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2017 Vol. 34, No. 11
Published: 2018-01-05
Geology and Subgrade
Railway and Rail
Bridge Engineering
Tunnel Engineering
Survey and Design
Urban Rail Construction
Engineering Economy and Management
Communication Signals
 
       Survey and Design
1 Re-exploration on General Layout Planning of Railway Hub Hot!
JING Feng-Ming
Abstract：Research purposes： The general layout planning of railway hub is the important support of "mid-long term railway network plan". The general layout planning of railway hub is difficult to be operated in the specific hub design. Through the analysis of the backgrounds, advantages and shortcomings of the general layout planning of railway hubs based on 2002 edition and the analysis of current situation, development trend and future prospects of social-economic structure in China, the paper summarizes the relationship between the general layout planning of railway hub and social-economic development of the city. This paper emphatically discusses the rational range of study in planning of railway hub, the layout of ring line, marshalling station, passenger station, comprehensive modern logistic park, and general configuration of the railway hub as well, to provide reference for research direction of general layout planning of railway hub.  Research conclusions： (1) The general layout planning of railway hub is closely related to the planning of the urban economic and social development. (2) It is very important to interpret correctly the mid-long term development plan of the nation & city's social- economic development. (3) The planning scope of the general layout of railway hub can appropriately break through the administrative divisions. (4) In planning year, the layout planning of passenger transport system should be improved to a new higher level in the general layout of railway hub, where more and more high-speed railways and intercity railways will appear in line composition of railway hub. (5) The research results can provide a reference for general layout planning of railway hub and design of railway station and hub.
2017 Vol. 34 (11): 1-4 [Abstract] ( 3609 ) HTML (1 KB)  PDF  (521 KB)  ( 2685 )
       Geology and Subgrade
5 Research on the Relationship between Perforated Sand-blocking Wall and Sand-blocking Effect
LI Kai-chong，SHI Long，JIANG Fu-qiang，XUE Chun-xiao，KONG Ling-wei
Abstract：Research purposes： As a kind of common engineering resistance measures, sand-blocking wall mainly used to intercept sand- drift and protect the railway. Many studies have obtained great achievement, which is about the action mechanism of sand-blocking wall. However there is less research on the relationship between perforated sand-blocking wall and sand-blocking effect. Through the research of them, the optimum design parameters were obtained, which will provide some technical support for the design and construction.  Research conclusions： (1) Sand collection quantity and the opening angle of sand-blocking wall showed normal distribution. Sand collection quantity reached maximum when the opening angle is 135°(2) When the airflow passes through the sand-blocking wall, the horizontal flow field presents a "V" shape, and the air velocity reaches the minimum at the wall. (3) Irregular arch distribution is discovered between the sand- blocking rate and the vertical height. Within 1 meters height, the sand-blocking rate of the wall with the opening of 135°is the highest, the middle is 45°, and the lowest is 0°.（4）Sand accumulation shape of the sand-blocking wall show a parabolic distribution. When the opening angle is 135 °, the initial projectile angle of the sand is the largest, the boundary line is the steepest, the desert ridge line is furthest away from the wall, and sand is easy to clean up. (5)The experimental results have guiding significance for the design and construction of sand-blocking wall.
2017 Vol. 34 (11): 5-8 [Abstract] ( 3301 ) HTML (1 KB)  PDF  (544 KB)  ( 2591 )
9 Experimental Research on the Mechanical Properties of Improved Red Soil Subgrade in Rich Water Area Hot!
XU Hua1, ZHANG Yi-bo1, ZHANG Jie1, YOU Guan-jun2, WANG Xin-yu1
Abstract：Research purposes： To solve the high-water content and uncompacted problems for red clay subgrade in rich water area, improved subgrade material with different water content was made by mixing original soil with weakly weathered red-mudstone gravel, which was sorted by a certain ratio of the particle size. Heavy compaction test, large direct shear test and unconfined compression test were conducted to get the filling material that meet the requirement of the railway subgrade construction.  Research conclusions： (1) The water content of original red soil can be reduced effectively through adding weakly weathered mudstone gravel. The optimum water content of the improved material is 10.26%, and the maximum dry density is 2.22 g/cm3. (2) The cohesion c of the improved material is 29.336 kPa and the friction angle φ is 32.86°, when the improved material is at optimum water content. Compared to the natural soil of red layer, the shear strength of the improved material has significantly improved. (3) Unconfined compressive strength of the improved material reaches 518.80 kPa when water content is about 8.85%, and decreases gradually with the increase of the water content. (4) Through mixing the weakly weathered red mudstone gravel with red clay, the characteristics of red clay do not change, and the water content of original soil can be reduced effectively as well, and the shear strength and deformation capacity also are increased. Besides, water content and compaction performance of the improved material can meet the requirements of railway subgrade design criterion. (5) The improved scheme can provide a reference for the southwest rich red layer area in railway subgrade engineering. 
