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In mining, open pits have slopes cut as steep as possible to ensure efficient mining yet not too steep to jeopardize safety. Building on existing contributions, the Texas A&M University Mine Slope database (TAMU-MineSlope) was created to provide global-scale insights into the runout mechanics of open pit slope failures and offer the database to engineers for further study. The database includes 134 cases of open pit slope failures that occurred at 76 mines worldwide. Based on energy principles and an analysis of the TAMU-MineSlope data, an equation to predict the travel distance of the slope failure mass is presented in this paper. Furthermore, based on the case histories analysis, an equation to predict the setback distance is proposed. Finally, the TAMU-MineSlope database shows that the average width to height ratio of the failing slope mass is 2.7 and that, for this ratio, the 3D factor of safety (FS) can reach a value 15% higher than the 2D FS. The database has been released in the public domain. Key words: slope stability, open pit slope failure database, travel distance, setback distance, three-dimensional analysis, 1. Introduction One of the major problems in open pit mining geotechnics is slope stability. The slopes of these large and deep excavations must be as steep as possible to [...]

The stability of slopes is typically evaluated by two-dimensional plane strain analysis. However, many slopes exhibit three-dimensional (3D) geometries, including slope corners. Several researchers have studied the stability of slope corners but found that the factor of safety (FS) was close to the FS for the plane strain case. The results of a new series of 3D finite element method (FEM) simulating slope corners, including slope angle, plan view angle, radius of curvature, and slope height are presented. They confirm that the FS does not vary much for corners compared to the plane strain case. However, 220 cases using an elastic-perfectly plastic soil model together with the FEM shear strength reduction method show that the displacement field is very different at the corners compared to plane strain with differences reaching over 100%. The displacement ratio between corners and plane strain is presented as a function of the plan view angle of the corner. Often failure is defined at a chosen large displacement, as in the ultimate load of foundation elements. If this concept is carried over to slope stability, it would indicate that the FS of corners should be very different from the plane strain case. A possible explanation is discussed. [ABSTRACT FROM AUTHOR]

The tragic consequences of vehicles running into infrastructures have raised the need for perimeter protection. One common perimeter barrier is a set of piles or posts in an in-line geometry as an efficient way to contain or redirect errant vehicles. To date, the design of such barriers relies mostly on performing full-scale crash tests. These crash tests are expensive, and it is often practical to run such tests. In this paper, a general yet simple analysis-design model called TAMU-POST was developed to predict the response of a group of in-line piles impacted by a vehicle. TAMU-POST is based on the finite difference solution to the governing differential equation for a beam supported by piles. The piles are represented by single degrees of freedom consisting of a dashpot, a lumped mass, a spring, and a slider. A large number of computer simulations using a non-linear finite element program LS-DYNA as well as the data obtained from two full-scale crash tests were used to calibrate the proposed model. The design quantities are the barrier deflection, the vehicle dynamic penetration defined as the maximum vehicle intrusion into the barrier, as well as other parameters including the bending moment in the piles and in the beams. A Monte Carlo Simulation analysis was conducted using TAMU-POST to evaluate the probability of failure of a group of in-line piles under a given vehicular impact when considering the inherent uncertainties associated with the input parameters and the model coefficients.

