Table of Content

30 July 2015, Volume 49 Issue 07 Previous Issue    Next Issue

Architechural Science

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Analysis of LongTerm Deformation of Railway Embankment at Repeated Train Load in Permafrost Regions WU Zhijian1,2,3,CHEN Tuo4，MA Wei5 2015, 49 (07):  929-934.  Abstract ( 759 )   Save Abstract： Based on strong motion tests on typical embankment at Beilu River segment along the QinghaiTibet Railroad, the acceleration history waveforms near railway tracks were collected when the train was passing, and the dynamic train load was converted into equivalent creep stress by using the equivalent static force method. Moreover, the creep equation of frozen soil was introduced according to the result of frozen soil rheological triaxial tests. The longterm deformation of the embankment at the train load was obtained, and the ratio of permanent deformation at the train load to the whole embankment deformation was quantized as well. The research results show that the vibration effect of repeated train load on deformation accounted for approximately 10% of the total accumulative settlement of the embankment. The creep strain values at the slope toes are significant and extended upwards gradually, which increases with the development of time and the strain rate decreases instead. References | Related Articles | Metrics

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Laboratory Model Test Study of Pullout Mechanism of Tunnel Anchorage TANG Hua,XIONG Xiaorong,WU Zhenjun,YUAN Conghua,Deng Qin 2015, 49 (07):  935-939.  Abstract ( 762 )   Save Abstract： A laboratory model test of tunnel anchorage was conducted to investigate its pullout mechanism and bearing capacity. First, a laboratory model test device was designed and produced. Second, through the strength and deformation test, the material ratio was determined to simulate tunnel rock. Third, the surface and rock deformation, strain and stress were measured during the entire test process. The results show that, under pulling loads, tensile failure first occurs in top surface rock near the anchorage, then shear failure occurs in the rock around the anchorage. The failure surface is inverted cone from the anchorage bottom. The bearing capacity of the tunnel anchorage consists of two parts. The first part is the ultimate friction resistance in the interface of anchorage and rock while the second part is the rock sheartensile resistancenamely clamping effect. Under 50 times design cable force, the tunnel rock is in elastic stage, suggesting that the current tunnel anchorage design is quite conservative and can be further optimized. References | Related Articles | Metrics

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Deformation and Instability Characteristics of Loess Slope Based on Shaking Table Model Test WU Zhijian1,2,3，LEI Tian1,2，CHEN Yujin1,2，WANG Ping1,2,3，CHAI Shaofeng1,2,3 2015, 49 (07):  940-945.  Abstract ( 752 )   Save Abstract： Based on the shaking table test of 1∶25 pure loess model with low water content and low angle,  the deformation and instability process of the loess slope under the earthquake were studied, the response characteristic of acceleration and stress was obtained, and the instability mechanism of typical loess slope under strong earthquake was discussed. The results show that the input of seismic wave has a surface and vertical amplification effect on the loess slopes. The top of the typical loess slope appear to have a series of tensile cracks when it suffers from a seismic intensity as high as VIII degree, with the increase of the intensity of the earthquake, the tensile cracks of the top develop from front to back gradually and form a series of permanent tensile failure. The top of the slope appears to have a significant seismic subsidence and presents the typical characteristics of seismic subsidence landslide when the loess slope suffers from a seismic intensity of as high as IX degree. References | Related Articles | Metrics

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Application of FVM with Collocated Grid in Flow Field Calculation of Variable Density Grout LI Xiaolong，WANG Fuming，ZHONG Yanhui，ZHANG Bei，GUO Chengchao 2015, 49 (07):  946-950.  Abstract ( 695 )   Save Abstract： To study the diffusion mechanism of expansible grouting material, a calculation method for solving two-dimensional flow field of variable density grout was developed based on the modern computational fluid dynamics theory. The structured collocated grid was used for partitioning the computational domain. The finite volume method (FVM) was employed to discretize the governing equations of grout. The momentum interpolation method (MIM) was adopted to establish the pressure correction equation. The semi-implicit method for pressure-linked equations (SIMPLE) was utilized for iteratively solving discrete momentum equations, pressure correction equations and velocity correction equations. By using it to solve an example of variable density grout freely expanding in a two-dimensional rectangular slot, the validity and high calculation accuracy of the proposed method was verified, laying a foundation for developing the numerical method for simulating the flow and diffusion process of expansible polymer grouting material in two-dimensional fractures. References | Related Articles | Metrics

