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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]

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]

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.

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.

The VERT wall is a new type of top-down retaining wall, which derives its name from the fact that it is vertically reinforced. Typically, three to four rows of 1-m-diameter cemented-soil columns are constructed to the depth of soil to be retained. After curing of the cement, the soil in front of this gravity wall is excavated in one step. To study the viability of this new wall type, a 10-m-high, 40-m-long, and 5.6-m-wide VERT wall was built at the National Geotechnical Experimentation Site at Texas A&M University. The soil is a medium-dense silty sand, and the wall was instrumented for horizontal and vertical movement. One year after excavation the horizontal movement of the wall was 24.6 nun and the settlement was 9.3 mm. These values are very close to the movements of the similar size tieback wall built at the same site. This performance is an indication of the viability of this new wall type.

Three bored piles were built and tested at the National Geotechnical Experimentation Sites, at Texas A&M University, to gather data on the reliability of large-strain dynamic methods to predict the static capacity of bored piles. The three piles had a nominal diameter of 0.915 m, a nominal length of 10 m, and some planned and unplanned defects. The piles were first subjected to a static load test and then four companies were asked to perform dynamic tests - namely, Statnamic and drop weight tests - and predict the static load test results. The paper shows the comparison between predicted and measured results.

Five square spread footings ranging in size from 1 to 3 m were load tested up to 150 mm of settlement. They were all embedded 0.75 m into a medium dense, fairly uniform, silty silica sand. Load-settlement curves are presented, as well as creep curves relating settlement and time under a constant load. Since the soil mass was instrumented with telltales and inclinometers, vertical and horizontal movements in the soil mass were obtained as a function of depth and lateral extent. Conclusions are reached regarding how best to measure footing settlement, how to present load test results, new correlations for use in design, creep settlement, effect of cyclic loading and preloading on creep rate, zone of influence under the footing, mode of deformation of the soil mass, and volume change observations. Twelve settlement methods, six bearing capacity methods, and the WAK (wave activated stiffness) test are evaluated by comparing the predictions with the measurements. Many results of these large-scale instrumented tests confirm findings at small scale of previous researchers.

A new method called SRICOS is proposed to predict the scour depth z versus time t around a cylindrical bridge pier of diameter D founded in clay. The steps involved are: (1) taking samples at the bridge pier site; (2) testing them in an erosion function apparatus to obtain the scour rate z versus the hydraulic shear stress applied (tau); (3) predicting the maximum shear stress (tau)(sub max), which will be induced around the pier by the water flowing at (upsilon)(sub 0) before the scour hole starts to develop; (4) using the measured z versus (tau) curve to obtain the initial scour rate z(sub i) corresponding to (tau)(sub max); (5) predicting the maximum depth of scour z(sub max) for the pier; (6) using z(sub i) and z(sub max) to develop the hyperbolic function describing the scour depth z versus time t curve; and (7) reading the z versus t curve at a time corresponding to the duration of the flood to find the scour depth that will develop around that pier. A new apparatus is developed to measure the z versus t curve of step 2, a series of advanced numerical simulations are performed to develop an equation for the (tau)(sub max) value of step 3, and a series of flume tests are performed to develop an equation for the Z(sub max) value of step 5. The method is evaluated by comparing predictions and measurements in 42 flume experiments.

A three-dimensional nonlinear finite-element analysis is used to study the influence of various design decisions for tieback walls. The numerical model simulates the soldier piles and the tendon bonded length of the anchors with beam elements, the unbonded tendon with a spring element, the wood lagging with shell elements, and the soil with solid three-dimensional (3D) nonlinear elements. The soil model used is a modified hyperbolic model with unloading hysteresis. The complete sequence of construction is simulated including the excavation and the placement and stressing of the anchors. The numerical model is calibrated against an instrumented case history. Then a parametric study is conducted. The results give information on the influence of the following factors on the wall behavior: Location of the tendon unbonded zone, magnitude of the anchor forces, embedment of the soldier piles, and stiffnesses of the wood lagging and the piles. The implications in design are discussed.