River meanders migrate over time and the consequences of this migration can create a problem for bridges and embankments near the river. This is why it is important to predict the lateral extent of future migration over the life of neighboring infrastructure. In the observation method for meander migration (OMM), the past movement and velocity history of the meander are used to back-calculate site specific erosion parameters. Those parameters serve as input to predict the meander migration for a chosen future velocity hydrograph. In this article and after a review of existing knowledge, the analytical steps leading to the development of the OMM are described, then the field and laboratory work at four full-scale meander migration case histories are presented, and then the four full-scale meander migration case histories are used to evaluate the OMM. The OMM has been automated in an Excel spreadsheet. Key words: meander, migration, erosion, soil, case histories, observations, prediction. Les meandres de riviere ou de fleuve migrent au fil du temps et les consequences de cette migration peuvent creer un probleme pour les ponts et les digues pres de la riviere ou du fleuve. C'est pourquoi il est important de prevoir l'etendue laterale de la migration future au cours de la vie des infrastructures voisines. Dans la methode d'observation de la migration des meandres (OMM), le mouvement passe et la vitesse du meandre au fil du temps sont utilises pour calculer les parametres de l'erosion specifique au site. Ces parametres servent de donnees d'entree pour predire la migration des meandres pour un hydrogramme de vitesse futur choisi. Dans le present article et apres un examen des connaissances existantes, les etapes analytiques menant au developpement de l'OMM sont decrites, puis le travail sur le terrain et en laboratoire concernant quatre cas concrets de migration de meandres a l'echelle reelle sur differentes periodes d'observation est presente, puis les quatre cas concrets de migration de meandres a l'echelle reelle sont utilises pour evaluer l'OMM. L'OMM a ete automatise dans une feuille de calcul Excel. [Traduit par la Redaction] Mots-cles: meandre, migration, erosion, sol, cas concrets, observations, previsions., Introduction River meanders migrate over time in a very complex fashion (Fig. 1). The consequences of this migration can create a problem for bridges and embankments near the river. This [...]

This paper presents the results of research on soil erosion and its mitigation by different methods such as grass, riprap, lime, and enzymes. The goal was to evaluate these methods for their degree of efficacy using laboratory erosion testing. The paper begins with a review of existing knowledge on erosion mitigation methods. The erosion resistance of natural and improved soil was investigated in the erosion function apparatus (EFA), a laboratory device for measuring erosion resistance in the velocity range of 0.3 to 6.5 m/s. EFA testing was performed on grass-covered soils, riprap-covered soils, enzyme-treated soils, and lime-treated soils. The erodibility of the soils before and after treatment was compared. The results of the EFA tests were also compared with a few large-scale field tests available in the published literature. The advantages, limitations, and range of applications of each erosion mitigation method are provided. [ABSTRACT FROM AUTHOR]

The main objective of this paper is to develop equations correlating the erosion resistance of a soil to its common geotechnical properties. A total of 975 erosion tests and approximately 13,600 associated common geotechnical properties were organized in a database called Texas A&M University (TAMU)-Erosion. About 300 of the 975 erosion tests and approximately 4,200 associated common geotechnical property tests were performed at Texas A&M University over the past 20 years. In parallel, an additional 675 erosion tests and approximately 9,400 corresponding common geotechnical properties were collected from the open literature. The erosion tests include mostly the erosion function apparatus test (EFA), jet erosion test (JET), and hole erosion test (HET). The raw data for all tests are embedded in TAMU-Erosion, along with an inquiry operation manual that allows the user to search the database. This database was used along with a standard statistical regression method and a probabilistic representation to develop the best equations correlating the erodibility parameters to the geotechnical properties. The best fit for each equation was quantified using standard goodness of fit indices. The best equations are presented along with probability curves conveying to the user the probability that the predicted value will be overpredicted or underpredicted. [ABSTRACT FROM AUTHOR]

A set of large-scale laboratory experiments were conducted to study the migration of meandering channel. Factors affecting the change of banklines, including the ratio of centerline curvature to channel width, bend angle, and Froude number were tested in the experiments. The effect of each factor on the evolution of channel plan form was evaluated and quantified. The channel bankline displacement was modeled by a hyperbolic function with the inclusion of the initial migration rate and the maximum migration distance. A three-dimensional numerical model was also employed to explain some findings in the laboratory tests. It is found that the maximum migration distance along a bend satisfies a Gaussian distribution. A set of equations were developed for predicting the maximum migration distance. With the maximum migration distance being developed as a function of several geometric and flow parameters, a hyperbolicfunction model can be applied to estimate the maximum bankline migration distance when the channel reaches equilibrium. DOI: 10.1061/(ASCE)HY. 1943-7900.0000050 CE Database subject headings: Rivers; Meandering streams; River bank erosion; Secondary flow; Sand; Open channel flow.

