Ebook: Proceedings of the 17th International Conference on Soil Mechanics and Geotechnical Engineering (Volumes 1, 2, 3 and 4)

The International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE), the Egyptian Geotechnical Society, the Government of Egypt, and the city of Alexandria invited academics and practitioners in the field of geotechnical and ground engineering from around the world to attend the 17^th International Conference on Soil Mechanics and Geotechnical Engineering (17^th ICSMGE) on 5 to 9 October 2009. This quadrennial event ranks among the premier events in the field of geotechnical and ground engineering worldwide, and was held at the spectacular, international award-winning Bibliotheca Alexandrina on the coast of the Mediterranean Sea. A technical exhibition, a major component of the event, was held in parallel to the conference (5-8 October).

The geotechnical challenges the world faces are becoming increasingly more complex and interrelated. Geotechnical engineers have had to expand their thinking and develop new technologies to better integrate socio-economic and environmental issues into engineering solutions at the surface and below ground in our cities and towns, coastal areas and sea beds, and in a global context for the health of the earth. To prepare for the more challenging changes to come, closer collaboration among those who study, research, and practice geotechnical engineering is requisite. Thus, The Academia and Practice of Geotechnical Engineering was chosen as the main theme of the 17^th ICSMGE.

The 17^th ICSMGE provided a forum for academics and practitioners in the geotechnical engineering field to explore the future of the profession and what can be done to assure that society's needs and expectations are met. Interactive discussions, led by preeminent leaders in the field, addressed the research required to meet ever changing global issues. Participants also explored case studies that all could learn from, and identified the means and value in strengthening relationships among the engineering and construction communities, as well as the general public.

Egypt, the place where geotechnical engineering essentially began, was the ideal setting to determine the field's future directions.

P. Sêco e Pinto, ISSMGE President

M. Hamza, Chairman of XVII ICSMGE

Although cement-based grouts are widely used in geotechnical and geoenvironmental engineering applications, e.g. for the stabilisation of soft soils, their performance can be adversely affected by exposure to aggressive chemicals. The use of zeolites, which are alumino-silicates with rigid hollow structures, has recently been suggested as a means of enhancing the durability of cement-based grouts especially for sulphate attack. As a result, an experimental study was carried out to verify the potential improvements in the behaviour of cement-based grouts containing zeolites in various aggressive environments. This paper focuses on the durability of soft clays stabilised with cement-bentonite and cement-zeolite grouts and addresses the diversity in their behaviour. The aggressive environments applied included sulphate and acid solutions and freeze/thaw cycles. The impact of the aggressive environment is assessed using the unconfined compressive strength (UCS). The results showed a clear difference in behaviour between the cement-zeolite and cement-bentonite grouts with the former significantly outperforming the latter in their resistance to both sulphate and acid solutions, although the latter still maintained its superior resistance to freeze-thaw cycling. The strength was also generally much higher due to the pozzolanic nature of zeolite and hence also enhanced the UCS compared to cement grouts alone.

The paper deals with the at-rest earth pressure coefficient K_0NC and Poisson's ratio ν prediction for normally consolidated soils based on the connection between the effective friction angle φ^′ and its mobilized proportion φ^′_mob in the process of one-dimensional compression. After considering the existing correlations between these two parameters, the comparison with experimental data leads to both the validation of the existing theoretical K_0NC equation coming from the BRICK model and the proposal of an equivalent empirical K_0NC equation, derived without any assumptions. The same connection between φ^′ and φ^′_mob leads to interesting correlations, one theoretical and one empirical, between φ^′ and ν for normally consolidated soils. No laboratory data in terms of pairs (φ^′,ν) have been found at all in literature, and, therefore, experimental validation of these correlations is necessary.