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Shaking Table Test on Earthquake Response of Discontinuous Medium High and Steep Rock Slope WANG Bin,CHE Ailan,GE Xiurun 2015, 49 (07):  951-956.  Abstract ( 845 )   Save Abstract： Seismic response of rock slope with discontinuous is mainly affected by its geometrical and mechanical properties. Due to its reverse or bedding joints, high and steep rock slope is at high risk of collapse and damage. To solve this problem, the dynamic response and failure mechanism were studied using a largescale shaking table test. The rock material was prepared with cement, sand, iron powder, clay and mixture. The discontinuous joint was imitated using Teflon fabric with low skin-friction coefficient. The experimental results indicate that there are three steps during the failure, that is, development of cracks, spalling of the slope, collapse and sliding. The main slide surface appears at the height of 2/3 of the slope, along the Teflon fabric. The internal acceleration of the slope shows an obvious amplification effect along the slope surface, and horizontal acceleration is more effective. Besides, as the earthquake intensity increase, the acceleration amplification increases near the tip of the slope. References | Related Articles | Metrics

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Analysis of Dynamic Response of Embankment Reinforced with Geogrid with Strengthening Nodes Based on PFC2D QIU Chengchun1,ZHANG Mengxi2,WANG Yiming3 2015, 49 (07):  957-960.  Abstract ( 651 )   Save Abstract： The embankments were simulated by the software of particle flow code based on the discrete element theory. Different dynamic responses were investigated in the cases of unreinforced embankment, embankment reinforced with traditional geogrid and embankment reinforced with geogrid with strengthening nodes. The displacement fields and the distribution of contact forces of soil particles in three cases were analyzed. Compared to the embankment reinforced with traditional geogrid, due to the existence of the strengthening nodes, the geogrid with strengthening nodes can effectively reduce the accumulated settlement of the embankment and restrict the lateral displacement of the slope. In the case of reinforced embankment, multiple vertical forcebearing columns develop below the loading platen, resulting in uniformly distributed forces within the embankment. References | Related Articles | Metrics

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Deformation Law and Failure Mechanism of Anchorage-Surrounding Rock System of Puli Extra-large Bridge TANG Hua,XIONG Xiaorong,DENG Qin,YUAN Conghua,WU Zhenjun 2015, 49 (07):  961-967.  Abstract ( 695 )   Save Abstract： The deformation law and failure mechanism of anchorage-surrounding rock system were studied by the 3D elasto-plastic numerical simulation using the finite difference method (FDM). The development of plastic zone, displacement and stress were analyzed with the increasing load. It is shown that at the designed cable force, the displacement of the system is maintained in millimeters. The hump of displacement between the anchorage and surrounding rock become clear under the increasing load. At the limit state, according to the displacement vector graph, the failure area of rock can be sketched, in which the upperlower destruction of surrounding rock are respectively 1.1 times and 0.5 times of the width of the back face of anchorage. The system has enough safety stability under the designed cable force. At aloading of 8 times of the cable force, the hoop and radial plastic zones achieve breakthrough. At the ultimate state, the plastic zones appear to be at an antiplug state. According to the displacement of the monitoring point, the plastic zones of surrounding rock and stress extension, the tensileshear complex failure caused by anchorage in surrounding rock may be in a failure mode. Key words： References | Related Articles | Metrics

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Effects of Heights and Height Differences of Piers on Dynamic Characteristics and Seismic Response of Parallel Bridges CHEN Bingyao1，WU Yongchang2 2015, 49 (07):  968-972.  Abstract ( 646 )   Save Abstract： Unequalhigh parallel bridges are different from those of conventional symmetric structures. The correlation between heights and height differences of piers to dynamic characteristics and seismic response was provided. Using a project as the background, the effects on dynamic characteristics and seismic response was studied by modifying height and height difference. The results show that the frequency is negatively correlated with heights and height differences of piers. Seismic response, which is not affected by height differences, increases with heights. Key words： References | Related Articles | Metrics

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Face Stability Analysis of Tunnels with Consideration of the Influence of Excess Pore Pressures HOU Yongmao 2015, 49 (07):  973-976.  Abstract ( 641 )   Save Abstract： During the earth pressure balance (EPB) shield tunneling, face stability is very important for controlling the impact on the environment. Field measurement was used to study the development and distribution of the excess pore pressure and earth pressure increment. Based on the monitored data, the fluidsolid coupling numerical model was used to analyze the face stability of tunnels with consideration of the influence of excess pore pressures in loading and unloading conditions. Subsequently, parametric analysis was executed to study the influence of the soil permeability coefficient and shield stopping time on face stability. References | Related Articles | Metrics

