Giroud’s research combines rigor and selection of topics of practical relevance both for geotechnical and geosynthetics engineering. Giroud researches mainly for the benefit of the practicing engineer. Hence, research findings have application in practice, not only implications for practice. While in academia (1963-1978), his research concerned mostly foundation design. The beneficiary of this research is the practicing civil engineer who needs to calculate the settlement or the bearing capacity of the soil. In the early 1970s, the scope enlarges to include engineers interested in incorporating geosynthetics in the design of a dam or a reservoir, provided there exist suitable design methods. Soon, Giroud’s publications provide the practicing engineer with design methods for a variety of applications of geosynthetics to unpaved roads, embankments, drainage systems, landfills and all kinds of containment facilities. Through the years, these methods are periodically revisited and improved, a hallmark of Giroud’s work.

Given the broad spectrum of Giroud’s research topics, the only sensible way to present an overview is to focus on main themes. However, this customary approach may miss the common elements of his research method, which are 1) defining crisply the problem and the relevant quantities, 2) delineating the method of analysis and 3) drawing attention to any assumptions needed to obtain a solution to the practical problem at hand. Element 1, definitions, is the contribution of Giroud-the-philosopher and makes introductory parts with definitions worth studying even for readers unfamiliar with the topics addressed, e.g. [1]. Element 3, making acknowledged assumptions, is the contribution of Giroud-the-pioneer; it is a manifestation of analytic agility that often opens new research directions for the geosynthetics community, e.g. [2]. Definitions and assumptions are signature elements of the Giroud research method, worthy of a separate study on research practices. A few times, the reader comes across a rarity in scientific papers, a volunteered public statement that a previous method is made obsolete by an improved replacement, e.g. [3]. Having stressed right from the beginning these elements so that readers anticipate them, we will see ample evidence of these characteristics in the thematic sections that follow.

At the beginning of his career as a researcher and assistant professor at the University of Grenoble, Giroud was interested in stresses and displacements induced in the soil by shallow foundations. The research output from this first, purely geotechnical, research decade is 80 publications with plasticity solutions for bearing capacity problems and a long series of elasticity solutions for stresses and settlement calculations, mostly in French but progressively in English as well. Perhaps the most useful family of solutions is that for the settlements at key points of a rectangular area loaded by any linearly varying distributed load (Giroud 1968) [4]. Several of these elasticity solutions are included in the classic compilation “Elastic Solutions for Soil and Rock Mechanics” by Poulos and Davis (1974) [5] (in Chapter 3, Distributed loads on the surface of a semi-infinite mass, and Chapter 5, Surface loading of a finite layer underlain by a rigid base). All the solutions were compiled in three volumes of the “Tables pour le calcul des fondations”, Volume 1 (Giroud 1972) [6] and Volume 2 (Giroud 1973) [7] on stresses and displacements, and Volume 3 (Giroud et al. 1973) [8] on bearing capacity. These three books, which have been routinely used by French-speaking engineers, are also available online with a foreword by Roger Frank, former president of the ISSMGE [link].

We asked Harry Poulos and Rodrigo Salgado, two prominent members of the geotechnical engineering community from different generations, to share with us thoughts about the place of elasticity and plasticity solutions, not necessarily only those by Giroud, at the end of the first quarter of the 21^st century.

HARRY POULOS

I first became aware of the work of J-P Giroud in 1969, when I began compiling a series of elastic solutions for soil and rock mechanics while on sabbatical leave at MIT. His work on this same topic had just been made accessible to the English-speaking world after being published in the ASCE Journal of the Soil Mechanics and Foundation Engineering Division, and the solutions he presented were comprehensive and a model of clarity. I had correspondence with him and subsequently visited him in Grenoble where he showed me the drafts of his own compilations of his original solutions. In due course, he kindly sent me the full three volumes of his work, including two volumes of elastic solutions and the later Volume 3 dealing with plasticity solutions for foundation bearing capacity.

In subsequent years, and especially when undertaking consulting work, I have frequently referred to Giroud’s work when a quick and reliable solution for foundation movement or bearing capacity was required. Even in these days when powerful computer programs are much more freely available, Giroud’s work remains invaluable in providing not only a quick solution, but perhaps even more importantly, a means of checking the accuracy and reliability of complex numerical computer analyses.

Giroud did the geotechnical profession a great service in compiling the three volumes of “Tables pour le calcul des foundations”, and an equally important and generous service in making these three treasure troves of information freely available online.

RODRIGO SALGADO

J.P. Giroud's work developing elastic and elasto-plastic analyses for the boundary-value problems of geomechanics—notably bearing capacity and settlement analysis—was done in the first part of his career and were, at the time, at a level of rigor that was unmatched. His solutions helped anchor geotechnical engineering to analyses that produced substantially correct answers to questions. The practicing engineer had only to decide that the assumptions underlying those analyses matched the conditions existing in the problem to be solved. It is noteworthy that he took care to produce tables and charts to aid the practice of geotechnical engineering. At the time, this was much needed because of very limited access to computers.

