Ebook: Proceedings of the 15th European Conference on Soil Mechanics and Geotechnical Engineering

L'essai d'expansion in situ d'une cavité cylindrique peut s'appliquer à tous les types de matériaux, des plus mous aux plus résistants, pour déterminer leurs propriétés mécaniques. Les auteurs présentent un appareil permettant d'étendre le domaine du pressiomètre Ménard jusqu'à des pressions d'essai de 25 MPa, ainsi que ses premières utilisations dans des roches peu fracturées.

For the construction of Papadates dam a site investigation was conducted by means of three boreholes in which double packer p meability testing was conducted. The dominant geological formation found was Upper Eocene Flysch consisting of siltstone and san stone alternations. In this paper the results of the permeability tests are presented and the hydraulic behavior of the Flysch was c fied of three distinct modes: turbulent flow, laminar flow and fracture expansion. Attempts for correlating RQD with permeability proved to return poor Pearson coefficients.

In the west part of Albania, near the Adriatic Sea there is a large area of very problematic soils as organic cohesive soils and fine sands under the ground water table. These soils have high porosity and are under consolidated. This region is characterized by a big development of motor-ways, industries, costal constructions and tourism.

We would like to present in this papers the laboratory and in-situ tests and studies performed by the laboratory “A.L.T.E.A&GEOSTUDIO2000” for the determination of the behaviour of these soils under static and seismic loads. We will also give some recommendations about engineering measures that should be taken for the improvement of these characteristics.

Daugava River is the largest river in Latvia, and it has been developed for hydropower with the construction of dams at three sites namely Plavinas, Kegums and Riga HPP. In the 1960s the largest of the three hydroelectric power plants - Plavinas Power Plant, having a considerably higher head than the other two and a relatively large reservoir, was built up. It is built across an ancient pre-glacial river channel, which is filled with glacial deposits up to 137 m or more thick.

Since construction of the power plant the properties of these soils and their behaviour are tested and discussed. During 2009 drilling and sampling were performed close to the Plavinas Dam as a scope of the geotechnical investigation for construction of the additional spillway on the right side of the power plant. Part of the samples was used for testing of soil clasification and mechanical properties in Geotechnical laboratory of the University of Latvia. Based on the testing results soils were classified and their properties described. Testing results were compared to previous findings and geotechnical properties of the soils tested during construction of dam. The tested soils are similar to the soils under Plavinas dam concrete structures and detail analysis of the soil properties helps to explain the long term behavior of the Plavinas dam structures, the possible changes of the soil properties as a result of the loading and impact of the artesian groundwater pressure.

The paper presents the investigation program and slope stability analysis of an active landslide situated on National road DN 1, major traffic way in Transylvania, Romania. Slope stability analysis was performed using Geo Fine software, considering circular or polygonal sliding surfaces and using GFAS software, applying FEM method. The investigation program is continued by a monitoring program to determine movements on the site and ground water table variation. On the site were placed inclinometers and piezometers, where the slope stability analysis indicates a lower value of the safety factor than the acceptable one.

The building comprises a 200 metre tall tower and 20 metre deep basement in a densely developed urban area. The tower has a steel frame closed by glass panels. The vertical loads are transmitted to the ground by six mega-columns and by a core in the central area. The lateral load restraint is provided by a permanent slab placed according to the top-down method. This paper discusses the geotechnical issues associated with the project and the ground investigation carried out to assess both the variability of the underlying soils and the parameters for design. The large amount of information on ground conditions around the site at shallow depths was integrated with a site-specific investigation that reached depths of 80 metres. Soil parameters were extrapolated from cross-hole tests, which were carried out with two boreholes and from the measurements of the mechanical energy, pressures and torque (PAPERO tests) during drilling. The groundwater water level was found at approximately 20 metres depth. The information provided by the ground investigation allowed the design of the retaining wall and the foundation system and the selection of a construction technique that accounted for the urban context.