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Detection and Cause Analysis of Internal Cracks for Large Scale 2-Directional Pre-Stressed Concrete Walls FENG Shaokong1,HUANG Tao2,LI Haifeng2 2015, 49 (07):  977-982.  Abstract ( 665 )   Save Abstract： Splitting cracks were found in the two-directional pre-stressed concrete walls of a large scale diversion project in north China. Based on internal structural characteristics of the wall, the impact imaging method (IIM) was applied for the detections of cracks distribution, seriousness and damage area ratio of the internal cracks and the damage cause analysis. The core test and numerical simulation by 3D FEM with prefabricated joints element were also adopted for verifications. The 56 drilled cores show that the IIM has high accuracy and resolutions on the internal crack distributions. This result provides reliable data for decisionsmaking of the wall repair strategies. Both field test results and numerical analysis show that the frost of the water inside the corrugated pipes that contain the prestressed tendon lead to the internal splitting cracks, due to the incompact grouting into the pipes. This accident shows the significance of the grouting quality control of the corrugated pipes inside the posttensioned structures in cold regions in northern China. Key words： References | Related Articles | Metrics

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Factors Influencing the Behavior of Single Geocell-Reinforced Sand ZHOU Yamei,ZHANG Mengxi,WU Yue 2015, 49 (07):  983-987.  Abstract ( 741 )   Save Abstract： To better understand the bearing capacity and deformation characteristics under circular load, a series of compression tests with the same space were conducted on single geocell-reinforced sand samples of three different shapes(circular, rectangular, and hexagonal crosssections) and three different constraint conditions (under flexible confining, rigid confining and unconfined condition). The effects of these variables were investigated according to the pressuresettlement curves. FLAC3D(Three Dimensional Fast Lagrangian Analysis of Continua) was introduced to simulate the compression tests. The nephograms of single geocell-reinforced sand in different conditions were compared. The results show that the geocell can improve the strength of soil. Circular cells have the best effect on reinforced sand of the cells of all shapes. Confining can constrain the deformation of soil and reduce the horizontal displacement of single geocellreinforced sand. With the modulus of confined material increasing, the stiffness of the geocell-reinforced sand increases. References | Related Articles | Metrics

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Application of Ultrasonic Testing Method to Detecting Concrete Structures of Jetty Surface WANG Yingyi1a,ZUO Zibo2,YU Kai2,HUAN GXingchun1,2 2015, 49 (07):  988-992.  Abstract ( 684 )   Save Abstract： Based on the theory of ultrasonic nondestructive testing, a prediction method for the strength of concrete structures using ultrasonic testing was established. The predicted strength of concrete with 4 200 measuring points using ultrasonic testing and measured strength of concrete with 400 samples using field drilling for core tests were compared based on the background of Wusong Jetty. The results show that both of the predicted and measured strength are approximate normal distribution. The probability peak intervals of the two methods are 12 to 16 MPa and 9 to 15 MPa, the distribution density are 28% and 23.26%, the range of strength distribution are 3 to 25 MPa and both are smaller than the design value. These results show an overall good performance by the prediction method. Key words： References | Related Articles | Metrics

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Dynamic Stability of Deep Water Foundation of Extra-Large Bridge Under Multiple Disasters CHEN Feng1,CHE Ailan1,FU Baiyong2,LIU Gao2 2015, 49 (07):  993-997.  Abstract ( 658 )   Save Abstract： Taking the deep water foundation of Qiongzhou Strait Bridge as the research object, and aimed at the issue of dynamic stability of deep water foundation of extra large bridge, the disastrous factors such as seismic load, ship impact load and wave forces were considered. Based on the dynamic FEM, the characteristics of dynamic response of the deep water foundation, the displacement response under the actions of multiple disasters were explored and analyzed. The caisson of the foundation represents without any phase difference basically under seismic force, and maximum displacement reaches 24.4 cm. The horizontal displacement reaches 15.1 cm under ship impact force, and 10.8 cm under wave force. The pile group shows complex response under dynamic load. Due to the constraints of soil and function of inertial force of the caisson, the relative displacement between the pile body and caisson is large, which leads to obvious stress concentration at pile head. The results can provide references for the design and construction of deep water foundation, especially for Qiongzhou Strait Bridge. References | Related Articles | Metrics