The role of plasticity theory and advanced constitutive modeling in today's geomechanics is no less important. In fact, the combination of greater understanding of elasto-plasticity, realistic constitutive models, rigorous methods of boundary-value problem solution—such as the material point method and the finite element method—and much more advanced computational power enable very accurate modeling of geotechnical problems. This capability has led to the ability to produce design methods for shallow and deep foundations, for example, that take full account of what has been learned about soil in the past five decades: (1) soil derives its strength from friction and dilatancy, and friction alone determines its mechanical response in the absence of volume change during shearing; (2) dilatancy depends on soil density, effective stress and soil fabric; and (3) soil is linear elastic only at very small strains, with plasticity starting for strains as small as 10^-6. These advances were only possible because of the pioneering work of Giroud and others of his contemporaries.

Geosynthetic materials started being used in civil engineering projects in the late 1950s. By the late 1960s, high-quality nonwoven geotextiles were available (still called “fabrics” then). Manufacturing companies were eager to see them used in civil engineering applications and Giroud was ready to apply to new materials the analytical skills he used on soils. From 1973, geotextiles and geomembranes become the only topic of his technical activity, both in research and consulting. In 1978, he leaves academia for consulting without decreasing significantly the rate of his research output; from this point onwards, research topics are drawn from his performance investigation and consulting activities. Research themes are principally geosynthetic properties and design methods.

Giroud has published approximately 100 papers on properties and behavior of geosynthetics, on subjects such as mechanical properties of geotextiles and geomembranes, interface friction between geosynthetics, durability of geotextiles and geomembranes, and behavior of geosynthetics under external actions (temperature, loading). Two notable examples are singled out from this body of work because they changed how the geosynthetics community perceived geomembrane behavior.

Wrinkles are undesirable geomembrane features, especially in landfills, because they ruin the good contact between compacted clay and geomembrane, thus increasing the rate of flow through geomembrane defects. Hence the practical interest in studying the mechanism of geomembrane wrinkle development. In 1992, Giroud and Morel [9] showed that the main parameter explaining the differences in wrinkle development between different geomembranes was the bending modulus of geomembranes and not the coefficient of thermal expansion, as it was assumed due to the absence of a unifying framework to account for observations of wrinkle development following geomembrane placement.

A more dramatic change of perception concerns the safety of design of applications of high density polyethylene (HDPE) geomembranes. In 1980, Giroud asked for the stress-strain curve for the HDPE geomembrane liner prescribed in the design report for the Proton Decay Experiment reservoir liner [10]. The curve showed a yield peak, implying an allowable strain equal to yield strain of a few percent –compared to 700 percent promoted by manufacturers–, which meant that the geomembrane could fail at places without good contact with the reservoir walls; Giroud recommended a design modification to reduce the strains in the geomembrane but the client dismissed Giroud’s concerns [11]. The liner indeed failed as and where predicted by Giroud on first filling of the reservoir. The hole was found and repaired; the repair together with the design modification initially recommended allowed a second successful filling of the reservoir. Giroud had realized that the 700% strain measured under ideal laboratory conditions was not relevant to the behavior of HDPE geomembrane in the field where minor scratches on the geomembrane surface would cause failure at the yield strain, since all geomembranes are bound to be scratched in the field. The mechanism is as follows: the scratch reduces the geomembrane thickness, thereby increasing the stress in the scratch until failure occurs in the scratched area while keeping the stress and strain slightly lower than the yield stress and strain in the rest of the geomembrane. In other words, the scratch acts as a fuse and the average strain (or apparent strain) over the entire geomembrane is approximately the yield strain while the strain in the scratch is the strain at rupture (e.g. 700%). These findings were rigorously demonstrated in a paper presented in 1984 at the International Conference on Geomembranes [12] and, despite initial strong opposition by the HDPE geomembrane manufacturer, were adopted by design engineers, thus changing the state of practice.

A related example of the mechanical behavior of geomembranes concerns stress and strain concentration next to geomembrane seams [13]. The basis of the theoretical analysis is that the two geomembranes connected by a seam are not initially in the same plane and, as a result, the seam rotates, as described conceptually in the 1984 paper discussed in the previous paragraph. The seam rotation induces bending moments and, hence, additional tensile strains; Giroud et al. (1995) [13] present the method for calculating these additional strains. Apart from a very inviting introduction, which makes it difficult for the reader to put it down (the equivalent of a page-turner for popular books), the paper is written with a clarity that guides readers and helps them follow every assumption made and every step of the analysis. What is more, it includes a detailed calculation example demonstrating the application of the methodology for three different seam types. Wrapping up, the authors discuss thoroughly (i) situations deviating from those assumed (e.g. non-mechanical processes generating tensile stresses, tensile stress in short lab specimens vs in the field) as well as (ii) practical consequences including practices to minimize the extra tensile strains. More than two decades later, the same problem is studied experimentally by Kavazanjian et al. (2017) [14] using digital imaging correlation analysis. The description of their experimental method matches in clarity the description of the analytical method of Giroud et al. (1995). The results of Kavazanjian et al. (2017) [14] confirm the concentration of strains in the vicinity of the seam. The average strain concentrations were, according to the authors, “reasonably close to those established with the Giroud et al. (1995) equations”. However, the maximum strains adjacent to the seams were “significantly greater” that the respective strains predicted with the Giroud et al. (1995) equations [13]. Specifically, “significantly greater” refers to 1.4 to 2.0 times greater. Kavazanjian et al. (2017) [14] believe that this difference is “likely due to nonuniformities and imperceptible imperfections along the seam”.

