Papers by Victor M Taboada
This paper presents the prediction of the lateral displacements due to liquefaction in the yards ... more This paper presents the prediction of the lateral displacements due to liquefaction in the yards of the Container Terminal at San Pedrito in the Mexican port of Manzanillo during the earthquake of October 9, 1995 (Ms=7.3, M~8.0). It describes briefly the results of field and laboratory tests carried out after the earthquake in order to obtain the required parameters to compute lateral displacements using the Newmark model and a modified Newmark block analysis which takes account of dilatant behavior; the models were calibrated with results of centrifuge experiments. Field data and simplified liquefaction analysis showed that the liquefied fill had a thickness of 13 m and a gentle slope of one degree. From the laboratory tests a yielding shear stress of 3.3 kPa was estimated, and from seismic risk analyses the input used for the prediction of the lateral displacements was a sinusoidal wave of twenty two cycles of constants amplitude of 3.25 m/s* at a frequency of 1.4 Hz. Since in the case of Manzanillo the laboratory results did not show evidence of dilatant behavior, the original Newmark sliding block analysis was used and predicted a lateral displacements of 1.95 m, which is in good agreement with the actual movements (slightly higher than 2 m) observed after the earthquake.
GEOTECH-YEAR 2000, 2000
This paper presents a computational tool to evaluate lateral ground displacements, DH, induced by... more This paper presents a computational tool to evaluate lateral ground displacements, DH, induced by liquefaction of slopes with gentle inclination, it considers Newmark sliding block model and modified Newmark sliding block analysis which takes into account an increase in soil strength at large strains (due to dilation). Both models were calibrated with results of centrifuge experiments. Then, we analyzed two case histories where seismically induced lateral displacement due to liquefaction were observed. The Wildlife Site (Imperial County, California) and the port of Manzanillo, Mexico. The predicted values of DH are in good agreement in both cases. The results included clearly show the significant effect that soil dilatancy has on DH. Thus, in modeling this phenomenon with a Newmark type approach this aspect should be taken into account to avoid overly conservative estimations of DH values.
The surface and downhole accelerations records of "Central de Abasto Oficinas (CAO)" array at Mex... more The surface and downhole accelerations records of "Central de Abasto Oficinas (CAO)" array at Mexico City, have been analyzed to determine the soil stiffness as a function of shear strain amplitude. The 09/10/95 seismic event (NS component) has been used for this purpose. The shear stress-strain histories have been evaluated directly from the field downhole acceleration records, employing a technique of system identification, and used to obtain the variation of shear modulus with shear strain amplitude. A shear-beam model, calibrated by the identified properties, is found to represent the site dynamic response characteristics. The results have been compared with values obtained in previous investigations from field and laboratory tests.
Using Predicted Dynamic Properties to Perform Seismic Site Response Analyses on a Bay of Campeche Calcareous Soil Deposit
This study presents the influence of using predicted (calculated) normalized shear modulus (G/Gma... more This study presents the influence of using predicted (calculated) normalized shear modulus (G/Gmax) and material damping ratio (D) curves on the design acceleration spectrum at the depth of maximum soil–pile interaction of a calcareous soil deposit in the Bay of Campeche.When comparing the predicted curves to the laboratory curves, it is concluded that due to limitations in the predicting models, the minimum confining pressure (σ’m) that must be used to get a good match with the laboratory curves is 150 kPa. After performing site response analyses for three shear wave velocity profiles and eight recorded acceleration time histories, the design acceleration spectrum was developed based on the envelope of the 24 calculated acceleration spectra. The acceleration amplitudes of the design spectrum in the short period range are slightly larger using the calculated curves than the laboratory curves. For periods longer than 0.27 seconds, the acceleration amplitudes of the design acceleration spectra are identical for practical purposes when both calculated and laboratory curves are used. Therefore, it is recommened to use the equations presented herein to calculate the curves of G/Gmax and D for calcareous soils in practice for preliminary and final seismic site response analyses. They can be especially useful in final evaluations of large or critical projects to calculate the curves when time and cost constraints make it impractical to perform direct experimental determinations of G/Gmax and D curves for each soil layer encountered in the soil deposit.
