A simplified semiempirical predictive relationship for estimating permanent displacements due to earthquake-induced deviatoric deformations is presented. It utilizes a nonlinear fully coupled stick-slip sliding block model to capture the dynamic performance of an earth dam, natural slope, compacted earth fill, or municipal solid-waste landfill. The primary source of uncertainty in assessing the likely performance of an earth/waste system during an earthquake is the input ground motion. Hence, a comprehensive database containing 688 recorded ground motions is used to compute seismic displacements. A seismic displacement model is developed that captures the primary influence of the system’s yield coefficient ( ky ) , its initial fundamental period ( Ts ) , and the ground motion’s spectral acceleration at a degraded period equal to 1.5 Ts . The model separates the probability of “zero” displacement (i.e., ⩽1 cm ) occurring from the distribution of “nonzero” displacement, so that very low values of calculated...

Simplified Procedure for Estimating Earthquake-Induced Deviatoric Slope Displacements

Based on a synthesis of published laboratory data, two types of cyclic threshold shear strain are examined and their approximate magnitudes identified for different types of soils. They are the linear cyclic threshold shear strain, γtl and the volumetric cyclic threshold shear strain, γtv, with γtv>γtl. These strains represent boundaries between fundamentally different categories of cyclic soil behavior. For cyclic strains below γtl, soil behaves essentially as a linearly elastic material. Between γtl and γtv, soil becomes markedly nonlinear but remains largely elastic because permanent changes of its microstructure still do not occur or are negligible. Above γtv, soil becomes increasingly nonlinear and inelastic, with significant permanent microstructural changes taking place under cyclic loading. That is, γtv, = the threshold separating cyclic strains that cause or do not cause significant permanent changes of soil microstructure. In practical terms, these microstructural changes are manifested in resid...

Cyclic Threshold Shear Strains in Soils

Ground motion evaluation procedures for performance-based design

Damping formulation for nonlinear 1D site response analyses

Engineering properties of municipal solid waste

The unit weight of municipal solid waste (MSW) is an important parameter in engineering analyses of landfill performance, but significant uncertainty currently exists regarding its value. A careful review of reliable field data shows that individual landfills have a characteristic MSW unit weight profile. Based on in situ unit weight data and trends observed in large-scale laboratory tests, a hyperbolic relationship was developed to represent this characteristic MSW unit weight profile. Within the context of this characteristic profile, landfill-specific values of MSW unit weight depend primarily on waste composition, operational practices (i.e., compaction, cover soil placement, and liquids management), and confining stress. Guidance is provided for developing landfill-specific MSW unit weight profiles, including procedures for performing large-scale tests for in situ measurement of MSW unit weight at a landfill.

Unit weight of municipal solid waste

One-dimensional nonlinear ground response analyses provide a more accurate characterization of the true nonlinear soil behavior than equivalent-linear procedures, but the application of nonlinear codes in practice has been limited, which results in part from poorly documented and unclear parameter selection and code usage protocols. In this article, exact (linear frequency-domain) solutions for body wave propagation through an elastic medium are used to establish guidelines for two issues that have long been a source of confusion for users of nonlinear codes. The first issue concerns the specification of input motion as “outcropping” (i.e., equivalent free-surface motions) versus “within” (i.e., motions occurring at depth within a site profile). When the input motion is recorded at the ground surface (e.g., at a rock site), the full outcropping (rock) motion should be used along with an elastic base having a stiffness appropriate for the underlying rock. The second issue concerns the specification of viscous damping (used in most nonlinear codes) or small-strain hysteretic damping (used by one code considered herein), either of which is needed for a stable solution at small strains. For a viscous damping formulation, critical issues include the target value of the viscous damping ratio and the frequencies for which the viscous damping produced by the model matches the target. For codes that allow the use of “full” Rayleigh damping (which has two target frequencies), the target damping ratio should be the small-strain material damping, and the target frequencies should be established through a process by which linear time domain and frequency domain solutions are matched. As a first approximation, the first-mode site frequency and five times that frequency can be used. For codes with different damping models, alternative recommendations are developed.

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Use of Exact Solutions of Wave Propagation Problems to Guide Implementation of Nonlinear Seismic Ground Response Analysis Procedures

The method for cyclic characterization of liquefiable sands, which employs the concept of dynamic backbone curve in conjunction with the Masing criteria for construction of unloading and reloading branches of cyclic loops, is refined and verified. The method also encompasses subsequent cyclic loading, when soil undergoes significant degradation due to pore‐water pressure buildup. To accurately describe the initial backbone curve and associated initial cyclic loop, and subsequent degraded backbone curves and associated subsequent cyclic stress‐strain loops, a well‐known hyperbolic model and a degradation model are modified. Although relatively simple, such modifications enable accurate description of the stress‐strain loops of the first and subsequent cycles, even in cases when soil rapidly degrades and liquefies in just a few cycles. Consequently, a much better agreement between the measured and calculated damping values can be also obtained. The investigation is based on test results obtained on five dif...

Cyclic Characterization of Liquefiable Sands

In situ measurements and observations of field performance provide a valuable source of information on the properties of municipal solid waste (MSW) for analysis of landfills. "Static" properties of MSW such as unit weight and shear strength are evaluated from observations made during and after waste placement, including records of tonnage of waste received and cover soil used during disposal, observations of stable MSW slopes and in situ load tests. "Dynamic" properties of MSW such as modulus and damping are evaluated from observations of the performance of landfills subject to strong ground motions and by geophysical testing. INTRODUCTION Seismic design of MSW landfills is complicated by difficulty in obtaining information on the properties of MSW. Difficulties in evaluating appropriate MSW properties for seismic stability and deformation analyses are not limited to the "dynamic" properties of small strain shear modulus and strain-dependent modulus reduction and damping factors. Appropriate values for the "static" properties of MSW unit weight and shear strength required for seismic stability and deformation analyses are also difficult to establish. The selected value of these static properties 1Associate, GeoSyntec Consultants, 16541 Gothard Street, Suite 211, Huntington Beach, CA 92647 2Senior Staff Engineer, GeoSyntec Consultants, 16541 Gothard Street, Suite 211 Huntington Beach, CA 92647 3Principal, GeoSyntec Consultants, 1100 Lake Hearn Drive, Suite 200, Atlanta, Georgia, 30342. 4Senior Project Engineer, GeoSyntec Consultants, 1100 Lake Hearn Drive, Suite 200, Atlanta, GA 30342

Evaluation of MSW properties for seismic analysis

This paper proposes a model for the behavior of fully saturated normally consolidated and overconsolidated marine clays subjected to uniform cyclic strain-controlled and staged cyclic loading under simple shear conditions. To simulate a clay response similar to that occurring during the irregular cyclic loading of earthquakes, ocean storms, and other natural phenomena, staged cyclic testing with several levels of different uniform cyclic strains was performed. Cyclic degradation, cyclic pore-water pressure generation, and cyclic threshold shear strain were incorporated into the model. Cyclic threshold shear strain was defined as the cyclic strain amplitude below which neither significant pressure develops nor significant degradation occurs. The model was verified by staged cyclic direct simple shear testing of five marine clays. Practical applications of the model are discussed.

Neven Matasovic

Papers

Unit weight of municipal solid waste

Use of Exact Solutions of Wave Propagation Problems to Guide Implementation of Nonlinear Seismic Ground Response Analysis Procedures

Cyclic Characterization of Liquefiable Sands

Evaluation of MSW properties for seismic analysis

Generalized Cyclic-Degradation-Pore-Pressure Generation Model for Clays