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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 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 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.

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.