Recent coe_cee items

Quantifying the Current and Future Greenhouse Gas Emissions from Road Infrastructure in Africa

Tue, 27 Jan 2026 00:00:00 +0000

This paper uses a newly developed framework for quantifying current and future greenhouse gas (GHG) emissions from Africa’s road transportation sector. It provides first-order estimates for road infrastructure projects (new road construction and existing road maintenance and rehabilitation) and vehicle-related emissions through 2050. Africa's current road network was estimated from available data, and its future growth (2021-2050) was modeled using three approaches. Road construction makes up the majority of GHG emissions from infrastructure built before 2021, with culverts and bridges contributing smaller but still significant amounts. By 2050, vehicle operation is projected to account for 85% of total transportation emissions, followed by vehicle manufacturing (7%), new road construction (4%), and road maintenance/rehabilitation and road roughness (approximately 2% each). While infrastructure-related emissions are relatively small compared to vehicle-related emissions, their...

Effect of Anisotropic Consolidation on Cyclic Liquefaction Resistance of Granular Materials via 3D-DEM Modeling

Mon, 4 Mar 2024 00:00:00 +0000

Effect of Anisotropic Consolidation on Cyclic Liquefaction Resistance of Granular Materials via 3D-DEM Modeling

Evolution of granular media under constant-volume multidirectional cyclic shearing

Mon, 29 Jan 2024 00:00:00 +0000

Evolution of granular media under constant-volume multidirectional cyclic shearing

Evolution of granular materials under isochoric cyclic simple shearing

Mon, 29 Jan 2024 00:00:00 +0000

Evolution of granular materials under isochoric cyclic simple shearing

Impact of bidirectional seismic shearing on the volumetric response of sand deposits

Mon, 29 Jan 2024 00:00:00 +0000

Impact of bidirectional seismic shearing on the volumetric response of sand deposits

Liquefaction of granular materials in constant-volume cyclic shearing: Transition between solid-like and fluid-like states

Mon, 29 Jan 2024 00:00:00 +0000

Liquefaction of granular materials in constant-volume cyclic shearing: Transition between solid-like and fluid-like states

Convergence of rotational hardening with bounds in clay plasticity

Mon, 29 Jan 2024 00:00:00 +0000

Convergence of rotational hardening with bounds in clay plasticity

Numerical modeling of soil liquefaction and lateral spreading using the SANISAND-Sf model in the LEAP experiments

Mon, 29 Jan 2024 00:00:00 +0000

Numerical modeling of soil liquefaction and lateral spreading using the SANISAND-Sf model in the LEAP experiments

Multidirectional cyclic shearing of clays and sands: Evaluation of two bounding surface plasticity models

Mon, 29 Jan 2024 00:00:00 +0000

Multidirectional cyclic shearing of clays and sands: Evaluation of two bounding surface plasticity models

Strategies for numerical simulation of cast-in-place piles under axial loading

Mon, 29 Jan 2024 00:00:00 +0000

Strategies for numerical simulation of cast-in-place piles under axial loading

Characteristic limitations of advanced plasticity and hypoplasticity models for cyclic loading of sands

Mon, 29 Jan 2024 00:00:00 +0000

Characteristic limitations of advanced plasticity and hypoplasticity models for cyclic loading of sands

Roles of pre- and post-liquefaction stages in dynamic system response of liquefiable sand retained by a sheet-pile wall

Mon, 29 Jan 2024 00:00:00 +0000

Roles of pre- and post-liquefaction stages in dynamic system response of liquefiable sand retained by a sheet-pile wall

Modeling cyclic shearing of sands in the semifluidized state

Mon, 29 Jan 2024 00:00:00 +0000

Modeling cyclic shearing of sands in the semifluidized state

Effect of particle shape on cyclic liquefaction resistance of granular materials

Mon, 29 Jan 2024 00:00:00 +0000

Effect of particle shape on cyclic liquefaction resistance of granular materials

Effects of size polydispersity on random close-packed configurations of spherical particles

Mon, 29 Jan 2024 00:00:00 +0000

Effects of size polydispersity on random close-packed configurations of spherical particles

Effect of coefficient of uniformity on cyclic liquefaction resistance of granular materials

Mon, 29 Jan 2024 00:00:00 +0000

Effect of coefficient of uniformity on cyclic liquefaction resistance of granular materials

