Bearing Capacity of Footings on Rock Masses Using Flow Laws

The influence of the non-associative flow law on the bearing capacity of shallow foundations on rock masses is, in general, a subject that is not discussed in the field of rock mechanics. The calculation methods of bearing capacity usually do not define which flow law is adopted and, in some methods, the associative flow rule is assumed without knowing how that hypothesis influences the bearing capacity of the rock mass. In this paper, the study of the influence of the dilatancy angle on the bearing capacity of shallow foundations on rock masses is presented. The variation of the bearing capacity with the associative flow law and the non-associative flow law with zero dilatancy angle is studied using the finite difference method and by considering the influence of the self-weight of rock material. The calculations confirm the great influence of the flow law on the bearing capacity and a correction coefficient is proposed, which makes it possible to estimate the variation of the bearing capacity of the rock mass in terms of the function of the flow law for the hypothesis of weightless rock masses.

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Assessment of the Bearing Capacity of Bridge Foundation on Rock Masses

Applied Sciences ◽

10.3390/app112412068 ◽

2021 ◽

Vol 11 (24) ◽

pp. 12068

Author(s):

Ana Alencar ◽

Rubén Galindo ◽

Claudio Olalla Marañón

Keyword(s):

Rock Mass ◽

Bearing Capacity ◽

Failure Criteria ◽

Shallow Foundation ◽

The Self ◽

Geological Strength Index ◽

Flow Rule ◽

Rock Masses ◽

Analytical Results ◽

Bridge Foundation

This paper aims to study the bearing capacity of a shallow foundation on rock mass, considering the most usual bridge footing width and adopting a Hoek–Brown material. The dimension of the foundation has been shown to be very significant in soils with linear failure criteria (Mohr–Coulomb envelope), and its study is necessary in the case of non-linear failure criteria, typical of rock masses. Analytical solutions do not allow incorporating this effect. A parametric study by a finite difference method was carried out, studying a wide variety of rock mass through sensitivity analysis of three geotechnical parameters: geological origin of the rock mass (mi), uniaxial compressive strength, and geological strength index. The results obtained by the numerical solution for the Hoek–Brown failure criterion were compared with the analytical results by adopting the classical hypotheses of plane strain conditions, associated flow rule, and weightless rock mass. The variation of the numerical bearing capacity due to the consideration of the self-weight of the rock mass was also analyzed since its influence is conditioned by the volume of ground mobilized and therefore by the width of the foundation. Considering the similarities observed between the numerical and analytical results, a correlation factor function of the self-weight is proposed. It can be used in conjunction with the analytical method, to estimate in a semi-analytical way the bearing capacity of a bridge foundation.

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An accessible calculation method of the bearing capacity of shallow foundations on anisotropic rock masses

Computers and Geotechnics ◽

10.1016/j.compgeo.2020.103939 ◽

2021 ◽

Vol 131 ◽

pp. 103939

Author(s):

R.A. Galindo ◽

M.A. Millán

Keyword(s):

Bearing Capacity ◽

Calculation Method ◽

Shallow Foundations ◽

Rock Masses ◽

Anisotropic Rock

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

Bulletin of Engineering Geology and the Environment ◽

10.1007/s10064-021-02368-2 ◽

2021 ◽

Author(s):

Ana Alencar ◽

Rubén Galindo ◽

Svetlana Melentijevic

Keyword(s):

Rock Mass ◽

Bearing Capacity ◽

Groundwater Level ◽

Sensitivity Study ◽

Shallow Foundations ◽

Unit Weight ◽

Geological Strength Index ◽

Strength Index ◽

Mass Type

AbstractThe 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.

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Application of Artificial Neural Networks for Predicting the Bearing Capacity of Shallow Foundations on Rock Masses

Rock Mechanics and Rock Engineering ◽

10.1007/s00603-021-02549-1 ◽

2021 ◽

Author(s):

M. A. Millán ◽

R. Galindo ◽

A. Alencar

Keyword(s):

Bearing Capacity ◽

Analytical Solutions ◽

Shear Failure ◽

Numerical Models ◽

Computational Effort ◽

Shallow Foundations ◽

Geological Strength Index ◽

Rock Masses ◽

Ann Model ◽

Artificial Neural

AbstractCalculation of the bearing capacity of shallow foundations on rock masses is usually addressed either using empirical equations, analytical solutions, or numerical models. While the empirical laws are limited to the particular conditions and local geology of the data and the application of analytical solutions is complex and limited by its simplified assumptions, numerical models offer a reliable solution for the task but require more computational effort. This research presents an artificial neural network (ANN) solution to predict the bearing capacity due to general shear failure more simply and straightforwardly, obtained from FLAC numerical calculations based on the Hoek and Brown criterion, reproducing more realistic configurations than those offered by empirical or analytical solutions. The inputs included in the proposed ANN are rock type, uniaxial compressive strength, geological strength index, foundation width, dilatancy, bidimensional or axisymmetric problem, the roughness of the foundation-rock contact, and consideration or not of the self-weight of the rock mass. The predictions from the ANN model are in very good agreement with the numerical results, proving that it can be successfully employed to provide a very accurate assessment of the bearing capacity in a simpler and more accessible way than the existing methods.

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Influence of Natural Cavities on the Design of Shallow Foundations

Applied Sciences ◽

10.3390/app10031119 ◽

2020 ◽

Vol 10 (3) ◽

pp. 1119

Author(s):

Jesús Luis Benito Olmeda ◽

Javier Moreno Robles ◽

Eugenio Sanz Pérez ◽

Claudio Olalla Marañón

Keyword(s):

Rock Mass ◽

Bearing Capacity ◽

Ultimate Bearing Capacity ◽

Shallow Foundation ◽

Rock Masses ◽

Volcanic Origin ◽

Rock Types ◽

Geometric Configurations ◽

Relative Eccentricity ◽

Decisive Parameter

When inner cavities of significant dimensions exist in natural rocks, problems arise when a shallow foundation for a building, bridge or other structure is builtonthem. Thus, taking one of the most representative cavity geometries in nature, the ellipsoidal horizontal shape, the main objective of this study is to obtain the ultimate bearing capacity of the foundation with cavities of different sizes and positions, on rock masses with different strengths and deformation characteristics. The study focuses on natural rocks of karst origin (in limestones, dolomites or gypsums) and of volcanic origin. The ultimate bearing capacity is determined relative to a situation without the existence of the cavity for different cavern positions and sizes, rock types (mi), strengths (UCS), and states (GSI) of the rock mass. The results showed that the most decisive parameter is the relative eccentricity. The influence of the rock type (Hoek’s parameter mi) is, for practical purposes, negligible (lower than 10%). The strength and condition of the rock mass (parameters UCS and GSI) have relatively little influence on the results obtained. This study aims to provide a simple design criteria for universal use, with different geometric configurations and qualities of rock masses that can be used directly without the need for sophisticated calculations by the designer.

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