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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]

Post-Katrina investigations revealed that most earthen levee damage occurred on the levee crest and land-side slope as a result of either wave overtopping, storm surge overflow, or a combination of both. This study addresses erosion resistance performance of a levee strengthening technique-high performance turf reinforcement mat under combined wave and surge overtopping conditions using full-scale flume tests as well as erosion function apparatus (EFA) tests. Based on the results of full-scale flume tests, an 'upper limit' of soil loss is observed for certain flow conditions. Erosion rate was presented as a function of velocity and freeboard. The effect of duration of overtopping on the erosion depth is also determined. The results of EFA tests indicate that the presence of grass roots substantially improve the critical velocity and soil erodibility. [ABSTRACT FROM AUTHOR]

Bridge scour is the loss of soil by erosion because of water flowing around bridge supports. Scour has been the number one cause of bridge failure in the United States with an average annual rate of 22 bridges collapsing or being closed owing to severe deformation. This paper addresses three topics related to bridge scour. First, a set of databases was used to quantify the statistical parameters associated with the scatter between the predicted and measured pier scour depth, as well as the probability that a deterministically predicted pier scour depth will be exceeded. These databases also were used to provide the bias factors in current predictions. Secondly, these statistical parameters were used to develop a reliability-based load and resistance factor design for shallow and deep foundations subjected to scour. The goal was to provide a design procedure where the reliability of the foundation is the same with or without scour. Reliability only addresses the probability of success and, therefore, of failure. Finally, the discussion was broadened by using the concept of risk defined as the probability of failure times the value of the consequences. In this third part, the risk associated with bridge scour was quantified and compared to risks associated with other engineering structures. Target values of acceptable risk were recommended as part of the conclusions. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Highlights a the study which investigated the behavior of five spread footings in sand. Description of the load tests; Information on the creep settlement; Differences between strain and depth.

Presents a simple approach for lateral load on piles (SALLOP) for the design of piles subjected to horizontal loads. Prediction of lateral pile capacity; Description of the non-linear behavior of the soil springs by the P-y curves; Zero-shear depth; Predicted versus measured lateral capacities; Prediction of deflection at working loads.