Papers by Richard Bathurst
E3S Web of Conferences
This document provides a summary of the different topics presented at the Special Session organiz... more This document provides a summary of the different topics presented at the Special Session organized by the International Geosynthetics Society (IGS) Technical Committee on Soil Reinforcement (TC-R). This Special Session brings together very interesting studies regarding soil reinforcement in the field of geosynthetics. Studies presented include topics both from theoretical and practical points of view of reinforcement geosynthetics including general products and applications, cases studies on road embankments under challenging site boundary conditions, research on deterministic and probabilistic design of reinforced fills over voids, numerical analysis of reinforced soil wall structures, encased granular column technique, and geosynthetic-reinforced bridge abutment behavior.
Frontiers in Built Environment, 2022
Soil-facing mechanical interactions play an important role in the behavior of earth-retaining wal... more Soil-facing mechanical interactions play an important role in the behavior of earth-retaining walls. Generally, numerical analysis of earth-retaining structures requires the use of interface elements between dissimilar component materials to model soil–structure interactions and to capture the transfer of normal and shear stresses through these discontinuities. In finite element method software programs, soil–structure interactions can be modeled using “zero-thickness” interface elements between the soil and structural components. These elements use a strength/stiffness reduction factor that is applied to the soil adjacent to the interface. However, in some numerical codes where the zero-thickness elements (or other similar special interface elements) are not available, the use of continuum elements to model soil–structure interactions is the only option. The continuum element approach allows more control of the interface features (i.e., material strength and stiffness properties), ...
Innovative Solutions for Deep Foundations and Retaining Structures, 2019
Earth retaining walls are common geotechnical structures with a wide range of solutions available... more Earth retaining walls are common geotechnical structures with a wide range of solutions available to perform the same function. More and more, geotechnical engineers are asked to find the best solution among several options in different civil engineering applications based on environmental impact, cost and societal/functional issues. Evaluation of these three pillars during the selection process of a structure (such as an earth retaining wall) is called a sustainability assessment. This paper describes a sustainability assessment methodology and gives examples to select the best sustainable option from candidate conventional gravity and cantilever wall types, and steel and polymeric soil reinforced mechanically stabilized earth (MSE) walls of 5 m height. Analyses were carried out using the MIVES methodology which is based on value theory and multi-attribute assumptions. The paper identifies how indicator issues are scored, weighted and aggregated to generate final numerical scores that allow solution options to be ranked. The final scores include an adjustment based on stakeholder preferences for the relative importance of the three sustainability pillars (environmental, economic (cost) and societal/functional). The analysis results show that MSE wall solutions are most often the best option in each category compared to conventional gravity and cantilever wall solutions and thus most often the final choice when scores from each pillar were aggregated to a final score. The paper also includes a sensitivity analysis of the choice of value functions and stakeholder weighting preferences on the final ranking scores used to select the best sustainable solution. The analyses also show that the choice of value function and stakeholder preferences can lead to a conventional structure being the best option.
Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)), 2021
Dynamic response of a segmental (modular block) retaining wall system to recorded ground motions ... more Dynamic response of a segmental (modular block) retaining wall system to recorded ground motions is investigated. The magnitude and characteristics of wall response are compared to those obtained under harmonic input base acceleration. The calculated maximum lateral displacement and reinforcement load of the segmental retaining wall mode1 subjected to a single frequency, harmonic input acceleration were considerably larger than the corresponding values obtained using a number of earthquake accelerograms with comparable predominant frequencies. It is concluded that the random characteristic of actual ground acceleration may partly explain the relatively good performance of reinforced-soil retaining wall systems that were designed without seismic considerations or at best using simple pseudo-static limit equilibrium methods. Nevertheless, it was found that low-frequency ground motions with high intensity values can result in significant structural response magnitude of short-period re...
Proceedings of the Institution of Civil Engineers - Geotechnical Engineering, 2016
Soils and Foundations, 2015
The paper reports the results of the analysis of field installation damage tests carried out on g... more The paper reports the results of the analysis of field installation damage tests carried out on geogrid soil reinforcement products used in Japan. The data are taken from Public Works Research Center (PWRC) product certification reports. The database comprises a total of 130 tensile tests performed on undamaged (reference) tests and 390 tensile tests performed on exhumed damaged geogrid specimens. A total of 78 installation damage factors were computed by the writers representing 26 different geogrid products from 12 different product lines in combination with three different aggregate types. The field tests were carried out using a standard PWRC protocol and the calculation of installation damage factors and spread in data was carried out in a consistent manner by the writers. The data are shown to be in good agreement with the results of tests carried out on similar products reported in other countries. The installation damage factors summarized in this study provide a useful benchmark for future field installation damage test results in Japan and worldwide. The statistical analysis of variability in installation damage test results is a prerequisite for future probabilistic analysis and design for the ultimate tensile rupture limit state in geogrid reinforced soil structures and for load and resistance factor design (LRFD) calibration of this limit state.
