上海地铁维护保障有限公司

At present, light-disturbance grouting technology has been widely applied in controlling and rehabilitating the transverse deformation of existing shield tunnels. However, there is a lack of corresponding research on the stratigraphic mechanical response during the minor-disturbance grouting process. This paper relies on a case study of transverse deformation rehabilitation of shield tunnels treated with minor-disturbance grouting in Shanghai. A lining ring is selected as a test ring at the site, with pressure sensors installed on both sides of the grouting hole to monitor the variations in earth pressure and pore water pressure. Based on this, the variations of the additional earth pressure, excess pore water pressure, and effective stress near the grouting hole during the grouting process are analyzed. Furthermore, the mechanical response of the ground at the test location induced by the grouting process of three adjacent grouting holes is further analyzed. On this basis, the slurry distribution coefficients in the existing grouting efficiency equations are corrected in conjunction with the additional earth pressure variations during grouting, and this provided a new idea for quantitatively characterizing the uncertainty of the grouting body in a two-dimensional plane and the design of grouting parameters in engineering practice.

[Objective] In evaluating the service life extension of urban rail transit trains, economic calculation serves as a key basis for decision-making and plays a critical role in determining whether to carry out life extension and associated upgrade. Therefore, it is essential to study the economic viability in urban rail transit train life extension based on whole life-cycle cost. [Method] Through calculating the whole life-cycle cost for urban rail transit trains, an economic evaluation method for train service life extension is proposed. Urban rail transit train life cycle is divided into four stages: procurement, operation, maintenance, and recycling/disposal. The costs for each stage are calculated separately, incorporating inflation factors and special expenses such as mid-term overhauls, which enables targeted evaluation for factors like interest rate, inflation, and refurbishment costs under service life extension scenarios. An empirical analysis and parameter study are conducted using a typical case，and multi-dimensional calculation is carried out for two scenarios: retirement at the standard 30-year service life and at the extended 45-year service life. [Result & Conclusion] When excluding the factors such as interest rates, inflation, and residual value at disposal, upgrade and procurement costs are the decisive factors influencing the economic feasibility of service life extension. The higher the procurement cost and the lower the cost, the greater the economic advantage of extending service life. Though interest rate factors significantly affect the overall life-cycle cost of the train, their impact on the economic viability of train delayed upgrade is relatively minor. Inflation factors have a substantial effect on the economics of train life extension; as the inflation rate increases, the cost advantage of life extension diminishes rapidly. When the inflation rate reaches 1.5%, extending train service through upgrade will eliminate any economic advantages.

[Objective]Arcing problems frequently occur in Shanghai rail transit vehicle bases,which not only damage the appearance and structure of the rails and wheels,but also affect train operation safety.Therefore,it is necessary to analyze ar-cing problems in the vehicle base,identify the cause of arcing,and then propose solutions.[Method]In the case of catenary power outage in the vehicle base,before and after disconnec-ting the unidirectional conduction devices on the entrance/exit lines,and when the mainline train enters and exits the station near the vehicle base,by detecting the current between the ma-intenance platform railing and the car body,and the current passing through the unidirectional conduction devices on the en-trance/exit lines,causes for the parking garage maintenance platform railing arcing are deeply analyzed.After adjusting the exiting line power supply mode,when there is no train leaving the depot and the outbound car is driving to the main line via the exit line,the voltage at both ends of the insulating joint,the voltage of the mainline rail to the ground,and the voltage of the yard rail to the ground are measured respectively,and causes for the insulation joint arcing when the wheel passing through the entrance/exit lines are deeply analyzed.Solutions are proposed for the cause of arcing.The application effect of using an intelligent conduction device instead of the unidirec-tional conduction device is emphatically verified.[Result &Conclusion]Arcing in the maintenance platform railing is caused by the stray current leaking from the mainline rail to the parking lot.Arcing in the base entrance/exit lines insulation joint is caused by the increase of rail return current and the in-crease of insulation joint pressure difference due to poor current return.In addition,since the arc extinguishing device thyristor in the unidirectional conduction device is affected by the mini-mum holding current,the turn-on voltage and other characteris-tics,both insulation joint ends cannot achieve the effect of me-tallic electrical connection,thus resulting in unsatisfactory arc extinguishing effect.The actual application effect shows that the intelligent conduction device can effectively block the stray current path,inhibit the stray current from flowing into the ve-hicle base,ensure the smooth return flow,thereby reducing the arcing occurrence in the vehicle base.

[Objective]In order to strengthen the status ma-nagement of urban rail transit line sections,it is necessary to predict the overall deterioration trend of the gauge in space.[Method]CEEMD(complementary ensemble empirical mode decomposition)theory is introduced to extract the IMF(intrin-sic mode function)of the geometric alignment of the track sec-tion.The PSO(particle swarm optimization)algorithm is uti-lized to optimize the SVR(support vector regression machine)to train and test the extracted data after calibrating the optimal parameters of the prediction model.Thus,the CEEMD-PSO-SVR prediction model is constructed.The prediction model is tested with 1,128 sets of track inspection sample data within the upward track section from K1 2+134 to K1 5+743 on Shanghai Metro Line 16.[Result & Conclusion]Compared with the PSO-SVR model and the ARIMA(autoregressive in-tegrated moving average)model,the CEEMD-PSO-SVR pre-diction model has advantages in three performance evaluation indicators,namely root mean square error,mean absolute er-ror,and absolute value of mean relative error.

In order to study the load-carrying capacity and ductility behavior of steel pipe-section piers with T-shaped stiffeners subjected to a constant vertical load and cyclic lateral loads,the accuracy of the employed finite element analytical method is firstly verified by comparing the analytical results with the existing test results.After that,the effects of normalized radius-to-thickness ratio,normalized slenderness ratio of the pier,normalized slenderness ratio of the longitudinal stiffener and axial compression ratio on the pier with eight T-shaped stiffeners are investigated through parametric study.Finally,based on the parametric analytical results,the formulas are proposed to predict the load-carrying capacity and ductility of the piers.The research results show that with the increase of normalized radius-to-thickness ratio,normalized slenderness ratio of the pier,normalized slenderness ratio of the longitudinal stiffener and axial compression ratio,the peak point of the lateral load-displacement skeleton curves at the top of the piers gradually decreases,and the downward trend becomes faster at the post-peak stage,which indicates that the load-carrying capacity and ductility behavior of the steel piers gradually decrease.By reducing the normalized radius-to-thickness ratio,normalized slenderness ratio of the pier,normalized slenderness ratio of the stiffener and axial compression ratio,the ultimate bearing capacity and ductility of steel bridge piers can be significantly improved.