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2018 Vol. 35, No. 1
Published: 2018-02-15
Geology and Subgrade
Railway and Rail
Bridge Engineering
Tunnel Engineering
Engineering Economy and Management
 
       Geology and Subgrade
1 Numerical Simulation Study of the Ultimate Resistance of Micropiles in Earth Slope Stabilization Hot!
SUN Shu-wei1, ZHU Ben-zhen2
Abstract：Research purposes： Micropiles are defined as small-diameter (typically less than 300 mm). Due to the small resistance of a micropile, micropiles are always designed as a group in earth slope stabilization. Micropiles-slope system is a complex three-dimensional space system and the mechanism of loading is very complex, and there is lack of scientific method to analyze the ultimate resistance of micropiles in slope stabilization. In this paper, the ultimate resistance of micropiles in earth slope stabilization was studied systematically, and influential parameters were also analyzed. Research conclusions： (1) The ultimate resistance of micropiles increases significantly as the pile spacing in row decreases, however, the reinforcing efficiency of a micropile in the group will decrease. This means that, for economical design, the special attention should be paid on the reinforcing efficient of a micropile under the premise of ensuring the ultimate resistance of group piles. (2) The ultimate resistance of micropiles is not sensitive with the pile spacing in line. (3) The total resistance of reinforcement system increases with the increase of anchorage length, and micropiles deformation transforms from rigid-body rotation to substantial flexural distortion due to the increase of anchorage length. For earth slope stabilization, the optimal anchorage length is about 2 times of the length above sliding surface. (4) The research results provide theoretical guidance for the design and safety evaluation of micropiles in earth slope stabilization.
2018 Vol. 35 (1): 1-5 [Abstract] ( 25520 ) HTML (1 KB)  PDF  (930 KB)  ( 25491 )
6 Statistical Analysis and Proposal on Pile Negative Friction in Collapsible Loess Areas
YE Chao-liang, LIANG Kai-fang, WANG Xiang-yang
Abstract：Research purposes： Giving reasonable value of pile negative friction and the depth of the neutral point is a difficult problem which researchers and designers concern most when designing pile foundations in collapsible loess areas. On the basis of analysis of the influence factor of the pile negative friction and the neutral point depth in collapsible loess areas, this paper collects more than 30 research findings of domestic field immersion test to make summary and statistical analysis of the pile negative friction and the neutral point depth in collapsible loess areas.  Research conclusions： (1) By making statistical analysis of massive measured data, it makes clear the upper and lower limit of pile negative friction and the neutral point depth. (2) When pile top elevations are lower than -5 m, the collapsible soil depth of the soil surrounding the pile is less than 6 m and the collapsible class is lower than Ⅱ, the soil surrounding the pile does not apply negative friction to piles. (3) In practical engineering, there is always large load applied on the pile top and collapsible probability and level is far less adequate than field injection, which all make the depth of the neutral point move up in practice and this paper suggests that taking value of the neutral point depth in 0.5～0.7. (4) By making statistical analysis of massive measured data, it suggests that taking negative friction value in 15～35 kPa is factual when design piles in deep collapsible loess areas and there should be more in-situ tests of pile foundation negative friction characters in loess areas. By combing research achievements, this paper can provide the basis for the pile foundation design in the deep collapsible loess area. 
