Probabilistic Approach to the Assessment of the Depth of Soil Freezing

The paper deals with the probabilistic method of the assessment of the depth of soil freezing. Annual (winter) maxima of the position of the zero centigrade temperature measured in the soil were approximated by Gumbel probability distribution. Its parameters were estimated using maximum likelihood method. Results received on the base of data from 2 meteorological stations and 30 years of observations, called as characteristic values of 50-year return period, refelect the influence of the climatic conditions on the freezing depth. On the other hand the soil structure and its conditions also play an important role in freezing. Nowadays they may be taken into account using correction coefficients. It is concluded that this methods is more precise than a method using so called air freezing index. Received results are not the same as given in the old Polish Standard. New analysis is currently being done.

The Boring Sounding of Alluvial Soils

In article the description and results of in situ test of soils is resulted by of Russian drilling test (RDT). It involves several drilling parameters: torque, axial force, rotation speed, linear velocity, tip resistance for identifying soil strata of different strengths and for determining dependences between drilling parameters and soil deformation properties.

Usage of Wood Fly Ash in Stabilization of Unbound Pavement Layers and Soils

Modification and stabilization of road structure unbound layers has extensively been studied both at laboratory and field for decades. The most commonly used binders for soil modification and stabilization are cement and quicklime (CaO), but alternative pozzolans and their mixtures are of economical, technical and environmental interest. This study presents soil stabilization with wood fly ash (WFA) at laboratory. Natural sand (Sa), Sa mixtures with 10% and 20% WFA were compacted at optimal water content according to Standard Proctor test LVS EN 13286-2:2012, and California bearing ratio (CBR) tested according to LVS EN 13286-47:2012 for cured samples after 96 hours immersed in water with 2 kg surcharge and after 7 days sealed simultaneously. At the same time also Immediate bearing index was determined for natural soil and their mixture with 10% WFA. Results showed 3.79 times enhancement in CBR values Sa after 7 days curing, justifying that WFA is valuable material for hydraulically bound mixtures.

Evaluation of Sand-Shell Mixture Behaviour for Breakwater Foundation

The available sand material for a breakwater foundation is mixed with shells. The shell percentage of the sand material is variable and percentages up to even 50% are observed. It is essential to evaluate the properties and the behaviour of the sand-shell mixture as this will form the improved breakwater foundation. In reality the backfilled sand of the breakwater foundation has different relative densities in different depths. In this study the mechanical properties of the sand-shell mixture for different relative densities are evaluated. For different relative densities of sand-shell mixture the direct shear tests and the consolidated undrained triaxial tests are carried out on some samples. The results of the experiments showed that the samples with higher relative density show a higher internal friction angle. However, for the samples with even low relative density, an internal friction angle of less than 32° is not observed. The volume variation of the samples with different relative densities are monitored. Samples with low relative density showed a contraction behaviour; resulting in an increase of the pore water pressure, a reduction of the effective strength and finally the samples become susceptible to liquefaction. While the samples with high relative density showed a dilatancy behaviour.

Experimental Investigation into Internal Erosion Potential for Granular Filters

Internal erosion is a phenomenon whereby the filtrates under the influence of significant seepage forces accompany the finer fraction from potential internally unstable filters (e.g. broadly- and gap-graded soil), occasionally rendering them ineffective. The filter assessment for internal erosion or instability potential is emphasized through particle size distribution based geometrical criteria ignoring the effect of compaction. In this study, the results of hydraulic gradient controlled internal erosion tests conducted over a wide range of compacted sand-gravel mixtures were used to analyse some of the available geometrical criteria, which interestingly showed partial success in assessing the filter’s internal erosion potential. It was revealed that the occurrence of internal erosion is a combined function of particle size distribution and the relative density of soils that had been ignored in many of the existing criteria. A comparison between the assessments obtained from some of the particle size based criteria and that from a constriction size based technique was reported for a large body of published data. It was observed that the latter criterion, which incorporates the effects of both particle size distribution and relative density of soils in tandem, could assess the reported test results with higher accuracy.

A Framework for Versatile Shape of Yield Surfaces for Structured Aniso-tropic Soft Soils

A framework based on logarithmic contractancy is proposed to produce versatile shapes of yield surfaces for structured anisotropic clays. The recently proposed constitutive model (E-SCLAY1S) is an extension of existing model called S-CLAY1S, which is a Cam Clay type model that accounts for anisotropy and structure. A new parameter called contractancy parameter is introduced to control the shape of the yield surface as well as the plastic potential (as an associated flow rule is applied). This new parameter can be used to fit the coefficient of earth pressure at rest, the undrained shear strength or the stiffness under shearing stress paths predicted by the model. The model predicts the uniqueness of the critical state line and its slope is independent of the contractancy parameter. The effect of the shape of the yield surface was investigated on computed results of a benchmark embankment constructed on Bothkennar (Scotland) clay by employing the E-SCLAY1S model as a user-defined soil model into the PLAXIS finite element code. The results demonstrate that the contribution of the shape of yield surface (logarithmic contractancy parameter) have a relatively large effect on lateral movement of subsoil beneath the toe of the embankment compared to the settlement of subsoil at the centre of the embankment.

