In this paper, the computational design of Box culverts are compared using Kleinlogel’s formulas and three-dimensional models based on Winkler and Modified Vlasov Foundation (MVF) by Radial Point Interpolation method (RPIM). In order to extend the RPIM to the study of Box culverts, a method of decomposition is made by subdomain and creation of a fictitious rotation. Similar results are observed between the RPIM_Winkler and STAAD PRO (FEM software), with fewer nodes in the case study. Kleinlogel’s formulas or the Winkler model gives a maximal increase in stresses at the middle of the raft of 5% and 12 times increased displacement. Finally, it emerges that for the same type of soil and a single structure, the reaction and shear modulus of the soil is highly depends on the distribution of loads on the structure.

one of the most important issues in operation of high-speed railway tracks is avoiding to sudden variation of the track stiffness. culverts and bridges are common areas which this problem is occurred along the railway lines.One of the method for applying the gradual variation of the track stiffness in these areas is using the approach slabs in transition zone. Therefore, in this research it has attempted to study this problem using numericalsimulation. In this regard, a typical culvert of Tehran-Qom-Esfahan high speed railway line with 6.6 m length was simulated. Then for studying the effect of transition zones, an approach slab includes of three parts with 6mlength and various thicknesses simulated by FE model. In this model the ballasted track and its components such as railpads, sleepers, ballast and subgrade were modeled as lumped mass-dashpot-spring systems and the rails, approach slabs and culvert were modeled by Euler-Bernoulli beamelements. Then the dynamic behavior of the transition zone investigated under the passing of the moving loads same as the axle loads of the ICE high speed train. In this matter a series of sensitivity analyses were carriedout on some parameters such as vehicle speed, approach slab thickness as well as damping and stiffness of track. Consequently, the achieved results show that the increasing of damping and stiffness of the track cause to the ballast forces increased and in other side it causes to the acceleration and settlement of the ballasted track and the approach slabs decreased. These aforementioned effects are more obvious in damping values higher than 200kN.sec/m and the track stiffness values in the range of 120 MN/m to 180MN/m. Moreover, it was understood that increasing the approach slabsthickness has remarkable effect on improving the dynamic behavior of the transition zone especially in speeds more than 340 km/hr.

Local scour at the culvert outlet is common event. In this study the effect of different angles of wing walls flare on scour in hydraulic conditions for type 1 and 4 flows at downstream of circular and Box culvert investigated. Wing walls flare 15, 30, 45, 60 and 75-degrees to the outlet centerline were considered in this study. Result showed 15-degree flare wing walls reduced scour depth, scour length and mound height. So, 15-degree flare wing wall in Box culvert and type1 flow reduced scour equal 35. 3% to the control test. Also, 30-degree flare wing walls in Box culvert and type1 flow has shown a good performance in reducing scour depth equal 46%. Wing walls flare angle 60 and 75-degree, did not have good performance in reducing scour depth at downstream of culverts. In type 1 flow, scour can be reduced by using of wing walls with any angles. In type4 flow, only 15-degree wing walls flare reduced maximum scour depth equal 30% in circular culvert and 10% in Box culvert. Also, the dimensions of the scour hole on downstream of the circular culvert is more than Box culvert. So, in the circular culvert and type 1, scour depth increased equal 35% compared to Box culvert and it was observed equal 95% in type-4 flow. The dimensions of the scour hole in type 1 flow is higher than type 4 at all angles, while the mound height in type 4 is higher than type 1 flow.

culverts are important structures to convey water under roads and rail roads. Blockage or clogging of drainage channels by woody debris is one of the serious problems in the design and operation of road culverts that has not been studied well. In this laboratory study, the entrance blockage of a Box culvert model due to the accumulation of woody floating objects is investigated. Also, the influence of hydraulic and geometric parameters such as flow velocity, elapsed time_ and the entrance flow depth in the culvert were studied. Laboratory observations showed that the entrance blockage increases as the interval time between the arrivals of woody floating objects reduces. The maximum blockage occurred in the falling limb of the hydrograph and the last time step. Using the experimental results and dimensional analysis, some dimensionless parameters are reported and their variations against the culvert entrance blockage are evaluated. The most effective parameters are identified using statistical analysis with SPSS software. Finally, a non-dimensional linear relationship is derived to determine the percentage of blockage as a function of the effective parameters.

