DSpace Angular :: Browsing by Author "Saez, Esteban"

Browsing by Author "Saez, Esteban"

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A hybrid PML formulation for the 2D three-field dynamic poroelastic equations
(2023) Mella, Hernan; Saez, Esteban; Mura, Joaquin
Simulation of wave propagation in poroelastic half-spaces presents a common challenge in fields like geomechanics and biomechanics, requiring Absorbing Boundary Conditions (ABCs) at the semi-infinite space boundaries. Perfectly Matched Layers (PML) are a popular choice due to their excellent wave absorption properties. However, PML implementation can lead to problems with unknown stresses or strains, time convolutions, or PDE systems with Auxiliary Differential Equations (ADEs), which increases computational complexity and resource consumption.This article introduces a novel hybrid PML formulation for arbitrary poroelastic domains. Instead of using ADEs, this formulation utilizes time-history variables to reduce the number of unknowns and mathematical operations. The modification of the PDEs to account for the PML is limited to the PML domain only, resulting in smaller matrices while maintaining the governing equations in the interior domain and preserving the temporal structure of the problem. The hybrid approach introduces three scalar variables localized within the PML domain.The proposed formulation was tested in three numerical experiments in geophysics using realistic parameters for soft sites with free surfaces. The results were compared with numerical solutions from extended domains and simpler ABCs, such as paraxial approximation, demonstrating the accuracy, efficiency, and precision of the proposed method. The article also discusses the applicability of the method to complex media and its extension to the Multiaxial PML formulation.The codes used for the simulations are available for download from https://github.com/hmella/POROUS-HYBRID-PML.& COPY; 2023 Elsevier B.V. All rights reserved.
An assessment of uncertainties in V_S profiles obtained from microtremor observations in the phased 2018 COSMOS blind trials
(2022) Asten, Michael W.; Yong, Alan; Foti, Sebastiano; Hayashi, Koichi; Martin, Antony J.; Stephenson, William J.; Cassidy, John F.; Coleman, Jacie; Nigbor, Robert; Castellaro, Silvia; Chimoto, Kosuke; Cornou, Cecile; Cho, Ikuo; Hayashida, Takumi; Hobiger, Manuel; Kuo, Chun-Hsiang; Macau, Albert; Mercerat, E. Diego; Molnar, Sheri; Pananont, Passakorn; Pilz, Marco; Poovarodom, Nakhorn; Saez, Esteban; Wathelet, Marc; Yamanaka, Hiroaki; Yokoi, Toshiaki; Zhao, Don
Site response is a critical consideration when assessing earthquake hazards. Site characterization is key to understanding site effects as influenced by seismic site conditions of the local geology. Thus, a number of geophysical site characterization methods were developed to meet the demand for accurate and cost-effective results. As a consequence, a number of studies have been administered periodically as blind trials to evaluate the state-of-practice on-site characterization. We present results from the Consortium of Organizations for Strong Motion Observation Systems (COSMOS) blind trials, which used data recorded from surface-based microtremor array methods (MAM) at four sites where geomorphic conditions vary from deep alluvial basins to an alpine valley. Thirty-four invited analysts participated. Data were incrementally released to 17 available analysts who participated in all four phases: (1) two-station arrays, (2) sparse triangular arrays, (3) complex nested triangular or circular arrays, and (4) all available geological control site information including drill hole data. Another set of 17 analysts provided results from two sites and two phases only. Although data from one site consisted of recordings from three-component sensors, the other three sites consisted of data recorded only by vertical-component sensors. The sites cover a range of noise source distributions, ranging from one site with a highly directional microtremor wave field to others with omni-directional (azimuthally distributed) wave fields. We review results from different processing techniques (e.g., beam-forming, spatial autocorrelation, cross-correlation, or seismic interferometry) applied by the analysts and compare the effectiveness between the differing wave field distributions. We define the M index as a quality index based on estimates of the time-averaged shear-wave velocity of the upper 10 (V-S10), 30 (V-S30), 100 (V-S100), and 300 (V-S300) meters and show its usefulness in quantitative comparisons of V-S profiles from multiple analysts. Our findings are expected to aid in building an evidence-based consensus on preferred cost-effective arrays and processing methodology for future studies of seismic site effects.
