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Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the dynamic response of high-speed railway bridge under flood, a two-span high-speed railway simple-supported beam bridge with unequal 32-meter pier height is studied. A three-dimensional hydrodynamic model of the substructure and a finite element model of the bridge under flooding are built up to analyze the law of flow field distribution around and the hydrodynamic pressure. The influences of the change of velocity and height of flood and the foundation scour depth on the dynamic response of bridge and internal force of pile foundation are revealed. The study shows that: (1) The law of flow field distribution is basically the same when the bridge substructure is impacted by the flood with different velocities; (2) When the flood velocity exceeds 3 meters per second, the influence of the hydrodynamic pressure on the substructure cannot be ignored, and the pressure is positively correlated with velocity and height of the flood; (3) The depth of foundation scour has a significant influence on the hydrodynamic pressure. But when the depth of foundation scour is increased after the bearing platform is exposed, the increase of the pressure is not obvious; (4) When the bridge is impacted by the flood, the overall law of the dynamic response of the bridge with time is basically the same. The response is as follows: When t = 1.06 s, the lateral vibration acceleration of pier top reaches the peak value; When t = 1.16 s, the lateral displacement of pier top reaches the peak value. After the lateral displacement and vibration acceleration reach their peak values, they both tend to attenuate decay rapidly and periodically. With the velocity and height of flood increasing, the peak values and final stable values of displacement and acceleration at prier top as well as the pile bending moment increase; (5) With the increase of foundation scour depth, both the dynamic response and the pile bending moment increase, but the negative bending moment area of pile foundation is more sensitive to the impact of foundation scour depth. [ABSTRACT FROM AUTHOR]

During the long-term operation of high-speed railway in our country, affected by various factors such as surrounding environment changes and human engineering activities, large lateral deviation occurs in some line bridge sections, which seriously affects the normal and safe operation of the train and needs to be rectified urgently. Based on the analysis of the principle of bridge rectification by high pressure jet grouting, the theoretical calculation model of bridge rectification is established, and the differential equations of pile deflection, rotation angle, bending moment and shear force under the high pressure jet grouting rectification mode and the analytical formula of pier top displacement are deduced based on the elastic foundation beam theory. Then,by comparing the calculated displacement at the top of the pier with the actual offset of the line,the feasibility of high pressure jet grouting technology for bridge rectification is analyzed, and the rectification effect is verified by typical engineering cases on site. Research shows that the top displacement of pier is related to foundation coefficient and excess pore water pressure generated by high pressure jet grouting; when foundation coefficient and excess pore water pressure take 1 MPa/ m and 80.3 kPa respectively,the top theoretical calculated displacement of pier is 81.8 mm,which is much larger than the actual deviation of ballastless track line of common high speed railway;In the bridge rectification project of a high speed railway Songjiang Grand Bridge,the displacement at the top of the pier calculated by the average value of the measured excess pore water pressure 30.4 kPa 6. 4~31. 0 mm,which is also greater than the maximum deviation 18.2 mm of the line, indicating that the high pressure jet grouting technology is feasible for bridge rectification theoretically;After rectification construction,the bridge and track structure are stable,the line alignment is smooth,and there is no abnormality in the normal speed operation for many years. The theory and practice have proved that the high pressure jet grouting method is a practical and feasible technical measure for bridge rectification. [ABSTRACT FROM AUTHOR]