SANISAND-MSf: a sand plasticity model with memory surface and semifluidised state

Mon, 29 Jan 2024 00:00:00 +0000

SANISAND-MSf: a sand plasticity model with memory surface and semifluidised state

Reply to the discussion by Dimitrios Kolymbas of the article entitled âCharacteristic limitations of advanced plasticity and hypoplasticity models for cyclic loading of sandsâ

Mon, 29 Jan 2024 00:00:00 +0000

Reply to the discussion by Dimitrios Kolymbas of the article entitled âCharacteristic limitations of advanced plasticity and hypoplasticity models for cyclic loading of sandsâ

The simplified thermal modeling approach used in CalME

Tue, 29 Nov 2022 00:00:00 +0000

This paper details the development of a new 1‑D combined finite difference and finite element procedure for calculating in-depth pavement temperatures, which has been implemented in the CalME design method. The model is driven by a database of known surface temperatures rather than raw climatic inputs and an energy balance at the surface, since it was noted that the pavement structure had little impact on the surface temperature (if the surface properties remain constant). The model runs quickly, enabling direct simulation of in-depth temperatures while performing Monte Carlo based simulation of pavement reliability. The disadvantages to this approach are that it requires the surface temperatures to be developed independently and that it does not have a coupled moisture model for the prediction of freeze/thaw conditions. The paper also details some anomalies in the output of the Enhance Integrated Climatic Model (used in the new AASHTO mechanistic-empirical...

Using Cameras for Measuring Displacements in Model Tests

Tue, 29 Nov 2022 00:00:00 +0000

Using Cameras for Measuring Displacements in Model Tests

SKS03: Centrifuge Test of Liquefaction-Induced Downdrag in Interbedded Soil Deposits

Thu, 14 Jul 2022 00:00:00 +0000

Earthquake shaking can cause significant soil settlements, especially if the shaking causes liquefaction. Soil settlements will induce drag loads that can significantly increase the axial loads in a pile foundation and/or cause significant pile settlement (Figure 1). The liquefaction-induced downdrag on piles is affected by the complex interplay and timing of a variety of processes including the development and dissipation of pore water pressures, soil settlement, sand boils and gaps that provide vents for high excess pore pressures. Since it has not been possible to accurately model all these complex processes, simplifying assumptions are used to account for downdrag in the current design procedures. A series of centrifuge tests were designed to investigate the complex processes and the validity of the simplifying assumptions. This report describes the details of the second (SKS03) of the two model tests performed under this project. Sinha et al. (2021b)describes the previous...

SKS02: Centrifuge Test of Liquefaction-Induced Downdrag in Uniform Liquefiable Deposit

Thu, 14 Jul 2022 00:00:00 +0000

Earthquake-induced liquefaction can cause soil settlement at pile interfaces, which can induce negative skin friction resulting in additional load (known as drag load) and drag the pile downwards (Figure 1). Despite significant research on the effects of liquefaction on structures and the seismic response of piles, there is still a knowledge gap in the evolution and assessment of liquefaction-induced downdrag on piles mainly related to the complex interplay and timing of the different mechanisms during/post liquefaction such as excess pore pressure generation/dissipation patterns, sequencing and timing of settlements, presence of interface gaps and ejecta, location of the initial neutral plane, and settlement around the tip. This has led to simplifying assumptions in current design procedures, which might result in over-conservatism in drag load estimation. Commonly used numerical tools lack the ability to model these mechanisms, while the absence of experimental data hinders...

Modeling of Dry and Saturated Soil-Foundation Interfaces

Thu, 14 Jul 2022 00:00:00 +0000

Modeling and simulation of earthquake soil-structure interaction (ESSI) require a number of sophisticated modeling and simulation approaches to reduce modeling uncertainty and improve the accuracy of results. The superstructure can be supported by either a shallow or deep foundation and in dry, partially saturated, or fully saturated soil. An interface element is thus required to accurately model the interaction of dry as well as partially saturated soil with the foundation. The current modeling techniques mostly assume a hard normal contact behavior i.e. normal contact stiffness is constant with penetration. However, more physical contact stress expected between the soil-foundation interface is non-linear. The normal contact stiffness increases with penetration until the soil surface becomes hard. At this stage, any further penetration can be assumed to be of hard contact. In this thesis, a soft contact formulation is presented to model the non-linear stiffness at the soil-foundation...