The liquefaction potential of sand-silt mixtures is investigated in this study. There has been widespread debate over the effect of silt on the liquefaction resistance of saturated sand-silt mixtures. Some researchers have reported that by increasing the fine content the liquefaction resistance of the sand-silt mixtures increases. However, recent researches have shown that silty sands are more liquefiable than clean sands, which is in complete contradiction with the previous results. The first purpose of this study is to reveal the true effect of silt on resistance to liquefaction of sandy specimens by means of a series of load-control cyclic triaxial tests. These tests were conducted on sand-silt mixtures in various fine contents. In addition, the anisotropic behavior of the sand-silt mixtures was studied in this research by exploring the effect of the initial shear stress and stress reversal. The effect of stress reversal was studied by introducing a new parameter RC. The effect of this parameter was investigated in detail, and it was found that this parameter has a crucial role in the behavior of sand-silt mixtures.

The engineering properties of Portuguese processed steel slags (ISACs) are tested to evaluate the appropriateness of their use in transportation infrastructures and geotechnical works. The laboratory results are compared with values specified in the Portuguese standards for natural aggregates and with values found for natural aggregates of various geological origins. The elastic modulus is carefully evaluated in order to compare the two ISACs with two standard base coarse materials (granite aggregate 0/31.5mm and limestone aggregate 0/19mm). All laboratory results show that the national processed steel slags could be used in geotechnical works, and particularly in transportation infrastructures. The two ISACs demonstrated better mechanical properties than the standard, unbound, granular base, coarse materials.

Compaction grouting has some problems that are basically attributed to the little understanding of grouting mechanisms. Large-scale double-wall calibration chamber and injection systems have recently been developed to physically model and investigate the technique in the laboratory. This paper describes the main features of the developed systems and presents and discusses results of injections performed into sand samples under different confining pressures. The grouting mechanisms are discussed in terms of the variation with injection of the vertical displacement of soil surface, the volume change of soil, and the coefficient of earth pressure at rest (K₀). The results and discussions reveal that during injection the soil exhibits large deformations and increases in the lateral stress. After termination or during suspension of injection, the soil experiences creep deformation and lateral stress relaxation. The initial stress condition of soil highly influences the soil deformation. The soil volume change increases with injection, but at an attenuating rate. A unique relationship between the increase of K₀ with injection and the volume of injected grout is established.

Piping failure is among the most common failure modes for embankment dams. It is often related to the potential of the embankment material to de-flocculate and erode in the presence of water. Soil erosion is therefore one of the main factors affecting the safety and serviceability of earth structures. This paper presents the results of a laboratory testing program intended to study the effects of dry density, moisture content and curing time on the erodibility and dispersivity of two alluvial deposits aimed to be used as dam core material. One sample is a recent deposit obtained from the flood plains of the River Nile in Northern Sudan (Soil A) while the other (Soil B) is obtained from an adjacent area in the upper terraces of the Nile. Preliminary evaluation has shown that Soil A is slightly dispersive while Soil B is highly dispersive.

Specimens from the two samples were prepared in the laboratory at different moisture and density conditions and tested for dispersivity and erodibility using the pinhole test. Identical specimens were prepared, cured for different periods of time extending up to 18 months and tested. The results have shown that the erosion resistance of the slightly dispersive Soil A improved with increase in dry density when the moisture content is wet of optimum and with curing time for specimens with lower density and moisture content. However, the highly dispersive Soil B did not show significant improvement of its erosion resistance, neither with increase of its density nor with increase in curing time.

The degradation of aggregate is the factor that normally determines the service life of the ballast bed. Quite recently the use of crushed rock aggregate has expanded also to the structural layers beneath the ballast bed (subballast). To ensure sufficient frost protection for the track, the thickness of subballast in Finland is normally as much as 1.5-2.0 metres. The ballast degradation occurring in an actual track structure over decades was studied by sampling and extensive series of laboratory tests with a special view to the quality of fines. Many properties of the mineral fines of the analysed ballast samples generally differed relatively little from each other. Degradation of ballast aggregates results mainly from mechanical fragmentation and attrition caused by traffic loads and tamping, and in a few cases possibly from frost weathering. The chemical weathering after crushing of the ballast of Finnish railways is generally insignificant. In the absence of long-term use experiences, the research strived to forecast the degradation of the subballast crushed rock aggregates in cyclic loading apparatus with three separate loading plates. A total of 35 long-term cyclic loading tests equivalent to about 150-300 MGT were carried out varying grain size distribution, strength of the aggregate, amount of fine material and water in the aggregate, loading level and flexibility of the bottom. In the water saturated state the degradation of crushed rock aggregate was dramatically strong. Grading of crushed rock aggregate had a significant impact on the degradation.