Copyright of Atomic Energy Science & Technology is the property of Editorial Board of Atomic Energy Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Shanghai Jiao Tong University (1006-2467) is the property of Journal of Shanghai Jiao Tong University Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Partial cable-stayed bridges have the advantages of high rigidity, good economy and convenient construction. In recent years, they have been widely used in high-speed railway, but most of them are two-tower structures. In this paper, based on the main bridge of Ji'nan Yellow River Bridge on Zhengzhou-Ji'nan Railway, the structural system, side-to-middle span ratio and key parameters of beam-tower-cable are analyzed and studied for the long-span, five-tower, four-span and large-span partial cable-stayed bridge on high-speed railway. Through comprehensive comparison and study, the structure system of tower pier consolidation is selected for the Yellow River Bridge, which has the advantages of partial release of temperature force, bridge stiffness and track surface irregularity index to meet the requirements of ballastless track on high-speed railway. Vibration-reducing and isolation measures can be adopted for beam section, effectively reducing seismic force and improving overall economy of bridge. The main bridge uses a smaller ratio of mid-span at the edge to meet the requirement of no auxiliary span for flood control, and can effectively reduce the corner at the end of the beam, avoiding the increase of the investment of the whole bridge due to the use of large girder height. When the height of the tower is 38 m, the increase of the height of the tower can significantly reduce the internal force of the beam, but the deformation under temperature load will increase accordingly. Therefore, the selection of the height of the tower should take into account the structural forces and the requirements of track irregularity. AT - 61 cable is used. Increasing cable size has little effect on bridge rigidity, but it can significantly reduce beam bending moment, but increase beam irregularity and residual creep deformation. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the influence of shape memory alloy (SMA) on the seismic response of railway self-centering piers, the SMA restrainer element is added to the verified two-spring model. Taking a railway bridge pier as the engineering background, the numerical analysis model is established based on OpenSees platform. By inputting three strong earthquake records, the influence of SMA restrainer on the pier is analyzed by nonlinear time history analysis method. The influence of the initial clearance and the change of the initial prestress of the key parameters of the SMA restrainer device on the displacement of the pier top and the bending moment of the pier bottom is discussed, and compared with the prestressed reinforcement restrainer. The results show that under ordinary ground motion El-Centro and Taft waves, the displacement at the top of the self-centering pier decreases with the decrease of the initial gap δ of the restrainer device, and the bending moment at the bottom of the pier increases with the decrease of the initial gap δ. With the increase of the initial preload of the SMA restrainer, the displacement of the top of the self-centering pier decreases and the bending moment of the bottom of the pier increases. The influence of SMA restrainer on the seismic response of self-centering piers under near-fault ground motion Northridge is complex. Under three strong earthquake records, compared with the prestressed reinforcement restrainer, SMA restrainer will reduce the bending moment of the pier bottom and increase the horizontal displacement of the pier top. [ABSTRACT FROM AUTHOR]

Based on the newly-built underpass tunnel of Nijiaqiao station in Chengdu Metro Line 8, which passes right under metro station of Line 1, and numerical simulation method is performed to compare and analyze the influence on the newly-built and existing structure between removing the temporary lining first and second lining first. Based on the working condition of "removal of temporary lining before the secondary liner", the plan of removing the support is further analyzed. Moreover, some results are verified by the on-site monitoring data. The main results show that: in the case of second lining first, the bending moment and settlement of the existing station and the preliminary lining bending moment and the secondary lining settlement of the new channel caused by the removal of the temporary lining are not obvious; for the case of temporary lining first, after all the temporary linings are removed at one time, the bending moments of existing and new structures change greatly along the section. In terms of structural settlement, the maximum sudden settlement of the preliminary lining of existing stations and new channels after the removal of temporary lining reaches 4.86 mm and 7.30 mm respectively. Basing on removing the temporary lining first, the most disadvantageous part occurs in the longitudinal middle of the underpass when the temporary lining is removed in sequence and removed by jumping. The settlement of the preliminary lining of the newly-built channel caused by the jumping is larger than that of the sequential dismantling, but its construction efficiency is higher. The specific method should be reasonably selected according to the construction safety standard and the economic requirements. [ABSTRACT FROM AUTHOR]

In order to study the applicability of assembled piers in high-speed railway bridges, the assembled piers in Guba Bridge of Beijing-Xiong'an High-speed Railway are taken as the prototype, and finite element numerical simulation is carried out with ANSYS software on the basis of full-scale quasi-static test, and the results are compared with the experimental data. The verified finite element model is used to analyze the seismic performance of the actual assembled bridge pier and the time-history response of a two-span continuous beam bridge with assembled bridge pier under seismic waves. The research shows that the hysteretic curves, skeleton curves, stiffness degradation characteristics, energy dissipation capacity and residual deformation of both the test assembly pier and the actual bridge assembly pier are basically the same and are not significantly different from those of the cast-in-situ pier, indicating that the sleeve connection does not have significant impact on the hysteretic performance and restoring force characteristics of the pier. Considering the pile-soil effect, the hysteretic area of the assembly pier decreases, the initial stiffness and hysteretic energy consumption decrease by 36% and 23.5% respectively. The natural frequency of the continuous beam bridge with assembled piers under the same mode is slightly smaller than that with cast-in-situ piers, and the maximum difference is only 2.7%, while the natural frequency is reduced by as much as 19% due to the pile-soil effect. Under the action of the actual seismic wave, the maximum displacement of the pier top, the bending moment and shear force of the pier bottom along the bridge direction of the assembled pier continuous beam bridge are close to those of the cast-in-situ pier. However, the pile-soil effect increases the maximum displacement of the pier top along the bridge direction by 9.4%, and decreases the bending moment and shear force of the pier bottom along the bridge direction by 41% and 40.9%, respectively. The results show that the seismic performance of high-speed railway bridge with assembled piers is not significantly reduced compared with that of cast-in-place pier bridge. [ABSTRACT FROM AUTHOR]