Prediction of Liquefaction-Induced Spreading by Dilatant Sliding Block Model Calibrated by Centrifuge Tests
Laboratory-determined soil dynamic properties are always (to different degrees) affected by sampl... more Laboratory-determined soil dynamic properties are always (to different degrees) affected by sample disturbance, scale effects, deficient modeling of in situ conditions, and so on. The installation of vertical arrays of strong motion instruments and the ensuing records obtained during various seismic events, have opened the opportunity to explore other alternatives to evaluate soil dynamic properties by solving the inverse problem. In this paper, an analytical procedure that allows the solution of this problem in a simple way is presented and applied to a case history in Mexico City. The model assumes 1-D propagation of shear waves throughout homogeneous viscoelastic soil deposits. The results obtained here are compared with the velocities measured by means of field studies at Central de Abasto Oficinas (CAO) site with a P-S logging system. These comparisons show the potential of this procedure.
Influence of earthquake frequency content on soil dynamic properties at CAO site
Soil Dynamics and Earthquake Engineering, Jun 1, 2002
The installation of vertical downhole arrays in the field that record the soil behavior during ea... more The installation of vertical downhole arrays in the field that record the soil behavior during earthquakes, has opened the opportunity of exploring another alternate method for assessing the soil dynamic properties by solving the inverse problem. This article proposes a methodology for solving this problem using spectral analysis of downhole arrays records. The one-dimensional shear wave propagation model was used,
Normalized Modulus Reduction and Damping Ratio Curves for Bay of Campeche Carbonate Sand
Predictive equations of normalized shear modulus (G/Gmax) and material damping ratio (D) are pres... more Predictive equations of normalized shear modulus (G/Gmax) and material damping ratio (D) are presented for calcareous sand, siliceous carbonate sand and carbonate sand of the Bay of Campeche and Tabasco Coastline. This was achieved using a database of 84 resonant column tests and 252 strain-controlled cyclic direct simple shear test that provide data to define the normalized shear modulus, G/Gmax, and material damping ratio, D, versus cyclic shear strain. The range of cyclic shear strains of the database is from 0.0001% to 1%, and the range of carbonate content (Ca2CO3) from 10% to 100%. The curves of normalized modulus reduction and damping ratio were organized in three groups according to the percentage of carbonate content: 1) calcareous sands (10% to 50%), 2) siliceous carbonate sand (50% to 90%) and 3) carbonate sands (90% to 100%). Two independent modified hyperbolic relations for normalized modulus reduction and material damping ratio versus cyclic shear strain were developed for each group. The normalized shear modulus was modeled using two parameters: 1) a reference strain defined as the strain at which G/Gmax is equal to 0.5, and 2) a parameter that controls the curvature of the normalized modulus reduction curve. The material damping ratio was modeled using four parameters: 1) a reference strain γrD defined as the strain at which D/Dmax= 0.5, 2) a curvature parameter αD that controls the curvature of the material damping ratio curve, 3) a maximum material damping ratio Dmax, and 4) a minimum material damping ratio Dmin. The new empirical relationships to predict the normalized modulus reduction and material damping ratio curves as a function of effective confining pressure are easy to apply in practice and can be used when site-specific dynamic laboratory testing is not available. The curves of G/Gmax-γ and D-γ, are similar between silica sand and calcareous sand. The curves of siliceous carbonate sand and carbonate sand are very similar, but show a different shape and width than the curves of silica sand and calcareous sand. This indicates that when the carbonate content is smaller than 50% there is a small effect on the curves of G/Gmax-γ and D-γ, and a considerable effect when the carbonate content is greater than 50%.