In this final category belong more than 150 publications with design-related themes truly tailor-made to the engineer’s needs: liner system design (70 papers), design of liner system drainage (38 papers), slope stability (29 papers), filters (22 papers) and road design (18 papers). The focus of this selective presentation will be on the recurrent themes, i.e. the themes periodically revisited and refined as already mentioned: filters, flow rates through holes of geomembrane liners, geosynthetics in unpaved road design and wind uplift of geomembrane liners.

Filters

Giroud worked for about 30 years on design criteria for geotextile filters and in so doing helped the geotechnical community understand better filter requirements for granular materials, as he demonstrated in his Terzaghi Lecture presented in 2008 [15] and the related 2010 paper [16]. The reader is advised to begin with Giroud’s first paper on filter criteria, published in 1982 [17], which adapts for geotextile filters the permeability and retention criteria developed for granular materials, because it helps understand the two main ideas of this work. The first idea is to ignore the tail parts of the gradation curve of the soil in contact with the filter (i.e. to consider only the central linear part of the curve and extend it to the 0% and 100% of the grain size distribution). The second idea is to differentiate between stable soils with coefficients of uniformity (C_u) less than 3 and unstable soils with coefficients of uniformity greater than 3: for the unstable soils, the filter criteria apply to the truncated part of the gradation curve for the finer portion of the soil with coefficient of uniformity equal to 3. The fully developed version of the design criteria for geotextile filters includes two more criteria, the porosity criterion and the thickness criterion [16]. Giroud’s work on design criteria for geotextile filters ends up elucidating design criteria for granular materials, for which the porosity and thickness criteria are automatically met [15]. However, Terzaghi’s classical retention criterion for granular materials is valid only for soils with small coefficients of uniformity; Giroud’s criteria (2010) [16] are valid for soils with large coefficients of uniformity as well.

After the completion of the 2^nd Int. Conf. on Geotextiles that took place in 1982 in Las Vegas, Andre Rollin writes in his closing report on four sessions on drainage that the large number of filtration criteria proposed and used seems to be justified by the many different types of problems. Have we converged through the years? Has Giroud’s work helped in this regard?

We asked Shobha Bhatia and Eric Blond to share thoughts about these questions.

SHOBHA BHATIA

In 1970, Dr. Giroud engineered the geotextile filter for the Valcros Dam during a period when the geotechnical community was just beginning to acknowledge geotextiles and their potential applications as filters. Subsequent studies have consistently validated the long-term efficacy of the Valcros Dam geotextile filter, underscoring the robustness of his pioneering design.

Dr. Giroud's extensive research on granular and geotextile filters has established the foundational principles of geotextile filtration science, significantly advancing the field. His groundbreaking insights have guided numerous researchers and influenced generations of engineers. The Geotextile Filter Design Guide (Luettich et al., 1992) remains an essential reference in the geosynthetics community, providing critical guidance globally.

Among his numerous innovations, Dr. Giroud’s concept of a two-layer geotextile filter (Giroud et al., 1998) is particularly noteworthy, warranting further investigation to fully realize its potential. In his 2008 Terzaghi Lecture, "Criteria for Granular and Geotextile Filters," he meticulously differentiated between granular and geotextile filters, offering a fundamental understanding of filtration principles that continues to inform contemporary engineering practices.

Regarding the question of multiple filtering criteria, a consensus has not yet been reached. This may be since certain filtering criteria have proven effective only in specific geotextile filter applications. As previously noted, Dr. J.P. Giroud's work provided a clear understanding of geotextile filters and the distinctions between granular and geotextile filters. Building on this foundation, research continues to expand knowledge of geotextile filters across various applications. For instance, in geotextile tube dewatering—where slurries have a high water content—some traditional geotextile filter criteria are not applicable. Therefore, ongoing efforts are required to develop new performance criteria to address these challenges effectively.

References

Luettich, S.M., Giroud, J.P., & Bachus, R.C., 1992, “Geotextile Filter Design Guide”, Geotextiles and Geomembranes, Special Issue on Geosynthetics in Filtration, Drainage and Erosion Control, Vol. 11, Nos. 4-6, pp. 355-370.

Giroud, J.P., Delmas, P., & Artières, O., 1998, “Theoretical Basis for the Development of a Two-Layer Geotextile Filter”, Proceedings of the Sixth International Conference on Geosynthetics, Vol. 2, Atlanta, Georgia, USA, March 1998, pp. 1037-1044.

Giroud, J.P., 2008, ASCE Terzaghi Lecture, “Criteria for geotextile and granular filters”

ERIC BLOND

Building on Prof. Bhatia’s remarks, JP Giroud indeed was the first engineer to use a geotextile as a filter in a large dam. This has been a trigger for much of his future work, in filtration as well as lining of hydraulic structures. Overall, his initiative has opened and shaped the way things are done today in hydraulic applications of geosynthetics. I believe that the systematic numerical approach carried by JP to analyze filtration must serve as a basis for future research. Soil behavior is well known, but we still miss the geotextile property, or properties, that will reflect the predictions of the theoretical analysis.

