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The paper studies strike-slip fault rupture propagation through dense sand and its interaction with surface foundations, combining physical and numerical modelling. A series of centrifuge tests is conducted using a three-section split-box, which allows the modelling of two strike-slip faults per test. A free-field test is initially conducted, followed by four interaction tests. Eight different foundation configurations are studied, varying the foundation location, surcharge load, aspect ratio and rigidity. The experiments are numerically simulated employing three-dimensional finite-element modelling, combining periodic boundaries and a relatively simple yet efficient constitutive model, developed as part of this study. Based on a Mohr–Coulomb yield criterion, the model incorporates post-yield isotropic frictional hardening and softening (MC–HS). Carefully calibrated on the basis of triaxial tests, the model is validated against the centrifuge model tests, and exploited to derive further insights. The MC–HS model covers the entire range from elastic to fully softened response, capturing the deviatoric and volumetric behaviour of dense sand, and especially its pre-softening volumetric response, which is proven to be crucial for the simulation of the complex mechanisms of strike-slip faulting. Both physical and numerical modelling reveal the formation of diagonal shear ruptures at the ground surface (Riedel shears). These are complex helicoidal structures, formed due to the spatial variation of shear stresses. Foundation response is mainly governed by the kinematic constraint offered by its presence. Fault rupture locations close to its sides typically lead to a translational mechanism, whereas locations close to its centreline lead to a rotational one. Foundation rigidity is proven to be a prerequisite for the development of both mechanisms, which rely on the ability of the foundation to resist the developing normal and shear stresses.

This paper combines data from laboratory, centrifuge testing, and numerical tools to highlight the predictive capabilities of the Bayesian method for uncertainty quantification and propagation. The Bayesian approach is employed to estimate uncertain parameters of a multi-yield constitutive model using data from cyclic-triaxial testing. Then, predictive capabilities of a finite element model in reproducing the dynamic response of a saturated sand deposit are investigated by drawing samples from the estimated posterior probability distributions of the constitutive model parameters. Variability of the predicted responses due to estimation uncertainty is evaluated. The response of centrifuge tests is used to assess the simulated responses.

Preshaking by previous seismic activity can significantly affect the liquefaction resistance of saturated sands. Field evidence, cyclic laboratory testing and centrifuge modeling show that: (i) earthquake events that build up excess pore pressures short of liquefaction strengthen the soil; and (ii) liquefying earthquakes may weaken the soil. The paper presents the results of a centrifuge test (Experiment 2), where a 6 m saturated loose silty sand deposit was subjected to 52 successive base shakings. Three types of shakings were used: preshaking Events A, with a shaking duration of 5 cycles, and stronger Events B and C having a duration of 15 cycles, with Events C having the largest input accelerations. A total of 35 Events A, 9 Events B, and 8 Events C were applied at the base of the model in an alternating sequence. All Events C liquefied the deposit, with the Events B inducing liquefaction at the beginning but not at the end of Experiment 2. Events A generally induced excess pore pressures but not liquefaction. In addition to the pore pressures, horizontal accelerations, settlement and densification, and the soil shear wave velocity, Vs, were also monitored during the test. The results were compared with those of Experiment 1, reported in a previous publication, where a similar 6 m deposit of the same silty sand was subjected to a different sequence of shakings A and B which did not include any Event C. Conclusions are drawn on the effect of the strong Events C on the deposit's response. Events A, B and C of Experiment 2 are plotted on existing Vs –based liquefaction charts. The charts predict well the liquefaction response of the deposit at the beginning of Experiment 2. On the other hand, for shakings near the end of the test, the charts predict liquefaction for the Events B, which by this time have stopped liquefying the deposit due to the previous history of shakings. This result is consistent with the field evidence including the presence of a number of “false positives” in the charts for silty sand sites in the Imperial Valley of California, an area of intense seismic activity.

Several factors have led to the extended need for investigation of the static and dynamic behaviour of mine tailings and include the rising generation and surface storage of mine waste, its frequent use as a construction material for the retaining structures and the relatively high rate of associated failures, with seismic liquefaction being a rather common cause. In this experimental study, dynamic response and surface slope stability of a layered mine tailings deposit were examined by means of four centrifuge tests performed at the Center for Earthquake Engineering Simulation (Rensselaer Polytechnic Institute). The material under study was fine copper–gold tailings and the varying parameters were average degree of consolidation prior to dynamic loading and base acceleration amplitude. The material was found to be liquefiable and its performance in terms of acceleration, shear strain, slope stability, residual lateral deformation, pore-pressure build-up and liquefied depth was somewhat dependent on the aforementioned parameters. The response of the deposits changed with increasing depth and effective stress, which made centrifuge testing highly advantageous.

This paper explores the generation of harmonics of a monochromatic excitation frequency in the stress response of an excited soil deposit. The relationship between the level of nonlinearity in the soil and the generation of harmonics is investigated in terms of a simple hysteretic stress-strain model. Centrifuge tests of soil deposits subjected to base excitation are used to confirm numerical inferences. Effects of harmonics generation were also analyzed in nonlinear and equivalent-linear numerical simulations of an excited soil deposit. It is shown that the harmonics are present in both physical experiments and nonlinear numerical simulations, but cannot be captured by equivalent-linear analyses.