Assessing Small-Strain Shear Modulus Based On In Situ Seismic Measurements in Bay of Campeche Sand
A database with in situ measurements of shear wave velocity (VS), cone tip resistance (qc), and b... more A database with in situ measurements of shear wave velocity (VS), cone tip resistance (qc), and basic soil properties of sand has been established from fifteen offshore geotechnical investigations performed in the Bay of Campeche. VS values were obtained from P-S logging. The database was tailored to develop empirical correlations for small-strain shear modulus (Gmax) based on qc (or relative density), void ratio, and effective stress. Three empirical correlations were developed to determine Gmax based on: 1) void ratio, effective vertical stress, and coefficient of lateral earth pressure at rest; 2) effective vertical stress and relative density determined from CPT data; and 3) effective vertical stress and cone tip resistance. To evaluate the accuracy of the correlations, a comparison was made between VS computed from the three empirical correlations and in situ VS measurements at an independent site. The predictions of VS fall in a rather narrow band, 15 % lower and higher than the in situ VS measurement, which supports the conclusion that these equations provide a useful approach to estimating VS or Gmax for use in ground response analyses or offshore wind farm foundation design at sites where time constraints and finite resources prevent the feasibility of making in situ VS measurements.
Effect of Strain Rate, Sampling Technique and Aging on the Soil Properties Used in the Reassessment of Pile Foundations Performance in the Bay of Campeche
All Days, May 4, 1998
After the Hurricane Roxanne passage over the Bay of Campeche in 1995, a reassessment and requalif... more After the Hurricane Roxanne passage over the Bay of Campeche in 1995, a reassessment and requalification of the offshore infrastructure was required. In order to represent better the real behavior of the platforms under current, wind and wave forces for the reassessment, effects such as soil sampling, strain rate and aging on the soil properties were incorporated in the analysis. The use of static parameters of the soil is an assumption 'very conservative for the analysis of reassessment of existent structures and for better geotechnical characterization the effect of strain rate, sampling technique and aging are considered. The consideration of these effects on the properties of soil were evaluated in IS sites. The laboratory results for soils with strain rate of 10–4 % hour, which corresponds to the wave forces, show a mean value of increment of 35% in the shear resistance of the soil. The push sampling technique showed an increase of 20% in Su versus the wire line technique. For including aging effect, triaxial and direct shear testing is being carry out on samples of different sites of the Bay of Campeche. The reassessment of the offshore structures is optimum if the analysis includes the mentioned effects since the assumptions of the geotechnical characteristics are more realistic. Introduction Offshore facilities in the Bay of Campeche were subjected to hurricane storm loadings during the passage of hurricane Roxanne in 1995. The oceanographic conditions developed were similar to those predicted for a 100 year return period. Due to that event, a reassessment program of the offshore platforms in the Bay of Campeche was initiated. In some cases, the reassessment of the marine platforms involved analytical methods for evaluating the ultimate limit state of the structures. Analyses were carried out using an ultimate limit-state limit- equilibrium analytical model, which is based on plastic-hinge theory and limit equilibrium (Bea et al, 1997). The yield strength of structural elements, the elastic modulus of steel and the soil characteristics have to be defined by the user. The depth variation of the undrained shear strength (for cohesive soils) or the angle of internal friction (for cohesionless soils) are considered, along with the bias and coefficient of variation of the pile capacity subjected to axial and lateral loads. Bias is defined as the ratio between true and computed values. The uncertainties in the parameters considered in the geotechnical problems are thus identified and assessed. Sources of bias in pile capacities may be introduced by the procedure used to (Bea, 1983; Tang, 1988; Tang, Gilbert, 1990):perform the soil boring;sample;perform the testing (in situ, laboratory);define the pile -loads;analyze the individual pile and pile system performance; anddefine the age of the pile at the time that the capacity is to be evaluated. In this paper, only points 2, 3 and 7 are addressed for the Bay of Campeche conditions. It is important to notice that if each of the above sources introduced a bias of 10%, the total bias in the pile capacity would be equal to 2.