An Empirical Correlation between the Residual Gravity Anomaly and the H/V Predominant Period in Urban Areas and Its Dependence on Geology in Andean Forearc Basins
(2021) Maringue, Jose; Saez, Esteban; Yanez, Gonzalo
The study of site amplification effects is crucial to assess earthquake hazards that can produce great damage in urban structures. In this context, the gravity and the ambient noise horizontal-to-vertical spectral ratio (H/V) are two of the most used geophysical methods to study the properties of the subsoil, which are essential to estimate seismic amplification. Even though these methods have been used complementarily, a correlation between them has not been thoroughly studied. Understanding this correlation and how it depends on geology could be important to use one method as an estimator of the other and to make a distinction between the seismic and gravimetric basement. In this research, a comparison between the residual gravity anomaly and the H/V predominant period is performed using a long dataset from different projects on sedimentary basins in a group of the most important cities in Chile. To simplify the geological information, a seismic classification is used for soils, which considers the Vs30 and the predominant period of vibration (T0). The results of this comparison show a direct correlation between both parameters, the higher the negative residual gravity anomaly the higher the H/V predominant period. This correlation improves when only soft soils are considered, increasing the R2 value in more than a 50% in all the individual cities with respect to the overall correlation. When all the cities are considered, the R2 value for soft soils increases up to 0.87. These results suggest that the ideal geological background for this correlation is when a soft soil layer overlies a homogeneous bedrock. Heterogeneities in the bedrock and in the soil column add dispersion to the correlation. Additionally, the comparison between the depth to basement inferred by both methods show differences of less than 15% in soft sites; in denser sites, the difference increases up to 30% and the definition of a clear H/V peak is more difficult. In general, the gravimetric basement is deeper than the seismic one. However, gravimetric depths to basement can be under/over-estimated in zones with a heterogeneous soil column.
Analysis of the breakage of the bio-cementation generated on glass beads during a direct shear test using a DEM model
(2024) Valencia-Galindo, Miguel; Saez, Esteban; Kozakovic, Martin; Havlica, Jaromir; Kramolis, David; Chavez-Crooker, Pamela
The improvement of soil behaviour by the bacterial precipitation of calcium carbonate has been extensively studied in geotechnical engineering. However, the evolution of bio-cementation bonds under shear conditions is only partially understood. This research presents a micromechanical approach to gain a deeper insight into the interaction between bio-cemented particles. A series of glass bead samples were treated with Microbial Induced Calcite Precipitation (MICP) and then subjected to direct shear tests. A calibrated model based on the Discrete Element Method was used to reproduce the macro-mechanical paths observed in the experiments, allowing the detailed analysis and description of the bond evolution at the microscopic scale in the treated samples. In general, it was found that a higher rate of bond breakage occurred before the peak shear strength was reached, and this was followed by a relatively constant rate of bond breakage associated with a macroscopic softening trend. Tensile stress was identified as the primary fracture mechanism. Finally, it was determined that the bond breakage mechanism is influenced by several factors, such as bond distribution, particle array, and the mechanical parameters of the bond.
