Effects of frictional forces acting on sidewalls of buried box culverts

Abstract

SUMMARYThe effects of frictional forces acting on the sidewalls of buried box culverts are presented as determined with finite element method (FEM) and detailed soil modelling. The possibility of reducing earth pressure on deeply buried concrete box culverts by the imperfect trench installation (ITI) method has been contemplated during the last several decades. There have been limited research results published primarily regarding the qualitative aspect of load reduction in ITIs. It was found during the course of this study that significant frictional forces develop along the sidewalls of box culverts and adjacent sidefills in ITIs. Current American Association of State Highway and Transportation Officials provisions do not consider these frictional forces, but they cannot be neglected in ITIs, as their effect is dominant. An optimum geometry for the soft zone in ITIs is presented to maximize earth load reductions. The soil-structure interaction at the box culvert-soil interface was found to have a significant effect on total earth pressure acting on the bottom slab. Predictor equations for earth load reduction rates were formulated for ITIs incorporating the optimum soft zone geometry based on the FEM.

Static soil culvert interaction the effect of box culvert geometric configurations and soil properties

“…Kang et al [9] investigated numerically the side friction of a box culvert under different soil fill heights, considering soil properties representative of compacted and uncompacted side fills for yielding and unyielding foundation soils. The F e values were established as a function of the culvert (H/Bc) ratio.…”

“…Bennett et al [4] AASHTO [10] Compacted Sidefill AASHTO [10] Uncompacted Sidefill CHBDC [11] Installation B1 CHBDC [11] Installation B2 Kang et al [9] Compacted Sidefill Kang et al [9] Uncompacted Sidefill Spangler [15] Sato et al [16] James et al [17] Tadros et al [7] Dasgupta et al [14] Vasleastad et al [18] Yang [19] Bennett et al [4] Pimentel et al [20] Fig. 1.…”

“…This behavior was observed in the thin culvert, while the thick culvert showed a uniform increase in the horizontal soil pressure with depth. Several researchers proposed soil culvert interaction factors for different soil heights above the culvert (e.g., [4,9,7,8]). Fig.…”

“…1. Comparison between different methods for calculating the soil structure interaction factors F e as a function of H/Bc [4,7,[9][10][11][14][15][16][17][18][19][20]. [7] Silty Clay Tadros et al [7] Silty Sand Girdler [21] Russ [22] Sato et al [16] James et al [17] Tadros et al [7] Dasgupta et al [14] Vasleastad et al [18] Yang [19] Bennet et al [4] Pimentel et al [20] Spangler [15] focussed on the response of the box culverts to the self-weight of sand.…”

“…et al[4] and Kang et al[9] as a function of H/Bc, whileFig. 19compares the results with the relationship proposed by Tadros et al[7] and Kim and Yoo[8] as a function of H. The relationship proposed by Kang et al[9] for compacted and uncompacted side fills shows a reduction in the F e values as the H/Bc ratio increases, while the relationship suggested by Bennett et al[4] shows an increase in the F e values for H/Bc P 2.42, and very small increase afterward.…”