2017 Vol. 34 (11): 9-13 [Abstract] ( 5328 ) HTML (1 KB)  PDF  (678 KB)  ( 2663 )
14 Influence of the Interaction between Frozen-thaw Cycles and Train Dynamic Loads on the High-speed Railway Subgrade Settlement
JIN Li-qiang, LI Hong-sheng, LIU Zeng-li, XING Huai-nian, LI Da, LI Shu-hui
Abstract：Research purposes： In recent years, the high-speed railway in China has developed rapidly, and its subgrade settlement has attracted more and more attention from the engineering community. But the research of subgrade settlement in seasonal frozen soil area is still in its initial stage. In this paper, first we study the characteristics of the high-speed railway subgrade in seasonal frozen area and the interaction between dynamic load and frozen-thaw cycles. Then we study the types, mechanism and development law of subgrade settlement. Finally we give a calculation model, method and an example.  Research conclusions： (1) Under the interaction between dynamic load and frozen-thaw cycle, subgrade settlement has different nature and mechanism in different cycle stages. (2) The subgrade settlement in seasonal frozen soil area includes compressibility settlement, pressure-dense settlement and thaw settlement. The maximum volume of settlement is produced during thawing of frozen soil. (3) The mechanism of settlement is mainly affected by the composition of soil, such as gas, unfrozen water and mineral particles, and under dynamic load the change of porosity is an important factor affecting the settlement. (4) The results of this paper can provide reference for subgrade design and maintenance in seasonal frozen soil area, and provide basis for the design and construction of high-speed railway subgrade settlement control.
2017 Vol. 34 (11): 14-18 [Abstract] ( 3223 ) HTML (1 KB)  PDF  (325 KB)  ( 2533 )
19 Application of the Non-excavation Retaining Structure on Cutting Deformation Control in High Speed Railway
ZHANG Zhan-rong
Abstract：Research purposes： The deformation control requirements of high-speed railway ballastless track subgrade engineering are very strict. To ensure the comfort and safety of the train operation, the subgrade of high-speed railway with operation does not allow any deformation. After a high-speed railway was opened to traffic, a section of cutting slope was obviously deformed and destroyed, which seriously affect its operational safety. In view of the characteristics of high density of train operation, high speed and high construction risk, a treatment scheme combining micro disturbance non-excavation retaining structure with risk management is put forward.  Research conclusions： (1) The slope deformation was controlled and the slope stability was improved, after using the steel pipe micro pile with DTH drill and through the lock beam connected into a whole part. The disturbance of subgrade slope is small in construction process of this technology, which is an important principle and conception for the treatment of high speed railway deformation diseases. (2) The construction risk of high speed railway deformation treatment is very high, and the risk management concept should be taken into account to the engineering design. To ensure the success of the treatment of high speed railway deformation diseases, the risk factors of the treatment scheme should be identified, and the detailed risk treatment measures should be formulated. (3) After construction, cutting deformation was controlled. The treatment technology of high speed railway deformation diseases combining micro disturbance non-excavation retaining structure with risk management can provide reference for the future high railway cut deformation treatment. 