Computational modelling of dynamic soil-structure interaction in shear wall buildings with basements in medium stiffness sandy soils using a subdomain spectral element approach calibrated by micro-vibrations
(2022) Ayala, Felipe; Saez, Esteban; Magna-Verdugo, Carolina
This paper presents a strategy for modelling dynamic soil-structure interaction (DSSI) using the spectral element method (SEM) with a Discontinuous Galerkin approach, calibrated by micro-vibrations. The proposed methodology allows not only to adjust the vibration frequencies of the structure but also the observed vibration modes. First, models of two structural shear wall buildings with basements in medium dense sandy soils are developed to estimate empirical modal characteristics and calibrate the structural subdomain and low-strain site properties. Convenient 3D arrays of multiple seismic sensors are used to obtain the environmental vibrations measurements. Afterwards, an optimization process is conducted to calibrate volumetric models of structures. This optimization is performed by preserving the most relevant modal frequencies and shapes to achieve an equivalent dynamic response. Finally, structural models are placed into a neighbouring soil model (soil subdomain), approximating nonlinear soil behaviour by an equivalent linear strategy. Using this complete soil-structure interaction model, relevant engineering performance parameters are assessed via simulations of buildings subjected to a plane wave excitation. The results show the significant effect DSSI have in shear-wall buildings with basements and the importance of considering the flexibility of the foundation in the interpretation of the results. In general, results indicate that DSSI effects are strongly dependent on the input frequency content, which might cause a reduction of the inter-story drifts. Furthermore, a significant period lengthening of the studied structures up to 47% is found, as well as a considerable decrease in story shear up to 220% and a maximum lateral roof displacement reduction of 34% when compared against fixed base referential responses.
Continuous characterization of dynamic soil behavior by Digital Image Correlation in a transparent shear laminar box
(2022) Segaline, Hugo; Saez, Esteban; Ubilla, Javier
This work characterizes and analyzes the dynamic behavior of a sandy soil due to one-dimensional propagation of mechanical waves into a transparent laminar shear box. The outstanding char acteristic of this laminar box is a transparent front glass, which allows monitoring the soil behavior by a high-speed and high-resolution camera, and then computing the displacement field in the soil by the Digital Image Correlation (DIC) technique. The response of the laminar container was evaluated using ambient vibrations, harmonic signals and Ricker wavelets. Afterward, dynamic soil properties derived from DIC analysis are compared against theoretical and laboratory results. Finally, a numerical simulation is carried out using the finite element method, where the influence of the lateral friction of the glass on the motion is assessed and discussed. It is concluded that the transparent laminar shear box provides a useful tool for studying the continuous dynamic soil behavior; additionally, the transparent boundary has a minor impact on the results and a minimum observable cyclic shear strain of about 10-4 was reached.
Earthquake-induced pressures on discontinuous piling support on Santiago gravel
(ELSEVIER SCI LTD, 2012) Saez, Esteban; Ledezma, Christian
Discontinuous anchored piling support (anchored soldier piles without lagging) is one of the most frequent earth-retaining systems used in temporary deep excavations in Santiago, Chile. The main advantages of using discontinuous piling support are their relatively low cost and ease of installation. This system is particularly efficient on stiff soils with deep groundwater table, conditions usually found in Santiago. This paper presents a numerical investigation of the characteristics of earthquake induced lateral pressures on discontinuous pile-supported excavations in Santiago gravel. An equivalent bi-dimensional plane-strain model was developed on the basis of a more refined 3D model in order to quantify the influence of the "arching effect" on the dynamic lateral earth-pressures. The dynamic response was studied for a suite of Chilean ground motion recorded on rock in order to evaluate the variability of the dynamic pressures and their influence on the piles' internal forces. These results are then compared against some simplified design recommendations. (C) 2012 Elsevier Ltd. All rights reserved.
Effect of sand particle shape on micromechanical modeling in direct shear testing
(2024) Necochea, Javier E.; Saez, Esteban; Hanley, Kevin J.
Soil representation in discrete element method (DEM) simulations is a complex process due to the intrinsic variability in grain shape. Many methods have been proposed to include shape effects in DEM, from rolling friction to aspherical particle representations such as ellipsoids or polyhedra. In this paper the micromechanical differences between two commonly used methods of shape representation, rolling friction applied to spherical particles and ellipsoids, are investigated for direct shear testing. This simulation study is supported by dry direct shear tests in the laboratory using a poorly graded sand and three vertical confining pressures: 50, 100 and 200 kPa. While the bulk behavior observed in the laboratory can be matched using both shape representation approaches, the micromechanics show significant differences. The average cumulative rotation of the ellipsoidal particles is an order of magnitude lower than for the spheres with rolling friction. The addition of rolling friction significantly affects the mechanical redundancy of the system, making the spherical-particle samples more hyperstatic than their ellipsoidal equivalents. Although using ellipsoids enables a better representation of the micromechanical behavior, this increases the computational cost five-fold compared to using rolling friction and spheres.