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Influence of Construction Procedures on Adjacent Energy Supply Pipeline due to Large Foundation Pit Excavation DU Jialun1，4,ZUO Zibo2,RONG Jian3,HUANG Xingchun1, 2 2015, 49 (07):  998-1004.  Abstract ( 679 )   Save Abstract： In this paper, numerical simulation analyses were performed to investigate the influence of construction procedures on foundation pit itself and the surrounding environment based on the background of A1 foundation pit of Shanghai Hongyuan Prime International Cultural City. The results show that when the excavation is completed, the final values of the amount of excavation pit bottom, vertical displacement of lattice and erect columns, stress of supporting system, lateral displacement of diaphragm wall and vertical displacement of adjacent energy supply pipeline for the Scheme One (mainly using island excavation) and Scheme Two (mainly using basin excavation) under the same conditions for the excavation and supporting are similar, but the latter is slightly smaller. In Scheme Two, the degree of the value dramatic changes for the impact of large foundation pit excavation on the foundation pit itself and the surrounding environment during each working condition is gentler than the value changes in Scheme One, therefore, Scheme Two is safer. References | Related Articles | Metrics

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Deformation Measurement and Numerical Stimulation of Large-Scale Underground Cavern XU Zhe1a,WANG Yingyi1b,LI Ke2,HUANG Xingchun1 2015, 49 (07):  1005-1009.  Abstract ( 713 )   Save Abstract： Taking a large-scale underground cavern of hydropower station for example, a 3D numerical model was established to obtain the deformation characteristics of the surrounding rock mass after excavation of the cavern, and the influence of prestress loss of the anchor rope on the surrounding rock mass deformation and stress state was analyzed. The rationality of the simulation method and the feasibility of the support measures was analyzed by comparing the simulation results with the measured results. The results show that the max horizontal displacement occurs at the middle of the sidewall, while the max vertical displacement occurs in the top of the arch, and in the intersect area of the cavern the deformation is significant. The simulation results are very close to the measured results which can show the actual excavation process and the deformation characteristics of the surrounding rock mass. The horizontal displacement  significantly increases when the prestress loss in anchor rope comes to a certain degree. Key words： References | Related Articles | Metrics

Communication and Transportation

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Elastic-Wave-Based Detection Method for Under Line Structure of High-Speed Railway YANG Hongkai,CHE Ailan,TANG Zheng,FENG Shaokong 2015, 49 (07):  1010-1016.  Abstract ( 632 )   Save Abstract： Based on the analysis and research of the structure and defects, the high-speed railway underline structure was simplified into a two-dimensional multi-medium structure, and a two-dimensional defect model of the underline structure was established. By using the dynamic finite element method, the elastic wave propagation characteristics, especially waveform and predominant spectrum were deduced. The qualitative relationship between the variation of elastic wave propagation characteristics and different defects was established. Aimed at the two common types of defects, a 1∶1 full scale model of highspeed railway with defects was established. The data collection method, analysis method, and result visualization method were proposed to evaluate the space distribution of preinstall defect. Key words： References | Related Articles | Metrics

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Detection Methods and Research About Full-wavefield Imaging Detection Method on High-Speed Railway Under-Track Structure TANG Zheng1,CHE Ailan1,FENG Shaokong1,SHI Youzhi2,FAN Yanmin1 2015, 49 (07):  1017-1022.  Abstract ( 113 )   Save Abstract： A full-wavefield imaging detection system integrates the point-source/point-receiver scheme with the multi-directional imaging technique. It is equipped with an impacting hammer, a series of three-component velocity transducers and a signal capturing unit. To evaluate the feasibility of this system for detecting defect of high speed railway under-track structure, a full-scaled highway embankment model test with pre-setting defection was conducted and a 3-D numerical simulation using FEM was performed for comparison and mechanism study. The results are in agreement with the numerical ones on the processed scanning images. It is concluded that the full-wavefield imaging detection method exhibits high potential in inspecting the defects of high speed railway under-track structure by imaging. References | Related Articles | Metrics

