The reasonable prediction of ground frost heave provides guiding significance for tunnel construction that uses artificial ground freezing technique. Single-pipe freezing theory, which considers the ...freezing point of soil and assumes the constant surface temperature of a freezing pipe, is suggested for solving the radius of the freezing front before the closure of the frozen wall. By contrast, the radius of the freezing front after the closure of the frozen wall can be calculated using flat-panel freezing theory, which considers the freezing point of soil and determines the average temperature of the freezing pipe circle. On the basis of these suggestions and the analytical prediction proposed by Cai et al. (2014), an improved analytical prediction of ground frost heave was established by the stochastic medium theory according to the formation process of the frozen wall. The improved analytical prediction was applied to an actual tunnel freezing project. Then, the heaving and horizontal displacements of the ground surface are obtained, which agree well with the field-measured data. The effectiveness and practicality of the improved analytical prediction are verified in this study.
Polycrystals are aggregates of numerous tiny crystallites whose orientation distributions are described by the orientation distribution function (ODF). Since crystal lattices are anisotropic, the ...properties of polycrystals depend on the ODF. The texture coefficients, which can be measured by X-ray diffraction, are the expanded coefficients of the ODF under the Wigner
D
-function bases. The texture coefficients contain the information of crystalline orientation distributions and crystal symmetries on polycrystals. Herein an orientation-dependent function is introduced to present the properties of polycrystals. A general expression of the orientation-dependent function for polycrystals is given. The general expression with the texture coefficients can be widely used to determine the properties of polycrystals. As applications of the general expression, the direction-dependent function, the elastic strain energy, and the yield function for anisotropic cubic polycrystals are given in simple and explicit forms.
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•Making full use of the feature to enhance the feature representation ability.•Improving the recognition accuracy of the anomalous spectral data.•Proposing a novel qualitative ...detection neural network for the blend fabrics.•Utilizing 5 neural networks in parallel is used.
Near Infrared spectroscopy (NIRS) qualitative analysis technology has shown excellent development potential in the field of blend fabrics. However, the qualitative detection method based on the convolutional neural network (CNN) is difficult to accurately extract the feature of the spectral data, which will lead to missing detection or false detection; when using deep learning to build a qualitative detection model, due to interference of the external environment and other factors, the spectral data collected may have outliers, this means that the knowledge generalization on anomalous testing data, which may have a different distribution of that of the training set, is not trivial, which will also lead to missing detection or false detection. To solve the above problems, this paper proposes a novel qualitative detection neural network by analyzing the near infrared spectral data of blend fabrics. Firstly, we remove the convolutional layer and pooling layer of the CNN, making full use of the feature to enhance the feature representation ability of the model. Secondly, adding the L1 norm of the feature coefficients as a penalty term to the loss function to force those features with high redundancy to become weaker. Thirdly,
in order to improve the recognition accuracy of the anomalous spectral data and minimize the model uncertainty, an ensemble machine learning approach utilizing 5 neural networks in parallel is used. To show the superiority of our proposed method, the existing methods are used as competitive methods to compare with our method. Our homemade dataset contains 3482 samples of blend fabrics with 9 different compositions. The results show that the Micro-F1-score, Micro-Specificity, Weight-F1-score, and Weight-Specificity of this method respectively 99.71%, 99.96%, 99.73%, and 99.99%, the results further confirm the method has higher analysis accuracy and stability. In addition, the method proposed in this paper can greatly improve the recognition accuracy of the anomalous spectral data. It has important practical value in the qualitative detection of blend fabrics.
The excavation works at underground mines create excavation damage zone (EDZ) in surrounding rocks around roadway geometry. The EDZ depth is a critical parameter for stability analysis, risk ...assessment support design and toxic waste leakage. This paper proposed an innovative EDZ depth prediction based on a modified nonlinear Mohr failure criterion and modification of conventional analytical solution by means of perturbation method. A set of cyclic loading tests of surrounding rock of roadways are conducted, and a modified Mohr failure criterion of rocks under cyclic loading path of TBM excavation is established on the basis of test results. Moreover, perturbation method was introduced for enhancing calculation accuracy. In order to verify the proposed analytical solution, a set of in situ digital panoramic borehole camera image monitoring was carried out within the roadways and the monitoring results correlated well with the proposed analytical solution. The EDZ geometries of roadways in deep mines are typically oval, and the EDZ depth is influenced by ground stress magnitude, lateral coefficient and support stress significantly. Through the proposed analytical solution, a more accurate prediction of EDZ depth of roadways can be obtained conveniently before the excavation works.