2018 Vol. 35 (1): 6-10 [Abstract] ( 11141 ) HTML (1 KB)  PDF  (477 KB)  ( 3177 )
11 Study of Soil Deformation Caused by Construction with PBA Method
HUANG Sheng-gen1, FU Zhuo1, WU Jun-lin2
Abstract：Research purposes： As a new method of metro station construction, the pile-beam-arch(PBA) tunneling method is developing rapidly. Neglecting the interaction between underground structure and soil, existing research results mainly focus on surface settlement and pipeline deformation. In particular, there is a lack of research on soil deformation caused by the construction of holes and piles in the four-hole and three-span structure. Based on the Suzhou Street Station of Beijing Metro line 16, the law of surface subsidence in the phase of pilot tunnel excavation was studied through the date of field monitoring. Metro station construction was dynamically simulated with FEM to study soil deformation during the construction in the four-hole and three-span structure.  Research conclusions： (1) "Effect of group cavities" will appear when a plurality of adjacent pilot tunnels are excavated together. (2) Pilot tunnel excavation, construction of first and second lining have the greatest impact on surface subsidence. The proportions of settlement are 32%, 55% and 7%. (3) Supporting system formed after finishing secondary lining construction. In addition to the bottom soil that has vertical upheaval due to unloading after excavation, the other soil mainly was mainly horizontal deformation. After station construction, certain horizontal displacement that moves to the center of station raised in the soil over the vault. Horizontal displacement, caused by stretching deformation of the supporting structure, toward the outside station obvious took place in the soil on both sides of the vault and the soil around the pile end moved to metro station. (4) The conclusion can provide a theoretical basis for the popularization and application of the pile-beam-arch(PBA) tunneling method and provide a reference for similar  projects in the construction and design. 
2018 Vol. 35 (1): 11-16 [Abstract] ( 11057 ) HTML (1 KB)  PDF  (1062 KB)  ( 3106 )
17 Experimental Research on the Stability of Embankment-bridge Transition Section of High-speed Railway in Seasonal Frozen Regions Hot!
SHEN Yu-peng1, DA Zhi-hua1, YUE Zu-run2, TIAN Ya-hu1
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Abstract：Research purposes： For the high-speed railway lines with more embankment-bridge transition section, the control of the deformation difference between the road and bridge transition section is an important factor to ensure the smooth operation of the train, especially in deep seasonal frozen regions. In this paper, a transitional section of Harbin-Qiqihar Railway is used as a pilot monitoring section, based on the field test data of ground temperature change, frost deformation and settlement deformation, the ground temperature change, frost deformation of subgrade surface and settlement  of subgrade basement of embankment-bridge transition section of high speed railway in cold regions are analyzed, the ground temperature and deformation characteristics are revealed, thus the stability of embankment-bridge transition section can be evaluated.  Research conclusions： (1) At the initial stage of construction, graded crushed stone is easier to be endothermic and exothermic compared to coarse grained soil as for backfill materials of bridge back; the temperature difference in corresponding depth of these two kinds of fillers decreases gradually and tends to 0℃, and finally the new thermodynamic equilibrium is formed. (2) During the freezing process, the maximum deformation of embankment-bridge transition section is 4.6 mm, meeting the requirements of specification. (3) Graded crushed stone being adopted as backfill materials of bridge back, the change process of frost heave deformation of subgrade surface layer with the temporal and spatial can be divided into four stages: the rapid development period of frost heave, frost heave relatively stable period, frost uplifting stage and thaw felling period. (4) The relationship between frozen depth and frost heave deformation of surface layer of embankment-bridge transition section is nonlinear when graded crushed stone is applied. But, the maximum frozen depth of embankment influences the maximum cumulative frost heaving value of the subgrade surface. (5) The settlement of the southern slope is greater than the northern slope. The closer to the northern slope-toe, the settlement and deformation amplitude of substrate becomes smaller. During the period between completion of subgrade construction and track laying, the settlement of basement increases slowly. Currently, the settlement deformation amount of each measuring points of the basement meets the standard requirements. (6) The research results can further provide reference for engineering design, construction and maintenance in the future.
