scholarly journals Assessment of the Bearing Capacity of Bridge Foundation on Rock Masses

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.

scholarly journals Influence of Natural Cavities on the Design of Shallow Foundations

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.

scholarly journals Bearing Capacity of Footings on Rock Masses Using Flow Laws

2021 ◽  
Vol 11 (24) ◽  
pp. 11829
Author(s):  
Ana Alencar ◽  
Ruben Galindo ◽  
Claudio Olalla Marañón
Keyword(s):  
Rock Mass ◽  
Bearing Capacity ◽  
Great Influence ◽  
Shallow Foundations ◽  
Flow Rule ◽  
Correction Coefficient ◽  
Rock Masses ◽  
Calculation Methods ◽  
Dilatancy Angle ◽  
Flow Law

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.

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

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.

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

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.

scholarly journals The ARMR Classification System and the Modified Hoek-Brown Failure Criterion Compared to Directional Shear Strength Models for Anisotropic Rock Masses

2019 ◽  
Author(s):  
Neil Bar ◽  
Charalampos Saroglou
Keyword(s):  
Shear Strength ◽  
Rock Mass ◽  
Failure Criterion ◽  
Classification System ◽  
Failure Criteria ◽  
Rock Masses ◽  
Anisotropic Rock ◽  
Anisotropic Rock Mass ◽  
Degree Of Anisotropy ◽  
Strength Models

The anisotropic rock mass rating classification system, ARMR, has been developed in conjunction with the Modified Hoek-Brown failure to deal with varying shear strength with respect to the orientation and degree of anisotropy within an anisotropic rock mass. Conventionally, ubiquitous-joint or directional shear strength models have assumed a general rock mass strength, typically estimated using the Hoek-Brown failure criterion, and applied a directional weakness in a given orientation depending on the anisotropic nature of the rock mass. Shear strength of the directional weakness is typically estimated using the Barton-Bandis failure criterion, or on occasion, the Mohr-Coulomb failure criteria. Directional shear strength models such as these often formed the basis of continuum models for slopes and underground excavations in anisotropic rock masses. This paper compares ARMR and the Modified Hoek-Brown failure criterion to the conventional directional shear strength models using a case study from Western Australia.

scholarly journals Rock Mass Rating and Geological Strength Index of rock masses of Thopal-Malekhu River areas, Central Nepal Lesser Himalaya

2013 ◽  
Vol 16 ◽  
pp. 29-42 ◽  
Author(s):  
Jaya Laxmi Singh ◽  
Naresh Kazi Tamrakar
Keyword(s):  
Rock Mass ◽  
Surface Condition ◽  
Geological Strength Index ◽  
Rock Mass Rating ◽  
Rock Slopes ◽  
Lesser Himalaya ◽  
Rock Masses ◽  
Strength Index ◽  
Rock Mass Structure ◽  
Exposed Rock

The rock slopes of the Thopal-Malekhu River areas, Lesser Himalaya, were characterized applying various systems of rock mass classification, such as Rock mass Rating (RMR) and Geological Strength Index (GSI), because the study area comprises well exposed rock formations of the Nawakot and Kathmandu Complexes, across the Thopal-Malekhu River areas. In RMR system, mainly five parameters viz. Uniaxial Compressive Strength (UCS) of rock, Rock Quality Designation (RQD), spacing of discontinuity, condition of discontinuity, and groundwater condition were considered. The new GSI charts, which were suitable for schistose and much disintegrated rock masses, were used to characterize rock slopes based on quantitative analysis of the rock mass structure and surface condition of discontinuities. RMR ranged from 36 to 82 (poor to very good rock mass) and GSI from 13.5±3 to 58±3 (poor to good rock mass). Slates (of the Benighat Slate) are poor rock masses with low strength, very poor RQD, and close to very close spacing of discontinuity, and dolomites (Dhading Dolomite) are fair rocks with disintegrated, poorly interlocked, and heavily broken rock masses yielding very low RMR and GSI values. Phyllites (Dandagaun Phyllite), schist (Robang Formation) and quartzite (Fagfog Quartzite, Robang Formation and Chisapani Quartzite), dolomite (Malekhu Limestone), and metasandstone (Tistung Formation) are fair rock masses with moderate GSI and RMR values, whereas quartzose schist and gneiss (Kulekhani Formation) are very good rock masses having comparatively higher RMR and GSI. The relationship between GSI and RMR shows positive and good degree of correlation. DOI: http://dx.doi.org/10.3126/bdg.v16i0.8882   Bulletin of the Department of Geology Vol. 16, 2013, pp. 29-42

scholarly journals A novel solution for ground reaction curve of tunnels in elastoplastic strain softening rock masses

2017 ◽  
Vol 23 (6) ◽  
pp. 773-786 ◽  
Author(s):  
Ali GHORBANI ◽  
Hadi HASANZADEHSHOOIILI
Keyword(s):  
Rock Mass ◽  
Strain Softening ◽  
Numerical Solutions ◽  
Polynomial Regression ◽  
Parameter Determination ◽  
Geological Strength Index ◽  
Support Pressure ◽  
Rock Masses ◽  
Reaction Curve ◽  
Ground Reaction Curve