2017 Vol. 34 (11): 19-24 [Abstract] ( 3657 ) HTML (1 KB)  PDF  (457 KB)  ( 2621 )
       Railway and Rail
25 Lateral Resistance Test and Mechanics Analysis of Bi-block Sleeper Hot!
JING Guo-qing1, QIANG Wei-le1, JIA Wen-li1, YAO Li2
Abstract：Research purposes： The lateral resistance of the sleeper is an important parameter to the geometric stability of the track and the transverse stability of the CWR. With the development of ballasted track operation conditions becoming more complex, more challenges are posed to the design and selection of the sleeper and developing RAMS oriented sleepers has been a hot research point. There are few researches on the bi- block sleeper on the ballasted track bed and its lateral resistance in China. In this paper, a series of lateral resistance tests for the bi-block sleeper and the Ⅲc mono sleeper were carried out to investigate the basic characteristics and influence of the lateral resistance for the bi-block sleeper.  Research conclusions： (1) Under the same ballast bed dimension, the bi- block sleeper produces more lateral resistance than the Ⅲc mono sleeper, with the variation of 13.6%~25.5%. (2) Raising the shoulder width can increase the lateral resistance of both the bi- block and Ⅲc mono sleeper with little difference. (3) Raising the shoulder height, which can significantly increase the lateral resistance, is more effective for the bi-block sleeper. For example, when the shoulder height increases from 0 mm to 150 mm, the lateral resistance increases by 4.2 kN ( 51.9%) for the bi-block sleeper, while 2.7 kN (38.0%) for the Ⅲc mono sleeper. (4) The conclusions of this paper lay the theoretical and experimental foundation for the application of the bi-block sleeper in the track engineering in China. 
2017 Vol. 34 (11): 25-28 [Abstract] ( 5979 ) HTML (1 KB)  PDF  (745 KB)  ( 2616 )
29 Longitudinal Force Analysis of Tram Embedded Track on Simply Supported Bridge
FENG Qing-song1，SUN Kui1，LUO Xin-wei2，LIU Qing-jie1，ZHANG Peng-fei1
Abstract：Research purposes： The interaction between rail and beam of CWR on bridge is really complex, and the stress and deformation characteristics of bridge and track structure become a hot research topic of scholars at home and abroad. In order to study the force and deformation and influence factors of track structure under temperature load, train load and braking load, according to the characteristics of the embedded track, the finite element model of embedded track CWR on bridge is established, the force and deformation of the track structure under three conditions are calculated, such as expansion-constriction force, deflection force and braking force, the influence of beam temperature difference, the longitudinal resistance of polymer material and the longitudinal stiffness of the pier on the expansion-constriction force is analyzed.  Research conclusions： (1) The longitudinal resistance and vertical stiffness of the embedded track are linear, and the relative displacement limit between rail and substructure is determined to be 6.2 mm. (2) The force and deformation of track structure increase linearly with the increase of beam temperature difference, and the allowable beam temperature difference is 38 ℃;With the increase of the longitudinal resistance of the track, the longitudinal displacement and the expansion- constriction force of the rail increase gradually, while the relative displacement between rail and substructure decreases gradually; The longitudinal stiffness of the bridge piers has little effect on the force and deformation of the track structure. (3) Under the condition of deflection force and braking force, the relative displacement between rail and substructure and the additional force of rail are small, so the expansion-constriction force condition should be paid attention to in the design. (4) When the beam temperature difference and the change of the rail temperature is 30 ℃, the strength of rail and the relative displacement between rail and substructure meet the requirements. Therefore, it is feasible to lay the embedded track on 32 m simply supported beam. (5) The research results have reference value for the design of tram embedded track on bridge.
2017 Vol. 34 (11): 29-32 [Abstract] ( 3257 ) HTML (1 KB)  PDF  (681 KB)  ( 2530 )
33 Research on the Mechanical Behavior of Concrete- filled Round-ended Weathering Steel Tubular Stub Columns under Axially Compressive Loading
DING Fa-Xing, FU Qiang, FANG Chang-Jing
Abstract：Research purposes： In order to study the mechanical behavior of concrete-filled round-ended weathering steel tubular stub columns, this paper carried out 4 concrete- filled weathering steel tubular stub columns in round-end forms experiments. The finite element (FE) method is used to analyze the concrete-filled weathering steel tubular stub columns. Analysis and comparison of the difference between concrete-filled weathering steel tubular stub columns and concrete- filled steel tubular stub columns was based on the finite element method and experiment results.  Research conclusions： (1) The constitutive relation of steel used in this paper is suitable for weathering steel and the steel tensile performance test shows that the mechanical properties of weathering steel and carbon steel are similar. (2) The ultimate bearing capacity, ductility and the restraint effect of steel tube on concrete are greatly improved with the confining stirrup. (3)The experimental results and finite element analysis results show that the static mechanical properties of concrete-filled round-ended weathering steel tubular stub columns and concrete- filled steel tubular columns are no significant difference. (4)The research results can provide the reference for the mechanical properties of the concrete-filled round-ended weathering steel tubular stub columns.