The computational fluid dynamics (CFD) solver FANS3D [Finite-Analytic Navier-Stokes code for three-dimensional (3D) flow] is coupled with a sediment transport model to simulate scour hole backfilling under unidirectional flows (current-only). FANS3D solves 3D, unsteady, incompressible Navier-Stokes equations in nonstaggered, general curvilinear coordinate systems. For the present study, the k-ε model is used for turbulence closure. The overset grid technique is utilized to generate the computational domain consisting of multiple blocks with different structures. The coupled model is validated with both clear-water and live-bed scour experiments. The numerical solution is also verified to be consistent against changes in time step size and grid density. Backfilling is initiated by first obtaining the equilibrium scour under a "flood" and then reducing the approach velocity to a "normal" flow, both of which conditions are in a live-bed scour regime. Using this approach, backfilling is successfully simulated around a cylindrical pier with three different hydrographs (variable velocity). The backfilled scour hole is compared with the equilibrium scour hole formed under normal flow (constant velocity). This study found that a given unidirectional flow velocity results in the same equilibrium scour depth regardless of the initial bed morphology. The location of the maximum depth inside the scour hole is also found to be a characteristic of the flow velocity. [ABSTRACT FROM AUTHOR]

This lecture presents four case history examples of erosion processes. Because the topic of soil and rock erosion is relatively underdeveloped in geotechnical engineering, an introduction precedes the case histories to describe some fundamental aspects of erosion. Erosion involves the soil or rock through its erodibility, the water through its velocity, and the geometry of the obstacle through its size and shape. Knowledge of these three components is needed for any erosion problem to be studied and solved. A set of fundamental issues are addressed in the first part including an erodibility classification for soils and rocks, an explanation of the stresses imposed by the water on the soil-water or rock-water interface, and an explanation of how the geometry impacts the problem. The Woodrow Wilson Bridge case history outlines a new and less conservative method to compute the scour depth and gives examples of bridge scour calculations. The Brazos River meander case history outlines a new method to predict meander migration and gives an example of migration calculations. The Pointe du Hoc case history gives an explanation of a process of rock cliff erosion. The New Orleans levees case history gives an example of erosion of levees by overtopping and proposes an erosion design chart for levee overtopping. Whenever possible the results are presented in a probabilistic fashion. All case histories make use of the erosion function apparatus, an apparatus developed to quantify the erodibility of a soil or rock and to give the constitutive law for erosion problems: the erosion function. The power point slides for the lecture including many photos of the case histories are available at under 'Lectures' and the video (DVD) of the lecture is available from the author, free of charge. CE Database subject headings: History; Erosion; Bridges; Levees; Cliffs; Rivers; Washington, D.C.; France; Louisiana; Texas.

Constitutive surfaces are indispensable for investigation of the behavior of soils. Saturated and unsaturated soils coexist in most engineering problems and it is meaningful to develop constitutive surfaces covering both saturated and unsaturated conditions which help to investigate the behavior for both saturated and unsaturated soils in a unified way. At present, the methodologies used for saturated and unsaturated soils are different and few researchers consider the constitutive surfaces for saturated soils. For unsaturated soils, the suction-controlled triaxial tests are usually laborious, time consuming, costly, and may not justify routine engineering projects. This paper discusses the role of constitutive surfaces in soil mechanics and presents an improved approach over existing interpolation methods to construct the constitutive surfaces for saturated and unsaturated conditions for a stable-structured soil using simple laboratory tests. CE Database subject headings: Void ratio; Saturated soils; Unsaturated soils; Laboratory tests; Surface properties.

Scour at a bridge pier is the formation of a hole around the pier due to the erosion of soil by flowing water; this hole in the soil reduces the carrying capacity of the foundation and the pier. Excessive scour can cause a bridge pier to fail without warning. Current predictions of the depth of the scour hole around a bridge pier are based on deterministic models. This paper considers two alternative deterministic models to predict scour depth. For each deterministic model, a corresponding probabilistic model is constructed using a Bayesian statistical approach and available field and experimental data. The developed probabilistic models account for the estimated bias in the deterministic models and for the model uncertainty. Parameters from both prediction models are compared to determine their accuracy. The developed probabilistic models are used to estimate the probability of exceedance of scour depth around bridge piers. The method is demonstrated on an example bridge pier. The paper addresses model uncertainties for given hydrologic variables. Hydrologic uncertainties have been presented in a separate paper. DOI: 10.1061/(ASCE)1090-0241(2008)134:2(175) CE Database subject headings: Bridges, piers; Scour; Probability; Estimation.