The paper presents the implementation of an identification technique to characterize the pore pressure behavior of a silty sand centrifuge deposit subjected to more than 70 seismic shakings with full pore pressure dissipation between shakings. The seismic shakings were meant to crudely simulate the seismic history of field deposits in some very seismically active zones in California. The technique estimates shear stresses and strains based on acceleration and pore pressure recorded using a vertical array of sensors in the deposit. A constitutive model was implemented to identify optimal material parameters controlling the contractive behavior of the soil based on the recorded response of all shakings. It was found that the seismic history of soil deposits plays an important role in determining the contractive tendency of the material, significantly influencing the pore pressure response of the deposit. That is, the seismic history can reduce or increase the resistance of a deposit to contraction and liquefaction.

This study investigated the dynamic response and liquefaction of level saturated-sand deposits subjected to biaxial shaking using a number of centrifuge tests. Dense and loose sandy soil deposits were built in a 2D laminar container and subjected to a series of biaxial base excitations that approximate in somewhat realistic fashion the conditions of a site subjected to earthquake shaking. A dense array of accelerometers and pore pressure sensors was used to monitor the deposit response. The recorded accelerations and pore pressures were employed along with a non-parametric identification procedure to estimate the corresponding dynamic shear stress-strain histories. In turn, these histories were employed to assess the effects of non-proportional loading on soil contraction and dilation mechanisms. Pore water pressure buildup was found to be affected by load non-proportionality and a direct function of the phase angle of the induced shear stresses. The loose and dense soil deposits had contrasting as well as similar response patterns.

This article presents numerical simulations investigating pore pressure buildup of a sand layer with a free drainage boundary at the top under both low and high overburden pressures and sub...

The article presents simulations of the seismic liquefaction response of dense and loose clean Ottawa sand under low and high overburden in the centrifuge, using Program FLAC3D and the P2Psand constitutive model. P2Psand was initially calibrated in the paper with cyclic stress-controlled triaxial tests and then modified with information from two centrifuge experiments. The calibrated model was used to simulate four centrifuge tests covering relative densities from 45% to 80% and overburden pressures from about 100 kPa (∼1 atm) to 600 kPa (∼6 atm). The four numerical computations were fully coupled effective stress simulations that allowed for pore water pressure buildup and dissipation at every time step. The calibration yielded very good matches between numerical and experimental results in all four centrifuge experiments, and calibrated P2Psand input parameters are suggested for practitioners in similar clean sands. The simulations confirmed the increased diffusivity of the sand layer under high overburden obtained before from the centrifuge results. The reason is that P2Psand assumes that the sand bulk modulus is proportional to the square root of the mean effective stress, consistent with the similar conclusion derived from the centrifuge data by the authors. The calibrated P2Psand model was also used to perform “no flow” simulations of the same four centrifuge experiments, in which fluid flow was not allowed during or after shaking. No flow simulations are used sometimes in practice to reduce numerical effort, on the assumption that liquefaction in the field is mostly undrained. It was found that this assumption may produce useful engineering results for a low overburden of 1 atm, but it may become increasingly incorrect and too conservative at higher overburden. The reason is that for certain field conditions, fluid flow becomes more significant during shaking under high overburden due to increased sand diffusivity.

Liquefaction induced ground failures during seismic events have been of major concern to the engineering community. Laboratory, full-scale, and centrifuge experimentation has provided valuable insights on the mechanics and propagation of liquefaction. Concurrently, advances in the computational field have led to refined numerical tools to simulate the liquefaction phenomenon. In an effort to better evaluate the modeling capabilities, the Liquefaction Experiments and Analysis Project (LEAP) aims at providing numerical modelers with high quality experimental data that can be used in a series of prediction exercises. For this purpose, in early 2015 several centrifuge tests were conducted at different facilities all over the world and were followed by numerical simulations. This paper presents the centrifuge test that was conducted at the Center for Earthquake Engineering Simulation at Rensselaer Polytechnic Institute and discusses the modeling techniques that were employed in order to gain a variety of information on the soil response.

The Liquefaction Experiments and Analysis Projects (LEAP) is an international effort to produce a set of high quality test data and to then use it in a validation exercise of existing computational models and simulation procedures for soil liquefaction analysis. A validation effort (LEAP-GWU 2015) was undertaken using a benchmark centrifuge model of a sloping deposit tested in a rigid-wall container. This article presents and discusses the shear stress-strain responses and effective stress paths of the LEAP-GW 2015 centrifuge tests and numerical predictions (including an assessment of the effects of the rigid boundaries).

LEAP (Liquefaction Experiments and Analysis Projects) is an effort to formalize the process and provide data needed for validation of numerical models designed to predict liquefaction phenomena. For LEAP-GWU-2015, one project within LEAP, an experiment was repeated at 6 centrifuge facilities (Cambridge University, Kyoto University, University of California Davis, National Central University, Rensselaer Polytechnic Institute, and Zhejiang University) and the results were shared and archived for the purposes of validation of numerical models. This paper describes the specifications for the LEAP-GWU-2015 experiment and compares the experimental results from the six facilities. The specified experiment was for uniform medium dense sand with a 5 degree slope in a rigid container subject to a ramped, 1 Hz sine wave base motion. The experiment was meant to be relatively simple to enable different facilities to produce comparable experiments. Although it cannot be claimed that identical experiments were precisely replicated on different centrifuges, it is argued that the results are similar enough that each experiment lends veracity to the set of results. A benefit of variability between experiments is that the variety enables a more general validation. Important lessons with regard to specification of future experiments for validation of numerical models are summarized. LEAP-GWU-2015 has demonstrated an approach that is a useful reference for future validation studies.

