عنوان مقاله [English]
Underground box culverts have applied to facilitate people's standard of living in various ways. Design and construction of these conduits request for determination of exerted pressure due to the soil and embankment weight above. Where, the applied load is large and culverts have been installed under high embankment, applied pressure become more significant. Therefore, reduction and control of the earth load on culverts, is of importance concern. Various methods and theories have been proposed to reduce the applied earth load on these underground structures. Among these, two methods have been commonly used namely, Trench Installation (TI) and Induced Trench Installation (ITI). For TI method, where the culvert is placed in a narrow trench, the deformable soil tends to settle down, while the adjacent trench walls act to hold the soil in place due to shearing stresses along the interfaces. This leads to a load transfer 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 above the buried culvert to induced positive arching, thus reducing the applied vertical pressure on culvert crown. Meanwhile, some deficiencies have addressed by researchers in each method. Trench Installation in comparison with Induced trench Installation, transfers larger earth load to culvert roof. Also, development of positive arching directly above of culvert roof, transfer more vertical stresses to adjacent soil columns, leading the larger horizontal stresses applied to buried culvert walls. In this study, 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 which called Trenched Induced Trench Installation (TITI). Firstly, the transferred pressure to the culvert under the weight of soil and surface pressure, has been validated using numerical analyses and compared with analytical equations which 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 roof, side walls 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 side walls and trench walls, also can control the pressure applied on the culvert side walls.