2018 Vol. 35 (1): 17-22 [Abstract] ( 16477 ) HTML (1 KB)  PDF  (884 KB)  ( 3377 )
23 Optimization Analysis of Short Sleeper Embedded Track Subgrade of Modern Tram
FENG Qing-song1，SUN Kui1，LUO Xin-wei2，LIU Qing-jie1，LUO Kun1
Abstract：Research purposes： In order to study the influence of the key influence parameters on the stress and deformation of track subgrade structure under the train load and get the optimal parameters combination of the track subgrade, the finite element analysis model of short sleeper embedded track subgrade of tram is established, five factors to the track subgrade mechanical properties are studied with orthogonal test method, which are fastener stiffness, track plate thickness, thickness of the support layer, the total thickness of subgrade and subgrade compaction index K30. In order to make up for the deficiency of quantitative analysis of orthogonal experiment, the weight coefficient of each evaluation index is determined by analytic hierarchy process (AHP). Finally, the optimal parameters combination of short sleeper embedded track subgrade structure is determined.  Research conclusions： (1) The stiffness of the fastener has the greatest influence on the rail displacement, and the thickness of the track slab has the greatest influence on the longitudinal bending moment of the track slab and the dynamic stress at the top of the subgrade, and the subgrade compaction index K30 has the greatest influence on the deformation of the top of the subgrade. (2)The weight coefficients of rail displacement, track slab bending moment, subgrade top displacement and dynamic stress are 0.085, 0.583, 0.043 and 0.289, respectively. (3)The optimal  design scheme of track subgrade is fastener stiffness 40 kN / mm, the thickness of track plate of 0.24 m, the support layer thickness of 0.27 m, the total thickness of subgrade of 1.1 m, subgrade compaction index(K30) of 110 MPa/m. (4)Comprehensive use of orthogonal experiment and analytic hierarchy process can transform qualitative problems into quantitative problems, so that the analysis results are more scientific and convincing. (5)The research results have reference value for the design of tram short sleeper embedded track and subgrade. 
2018 Vol. 35 (1): 23-28 [Abstract] ( 10771 ) HTML (1 KB)  PDF  (519 KB)  ( 2847 )
       Railway and Rail
29 Mapping Relationship between the Temperature and Longitudinal Displacement of Rails at the Transition between the Bridge and Tunnel Hot!
ZENG Zhi-ping1, LUO Jun1, RAO Hui-ming2, WU Zhi-peng1
Abstract：Research purposes： The rails at the transition between bridge and tunnel will crawl longitudinally under the effect of temperature gradient, which influences the stability of CWR. Taking the rail at the temperature transition zone as the research object, the differential equation of rail displacement was established, the mapping relationship between rail temperature distribution and longitudinal displacement was deduced, and the law of influencing rail crawl of ballastless track was revealed in this paper.  Research conclusions： (1) The longitudinal deformation and its range of nonlinear resistance model is much larger than the linear resistance model; for the rail maximum displacement, the non-linear distribution of rail temperature is 5.3%~38.6% higher than that of the linear distribution. It is suggested to consider the non-linearity of rail temperature and longitudinal resistance to accurately obtain the rail displacement at the transition. (2) When the rail temperature difference is constant, with the maximum temperature force gradient ratio k varying from 1.5 to 3.5, the largest rail longitudinal displacement increases only 7% when the transition zone length is 10 m but it increases 26.7% and 32.8% respectively when the length is 40 m and 50 m. Thus, more attention should be paid to the nonlinear rail temperature distribution for the transition with high rail temperature difference and long rail temperature transition zone. (3) The increase of limit resistance of fasteners will reduce the rail crawl significantly, but the influence degree is limited. The rail displacement decreases 40.8%~49.2% with the limit resistance varying from 6.5 kN/(m·rail) to 12 kN/(m·rail), but when the resistance changes from 24 kN/(m·rail) to 30 kN/(m ·rail), the slippage only is only 12.8%~24.4%. (4) The analytical expressions can accurately describe the mapping relationship between the parameters and the rail longitudinal displacement and provide useful references for further study of force characteristics of rail at the transition and improving the stability of CWR. 