Dynamic Probings, whether Heavy, Medium or Light type (DPH, DPM, DPL), are state-of-the art methods for subsoil investigation used by Geotechnical Engineers in Europe. Dynamic Probings are used worldwide to determine geotechnical design parameters, and in Europe EC-7-2 (Ground Investigation and Testing) and EC-7-1 (Geotechnical Design) are the-up-to date standards. The uses of dynamic probings are important since the Cone Penetration Test (CPT) is found to be good only in soft to stiff cohesive soils and loose to medium dense sands.

Since the CPT cannot be used in dense sands, gravel or bedrock due to very high penetration resistances, DPH, DPM and DPL are mainly used for geotechnical investigations. In this study based on the approach by Zweck, who defined N₁₀*=10 / e (e = cm of the probe penetration per blow), the use of an automated data acquisition system was further developed to eliminate the influence of operators logging the data manually. By using a Field Geo-Measuring system (FGM) for dynamic probings, the quality, comparability and interpretability of the acquired data can be tremendously increased and, therefore, the automated system should be incorporated into EC 7-2 as a standard procedure for dynamic probings.

In the south-western part of Ukraine Black Sea plateau as a base foundation soils used semi-rock soils presented pontian limestone. In the state standards are no methods for determining their mechanical characteristics needed for the design of foundations and piles. The article presents the methodology and results of laboratory and field studies of these characteristics.

The Standard Penetration Test (SPT) is a test which provides assessment of soil properties and foundation design parameters. The Standard Penetration Test (SPT) is the in-situ soil characterization test, which is most widely used in the Americas. The N_SPT index depends not only on the soil properties and on the SPT sampler characteristics, but also on the energy delivered to SPT sampler during the hammer impact. The amount of energy that is transferred to the sampler depends on many factors, including the test equipment characteristics, soil conditions, and procedures followed during the test. For this reason, different N_SPT index values can be obtained for the same soil. Thus the N_SPT index should be normalized to a standard energy level that is equivalent to 60% of the nominal SPT hammer energy. Thus, it is of great importance to evaluate the actual energy input. The aim of this work is to show a suitable instrumented subassembly developed to assess the amount of energy that is effectively delivered to the sampler during a hammer impact. Results of SPT tests, conducted at the Experimental Research Site of the University of Sao Paulo (USP), showed the suitability of the instrumented subassembly to measure the amount of the energy that reaches the sampler, for the particular conditions. However, it should be verified if these conclusions are valid for tests performed in other situations involving the use of different types of hammer, different soil conditions and different instrumented subassembly positions.

Within the designed alignment of E-80 motorway in South East Serbia: Section Dimitrovgrad By-Pass the roadway alignment for the motorway and respective structures has been adopted. In the area of the abovementioned section it is foreseen to build the roadway in twin-tube tunnel Progon with total length of 1100 m.

The terrain is composed of clayey-gravely layers which are present in alternating sequence with sections of clay. The transitions from one into another lithological member are mostly gradual and unclear, seldom sharp, and consequently it is very difficult to single out the boundary between them.

In the course of analysis pertaining to geotechnical construction conditions, the geotechnical zoning of rock masses was carried out, i.e. the constraints were set for terrain parts along the designed tunnel alignment inside which there are similar conditions regarding the tunnel construction. Respecting the previously given criteria, according to geotechnical conditions, in the tunnel tube all singled-out quasi-homogenous zones can be classified into four significantly different categories of rock masses with specific conditions for tunnel excavation and support system.

Taking into account geotechnical conditions found on the location, size and shape of future tunnel, as well as advanced trends in the tunneling, as optimal technical and cost-effective solution, the tunnel construction as per SCL has been adopted. Under specific conditions, SCL thanks to its flexibility, can fulfill the requirements regarding the costs and construction deadlines, validity of the technical solution, and security of manpower and equipment.

