Research conclusions: The loess featured with coarse particles， porousness， disintegration， relatively strong permeability，thick soil layer，strong collapsiblility，structural fracture development are main reasons for the loess sinking hole in the Longxi region． Under the main effects of water erosion and underground erosion and the auxiliary effects of the saturated yielding，disintegration，gravity and living things，the loess sinking hole is formed by the preferential seepage channel and the runoff channel of the vertical bedding joint，structural joint and unloading joint．The formation mechanism of the loess sinking hole includes the following five types: the water erosion － breakthrough

Research conclusions: Taking the main deep foundation pit of this station as the engineering background，the introduction is given to the calculation process of the incremental method for the laminated wall and the internal bracing system by using the SAP84 finite element program． The research is done on the horizontal displacement of the underground diaphragm wall，the axis force of the steel bracing system，the vertical displacement of laced column and the settlement of the surrounding buildings during the excavation． The monitored result shows the measured horizontal displacements of the underground diaphragm wall are 44 ～ 71 mm，a bit bigger than the calculated values． The maximum measured axial forces of the steel bracing are about 64 to 80 percent of the maximum calculated value． The maximum heave value of the laced column is about 20mm． The analytical results indicate the deformation of retaining structure and the settlement of surrounding buildings can be effectively controlled if the steel bracing are installed in time and the floor concrete is casted as soon as possible．

Research conclusions: The calculation thicknesses of the compression layer of the soft － soil high － compression foundation and the medium － compression clay foundation should be determined according to that the additional stress is equal to the 0． 1 time of its stress． The calculation thicknesses of the compression layer of the non － clay foundation and the low － compression clay foundation should be determined according to that the additional stress is equal to the 0． 2 time of its stress． The settlement in the reinforced range of the CFG pile composite foundation should be calculated by using the soil composite compression modulus method． When the settlement of the subjacent bed is calculated by using the equivalent entity method，its calculation result is rather closed to the real settlement． When the settlement in the reinforced range of the bored cast － in － place pile structure foundation is calculated with the pile theory and the settlement of the subjacent bed is calculated by using the stress diffusion method，their calculation results are rather closed to the measured settlement．

Research conclusions: For the soft soil or soft rock cutting，the light structure of combination of the dense spacing prestressed anchored frame beam to the steep slope with the toe remaining wall is used，and the appropriate vegetation measure is taken in the anchored frame beam，with the features of mature technology，advanced process，rationality and reliability． So，it can be widely applicated．

Research conclusions: A bi － direction searching model based on plane coordinate system is established． This model considers the geometric features of the multiple level platforms of the cutting slope and the rock stratum attitude，and it can be used to analyze the hidden sliding body one by one and search for the minimum safety coefficient about slope stability． In addition，in order to improve the analysis efficiency of the stability of the rock cutting slope，an professional software is developed by using C # programming tools to realize the automatic searching for the bi － directional structure surface of the bedding rock slope．

Research conclusions: The function was derived． The calculation was made for the standard section of the embankment slope of the ordinary railway with the Monte － Carlo method to make sure the target reliability index of the railway embankment was 2． 3 for discussing the variation of target reliability index． A set of the partial coefficients and their expressions were obtained for studying the influences of the slope parameters and the their variations on the partial coefficient． There are following three resolutions on the big variation the partial coefficients in the design: Firstly，based on the variable parameters，the reliability is directly calculated． Secondly，the partial coefficient is adjusted with the adjustment formula． Finally，on considering the partition between the main variation parameters and the variation coefficient，the different partial factors are used．

Research conclusions: ( 1) With the pier － top longitudinal support scaffolding method，the cast － in － place of the superstructure crossing the bridge can be conducted with security and high quality and efficiency． ( 2) By making full use of the pier top and space under the flange plate of the box beam to support the longitudinal bars along with sectional steel cross beam，it can be as the support platform for the outside modeling and operation． ( 3) By making full use of the existing materials，the cost can cut and the construction period can be reduced．