Shrink-swell soils are characterized by significant volume expansions and contractions during wetting and drying processes, respectively. Railroads on shrink-swell soils are subjected to huge solicitations associated with the volume change of the soil. The highly permeable ballast layer exacerbates soil volume changes due to moisture variation, which generally lead to unacceptable uneven settlement. The mechanism behind the observed railroads problems on expansive soils, and the associated (possible) remedial solutions, are still unclear. A site in Texas has been chosen recently to study in detail the aforementioned problems. In this paper, the typical geomechanical problems associated with railroads on shrink-swell soils in Texas are discussed. We also presented the test site information and preliminary lab tests to obtain water retention curve of the site soils.

The paper presents a study on erodibility of soil above the groundwater level where the water is in tension. Such soils particularly clays are very sensitive to moisture and temperature changes and can be eroded significantly by water flow. The erosion of clay and sand samples from the US National Geotechnical Experimentation Site at Texas A&M University is studied. Two sets of experiments are done with the clay and the sand. The first set was performed on sample collected in November 2014 and the second set on samples from June 2014. The depth of the samples varied from 0.6 to 3.6 m where water content and density changes. A series of erosion tests was performed in the Erosion Function apparatus (EFA) with the intact clay and then with the sand reconstructed to the field density and field water content. The erosion tests are performed at different flow velocities varying from 0.5 m/s to 5.5 m/s. The erodibility is quantified by the relationship between the erosion rate and the water velocity called the erosion function. Some relationships between the critical velocity and common soil properties are discussed. The collapse of the clay structure when inundated (soaking) is studied.

The San Jacinto Monument was built in 1936 to commemorate the 100-year anniversary of the victory of the Texan army over the Mexican army. The victory at the battle of San Jacinto followed the defeat at the battle of the Alamo and secured the independence of Texas, as well as several other states along the Mexican border. The monument consists of a 176.5-m-high column resting on a large square mat with each side=37.8 m. The mat foundation was designed by Raymond Dawson who chose an average pressure of 223.8 kPa under the mat. Dawson had settlement points placed on the mat foundation together with benchmarks away from the monument. The settlement of the monument has been recorded over the last 70 years and shows a total settlement to date of 0.329 m. The settlement appears to be almost complete. This remarkable case history is used to evaluate current practice of calculating consolidation settlement and a best approach is suggested for such structures. Other issues addressed include the depth of influence, the time rate of settlement, the elastic-modulus approach, and the ultimate bearing capacity. DOI: 10.1061/(ASCE)1090-0241 (2007) 133: 11(1337) CE Database subject headings: Mat foundations; Foundation settlement; Soil consolidation; Case reports; Monuments; Texas.

A study of the assumptions involved in the ultimate bearing capacity equation indicates the shortcomings of that equation and load test data confirm these shortcomings. A new approach using a normalized load settlement curve is proposed to alleviate these shortcomings and to obtain the complete load settlement curve for a footing in sand. The normalization consists of plotting the mean footing pressure divided by a measure of the soil strength within the depth of influence of the footing versus the settlement divided by the footing width. It is shown that the normalized load settlement curve for a footing is independent of footing size and embedment. It is proposed to obtain the normalized curve point-by-point from a soil test. Because the deformation of the soil observed under full-scale footings during loading indicates a barreling effect similar to the soil deformation around a pressuremeter probe, the preboring pressuremeter curve is used to obtain the footing curve. The new method consists of transforming the preboring pressuremeter curve point-by-point into the footing load settlement curve. Load tests and numerical simulations are used to propose a method for a rectangular footing near a slope subjected to an eccentric and inclined load. The new method gives the complete load settlement curve for the footing and alleviates the problems identified with the bearing capacity equation. CE Database subject headings: Sand; Spread foundations; Bearing capacity; Foundation settlement; Load tests; simulation; Curvature.