Le papier présente les besoins géotechniques pour le dimensionnement des structures pétrolières par grands fonds et rappelle les propriétés spécifiques des sédiments de la pente continentale. Il décrit ensuite la stratégie de reconnaissance mise au point, insiste sur la complémentarité entre essais in situ et essais de laboratoire et montre comment la combinaison judicieuse des différentes données permet d'accéder aux paramètres d'ingénierie.

The critical state (or critical void ratio) line is the locus of void ratio-effective stress conditions achieved after shearing a soil to large displacement and after all net void ratio changes and effective stress changes are complete. The triaxial compression test is commonly used to define the critical state line of sandy soils. In this study, we present drained and undrained triaxial compression and ring shear tests that are used to define the critical state line of a silty sand sampled from the Mississippi River near Cape Girardeau, Missouri, USA. All specimens were prepared by pluviating the dry sand through air. The results show that both drained and undrained (or constant volume) triaxial and ring shear tests reach critical state at similar shear displacements prior to the onset of particle damage in the ring shear tests. A unique critical state line can be defined for these states. At larger shear displacements only possible in the ring shear tests, considerable particle crushing happens and dominates the sand behavior and only after very large shear displacements (>750 cm) particle crushing ceases to continue and a complete particle rearrangement is reached. At this state, the stresses and volume of the sand become constant which corresponds to the critical state of the crushed sand. A unique line can also be drawn for this state. These unique critical state lines indicate that they are not influenced by the drainage conditions and shearing modes.

The settlement estimation of a shallow foundation requires the laboratory determination of the soil modulus or the compression index by oedometer or triaxial tests. The oedometer soil samples, by whose testing the two indices are determined, present a certain disturbance during their extraction from the ground and sampler tube respectively. This fact, together with setting the samples to a stress/strain state different from the in situ ones, determines a deviation of the results from reality. The authors designed a new oedometer device, to decrease or eliminate the induced testing errors, that differs from the classical one by the followings: the test is performed directly on the soil specimen removed from the boreholes without sampling the 70 mm diameter and 20 mm height cylinders; the stress-strain and stress-voids ratio curves, to determine these two indices, are obtained on samples with a partial lateral confined strain, under a stress state close to the one in situ; the new oedometer device provides the condition to perform a plate load test and obtain the stress-settlement curve, based on which the vertical subgrade modulus and by correlation the soil modulus can be derived. Thus, the paper presents the general approach to perform these two types of tests and their corresponding individual stages to quantitatively assess the soil compressibility by the soil modulus and compression index, established for pre-existing and induced stress states as similar as possible to the in situ ones, before and after construction is performed.

Leakage of oil into the soil may occur due to several reasons. This leakage will result in the formation of soil layer mixed with oil. The mechanical soil properties may be influenced by the leaked oil. To investigate the compressibility parameters for oil contaminated sandy soil, an extensive testing program was carried out in the Geotechnical Engineering Laboratory at Ain Shams University in Egypt. The oil by-products used in the testing program were kerosene, solar, and used oil. Sand samples with different relative densities were mixed with the oil by-products, using 2 % to 15 % oil contents. Consolidation tests were carried out on the prepared oil contaminated sand samples. The results obtained from the testing program are Analyzed and discussed. The effects of oil viscosity, together with its percentage on the sloughing and the modulus of deformation are studied and presented. Finally, the general conclusions of the research are pointed out.

When soil liquefaction occurs in slightly sloping ground or near free-face topographic irregularities large horizontal displacements may occur due to the lateral spreading of the liquefied ground. This kind of ground failure may cause extensive damage to pile-supported structures as witnessed in several recent earthquakes (Chi-Chi 1999, Kobe 1995, etc). A systematic analysis of the detrimental effect of lateral spreading requires a sophisticated 3-D numerical analysis. Still, there is need for preliminary estimation of the response of deep foundations based on readily available data, such as the geometric and the mechanical characteristics of the foundation and the maximum anticipated displacement at the ground surface. For this purpose, a set of over 200 parametric numerical analyses were performed, with the pseudo static P-y method, in order to analyze the basic parameters affecting the pile behavior. The results of the parametric analysis have been consequently combined into design charts for the computation of the maximum developed pile head displacement and moment.