Some physical properties of crystals differ in direction n because crystal lattices are often anisotropic. A polycrystal is an aggregate of numerous tiny crystallites. Unless the polycrystal is an ...isotropic aggregate of crystallites, the physical properties of the polycrystal vary with n. The direction-dependent functions （DDF） for crystals and polycrystals are introduced to describe the variations of the physical properties in direction n. Until now there are few papers dealing systematically with relations between the DDF and the crystalline orientation distribution. Herein we give general expressions of the DDF for crystals and polycrystals. We discuss the applications of the DDF in describing the physical properties of crystals and polycrystals.
The orientation distribution of crystallites in a polycrystal can be described by the orientation distribution function (ODF). The ODF can be expanded under the Wigner D-bases. The expanded ...coefficients in the ODF are called the texture coefficients. In this paper, we use the Clebsch-Gordan expression to derive an explicit expression of the elasticity tensor for an anisotropic cubic polycrystal. The elasticity tensor contains three material constants and nine texture coefficients. In order to measure the nine texture coefficients by ultrasonic wave, we give relations between the nine texture coefficients and ultrasonic propagation velocities. We also give a numerical example to check the relations.
Tunnel Boring Machines (TBMs) are a cutting-edge excavating equipment, but are barely applied in underground coal mines. For TBM excavation projects involving the Zhangji coal mine, the surrounding ...rock properties, stress field, cross section geometry, as well as the excavation-induced stress path of TBM-excavated coal mine roadways are different from those of traditional tunnels or roadways. Consequently, traditional roadway supporting technologies and experiences cannot be relied on for this project. In order to research an appropriate supporting pattern for a TBM-excavated coal mine roadway, first of all, the constitutive model of roadway surrounding rocks was derived, and a rock failure criterion was proposed based on rock mechanical tests. Secondly, a three-dimension finite element model was established and computer simulations under three different supporting patterns were conducted. Stress redistribution, roadway convergence, and excavation damage zone ranges of surrounding rocks under three different support patterns were analyzed and an optimal support design of the TBM-excavated roadway was made based on simulation results. During roadway excavation, convergence gauge and rock bolt dynamometers were installed for monitoring roadway convergence and the axial forces of rock bolts. The in-situ monitoring results verified the validity of roadway supporting designs.
As the pressure and heat transfer boundaries between primary and secondary sides, the steam generator (SG) should be integrated during operation. However, SG suffers from the problems including ...vibration, wear, fatigue and corrosion, which will lead to the degradation of tubes and other components and may lead to the failure of SG. The research on the degradation of SG is associated with many disciplines, including thermohydraulics, structural mechanics, water chemistry and materials science, among these, the thermohydraulics are the foundation of other analysis. In the current work, SGTHPorous3D, a 3D steam generator thermohydraulics analysis code based on twofluid porous media model, was developed for the prediction of 3D thermohydraulics in the Utube SG (UTSG) and helical coiled SG (HCSG). First, the twofluid porous media model for the straight tube, U-bend and helical tube bundle was proposed for the general application of UTSG and HCSG. A velocity projection method was employed to estimate the flow resistance and heat transfer for inclined sweeping flow over different types of tubes. With these models, the 3D numerical strategy based on coarse mesh was developed for the shell side of SG. Second, as for the tube side flow, the parallel 3D multichannel model was used to simplify the numerous spatially distributed tubes. The effects of centrifugal force were considered by employing the flow resistance and heat transfer maps specially developed for Ubend and helical shaped tubes. Finally, a data mapping method was also developed for the tubetoshell side heat transfer between cells of different spatial scales. A partial relaxation scheme was used to accelerate the convergence of coupled heat transfer, where the heat flux was relaxed while the temperature wasn’t. The experiment data from the Westinghouse MB2 UTSG, the KAERI HCSG and the SJTUNETH HCSG were used for code validation. The SGTHPorous3D code was applied to predict the 3D thermalhydraulics parameters in the CAP1400 SG. The distributions of thermal-hydraulics parameters for each phase and the mixture phase were obtained. High non-uniformity can be observed for the flow and heat transfer parameters. The ratio between heat released in the hot side and cold side is as large as 2.7. The crossflow energy related to the flowinduced vibration is also derived to find the possible location of tube damage. The most probable location for a potential tube rupture locates at approximate 04 rad in the hot side. The results show that the SGTHPorous3D can predict the 3D thermalhydraulics parameters in both of the tube and shell sides of UTSG and HCSG, which provides support for the heat transfer design and flowinduced vibration analysis for the SGs.
Plain concrete is susceptible to cracking under aggressive environment such as in freezing shaft. And addition of steel fibres in plain high strength concrete is proved to be effective in cracking ...resistance and brittleness improvement, etc. This paper presents results of experimental investigation carried out to study the mechanical properties of steel fibre-reinforced concrete having volume fractions of 0.38%, 0.51% and 0.64% for two types of fibres respectively. The results of this study revealed that there is an increase for all the mechanical properties such as compressive strength, split tensile strength, modulus of elasticity and flexural strength. Enhancement for split tensile strength and flexural strength is more evident than compressive strength.
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