Field measurements associated with the behavior of ten low-pressure grouted anchors installed with a hollow stem auger at the National Geotechnical Experimentation Site at Texas A&M University are presented. The anchors were 0.3 m in diameter and embedded 13.8 m in a stiff to very stiff clay. Six anchors had a tendon bond length of 4.6 m and four had a tendon bond length of 9.2 m. All anchors were load tested to near failure, some were subjected to creep tests, and some to long-term relaxation tests. This study evaluates the load distribution in the soil, grout, and steel tendon; the shear strength of the soil-grout interface compared to engineering soil properties; the relationships between the ultimate load, the creep failure load, the creep threshold load, and the design load; the creep movement rate under load; and the load loss as a function of time. The results show that anchors with shorter tendon bond lengths have higher ultimate capacities and lower creep rates, and transfer the load further away from the supported structure.

The beam-column method for the design of tieback walls is of intermediate complexity between the pressure diagram methods and the finite-element method (FEM). A set of recommended P-y, F-w, and Q-w curves are presented for the soil model and the P-y path method is described to simulate properly the construction sequence of excavation and tieback stressing. The recommended beam-column method is evaluated by comparing predictions with the measured behavior of four full-scale tieback walls in sand and in clay. The most influencing factors are identified through a parametric analysis and a comparison with four pressure diagram methods is presented. The beam-column method is a deflection-based method that satisfies the vertical, horizontal, and moment equilibrium of the wall. These significant and fundamental advantages over the pressure diagram methods make it a superior method, which should be used anytime the added complexity is warranted. The most severe limitation of the beam-column method is its inability to properly account for mass phenomena, namely, mass movement and downdrag. The most useful aspect of the beam-column method is its ability to give better bending moment profiles than the pressure diagram methods.

Bitumen has been shown to reduce significantly the downdrag load on piles. The problem is to know how to choose the fight bitumen for the job. The right bitumen must not deform excessively under gravity stresses during the storage period, must not deform excessively under dynamic stresses due to pile driving, must offer little shearing resistance and therefore downdrag during the soil settlement process, and must not let the soil particles penetrate excessively into the coating. Rational design approaches are developed for each of the four criteria on the basis of the fundamental behavior of bitumen, full-scale downdrag tests on 15 piles at a Northern and Southern site, and a series of laboratory tests. Guidelines are presented for the bitumen selection process and tips are given for the field application of the bitumen coating.

A three-dimensional (3D) nonlinear finite-element analysis is used to study the behavior of soil-nailed walls constructed under a bridge abutment built on piles. The numerical model simulates the piles and the nails with beam elements, the abutment and the pile cap with solid 3D brick elastic elements. The soil model used is a modified hyperbolic model with unloading hysteresis. The complete sequence of construction is simulated including the excavation of the embankment slope under the bridge in front of the abutment and the placement of the nails. The numerical model is calibrated against an instrumented case history. Then a parametric study is conducted. The results give information on the effect of the excavation and nail placement on the following: axial load and bending moment in the piles and load in the nails and wall deflections. The results are used to suggest design guidelines.

The problem of a pile subjected to lateral loading is often solved by assuming that the pile is an elastic member and that the soil can be represented by a series of nonlinear horizontal springs. The P-y curves describe the nonlinear behavior of the soil springs. Previously, a method was developed at Texas A&M University to obtain the P-y curve directly from the pressuremeter curve. This method gave good predictions but was complicated and time consuming. Simple approach for lateral load on piles (SALLOP) is a simplification of the complicated method; it makes use of the pressuremeter limit pressure and the pressuremeter modulus. It is a semitheoretical or semiempirical method in that the framework is theoretical but the factors in the theoretical equations are adjusted by comparison to 20 full-scale load tests. The accuracy of SALLOP is very reasonable as shown by comparing measured and predicted behavior for the 20 full-scale pile load tests used to develop the method.

There is ice in the Gulf of Mexico, and this type of ice called gas hydrates burns when ignited. Gas hydrates form slowly within the soil mass when the gas seeping up from offshore oil reservoirs mixes with water under high pressures (>500 m of water) and low temperatures (a few degrees Celsius). The oil travels from the well to the platform through a conductor pipe. The oil and therefore the conductor are very hot and melt the existing hydrates that are within the depth of the foundation piles. The melting process generates a large amount of gas that can endanger the stability of the foundation. The rate at which the temperature rises around the hot conductor in the hydrate rich soil is studied using the finite-element method (FEM). A detailed thermodynamic analysis is performed. It includes a laboratory experiment to help validate FEM, a study of the mesh size, the thermodynamic analysis results, a study of the conductor size, and of the latent heat influence. The results can be used to evaluate the temperature rise around a hot pipe buried in soil and therefore the propagation of the hydrate melting front around the conductor and toward the piles.