One of the reasons there are still many different filtration criteria is that the selection and determination of the geotextile significant property used in filtration criteria has also been controversial. Opening size is a key parameter for essentially every filtration criterion published so far, but opening size measurement is not universal and reliable. For example, there is no relation between opening sizes determined in Europe or in North-America.  In fact, the ‘opening size’ published using one standard may differ from the one published per another standard by a factor of a few. Historically, opening size measurement techniques were developed by geotechnical engineers to mimic sieves. Since then, the industry has developed capillary-based methods, measuring the pore-size distribution, which are better suited to the structure of geotextiles. Innovative concepts such as the number of constrictions, published by Giroud 25-30 years ago, start to be better understood. Piggybacking on Giroud’s work, but using measurements better-suited for geotextiles may, finally, lead to the reduction of the number of filtration criteria.

It is important to highlight that, when avoiding gross conceptual errors, geotextile filters perform, in fact, very well in most cases. Filtration performance is typically questioned by engineers only in critical applications such as dams — even though one of the first large-scale uses of geotextiles as filters was in a dam, over half a century ago, by JP Giroud!

In my opinion, further advancing the knowledge on geotextile filtration performance in large structures, such as dams, will have to be driven by users. The reason is simple: the ratio ‘Risk / Business volume’ is too high for such critical applications, i.e., manufacturers are unlikely to see a return on their investments. However, geosynthetics are, in fact, one of the best tools geotechnical engineers have to contribute to the decarbonization of their work. Decarbonization is, or will soon be, among the most important priorities in many countries. Hence, advancing science to expand the use of geotextile filters in large, risk-adverse structures may be driven by users, using theoretical analysis developed by Giroud and recent developments in geotextile characterization methods. Ideally, we would like to have more Girouds, i.e., people being both users and researchers at the same time.

Flow through geomembrane holes

This two-decade-long string of papers is a quintessential example of Giroud’s relentless focus on improving design methods and is worth a detailed improvement-by-improvement presentation. It is yet another example of shifting perceptions about geomembranes by the geosynthetics community from a supposedly impermeable material to a material with imperfections –holes in this case– in the field [18]. These imperfections necessitate estimating rate of leakage, which is crucial for landfills. The beginning is made with a two-part paper (Giroud & Bonaparte 1989a,b) [19, 20] that sets the stage for the study of a composite liner consisting of a geomembrane overlying a compacted clay or a geosynthetic clay liner; the goal is to determine flow rate through a geomembrane hole with a graphical method, for two cases of good and poor quality of contact between the geomembrane and the underlying clay. Recommendations for hole sizes and frequency are also provided. The main idea is to bound the flow rate through a hole with two simple closed-form equations for its absolute minimum and absolute maximum values (varying as much as seven orders of magnitude) and to establish two key “anchor” points, for perfect and excellent contact between the geomembrane and the underlying soil. The equation for the perfect contact is again of the simple closed-form type, whereas the equation for the excellent contact is based on published empirical data. Excellent contact is considered the best possible field condition. The flow rates for the more probable in the field conditions of “good contact” and “poor contact” are found by interpolation from the curve constructed with the four bounding and anchoring points, with the help of a fifth anchoring point for a conceivable worst geomembrane-soil contact at field conditions. To save the engineer the effort to go through the graphical solution, Giroud et al. (1989) [21] construct 500 curves with a range of typical parameters and from them determine fitting parameters for flow rate equations for good and poor contact that are functions of the contained liquid height, the area of the geomembrane hole and the hydraulic conductivity of the underlying clay. Due to the assumption that the hydraulic gradient of flow is equal to one, the equations are valid for liquid height at most equal to the thickness of the clay. Then Giroud et al. (1992) [22] use an improved (but internally inconsistent) expression for the hydraulic gradient that is related to the geometry of the problem and propose expressions for circular, square, rectangle and infinitely long holes (e.g. a defective seam), without a limitation on the liquid height. They state clearly that the assumption made for the flow domain of the rectangular hole “has not been verified experimentally or through a more rigorous analysis”. Finally Giroud (1997) [23] removes the inconsistency of the hydraulic gradient. The refined equations have the same format and come in pairs for good and poor contact. However, because the equations are derived by fitting of results produced using the Giroud et al. (1992) equations over a range of input parameters, the Giroud (1997) equations are valid for liquid height as high as 3m.