Ground Reaction Curve (GRC) is one of the most important elements of convergence-confinement method generally used to design tunnels. Realistic presentation of GRC is usually assessed based on the advanced rock strength criteria, also, rock mass behavior (including plasticity and softening treatments). Since taking these parameters into ac­count is not simply possible for practitioners and needs complicated coupled theoretical-numerical solutions, this paper presents a simple novel approach based on Evolutionary Polynomial Regression to determine GRC of rock masses obeying both Mohr-Coulomb and Hoek-Brown criteria and strain softening behaviors. The proposed models accurately present support pressures based on radial displacement, rock mass strength and softening parameter (determination coefficient of 97.98% and 94.2% respectively for Mohr-Coulomb and Hoek-Brown strain softening materials). The ac­curacy of the proposed equations are approved through comparing the EPR developed GRCs with the ground reaction curves available in the literature. Besides, the sensitivity analysis is carried out and in-situ stress, residual Hoek-Brown’s m constant and residual dilation angle are introduced as parameters with the most influence on the support pressure in Hoek-Brown and peak and residual geological strength index are the most affective parameters on the support pressure of tunnels in the strain softening Mohr-Coulomb rock mass.

scholarly journals Rock Mass Characterization for Assessment of Safe Cut Slope and Rock Bearing Capacity at Gondang Dam Site, Karanganyar, Indonesia

2019 ◽  
Vol 4 (1) ◽  
pp. 9
Author(s):  
Sao Sochan ◽  
I Gde Budi Indrawan ◽  
Dwi Agus Kuncoro
Keyword(s):  
Rock Mass ◽  
Bearing Capacity ◽  
Research Area ◽  
Engineering Properties ◽  
Geological Strength Index ◽  
Cut Slope ◽  
Rock Mass Characterization ◽  
Rock Mass Quality ◽  
Allowable Bearing Capacity ◽  
Tuff Breccia

This paper presents results of surface rock mass characterization for assessment of safe cut slopes and allowable bearing capacity of foundation rocks at the construction area of Gondang Dam. The rock mass characterization involved determination of intact rock engineering properties and rock mass quality based on the Geological Strength Index. The rock mass characterization results showed that the research area consisted of moderately to highly weathered and very weak to weak andesite breccia and andesite tuff breccia. The andesite breccia had very poor to fair rock mass quality, while the andesite tuff breccia had poor to fair rock mass quality. The research area was divided into three zones of safe cut slope and allowable bearing capacity. Landslides occurred at natural slopes having poor to very poor rock mass quality and inclinations greater than the determined safe cut slopes.The foundation rock of the embankment dam had fair rock massquality and 135–280 T/m2 allowable bearing capacity

scholarly journals Engineering geological investigations for evaluation of excavation method and stand-up time of the DK99-DK100 Jakarta – Bandung high-speed railway tunnel, Indonesia

2021 ◽  
Vol 325 ◽  
pp. 01005
Author(s):  
Linda Ali ◽  
I Gde Budi Indrawan ◽  
Hendarto Hendarto
Keyword(s):  
Rock Mass ◽  
High Speed ◽  
Poor Quality ◽  
Geological Strength Index ◽  
Rock Masses ◽  
Railway Tunnel ◽  
Tunnel Excavation ◽  
High Speed Railway ◽  
Geological Conditions ◽  
Subsurface Engineering

This paper presents the investigation of surface geology and subsurface engineering geology to analyze the excavation method and stand-up time of the DK99-DK100 Jakarta-Bandung high-speed railway Tunnel, Indonesia. Rock mass quality, tunnel excavation method, and stand-up time determined using Geological Strength Index (GSI), Basic Quality (BQ) systems, converted to Rock Mass Rating (RMR) and The Japan Society of Civil Engineering (JSCE) for comparison. The result shows that the study area consists of slightly to completely weathered andesite breccia and slightly weathered andesite lava. The rock masses at the tunnel elevation had very poor to poor quality and were associated with high weathering degrees. The recommended rock excavation method based on the GSI is digging. The recommended tunnel excavation method based on RMR is multiple drifts, top heading, and bench, while based on JSCE is bench cut method. The tunnel stand-up time is 30 minutes - 2 hours based on the RMR, while it is predicted to be unstable without support based on the BQ. The recommended design is expected to be applied effectively according to the geological conditions. It is expected to understand better the tunnel excavation method in poor rock masses, especially in Indonesia.

scholarly journals Analysis of rock mass behavior with Empirical and Numerical method for the construction of diversion tunnel, Laos

2022 ◽  
Vol 1212 (1) ◽  
pp. 012028
Author(s):  
D J W Mboussa ◽  
S Sun
Keyword(s):  
Numerical Modeling ◽  
Rock Mass ◽  
Field Investigation ◽  
Geological Strength Index ◽  
Rock Masses ◽  
Mountain Area ◽  
Diversion Tunnel ◽  
The Stability ◽  
The Cost ◽  
The Impact

Abstract Tunneling construction in the mountain area is a challenge for engineers and geotechnicians because of instability due to the presence of discontinuities. The objective of this paper is the modeling of surrounding rock masses for the stability of the diversion tunnel to predict the behavior of rock masses during the excavation process for the Nam Phoun hydropower station project in Laos. Field investigation and laboratories test was realized; Empirical methods as Rock mass designation and Geological Strength Index were performed, rock masses were classified in three categories (RM-1, RM-2, and RM-3); in situ stresses were obtained from existing equations, numerical modeling was performed by the 2D plane strain finite element code Phase2 developed by Rocscience, using Generalized Hoek-Brown criterion for each type of rock masses. The results of numerical modeling show the strength zones of stresses and deformations around the tunnel and predict the instabilities around the tunnel during excavations processes. Thus, for all rock’s masses, it will be necessary to consider an analysis for the supports design before the excavation’s process. The findings of this study allow a clearer understanding of the importance to assess a predictive analysis of slope stability during the feasibility phase of a project by engineers to have an idea of instabilities and its significant in preventing the impact on the cost of the project.

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