2017 Vol. 34 (11): 33-37 [Abstract] ( 3308 ) HTML (1 KB)  PDF  (858 KB)  ( 2570 )
       Bridge Engineering
38 Cooling Method Numerical Analysis of Suspender Cable Tension and Cable Saddle Pushing
ZHANG Hai-shun1, WANG Yu-yin2
Abstract：Research purposes： When the long-span self-anchored suspension bridge could not use the general support method to install the steel box girder of main span, the "first cable-stayed, second suspension" overall construction plan was adopted in the world first. The most important process of the scheme was the system transformation from cable-stayed bridge to self-anchored suspension bridge. The suspender cable tension and main cable saddle pushing were realized in the numerical simulation of system transformation. The cooling method similarly with unstressed state control method was applied. Guided by this method, the system transformation whole process of Egongyan self-anchored suspension bridge was analyzed. The Egongyan self-anchored suspension bridge will be the world's largest span of 600 m self-anchored suspension bridge after the completion. The element selection and its parameter determination methods and techniques of the key components of suspension bridges were expounded in the state of two kinds of cable support system coexistence using ANSYS.  Research conclusions： Through the numerical simulation, the changing rules of key components in the process of system transformation were analyzed.The conclusions are as follows: (1)All the cable units of the two models used their unstressed length to build the model under unstressed state control method. The coupling analysis model was remodel using the iterative  calculation. (2) The cooling method makes the suspender cable cool to its unstressed cable length from modeling length. The cooling method also makes the deviator of main cable saddle cooled to near zero and realize the main cable saddle pushing. (3) The cooling method can be used in the calculation models of the suspension bridges system transformation process at suspension cable tension and main cable saddle pushing.
2017 Vol. 34 (11): 38-42 [Abstract] ( 3368 ) HTML (1 KB)  PDF  (838 KB)  ( 2559 )
43 Seismic Design of the Continuous Rigid Frame Bridge with Double Thin-walled Short Piers in High Intensity Earthquake Area Hot!
ZHANG Yong-liang，LU Xiao-su，CHEN Xing-chong，WANG Yun
Abstract：Research purposes： Taking the continuous rigid frame bridge with double thin-walled short solid piers in high intensity earthquake area as the research object, and focusing on the overall seismic performance of the substructure, a selection method of ductility seismic system for the pier of this kind of the bridge is presented based on the three level fortification target. The relationship between section size, longitudinal reinforcement ratio and structural seismic performance of double thin-wall short piers is systematically discussed.  Research conclusions： (1) For the double thin-wall short piers of the continuous rigid frame bridge in high intensity earthquake area, the failure modes should be judged according to the shear span ratio of piers, and then the seismic ductility classification and design method are also chosen. (2) Under the excitation of low-level earthquakes, the section size and reinforcement design of main pier are controlled by the longitudinal seismic response of the bridge, the longitudinal bending moment of the critical section of main piers is obviously increased with the increase of wall thickness, and the amplitude of increase was greater than that of transverse excitation. (3) Under transverse high-level earthquake excitation, only the perfectly elastic or basic elastic structure could be adopted because the shear span ratio of the pier in the transverse direction was relatively small. This will cause the fact that the reinforcement ratio of the pier and the pile foundation is significantly increased, so it became the main factor to control the design of the substructure. (4) Under the longitudinal high-level earthquake excitation, the demand of plastic rotation of main piers decreases when wall thickness increases, under the three combinations of wall thickness and longitudinal reinforcement ratio, the plastic rotation capacity of the plastic hinge achieves the seismic fortification target of "No Collapsing in the Strong Earthquake", and its deformation capacity and safety reserve is basically equal. (5) The research results can provide a reference for the seismic design of similar bridges. 
2017 Vol. 34 (11): 43-47 [Abstract] ( 6094 ) HTML (1 KB)  PDF  (581 KB)  ( 2617 )
48 Mapping Relationship between the Bridge Pier′s Displacement and Rail Deformation of High-speed Railways under the Influence of Sunshine Temperature Hot!