Then comes a paper by Touze-Foltz and Giroud (2003) [24] that sets the standard for a clearly-written public statement for a previous method made obsolete by an improved replacement. In the preceding years, new (and cumbersome) analytical solutions had become available and shown that the solutions for rectangle and infinitely long openings, in the exact words used by Touze-Foltz and Giroud (2003) [24], “were flawed”. By generating again a large number of analytical solutions, they propose an improved set of equations for long openings, as well as for defective wrinkles (i.e. wrinkles with holes), while Giroud’s (1997) equations [23] for circular holes for good and poor contact remain the same. Their Table 3 summarizes valid old and new solutions and Section 6.2 delineates clearly the range of their applicability (or the limits of their validity) in terms of hole dimensions, liquid height (again up to 3m), hydraulic conductivity and thickness of clay. Two more papers complete this series of continuous improvement and extension of easy-to-use expressions for calculating flow rates through geomembrane holes. Giroud and Touze-Foltz (2005) [3] improve the expression for elongated holes of finite length, noting that it is not safe to neglect flow close to the edges. The message of the flawed equations for elongated openings by Giroud et al. (1992) [22] is repeated herein and even more loudly, as it has a section of its own (Section 4.3) titled: “Obsolescence of equations by Giroud et al. (1992) for defects of finite length”. Then, Touze-Foltz and Giroud (2005) [25] extend the applicability of their solutions to large circular holes of diameter up to 0.6 m. It is reiterated that, to produce results for the entire containment facility, all these methods require assumptions for hole shape, size and frequency, which can be guided by the quality of construction and available statistics from the field. Giroud (2016) gives such recommendations in his Victor de Mello Lecture [26], which packages neatly and inspiringly his experience with geomembranes and explains differences when using geomembranes in landfills vs in reservoirs and dams. And just when we thought we have heard the last word, Giroud and Wallace (2016) [27] tackle the impact of wrinkles on the leakage flow calculation problem from a new angle. Instead of assuming wrinkle characteristics, they use the Giroud and Morel (1992) [9] equation for wrinkle formation and combine them with the flow rate equations previously developed. Over the decades since 1989, several research teams tackled the problem of flow through geomembrane holes and the role of wrinkles, in particular Kerry Rowe and his team at Queens University.

We asked Kerry Rowe and Malek Bouazza to share thoughts about the applicability of results from research on leakage through geomembranes and further research needs.

MALEK BOUAZZA

Giroud's early research on predicting leakage rates through geomembranes played a pivotal role in advancing liner system design for the waste containment industry. His work provided important insights into how defects impact leakage, leading to the development of analytical models that significantly improved liner system design. These models became indispensable for engineers and regulators in assessing the hydraulic performance of lining systems and compliance with different jurisdiction guidelines on acceptable leakage rates. As fundamental knowledge advanced, more sophisticated models became available, and they accounted for the presence and size of wrinkles and the location of the defect(s) on the wrinkle. Models based on probability analysis and machine learning have started to emerge recently but are yet to be embraced by practitioners. While practitioners increasingly adopt sophisticated models, Giroud’s models have stood the test of time. They remain widely used in practice, primarily as reliable screening tools, demonstrating their enduring value in providing a first estimate of leakage rates before more advanced analyses are conducted.

Over the decades since 1989, several research teams tackled the problem of flow through geomembranes. In particular, Rowe (1998), acknowledging Giroud’s significant advance in developing practical solutions for predicting leakage through holes, recognized that the disconnect between the predicted leakage using Giroud’s equations and a reasonable number of holes was not due to any error in the equations but due to the assumption of direct contact. Thus, the consequent leakage disconnect could be explained by holes and wrinkles, below which the geomembrane was not in direct contact with the underlying subgrade or clay liner. Rowe (1998) published an analytic solution to predict leakage for different lengths and widths of wrinkles with a hole, and his team at Queen’s University proceeded to document the extent of wrinkling and its relationship to solar radiation. In doing so, they again acknowledged and built upon work by Giroud and Morel (1992) with extensive field data. Rowe’s team demonstrated conclusively with large-scale simulators that wrinkles that are covered by a drainage layer do not disappear but remain as a somewhat smaller but significant version of the original wrinkle, irrespective of applied stress, due to arching in the soil around the wrinkle. Rowe then demonstrated that the leakage observed in double lined systems could easily be explained by a reasonable number of wrinkles with holes, particularly those at the toe of slopes. Subsequently Rowe’s team, in following Giroud leadership in developing his original equations, expanded the range of solutions considering the inverse situation of the tailings storage facilities where a hole in the geomembrane is covered by relatively low permeability tailings and they developed analytical solutions for these cases following a suggestion by Giroud in a discussion of their experimental work. In an interview, Rowe noted the famous words of Sir Isaac Newton in a letter to Robert Hooke in 1675 “if I have seen further, it is by standing on the shoulders of giants” and stated that within the geosynthetics world that giant is JP Giroud. Rowe, followed by saying “JP’s dedication, thoroughness, and devotion to advancing engineering practice through good science has been an inspiration to all of us who have followed it in his giant footsteps”.

Reference

Rowe, R. K., 1998, “Geosynthetics and the minimization of contaminant migration through barrier systems beneath solid waste”, Keynote paper in Proceedings of the 6th International Conference on Geosynthetics, Atlanta, Vol. 1, pp. 27–103.