Effect of the inelastic dynamic soil-structure interaction on the seismic vulnerability assessment
(2011) Saez, Esteban; Lopez-Caballero, Fernando; Modaressi-Farahmand-Razavi, Arezou
This paper presents a study of the influence of inelastic dynamic soil-structure interaction (DSSI) on the seismic vulnerability assessment of buildings. The seismic vulnerability is evaluated in terms of analytical fragility curves constructed on the basis of non-linear dynamic finite elements (FE) analysis. An analytical sensibility strategy is introduced in order to define a suitable size of the motion database to be used for computing fragility curves. The fragility curves developed in this study are compared with reference curves. Concerning the effect of the inelastic DSSI, a general reduction of seismic demand when DSSI phenomena are included is found. Derived fragility curve reflects this seismic demand reduction. The importance of the ground motion database is highlighted in terms of the variability of parameters describing derived fragility curves. Comparison with reference curves are satisfactory. Findings illustrate clearly the importance and the advantages of an adequate DSSI effects evaluation. (C) 2010 Elsevier Ltd. All rights reserved.
Effects of soil heating changes on soil hydraulic properties in Central Chile
(2024) Giraldo, Carolina V.; Acevedo, Sara E.; Contreras, Cristina P.; Santibanez, Fernando; Saez, Esteban; Calderon, Francisco J.; Bonilla, Carlos A.
Wildfires are natural phenomena for most ecosystems on Earth. Many soil properties are impacted by fire, including soil hydraulic properties. We used a laboratory experiment to replicate the temperatures reached by a natural wildfire and documented the effects on soil hydraulic properties. This study hypothesizes that the impact of heating on soil hydrological properties can be explained by the interaction of a number of variables especially organic matter content (OM), cation exchange capacity (CEC), texture, pH, and electrical conductivity (EC). The main objective of this study is to explore the interconnections between soil hydraulic, chemical, and physical properties, focusing on understanding how these relationships change across different ecoregions and temperatures. Sixteen soils were collected across 16 sites susceptible to forest fires in the Central Zone of Chile and heated to 100 degrees C and 300 degrees C for two hours. These sites were representative of two distinct ecoregions: the Chilean Matorral (CM) and the Valdivian Temperate Forests (VTF). Chemical, physical, and hydraulic soil properties were measured before and after heating. At 100 degrees C, there were no significant changes in chemical, physical, or hydraulic soil properties. At 300 degrees C, significant changes were observed in most soil properties in soils from both ecoregions. The OM content and CEC decreased, whereas pH and electrical conductivity increased. In addition, clay content and water aggregate stability (WSA) decreased, while all hydraulic properties increased their values. The aforementioned results demonstrate that infiltration increased after the soil was heated. This can be attributed primarily to decreases in clay content. At the same time, the water repellency (R) index decreased, allowing water to more easily wet the soil particles. Correlations revealed that CEC and clay are the main factors ruling soil hydraulic properties at all temperatures. Clay mineralogy also contributes to the soil hydraulic behavior observed. Nonlinear models were developed to estimate hydraulic properties at 100 degrees C and 300 degrees C, using the main soil properties. The models illustrated that the soils of the CM ecoregion, which are characterized by lower OM and influence of clay/CEC ratio, would be less affected by fire compared to the soils of VTF. The water holding capacity would decrease in both ecoregions. However, due to the greater changes in OM and clay in VTF, the impact would be greater than in CM.1
Evaluation of dynamic soil-structure interaction effects in buildings with underground stories using 1 g physical experimentation in a transparent shear laminar box
(2022) Segaline, Hugo; Saez, Esteban; Ubilla, Javier
This article presents a study of the Dynamic Soil-Structure Interaction (DSSI) using physical reduced-scale models of a building under different configurations of above-ground and underground stories. Each model was tested in a laminar shear box with a transparent front side. This characteristic of the device makes it possible to visualize the soil particles during the test and acquire data from the soil-structure interaction in a direct and spatially continuous way. A shaking table, an array of 3 high-speed and high-resolution cameras and a tactile dynamic pressure sensor were used. Ricker wavelets, with a wide range of frequencies and amplitudes, were used to evaluate the transfer functions in the system and the seismic response of model. Kinematic interaction effects were evaluated using the Digital Image Correlation (DIC) technique. It is verified that the experimental system allows a detailed tracking of the dynamic interaction between the building and the surrounding soil. The results show the direct relationship between the frequency content of the input wavelet and the dynamic pressure distribution acting on the underground levels, and the increase of the building's first vibrating period. In addition, it was found that the distribution and magnitude of the lateral soil thrust is dominated by the super-structure vibration, and not the ground movement. This relationship becomes more important as the slenderness of the building increases, i.e., as the rocking mode of vibration becomes more significant. Additionally, in the case of buildings with basements, our results suggest that the combination of the increased confinement, the interaction of the foundation in terms of motion compatibility and the vibrations transferred from the super-structure to the ground produces an invariable reduction in effective base motion, suggesting that neglecting the effects of DSSI would be a conservative assumption.