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Construction Mechanics of Tunnel with Super-Large Cross-Section and Its Dynamic Stability 2015, 49 (07):  1023-1029.  Abstract ( 85 )   Save Abstract： The force of closely-spaced tunnel with super-large cross-section changes a lot because the flat rate becomes smaller. Aimed at the problem of displacement deformation characteristics and the pressure distribution of the surrounding rock in closely-spaced tunnel supporting design with super-large cross-section, and baseid on the two-hole eight-lane highway tunnel in Niu Zhai Hill, this paper established a three-dimensional finite element model considering the actual terrain and geology. It conducted a numerical simulation analysis of the  construction mechanical form of the tunnel under excavation, obtained the law of tunnel surrounding rock deformation during tunnel cons, and investigated the influencing law of proximity construction for closelyspaced large-section tunnel. The results show that the construction mechanical properties of closely-spaced large-section tunnel are complex. Due to the influence of bias pressure, the overall horizontal displacement of the surrounding rock is unsymmetrical distributed; the maximum horizontal displacement occurs in the spandrel of southline tunnel, the maximum subsidence of tunnel vault occurs in first hole, and the bulge at the tunnel invert is large. The stress concentrates in the invert and arch foot of the two holes. Based on these findings and considering the earthquake damage of tunnel entrance easily caused by bias pressure and ultrashallow cover, this paper performed dynamic finite element calculation after tunneling, analyzed the dynamic response under earthquake force of portal section, and evaluated its dynamic stability. The results provide basis for the optimal design, tunnel construction guidance and evaluation of tunnel stability and safety of supporting structure. References | Related Articles | Metrics

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Influence of Metro Train Loading Calculation Methods on Dynamic Responses of Shield Tunnel LI Lei1,2,ZHANG Mengxi1,WU Huiming2 2015, 49 (07):  1030-1034.  Abstract ( 123 )   Save Abstract： Moving axle loads, excitation force function and deterministic formulas for vibration acceleration of track were employed to calculate the metro train load timehistory in Shanghai. Considering the interface characteristics between the segments and the surrounding soils as well as other segments and the effect of longitudinal joint bolts, a threedimensional dynamic finite element model of track bedsegmentsoil system was constructed to compare the dynamic responses on shield tunnel structures. The results show that dynamic stresses timehistory curves of track bed and soil elements are basically the same for the three methods. Due to the differences of acceleration frequency spectrum caused by moving axle loads and excitation force function methods, the evaluation of metroinduced environmental vibrations should be based on the measured data of metro train loading. References | Related Articles | Metrics

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Loose Media Slope Stability Evaluation Based on Fuzzy Analysis ZHANG Shilun1,ZHANG Mengxi1,JI Suiwang2,CHEN Qiang2,LUO Kangjun2 2015, 49 (07):  1035-1039.  Abstract ( 83 )   Save Abstract： The loose media slope stability evaluation based on fuzzy analysis was proposed aimed at the difficulties in using the conventional methods to get its stability evaluation, because of the complex internal structure and affecting factors of the mountainous highway loose media slope. The loose media slope stability fuzzy AHP comprehensive evaluation was conducted based on J1 segment engineering examples of YaKang highway. The result shows that the method proposed is simple, reliable, and a scientific, which can provide a new reference for the engineering application. References | Related Articles | Metrics

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Model Test on Approaching Construction of Multi-line Overlapped Shield Tunnelling ZHANG Xiaoqing1，ZHANG Mengxi1，WU Yingming2,LI Lei1，WANG Youcheng1 2015, 49 (07):  1040-1045.  Abstract ( 66 )   Save Abstract： With the unceasing development of the metro construction, multi-line overlapped shield tunnels in soft soil are being built as a complex spatial distribution. For two kinds of typical construction methods of upcrossing and under-crossing, model test research was applied to analysis the dynamic construction process. According to the shield tunneling technology characteristics and control requirements of approaching construction, the drainage method was applied to selective analysis of the surface subsidence and the existing tunnel longitudinal deformation caused by formation damage and excavation unloading of multiline overlapped tunnel at various stages. The research results can provide some theoretical basis and prophase guidance for similar projects in the future. References | Related Articles | Metrics

Architechural Science

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Distributed Running State Monitoring and Pre-Warning of Common Span Railway Bridges ZHAO Weigang1，WANG Xinmin1，DU Yanliang1，LI Yundong2 2015, 49 (07):  1046-1051.  Abstract ( 100 )   Save Abstract： This paper proposed and developed an efficient and reliable distributed wireless intelligent bridge monitoring system for the monitoring of commonspan and wild distribution bridges. This system is consisted of a sensor, an acquisition node, a gathering controller and a central sever. It presented a new realtime earlywarning method and the parameters based on both the monitoring data and existing test specification for railway bridge to realize a graded early warning of bridge running state.The proposed monitoring and prewarning system is verified in the realtime monitoring of Daqin Railway bridge. References | Related Articles | Metrics