Under strong winds, newly transplanted trees can tilt or fall, causing economic losses and injuries. Therefore, studying the wind resistance of trees and methods to enhance their wind resistance is of great significance. In this study, 3D simplified models of spruce were built before and after the installation of support frames in them. The trees were 8 m in height, 4 m in crown diameter, with a trunk diameter of 0.3 m at the base. Corresponding mechanical properties were assigned to the models and fluid-solid interaction was numerically simulated. The results showed that without support, the displacement of the spruce treetop, shear stress on branches, and bending moment at the base increased with increasing wind speed. At a wind speed of 20 m.s-1, the maximum shear stress in the transverse direction of spruce was 2.6 MPa, exceeding 85% of its transverse shear strength. This indicates that there is a possibility of shear failure in the tree with the failure point at the junction of the primary branch and the main stem. Supporting the tree at 1/8, 2/8, and 3/8 of its height reduced the displacement of the treetop, shear stress on branches, and bending moment at the base, ultimately lowering the risk of shear failure and falling. When the support frame was placed at 2/8 of the tree's height, the shear stress on the tree was minimized, reducing the risk of branch breakage by 50%. However, the part of the tree above the support frame had an increased wind-induced oscillation frequency compared to the unsupported tree, reducing the tree's stability and increasing the risk of branch breakage owing to prolonged high-frequency vibration. Numerical simulation of wind-induced tree response is highly customizable, and its results have reference value for studying wind resistance of trees and designing support frames for trees. [ABSTRACT FROM AUTHOR]

Copyright of China Mechanical Engineering is the property of Editorial Board of China Mechanical Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Surface layer is an important part of foundation pit supporting system. For the purpose of designing the surface layer reasonably, this paper established a forced model of the surface layer by using the small deflection bending theory of thin plate, and the forced analysis was carried out on the surface layer of shotcrete foundation pit support type. In order to simplify the calculation, the concrete surface layer is assumed to be an elastic body, and the surface layer is simplified as a rectangular thin plate with four sides simply supported on the foundation pit slope, which derives in the general expressions of the deflection and bending moment of the bottom layer under active earth pressure. And the bending moment and deflection of the bottom layer after the foundation pit excavation are simulated by the finite difference software FLAC3D. The results show that the theoretical values of the deflection and bending moment are in agreement with those of numerical simulation, the margin of error between the calculation value and the simulation value of the maximum deflection and maximum bending moment are 6 % and 13 % respectively, the distribution laws which simulation cloud pictures of the deflection and bending moment show are consistent with those calculated by the formulas. The deflection and bending moment both reduce gradually from the surface center to boundary, which verifies the effectiveness of the proposed method. The formulas can provide reference for the design of surface layer.

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the influence of different forms of defects on the stress of lining structure, through the model test, different forms of defects were simulated, and the changes of bending moment, axial force and safety factor at different parts of lining structure were analyzed. The results showed that the defects at the connection between the side wall and the inverted arch increased the bending moment and axial force at the middle of the lining arch waist and the inverted arch, and decreased the bending moment and axial force at the vault. According to the different forms of defects, the effects on different parts of the lining were different. When there were only concrete shrinkage defects or unconnected steel defects, the main influence parts of lining structure were haunch and side wall. When the two defects coexisted, the middle part of vault and inverted arch would also be greatly affected. The influence of concrete loose defects on the safety factor of lining structure was generally greater than that of unconnected defects of steel bars. The main influence areas were arch waist and side wall. When the two defects coexisted? the safety lector at the middle of arch waist and invert decreased obviously 3 which was 52.03% and 32.40% respectively. The effect of defects on the safety factor at the middle of the hance and inverted arch was greater than that at the vault and side wall. During construction? the quality of concrete pouring here should be strictly controlled to ensure the strength after forming, and the pouring thickness can be appropriately increased to make it have a higher safety reserve. [ABSTRACT FROM AUTHOR]