Soil stabilization with cement is a good solution for the construction of subgrades for roadway and railway lines, especially in “noble” foundations layers, under the platforms, and mostly in transition zones between embankments and rigid structures, where the mechanical properties of supporting soils are very much demand full. These solutions are especially attractive in line works where other ground improvement techniques are extensive and, therefore, very expensive. On the other hand, the economic and environmental costs of such works should be optimized with good balances between excavation and embankment volumes. For this purpose, the improvement of locally available soils can bring great advantages, avoiding a great amount in borrowing appropriate material, as well as the need of disposing huge volumes in deposits. This paper focus on the characteristics of two soils, Osorio sand and Botucatu residual sandstone (BRS), which can be converted to well accept materials to that purpose, if stabilized with cement. The study of soil stabilization with cement relies on the quantification of the influence percentage of cement and porosity that is adopted in the admixing process for different state and stress conditions. This influence will be evaluated from the analysis of unconfined compression strength (UCS) test results. This experimental framework will enable a good definition of mechanical parameters used in design of foundations and subgrades of railways platforms and for their execution quality control.

The Post Pampeano Formation is composed of high plastic clays and silts which was deposited in fresh fluvial water and in marine environments. Actually this formation covers the left bank of the Rio de la Plata and the Delta of the Paraná river. At some places the thickness of the deposit reach 30 m. In this work, the Post Pampean Formation was characterized by means of in situ and laboratory tests. The results were modelled by means of the Cam-Clay constitutive model. A procedure is described for the prediction of the undrained shear strength of the soil Formation if known: the index properties mean effective pressure and water content. The reported data will be used in a large-scale projected to be constructed in this soil Formation.

The Gateway Upgrade Project in the State of Queensland, Australia, is the largest road and bridge infrastructure project in the state's history. A statistical analysis of intact rock strength properties of the sub-horizontally interbedded sandstone stratum underlying the main river span of the duplication bridge was carried out using pre-construction geotechnical data. These findings were then compared with an analysis based on additional borehole data captured during construction. However, this has been confined to the additional data obtained at the southern pier location of the main span only for this paper. Having a borehole at each socket location at this pier showed that signification variation of ground conditions could occur locally between piles, even for the same pier location.

Given the data variation, an appropriate statistical density function is required for statistical modeling to asses the reliability of the design. Using the probabilistic models identified, the study undertakes to rationalize the design rock strength input model adopted for socket design. The impact of rock strength anisotropy on the design UCS is also investigated. The implications of using the design UCS with various probability distribution models to satisfy limit state material characterization requirements are briefly discussed. Assumption of normality in the data distribution was shown to have the potential to significantly affect the design values.

On présente dans cette communication les résultats d'un programme d'essais triaxiaux sur éprouvettes de 300 mm de diamètre, destiné à étudier le comportement mécanique d'un sol grossier à matrice de référence, composé d'une matrice sableuse et d'inclusions anguleuses, en termes des caractéristiques de rupture du matériau. On met en évidence l'influence de la fraction volumique des inclusions, de leur taille et de leur distribution granulométrique sur les comportements observés et sur les caractéristiques de rupture du matériau, quantifiées par l'angle de frottement interne.

To evaluate the geotechnical properties of a soil mass, different soil specimens were prepared in the lab by mixing various proportions of quartz, smectite, and illite. Liquid limit, plastic limit, and volume change behavior in terms of compression and swelling indices were measured according to the procedure mentioned in the respective ASTM methods. Those minerals are considered as the most common minerals that are found in expansive soils that include mudstone/clay stone, marl and shale. Such expansive soils are always considered as problematic soils in geotechnical engineering. The results show that plasticity index and liquid limit depend on the proportion of smectite and total clay content. A parabolic relationship could be observed between the liquid limit and proportion of smectite. Smectite is mainly controlling the plasticity characteristics. Likewise, volume change properties also depend on the proportion of smectite and liquid limit. A parabolic relationship was observed between the compression index and proportion of smectite, whereas a linear relationship was observed between the liquid limit and compression index. The results clearly show that we can estimate the coefficient of consolidation, and compression and swelling indices of a soil mass with reasonable accuracy with liquid limit and proportion of dominant clay mineral. This finding has a great significance in the geotechnical engineering because with a small amount of soil that can be collected from a boring core, we will be able to evaluate liquid limit, mineralogical composition, and clay content. Those parameters can be used to estimate the compressibility and hydraulic conductivity of a soil mass. They are very important in numerical simulation, foundation design, and many other applications in geotechnical engineering.