The paper presents numerical predictions of excess pore pressure, liquefaction and settlement response of four centrifuge model tests of 6 m uniform deposits of saturated clean Ottawa sand, placed by dry pluviation and having a relative density ranging from 38% to 66%. The deposits were subjected to 1D uniform base shaking consisting of 10–15 cycles of peak acceleration ranging from 0.04 to 0.12 g. All predictions were conducted with the nonlinear effective stress numerical code Dmod2000. Significant effort was spent in calibrating Dmod2000 by matching the pore pressure and settlement measurements of the first shaking (S1) of a series of shakings conducted in centrifuge Experiment 3. This resulted in very good predictions of both pore pressures and settlement measured in this shaking S1. The exercise showed the importance for realistic simulations of having the correct soil compressibility and permeability. This calibrated version of Dmod2000 was used for a good pore pressure prediction of the preshaken deposit in the same Experiment 3 (S36), by modifying only one parameter in the undrained pore pressure model; and also well predicted pore pressure responses in Tests FFV3 and PFV1, without any change in the parameters of Dmod2000 except for use of the new input motions (Type B predictions). The experimental and numerical results showed that both cyclic shear stress/strains and upward water flow determine together the pore pressure buildup and liquefaction phenomena. The soil response is partially drained rather than undrained, and pore pressure dissipation does take place during shaking both before and after liquefaction occurs.

T-walls are pile-supported floodwalls commonly built in New Orleans. They are founded on long concrete or steel battered piles and include a sheet pile cut off for seepage and gradient control. Since soils in southern Louisiana contain soft and compressible silt and clay, these floodwalls need to be designed to resist flood loads and loads produced by consolidation of soft soil under the weight of new fill. In an attempt to develop a comprehensive T-wall design procedure that appropriately considers field conditions, the United States Army Corps of Engineers New Orleans District partnered with Rensselaer Polytechnic Institute and Virginia Polytechnic Institute and State University. A testing programme was developed to perform centrifuge tests that would provide insight into the mechanisms and magnitudes of settlement-induced bending moments and reliable datasets for validation of numerical models. This paper describes the experimental approach and presents two centrifuge tests with T-walls resting directly on clay. The bending moments on the battered piles significantly increased under the weight of the new fill. With settlement around the piles reaching values of 1·5 m, the bending moments at least doubled over the testing course, with maximum values observed at the top third of the pile length.

This paper presents an integrated experimental and numerical study of high-density polyethylene pipeline behavior under earthquake faulting that induces both bending and compression. The experiment...

The paper presents a series of centrifuge tests simulating a level site consisting of granular soil deposits subjected to various biaxial and uniaxial base excitations. The tests were conducted at RPI NEES centrifuge facility to assess the dynamic response characteristics of level deposits under multidirectional shaking. Synthetic sinusoidal waves were used as base excitations to test loose models under biaxial and uniaxial shaking. Dense arrays of accelerometers were used to monitor the deposit response along with pore water pressure transducers. Two uniaxial tests and one biaxial shaking test were conducted on three similar soil models to study the impact of multidirectional shaking on the generation of soil liquefaction. The two uniaxial shaking tests consisted of: (a) a test with input energy content using an Arias intensity similar to that of the biaxial input shaking and (b) a test with 10% increase in one of the components of the biaxial shake amplitude, as commonly done in practice for uniaxial simulation of multidirectional field shaking. The observed acceleration and pore pressure are used along with non-parametric identification procedures to estimate the corresponding dynamic shear stress–strain histories. The measured results along with the stress and strain histories obtained are used for two purposes: first, to shed light on the properties of liquefaction occurring through the stratum under uniaxial shaking; second, to show the difference in soil behaviour when it is subjected to biaxial shaking. The latter purpose is evident in the strain energy generated in the biaxial test compared to that of equivalent and traditional uniaxial tests.

This paper presents an identification technique to characterize the contractive and pore pressure behavior of loose sandy soils under seismic excitation. The technique relies on acceleration and pore pressure records provided during excitation by vertical arrays of accelerometers and pore pressure sensors. The technique employs non-parametric estimates of shear stresses and strains. A multi-surface plasticity approach is used to model the soil response. A reduced scale centrifuge model and a large scale experiment are used to demonstrate the capabilities of the developed technique. The technique allows for a more complete interpretation of the coupled shear–volume behavior of a soil deposit.

After catastrophic levee failures triggered by the 2005 Hurricane Katrina, concrete T-walls with batter piles are extensively used to enhance the integrity of levees in the New Orleans area. Since the foundation soils in this region typically include soft and compressible clays, T-walls with batter piles should be designed to account for bending moments and stresses induced by settlement. However, the current T-wall design procedure for estimating these settlement-induced bending moments (SIBMs) only takes a limited range of conditions into consideration. This paper presents results from a series of finite-difference numerical simulations to investigate the effects of various parameters on SIBM in pile-supported T-walls. The numerical model was first used to simulate a centrifuge test and upon comparison, a reasonable agreement was observed between the numerical simulation and experimental results. The numerical model was then used to investigate the effects of different parameters including pile connecti...

