The compressible inclusion function of EPS geofoam

A critical review of the existing pseudo-dynamic approach is provided and a new pseudo-dynamic approach is proposed based on a visco-elastic behavior of backfill overlying rigid bedrock subjected to harmonic horizontal acceleration. Considering a planar failure surface, closed form expressions for seismic active soil thrust, soil pressure distribution and overturning moment are obtained. The results of this study indicate that the existing pseudo-dynamic method can strongly underestimate the soil active thrust especially close to the fundamental frequency of the backfill, where the soil response is more sensitive to the damping ratio. The acting point of the total seismic active thrust is always found to be higher than that predicted by the traditional pseudo-dynamic approach. The effect of the shear resistance angle and wall friction angle on the acting point increases as the amplitude of the base acceleration increases, whereas their effect is generally small far from the natural frequencies of the backfill.

A New Pseudo-dynamic Approach for Seismic Active Soil Thrust

By taking the failure surface as a combination of the arc of a logarithmic spiral and a straight line, passive earth pressure coefficients in the presence of horizontal pseudostatic earthquake body...

Seismic passive earth pressure coefficients for sands

Seismic passive earth pressure coefficients were computed by the method of limit equilibrium using a pseudostatic approach for seismic forces. Composite curved rupture surfaces were considered in the analysis. While earlier studies using this type of analysis were mainly for sands, seismic passive earth pressure coefficients were obtained in the present study considering the effects of cohesion, surcharge, and own weight. The minimum seismic passive force was obtained by adding the individual minimum values of these components and the validity of the principle of superposition was examined. Other parameters considered in the analysis were wall batter angle, ground surface slope, soil friction angle, wall friction angle, wall adhesion to soil cohesion ratio, and horizontal and vertical seismic accelerations. The seismic earth pressure coefficients were found to be highly sensitive to the seismic acceleration coefficients both in the horizontal and vertical directions. Results of the study are presented in the form of figures and tables. Comparisons of the proposed method with available theories in the seismic case are also presented.

Seismic Passive Earth Pressures in Soils

The paper examines seismic stability analyses of geosynthetic-reinforced segmental retaining walls (modular block walls). Stability analyses are developed within the framework of a pseudo-static approach that gives factors of safety against collapse mechanisms or rupture of component materials. The Mononobe-Okabe method is used to estimate dynamic earth pressures. Parametric analyses of forces and factors of safety related to external, internal and facing failure modes for walls constructed on competent foundations are presented. Shear interfaces between facing units are considered as possible planes of failure in facing stability analyses. The potential for local toppling of the facing column is also investigated. The results of analyses demonstrate that there is a limiting value of the horizontal seismic coefficient above which the margin of safety against base sliding and overturning may be unacceptably low during a seismic event for segmental retaining walls designed to just satisfy minimum factors of...

Pseudo-Static Seismic Analysis Of Geosynthetic-Reinforced Segmental Retaining Walls

: This technical report deals with the soil mechanics aspects of the design of waterfront retaining structures built to withstand the effects of earthquake loadings. It addresses the stability and movement of gravity retaining walls and anchored sheet pile walls, and the dynamic forces against the walls of drydocks and U-frame locks. The effects of wall displacements, submergence, liquefaction potential, and excess pore water pressures, as well as inertial and hydrodynamic forces, are incorporated in the design procedures. Several new computational procedures are described in this report. The procedures used to calculate the dynamic earth pressures acting on retaining structures consider the magnitude of wall displacements. For example, dynamic active earth pressures are computed for walls that retain yielding backfills, i. e., backfills that undergo sufficient displacements during seismic event to mobilize fully the shear resistance of the boil. For smaller wall movements, the shear resistance of the soil is not fully mobilized and the dynamic earth pressures acting on those walls are greater because the soil comprising the backfill does not yield, i.e., a nonyielding backfill. Procedures for incorporating the effects of submergence within the earth pressure computations, including consideration of excess pore water pressures, are described.... Dynamic earth pressures, Hydraulic structures, Earthquake engineering, Soil dynamics, Earth retaining structures.

The Seismic Design of Waterfront Retaining Structures

Few solution techniques exist for the determination of pseudostatic dynamic passive earth pressures for cohesionless soils. The widely accepted Mononobe–Okabe equation can result in the computing o...

Limit equilibrium computation of dynamic passive earth pressure

: The U.S. Army Corps of Engineers is responsible for designing and maintaining a large number of navigation and flood control structures. Many of the older massive concrete gravity hydraulic structures are being examined to determine if rehabilitation is required to meet stability criteria. The procedures currently used for evaluating the safety of existing massive hydraulic structures are the conventional equilibrium methods, which are the same general methods used in the design of these structures. Because the conditions of equilibrium are insufficient for a complete analysis of all aspects of structure foundation interaction involved in the stability and performance of these structures (soil structure foundation interaction in the case of earth retaining structures), these conventional equilibrium methods necessarily involve assumptions regarding aspects of the loading forces and the resisting forces that act on the hydraulic structures. Differences between actual field performance and calculations from conventional analysis have been noted for some existing hydraulic structures. Conventional design methods were developed based largely on classical limit equilibrium analysis without regard to deformation related concepts. Today, analytical tools such as the finite element method (FEM) are available which consider the manner in which the loads and resistance are developed as a function of the stiffnesses of the foundation rock, the structure foundation interface, and rock joints within the foundation. These analytical tools provide a means to evaluate the conventional equilibrium-based design methods used to evaluate the safety of existing hydraulic structures, and specifically, to identify and investigate key assumptions used in safety calculations from the conventional analysis.

http://www.dtic.mil/cgi-bin/GetTRDoc?AD=ADA329714&Location=U2&doc=GetTRDoc.pdf

Repair, Evaluation, Maintenance and Rehabilitation Research Program: Evaluating the Stability of Existing Massive Concrete Gravity Structures Founded on Rock

Few solution techniques exist for the determination of dynamic passive earth pressures for cohesionless soils. The pseudostatic dynamic Mononobe-Okabe equation is widely used to design structures that must resist earthquake loads. Researchers have noted that the Mononobe-Okabe equation assumes a planar failure surface, which is not the most critical mode of failure for determining the passive failure load. The goal of this research was to develop a more accurate method for computing pseudostatic dynamic passive earth pressures. This paper outlines the development of a computer-program-based solution assuming a log-spiral failure surface to compute pseudostatic dynamic passive earth pressure coefficients. The programming language COMMON LISP was used to develop the code. The features and capabilities of this programming language are not widely known outside the field of computer science. This paper illustrates the use of COMMON LISP in the formulation and solution of computationally intensive algorithms.

Robert M. Ebeling

Papers

The Seismic Design of Waterfront Retaining Structures

Limit equilibrium computation of dynamic passive earth pressure

Repair, Evaluation, Maintenance and Rehabilitation Research Program: Evaluating the Stability of Existing Massive Concrete Gravity Structures Founded on Rock

Computation of dynamic passive earth pressure using lisp