Distinct-Element Method Simulations of Rock-Socketed Piles: Estimation of Side Shear Resistance Considering Socket Roughness
J.G. Gutiérrez-Ch, S. Melentijevic, S. Senent, R. Jimenez
Abstract
Rock-socketed piles are foundational elements designed to transmit large concentrated loads to stronger materials located at greater depths. The rock-socket side shear resistance is commonly estimated using empirical criteria as a percentage of the rock or concrete uniaxial compressive strength. However, this approach neglects the influence of other important aspects, such as the roughness of the pile-socket interface. In this work, numerical discrete-element models of rock-socketed piles with different degrees of socket roughness are employed to estimate the influence of the socket roughness on the load-settlement response and on the side shear resistance. The numerical simulation results are compared with predictions obtained using empirical correlations based on load test results and proposed by other authors. Results indicate that the discrete-element method is suitable to reproduce rock-socket pile behavior considering socket roughness; they also suggest that sockets drilled with standard tools in soft to medium rock tend to be relatively smooth unless artificially roughened with special tools and that damage to the interface asperities becomes more relevant after socket settlement of about 1% of the socket diameter, especially for rougher piles.
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Distinct element method simulations of rock-concrete interfaces under different boundary conditions
J.G. Gutiérrez-Ch, S. Senent, S. Melentijevic, R. Jimenez
Abstract
The shear behaviour of concrete-rock interfaces has been the aim of extensive research in geotechnical engineering applications such as rock socketed piles, rock bolts and concrete dam arch bridge foundations. Several experimental studies through direct shear tests have been conducted to evaluate the shear behaviour of rock-concrete interfaces under CNL (Constant Normal Load) and CNS (Constant Normal Stiffness) conditions. In this paper, PFC2D numerical simulations of unbonded rock-concrete planar and saw-tooth triangular joints under CNL and CNS boundary conditions are conducted using the Shear Box Genesis (SBG) approach proposed by Bahaaddini et al. (2013b). The numerical simulation results are compared with experimental data published by Gutiérrez (2013) and Gu et al. (2003). Results indicate that the SBG approach reproduces suitably the shear behaviour, failure mode and asperity damage of unbonded (planar and triangular) rock-concrete interfaces, specially under CNL conditions.
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DEM simulation of rock creep in tunnels using Rate Process Theory
J.G. Gutiérrez-Ch, S. Senent, P. Zeng , R. Jimenez
Abstract
The time-dependent (creep) behaviour of rocks affects the safety and stability of tunnels excavated in weak rocks and at great depths. Several theories have been proposed to simulate the creep deformation in rock; i.e., the progressive time-dependent damage that rocks (or other materials) exhibit under constant stress. However, most of these theories do not capture the accelerating strains associated to tertiary creep and leading to rock failure. In this research, the Rate Process Theory (RPT), combined with the Discrete Element Method (DEM), are used to simulate rock creep deformation in deep tunnels. To do that, two-dimensional (2D) DEM tunnel models are built using particles, with their interactions being simulated by a hybrid mixture of the linear and flat joint contact models. The RPT is incorporated into such models by a user-defined Visual C++ script that modifies their friction coefficients during the DEM simulation, depending on the relative velocity between particles. Numerical results show, for the first time, that the joint RPT-DEM approach is able to reproduce all stages of tunnel convergences associated to rock creep, including tertiary creep; and that it can reproduce the rock damage associated to such creep strains.
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Learning behavior of foundation and retaining structures based on small-scale tests
APRENDIZAJE DEL COMPORTAMIENTO DE CIMENTACIONES Y ELEMENTOS DE CONTENCIÓN BASADO EN MODELOS FÍSICOS ENSAYADOS A ESCALA REDUCIDA (Código: IE24.0406)
Coordinador: José G. Gutiérrez-Ch
Co-coordinador: Jesús González Galindo
Técnico del Laboratorio: Jesús Page
Becario: Elias Esteban Mateo
El objetivo general del Proyecto de Innovación Educativa es que el alumno adquiera los conocimientos para realizar un diseño óptimo de las cimentaciones y de las estructuras de contención, a partir de experiencias complementarias basadas en modelos físicos a escala reducida. En concreto, se quiere que el alumno alcance los siguientes objetivos específicos:
- Desarrollar la capacidad de diseñar cimentaciones y estructuras de contención.
- Comprender el comportamiento de las cimentaciones y estructuras de contención con las cargas de servicio.
- Entender cómo, cuándo y por qué se produce el mecanismo de rotura de las cimentaciones y estructuras de contención.
- Conocer el grado de sensibilidad del comportamiento de una cimentación y/o estructura al cambio de terreno de cimentación y de las acciones externas.
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Failure mechanism for a shallow foundation based on a small-scale test
Earth pressure on a retaining wall: Failure surface of active case
Earth pressure on a retaining wall: Failure surface of active and passive case
Failure mechanism for a shallow foundation based on a small-scale test
Rock shear creep modelling: DEM – Rate process theory approach
J.G. Gutiérrez-Ch, S. Senent, E.P. Graterol, P. Zeng , R. Jimenez
Abstract
Understanding the rock creep behavior is necessary to determine the long-term strength and safety of several geotechnical designs. There are several formulations to study the rock creep; however, most of them do not properly capture the tertiary creep. To overcome such limitation, model improvements have been made and new creep models (e.g., creep models with an associated viscoplastic flow rule) have been proposed. As an alternative, the Rate Process Theory (RPT) has been recently used to study the soil/rock creep behavior. This article expands previous works by analyzing the applicability of the Discrete Element Method (DEM) with RPT implementation to simulate Rock Shear Creep (RSC). To do that, (i) 2D DEM direct shear creep tests under Constant Normal Load (CNL) conditions are used, (ii) DEM specimens are built by a combination of the Flat-Joint Contact Model (FJCM) and the Linear Model (LM), and (iii) the DEM + RPT approach is calibrated by using experimental tests from the literature. DEM results presented here illustrate the suitability of DEM–RPT methodology to reproduce all stages of RSC, including tertiary creep. The effect of the applied shear stress and normal stress on RCS is also analyzed. Finally, the most important novelties of this paper are: (1) the DEM–RPT methodology can be easily calibrated by using a laboratory direct shear creep test; (2) the calibrated DEM models are suitable to analyze the main aspects of RSC; and (3) DEM results qualitatively agree with the overall experimental trend published in the literature
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