Damage to bridge crossings during flood events endangers the lives of the traveling public and causes costly disruptions to traffic flow. The most common causes of bridge collapse are scouring of the streambed and banks and erosion of highway embankments. This study couples a synthetic river flow simulation technique with a scour model for cohesive soils and determines the expected scour depth for a given lifetime of the bridge. A fractionally differenced autoregressive integrated moving average model generates synthetic streamflow sequences of the same length as the expected lifetime of the bridge. The scour model predicts the progression of scour depth through time in a multilayered soil. The model is used to determine the scour depth associated with different replicates of the synthetic flow sequences of the same length as the lifetime of the bridge. The probability distribution of scour depth is estimated by repeating this simulation procedure over a number of independent realizations of streamflow series for a given life of the bridge. This approach provides a framework for the probabilistic design and risk analysis of bridge foundations subjected to scour. DOI: 10.1061/(ASCE)0733-9429(2006)132:5(493) CE Database subject headings: Bridges, piers; Scour; Cohesive soils; Stochastic processes; Risk management.

There is a trend toward using the modulus as an alternative to dry density in compaction control because of the undesirable nuclear source in the current field density gage and because a modulus is often used in the design of roadway bases and compacted fills. The Briaud compaction device (BCD) is a new instrument used to obtain a soil modulus in only a few seconds; it consists of leaning on a rod equipped with a thin circular metal plate at the bottom end and recording the bending of that plate under a standard load. This article describes the theory and the experiments that have been performed to validate the new instrument. This validation is based on a comparison to a simple plate test and on a numerical simulation of the BCD test. A recommended procedure is outlined in the conclusions. The BCD is used in the lab on top of the soil in the Proctor mold to obtain the lab modulus versus water content curve and select a target value. Then the BCD is used in the field to verify that the target modulus has been achieved. DOI: 10.1061/(ASCE)1090-0241(2006)132:1(108) CE Database subject headings: Soil compaction; Soil water; Water content; Soil modulus

A new method is proposed to estimate the vertical movement of the ground surface for soil that swells and shrinks due to variations in water content. The water content is used as the main soil parameter and a shrink test is suggested to obtain the relationship between the change in water content and the volumetric strain induced. We propose estimating the change in water content and the depth of seasonal moisture changes from local databases or from existing techniques. The method is evaluated by comparing the predicted movement and the measured movement of four full-scale spread footings over a period of 2 years. CE Database subject headings: Shrinkage; Swelling; Water content; Predictions.

By 2005, approximately 60,000 bridges throughout the US were identified as having unknown foundations. The Federal Highway Administration (FHWA) required Departments of Transportation (DOTs) across the US to evaluate the safety of these bridges, in particular against scour failure, and reclassify them in the National Bridge Inventory (NBI). A probabilistic methodology is developed in this study to predict the type, embedment depth, and dimensions of unknown bridge foundations and to rigorously quantify the uncertainty of the predictions. This methodology uses artificial neural networks (ANNs) to predict the expected values of bearing capacity (BC) using available information on bridge loading, soil strength, location, and year built, among other parameters. The unknown foundation characteristics are then evaluated using the Bayesian inference method and Markov chain Monte Carlo (MCMC) simulations, based on the predicted BC by the ANN models. The proposed method was validated based on a case study and proved successful in providing reasonable estimates on minimum foundation embedment depth for scour failure risk assessments. Transportation management authorities could adopt this method to reclassify bridges with unknown foundations and to implement risk based decision making approaches for bridge management. [ABSTRACT FROM AUTHOR]

Summary: Railroad track problems have been exacerbated by the continuous increase in freight loads and train traffic. The need to implement soil improvement technique in a relatively short window‐time (ie, to minimize train‐traffic disruption) is a key aspect to be considered when adopting a convenient remedial solution to control settlements in railroads constructed on problematic subgrades. Rigid inclusions are selected in this paper because they are reliable solutions relatively easy to implement. Furthermore, they can be used in different ground conditions and are suitable for short construction times (eg, do not require a curing time, as in grouting methods). Typical (analytical) methods for the design of rigid inclusions are adopted in this paper to define an optimal distribution of piles for the case of existing railroads. The selected layout is then analyzed in detail by means of a 3‐D dynamic finite element simulator using both, elastoplastic and elastic models. The performance of rigid inclusions is studied considering different operational scenarios, with dynamic and static loads, as well as involving subgrades with different plasticity index values. It is found that the predictions from the analytical design methods for rigid inclusion tend to be unconservative when compared against the finite element results. As for the numerical solutions, the most unfavorable stress condition is associated with the dynamic elastoplastic finite element solution. It is estimated that the rigid inclusions will contribute to a reduction in the ground settlements of around 15% to 20%, depending on the subgrade plasticity index. [ABSTRACT FROM AUTHOR]