Accurate evaluation of soil dynamic properties is essential for seismic response analyses of sites. In a number of studies, site properties have been identified using one-dimensional analyses. Such analyses uncouple the two-dimensional (horizontal) response of soil deposits, which is inherently coupled. This paper presents a system identification technique that takes into account the coupled two-directional response of soil deposits. The technique employs non-parametric estimates of the shear stresses derived from acceleration records provided by a vertical (downhole) array. A multi-yield surface plasticity approach is used to model the multi-dimensional stress-strain relation. The identification technique is first verified using finite elements computational simulations. This technique was then used to assess the coupled response of the Wildlife liquefaction research site (Imperial Valley, California). The identified shear moduli and shear wave velocities were found to be in a very good agreement with those measured in the field using crosshole seismic testing.

The effect of preshaking and repeated liquefaction on liquefaction resistance was studied in a large-scale shaking table experiment, in which a sequence of 51 shakings was applied to the ba...

Two centrifuge experiments were conducted at Rensselaer Polytechnic Institute (RPI) to evaluate and assess the validity of the generalized scaling laws. The experiments were performed within the framework of the Liquefaction Experiments and Analysis Project (LEAP) and consisted of testing a saturated sloping deposit subjected to a tapered base input acceleration. The two tested models reflected consistent soil conditions but were built based on different scaling principles. The first model observed the conventional scaling laws for centrifuge physical modeling. The second model reflected the generalized scaling laws. The two tested models exhibited consistent response before liquefaction. The generalized scaling model showed a higher susceptibility to liquefaction and had a higher rate of pore pressure buildup.

Several researchers found that the behavior of natural preshaken soils can be very different from artificial recent fills. This paper presents an extensive database of two very long centrifuge experiments (CS-5-1-1 and CC-5-1-1) performed both on silty and clean sand at the geotechnical centrifuge testing facility at Rensselaer Polytechnic Institute (RPI). The two experiments test the effect of seismic preshaking history on the liquefaction resistance of sandy soils. The database described herein was generated using the NEEShub online DataStore tool under the name “PRESHAKE: Centrifuge modeling of the effect of seismic preshaking on the liquefaction resistance of sands” (DOI: http://dx.doi.org/10.4231/D38K74X78 ). The paper discusses the tools and materials used in the experiments along with an explanation of each item in the database. Sample analyses are also presented in the paper to give an insight on the capabilities of the database for numerical and analytical applications. The paper is concluded with some possible applications along with tips and limitations of the database.

Centrifuge and large-scale testing in geotechnical engineering are very useful tools for modeling soil behavior under different loading conditions, particularly under earthquake loading. The paper presents an extensive database of nine centrifuge and large-scale liquefaction experiments performed both at the geotechnical centrifuge testing facility at Rensselaer Polytechnic Institute (RPI) and the large-scale testing facility at the University at Buffalo (UB). The database described herein was generated using the NEEShub online DataStore tool under the name “CENSEIS: Centrifuge and Large (Full)-Scale Modeling of Seismic Pore Pressures in Sands” (DOI: http://dx.doi.org/10.4231/D3GF0MX4F ). The paper discusses the tools and materials used in the experiments along with an explanation of each item in the database. Sample analyses are also presented in the paper to give an insight on the capabilities of the database for numerical and analytical applications. The paper is concluded with some possible applications along with tips and limitations of the database.

A series of centrifuge tests of a sloping ground were conducted at Rensselaer Polytechnic Institute (RPI). These tests were used to monitor and assess the soil response, in terms of generated accelerations, excess pore water pressure (EPWP) and associated lateral spreading, as a function of variations in the dynamic input motion and soil relative density. This series of tests are part of the Liquefaction Experiments and Analysis Projects (LEAP-2017), an international effort to assess the repeatability and reproducibility of centrifuge experimental results, and verify and validate soil liquefaction numerical tools using the experimental data.

A series of centrifuge tests were conducted to examine self-weight consolidation, dynamic response, liquefaction potential, and slope stability of mine tailings alone and in mixtures with w...

The main objective of this study is to investigate systematically the lateral earth pressure induced by the cone penetration test (CPT) conducted at various distances from the rigid container wall. A series of centrifuge CPTs were performed in dry Ottawa sand using two miniature penetrometers with diameters of 4 and 12 mm. The CPT locations varied from 2 to 42 times the cone diameter. The change of lateral earth pressure was measured using tactile pressure sensors. Results from this study have shown that the lateral earth pressure change was mainly associated with the initial relative density of soil, the distance away from the testing location and the diameter of the cone penetrometer. The change of lateral pressure can be as large as 150–200 kPa at a distance of 2–4 times the diameter of the CPT. The effect of initial soil relative density on the change of lateral earth pressure was greater when using the 4 mm CPT than the 12 mm CPT. Some residual lateral pressure was observed after completion of the CPT in dense sand tests.

This paper reviews the application of physical modelling to problems related to soil properties and soil behaviours. The problems discussed included soil characterisation techniques, spatial variability, soil arching, soil ageing, dynamic soil behaviour and unsaturated soils.