Coating piles with bitumen down to their neutral points to debond them from embedding soil is a feasible method to minimize the adverse effects of negative skin friction. Bitumen is a petroleum product composed of numerous extremely complex organic compounds including polycyclic aromatic hydrocarbons (PAHs) that have been identified by the U.S. Environmental Protection Agency (EPA) as toxic and carcinogenic materials. To investigate the engineering behavior of bitumen-coated piles under extreme weather conditions, full-scale field tests were performed in New Orleans, Louisiana, and Edmonton, Alberta, Canada. Instrumented piles were installed at these sites from 1989 to 1990. This paper presents the results of geoenvironmental field investigations performed at these sites to determine the spatial distribution of target PAHs in the subsurface after the piles had been installed for 2-3 1/2 yr. The findings of the investigation indicate that subsurface contamination, if there is any, caused by the installation of bitumen-coated piles is well within acceptable limits.

The LATWAK test consists of hitting in the horizontal direction the side of a pile on which a horizontal velocity transducer is attached. The blow is delivered with a sledge hammer equipped with a dynamic force transducer. The force time signal from the hammer (input) and the velocity time signal from the pile (output) are recorded during the impact. The experimental mobility curve is obtained as a function of frequency by calculating the modulus of the complex valued ratio of velocity over force using Discrete Fourier Transforms. Theoretically it is assumed that the pile is an elastic member with mass and that the soil can be represented by linear springs and viscous damping. The problem of the steady state forced vibration of the pile in such a soil is solved mathematically. It leads to the theoretical mobility curve for the pile-soil system. The experimental mobility curve obtained in the LATWAK test on the pile is matched with the theoretical mobility curve. A system identification technique is used to match the two curves and to extract the best-fit model parameters, which include the static lateral stiffness K for the pile-soil assembly. To evaluate the usefulness of the method, the lateral stiffness [K.sub.p], predicted by the LATWAK test on a pile was compared to the lateral stiffness [K.sub.m] measured in a static lateral load test on the same pile. A total of 20 pile load tests and 20 LATWAK tests were performed and used to compare [K.sub.p] and [K.sub.m]. The results are encouraging.

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]

The best current highway engineering practice in minimizing the formation of interface bumps between bridge abutments and embankments involves a combination of good design and construction techniques with adequate maintenance procedures that meet budget requirements and safety regulations. There are ten points to consider in minimizing the formation of such costly bridge hazards. The most important is that design factors should be thoroughly evaluated in the construction of bridges.

Stiffened slabs-on-grade are one of the most economical solutions for 1- to 3-story buildings on shrink-swell soils. They consist, for example, of 1-m-deep, 0.3-m-wide beams resting on the soil, spaced 4 m apart in both directions covered by a 0.1-m-thick slab-on-grade. The challenge is to optimize the beamdepth, width, and spacing for the slab to be stiff enough that themovement of the soil at the edges of the slab will not cause undue bending of the foundation and the structure above it. Indeed, shrink-swell soils are affected by the weather and/or by the irrigation at the edges of the foundation and will swell and shrink as a result. This article presents a new method to design stiffened slabs on grade such that the differential movement divided by the length over which this movement takes place is within tolerable limits. The method gives the beam depth necessary to achieve such stiffness as well as the bending moment and shear force to be resisted. The method is automated in a spreadsheet called TAMU-SLAB. [ABSTRACT FROM AUTHOR]

A component of geotechnical applications involving nonisothermal conditions is the determination of the thermal properties of the ground. This paper presents a new test, called the thermal cone dissipation test (TCT), which overcomes most of the drawbacks observed in current in-situ techniques used to determine the thermal properties of soils. The equipment consists of a cone penetrometer equipped with thermocouples located behind the cone point. The TCT is pushed in the ground at the standard penetration rate of 2 cm/s, and the friction between the cone and the soil increases the cone temperature. The temperature decay is recorded as a function of time (for approximately 30 min) and this information is used to estimate the thermal conductivity and other thermal properties of soils. The calibration of the curves proposed in this work to estimate the thermal properties of the ground was based on three main activities: (1) in-situ experiments, carried out at three different locations involving different soil types; (2) laboratory investigation, aimed at obtaining the thermal conductivity of the soils studied in the field; and (3) numerical simulations, used to validate the proposed numerical models against the experimental data and to populate the proposed calibration curves including ground conditions to explore in the field. Very good agreements between field, laboratory and numerical results were obtained for the 11 TCTs studied in this research. It is expected that the proposed calibration curves will be enhanced in the future as additional experimental data become available. [ABSTRACT FROM AUTHOR]

