V–H–M seismic capacity envelopes of strip foundations on slopes for capacity design of structure-foundation system

Abstract

The columns and the supporting foundations are invariably subjected to the interacting axial force, V, shear force, H and moment M. It is quite common to consider the interaction of these forces in design of structural components, but the available standards and literature usually ignore the effect of interaction in case of foundations on slopes. Further, very little information is available about seismic capacity of foundations located on slopes. This article presents a numerical study on evaluation of the V-H-M capacity envelopes of strip foundations placed on top and face of slopes and subjected to earthquake action, with an objective of enabling a direct comparison with the capacity of the supported columns. Nonlinear 2D finite element limit analyses (FELA) are performed for this purpose. Modified 'Probe' analyses are carried out for two representative c- soil slopes to develop the V-H-M capacity envelopes. The computed capacity envelopes are compared with their counterparts on flat ground. The characteristic features of the capacity envelopes are identified and explained considering the failure patterns under different combinations of V, H and M. A comparison of the capacity envelopes of counterpart foundations on flat ground and of columns is presented to highlight the relative hierarchy of strength of columns and foundations of a typical building on slope.

Undrained seismic bearing capacity of strip footings horizontally embedded in two-layered slopes

“…Considering that the variation of c u1 /(gB) only effects the deformation state and rarely has influence on the variation trend of bearing capacity (Xiao et al, 2018), the value of c u1 /(gB) is set as 4. With two fixed parameters, the undrained seismic bearing capacity can be simplified as follows: In this study, two slopes with inclination angle of 20°and 30°are, respectively, adopted to represent the gentle slope and steep slope (Raj et al, 2019a(Raj et al, , 2019b. To investigate the influence of layered soil on bearing capacity, D 1 /B is set as 4 (D 2 /B = 6, D/B = 5) to represent the situation that the strip footing located in the bottom soil layer, whereas D 1 /B is set as 6 (D 2 /B = 4, D/B = 5) to represent the situation that the strip footing located in the top layer.…”

“…In this study, two slopes with inclination angle of 20° and 30° are, respectively, adopted to represent the gentle slope and steep slope (Raj et al, 2019a, 2019b). To investigate the influence of layered soil on bearing capacity, D 1 /B is set as 4 ( D 2 /B = 6, D / B = 5) to represent the situation that the strip footing located in the bottom soil layer, whereas D 1 /B is set as 6 ( D 2 /B = 4, D / B = 5) to represent the situation that the strip footing located in the top layer.…”

“…Considering that the variation of c u1 /(gB) only effects the deformation state and rarely has influence on the variation trend of bearing capacity (Xiao et al, 2018), the value of c u1 /(gB) is set as 4. With two fixed parameters, the undrained seismic bearing capacity can be simplified as follows: In this study, two slopes with inclination angle of 20°and 30°are, respectively, adopted to represent the gentle slope and steep slope (Raj et al, 2019a(Raj et al, , 2019b As mentioned above, pseudostatic approach is used to obtain the seismic bearing capacity, namely applying a horizontal seismic coefficient k h in both soils and footings to simulate the seismic action. Previous study (Cinicioglu and Erkli, 2018) has proven that when k h .…”

“…Keshavarz et al (2019) adopted FELA to predict the seismic bearing capacity of strip footings located on the top of slopes. More recently, the issue has been further extended to the case of the sloping ground (Raj et al, 2018(Raj et al, , 2019a(Raj et al, , 2019b.…”

Estimating the Uplift Bearing Capacity of Belled Piers Adjacent to Sloping Ground by Numerical Modeling Based on Field Tests

“…Many theoretical, numerical, and experimental results have been proposed to determine the load-bearing capacity of the footings adjacent to slopes or resting on slope surfaces [2][3][4][5][6][7][8][9]. Based on the results of slope model footing tests, Castelli and Lentini [2,10] studied the influence of the slope distance on the bearing capacity of the foundation and determined the modified bearing capacity factors.…”