In this paper recently finished and on-going research of strength and deformation properties of Swedish fine-grained sulphide soils is presented. In the paper, some selected test results from the finished project are presented and recommendations are given for determination and evaluation of undrained shear strength of sulphide soils. A short description of the characteristics of the particular type of sulphide soil is also given. The overall purpose of the recently started research project is to improve the possibilities to predict long term settlements of structures founded on sulphide soils.

This paper describes the phenomenon of strain accumulation and different influencing parameters. Three groups of parameters are to be considered: parameters related to the current state of the soil, the current state of stress, and the characteristics of the load cycle applied. In particular, general approach and governing equations of an accumulation model, recently developed at the KHBO in close cooperation with the K.U. Leuven, are introduced. For validation of the model and determination of model parameters combined cyclic triaxial and bender element tests are carried out. The presented model is implemented in a three-dimensional finite element framework. Practical relevance of the topic is emphasized by a numerical example.

Cyclic triaxial tests have been widely used to determine the liquefaction susceptibility of soils in the laboratory. Tests have been mostly performed on clean sand and silty/clayey sand where the specimens are reconstituted in the lab. Two major criteria have been used to define liquefaction: 1) loss of effective confining pressure due to excess pore pressure build up (usually referred to as initial liquefaction) and 2) 5% double amplitude strain (±2.5% axial strain) with the later being the more popular choice in recent years. This paper compiles results from the literature and research by the author to address the applicability of using the 5% double amplitude strain criterion for liquefaction with the recent growth in testing non-traditional geo-materials.

Results of a laboratory research programme on the crushing of dry sands compressed under one-dimensional conditions, at vertical effective stresses σ^′_v up to 120 MPa, are reported in the paper. Tests have been carried out on calcareous bioclastic and on quartz sands, with initial coefficient of uniformity C_u ranging from 1.10 to 1.42. The crushing of bioclastic sand particles is considerable even at low stresses, whilst for quartz sands it becomes appreciable for stresses higher than 10 MPa. It is shown that the evolution of the grain-size distribution of a given sand can be effectively represented by the following relation between the absolute value of the decrement of the generic characteristic diameter ΔD_i and σ^′_v:ΔD_i=h/(K(1+Ce^−hlgσ′v)), where C, h, K are parameters depending upon the nature and the initial grain-size distribution of the sand. This Verhulst type relation properly accounts for the existence of an upper limit to ΔD_i. The analysis of published data shows that this type of relation also applies for other, quite different, sands.

Flowslide is a common type of failure of granular soil slopes. Although many flowslides can be explained using static liquefaction or instability behaviour of sand under undrained conditions, some of the failures might have occurred under essentially drained conditions, e.g. the Wachusett Dam case in 1907. Recent laboratory studies on Changi sand under axisymmetric conditions have shown that sand can become unstable under completely drained conditions. Based on these laboratory studies, new failure mechanisms for granular slopes were proposed. However, to date, most of the experiments on the instability behaviour of granular soils were carried out under axisymmetric conditions even though slope failures can only be simplified into plane-strain conditions. Although the behaviour of sand under plane-strain conditions has been studied by a number of researchers, the instability of sand under plane-strain conditions has seldom been investigated. In this paper, experimental data obtained from plane-strain tests are presented to illustrate the unstable behaviour of sand under both undrained and drained conditions. A comparison between the instability conditions observed under axisymmetric and plane-strain conditions is made. A unified instability condition which is applicable to both axisymmetric and plane-strain conditions is presented.