An identification technique is used to estimate the nonlinear dynamic properties of a soil deposit using the acceleration records provided by a vertical (downhole) array along with a nonlinear least squares optimization algorithm. The technique employs non-parametric estimates of the shear stresses derived from the recorded accelerations; therefore, it does not require the forward modeling of the whole soil deposit. Soil properties are described by a hyperbolic shear stress–strain relation. A multi-surface plasticity approach is used to model the stress–strain relation. Convergence and accuracy of the identification technique are assessed using numerical simulations. Two centrifuge experiments are used to validate and demonstrate the capabilities of the technique to estimate the stiffness and damping ratio profiles of a site subjected to base excitation. Performance of the technique is also evaluated using field data corresponding to the 1987 Superstition Hills earthquake recordings from the Wildlife Liquefaction Array at the Imperial Valley in Southern California. The identification results were found to be in good agreement with direct measurements of shear wave velocities.

This paper is a systematic effort to clarify why field liquefaction charts based on Seed and Idriss׳ Simplified Procedure work so well. This is a necessary step toward integrating the states of the art (SOA) and practice (SOP) for evaluating liquefaction and its effects. The SOA relies mostly on laboratory measurements and correlations with void ratio and relative density of the sand. The SOP is based on field measurements of penetration resistance and shear wave velocity coupled with empirical or semi-empirical correlations. This gap slows down further progress in both SOP and SOA. The paper accomplishes its objective through: a literature review of relevant aspects of the SOA including factors influencing threshold shear strain and pore pressure buildup during cyclic strain-controlled tests; a discussion of factors influencing field penetration resistance and shear wave velocity; and a discussion of the meaning of the curves in the liquefaction charts separating liquefaction from no liquefaction, helped by recent full-scale and centrifuge results. It is concluded that the charts are curves of constant cyclic strain at the lower end (Vs1

Shallow foundations supporting bridge piers, building frames, shear walls and monuments are often subjected to extreme lateral loading such as wind in offshore environments, or strong seismic shaking. Under such loading conditions, foundations may experience a host of non-linear phenomena: sliding on and uplifting from the supporting soil or even soil failure in the form of development of ultimate bearing capacity mechanisms. This type of response is accompanied by residual settlement and rotation of the supported structural system. Nevertheless, inelastic foundation performance can provide potential benefits to the overall seismic integrity of the structure. Thanks to such non-linearities, energy dissipation at or below the foundation level may eventually limit the seismic demand on structural elements. Several theoretical and experimental studies have provided encouraging evidence to this effect. This paper has a dual objective: first, to study the behaviour of shallow foundations under vertical and lateral monotonic loading and under lateral slow cyclic loading of progressively increasing amplitude; second, to explore the differences in foundation response between reduced-scale 1g and centrifuge 50g model testing. Emphasis is placed on interpreting their discrepancies by unveiling the role of scale effects. The role of soil densification due to multiple loading cycles with uplifting is also highlighted.

The paper presents a series of centrifuge tests of level sites consisting of a granular soil deposit, with and without an embedded structure subjected to various biaxial and uniaxial base excitations. The tests were conducted at RPI NEES centrifuge facility to assess the dynamic response characteristics of level deposits and soil-structure interaction (SSI) under multidimensional conditions. Synthetic sinusoidal waves were used as base excitations to test soil models under biaxial and uniaxial shaking. A dense array of accelerometers was used to monitor the deposit response along with pore water pressure transducers. One uniaxial test and two biaxial shaking tests were conducted on three similar soil models, to study the effect of multidirectional shaking on the generation of soil liquefaction for dense deposits. The observed acceleration and pore pressure are used along with non-parametric identification procedures to evaluate the corresponding dynamic shear stress–strain histories. The measured results along with the obtained time histories are used to shed light on the mechanisms of liquefaction occurring through the stratum under multiaxial shaking. It also shows the effect of soil relative density on soil behavior when subjected to biaxial shaking. The soil–structure interaction test showed significant differences in soil behavior at different locations beneath the footing when subjected to biaxial shaking. This difference is associated with coupling in stress–strain in both experiments compared to the more known uniaxial soil behavior.

Natural and man-made hazards are often associated with costly damages to civil infrastructure systems, such as buildings, bridges, Levees, dams, pipelines and offshore structures of all types. The lack of high-quality field and lab data of soil system response have eluded researchers and practitioners until recently. Recent advancements in physical modeling facilities (centrifuge and full scale) and advancement in remote sensing technology are leading to a new reality for the health assessment of soil–structure systems. This new reality is leading to a paradigm shift in the evaluation and modeling of soil–structure systems. Physical modeling, remote sensing and computational simulations are destined to replace the current empirical approaches and will ultimately become the main tool for analysis and design of soil–structure systems. The paper discusses the results of recent research studies utilizing physical modeling to simulate the response of critical soil–structure systems to natural and man-made hazards.

The paper compares two liquefaction case histories in California: (1) the response of the Wildlife site in the Imperial Valley to the 2010 El-Mayor Cucapah earthquake (Mw=7.2, amax=0.15 g)...