WU Bin1, LIN Zhi-hua1, ZENG Zhi-ping1, XIE Hong2, RAO Hui-ming3
Abstract：Research purposes： Under the influence of sunshine temperature, the sun side and the dorsal side of the bridge pier body produce temperature difference, leading to the lateral displacement of the pier top, further causing the lateral deviation of the beam and the track and ultimately giving rise to the lateral irregularity of the rail on the bridge. In order to guide design of the pier and maintenance of the track, this paper takes double-block ballastless track of high-speed railways on the simply supported beam bridges as the research object. By adopting unit load method, the  relationship between lateral displacement and temperature difference, pier height and pier width is analyzed. Moreover, based on the principle of the interaction among lines, bridge, and piers, the mapping relationship between the lateral displacement of the pier top and the deformation degree of the rail is deduced, and the corresponding analytic expression is also proposed.  Research conclusions： (1) The displacement of the pier top under the influence of sunshine temperature is proportional to temperature difference in section direction and the square of the height of the pier, which is inversely proportional to the transverse width of the cross section. (2) The rails are deformed with the lateral movement of the pier top, and its deformation degree is proportional to the lateral displacement of the pier top and is related to the parameters such as the spacing between the fasteners and the transverse flexural rigidity of the rail. (3) Based on the analytic expression of the mapping relationship between the lateral displacement of the pier and the deformation of the rail, the transverse deformation  curve of the rail can be obtained easily according to the parameters such as pier height, pier width and pier temperature difference, which are of reference value for guiding design of the pier and maintenance of the track. (4) The research results of this paper have a reference value for studying the mapping relationship between lateral displacement and rail deformation of other unit ballastless track piers on the bridge.
2017 Vol. 34 (11): 48-52 [Abstract] ( 4155 ) HTML (1 KB)  PDF  (509 KB)  ( 2578 )
53 Experimental Study on Mechanical Properties of Lead Rubber Bearing under Multi-directional Loading
WANG Jian-qiang1, GENG Jia-shuo1, ZHAO Zhuo2
Abstract：Research purposes： At present, the research on the mechanical properties of lead rubber bearing is mainly based on the uni- directional compressive-shear test of the bearings. However, in the actual earthquake, the rubber bearing is in the multi-directional loading state. So it is necessary to study the mechanical properties of the bearings under multi-directional loading. In this paper, the low-cycle cyclic loading test method is used to study the mechanical properties of the lead rubber bearings, the uni-directional and bi- directional compressive-shear tests of the bearings were carried out. The influence of multi-directional loading on the mechanical properties of the bearings was studied, and the shear properties of the bearings under bi-directional compressive-shear state were simulated.  Research conclusions： (1) Comparing with the results of the uni-directional compressive-shear tests, the energy dissipation, yield force, post yield stiffness, horizontal equivalent stiffness, and equivalent damping ratio of the lead rubber bearings under bi-directional compressive-shear tests decrease. (2) According to the shear properties empirical formula of the lead rubber bearings under uni-directional compressive-shear tests, the shear properties of the bearings under bi-directional compressive-shear tests can be effectively simulated, but when the compressive stress is larger, the error between the calculated values and experimental values is much bigger, so it should be concerned about this case. (3) The research results are helpful to the design and analysis of the isolated structures. 
2017 Vol. 34 (11): 53-58 [Abstract] ( 3280 ) HTML (1 KB)  PDF  (994 KB)  ( 2630 )
       Tunnel Engineering
59 The Effect of Pressure Release of Gaseous Phase and Pressure Released Gather Underground Water of Gaseous Phase in Vadose Zone When Tunneling
XU Zeng-rong
Abstract：Research purposes： The people be nagged by cause of tunnel leakage and little water burst in vadose zone in long times during tunnel construction or operation. This paper finds out the main factor that affect moisture change of tunnel periphery through analysis of three phase changing of soil after excavation, reveals the cause of tunnel leakage and the formation of saturated zone, reasonably explains the question of tunnel leakage that tunnel located in the underground water level and no perched water, and puts forward new concept about gaseous phase migration and part underground water around tunnel. Research conclusions： (1)The pressure increase grads of gaseous phase in vadose zone are greater than the pressure increase  grads of atmosphere in about most mouths of one year. (2)After excavation of the tunnel, converging movement of gaseous phase in vadose zone appears, and moisture of gaseous phase generates movement, adsorption, conversion, this phenomenon is named as the effect of pressure release of gaseous phase in vadose zone in this paper. This paper thinks that this effect is another important influence except the surrounding rock change of stress field when tunneling. Partial saturated underwater in surrounding rock produced by the effect of pressure release of gaseous phase is named pressure released gather underwater of gaseous phase in vadose zone, this underground water overflowing is main reason of tunnel leakage and little water burst in vadose zone. (3)This paper can be used for the survey of engineering geology and hydrogeology in tunnel engineering and other underground engineering. 
