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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.