2018 Vol. 35 (1): 29-35 [Abstract] ( 13456 ) HTML (1 KB)  PDF  (739 KB)  ( 3081 )
36 Mechanical Analysis and Arrangement Study of REJ for CWR on Cable-stayed Bridge
CAI Xiao - pei1, MIAO Qian1, LI Da - cheng1, XU Juan - juan2
Abstract：Research purposes： Compared with the common railway bridge, the interaction between the bridge and rail on cable- stayed bridge with large span and long beams is more complicated. There is little related research and engineering application of continuous welded rail (CWR) on the long span cable-stayed bridge. Especially, the research on the interaction between structures, mechanical behaviors and optimal arrangement of rail expansion joints (REJ) are relatively inadequate. In this paper, based on the Anqing - Jiujiang Railway Yangtze River Long-span Cable-stayed Bridge, the spatial coupling model of CWR on bridge is established and the design schemes of CWR on the bridge are studied and analyzed.  Research conclusions： (1) Due to that temperature span of cable-stayed bridge is large and the REJ is not used, the rail strength and track stability cannot meet the requirements of the standards when the whole bridge is laid with constant and small resistance fasteners. (2) In order to reduce the interaction between the beam and rail, two sets of one-way REJ are arranged at both ends of the main beam. (3) Switch rail of REJ should be arranged on the continuous main beam with constant resistance fasteners. The stock rail is located at the simply supported beam of the side span. Small or constant resistance fasteners can be laid on the stock rail side. (4) The research can be used as reference for design and checking, structural optimization and arrangement of REJ for CWR on cable-stayed bridge.
2018 Vol. 35 (1): 36-41 [Abstract] ( 10019 ) HTML (1 KB)  PDF  (689 KB)  ( 2743 )
42 Dynamic Influence of Profile Parameters on LIM Train Hot!
WEI Qing-chao1, ZANG Chuan-zhen1, NIE Xin-lu2, WANG Xiao1, WANG Gang1
Abstract：Research purposes： The influence of profile parameters on the travelling comfort and safety of the LIM train should be determined. Based on the data of LIM metro system at Capital Airport Express, a three- dimensional train-line coupling dynamic model was established. The dynamic response characteristics of LIM metro system under the influence of profile parameters and train speed were analyzed. The fitting relation formula between the maximum vertical acceleration, the maximum vertical wheel rail force, the maximum wheel load reduction rate, vertical curve type, vertical  curve radius and train speed were obtained.  Research conclusions： (1)The concave vertical curve will increase the vertical acceleration of the train and the vertical force of the wheel and rail, and reduce the wheel load reduction rate.(2)The convex vertical curve will reduce the vertical acceleration of the train and the vertical force of the wheel and rail, and increase the wheel load reduction rate.(3)The maximum vertical acceleration of the train, the maximum vertical force of wheel and rail, the maximum wheel load reduction rate are related to the reciprocal of curve radius.(4)The maximum vertical acceleration of the train, the maximum vertical force of wheel and rail, the maximum wheel load reduction rate are related to the square of vehicle speed.(5)The research results can provide the theoretical basis for the optimization of LIM metro system′s profile parameters.
2018 Vol. 35 (1): 42-48 [Abstract] ( 12147 ) HTML (1 KB)  PDF  (909 KB)  ( 2802 )
49 Research on the Stability Theory of CRTS Ⅱ Slab Ballastless Track on High-speed Railway
ZHANG Xiang-min1，ZHAO Lei2
Abstract：Research purposes： The upwarp deformation of longitudinal connected track slab is one of the major disease forms of CRTS Ⅱ slab track in China at present. Based on the combination of differential equation method and energy method, adopting the track bending deformation patterns with sing-wave, the stability analysis models of longitudinal connected straight track slab and curved track slab which is considering vertical curve are established, and the formula of stability calculation is deduced, and the influence regularity of the parameters related to the stability of the track slab is studied.  Research conclusions： (1) For CRTS Ⅱ slab ballastless track, the theory of stability of CWR (continuous welded rail) should be used to analyze the stability of longitudinal connected tack slab, and obtain the minimum critical temperature rise amplitude of the track slab, providing the basis for the stress free temperature of the slab during construction. (2) The open joints or the weakening between track slab and the interface of mortar is the most immediate cause of the upwarp deformation of longitudinal connected track slab. The reduction of the bond strength of CA mortar will lead to the 〖HJ〗marked decline of the critical buckling load of the track slab. When the bond strength of the cement and asphalt (CA) mortar is reduced by 50%, the minimum critical slab temperature will be reduced by 25%; When the longitudinal resistance of the track slab is reduced by 50%, the minimum critical slab temperature will be reduced by 5.7% and the critical versine will increase by 38.1%. The larger the initial bending of the track slab, the lower the minimum critical slab temperature, also the critical wavelength is longer and the critical versine is reduced. The effect of the vertical curve on the stability of the track slab is very small, and the reduction of minimum critical temperature force is not more than 1%. (3)The research results clarify the mechanical mechanism of the upwarp deformation of longitudinal connectedtrack slab and the influence rules of the key parameters, which can provide theoretical reference for the stability study of CRTS Ⅱ slab ballastless track on high-speed railway. 