Geosynthetics in unpaved road design

The design of geosynthetics in unpaved roads, similar to leakage through geomembranes, is another example of Giroud starting a line of research that allowed future improvements by other researchers and himself.  The story is told in a 2023 paper on the use of geosynthetics in roads [1]. The Giroud & Noiray (1981) [2] empirical method made possible to calculate the reduction of thickness of the base when a geotextile is placed between the base and the subgrade. Giroud and Han (2004a,b) [28, 29] improved the method by considering both geogrids and geotextiles and accounting for additional parameters. In addition, they calibrated the new method with data that had become available after the mid 1990s. Several computer programs and design tools have been developed to facilitate the use of the Giroud-Han method for unpaved road design. It is worth going back to the original Giroud & Noiray paper for some history: it appeared in the ASCE Geotechnical Journal in September 1981, and was the journal’s first paper dealing entirely with geosynthetics, as noted by Bob Koerner in his discussion of it. That the paper addressed a real need is evidenced by the discussion it elicited: six extensive discussion pieces by renowned experts which, together with the closure, nearly amount to another paper in the December 1982 issue!

Wind uplift of geomembrane liners

One more string of papers with successive refinements over 15 years concerns design against uplift of geomembrane created by the wind lowering the atmospheric pressure on portions of exposed geomembranes on landfill covers and side slopes of landfills and reservoirs. Giroud et al. (1995) [30] presented a design method for the necessary resistance of the geomembrane against tensile failure, extended by Zornberg and Giroud (1997) [31] and completed by Giroud et al. (1999) [32] with the design method for the necessary resistance of the geomembrane anchor. The work presented in these publications made possible to design and construct in 1997-1998 the first landfill with an exposed geomembrane cover, as described in the “Engineer” Section [33]. In 2006, Giroud and coworkers [34] presented a method for designing geomembrane anchors that is independent of the geomembrane properties, thus facilitating evaluation of alternative anchor designs and geomembrane materials. In the most recent paper of the series, Giroud (2009) [35] revisits the implicit Giroud et al. (1995) [30] equation for the geomembrane strain in the case where the geomembrane has a linear tension-strain curve, which admits an iterative solution, and proposes an approximate explicit solution that is very accurate for the entire range of geomembrane strains typically considered in design.

We cannot quantify the impact on engineering practice of the design methods presented in this section because (i) we do not ask such questions and, as a result, (ii) we have not come up with a systematic way to answer –preferably quantitatively– these questions. Research in applied fields of practice, e.g. Engineering, Education, Medicine, aims to improve existing practices and create new ones. Such research is deemed to be useful if improvements and new practices are indeed being applied. Hence, the litmus test for the direct usefulness of research projects in applied fields is whether their results have been used in practice. This test can be performed by soliciting input from the intended recipients of the research results, i.e. engineering consultants and contractors, instructors, physicians. Strangely, although the need for performing usefulness tests has been recognized [36], reporting on test outcomes is scarce [37].

Lacking a metric to assess usefulness of research results in practice, we turned to Ed Kavazanjian and Richard Thiel to close the “Researcher” Section with their thoughts on the impact of Giroud’s research.

ED KAVAZANJIAN

JP Giroud was a pioneer in investigating geosynthetics behavior and developing geosynthetics design methodologies at a time when there were few, if any, attempts to quantify the relevant properties of geosynthetics and relate them to geosynthetics performance. Almost all of the analyses used to quantify geosynthetics behavior in practice today owe their genesis to JP Giroud. Even those which he did not have a direct hand in developing are often based on an initial methodology for quantifying behavior developed by JP and use geosynthetics property relationships developed by JP. JP’s work, while always analytically rigorous and backed by sound research, was characterized by the philosophy of “a commitment to rationality” that he instilled in the researchers and practitioners working with him. Challenged to develop a rational design for some geosynthetics application, JP would invariably come up with a rational and rigorous way to quantify geosynthetics behavior that was accessible to practicing engineers. 

RICHARD THIEL

The great value of Giroud’s technical writings is their immediate relevance to practical design applications.  His works are made useful to practitioners by virtue of Giroud’s elegant exposition of the problem statements, precise definitions, clear descriptions of the physical context, step by step derivations well supported by engineering mathematics and physics, relevant and clearly worked out design examples, relevant supplementary discussions, and concise conclusions.  The result is that Giroud’s works have significantly advanced the field of containment system design, leading to defendable solutions that enhance the understanding of the mechanisms, sensitivities, limitations, reliability, and functionality of these types of designs.  More than anything, Giroud’s works provide outstanding examples of how a design practitioner might approach and work out solutions for design problems.

From “Geosynthetics in unpaved road design”

[1] Giroud, J.P., Han, J., Tutumluer, E. & Dobie, M., 2023, “The use of geosynthetics in roads”, Geosynthetics International, 30, No. 1, pp. 47-80, with Supplemental Documents, https://doi.org/10.1680/jgein.21.00046. [Stating definitions: see Section 2.1.]

[2] Giroud, J.P. & Noiray, L., 1981, “Geotextile-Reinforced Unpaved Road Design”, Journal of the Geotechnical Division, ASCE, Vol. 107, No. GT 9, September 1981, pp. 1233-1254, https://doi.org/10.1061/AJGEB6.0001187 (Discussion and closure Vol. 108, GT 12, December 1982, pp. 1654-1670) [Acknowledging assumptions: see Conclusions Section where the validity of assumptions is revisited.]