Journal of the Society of Materials Science, Japan, 2016
Geosynthetics International, 2015
ABSTRACT: This paper reports the results of three 4 m high full-scale instrumented geogrid-reinfo... more ABSTRACT: This paper reports the results of three 4 m high full-scale instrumented geogrid-reinforced soil walls constructed with different structural facings having a range of stiffness. The walls were seated on a 2 m deep foundation layer that was laterally supported at the base of the wall face by a rigid bulkhead. Following end of construction, the bulkhead was moved outward in stages to simulate loss of foundation support in the vicinity of the wall toe. Bulkhead loads, wall deformations, backfill settlements, reinforcement loads and earth pressures recorded at end of construction and during bulkhead displacement are presented in this paper. Measured reinforcement loads are compared to predicted loads at end of construction using different design methods. The walls demonstrated that there was available reserve load capacity which prevented internal failure mechanisms from developing in the reinforced soil zone even after significant loss of foundation support in the vicinity of...
INTERNATIONAL CONFERENCE ON COMPUTATIONAL SCIENCES-MODELLING, COMPUTING AND SOFT COMPUTING (CSMCS 2020), 2021
Soils and Foundations, 2015
The paper uses statistical data for the prediction of installation damage and creep-reduced stren... more The paper uses statistical data for the prediction of installation damage and creep-reduced strength collected by the writers in earlier investigations to estimate the probability of failure of tensile rupture of geogrid reinforcement products. The original data were compiled from Public Works Research Center (PWRC) geogrid product certification reports issued in Japan. The paper develops the formulation for the ultimate tensile rupture limit state equation and links it to allowable stress design (ASD) practice currently used in Japan and reliability theory-based load and resistance factor design (LRFD) used in North America. The paper shows that variability in the prediction of creep-reduced strength is largely captured by the inherent variability in strength of the materials at the time of manufacture. Combined variability due to creep and installation damage is typically dominated by variability in the prediction of strength after installation damage. Where this is not the case the combined variability is very low (less than 5%). The variability in the estimate of strength reduction due to combined installation damage and creep is demonstrated to be less than the variability in the estimates of reinforcement load even for the case of a load model judged to give relatively accurate load predictions. For poorer load models the under-prediction of reinforcement loads provides an additional margin of safety. The paper provides a framework for future rigorous reliability theory-based LRFD calibration for the ultimate tensile rupture of geogrid reinforcement in reinforced soil applications in Japan and elsewhere, and provides the necessary bias statistics for the resistance side in the ultimate tensile rupture limit state equation.
Geosynthetics International, 1995
The paper examines seismic stability analyses of geosynthetic-reinforced segmental retaining wall... more 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 sat...
Geosynthetics International, 1994
The paper describes a series of in-isolation cyclic load-extension tests performed on HDPE,and PE... more The paper describes a series of in-isolation cyclic load-extension tests performed on HDPE,and PET geogrid specimens. The specimens were tested at five different loading frequencies: 0.1, 0.5, 1.0, 2.0 and 3.5 Hz, and over a range of load amplitudes. The load-strain behavior of the geogrid materials is characterized using two distinct features of the cyclic response: 1) non-linear hysteresis unload-reload loops; and 2) a load-strain cap that contains all hysteresis curves. The cyclic load-strain response of the HDPE and PET geogrid specimens is demonstrated to be significantly different from the static response of the same materials tested according to the current ASTM D 4595 method of test. The load-strain caps for HDPE geogrid specimens are found to be very sensitive to the loading frequency and loading history while those of the PET geogrid appear to be relatively insensitive. The hysteresis load-strain behavior of both types of geogrids depends strongly on the load level and loa...
Soils and Foundations, 2015
ABSTRACT A mechanically stabilized earth wall with steel strip soil reinforcement was built and i... more ABSTRACT A mechanically stabilized earth wall with steel strip soil reinforcement was built and instrumented by the Public Works Research Institute of Japan. Measured reinforcement loads and vertical toe loads are compared to values predicted using the finite difference program FLAC. Backfill and foundation soil properties were not reported in the original case study. A novel relative error technique was used to select the best estimates of the single-value elastic modulus for both soils. The relative errors were computed from the calculated and measured values of the tensile load in the steel strips and the vertical toe load at the end of the wall construction. Minimum relative errors were visually detectable in the contour plots of the weighted relative errors, and these minima were used to select the elastic moduli of the baseline backfill soil and the foundation soil. The baseline values were shown to yield predicted tensile and vertical toe loads that are judged to be in good agreement with the measured data. Parametric analyses were carried out to examine the quantitative influence on the computed reinforcement loads and the vertical toe load of the various soil modulus, interface shear stiffness and interface friction angles around the baseline values.
Geosynthetics International, 2002
A summary of 20 well-documented geosynthetic wall case histories representing a total of 35 analy... more A summary of 20 well-documented geosynthetic wall case histories representing a total of 35 analysis conditions is presented. These case histories cover a wide variety of wall heights, surcharge loading, foundation conditions, facing types and batter, reinforcement types and stiffness, and reinforcement spacing. All of the production walls, including some that have been in service for 25 years, have performed well with low reinforcement strains and minimal deflections. Some of the walls were research structures that, although purposely underdesigned, could not be taken to failure, demonstrating that the internal stability design of geosynthetic walls in North America is conservative. Each of the walls was characterized globally with respect to internal level of safety, or resistance to demand ratio. Even when using nonconservative estimates of soil property values and perfect matching of the reinforcement strength to demand, the Simplified Method resulted in approximately 1.5 to 4 t...