Numerical Modelling of Inclined Piles in Settling Soil

The allowable load for slender end-bearing piles in soft soils driven or drilled to compact till or rock frequently depends on the structural capacity of the pile. Pile groups consisting of such slender preceast concrete or steel piles often include inclined piles, since such small-diameter piles have a limited horizontal bearing capacity. Inclined piles placed in settling soil are subjected to a lateral force, which reduces the pile structural capacity. The simplified beam-spring design methods normally used to predict the impact on the structural capacity of inclined piles in settling soil are currently very crude because of the simplified description of the real pile and soil. On the other hand, the possibility to accurately calculate settlements in soft soil is highly developed, and it is possible to include creep effects in routine settlement calculations. There is currently no direct link between the advanced settlement analysis and the crude beam-spring idealization of inclined piles in settling soil. A full numerical model containing both the pile soilstructure interaction and the settlement process is very time-consuming to run and associated with mesh convergence and contact formulation problems. Herein a suitable modelling idealization of the settling soil is discussed, in which a settlement distribution from an advanced FEM-analysis is adapted to a simplified FEM or beam spring analysis suitable for practical design. The calculation method is compared to field measurements, and is shown to compare well with the field case. A strategy to adapt the settlement profile to model calculation of inclined piles is discussed.

Correlations of Regional Geotechnical Parameters on the Basis of CPTU and DMT Tests

The requirements for field research for Polish conditions demand proper dependences. Dependences based on more than 30 localizations for different genetic types of soils were derived for the area of Poland. Direct results from CPT, DMT and profiles from boreholes have been collected at the test sites for individual localization. For interpretation of results, dependences and diagrams of CPTU versus DMT were created. Correlations on the background of results from literature for different types of soils for numerous research areas were collected, with established dependences for Polish grounds conditions. Additionally some recommendations for the interpretation of the results from CPTU and DMT tests for analysed soils have been proposed.

German Proposals for the Revision of Eurocode 7 “Geotechnical design”

After implementing the Eurocodes, concerns were raised that the set of rules and regulations is not suitable for the designer’s day-to-day use. The first generation of Eurocodes consists of 58 codes with more than 5,200 pages. Moreover, practitioners have to cope with national supplementary codes. As a result, an “Initiative on Improving the Practicability of Technical Rules for Building Constructions” (PRB) was established by the German construction industry and associations of structural engineers in 2011. As part of the initiative, a Project Group for Geotechnical Design was established alongside groups for the other Eurocodes, with the aim of streamlining Eurocode 7 and reducing the number of design approaches and partial safety factors. The paper will analyse the shortcomings of the two parts of Eurocode 7 and present a concept for a more concise and user-friendly code. Furthermore, comparative calculations have been performed for standard geotechnical design applications to investigate the potential for European harmonization in geotechnical design. The results are described and it is shown how they can be incorporated in the revision of EC 7. Moreover, a new formula for verifying geotechnical ultimate limit states is presented which formally covers all design approaches and also enables other parameters such as consequence classes, human error etc. to be incorporated by applying different multiplicative partial safety factors.

Simulation of the Plug inside Open Steel Pipe Piles with Regards to Different Installation Methods

Open steel pipe piles are used for various applications in costal engineering and port structures and they are becoming increasingly more important for offshore structures. A plug formed during the installation of open steel pipe piles has an influence on the installation process of the steel pipe pile as well as on the final bearing behaviour and the pile resistance. Forming of the plug depends on different influences, e.g. the pile diameter, the soil conditions and the installation method. To obtain a better understanding of the formation of the plug and its consequences several experimental small-scale tests, experimental field tests and numerical simulations have been performed. But so far this phenomenon is not completely investigated yet. At the beginning of this paper a structured overview about the characterization of the plug as well as soil mechanical processes during the pile installation in non-cohesive soil are provided. Then, the results of a centrifuge study are shown. The focus of this paper is the numerical simulation of the installation process of impact and vibratory driven piles in non-cohesive soil to investigate the effect of plugging with regard to different installation methods. Centrifuge experimental results are utilized to validate the numerical model, which can provide detailed insights into the physical processes occurring in the soil but are difficult to measure in experiments. The numerical analyses hence illustrate zones of densification/loosening, which highlight the differences resulting from the installation methods.