From “Flow through geomembrane holes”

[3] Giroud, J.P. & Touze-Foltz, N., 2005, “Equations for calculating the rate of liquid flow through geomembrane defects of uniform width and finite or infinite length”, Geosynthetics International, Vol. 12, No. 4, pp. 191-204, https://doi.org/10.1680/gein.2005.12.4.191 [Acknowledging obsolescence of earlier work: see Sections 4.2 & 4.3.]

[4] Giroud, J.P., 1968, “Settlement of a linearly loaded rectangular area”, Journal of the Soil Mechanics and Foundation Division, ASCE, 94, SM 4, Proc. Paper 6021, July 1968, pp. 813-831, https://doi.org/10.1061/JSFEAQ.0001174

[5] Poulos, H.G. and Davis, E.H., 1974, “Elastic solutions for soil and rock mechanics”, John Wiley, 411 p.

[6] Giroud, J.P., 1972, “Tables pour le calcul des fondations”, Vol. 1: Tassements, Dunod, Paris, France, 360 p. (in French) [link]

[7] Giroud, J.P., 1973, “Tables pour le calcul des fondations”, Vol. 2: Tassements, Dunod, Paris, France, 505 p. (in French) [link]

[8] Giroud, J.P., Tran-Vo-Nhiem & Obin, J.P., 1973, “Tables pour le calcul des fondations”, Vol. 3: Force portante, Dunod, Paris, 445 p. (in French) [link]

Tables Link: http://www.geotech-fr.org/publications/tables-de-giroud

[9] Giroud, J.P., & Morel, N., 1992, “Analysis of Geomembrane Wrinkles”, Geotextiles and Geomembranes, Vol. 11, No. 3, pp. 255-276.  https://doi.org/10.1016/0266-1144(92)90003-S (Erratum: 1993, Vol. 12, No. 4, p. 378.)

[10] Giroud, J.P. & Stone, J.L., 1984, “Design of Geomembrane Liner for the Proton Decay Experiment”, Proceedings of the International Conference on Geomembranes, Vol. 2, Denver, CO, USA, June 1984, pp. 469-474. [link]

[11] Giroud, J.P., 2019, “Lessons learned from case histories of reservoirs lined with geomembranes”, Revue Française de Géotechnique, Vol. 159, No. 2, 13 p., https://doi.org/10.1051/geotech/2019014

[12] Giroud, J.P., 1984a, “Analysis of Stresses and Elongations in Geomembranes”, Proceedings of the International Conference on Geomembranes, Vol. 2, Denver, CO, USA, June 1984, pp. 481-486. [link]

[13] Giroud, J.P., Tisseau, B., Soderman, K.L., & Beech, J.F., 1995, “Analysis of Strain Concentrations Next to Geomembrane Seams”, Geosynthetics International, Special Issue on Design of Geomembrane Applications, Vol. 2, No. 6, pp. 1049-1097, https://doi.org/10.1680/gein.2.0046

[14] Kavazanjian, E., Andresen, J. & Gutierrez, A., 2017, “Experimental evaluation of HDPE geomembrane seam strain concentrations”, Geosynthetics International, Vol. 24, No. 4, pp. 333–342. https://doi.org/10.1680/jgein.17.00005

Filters

[15] Giroud, J.P., 2008, ASCE Terzaghi Lecture, “Criteria for geotextile and granular filters” [link]

[16] Giroud, J.P., 2010, “Development of criteria for geotextiles and granular filters”, Prestigious Lecture, Proceedings of the 9th International Conference on Geosynthetics, Guarujá, Brazil, May 2010, Vol. 1, pp. 45-64, https://library.geosyntheticssociety.org/proceedings/prestigious-lecture-development-of-criteria-for-geotextile-and-granular-filters-pdf/

[17] Giroud, J.P., 1982, “Filter Criteria for Geotextiles”, Proceedings of the Second International Conference on Geotextiles, Vol. 1, Las Vegas, NV, USA, August 1982, pp. 103-108.

Flow through geomembrane holes

[3]

[18] Giroud, J.P., 1984b, “Impermeability: The Myth and a Rational Approach”, Proceedings of the International Conference on Geomembranes, Vol. 1, Denver, CO, USA, June 1984, pp. 157-162. [link]

[19] Giroud, J. P. & Bonaparte, R., 1989a, “Leakage through liners constructed with geomembranes-Part I. Geomembrane Liners”, Geotextiles and Geomembranes, Vol. 8, No. 1, pp. 27-67, https://doi.org/10.1016/0266-1144(89)90009-5

[20] Giroud, J. P. & Bonaparte, R., 1989b, “Leakage through liners constructed with geomembranes-Part II. Composite Liners”, Geotextiles and Geomembranes, Vol. 8, No. 2, pp. 71-111, https://doi.org/10.1016/0266-1144(89)90022-8

[21] Giroud, J.P., Khatami, A. & Badu-Tweneboah, K., 1989, “Evaluation of the rate of leakage through composite liners”, Geotextiles and Geomembranes, Vol. 8, No. 4, pp. 337-340, https://doi.org/10.1016/0266-1144(89)90016-2

[22] Giroud, J.P., Badu-Tweneboah K. & Bonaparte, R., 1992, “Rate of leakage through a composite liner due to geomembrane defects”, Geotextiles and Geomembranes, Vol. 11, No. 1, pp. 1-28, https://doi.org/10.1016/0266-1144(92)90010-8