Accurate estimation of shear wave velocity is necessary in most geotechnical earthquake engineering applications. This paper details two different methodologies implemented for the estimation of the shear wave velocity profile of soil deposits. The first implemented method employs bender elements, whereas the second relies on a system identification technique and the use of acceleration recordings. In order to compare the two techniques, two centrifuge experiments were conducted using saturated Ottawa F#55 sand in a one-dimensional laminar container. The sand was deposited at void ratios 0·723 and 0·625, respectively. Shear wave velocity profiles obtained using both techniques were compared. These profiles were also compared to those documented in the literature. The results agree well with each other and with the values from the literature. The matching results support the validity of using both methods as a means of estimating the shear wave velocities in centrifuge models as well as in full-scale testing.

Centrifuge modeling of pore pressure buildup in a sand deposit as a result of shaking is evaluated by comparison with a large-scale experiment. In large-scale Test SG-1, a 5.6-m-thick, mildly sloping deposit of hydraulic fill clean Ottawa sand of Dr=40%, was subjected to 5 s of low-intensity base shaking (

A systematic study is presented herein on the seismic response of buried pipelines subjected to ground fault rupture in the form of normal faulting. In this study, advanced computational simulations are conducted in parallel with physical testing using a geotechnical centrifuge. For the numerical simulations, the pipeline was modeled using isotropic 3-D shell elements and the soil was modeled using either 1-D spring elements or 3-D solid (continuum) elements. The results from continuum finite-element analyses are compared with those from a Winkler-type model (in which the pipe is supported by a series of discrete springs) and with results from centrifuge tests. In addition, via appropriate modeling of the soil-pipe interaction, the q-z relation of the soil medium is elucidated for normal faulting events. The numerical analysis results demonstrate the potential for continuum modeling of events that induce pipe-soil interaction and results in improved understanding of pipe-soil interaction under normal faulting.

Assessing the health of and maintaining civil infrastructure has been an increased concern in the wake of natural disasters such as Hurricane Katrina in 2005 and the summer 2007 flood events in the UK. The variability of properties within geotechnical systems makes predictions of soil behavior extremely difficult, especially when soil models are not calibrated with field-measured performance. Unfortunately the current state of the art in geotechnical system health assessment is either based on very expensive monitoring systems for real-time information or on periodic measurement of ground surface displacements. Accordingly, a need has arisen for a system capable of in situ, real-time monitoring of levees, embankments, and other earthen structures. The work presented herein highlights the development of novel, affordable sensing technologies for use in a framework to monitor, manage and ensure the safety of geotechnical infrastructure. MEMS (micro-electro-mechanical systems)-based in-place inclinometer system, Measurand’s ShapeAccelArray (SAA), is now established as a sensing tool for simultaneous measurement of 3D soil acceleration and 3D ground deformation up to a depth of one hundred meters, with an accuracy of ±1.5 mm per 30 m. Each sensor array is connected to a wireless sensor node to enable real-time monitoring as well as remote sensor configuration. This system is now being further developed to include digitally integrated pore pressure measurement in the form of vibrating wire piezometers equipped with microprocessors (called SAAPs). The SAAPs are able to convert vibrating wire data to digital data downhole, and they integrate easily into the SAA system. In situ testing was conducted in a levee in England subjected to significant tidal loading (up to 6 m of fluctuation during spring tides) through collaboration with the European Union’s UrbanFlood project. In addition to the SAAs and SAAPs installed in three sections of the levee, the site was also instrumented with other sensors from Alert Solutions and TenCate, providing values for comparison. The likelihood of this levee to experience deformation and the density of instrumentation installed in the bank made this the ideal location to test the new SAAP system. The additional insight into subsurface behavior provided by the SAAPs is integral in the development of a comprehensive system for monitoring and management of civil infrastructure. The preliminary testing indicates the suitability of this new multi-parameter system for inclusion in a multi-scale monitoring and health assessment framework, which will be implemented in New Orleans, LA in 2012.

This paper has two objectives. The first is to evaluate the cyclic shear strain needed to trigger liquefaction, γcl, in clean and silty sands in the field during earthquakes as an alternative to the currently used cyclic resistance ratio (CRR). The second objective is to explore the effect of a high effective overburden pressure, σv0′, on the value of CRR. The first objective is accomplished mainly by using an equation relating γcl and CRR valid for shear wave velocity–based liquefaction charts. This equation is supplemented with laboratory results from undrained cyclic strain-controlled tests as well as large-scale and centrifuge model shaking experiments. It is shown that for recent uncompacted clean and silty sand deposits and earthquake magnitude Mw=7.5, γcl≈0.03%, with this value increasing to γcl≈0.3% (in some cases to 0.6%) in denser and overconsolidated, preshaken, and compacted sands. These small values of γcl in the field are controlled by two factors: excess pore pressure buildup in the...

A systematic study of buried pipeline response to strike-slip faulting was performed wherein advanced computational simulations were conducted in parallel with a series of physical tests employing split-boxes within the geotechnical centrifuge at Rensselaer Polytechnic Institute and the full-scale testing facility at Cornell University. This article describes the numerical modeling and simulations of the experimental tests. The buried pipeline and the surrounding soil are modeled using nonlinear beam (shell) elements and elasto-plastic springs distributed along the pipeline, respectively. Using the finite element method, reasonable predictions are obtained for the axial and bending strain distributions measured during the tests. It is also shown that finite element analysis using pipe beam elements and a modified soil spring model can accurately predict the pipeline seismic behavior due to strike-slip fault rupture, especially when the pipe is subjected to combined bending and tension. In addition, existi...