In order to study the damage mechanism of shield segment structure of shield tunnel with small curvature radius, based on practical engineering cases, a fine lining segment model considering segment joints and inter-ring joints was established to reveal the segment damage mechanism in the construction stage of shield tunnels with small curvature radius. The results showed that the axial force, shear force, positive bending moment and Mises stress of the segment all peaked at the inner and outer arch waists when the shield tunnel with small curvature radius was constructed in the turning section. The arch waist position of segments were more likely to be damaged during the excavation process. When the rectification angle of the jack thrust increased, the overall tunnel deviated to the outside. The outer side of the shield tunnel waist was more obviously affected, since the offset of outer arch waist was significantly larger than that of inner arch waist. The numerical simulation was consistent with the field observation of segment damage, which could provide reference for practical engineering. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Aiming at the lining structure damages caused by surrounding rock hydro-collapse of loess tunnel and considering the characteristics of surrounding rock pressure increasing and surrounding rock constraint softening during the surrounding rock hydro-collapse of loess tunnel, methods for determining the variation values of surrounding rock pressure and subgrade bed coefficient before and after surrounding rock hydro-collapse of loess tunnel are proposed, and then an analysis method based on load-structure model is created for calculating the mechanical response of lining structure in the process of surrounding rock hydro-collapse of loess tunnel. A loess tunnel, on which a field immersion test was conducted before, is selected as the analysis object. The variation law of structure internal force and safe bearing status of the tunnel during the surrounding rock hydro-collapse are calculated and analyzed by using the established load-structure model. The results show that the internal force of the lining structure increases significantly and the internal force distribution form changes due to surrounding rock hydro-collapse. In particular, the bending moment at the center of the inverted arch and the wall foot increases by about 2.5~3 times, and the bearing safety factor of the section can be reduced to less than 1, which should be addressed in the design of lining structure. The calculation results of the model are consistent with the field measurements, which verifies the rationality of the analysis method and can provide some reference for the redundant design of the lining structure of collapsible loess tunnel. [ABSTRACT FROM AUTHOR]

In order to figure out the influence of existing tunnel induced by underlying tunneling, firstly, the soil-free settlement of tunnel centerline caused by underlying tunneling is calculated by Loganathan function. Secondly, the additional loading on the existing tunnel is transferred by soil-free settlement. The existing tunnel is simplified as Euler-Bernoulli beam lying on Kerr foundation model and the tunnel axis force second-order effect is taken into consideration. Then, a deformation analytical solution of the existing tunnel is proposed based on the condition of the freedom of the two tunnel ends. Studies show that, compared with the measurements, the proposed method solutions have more in accord with the measurements. By comparing with degraded solution based on the proposed method, the prediction of proposed method is more superior. Further studies show that both the deformation and bending moment of the tunnel linear increase with the volume loss; with the depth of existing tunnel centerline increasing, tunnel deformation and inner force will be increased; with the diameter of shield tunneling increasing, the deformation and inner force of the existing tunnel increase significantly. Key words: shield tunnel; passing under existing tunnel; Euler-Bernoulli beam; foundation model; axis force influence [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Focusing on aero-engine low-pressure rotor spline couplings, the nonlinear characteristics of bending stiffness and the mechanism were analyzed, a solid finite element model of spline coupling considering gear surface contacts was established, the static stiffness experiments of the spline couplings were carried out. Through simulation and experiments, the nonlinear variation law of the structural stiffness of spline couplings was studied, and then the influence laws of fit clearance, tightening moment and torque on bending stiffness were discussed. The research results show that, due to the different contact states and stress conditions of the positioning surfaces, the bending stiffness variations of the spline couplings were mainly divided into two stages, which had piecewise nonlinear characteristics. The bending stiffness of the spline couplings is sensitive to the fit clearances of the positioning surfaces, and reducing the fit clearances of the positioning surfaces may effectively improve the bending stiffness of the structures; tightening moment has little influence on the bending stiffness, and under low load conditions, torque has an obvious effect on the bending stiffness. [ABSTRACT FROM AUTHOR]