Research conclusions: From the testing instances，it can be seen that during the test it can not only use the sonic parameters to determine whether there is a defect in the pile，and various kinds of the parameters should be used together to determine whether there is a defect in the pile and what are the defect range and level． If the defects of the accumulation of aggregates and insufficient mortar caused by the concrete segregation exist，the sonic wave will pass the more interfaces to cause decrease of the amplitude． In the low strong area with the less aggregate and more mortar，the wave velocity is low，but the amplitude is basically the same，even over high． If the defects of the pile diameter shrinking and the pile with mud ( sand) exist，the sonic velocity and amplitude in this area decrease obviously compared with the normal concrete． The defect of lots of airs stayed in the concrete of the of the up part of cast － in － place pile caused by lifting the tube too fast will not produce the obvious decrease of wave velocity，but it will produce the obvious reductions ( scattering) of the sonic wave energy and the receiving wave energy．

Research conclusions: As the simplest and the most commonly － used means，the temporary buttress can be used as the external auxiliary member of the steel truss arch for erecting the large span steel truss arch bridge，and by using it，the requirement of the linear adjustment for the steel truss arch can be met． By using active control technologies for controls of the vertical and horizontal shifts and the elevation，the arch and tie bar of the steel truss arch can be gathered up，the up and down operation of the whole steel truss arch bridge can be avoided and the measures for the closure adjustment of the steel truss arch bridge can be simplified．

Research conclusions: Based on the experiences and learning lessons about the bridge construction，the following proposals are made: ( 1) The bridge＇s design load bearing capacity should increase to make sure the bridge can stand up to the vehicles with the one － side loading and overloading． ( 2) The anti － dumping structure should be used to avoid the big careless omissions and defects． ( 3) The water － proof，draining and anti － seismic functions of the bridge should be improved to make the bridge more durable and more suitable for use．

Research conclusions: ( 1 ) To evaluate the danger of the large deformation is the important to prevent the large deformation of the high stress soft rock tunnel，and the evaluation content should include the three areas of the grading of the high stress soft rock tunnel，the deformation calculation and formulation of the responsibility for the failure of the primary support． ( 2 ) The release － constraint balancing method is used for releasing the ground stress by allowing deformation volume according to the features of the high stress soft rock tunnel and constraining the deformation by strengthening the primary support and lock pin，closing timely and dynamically reinforcing． The engineering application in the Lanzhou － Chongqing Railway shows this method is available for controlling the big deformation of the high stress soft rock tunnel．

Research conclusions:In the works of the deep bore hydro － geological survey and the ground stress testing for railway tunnel，there are following three sectors to determine the whether the tests accuracy can be enhanced and whether the tests succeed or not: (1) Selection of the testing section: Dividing the test section that meets the test requirement is the prerequisite for the successful test．(2) Determination of water stop position on the top and bottom ends: The effect of the water stop is crucial to the success of the test．(3) Determination of the thickness of the test section: Determination of the calculation thickness of the hydro － geologic test plays a decisive role in accuracy of the test data．

Research conclusions: From the research on the technologies for opening compartment and changing cutleries of the shield in the complex stratum，it is concluded the clay membrane with the average thickness above 5cm must cover the entire soil of the working face． The feeding and compressing compartment must be done step by step at the same time． The pressure should be reduced step by step． The pressure needed for forming the clay membrane should be bigger than the cutting pressure by 0． 5 bar．

Research conclusions: From the research on the shield overlapped tunnel with minimum clearance of 1． 6 m under effect of the train vibration load，it can be seen: ( 1 ) Under the effect of the dynamic load，the main stress of the soil embedded layer is mainly of the compression stress and it is in safety range under the effect of the train vibration load． ( 2) Under the effect of the dynamic load，the internal force of segment increases a little，but it is acceptable． ( 3) Under the effect of the dynamic load，the pulling force of the bolt on the completed block is the biggest among all hoop bolts of the segment of the upper tunnel，and it is necessary to reinforce the joint bolt because of the stress increase． ( 4) In order to ensure the safety of the railway traffic，the effective damping system should be installed for the up and down overlapped tunnel． This theoretical analysis can be as the theoretical analysis to the operation of the shield overlapped tunnel and as the reference to the similar works．