2018 Vol. 35 (1): 49-55 [Abstract] ( 10713 ) HTML (1 KB)  PDF  (537 KB)  ( 2886 )
56 Influence of Creep Camber of Bridge on Dynamic Characteristics of Railway with Longitudinal Connected Ballastless Track on Bridge Hot!
XU Qing-yuan, LIN Qing-teng, FANG Zi-yun, LOU Ping, ZHANG Ze
Abstract：Research purposes： Creep camber is likely to appear in the prestressed bridges of high-speed railway which is very sensitive to track irregularity. It is a serious problem in engineering to study the influence of irregularities caused by creep camber of prestressed bridge on the train-longitudinal connected slab track-bridge coupling dynamic system. Based on vehicle-track coupling dynamic theory, a three-dimensional finite element coupling dynamic model of high speed train-longitudinal connected slab track-bridge, which considered the nonlinear contact among different components of slab track-bridge system, was established and verified. Using the established dynamic model and taking high-speed train passing longitudinal connected slab track on bridge with creep camber, the dynamic characteristics of the coupling system were studied.  Research conclusions： (1) The creep camber of bridge has a great influence on the vibration acceleration of train, however, the influence on the vibration acceleration of bridge is not obvious. (2) The creep camber of bridge has some influence on maximum wheel-rail force, positive bending moment of rail, tension force of fastener, tensile stress of track slab and base plate, pressure stress of CA mortar, but the influences for them are different. It has relatively small influence on maximum wheel-rail force, but large influence on maximum positive bending moment of rail, tension force of fasteners, tensile stress of track slab and base plate, pressure stress of CA mortar. (3) The local void among the slab track-bridge system caused by creep camber of bridge has a great influence on the dynamic stress characteristics of high speed train-longitudinal connected slab track-bridge coupling system. (4) The research results will provide theoretical basis to control the value of creep camber of prestressed bridge of high-speed railway with longitudinal  connected slab track on it. 
2018 Vol. 35 (1): 56-61 [Abstract] ( 11529 ) HTML (1 KB)  PDF  (591 KB)  ( 2805 )
62 Effects of Parameters of CRTS Ⅱ Slab Track on Frequency Responses of High-speed Vehicle
XU Jin-hui1, WANG Xin2, HUANG Da-wei1, WANG Biao3
Abstract：Research purposes： To study the effects of structural parameters of CRTSⅡ slab track on the operation quality of vehicles, a dynamic analysis model of high speed vehicle - CRTSⅡ slab track vertical coupling system was established. Frequency analysis method and symplectic method were combined to solve the frequency responses of the coupling system, and the influence on frequency responses of high speed vehicle of slab thickness, concrete supporting layer thickness, stiffness and damping of fastening system, elastic modulus and damping of CA mortar was studied.  Research conclusions： (1)The track parameters have negligible influence on the vibration of car-body and bogie, but have large influence on wheel-rail vertical force and wheel-set vertical acceleration. (2)The thickness of slab should not be too large or too small. If the thickness of slab is too large, the vibration in the range of 50~70 Hz of wheel-set vertical acceleration and wheel-rail vertical force will be increased. In turn, if the thickness of slab is too small, the vibration in the range of 30~50 Hz of wheel-set vertical acceleration and wheel-rail vertical force will be increased too. (3)Under the premise of satisfying track structure strength, appropriately reducing the thickness of concrete supporting layer can decrease wheel-set vertical acceleration and wheel-rail vertical force. (4)Under the premise of satisfying track geometry and track dynamic displacement, adopting fastening system with small stiffness and large damping can decrease wheel-set vertical acceleration and wheel-rail vertical force. (5) The research results can provide a theoretical basis for the design of CRTS II slab track and promote the development of China's high speed railway. 