Communication and Transportation

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Common Cause Failure Analysis of Automatic Train Control System FANG Yungen,ZENG Xiaoqing,WANG Gang 2015, 49 (07):  1052-1057.  Abstract ( 98 )   Save Abstract： Common cause failures(CCF) is not easy to be identified and evaluated in automatic train control(ATC) system design and development. The analysis of the failure characteristics of ATC system failures, system modelling and calculation demonstrated that CCF had a significant impact on the safety of the system. A CCF vulnerability factor was designed according to the system safety theory and the characteristics of the ATC system. Then, the process for CCF identification and screening was discussed. Based on the 2 out of 3 ATC safety architecture, the system failure probability which takes account of CCF was computed. It is found out that it is difficult to quantitatively calculate the CCF due to the lack of historical CCF data. Finally, the general CCF control measures was discussed and summarized. References | Related Articles | Metrics

Mathematical sciences and chemical

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Application of the Inertial Entropy Theory in Analysis of Transversely Isotropic Thermoelastic Cylindrical Shell WANG Wei,ZHAO Shexu 2015, 49 (07):  1058-1061.  Abstract ( 78 )   Save Abstract： The inertial entropy theory was used to analyze the thermoelastic coupling free vibration problem of a simply supported homogeneous transversely isotropic thermoelastic cylindrical shell. By introducing the displacement potential functions, the equations for free vibration problems could be reduced to four secondorder ordinary differential equations and modified Bessel function solutions with complex arguments could be obtained that can describe the displacement, temperature and stress. Considering the tractionfree and thermally insulated conditions at the lower and upper surfaces of the shell, the free vibration equation could be obtained. The crystal of Zinc was chosen as the material. The numerical calculations show that the thickness of the shell has a greater impact on the lowest frequency with the increase of mean radiustolength ratio and the axial halffull wave number. The circumferential full wave number has a greater impact on the lowest frequency of thinnerwall shell. The lowest frequency decreases first and then increases with the ascent of the the circumferential full wave number. The increase of circumferential full wave number enlarges the influence of the thickness of the shell. The inertial entropy theory can get the exact solution with fewer parameters. References | Related Articles | Metrics

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Scattering of Elastic Wave by Two Ideal Fluid-Saturated Inclusions in Double-Porosity Medium DONG Dongxia,SU Jun,ZHAO Shexu 2015, 49 (07):  1062-1066.  Abstract ( 125 )   Save Abstract： Using the Helmholtz resolution method, the solidmatrix, matrix pore and fracture pore coupling equations were decoupled. A series of elastic waves equations were obtained by using the wave function expansion method. Then, with the help of the transformation theory for spherical coordinates and the superposition principle, the scattering problem of double spherical inclusions were expressed in the same coordinate system. Finally, examples of calculation and analysis of different parameters were concerned to determine their impacts on first order wave amplitude with variation to frequency. The results show that different inclusions distance and inclusion radius have significant impact on P1 to P3 wave and Swave amplitude. The value of P1 to P3 wave and Swave amplitude decrease as the distance between the inclusions increases. This impact is more significant at higher frequency. Besides, the value of P1 to P3 wave and Swave amplitude increase as the radius of the other inclusion increases. The radius has more impact on P1 and P3 wave but has a rather small influence on P2 wave and S wave amplitude. References | Related Articles | Metrics

Communication and Transportation

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Face Failure Mechanism for Slurry ShieldDriven Tunnel in layered Ground Condition — Coupling Macroscopic and Microscopic Aspect HU Xinyu1,LIU Anyang1 2015, 49 (07):  1067-1074.  Abstract ( 90 )   Save Abstract： The face stability mechanism for slurry shield under the layered ground condition is of great significance. During the process of the shield tunnelling, the original structure and the strength of the soil around the face will be changed due to the slurry gradual infiltration into the excavation face. Thus, in order to connect and quantify the relationship between the mechanical property and the microscopic structure, the triaxial experimental tests coupled with the numerical simulation method for evaluating the tunnellinginduced ground movement were introduced, Then, based on the actual geometry of the failure mechanism in clay, a modified wedge model with its corresponding analytical solution for the critical face support pressure was presented. For the layered ground condition, it is recommended that the slurry support pressure should be controlled to a relatively low level due to the softening characteristic of clay soil, and it is the pressure produced by the shield cutter bits and transferred to the excavation face contributes to face stabilization. The geometry of the failure mechanism in this ground condition resembles the case in sand: it exhibits a chimneylike failure mechanism, can be better described by the wedge stability models, and the maximum displacement of the ground just occurs on top of the tunnel face.   References | Related Articles | Metrics