Evaluation of the Effectiveness of a Soil Treatment Using Calcium Carbonate Precipitation from Cultivated and Lyophilized Bacteria in Soil's Compaction Water
(2021) Valencia-Galindo, Miguel; Saez, Esteban; Ovalle, Carlos; Ruz, Francisco
Microbial-induced carbonate precipitation (MICP) is a bio-inspired solution where bacteria metabolize urea to precipitate. This carbonate acts as a bio-cement that bonds soil particles. The existing framework has focused mainly on applying MICP through infiltration of liquid bacterial solutions in existing soil deposits. However, this technique is inefficient in soils with high fines content and low hydraulic conductivity, and thus few studies have focused on the use of MICP in fine soils. The main objective of this study was to evaluate the effect of MICP applied to compaction water in soils containing expansive clays and sandy silts. This approach searches for a better distribution of bacteria, nutrients, and calcium sources and is easy to apply if associated with a compaction process. In soils with expansive minerals, the effect of MICP in swelling potential was explored at laboratory and field scales. In sandy silts, the evolution of the stiffness and strength were studied at the laboratory scale. The treatment at the laboratory scale reduced the swelling potential; nevertheless, no significant effect of MICP was found in the field test. In sandy silts, the strength and stiffness increased under unsaturated conditions; however, subsequent saturation dissolved the cementation and the improvement vanished.
Geological and geotechnical investigation of the seismic ground response characteristics in some urban and suburban sites in Chile exposed to large seismic threats
(2022) Maringue, Jose; Mendoza, Laura; Saez, Esteban; Yanez, Gonzalo; Montalva, Gonzalo; Soto, Valeria; Ayala, Felipe; Perez-Estay, Nicolas; Figueroa, Ronny; Sepulveda, Natalia; Galvez, Carlos; Ramirez, Paola; Ovalle, Carlos
The central area of Chile's Valparaiso Region has been classified as a seismic gap for a major earthquake, which makes it very important to understand the seismic hazard of the zone. Generally, seismic codes consider a qualitative classification of sites to estimate the possible damage in the case of an earthquake scenario. Estimating the values of acceleration could be very important to prevent damages and increase preparedness for these rare events. In this research, a qualitative and quantitative estimation of seismic hazard is performed in the study area (Valparaiso region between Papudo and San Antonio 32 degrees-34 degrees S). This is achieved through an integrated and relatively economical approach which considers the information from Geology, Geophysical experiments (Gravity and seismic methods), and Geotechnical analyses. The results of the geophysical survey and geology information allow dividing the zone into five site types through a new proposal of site classification that depends not only on the V-s30,V- but also on the sites predominant period (T-0), which is an innovation of this work for the Chilean code. The Peak Ground Acceleration (PGA) values in the study zone were estimated using a Ground Motion Predictive Equation developed for the Chilean subduction zone. Additionally, we consider three different seismic scenarios according to the history of events in Central Chile. The results of this quantitative analysis show PGA values up to 0.52 g for the median and 1.2 g for the 84th percentile of the scenarios. Overall, the highest accelerations (PGA) are in zones with low shear wave velocities (< 500 m/s), a long predominant period (> 0.4 s) and where geology establishes the presence of low stiffness soils. The comparison of response spectra from the model against records from 2010 Maule and 1985 Valparaiso earthquakes shows available models tend to overpredict the intensities.