2017 Vol. 34 (11): 59-63 [Abstract] ( 3271 ) HTML (1 KB)  PDF  (361 KB)  ( 2467 )
64 Research on the Disaster Induced Factors and Disaster Characteristics of the Surrounding Rock in Xigeda Strata Tunnel Hot!
WANG Zhi-jie, ZHOU Ping, XU Hai-yan, HOU Wei-ming, LEI Fei-ya, WANG Li, LIU Chuan-kun
Abstract：Research purposes： Because of the characteristics of argillization induced by water, the widespread Xigeda strata in the Southwestern areas severely impact the tunnel engineering construction along the Chengdu-Kunming  Railway. Thus, it is of significance to carry out the study on Xigeda strata tunnel. We made field research on the catastrophe pattern of Xigeda strata tunnel, deeply studied the catastrophe feature and mechanism of the tunnel surrounding rock in Xigeda strata by means of field sampling, indoor test, numerical modeling, field monitoring, theoretical analysis and the like.  Research conclusions：（1）When the tunnel crosses the Xigeda strata, catastrophes appear, for example, the large sedimentation of vault, big horizontal convergence, the hunching and mud burst of the inverted arch, and the collapse of face and other typical catastrophe patterns.（2）When water content ranges within 0% and 25%, the displacement changes  trends of the vault crown settlement, the horizontal convergence, the uplifting of the inverted arch, and the extracted deformation of face are basically the same. Moreover, with the gradual increase of water content during the excavation process, the deformation of the tunnel surrounding rock becomes clearer. Especially when water content gradually changes towards the value of 30% from that of 25%, the displacement changes of those parts increase sharply and when the water content reaches 30%, the accumulated sedimentation values of every part of the tunnel reach the tunnel catastrophe state. Thus, 25% of the water content can be marked as the critical value of the catastrophe of the Xigeda tunnel, while 30% of that is the catastrophe value. （3）We establish the judgment matrix and evaluate it through setting up the index system of catastrophe factor and then determine the weight of every factor by using the analytic hierarchy process. The catastrophe source factor that influences the weight most is the geology of Xigeda itself and the 〖JP2〗rock mass mechanics with the factor being 0.625 0, followed by the factor of hydrogeology, which is 0.238 5, groundwater index is the most important factor in hydrogeological factors. （4）The conclusions obtained can provide guidance  for the rapid and safe construction of Xigeda strata tunnel in the Southwestern Areas. 
2017 Vol. 34 (11): 64-67 [Abstract] ( 4153 ) HTML (1 KB)  PDF  (1467 KB)  ( 2606 )
       Communication Signals
68 Analysis of Unbalanced Coefficient of High-speed Railway Traction Return Current
MA Jiu-yang
Abstract：Research purposes： In the process of high-speed railway joint test and dynamic detection, the lack of testing methods and limit requirements for traction return index impacts on high-speed rail construction quality and dynamic acceptance. According to the current detection standards in the reflow index detection missing, this paper proposed the imbalance index assessment parameters of high-speed railway traction return current and established grading criteria, to provide the basis for rectification, dynamic detection and dynamic acceptance of high-speed railway integrated grounding system engineering.  Research conclusions： (1) The unbalanced coefficient of the ground return line of the railway is used as the analysis index of the imbalance of the traction return current. After the difference test, it is necessary to establish a set of quality criterion passing the unbalanced coefficient of ground lines, without differentiating line types. (2) The range of the backflow unbalanced coefficient of the upstream and downstream ground return is divided into β≤0.43 and 0.43<β≤0.70 which is regarded as the interval of good and qualified engineering respectively, and the value beyond the above interval is judged to be poor level. (3) The research results can be applied to the integrated grounding dynamic detection of new high-speed railway engineering joint test and dynamic detection, and can be referred for new railway projects using integrated grounding system. 