Shrink-swell soils can cause distresses in buildings, and every year, the economic loss associated with this problem is huge. This paper presents a comprehensive system for simulating the soil-foundation-building system and its response to daily weather conditions. Weather data include rainfall, solar radiation, air temperature, relative humidity, and wind speed, all of which are readily available from a local weather station or the Internet. These data are used to determine simulation flux boundary conditions. Different methods are proposed to simulate different boundary conditions: bare soil, trees, and vegetation. A coupled hydro-mechanical stress analysis is used to simulate the volume change of shrink-swell soils due to both mechanical stress and water content variations. Coupled hydro-mechanical stress-jointed elements are used to simulate the interaction between the soil and the slab, and general shell elements are used to simulate structural behavior. All the models are combined into one finite element program to predict the entire system's behavior. This paper first described the theory for the simulations. A site in Arlington, Texas, is then selected to demonstrate the application of the proposed system. Simulation results are shown, and a comparison between measured and predicted movements for four footings in Arlington, Texas, over a 2-year period is presented. Finally, a three-dimensional simulation is made for a virtual residential building on shrink-swell soils to identify the influence of various factors. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Scour is the removal of soil around bridge supports due to water flow during floods. One of the major problems with scour is in the case of unknown bridge foundations. Bridges with unknown foundations are listed in the National Bridge Inventory as having insufficient data for scour evaluation, particularly regarding foundation depth. Knowing the foundation depth is a critical component of scour risk assessment. Multiple nondestructive testing methods are currently used to determine the depth of unknown bridge foundations; however, many methods are hindered by the type of substructure. An advantage of using near-surface geophysical methods, specifically electrical resistivity (ER) and induced polarization (IP) imaging, is that the inversion processes yield subsurface images, thereby allowing the depth and, to a lesser extent, the foundation type to be seen. Unlike a majority of existing testing methods, ER and IP imaging do not physically use the structure so they are applicable to simple and complex foundation structures. In this paper, results of ER and IP imaging tests performed at the Texas A&M University National Geotechnical Experimentation Site, on a bridge with known foundation depth and a bridge with unknown foundation depth are presented. The applicability of ER and IP imaging to determine substructure characteristics for unknown bridge foundations is also discussed. A probability of nonexceedance estimate for predictions using IP is given to quantify IP imaging reliability. [ABSTRACT FROM AUTHOR]

Scour of the soil by flowing water around bridge supports is the number one reason for bridge collapse. Predicting the depth of the scour hole is an integral part of bridge foundation design, as it impacts the depth of the piles. Indeed, the scour depth must be ignored in the vertical and horizontal resistance of the piles. This paper presents a method to predict the progression of the scour depth around bridge supports as a function of time when subjected to a velocity hydrograph. It also addresses the issue of layered soils. The equations make use of the commonly used water velocity and dimensions of the obstacle, but add a new and important component: the soil erosion function to characterize the degree of soil resistance to erosion. The equations apply to pier scour, contraction scour, and abutment scour. The predicted output is the scour depth as a function of time for a given velocity hydrograph and soil layer stratigraphy. A comparison between measured and predicted scour depth is presented, but more comparisons are necessary, particularly at full scale. [ABSTRACT FROM AUTHOR]

Scour of the soil by flowing water around bridge supports is the number one reason for bridge collapse. Predicting the depth of the scour hole is an integral part of the bridge foundation design, as it impacts the depth of the piles. Indeed, the scour depth must be ignored in the vertical and horizontal resistance of the piles. This paper presents a method to calculate the maximum depth of the scour hole around bridge supports when subjected to a constant water velocity. Most existing methods take into account the water velocity and the geometry of the obstacle but not the soil type. The method presented in this paper keeps those important variables and adds the paramount influence of the soil erosion characteristics. It is developed on the basis of 94 flume tests, some of them very large laboratory-scale tests, as well as dimensional analysis and experience. It applies to pier scour, contraction scour, and abutment scour. The method is evaluated by comparing the maximum scour depth predictions against measured data from 10 databases of pier, contraction, and abutment scour depths. [ABSTRACT FROM AUTHOR]