Influence of the groundwater level on the bearing capacity of shallow foundations on the rock mass

Abstract

The presence of the groundwater level (GWL) at the rock mass may significantly affect the mechanical behavior, and consequently the bearing capacity. The water particularly modifies two aspects that influence the bearing capacity: the submerged unit weight and the overall geotechnical quality of the rock mass, because water circulation tends to clean and open the joints. This paper is a study of the influence groundwater level has on the ultimate bearing capacity of shallow foundations on the rock mass. The calculations were developed using the finite difference method. The numerical results included three possible locations of groundwater level: at the foundation level, at a depth equal to a quarter of the footing width from the foundation level, and inexistent location. The analysis was based on a sensitivity study with four parameters: foundation width, rock mass type (mi), uniaxial compressive strength, and geological strength index. Included in the analysis was the influence of the self-weight of the material on the bearing capacity and the critical depth where the GWL no longer affected the bearing capacity. Finally, a simple approximation of the solution estimated in this study is suggested for practical purposes.

Assessment of the Bearing Capacity of Bridge Foundation on Rock Masses

“…The use of numerical methods and the progress of computational geomechanics have allowed access to the practical calculation of more sophisticated bearing capacity problems involving: (a) anisotropic rock masses (in [26] a solution in some simple cases is indicated and in [27] another solution for piles in rock masses is developed but in both cases the solutions do not depend on the width); (b) the presence of a water table in the rock [28], the shape of the foundation in rock masses [29], and roughness of the rock [30] where the results do not incorporate the size foundation; (c) the interaction with other structural elements such as tunnels [31] where it is not possible to know the influence of the dimension of the foundation; (d) bilayer rock under the footing [32] that does not depend on the width of footing; (e) the dynamic response of the foundation that offer solutions that do not depend on the geometric characteristics of the analyzed foundation (in [33] and [34] cases without self-weight of the ground are considered, [35] a particular application is considered but it is not possible to obtain the influence of the foundation size). In addition, new calculation methods have been developed in the study of piloted foundations in non-cohesive soil [36], cohesive soil [37], and considering inclined load [38] but using a linear failure criterion not representative of the behavior of a rock masses.…”

The Effect of the Water Table on the Bearing Capacity of a Shallow Foundation

“…Alencar et al [23] studied the influence of different groundwater levels on the ultimate bearing capacity of shallow rock foundations and how the groundwater level no longer affects the bearing capacity by using the finite difference method, respectively assessing the width of the foundation, the type of rock mass, the uniaxial compressive strength, and the geological strength index. Safarzadeh and Aminfar [24] studied the effect of the groundwater table drop on the bearing capacity of shallow square model footings on compact sand by conducting plate load tests and finite element software OptumG2 under different groundwater table conditions.…”