Assessing Small-Strain Shear Modulus Based On In Situ Seismic Measurements in Bay of Campeche Sand
Day 1 Mon, May 01, 2023
A database with in situ measurements of shear wave velocity (VS), cone tip resistance (qc), and b... more A database with in situ measurements of shear wave velocity (VS), cone tip resistance (qc), and basic soil properties of sand has been established from fifteen offshore geotechnical investigations performed in the Bay of Campeche. VS values were obtained from P-S logging. The database was tailored to develop empirical correlations for small-strain shear modulus (Gmax) based on qc (or relative density), void ratio, and effective stress. Three empirical correlations were developed to determine Gmax based on: 1) void ratio, effective vertical stress, and coefficient of lateral earth pressure at rest; 2) effective vertical stress and relative density determined from CPT data; and 3) effective vertical stress and cone tip resistance. To evaluate the accuracy of the correlations, a comparison was made between VS computed from the three empirical correlations and in situ VS measurements at an independent site. The predictions of VS fall in a rather narrow band, 15 % lower and higher than t...
1 Research Professor, Geotechnical Department, Institute of Engineering, UNAM. 2 Research Profess... more 1 Research Professor, Geotechnical Department, Institute of Engineering, UNAM. 2 Research Professor, Mine and Engineering Department,Civil Eng. School, National University of Colombia at Medellin 3 Research Professor and Head, Geotechnical Department, Institute of Engineering, UNAM, Apartado Postal 70-472, 04510 Méx 4 Assistant Researcher, Geotechnical Department, Institute of Engineering, UNAM IDENTIFICATION OF MEXICO CITY CLAY DYNAMIC PROPERTIES
In this research, the degradation by fatigue of Mexico City clay is studied using a triaxial equi... more In this research, the degradation by fatigue of Mexico City clay is studied using a triaxial equipment where the cyclic stress amplitude was maintained constant during the experiment. The variables considered in the study were the following: state of the soil, effective mean confining stress, magnitude of cyclic stress and number of loading cycles. Undisturbed samples, anisotropically and isotropically consolidated, were subjected to cyclic loading for this purpose. When analyzing the cyclic stress-strain response with the number of cycles a threshold of permanent deformation in function of the cyclic deviator stress and axial strain was found. When the cyclic strain exceeds this distinctive value the rate of permanent (plastic) deformations accumulate faster. For practical applications of computing permanent deformations in Mexico city a simplified method is proposed. This method considers the above threshold and a hyperbolic model to represent the cyclic response in Mexico City clays.
Effect of Strain Rate, Sampling Technique and Aging on the Soil Properties Used in the Reassessment of Pile Foundations Performance in the Bay of Campeche
All Days, 1998
After the Hurricane Roxanne passage over the Bay of Campeche in 1995, a reassessment and requalif... more After the Hurricane Roxanne passage over the Bay of Campeche in 1995, a reassessment and requalification of the offshore infrastructure was required. In order to represent better the real behavior of the platforms under current, wind and wave forces for the reassessment, effects such as soil sampling, strain rate and aging on the soil properties were incorporated in the analysis. The use of static parameters of the soil is an assumption 'very conservative for the analysis of reassessment of existent structures and for better geotechnical characterization the effect of strain rate, sampling technique and aging are considered. The consideration of these effects on the properties of soil were evaluated in IS sites. The laboratory results for soils with strain rate of 10–4 % hour, which corresponds to the wave forces, show a mean value of increment of 35% in the shear resistance of the soil. The push sampling technique showed an increase of 20% in Su versus the wire line technique. ...