To further improve the transportation level of China's high-speed railway, it is urgent to research on the key technology of speed in for the existing 250 km/h high-speed railway. The track structure directly bears the train load, the adaptability of the track after the train speed increase is an important factor affecting the safe and stable operation of the train. Based on the field investigation, finite element analysis, numerical calculation and other methods, this paper studies the adaptability of ballasted track, ballastless track and designed track superelevation, and the technical conditions for the speed-increase track of 250 km/h high-speed railway are put forward. The main conclusions are as follows: the speed increase of ballasted track lines will cause the increase of dynamic indexes of the fastener and track bed, which will reduce the service performance of structures; the speed increase of ballastless tracks will cause the increase of the longitudinal and transverse bending moments of track slab and concrete base slab, and the longitudinal bending moment of track slab in subgrade section increases the most, which is 4. 7 kN · m/ m; considering the safety margin, the reinforcement of track slab and concrete base slab in the subgrade, bridge and tunnel sections meets the requirements of strength and crack width; after the speed increases, the track design curve superelevation should be adjusted to meet the requirements of minimum curve radius and transition curve length under different speed levels; after the speed increase, attention should be paid to the drainage of track slab structure, track smoothness, etc., and the relevant requirements of the current specifications should be satisfied. [ABSTRACT FROM AUTHOR]

Copyright of Advanced Engineering Science / Gongcheng Kexue Yu Jishu is the property of Advanced Engineering Science Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Relying on the open excavation subway foundation pit project of Aixihu in Nanchang, the excavation of the foundation pit was numerically simulated by ABAQUS software. The reliability and applicability of the numerical model were verified by comparing the numerical calculation and field monitoring results of the horizontal displacement of the diaphragm wall, supported axial force, surface settlement. The bending moment variation law of diaphragm wall during excavation was analyzed. The research showed that there was a significant difference in the bending moment between the earth facing side and the excavation side of the diaphragm wall, the excavation side was tensioned as a whole and the earth facing side was compressed as a whole. The maximum bending moment of the excavation side was 2.3 times than that of the earth facing side. In the original design scheme, the main reinforcement on both sides of the diaphragm wall was symmetrically reinforced, and there was a large optimization space in the design scheme; the effect of crack control was not good only by increasing the amount of reinforcement. Under the condition of constant excavation depth and internal support spacing, after the asymmetric reinforcement optimization of the existing design, the reinforcement amount on the earth facing side and excavation side was reduced by 38.3% and 11.4% respectively, and the load sharing characteristics of the structure were more reasonable, which could greatly reduce the use of reinforcement, so as to reduce the project investment and construction scale. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Hebei University of Science & Technology is the property of Hebei University of Science & Technology, Journal of Hebei University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A lateral loading model box was used to carry out model tests under two cases: the tunnel was located in loess (case 1) and penetrated by potential sliding surface in loess (case 2). The stress characteristics of tunnel lining in the process of slope deformation were studied, and the laws of slope deformation, pressure change of tunnel surrounding rock and lining moment change were analyzed. Results showed that the surrounding rock near the slope side of the tunnel lining was easy to form a void zone under the two cases. The maximum width of the void zone was about 1 cm in case 1 and close to 2 cm in case 2. The void zone in case 2 was much larger than that in case 1, with a relative increase of 100%; Compared with case 1, the peak value of lining bending moment in case 2 increased significantly, with a relative increase of 159.33%, and the maximum increase was located in the area near the side arch foot of the slope. The slide of the potential sliding surface in the slope significantly increased the possibility of tunnel lining damage. [ABSTRACT FROM AUTHOR]

For the problems of the well deflection, hole enlargement, bit whirl and vibration, and the bit early failures caused by the unbalanced forces on PDC bits during the drilling processes, the optimal design model of cutter-layout of global force balanced PDC bits and bending moment model were constructed based on the existing PDC bit cutting mechanics, and the corresponding solution method was proposed. Results of a cutter layout design example show that the global force balance cutter layout design method may keep the global force balanced status of PDC bits in different footages. In particular, the force balance state of PDC bit is greatly improved at small footage(<1 mm). The drilling stably of PDC bits is improved. The results are of great significance to amend the forces on drill bits, which may extend the service life of the drill bits and improve the drilling efficiency. [ABSTRACT FROM AUTHOR]

The in-plane impact dynamics properties of the negative Poisson's ratio effect honeycomb structures with variable arc angle curved concave sides were studied by using numerical method. The effects of the impact velocities and arc angles on the deformation failure mode and the energy absorption capacity of the honeycomb structures with curved concave sides were discussed. The results show that changing the impact velocities and arc angles has effects on the deformation failure mode of the honeycomb structures with curved concave sides. When the impact velocity is high, the stress fluctuation ranges of the honeycomb structures are large and the energy absorption value per unit volume of the structures increases with the increasing of the arc angles. The above phenomenon does not exist when the impact velocity is low.When the arc angle is larger than 120°, the honeycomb structures with curved concave sides have negative Poisson's ratio effect, and the energy absorption capacity of the structures are higher than that with positive Poisson's ratio honeycomb structures corresponding to other arc angles, where the phenomenon is independent of the impact velocity. [ABSTRACT FROM AUTHOR]

