(s):  
Reactive Transport ◽  
Chemical Species ◽  
Interfacial Area ◽  
Heterogeneous Porous Media ◽  
Major Influence ◽  
Small Scale ◽  
Full Resolution ◽  
Scale Heterogeneity ◽  
Reactive Pollutant ◽  
Reservoir Description

Mixing of chemical species across plume boundaries has a major influence upon the fate of the reactive pollutant in the subsurface. Small-scale heterogeneity leads to irregular plume boundaries which enhances mixing-controlled reactions through increasing the interfacial area of the plume. Therefore, it is crucial to capture this small-scale heterogeneity in order to properly model reactive transport. Unfortunately, computational limitations do not permit full resolution of the smallest scales of heterogeneity as the size of geomodels used for reservoir description typically exceeds by several orders of magnitude the capabilities of conventional reservoir simulators. Thus, it is necessary to use a coarse numerical grid, particularly for the cases with a large number of reactive species.

scholarly journals A Novel Comprehensive Kinematic and Inverse Dynamic Model for the Flybar-Less Swashplate Mechanism: Application on a Small-Scale Unmanned Helicopter

Symmetry ◽  
2020 ◽  
Vol 12 (11) ◽  
pp. 1849
Author(s):  
Jianbo Liu ◽  
Rongqiang Guan ◽  
Yongming Yao ◽  
Hui Wang ◽  
Linqiang Hu
Keyword(s):  
Dynamic Model ◽  
Flight Control ◽  
Virtual Work ◽  
Influence Factors ◽  
Parallel Manipulators ◽  
Small Scale ◽  
Unmanned Helicopter ◽  
Inverse Dynamic ◽  
Inverse Dynamic Model ◽  
Helicopter Flight

In this paper, we propose a novel kinematic and inverse dynamic model for the flybar-less (FBL) swashplate mechanism of a small-scale unmanned helicopter. The swashplate mechanism is an essential configuration of helicopter flight control systems. It is a complex, multi-loop chain mechanism that controls the main rotor. In recent years, the demand for compact swashplate designs has increased owing to the development of small-scale helicopters. The swashplate mechanism proposed in this paper is the latest architectures used for hingeless rotors without a Bell-Hiller mixer. Firstly, the kinematic analysis is derived from the parallel manipulators concepts. Then, based on the principle of virtual work, a methodology for deriving a closed-form dynamic equation of the FBL swashplate mechanism is developed. Finally, the correctness and efficiency of the presented analytical model are demonstrated by numerical examples and the influence factors of the loads acted on actuators are discussed.

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