Centrifuge modeling of seismic behavior of a slope in liquefiable soil
Soil Dynamics and Earthquake Engineering, 2002
Two centrifuge tests were designed to improve the understanding the response of liquefied sandy s... more Two centrifuge tests were designed to improve the understanding the response of liquefied sandy slopes beyond initial liquefaction. A distinctive dilative behavior of the soil was observed near the slope where static shear stresses are present. The corresponding drops in the piezometric records and simultaneous negative upslope spikes in the acceleration records were measured in the transducer raw data. This
Predictive Equations of Shear Wave Velocity for Bay of Campeche Clay
All Days, 2013
One of the most important soil parameters required in the analyses of the piles of oil platforms ... more One of the most important soil parameters required in the analyses of the piles of oil platforms subjected to lateral earthquake loading is the shear wave velocity (VS) of the soil. Since in-situ measurements of VS is part of the scope of work of a limited amount of platform sites, there is the need to develop site specific correlations to estimate VS based on basic soil properties. To cover this need a database with in-situ measurements of Vs and basic soil properties of clay has been established. Data were collected from eleven offshore geotechnical investigations performed on behalf of PEMEX for the design and installation of fixed offshore platforms in the Bay of Campeche. The database was tailored to developed empirical correlations between the shear wave velocity and undrained shear strength, effective vertical stress, water content, void ratio, overconsolidation ratio and net cone resistance, using simple regression analyses and multiple regression analyses. Three of the most...
Influence of earthquake frequency content on soil dynamic properties at CAO site
Soil Dynamics and Earthquake Engineering, 2002
The installation of vertical downhole arrays in the field that record the soil behavior during ea... more The installation of vertical downhole arrays in the field that record the soil behavior during earthquakes, has opened the opportunity of exploring another alternate method for assessing the soil dynamic properties by solving the inverse problem. This article proposes a methodology for solving this problem using spectral analysis of downhole arrays records. The one-dimensional shear wave propagation model was used,
Recurrent and Constructive‐Algorithm Networks For Sand Behavior Modeling
International Journal of Geomechanics, 2001
Page 1. The International Journal of Geomechanics Volume 1, Number 4, 371387 (2001) Recurrent an... more Page 1. The International Journal of Geomechanics Volume 1, Number 4, 371387 (2001) Recurrent and Constructive-Algorithm Networks For Sand Behavior Modeling Miguel P. Romo, Silvia R. García, Manuel J. Mendoza, and Victor Taboada-Urtuzuástegui ...
Monte Carlo Simulations of the Dynamic Response of Pile Groups
A study is presented on the effect of variations of relevant parameters within a pile group on th... more A study is presented on the effect of variations of relevant parameters within a pile group on the vertical dynamic response of the group. These parameters include the shear wave velocity of the soil, pile separation, and individual pile response. The study is implemented through Monte Carlo simulations, for maximum and minimum expected degrees of variability in the field. It is concluded that for certain field conditions, random variations can significantly affect the group response by reducing constructive and destructive wave interference. Further studies are suggested as part of the development of an engineering method for dynamic pile group evaluations.
Centrifuge Modeling of Earthquake-Induced Lateral Spreading in Sand
Journal of Geotechnical and Geoenvironmental Engineering, 1998
This paper presents results of 11 centrifuge model tests of liquefaction and earthquake-induced l... more This paper presents results of 11 centrifuge model tests of liquefaction and earthquake-induced lateral spreading in sand using a laminar box. The centrifuge experiments simulate a horizontal or sloping, 10-m thick stratum of water-saturated homogeneous coarse sand of infinite lateral extent and relative density 40–45%, placed on an impervious rigid base. Such homogeneous, clean, coarse stratum represents some field liquefaction situations, but not others involving fine and/or silty sands or strong layering of strata of different permeabilities. The centrifuge tests presented provide significant general insight into mechanisms and parameters influencing the lateral spreading phenomenon. The layer was subjected to lateral base shaking with a prototype peak acceleration ranging from 0.17 to 0.46g, a frequency of 1–2 Hz, and a duration of approximately 22 cycles in all cases. The slope angle simulated in the field αfield ranged from 0 to 10°. Detailed discussions and comparisons of the 11 centrifuge test res...
Uploads
Papers by Victor M Taboada