A number of centrifuge tests have been conducted to study the interaction between liquefied sand under earthquake-induced lateral spreading and pile foundations. Most of those centrifuge models resemble full-scale prototypes from case histories, usually with limited field measurements, while a few of them replicate the conditions of full-scale heavily instrumented laboratory tests. This paper presents the results of centrifuge tests modelling the single pile interaction with liquefied sand conducted at Rensselaer Polytechnic Institute in Troy, New York, and their comparison with the respective large-scale prototype tests conducted at the National Research Institute for Earth Science and Disaster Prevention in Tsukuba, Japan. A critical analysis of the scaling laws currently used for this kind of centrifuge tests is included, focusing on the use of viscous fluid for centrifuge model saturation and the validity of the centrifuge scaling laws when shear band development plays an important role in soil–structure interaction. This paper also presents recommendations for pile foundations design against the lateral pressure associated with liquefied sand under lateral spreading.

This paper examines in detail the mechanics of lateral spreading observed in a full-scale test of a sloping saturated fine sand deposit, representative of liquefiable, young alluvial and hydraulic fill sands in the field. The test was conducted using a 6-m tall inclined laminar box shaken at the base. At the end of shaking, nearly the whole deposit was liquefied, and the ground surface displacement had reached 32 cm. The presented analysis of lateral spreading mechanics utilizes a unique set of lateral displacement results, DH, from three independent techniques. One of these techniques—motion tracking analysis of the experiment video recording—is especially useful as it produced DH time histories for all laminar box rings and a complete picture of the lateral spreading initiation with an unprecedented degree of resolution in time and space. A systematic study of the data identifies the progressive stages of initiation and accumulation of lateral spreading, lateral spread contribution of various depth ranges and sliding zones, their relation to the simultaneous pore pressure buildup, and the soil shear strength response during sliding. DOI: 10.1061/ASCEGT.1943-5606.0000409 CE Database subject headings: Soil liquefaction; Residual strength; Hydraulic fill; Full-scale tests; Lateral displacement. Author keywords: Liquefaction; Residual strength; Hydraulic fill; Full-scale tests; Lateral displacement.

Permanent ground deformation (PGD) is one of the most damaging hazards for continuous buried lifelines. This hazard is especially severe when the PGD results in net compression in the pipe. In that case, buckling of pipe material can occur. If buckling is moderate, deformation of the pipe cross-section can lead to flow restriction and high friction losses, and eventually require line replacement. If buckling is severe, high localized strains can lead to pipe rupture, loss of contents, and possible pollution of surrounding soil. In this article, centrifuge tests of buried pipelines subject to abrupt ground failure in the form of surface faulting are presented. The fault movement results in mostly compression in the pipe. The test results are compared with a case history of pipe failure in the 1999 Izmit, Turkey earthquake and also with the results from the centrifuge tests which result in net tension in the pipe. The experimental setup, procedures, and instrumentation are described in detail. Suggestions f...

Numerical models are commonly used in practice to predict the occurrence and propagation of liquefaction and lateral spreading. Nevertheless, there are still only a few good-quality data sets to validate these models. An international collaboration between physical and numerical modelers has been initiated through the Liquefaction Experiments and Analysis Projects (LEAP) to establish a standard method for validation of numerical models. One of the main goals of LEAP is to provide numerical modelers with high-quality experimental data that can be used in a series of prediction exercises. In this framework, a small-scale centrifuge test of a sloping deposit was conducted at Rensselaer Polytechnic Institute (RPI) in January 2015 and provided comprehensive data sets for evaluation of soil liquefaction numerical tools. The same experiment was repeated in September 2015 to assess the robustness and repeatability of the physical modeling methods at RPI. This paper serves a double objective: (1) to study the response and liquefaction potential of sloped deposits experimentally and (2) to establish the repeatability of experimental data to be used in numerical simulations.

This paper provides an assessment of tactile pressure sensors for geotechnical applications. A tactile pressure sensor is an array of small sensing units, called sensels, embedded in a polymeric sheet or pad that measures the magnitude and distribution of stresses normal to the sheet surface. Methods for minimizing the effects of shear on sensor measurements are discussed and the efficacy of these methods are demonstrated by laboratory experiments. The time-dependent characteristics of the sensors are evaluated and recommendations are provided for measurements that account for time-dependent effects. Tactile pressure sensor measurements in response to vertical loading and unloading and to lateral loads on full-scale pipelines affected by large horizontal ground movements are compared with independent measurements of the loads. Sensor measurements are used to show the distribution of normal stress on pipelines subject to large lateral soil movement.

This paper presents experimental results and analysis of six model centrifuge experiments conducted on the 150 g-ton Rensselaer Polytechnic Institute centrifuge to investigate the effect of soil permeability on the response of end-bearing single piles and pile groups subjected to lateral spreading. The models were tested in a laminar box and simulate a mild infinite slope with a liquefiable sand layer on top of a nonliquefiable layer. Three fine sand models consisting of a single pile, a 3×1 pile group, and a 2×2 pile group were tested, first using water as pore fluid, and then repeated using a viscous pore fluid, hence simulating two sands of different permeability in the field. The results were dramatically different, with the three tests simulating a low permeability soil developing 3–6 times larger pile head displacements and bending moments at the end of shaking. Deformation observations of colored sand strips, as well as measurements of sustained negative excess pore pressures near the foundations i...