Research conclusions: ( 1) The Daping landslides are caused by the joint effects of the geological and hydrological conditions． ( 2 ) The interaction mechanisms between the tunnel excavation and anti － slide pile of slope can be expressed as follows: The anti － slide pile belongs to the passive support structure and the deformation of anti － slide pile is the embodiment of load bearing． The tunnel excavation process is a process of disturbing the landslide mass and also a process of bringing the anti － slide pile into play． ( 3) With the schemes of reinforcing landslide，tunnel excavation and tunnel supporting not only can the stability of landslide mass be guaranteed，but also can the security of tunnel construction be guaranteed．

Research conclusions: This paper studies the choice of the integral parameters at the different train speed with the Newmark method by building the simple catenary suspension mechanics model for the catenary and pantograph system． The result shows the simulation needs an vibration stabilization process when the model order is too low，and the result is satisfied when the model order is over 150． The time interval should be the half of the critical time interval for ensuring the simulation accuracy．

Research conclusions: The key of the underground barriers cleaning － up technology by artificial ground freezing method is the closure and quality of the frozen soil． After the frozen soil temperature is at － 10 ℃ ，the underground barriers was cleaned up successfully，and the heave and melt effect in the soil was controlled within ± 6mm． It provided an effective control of the construction safety risks，and reduce the effect to the construction environments，which gives a good benefit to other similar construction projects．

Research conclusions: The risk identification of subgrade project should be done from a specific engineering combining risk events with risk sources． The risk events must be found by the procedure of the project – sub item – branch item –construction process，as well as the risk sources at the same time from five aspects: the nature，geology，environment，design and construction，materials． The treatment of risk shall comply with the following basic principles: using the economic and reasonable technical and control measures to prevent the subgrade risks，lessening or reducing loss caused by risks and avoiding collapse，sliding，which is difficult to restore and affects normal function． subgrade risk should be controlled from its root． In the planning and design stage，the identified risk that is likely to cause the delay of schedule or cause heavy loss should be remedied by adjusting line plane or profile，adopting substitute program or other optimizing program to avert or reduce risks． Economic and rational technical measures are needed to guard against the risks in subgrade projects．

Research conclusions: ( 1) It is feasible to analysis the factors of the sliding risk of slope，using analytic hierarchy process combined with expert scoring method． ( 2) In the criterion layer，the influence of technological factors is greater． ( 3) For the technology risk，how to design reasonably and reduce the sliding risk for the slope of embankment is very important． And construction quality only take second place． ( 4) For sliding risk of embankment slope，control the risk of design and construction is the key．

Research conclusions: The risk management system composed of the analytic hierarchy process method，expert investigation method and fuzzy evaluation method has the characteristics of the distinct levels，clear steps and detailed analysis． The analysis results accord with the real situation，so it is reliable． The natural risk，environmental risk， construction risk and design risk have the big influence on the risk assessment results of the expansive soil nailing wall． Therefore，on fully consideration of natural and environmental factors，the reasonable design and strictly construction according to the design are the key points to reduce the collapse risk of the expansive soil nailing wall．

Research conclusions: ( 1) It is necessary to control the safety risk to the existing and under － construction station buildings，and the corresponding measures should be taken for eliminating the existing hidden danger in safety． ( 2) The building designer should comprehensively control the safety risk in design to timely find out the hidden danger and provide the guidance and technical support to dealing with the safety accident once the safety accident happens． ( 3) The relations between the the safety risk and the development and the profits increase should be well dealt with．

Research conclusions: Compared with the all marketing expenditures born by developer of real estate alone，the unilization ratio of the marketing expenditure is higher under the condition of the marketing expenditure born by the both developer and sales agents and the profits of the both marketing supply chain and sales agent are higher． In addition，the optimized marketing expenditure is positively correlated with the marketing capabilities of the both developer and sales agent． Nevertheless，the optimized proportion of the expenditure shared by the sales agent is negatively correlated with the marketing capability of the developer and positively correlated with the marketing capability of the sales agent．