2017 Vol. 34 (11): 68-71 [Abstract] ( 3283 ) HTML (1 KB)  PDF  (540 KB)  ( 2505 )
       Urban Rail Construction
72 Analysis of the Shield Selection for Anhydrous Sand Layer in Shijiazhuang
SHANG Yan-liang1，BAO Lin2，SHI Wen-jun2
Abstract：Research purposes： With the promotion and application of shield construction technology in urban subway construction, shield equipment selection has become the key link of the shield construction process. In this paper, the problem of shield selection during the construction of earth pressure balance in anhydrous sand layer is discussed, the influence of shield selection on surface subsidence is studied and the rules of selection are summarized. Based on the data of the anhydrous sand layer shield construction of Shijiazhuang metro, the paper evaluates the shield selection of several sections and finds out the key influencing factors.  Research conclusions： (1) In the region, the surface sedimentation value caused by Komatsu shield machine with panel cutter and 40% aperture ratio is 11～14 mm. (2) In the region, the surface sedimentation value caused by Herrenknecht shield machine with composite cutter and 35% aperture rate is 7～10 mm. (3) During shields selection, the appropriate cutter type should be selected, and the small aperture ratio and the small cutter wheel torque shield model is given priority to, in order to improve the stability of excavation surface and reduce the adverse effects caused by shield excavation. (4) The research results can provide reference for the shield selection of tunnel engineering.
2017 Vol. 34 (11): 72-76 [Abstract] ( 3220 ) HTML (1 KB)  PDF  (687 KB)  ( 2531 )
77 Spatial Distribution Prediction Method of Ground Displacement Induced by Shield Tunneling Hot!
ZHANG Jin-xun1,JIANG Hua2, CHENG Jin-guo2, JIANG Yu-sheng2, QU Xing-tong2
Abstract：Research purposes： The effect of shield tunnelling-induced displacement is really a concern that should be drawn attention in metro construction. Most prediction of settlement is focused on surface and rare study on spatial distribution prediction is carried out. Therefore ，based on the engineering background of Line 14 in Beijing Subway，numerical simulation is adopted to investigate the relationship of the settlement and influence range between subsurface and surface, and a prediction method of spatial distribution for ground settlement on the basis of the combination of the transverse and longitudinal ground settlement is proposed and verified with field test.  Research conclusions： (1) Coefficients of surface settlement trough width of any cross section ahead of or behind the shield is generally equal to that of the final settlement trough. (2) The settlement troughs both in surface and subsurface reflect the normal distribution. With the increase of depth, the maximum of settlement shows a nonlinear increase of power function and the width coefficient of settlement trough reflects a nonlinear decrease of power function. (3) The ground settlement of any point is related to the maximum surface settlement value，coefficient of settlement trough width and volume loss.(4) The research results provide theoretical guidance for shield tunnelling- induced displacement in similar geological conditions. 
2017 Vol. 34 (11): 77-81 [Abstract] ( 4136 ) HTML (1 KB)  PDF  (835 KB)  ( 2619 )
       Engineering Economy and Management
82 Research on the Market Demand Risk and Sharing Mechanism of PPP Projects
WANG Jun-shan
Abstract：Research purposes： At present, the government vigorously promotes the PPP model in the field of public infrastructure, and market demand is one of the most important risk factors of PPP projects. Through sorting out the relevant literatures and domestic and international PPP project, this paper analyzes the causes, effects, theoretical basis and risk sharing preferences of demand risks, and also puts forward a risk sharing proposal.  Research conclusions： (1) The impact of market demand risks arising from competition risks, socio-economic development, deficiencies forecast and changes in government decision-making, not only directly affect the actual income of the project, but also indirectly affect the investor's confidence in project and government. (2) The market demand risk sharing should adhere to most appropriate principle (by whom to share, when to share and how to share), the emphasis of demand risk sharing in preparation stage, construction stage, and operation stage is different. (3) According to the different situations of PPP projects, the market demand risk sharing proportion and realization path should be carried out in detail and scientific decision-making. (4) The research achievements have theoretical and practical significance for improving PPP projects risk management efficiency. 
2017 Vol. 34 (11): 82-87 [Abstract] ( 3478 ) HTML (1 KB)  PDF  (361 KB)  ( 2577 )
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