2018 Vol. 35 (1): 62-69 [Abstract] ( 9951 ) HTML (1 KB)  PDF  (1164 KB)  ( 2775 )
       Bridge Engineering
70 Dynamic Responses of a Ballastless Track Bridge under Debris Flow Impacts
ZHANG Xun, WEN Zhi-peng, LIU Rui, RUAN Ling-hui, LI Xiao-zhen
Abstract：Research purposes： The debris flow impacts give rise to additional deformations of the ballastless track on bridge, resulting in threats to the operation of high-speed trains. One key to study the problem is to determine the debris flow load model and its influences. A simplification model of the debris flow load is presented in this paper, which considers the slurry pressure, boulder impact and the effect of dragon-head and dragon-tail. A multi-span simple beam bridge on Chengdu-Lanzhou high- speed railway is taken as the study case, and the three-dimensional finite element model of the ballastless track-bridge is built to investigate dynamic responses in terms of lateral displacements at piers' top, lateral displacements at girders' mid-span and lateral relative displacements of rail supports at the end of adjacent spans. At last, parametric studies are carried out to study the influence rules.  Research conclusions： (1) The occurrence moment of the peak dynamic response is slightly later than the time of boulder impacts, and the dynamic responses are sensitive to the magnitude and height of the debris flow load. (2) Dragon-head and dragon-tail effects give rise to significant differences on lateral displacements at piers′ top and lateral displacements at girders′ mid-span, while marked variations only appear in the dragon-tail part for lateral relative displacements of rail supports at the end of adjacent spans. (3) The lateral displacements at piers′ top and the lateral displacements at girders′ mid-span are observed to be slightly increased by increasing the duration of the single boulder load; however, significant increases are found in the lateral relative displacements of rail supports at the end of adjacent spans. (4) The research results can provide good reference for subsequent study of running safety of high speed trains on bridges subjected to debris flow impacts.
2018 Vol. 35 (1): 70-77 [Abstract] ( 9790 ) HTML (1 KB)  PDF  (1400 KB)  ( 2792 )
78 Calculation and Analysis of the Straddle-type Monorail Vehicle-track Beam Coupling Vibration Hot!
LI Xiao-zhen, GE Yan-long, JIN Zhi-bin
Abstract：Research purposes： In order to evaluate the driving stability and comfort performance of straddle-type monorail transit, the dynamic interaction between vehicle and track beam is studied. A spatial coupling vibration model of monorail system is established before the calculation program is self-compiled for simulation analysis. The dynamic characteristics of standard PC track beam are calculated and assessed, and the influence of different speed and passenger volume on dynamic responses is discussed.  Research conclusions： (1) The relationship between midspan displacements of track beam and vehicle speed is not obvious in vertical and transversal directions. The transversal and vertical accelerations of track beam and lateral responses of pier top increase with the rise of the travel speed. Augment of passenger volume will increase the vertical deflection of track beam. (2) The transversal and vertical accelerations of vehicle increase with the rise of the speed, and decrease with the enlargement of the passenger volume. (3) Standard track beam performs well, and the monorail vehicle can pass through the track beam smoothly under designed condition of speed and passenger volume. (4) This research result can provide reference for structure design and traffic management of straddle-type monorail transportation.