Journal of Geotechnical and Geoenvironmental Engineering, 2016
AbstractThe paper reports numerical model details and predictions of the end-of-construction perf... more AbstractThe paper reports numerical model details and predictions of the end-of-construction performance for two instrumented and well-documented mechanically stabilized earth (MSE) walls. The walls were constructed as part of the highway SR-18 approach fills for a bridge near Seattle, Washington. The geogrid reinforced block face walls were modeled using a commercially available two-dimensional (2D) finite-difference program. The paper provides details on how material properties were selected from laboratory testing of wall components and how the computer modeling was carried out. The paper shows that predicted wall deformations and reinforcement strains were in reasonable agreement with measured data using both linear elastic-plastic and nonlinear elastic-plastic constitutive models for the soil. The geogrid reinforcement was simulated using a nonlinear load-strain-time secant stiffness model and cable elements. The paper compares numerical predictions of reinforcement loads at end of construction with ...
Geotextiles and Geomembranes, 2016
Geosynthetic-reinforced and column-supported (GRCS) embankments have proven to be an effective co... more Geosynthetic-reinforced and column-supported (GRCS) embankments have proven to be an effective construction technique for fills on soft foundations. The paper introduces a modified unit cell approach to model GRCS embankments supported by deep mixed column walls. The modified unit cells include linear elastic springs at one or both vertical boundaries to 21 simulate lateral displacements of the embankment fill and foundation soil. Program FLAC is 22 used to compare numerical outcomes using the modified unit cells with those using the typical 23 unit cell arrangement with lateral rigid side boundaries. Numerical results demonstrate good 24 agreement between simulations using small-strain and large-strain modes in some cases and large differences in other cases. Lateral displacements of the embankment fill and foundation soil using the modified unit cells are shown to have large influence on reinforcement loads. Finally the paper demonstrates that calculated reinforcement loads are sensitive to choice of small-strain 28 or large-strain mode when using program FLAC.
Journal of Geotechnical and Geoenvironmental Engineering, 2015
ABSTRACT The Simplified Method as reported in AASHTO and Federal Highway Administration (FHWA) ma... more ABSTRACT The Simplified Method as reported in AASHTO and Federal Highway Administration (FHWA) manuals has been demonstrated to give poor predictions of unfactored reinforcement loads and strains, especially for geosynthetic reinforced soil walls. The writers have proposed the K-stiffness Method to improve the load prediction accuracy for walls under working stress (operational) conditions. However, it has also been recognized in recent publications by the writers and others that further improvements to the K-stiffness Method are needed. Furthermore, acceptance of the K-stiffness Method has been hindered due to its perceived complexity and the use of the plane strain friction angle to quantify the strength of the reinforced soil. This paper takes a fresh look at both methods and uses lessons learned from the K-stiffness Method development to improve the accuracy of the AASHTO/FHWA Simplified Method. Key parameters introduced during the development of the K-stiffness Method are applied to the Simplified Method and updated to further improve load prediction accuracy. Additional wall case histories have been added to the database used for the original K-stiffness Method to calibrate the new model and to broaden its utility. An important improvement is a single model that allows for seamless load prediction across a range of walls constructed with relatively extensible geosynthetic reinforcement and inextensible steel reinforcement materials. The quantitative improvement of the new model (Simplified Stiffness Method) compared to the current AASHTO/FHWA Simplified Method is demonstrated through statistical analysis of load bias values (i.e., the ratio of measured to predicted reinforcement load).
This report summarizes the scope and conclusions of a 3D numerical modelling analysis of mechanic... more This report summarizes the scope and conclusions of a 3D numerical modelling analysis of mechanically stabilized earth (MSE) walls constructed with concrete panels and strip reinforcement. These systems pose numerical challenges as a result of the discontinuous reinforcement arrangement which suggest the necessity on the 3D strategies instead of 2D modelling to determine and to fit its actual intrinsic behaviour.
Soil-facing mechanical interactions play an important role in the behavior of earth retaining wal... more Soil-facing mechanical interactions play an important role in the behavior of earth retaining walls. Generally, numerical analysis of earth retaining structures requires the use of interface elements between dissimilar component materials to model soil-structure interactions and to capture the transfer of normal and shear stresses through these discontinuities. In the finite element method PLAXIS software program, soil-structure interactions can be modelled using “zero-thickness” interface elements between the soil and structural components. These elements use a strength/stiffness reduction factor that is applied to the soil adjacent to the interface. However, in some numerical codes where the zerothickness elements (or other similar special interface elements) are not provided, the use of continuum elements to model soil-structure interactions is the only option. The continuum element approach allows more control of the interface features (i.e., material strength and stiffness prop...
Uploads
Papers by Richard Bathurst