The Standard Penetration Test has become increasingly popular in testing stiff to hard cohesive soils. Several correlations have been proposed that associate undrained shear strength with SPT blowcount in such soils. These correlations, often produced through significant data scatter, are typically restricted to specific materials and their main drawback is their not taking into account physical characteristics, often conveniently reflected in trivial lab processes, e.g. clay mineralogy manifested through Atterberg limits. A simplified empirical relationship is presented that correlates the undrained shear strength (c_u) of cohesive formations and the ‘as-measured’ SPT blowcount (N) attempting to reduce statistical scatter by addressing the important influence of characteristic physical properties on soil strength. The correlation derives from the statistical processing of data obtained in three different stiff to very hard cohesive formations in Greece, essentially clays and marls, each exhibiting a consistently identifiable geotechnical behaviour, in which a large number of ‘coupled’ SPT and lab UU triaxial tests were performed. Processing of the available data supports the common observation that the definition of a constant c_u / N ratio (even within the same material) is unrealistic. The inclusion of both water content (w) and plasticity index (PI) in such correlations is investigated and found to significantly improve the consistency of correlation results, indicating a linear dependence of the c_u / N ratio on (w) and logarithmic dependence on (PI). The identification of additional independent parameters affecting the procedure is also examined and basic directions for the orientation of future correlations are outlined.

Cette communication présentera une étude approfondie des facteurs d'influence et des corrélations possibles à partir de la technique des paramètres de forage. Une sondeuse géotechnique hydraulique instrumentée a été utilisée sur des planches expérimentales constituées de différents matériaux et stratification. L'observation de la variation des paramètres de fonctionnement de la machine permet d'avoir une idée assez précise de la position des transitions des couches de sols ou de roches de natures différentes. De même, la combinaison de ces paramètres permet d'approcher la variation de certains paramètres mécaniques et hydrauliques de ces terrains. Le programme de travail mis en œuvre lors de l'étude a été le suivant:

- établir la méthodologie pour aboutir à des grandeurs physiques corrélées aux paramètres mécaniques

- tester sur sites réels différentes planches expérimentales avec un programme d'essai visant à isoler les paramètres d'influence,

- appliquer la statistique à ces champs de données pour aboutir à des relations empiriques et théoriques.

Les résultats sont comparés à des essais de pénétration au carottier (SPT) et au pénétromètre statique avec piézocone.

Cette communication s'attachera à faire un état des pratiques et à présenter l'importance de l'écriture de protocole spécifique à cet essai qui doit être considéré comme un essai à part entière et doit être adapté à l'objectif de la reconnaissance.

Seismic surface methods are widely recognised has being the most cost effective way of evaluating seismic velocity in large areas, especially in sedimentary deposits were the soil profile is usually characterized by a seismic velocity increase with depth. In the case of volcanic massifs, it's common to have volcanic rock layers enclosed in volcanic sedimentary deposits, and in this case the isolated use of seismic surface methods can provide multiple models for the same field data. In this paper is going to be described a case study, of the combined use of various surface and borehole seismic techniques, in the determining of the site P and S wave seismic velocity profile. The results obtained from this tests, allowed the comparing of results and discussing of the advantages and limitations in its use.

The revealing technique for detecting fractured zones in rocky massif is developed. Scheduled positions of fractured zones marked on map and directly on locality, determined with use of biolocation effect, were identical. Results, which were received with use of biolocation methods, have confirmed with devices, geophysical researches and scientific experimental works on cementation detected of fractured zones

One of the techniques used for the construction of underground infrastructure is horizontal directional drilling (HDD). This trenchless method is complicated when crossing gravel deposits as a borehole in coarse gravel tends to collapse, causing the drill pipe to get stuck or the failure of installation of the product pipeline due to exceeding pull forces. In order to find a solution for the problem of borehole instability, the Biogrout process was adapted for borehole stabilization in gravel. In the Biogrout process, loose sand is converted into sandstone by injection of a dedicated mixture in the underground, which stimulates micro-organisms to catalyze chemical reactions leading to the precipitation of calcium carbonate (CaCO₃) crystals. These crystals form ‘bridges’ between the grains, increasing the strength and stiffness of the material. After a first successful test on lab scale in 2008 in which gravel was cemented, a 3 m³ container was treated after which a hole successfully was drilled through it using HDD equipment. Following the success of this container test, two field applications were performed as part of the installation of two 48 inch steel gas pipelines with a length of 600 and 900 meter near Nijmegen NL. During these field applications twice a volume of 1.000 m³ gravel was stabilized in only 7 days each time using the Biogrout technique, after which a HDD was performed successfully.