2018 Vol. 35 (1): 78-83 [Abstract] ( 10054 ) HTML (1 KB)  PDF  (733 KB)  ( 3079 )
84 Discussion on Design Method of General Safety Factor of Composite Lining Tunnel Hot!
XIAO Ming-qing
Abstract：Research purposes： Composite lining is often used in the railway, highway and other traffic tunnels, and the primary support is generally designed by layer structure method or engineering analogy method, while the secondary lining is usually designed by load structure method, so it is difficult to evaluate the structural safety uniformly due to the difference of analysis methods. The current tunnel design code only specifies the safety factor requirements of secondary lining, but the composite lining is not a single structure, so it is necessary to study the general safety factor of primary support and secondary lining. And it is necessary to study the load-structure model of primary support to establish the design method of total safety coefficient.  Research conclusions： (1) For composite lining structure with shotcrete and rock bolt support, the surrounding rock pressure increases with the increase of the buried depth, therefore the tunnel support parameters should be adjusted according to the buried depth. (2) The unified design method of composite lining including primary support and secondary lining can be established by the load-structure model. (3) The general safety factor of composite lining tunnel should include the safety contribution of both primary support and secondary lining. When using steel reinforced concrete as secondary lining, the general safety factor should be not less than 3.0, or else not less than 3.6. （4）Different distribution of safety factor on primary support and secondary lining suggested by different design methods is shown in table 2. (5) The result of reanalysis on the structural safety of existing high-speed railway tunnel using this design method shows that when the buried depth is about 300 m, the supporting parameters of tunnel in surrounding rock of Ⅲand Ⅳ grade can be further optimized. (6) The research results can provide ideas and methods for structural design of composite lining tunnel.
2018 Vol. 35 (1): 84-88 [Abstract] ( 10066 ) HTML (1 KB)  PDF  (444 KB)  ( 7279 )
       Tunnel Engineering
89 Numerical Calculation and Analysis on Effects of Pilot Heading of Xinchengzi Tunnel with Small Spacing
LIU Zhi-qiang, SONG Ye, WANG Ren-jie, WU Jian
Abstract：Research purposes： This study is aiming at the engineering difficulties of the tunnels with small spacing, including the multi-cavity effects and the stability of interval rock pillars. At present, the domestic current study is mainly focused on conditions of shallow-buried, urban region and general surrounding rocks and on the contrary, little study on tunnels with small spacing in squeezing rocks is made. In this paper, by means of numerical calculation and data statistic analysis, the effects of pilot headings with small spacing in squeezing rocks is studied, which can provide a reference for similar projects.  Research conclusions： (1)For the tunnels with small spacing in squeezing rocks, the impacts of neighboring tunnel on main tunnel excavation include the plastic deformation of interval rock pillar and the deformation release of neighboring tunnel, of which two deformations shall be overlapped and interacted. (2) The influential range of heading tunnel excavation is between 1.5B in front of working face and 2B behind working face. (3) The effects of pilot heading can obviously reduce the impacts of following tunnel excavation on heading tunnel, meanwhile the displacement of tunnel with pilot headings can reduce to 10~20% of tunnel with no pilot headings and its influential range drops to within the limit of 1.5B. (4) The deformation statistics and analysis of Xinchengzi tunnel indicate that the deformation of following left tube is 11.6%～20.4% less than that of right tube and when the stress of pilot heading is released, the mean and maximum values of deformations in left and right tubes are reduced by 7%～20%.（5）The research results can provide reference for the design and construction of the similar tunnel in squeezing rocks. 
2018 Vol. 35 (1): 89-94 [Abstract] ( 9759 ) HTML (1 KB)  PDF  (605 KB)  ( 2838 )
95 Deformation and Interlayer Disengaging Analysis of Monolithic Track Bed under the Shield Tunnel Settlement
PENG Hua, LIANG Yan-ke, CAI Xiao-pei, MA Wen-hui
Abstract：Research purposes： Disengaging of monolithic track bed caused by shield tunnel settlement has become an important factor affecting the safety of subway operation. To reveal the mechanical characteristics of monolithic track bed under shield tunnel settlement, a spatial coupling finite element model for a track - track bed - segment lining system is established. Based on the segment settlement monitoring data of Beijing Subway Airport Line T2, the deformation and failure characteristics of monolithic track bed are analyzed under disengaging of it.  Research conclusions： (1) When wave trough of local settlement at the expansion joint occurs in segment, fractures appear on the surface of the track bed at the settlement starting point, as well as two sides of the track bed bottom. When settlement trough is located in the middle of two expansion joints, a large scale of cracking phenomenon appears on the surface of track bed at the settlement starting point, while cracks appears on both sides of the bottom of the track bed and the track bed at settlement trough. (2) When the segment is in continuous settlement, and two subsidence troughs are not located in the expansion joint, the crack will appear at the bottom of a large range of bed surface, and tension stress is relatively small, without cracking. When the trough of one segment settlement area is located at the expansion joint, there will be cracking on both sides of the track bed, and a wide range of cracking on the surface of the 〖HJ〗ballast. (3) The research achievement has a certain value of reference for the maintenance in the shield tunnel of metro. 