Soil erosion is a major problem in civil engineering. It is involved in bridge scour, meander migration, levee overtopping, internal erosion of earth dams, surface erosion of embankments, and cliff erosion. The best way to predict the erodibility of a soil is to measure it directly on a site-specific basis by in situ testing in the field or by testing samples in the laboratory. The borehole erosion test (BET) is a new in situ soil-erosion test proposed to measure the erosion of the walls of a borehole while wet rotary drilling takes place. The increase in diameter of the borehole is measured with borehole calipers as a function of time and for a given flow velocity. The result is a profile of soil erodibility as a function of depth. Tests in clay and in sand conducted at the National Geotechnical Experimentation Sites at Texas A&M University are presented and compared with laboratory soil-erodibility tests with the erosion function apparatus (EFA) on samples taken from the same borehole. Computational fluid dynamics (CFD) numerical simulations of the velocity and shear stress field for the BET are also presented. The experimental and numerical results show the lessons learned and lead to an evaluation of the advantages and drawbacks of this new test. [ABSTRACT FROM AUTHOR]

The problem of the bump at the transition between the embankment and the bridge is an important concern for railways and highways. These bumps can lead to a rough riding surface which creates discomfort at high speed and high maintenance costs. The current study addresses the problem for High Speed Trains (HST). One reason for the development of a bump is the difference in stiffness between the compacted soil embankment and the bridge typically resting on deep foundations. A 4-D finite element model, developed in LS-DYNA, was used to simulate the effect of this difference in stiffness at the transition between the embankment and the bridge. The modulus of the embankment is varied from 5 MPa for a very soft embankment to 120 MPa for a very stiff embankment. The bridge is considered to be rigid by comparison. This study will show that the dynamic amplification factor, DAF, defined as the ratio of the maximum dynamic rail/wheel impact force to the static load on the wheel, changes dramatically with the embankment modulus and train speeds. [ABSTRACT FROM AUTHOR]

Groups of in-line piles connected by beams are being used to contain errant vehicles for roadside safety and perimeter protection of sensitive infrastructure. The effectiveness of in-line groups of piles to safely redirect or stop approaching vehicles has not been well investigated from the geotechnical point of view. In this paper, the performance of barriers is examined through full-scale crash tests and numerical simulations. The full-scale crash tests consisted of two different configurations of piles and beams as well as two different soil types: one was in loose sand and the other in hard clay. Both barriers were subjected to vehicle impact: one by a medium-duty truck and the other by a pickup truck. The barriers successfully contained the impacting vehicles. Detailed finite-element models of the barriers and the soil were developed and combined with the vehicle models to simulate the dynamic events. Comparison between predicted and measured behavior was used to calibrate the models. Additional simulations were performed to evaluate the effect of major structural and geotechnical design parameters including soil strength, pile spacing, and number of piles on the impact response of these systems. Practical recommendations are drawn from the experimental and numerical work. [ABSTRACT FROM AUTHOR]

Stiffened slabs-on-grade are one of the most efficient and inexpensive foundation solutions for lightweight structures on shrinkswell soils. The Ellison Office Building (EOB) is a 1-story steel-framed building founded on a clay formation of high shrink-swell potential. The foundation system of the EOB is composed of a rectangular stiffened slab-on-grade with approximate dimensions of 18.3 by 38.1 m. The slab thickness is 0.1 m, and the depth of all stiffening beams is 1.05 m. Beam spacing distances, center to center, are 3.05 and 3.81 m in the short and long directions, respectively. Exploration of subsurface soil conditions at the EOB site took place to determine soil index properties as well as unsaturated moisture diffusion and volume change characteristics for unsaturated soils. Monitoring the movements of both the slab-on-grade and the 4.5 m soil underneath continued for 2 years after foundation construction, since September 2004. Investigating the EOB foundation performance in light of the soil-structure interaction characteristics of the foundation showed two main distinct slab movement patterns: continuous global heave and localized fluctuating slab edge heave and drop movements. [ABSTRACT FROM AUTHOR]