Modeling self-compaction and static stability of a copper filtered tailings pile under unsaturated conditions
(2024) Gallardo, Ricardo; Saez, Esteban; Lopez-Caballero, Fernando
Filtered tailings piles have better mechanical stability than other tailings disposal alternatives because they operate in an unsaturated condition. However, very few studies have quantitatively assessed the contribution of partial saturation for both self-compaction and mechanical stability. In this article, we evaluate the mechanical stability of a filtered tailing pile, based on an analysis of self-consolidation by material deposition under unsaturated conditions, considering rates of 1 h, 1 day and 4 days. For this purpose, an experimental study was carried out which included oedometric and triaxial consolidation tests in both, saturated and unsaturated conditions. Based on these results, a constitutive soil model was calibrated using the Bishop's effective stress concept, considering the evolution of the effective saturation and including soil-water characteristic curve (SWCC) as a function of volumetric strains. The results show that the proposed modeling strategy provides a reasonable approximation of laboratory paths with a single set of parameters. Additionally, the same approach was applied to model the pile's construction process. In this case, it was observed that the potential failure surface is triggered when the soil reaches a saturation degree of about 65-70%. At and this value, the soil behavior is practically independent of deposition rates, slope inclination and pile height. However, the factor of safety (FoS) decreases for faster deposition rates compared to slower ones.
Numerical modeling of 3D site-city effects including partially embedded buildings using spectral element methods. Application to the case of Vina del Mar city, Chile
(2020) Soto, Valeria; Saez, Esteban; Magna-Verdugo, Carolina
In recent years, seismic wave propagation analyses have become a powerful tool to evaluate the site effects in a given region. Among several approaches, Spectral Element Method (SEM) has been widely used with that purpose because its flexibility and computational efficiency. In addition to other effects than basin shape, material nonlinearity and heterogeneity, the multiple interactions between the soil and structures, denominated site-city effects (SCI), can play a crucial role in densely populated areas. There are many options to model this kind of interaction, especially if the buildings are partially embedded on the soil. This paper evaluates the importance of the proper SCI modeling against more standard uncoupled approaches, focusing on the local interaction between the soil and a group of buildings including inelastic soil behavior. We focus our work on the case of downtown Vina del Mar, a touristic coastal city of central Chile, where the observation of a reiterated distribution of damage in reinforced concrete buildings during two major earthquakes has motivated numerous studies. For that purpose, a realistic 3D numerical model of the area is created, considering the existing buildings and using micro-vibration as a main calibration tool. The open-source code SPEED was used to perform the wave propagation simulation, which combines the spectral element method with a discontinuous Galerkin approach. A geophysical study was conducted to estimate the model parameters, shear modulus degradation and damping curves are extracted from laboratory tests to account for the non-linearity of the soil. In general, the results indicate that the inclusion of the SCI is beneficial to the structure's response in most cases, and that SCI modeling needs to considerate the level of embedment to obtain more precise results. Indeed, in buildings of 12 or more stories, the response would not be affected by the level of embedding of the base and the inclusion of site-city effects is beneficial, while for buildings lower than 5 stories, the total embedment of the base generates a significant decrease of the response.