Permanent ground deformation is arguably the most severe hazard for continuous buried pipelines. This paper presents results from two pairs of centrifuge tests designed to investigate the differences in behavior of buried high-density polyethylene pipelines subjected to normal and strike-slip faulting. The tests results show that, as expected, the pipeline behavior is asymmetric under normal faulting and symmetric under strike-slip faulting. In the case of strike-slip faulting, the soil–pipe interaction pressure distribution is symmetric with respect to the fault. However, in the case of normal faulting, there is a pressure concentration close to the fault trace on the up-thrown side, with much lower soil–pipe interaction pressures at other locations on the pipe. The soil–pipe interaction force versus deformation relationship (i.e., the p–y relationship) was obtained based on the experimental data. The p–y relationships for both the strike-slip and normal faulting cases were also compared with the relationships defined within the American Society of Civil Engineers (ASCE) guidelines. It was found that, for the case of strike-slip faulting, the experimental p–y relationship is generally consistent with the ASCE guidelines. In contrast, the experimental p–y relationship is much softer than that defined by the ASCE guidelines for the normal faulting scenario.

Permanent ground deformation is a severe hazard for continuous buried pipelines. This technical paper presents results from four centrifuge tests designed to investigate the influence of pipe-fault orientation on pipe behavior under earthquake faulting. The experimental setup and procedures are described, and the test results are presented. The test results show that, as expected, pipe axial strain is strongly influenced by the pipe-fault orientation angle, whereas the influence of pipe-fault orientation angle on pipe bending strain is minor. The measured pipe strains were shown to follow the trend predicted by the Kennedy model. Also, through a parametric study using the Kennedy model, the experimental data were extrapolated for cases of pipeline with longer unanchored length. By combing the data from strain gauges and tactile pressure sensors, transverse force–deformation relations or p–y relations for the pipe were determined. The data indicates that the underlying p–y relationship varies along the len...

Hurricane Katrina was one of the worst natural disasters in U.S. history. The effects of the hurricane were particularly devastating in the city of New Orleans. Most of the damage was due to the failure of the levee system that surrounds the city to protect it from flooding. This paper presents the results of centrifuge models conducted at Rensselaer Polytechnic Institute and the U.S. Army Corps of Engineers simulating the behavior of the levees at London Avenue North and South that failed during Hurricane Katrina. Those levees failed without being overtopped by the storm surge. Also included are the results of a centrifuge model of one levee section at Orleans Canal South, which did not fail during the hurricane. The key factor of the failure mechanism of the London Avenue levees was the formation of a gap between the flooded side of the levee and the sheetpile. This gap triggered a reduction of the strength at the foundation of the protected side of the levee. The results are fully consistent with field observations. Gulf of Mexico, and the Mississippi River running through the southern portion of New Orleans. The levee system that surrounds the city protecting it from flooding experienced extensive damage during the hurricane, leaving roughly 80% of the city under water. Shortly after the hurricane, several multidisciplinary groups were formed with the goal to understand the causes of this disas- ter, in particular, the failure of the levee system. Many of those independent investigators visited New Orleans shortly after the hurricane to capture as much data and field observations as pos- sible before the levee failure sites were disturbed by ongoing emergency repair activities. The field observations described in this paper were taken from a report published about three months after Katrina and sponsored by the National Science Foundation Seed et al. 2005. All of the work reported in this paper was conducted as part of the evaluation performed by the U.S. Army Corps of Engineers USACE regarding the hurricane protection system in southeast Louisiana. That effort initiated by the Chief of Engineers for USACE was termed the Interagency Performance Evaluation Taskforce IPET. Part of that effort was a thorough analysis of the performance of the hurricane protection system. A component of that work was physical modeling of selected locations of the levee system, which is presented herein. The USACE provided critical information for the research presented in this paper, such as the pre-Katrina geometry of the levees and material properties, as well as storm surge water elevations and the general progres- sion of events during Katrina, which was later published in USACE 2006. This paper presents the results of 50g centrifuge physical mod- els of the performance of two levee sections at London Avenue and one levee section at Orleans Canal. The tests were conducted at the Rensselaer Polytechnic Institute RPI in Troy, N.Y., and the USACE, Engineer Research and Development Center ERDC in Vicksburg, Miss. Duplicate physical models of the levees reported in this paper were conducted at both facilities to

Centrifuge modeling of the 17th Street Canal and Orleans Canal North levees was performed in this study. During hurricane Katrina the levees on the 17th Street Canal failed, leading to breaches in the outfall canal in the city. Two mechanisms were observed in the centrifuge modeling that could cause a breach. First, a water-filled crack formed in front of the floodwall as the water in the canal rose above the top of the levee. The levees on the 17th Street Canal, which were supported on clay foundations, failed when this cracking led to a translational (sliding) failure in the clay layer commencing at the toe of the floodwall. The levees at Orleans Canal North, where failure did not occur, were also modeled to demonstrate that the model tests could successfully simulate failure and nonfailure conditions. The centrifuge model tests identified the importance of the crack formation in relation to the stability of the floodwall. These tests also confirmed that levee geometry, floodwall depth of penetration, and the underlying soil profile were all critical to the performance of the system under flood loading.