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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 relative performance of H2O and sCO2 as geothermal working fluids (GWFs) in liquid-dominated enhanced geothermal systems (EGSs) was investigated in this study. Such systems rely on the injection of GWFs (geothermal working fluids) to sustain geothermal energy recovery, which is dominated by conduction-based heat exchange from the rock to the GWF in the hydraulic fracture. H2O is currently the only GWF considered for EGS operations, but supercritical CO2 has been proposed as a potential GWF because of its lower density and viscosity, which lead to the hypothesis of potentially significant thermal energy recovery. However, H2O appears to have an initial advantage because of its significantly higher thermal conductivity. We compared the performance of H2O and SCO2 as GWFs in a 3D stencil (minimum repeatable element) of an EGS involving a hydraulic fracture connecting the injection and the production wells, the main body of the EGS rock that provides the heat source, and boundaries that are sufficiently distant from the main body of the main body of the rock to maintain constant pressure and temperature conditions over a 30-year period of EGS operations In our studies we considered variations in the initial reservoir temperature, in the injection method (at a constant-rate and at a constant bottomhole pressure) and in the reservoir permeability, in an effort (a) not only to compare the EGS performance of H2O and sCO2 as GWFs but also (b) to determine the conditions (if any) under which sCO2 can be more effective than H2O. The results of the study indicated the overwhelming superiority of H2O as a GWF under any and all of the conditions covered by the study, producing fluids at dependably much higher temperatures and yielding invariably drastically higher energy recovery than sCO2 despite the consistently higher GWF injection and production rates attained with sCO2. [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 [...]

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.

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.