Parametric Study of Liquefaction Induced Downdrag on Axially Loaded Piles

Thu, 14 Jul 2022 00:00:00 +0000

Earthquake-induced liquefaction typically causes soil settlement which may lead to downdrag in axially loaded piles. The drag load generated may overstress the pile or cause significant foundation settlements. Despite significant research progress on the effects of liquefaction on structures and the seismic response of piles, there is still a knowledge gap in the assessment of liquefaction-induced downdrag. This paper discusses different factors that govern this mechanism and presents a parametric study performed using the AASHTO-recommended neutral plane method using displacement-based t-z spring analyses on a simplified profile where liquefiable layer depth and thickness, reconsolidation strains in dense and loose sand, tip conditions, and pile types (L/D ratios) are varied. The results obtained from this preliminary analysis draw some important conclusions regarding the performance of large, medium, and slender piles and are used to design centrifuge model tests to further...

Use of Photron Cameras and TEMA Software to Measure 3D Displacements in Centrifuge Tests

Thu, 7 Jul 2022 00:00:00 +0000

Snapshots recorded from multiple cameras viewing the same dynamic event from different angles can be processed and used for the dynamic tracking of 3D displacements of multiple targets placed on the model. This report describes the first combined use of new high-speed Photron cameras and the TEMA Classic 3D software at the Center for Geotechnical Modeling (CGM) at University of California, Davis (UCD). The cameras and their mounting, as well as the target markers, lighting, camera calibration, and camera triggering are described, followed by a discussion on the software options selected for the analysis of videos recorded for a centrifuge model test conducted on the 9 m-radius centrifuge. The results presented show that this method is effective and reliable in obtaining the positions, displacements, velocities, and accelerations of the targets. Recommendations are made for improvements in future applications.

Obtaining the 3D displacements of targets requires multiple...

Centrifuge Study of Downdrag on Axially Loaded Piles in Liquefiable Soils

Thu, 7 Jul 2022 00:00:00 +0000

Piles are designed to transfer superstructure loads using positive skin friction and tip resistance while undergoing acceptable settlements. However, when liquefaction-induced soil settlement occurs, it can drag the pile downward and result in negative skin friction and drag load. In such cases, estimating the drag load and pile settlement becomes important for pile design. A series of centrifuge model tests were performed to study liquefaction-induced downdrag on piles. The tests included four heavily instrumented piles installed in two different soil layered profiles with their tip embedment zero, three and five times their diameterin the dense sand. Loads on the piles were varied to study their effect on drag load and pile settlement. Results are presented describing the mechanism behind the development of liquefaction-induced downdrag, the magnitude of drag load, and pile settlement. Finally, recommendations are made for the design of piles in liquefiable soils

Impact of bidirectional seismic shearing on the volumetric response of sand deposits

Tue, 11 Feb 2020 00:00:00 +0000

Impact of bidirectional seismic shearing on the volumetric response of sand deposits

Proceedings of the Symposium on Recent Advances in Geotechnical Centrifuge Modeling

Fri, 15 May 2015 00:00:00 +0000

Cover: Proceedings of the Symposium on Recent Advances in Geotechnical Centrifuge Modeling, National Geotechnical Centrifuge, Department of Civil Engineering, University of California Davis

Introduction: A symposium on Recent Advances in Geotechnical Centrifuge Modeling was held on July 18-20, 1984 at the University of California at Davis. The symposium was sponsored by the National Science Foundation's Geotechnical Engineering Program and the Center for Geotechnical Modeling at the University of California at Davis.

The symposium offered an opportunity for a meeting of the InternationalCommittee on Centrifuges of the International Society for Soil Mechanics and Foundation Engineering. The U.S. participants also met to discuss theadvancement of the centrifuge modeling technique in the U.S. A request is being transmitted to the American Society of Civil Engineers to establish a subcommittee on centrifuges within the Geotechnical Engineering Division.

Editor:...

CENTRIFUGAL MODEL TESTS FOR ULTIMATE BEARING CAPACITY OF FOOTINGS ON STEEP SLOPES IN COHESIONLESS SOIL [abstract]