Underground Box culverts have been applied to facilitate people's living standard in various ways including municipal sewer lines, water mains, gas and oil lines, electric and telecommunication conduits, and pedestrian and subway tunnels. Design and construction of these conduits demand determining exerted pressure due to the soil and embankment weight above. Several ways have been developed for buried culverts and calculating the soil earth to which the buried culvert is subjected to. Accordingly, the applied load is large and culverts are installed under high embankment; applied pressure becomes more significant. Therefore, the reduction and control of the earth load on culverts is of importance. To date, various methods and theories have been proposed to reduce the applied earth load on these underground structures. Among these, two methods are commonly used: Trench Installation (TI) and Induced Trench Installation (ITI). For the TI method, where the culvert is placed in a narrow trench, the deformable soil tends to settle down, while the adjacent trench walls hold the soil in place due to shearing stresses along the interfaces. This leads to the transfer of load from the fill to the trench walls developing soil arching, hence reducing the vertical pressure transfer to buried Box culvert. Another method, ITI, is a construction technique employed to reduce the vertical pressure on buried structure, in which a layer of compressible material is placed directly on the buried culvert to induce positive arching thus reducing the applied vertical pressure on culvert crown. Meanwhile, researchers have addressed some deficiencies in each method. Trench Installation in comparison with Induced trench Installation transfers larger earth load to culvert roof. In addition, the development of positive arching directly above the culvert roof transfers more vertical stresses to adjacent soil columns, leading to larger horizontal stresses applied to buried culvert walls. In this study, by taking benefits of these two common methods, an installation method has been proposed in which the culvert is installed in a trench with a layer of deformable material placed above the Box culvert roof, called Trenched Induced Trench Installation (TITI). Firstly, the pressure transferred to the culvert under the weight of soil and surface pressure has been validated using numerical analyses compared with analytical equations that predict the applied pressure. Then, two-dimensional finite element analyses have been performed to explore the effect of various factors on the applied pressure on the roof, sidewalls, and bottom of buried Box culvert in TITI method. Results show that soil arching reduces the earth pressure on roof and arching developed between Box sidewalls and trench walls; the pressure applied on the culvert side walls can be controlled.

Scouring is a two phase flow and has been experimentally studied. culverts are used to transfer the flow from one side of roads or banks to the other side. This experimental work is conducted to study the scouring down stream of a pipe culvert. The scour hole properties is a function of various parameters like: discharge, height of drop, tail water depth, diameter of the pipe and sediment size. In this study, variations of scour hole dimensions, and changes of the ridge caused by scouring were correlated to: pipe diameter, drop height, dens metric Froude number and tail water depth. It was observed that depth and width of the scour hole and the height of the ridge increase with the increasing the pipe diameter, but the length of scour hole decrease. Moreover, it was observed that increasing the tail water depth, width and depth of the scour hole decrease, but the length of scour hole and height of the ridge increases. In addition, with increasing the drop height, depth and width of scour hole and height of the ridge increase, but length of scouring hole decrease. The ratio of the scour hole dimensions and the height of the ridge to the drop height was related to Tw/D (tail water to pipe diameter ratio), SN (dens metric ّFroude number) and Hc/D (drop height to pipe diameter ratio).