2018 Vol. 35 (1): 95-99 [Abstract] ( 10027 ) HTML (1 KB)  PDF  (813 KB)  ( 2936 )
       Engineering Economy and Management
100 Research on the Relationship between High Speed Rail Project and Land Use Change in Beijing- Tianjin-Hebei Region
ZHU Tao-xing, ZHU Zheng-guo, REN Jian-xin
Abstract：Research purposes： High-speed railway affects population mobility and raises the demand for land products and services, and thus leads to the increase of land use intensity and renovation of land use patterns. Taking Beijing-Tianjin-Hebei region as an example, this paper studies the relationship between high-speed railways and regional land use intensity, as well as the influence of high- speed railways on regional land use forms. In the analysis, social network efficiency index and regional land use efficiency index are constructed, and Pearson correlation coefficient and grey correlation analysis are adopted.  Research conclusions： (1) Since the operation of high-speed rail, the efficiency of railway transportation network structure has changed obviously among urban nodes, and the connection degree among each node has been quite different in Beijing-Tianjin-Hebei region. (2) It is found that, along with the growth of regional high-speed railway lines, the most significant changes of land use types in Beijing-Tianjin-Hebei region occur in commercial land use and high-grade residential lands. In the meanwhile, the impact of the growth of high-speed railway lines on changes in land use type is relatively minor with respect to affordable housing, low-cost housing, and public administration and service lands. (3) The improvement of high-speed rail network is changing land use pattern in Beijing, Tianjin and Hebei, and construction land use starts putting more emphasis on commercial service lands and high-end industries.(4) The research conclusion can provide decision-making basis and guidance for the spatial orientation of high-speed railway planning and construction. 
2018 Vol. 35 (1): 100-105 [Abstract] ( 9830 ) HTML (1 KB)  PDF  (400 KB)  ( 2761 )
106 Thinking on the Sustainable Development of Survey and Design Enterprises under the New Situation
LUO Jing-feng
Abstract：Research purposes： China is in a key period of economic structural adjustment and transformation and upgrading, we actively promote supply-side structural reform, promote the economic transformation and industrial structure adjustment. The survey and design enterprise is faced with the complicated external environment, and will enter a critical period of adjustment and reshuffle in the future. In view of this, combined with the current macro-economic situation and industry development environment, this paper analyzes the opportunities and challenges of survey and design enterprise development, and puts forward the countermeasures and ways for the sustainable development of enterprises, to promote the healthy and sustainable development of survey and design enterprise.  Research conclusions： Through the analysis of the macro-economic environment and industrial development environment faced by the survey and design enterprises, it is concluded that :(1) Innovate and develop market development mode, and enter the potential market region; (2) Improve the overall contract strength of the project and expand the total contract market share; (3) Strengthen scientific and technological innovation and achievements transformation, and enhance the core competitiveness of enterprises; (4) Strengthen personnel training and improve the construction of talent team; (5) Strengthen information construction and improve the depth and breadth of application; (6) The research results have certain reference significance for the sustainable and healthy development of the current survey and design enterprises.
2018 Vol. 35 (1): 106-110 [Abstract] ( 10180 ) HTML (1 KB)  PDF  (487 KB)  ( 2917 )
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