The third generation hub beatings were taken as the object of study to deduce the con tact deformations and contact loads among rolling body, inside and outside raceways under the actions of bending moment. A more accurate calculation model of contact load dssttibution was proposed. The circumferential dssttibution laws of contact load and contact angle of hub beatings under different working conditions were analyzed. Based on the first modification of load distribution in hub beatings, the contact fatigue of raceway materials and bearing rollers with different position angles was considered, and the modified L-P model of fatigue life of third generation hub beatings was obtained by using the product laws statistical interpretation. Meanwhile, combined with the ISO281-2007 life co-reaction calculation method, second modification of the lubrication phenomenon were conducted, and the fatigue life model of the third generation wheel hub beatings was obtained, where the lubrication was modified. The bending fatigue tests of the beatings were carried out by rotating bending fatigue testing machine. The tests results show that the errors between the theoretical and testing values calculated by the proposed fatigue life model are less than 10%, and the correctness of the model is verified. [ABSTRACT FROM AUTHOR]

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Comparing to the roof and door, the two ribs of coal mine roadways are relatively weaker and have more deformability. The large deformation of the coal-mass in the ribs have significant effect on the roadway stability. Based on the practical case of severely deformed ribs and by considering its deformability, an analytical model of roof beam with Winkler foundation is built. Hereby the characteristics of bending moment and reflection have been studied. The foundation rigidity of coal mine roadway is revealed and the rib-control support principle is proposed. By employing reinforcement in the ribs, the foundation rigidity of the ribs will increase, and the deformation and failure of the ribs will directly controlled by the reinforcement. The stability of roof and floor is reinforced via the foundation rigidity effect. The foundation rigidity and the rib-control support principle of coal mine roadway are analyzed and validated by means of numerical simulation and field tests. The results show that under the effect of the vertical concentrated stress over ribs, the coal-mass is notably compressed and the roof strata bend and sag along with it. The foundation rigidity has great effect on roof deformation which makes it the key influencing factor. Under the conditions of identical roof support, the reinforcement in the ribs will not only reduce the convergence and failure extent of the ribs during roadway development and retreat mining, but also effective control the deformation and failure of the roof and the floor, which makes it an effective method to improve the roadway stability. This study has improved the understanding of the importance of rib support in roadway ground control, and revealed the support mechanism of rib-control. [ABSTRACT FROM AUTHOR]

In view of the asymmetrical deformation failure in the mining roadway at a steeply inclined special thick coal seam, some field observations, mechanical modeling calculations and numerical simulation analysis were used to reveal the asymmetrical deformation failure mechanism after the excavation of the roadway in steeply inclined coal seams. The stress field after the excavation of the roadway and the distribution characteristics of the plastic zone were analyzed. A new support and reinforcement scheme for the retractable U-shaped steel and asymmetric prestressed anchor(cable)support was proposed. The study shows that:(1) the asymmetrical failure of the roadway is characterized by the subsidence, slippage, and internal expansion along the bedding of the hard rock strata along the side of the coal body; the subsidence of the top of the side of the hard rock is greater than that of the coal side and the central axis of the roadway inclines to the coal side. (2) The asymmetric deformation mechanism of the roadway is that, under the effect of nonuniform load, the angle and size of the counterforce of the shoulder angle support on both sides of the roadway arechanged. The reaction force of the hard rock lateral support is greater than that of the coal side. Also the inclination angle of the coal side is larger than the side of the hard rock. The side rock of the hard rock layer slides, sinks, and expands along the bedding under the action of small angle and large stress, and the side of the coal body is pushed out of the drum under the action of nearly vertical angle force. (3) The bending moment of the roadway from the side of the hard rock to the side of the coal body is increasing all the time. The shear force appears to increase first, then decrease and then increase, and the direction changes in the second increase. The position of the direction change is the offset position of the roadway axis inclining to the side of the coal body. The axial force appears as a parabola,decreasing first and then increasing. The optimum and reasonable section of the roadway under non-uniform load acts is the"asymmetric three-hinged arches". (4) The retractable U-shaped steel and asymmetric prestressed anchor(rope) support are proposed, focusing on reinforcing the lateral support of the roadway coal body and the top support on the side of the hard rock. [ABSTRACT FROM AUTHOR]