[23] Giroud, J.P., 1997, “Equations for calculating the rate of liquid migration through composite liners due to geomembrane defects”, Geosynthetics International, Vol. 4, Nos. 3-4, pp. 335-348, https://doi.org/10.1680/gein.4.0097

[24] Touze-Foltz, N. & Giroud, J.P., 2003, “Empirical equations for calculating the rate of liquid flow through composite liners due to geomembranes defects”, Geosynthetics International, Vol. 10, No. 6, pp. 215-233, https://doi.org/10.1680/gein.2003.10.6.215

[25] Touze-Foltz, N., & Giroud, J.P., 2005, “Empirical equations for calculating the rate of liquid flow through composite liners due to large circular defects in the geomembrane”, Geosynthetics International, Vol. 12, No. 4, pp. 205-207, https://doi.org/10.1680/gein.2005.12.4.205

[26] Giroud, J.P., 2016, “Leakage Control using Geomembrane Liners”, The Victor de Mello Lecture, Soils and Rocks, São Paulo, Brazil, Vol. 39, No. 3 September-December 2016, pp. 213-235. https://doi.org/10.28927/SR.393213

[27] Giroud, J.P. & Wallace, R.B., 2016, “Quantified Impact of Geomembrane Wrinkles on Leakage Through Composite Liners”, GeoAmericas 2016, Proceedings of the Third PanAmerican Conference on Geosynthetics, Miami Beach, USA, April 2016, 10 p.

Geosynthetics in unpaved road design

[1, 2]

[28] Giroud, J.P. & Han, J., 2004a, “Design Method for Geogrid-Reinforced Unpaved Roads. I Development of Design Method”, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 130, No. 8, August 2004, pp. 775-786, https://doi.org/10.1061/(ASCE)1090-0241(2004)130:8(775) (Discussion and closure, Vol. 132, No. 4, pp. 547-551)

[29] Giroud, J.P. & Han, J., 2004b, “Design Method for Geogrid-Reinforced Unpaved Roads. II Calibration and Applications”, Journal of Geotechnical and Geoenvironmental Engineering, Vol. 130, No. 8, August 2004, pp. 787-797, https://doi.org/10.1061/(ASCE)1090-0241(2004)130:8(787) (Discussion and closure, Vol. 132, No. 4, pp. 547-551)

Wind uplift of geomembrane liners

[30] Giroud, J.P., Pelte, T., & Bathurst, R.J., 1995, “Uplift of Geomembranes by Wind”, Geosynthetics International, Special Issue on Design of Geomembrane Applications, Vol. 2, No. 6, pp. 897-952, https://doi.org/10.1680/gein.2.0042 (Errata, 1997, Vol. 4, No. 2, pp. 187-207, and 1999, Vol. 6, No. 6, pp. 521-522.)

[31] Zornberg, J.G., & Giroud, J.P., 1997, “Uplift of Geomembranes by Wind - Extension of Equations”, Geosynthetics International, Vol. 4, No. 2, pp.187-207, https://doi.org/10.1680/gein.4.0093 (Errata: 1999, Vol. 6, No. 6, pp. 521-522).

[32] Giroud, J.P. Gleason, M.H., & Zornberg, J.G, 1999, “Design of Geomembrane Anchorage Against Wind Action”, Geosynthetics International, Vol. 6, No. 6, pp. 481-507, https://doi.org/10.1680/gein.6.0161

[33] Gleason, M.H., Germain, A.M., Vasuki, N.C., & Giroud, J.P., 1999, “Design and Construction of an Exposed Geomembrane Cover for a Solid Waste Landfill”, Proceedings of the Seventh International Landfill Symposium, Sardinia, Italy, October 1999, Vol. 3, pp. 335-342.

[34] Giroud, J.P., Wallace, R.B., & Castro, C.J., 2006, “Improved methodology for geomembrane wind uplift design”, Proceedings of the 8th International Conference on Geosynthetics, Yokohama, Japan, September 2006, Vol. 1, pp. 225-230, https://library.geosyntheticssociety.org/proceedings/a-2-07-improved-methodology-for-geomembrane-wind-uplift-design-pdf/

[35] Giroud, J.P., 2009, “An explicit expression for strain in geomembrane uplifted by wind”, Geosynthetics International, Vol. 16, No. 6, pp. 500-502, https://doi.org/10.1680/gein.2009.16.6.500

[36] Sullivan, G.M., Simpson, D. et al., 2014, “Redefining Quality in Medical Education Research: A Consumer’s View”,  Journal of Graduate Medical Education, 6(3):424-429, https://meridian.allenpress.com/jgme/article/6/3/424/34152/Redefining-Quality-in-Medical-Education-Research-A

[37] Fraser, K., Tseng, T.-L.B. & Deng, X., 2018, “The Ongoing Education of Engineering Practitioners: How Do They Perceive the Usefulness of Academic Research?”, European Journal of Engineering Education, 43(6):860-878, https://www.tandfonline.com/doi/full/10.1080/03043797.2018.1450847