Introduction: culverts are common structures for runoff drainage system in the design and construction of roads and railways, in both urban and rural areas. Due to the nature of runoff flow, large amount of sediments, foliage, urban waste and debris materials may accumulate in the entrance of culverts, particularly in flood events. Blockage in the culvert’ s entrance can result in a significant increase in flood risk, through elevated flood levels and diverted flow paths through the urban or rural areas (Rigby et al., 2002). Sudden blockage in a runoff system is also one of the common problems. The study of culvert’ s blockage would be useful in the prediction and prevention of flood hazard in the vicinity of drainage systems. Current study deals with this problem in Box culverts. Blockage effects on the upstream water level were investigated using both experimental and numerical modeling. The FLOW-3D model was chosen, because the sufficiency of this model for such flow conditions was already reported by several studies such as Abad et al. (2008), Salamat Ravandi (2011) and Gunal et al. (2019). Methodology: Experimental tests were conducted in Hydraulic Laboratory of Water Engineering Department in Bu Ali Sina University, Hamedan, Iran. The Box culvert models made of glass and smooth water pipes used as circular culvert models. The experimental setup includes a glass wall flume with 10m length, 0. 5m width and 0. 6m deep. Rectangular plates in different sizes were used in order to make sudden blockage into the culverts. An extensive experiment tests was conducted under different flow condition and blockage scenarios, and 21 experimental data sets were provided. The FLOW-3D model, Version 11. 3, was performed on the main server of Water Institute at the University of Tehran, and adapted to the experimental data sets from this study. The stability and sensitivity of this model have been tested according to: mesh cell size, simulation time step, turbulent model, and culvert hydraulic characteristics such as wall roughness. The simulation convergence was achieved with an efficient simulation time step of 80 seconds. Three different mesh blocks were used for pre-simulation cases, and a block in block with 1. 0 cm and 0. 5 cm mesh cell sizes were chosen as the best meshing scenario. The RNG was found to be an appropriate turbulence model. The slope of culvert barrel was changed from horizontal to 0. 005 in the flow direction, and the roughness coefficient modified from 0. 00085 m to 0. 001 m in the culvert barrel. The relative error of simulated water levels and discharge for calibrated model were to be in the order of acceptance ranges, and the simulation FLOW-3D model was adjusted as an efficient and reliable tool. The FLOW-3D model was then calibrated and verified using the experimental data sets, and was used to simulate different flow conditions into the culverts, under different entranceblockage scenarios. Results and discussion: Effect of the inlet blockage on upstream water level was tested for three flow rates (the design discharge of 27. 5 lit/s, and two lower discharges of 10. 5 lit/s and 16. 5 lit/s), in four different sizes of inlet blockage (B). Simulation results showed a good agreement in upstream backwater level in all cases. In the case of flow with 16. 5 lit/s, upstream water level raised from 28. 5 cm in non-blocked inlet to 31. 4, 34. 2 and 38. 5 cm in presence of 20%, 40% and 60% blocked inlet area, respectively. The rate of the upstream water level increase (DHu) against the reduced inlet area (1-B) represents a higher rate for discharges smaller than the culvert-design discharge. The evaluated equations for upstream water level enhancement were: 𝐷 𝐻 𝑢 =-0. 48(1-B)+45. 089 (1) 𝐷 𝐻 𝑢 =-0. 82(1-B)+75. 663 (2) in which, Eq. (1) is for design discharge and Eq. (2) for the smaller discharges. Blockage has been affected flow in the barrel and in the downstream of the culvert. Investigation of turbulent characteristics and shear velocity values in both the barrel and downstream indicated the impact of blocked inlet. Turbulent energy of flow in the 60% blocked-inlet area was 5 times greater than that of non-blocked inlet for the design discharge. Also shear velocity in the same blockage situation increased by 2 times in downstream which results in a greater scouring power of the flow downstream. Sorourian et al. (2015) reported this phenomenon with even higher scour downstream of blocked culverts. Maximum value of shear velocity increased with the increase level of blockage in the all flow condition, however in the design discharge it seems to be constant for blockages greater than 40%. Conclusion: The FLOW-3D model was calibrated and validated to simulate the flow into the culverts. Influence of inlet obstruction on the upstream water level and flow characteristics into the barrel and downstream of the culvert was investigated. The results show a linear increase in the upstream water level by decreasing the percentage of culvert inlet. The upstream water level for the design discharge was lower than the other tested discharges. Changes in turbulent flow properties and shear velocity inside the barrel and downstream were also investigated in the presence of obstruction. Shear velocity increased 3 times in the presence of 80% blockage for 10. 5 lit/s. and for the design discharge (27. 5 lit/s) with 60% inlet blockage increased 2 times. The turbulence energy for the design discharge has also increased by about 5 times. The present results confirm the previous studies on the effect of the culvert inlet obstruction on the geometry of the scour hole downstream of culverts.