An investigation was made of the filters needed in dams for fine‐grained clays and silts. The “critical” downstream filter in a central core dam should be capable of controlling and sealing a concentrated leak through the core, and should also be stable in conventional laboratory filter tests under a relatively high gradient, such as 1,000. Two different types of laboratory tests were developed to simulate the action of a critical filter (slot and slurry tests). Both gave identical and reproducible results. For fine‐grained clays a sand filter with D15 of 0.5 mm is conservative. For sandy clays and silts the filter criterion D15/d85⩽5 is conservative and reasonable. The Atterberg limits of a clay have no significant influence on the needed critical filter. For nondispersive and dispersive clays having similar particle size distribution the needed critical filters are the same. For “noncritical” filters, such as filters upstream of a clay core, quantitative filter criteria are not necessary.

Filters for Silts and Clays

There is now sufficient evidence to conclude that concentrated leaks occur commonly through the impervious sections of embankment dams by hydraulic fracturing without being observed, even in dams which are not subjected to unusually large differential settlement. Usually these concentrated leaks do not cause erosion, either because the velocity is too low or because the leak discharges into an effective filter. Subsequently the leakage channel is squeezed shut by swelling or softening of the embankment material forming the walls of the crack. In the typical case no measurable leakage emerges downstream and there is no other indication that a concentrated leak developed and was subsequently sealed. This action probably occurs to some degree in most embankment dams.

Hydraulic Fracturing in Embankment Dams

Development of dam safety management system

Hydraulic fracturing can occur in the clay core of an earth and rock-fill dam if the vertical effective stress in the core is reduced to levels that are small enough to allow a tensile fracture to ...

A case study of hydraulic fracturing using finite element methods

Reliability-based serviceability limit state design for immediate settlement of spread footings on clay

Although a variety of methods exist to estimate axial capacity for augered cast-in-place piles, they are generally limited to allowable stress design (ASD) procedures, with little consideration of design reliability. This paper describes the addition of static loading test results to a global augered cast-in-place pile data set to assess the accuracy of new and existing design methods and to address the current lack of reliability-based design methods for augered cast-in-place piles. The new static loading tests in western Washington were carried out on piles installed in granular materials, with pile diameters and lengths ranging from 0.41 to 0.51 m and 9.5 to 29 m, respectively. The preparation of beta coefficients and unit toe bearing resistance values is discussed within the framework of strain-dependent composite tangent moduli and observed residual loads. New relationships for the beta coefficient and toe bearing resistance values are proposed, and the accuracy of new and existing design pro...

Reliability-Based Design of Augered Cast-in-Place Piles in Granular Soils

Incremental, nonlinear finite element analyses were conducted for 14 representative zoned dams of differing geometries and material properties to assess the load transfer and potential for cracking by hydraulic fracturing and local overstress. The results of these analyses showed that significant load transfer was observed in all cases; the load transfer was from the core onto the transitions and shells over most of the height, but was onto the core near the crest. This may be a possible mechanism for longitudinal core cracking in the crest. All other factors being equal, the dams which would exhibit the least transverse cracking potential would have flatter side slopes, thicker cores, sloping cores, medium dense shells and cores compacted drier than optimum. The effect of variations in the transitions properties and thicknesses, dam height and core slope in sloping core dams was found to be small with regard to cracking potential.

Load Transfer and Hydraulic Fracturing in Zoned Dams

Closure of "Load Transfer and Hydraulic Fracturing in Zoned Dams"

A variety of methods are available to estimate axial pile capacity for augered cast-in-place piles, however, these methods are generally limited to Allowable Stress Design procedures with little consideration of design reliability. Local and global datasets of shaft resistance design parameters have been evaluated to address the current lack of reliability-based design methods for augercast piling. This paper summarizes the results of static loading tests performed in Western Washington, installed within granular materials and with diameters and lengths ranging from 0.41 to 0.51 m and 9.5 to 29 m, respectively. The preparation of unit shaft resistances is discussed in consideration of strain dependent composite tangent moduli and observed residual loads. Relationships and their statistical characterization are proposed for unit shaft resistance as function of pile head displacement and relative density (i.e., Standard Penetration Resistance). These data are combined with an existing dataset to represent a global database of β-coefficients. Resistance factors for unit shaft resistance and β-coefficients at the strength limit calibrated using First-Order Second Moment and Monte Carlo methods are proposed for use in Load and Resistance Factor Design.

Reliability of Shaft Resistance for Augered Cast-in-Place Piles in Granular Soils

https://ascelibrary.org/doi/pdf/10.1061/%28ASCE%29GT.1943-5606.0000936

Erratum for “Reliability-Based Design of Augered Cast-in-Place Piles in Granular Soils” by Armin W. Stuedlein, William J. Neely, and Thomas M. Gurtowski

Thomas M. Gurtowski

Papers

Reliability-Based Design of Augered Cast-in-Place Piles in Granular Soils

Load Transfer and Hydraulic Fracturing in Zoned Dams

Closure of "Load Transfer and Hydraulic Fracturing in Zoned Dams"

Reliability of Shaft Resistance for Augered Cast-in-Place Piles in Granular Soils

Erratum for “Reliability-Based Design of Augered Cast-in-Place Piles in Granular Soils” by Armin W. Stuedlein, William J. Neely, and Thomas M. Gurtowski