The paper presents an analysis of effectiveness of the application of seven commonly used CPT-Based classification systems for the assessment of subsoil stratigraphy and lithology. The analysis was conducted with the following classification systems: Begemann 1965, Douglas/Olsen 1981, modified Schmertmann 1985, Robertson et al. 1986, Robertson 1990, Eslami/Fellenius 1997, and, Zhang/Tumay 1999. The analysis was performed for subsoil composed of slightly and strongly overconsolidated moraine tills and glacifluvial sands and gravels. In the investigated area a total of nine piezocone penetration tests, PCPT (or CPTU) tests were conducted and samples were collected for laboratory analyses. The reference point for soil behavior type classification systems was provided by the results of grain size distribution of the soil. The basic element in the analysis was to determine the effect of the type of the applied soil behavior type classification system on the construction of the subsoil stiffness model. Three systems were selected as best performing for the purpose of this analysis: Douglas/Olsen 1981, Robertson et al.1986, and Zhang/Tumay 1999. The construction of subsoil stiffness models was based on the statistical Inverse Distance Weighted method (IDW) by Młynarek, et al., 2007.

The presence of hard concretions and lithified beds in the subsoil can cause serious problems during the realisation of infrastructure projects. As these concretions do most often not occur as continuous layers, they also are a real challenge for geotechnical investigations. This paper gives an overview of geological features and general characteristics of typical hard soil concretions in Flanders. Special attentions is paid to the important interaction between geology and geotechnics. Some typical examples are given of successful and unsuccessful geotechnical investigation programs and their effects on the realisation of infrastructure projects.

The paper presents the results of a research on the influence of structure characteristics on the mechanical behaviour of a saturated compacted scaly clay. To this aim, mechanical properties of compacted scaly clay samples after saturation are compared with the corresponding properties measured on the clay reconstituted in the laboratory. For the stress range explored in the experimental programme, compacted scaly clay samples are stiffer and stronger than reconstituted clay samples owing to their greater density. Collected results are discussed taking in consideration microstructure characteristics of the compacted and reconstituted clay samples.

The dynamic Poisson ratio is a complex calculation parameter mainly considering the standard existing equipment in some Geotechnical laboratories. Nevertheless, this dynamic property can be easily calculated through a simple relationship – based on the theory of elasticity – between the propagation velocities of two distinct elastic waves. Despite permitting an easy calculation of the dynamic Poisson ratio, the signals arrival instant – in regard to the above referred waves – are not always identifiable on the time domain basis of interpretation (Viana da Fonseca et al. [1]). For the analysis of the dynamic Poisson's ratio, three types of elastic waves were taken into consideration. For soil-cement specimens – studied in this paper – were calculated the compression wave velocity V_P, Bar wave velocity V_L and shear wave velocity V_S. Properties like the dynamic confined modulus M_din, dynamic modulus of elasticity E_din and dynamic shear modulus G_din were also intended. The cross comparison between the dynamic Poisson ratios computed by different waves is used to ensure the chosen arrival instances based on time domain interpretation. In this paper it is also preformed a dynamic Poisson ratio recalculation in order to evaluate the parameter sensitivity regarding the equipment resolution concluding in the possibility to estimate fair values of υ_din from the presented tests.

The uniaxial compressive strength (UCS) is one of the main parameter for rock mass characterization and classification, as well as in rock engineering practice. Although UCS testing has been standardized by the International Society for Rock Mechanics other parameters such as results from point load test, which is comparatively cheap and easy to apply, are most widely used. Various studies in the literature propose relationships between I_s50 (from point load test) and UCS, thus objective of this study is to determine conversion factors relating I_s50 and UCS for intact sedimentary rocks, as well as for conglomerates and breccias, since to those rocks, specimen with geometric characteristics for the USC test according to ISRM requirements can not be easily shaped.