Rheological, petrophysical and geometrical constraints of a subduction channel from a numerical model perspective: Insights from La Cabana Paleozoic peridotites, Coastal Cordillera of south-central Chile
(2022) Sanhueza, Jorge; Yanez, Gonzalo; Barra, Fernando; Maringue, Jose; Figueroa, Ronny; Saez, Esteban
The emplacement of ultramafic blocks in accretionary complexes poses a geodynamic problem due to their negative buoyancy. In this study, we explore plausible emplacement scenarios for peridotite bodies in the Coastal Cordillera of south-central Chile by combining geophysical observations, numerical modeling and available petrological data for ultramafic blocks exhumed along the subduction channel. The La Cabana massif is the largest serpentinized peridotite complex yet recognized in the Coastal Cordillera, however, its size and petrophysical characteristics remain unknown. The geophysical measurements were performed to determine the size of this body, involving magnetic airborne surveys and electrical resistivity tomography. Inversion data show that the largest ultramafic block in La Cabana is 3 km long, 1.5 km wide and at least 1.2 km deep. This result constrains the characteristics of the block transported by the subduction channel. In the second step, we developed a numerical model for the subduction channel assuming a viscous rheology. In this modeling effort we search for tectonic scenarios that provide adequate conditions for the exhumation of the ultramafic body in La Cabana. These scenarios included a combination of key parameters, subduction angle dip and velocity, subduction channel geometry, rheology and density contrast. Scenarios compatible with the exhumation of La Cabana body type includes channel viscosity range of 10(19-20) Pa s, fast exhumation rates at mantle depths (10-20 mm/yr; >30-40 km), steep subduction angles (30 degrees-60 degrees), subduction channel widths of 3-5 km, density contrast between -200 and -400 kg/m(3) and a body diameter of 1.5 km which is consistent with our geophysical inversions. On the contrary, slow exhumation rates (similar to 1 mm/yr), low subduction angles (15 degrees), high-density contrasts (-400 to -600 kg/m(3)) and bodies larger than 1.5 km wide, are not viable exhumation scenarios. The methodology developed provided insights to infer ancient subduction channel geometries and rheologies that include peridotite.
Scale and suction effects on compressibility and time-dependent deformation of mine waste rock material
(2024) Osses, Rodrigo; Pineda, Jubert; Ovalle, Carlos; Linero, Sandra; Saez, Esteban
Designing high mine waste rock piles for long-term behavior requires material mechanical characterization over a large range of stresses and variable environmental conditions. However, representative coarse samples cannot be handled by standard testing devices and the common approach is to test small-scaled samples at the laboratory, which might be affected by particle size effects when compared to the field material. Several reported results indicate that coarser samples present higher amount of particle crushing than small-scaled samples, thus lower dilatancy and higher compressibility. However, specific studies of size effects on time-dependent deformation are lacking. The aim of this paper is to identify the effects of particle size and suction on stressdeformation mechanism of partially saturated mine waste rock. Oedometric compression tests on two parallel graded samples are presented: the gravelly fraction (dmax=50 mm) and the sandy fraction (dmax=2.36 mm). Each stress increment triggers << instantaneous >> and delayed strains. The results reveal the combined effects of particle size and humidity on the mechanical behavior. Coarser samples exhibit higher total compressibility and creep deformation, which also increases with the material humidity. The results give empirical support for the development of scaling laws and suggest that total deformation can be decoupled considering a suction dependent index for creep deformation.
Topographical and structure-soil-structure interaction effects on dynamic behavior of shear-wall buildings on coastal scarp
(2021) Sucasaca, Julio; Saez, Esteban
This paper investigates numerically the influence of slope topography, soil stratigraphy and dynamic interaction between close shear-wall buildings of typical residential projects on coastal scarp. A numerical model based on real buildings taken as cases for this study, is calibrated with field measurements. A nonlinear finite element dynamic analysis is conducted to derive topographical aggravation factors prior to excavation and construction of the buildings and to assess structural responses after their construction for different interaction scenarios and ground motion inputs. We concluded that the surface profile has a large effect on the dynamic response of a stiff low-rise building when their characteristic wavelengths are close each other and it can play a detrimental role increasing up to 80% the interstory drift, 35% the seismic coefficient and 57% the fixed-base fundamental period depending on the input. In several other input cases including far-field earthquake records, dynamic soilstructure interaction is beneficial. Furthermore, it is shown that the structure-soil-structure scenario has negligible additional effect from a practical point of view with respect to soil-structure interaction for this case of study. These results suggest that similar residential projects should be cautious in the design of low-rise buildings located near a slope crest.

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