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The railway network on coastal areas of Finland is predominantly located in soft clay areas. The undrained shear strength of such clays is generally low, highly anisotropic, and rate dependent, and it exhibits post-peak strain softening under undrained conditions. A full-scale failure test was performed by Tampere University of Technology in Perniö, Western Finland, in 2009. A shallow railway embankment built on a soft clay deposit was equipped with a loading structure and loaded to failure in about 30 h. The embankment collapsed 2 h after the last loading step. In this study, data collected from the experiment are used, together with laboratory test results on high-quality samples, to conduct advanced finite element analysis of the Perniö failure test. The NGI-ADPSoft model is used for this purpose, which is capable of simulating the strain-softening behavior of the clay. Even though the observed rate effect is not taken into account in the analyses, the failure load can be predicted reasonably well. Good agreement is also observed for calculated displacements and failure mechanism with experimental observations.

The study focuses on the derivation of transformation models for undrained shear strength (su) of Finnish soft sensitive clays. Specific correlation equations for suof Finnish clays are presented in this work for the first time. Field and laboratory measurements from 24 test sites in Finland are exploited for this purpose and a multivariate database is constructed. The multivariate data consist of sufrom the field vane test, preconsolidation stress, vertical effective stress, liquid limit, plastic limit, natural water content, and sensitivity. The main objective is to evaluate the interdependence of su, consolidation stresses, and index parameters and provide a consistent framework for practical use. The new correlations are established through regression analyses. The constructed framework is further validated by another independent multivariate database of clays from Sweden and Norway as well as by empirical equations for Swedish and Norwegian clays. Existing correlations are evaluated for Finnish and Scandinavian clays. Finally, bias and uncertainties of the new correlations are presented.

This paper investigates the feasibility of Least square support vector machine (LSSVM) model to cope the problem of implicit performance function during first order second moment (FOSM) method based slope reliability analysis. LSSVM is firmly based on the theory of statistical learning. In LSSVM, Vapnik’s e -insensitive loss function has been replaced by a cost function which corresponds to a form of ridge regression. Here, LSSVM has been used as a regression technique to approximate implicit performance functions. A slope example has been presented for illustrating the applicability of LSSVM based FOSM method. The developed LSSVM based FOSM has been compared with the artificial neural network (ANN) and least square method. The result shows that the approximation of LSSVM can be used in the FOSM method for slope reliability analysis.

This paper examines the potential of relevance vector machine (RVM) for slope reliability by using first order second moment method (FOSM). The FOSM demands the values and partial derivatives of the performance function with respect to the design random variables. Such calculations could be time-consuming or cumbersome when the performance functions are implicit. The analysis of slope by limit equilibrium method gives implicit performance functions. Here, RVM has been used to predict implicit performance functions. RVM rely on the Bayesian concept and utilize an inductive modelling procedure that allows incorporation of prior knowledge in the estimation process. In this paper, an example is given regarding how the proposed RVM-based FOSM analysis can be carried out. This study shows that the proposed RVM-based FOSM is viable alternative for slope reliability analysis.

An improved harmony search algorithm is proposed which is found to be more efficient than the original harmony search algorithm for slope stability analysis. The effectiveness of the proposed algorithm is examined by considering several published cases. The improved harmony search method is applied to slope stability problems with five types of procedure for generating trial slip surfaces. It is demonstrated that the improved harmony search algorithm is efficient and effective for the minimization of factors of safety for various difficult problems, and the method of generating the trial failure surfaces can be important in the minimization process.

“Failure to converge” during slope stability analysis for complicated slopes with external surcharge or soil nails using the “rigorous” methods are experienced by many engineers. The two main reasons for failure to converge are: (1) the fulfillment of the assumptions for a specific method of analysis; (2) the limitation of the numerical method in evaluating the factor of safety. It will be demonstrated that there are problems where convergence for the “rigorous” methods is not achieved by the conventional iteration analysis, but physically acceptable results may exist for some of these “non-converged” problems, if the failure to converge is due to the second reason as given above. With reference to some of the designs by the engineers in Hong Kong, the authors will also demonstrated that the minimum factors of safety obtained by the current design practice may be over-estimated due to the convergence problem in the stability analysis.

In this paper, the factors of safety and the locations of critical failure surfaces obtained by the limit equilibrium method and strength reduction method are compared for various slopes. For simple homogenous soil slopes, it is found that the results from these two methods are generally in good agreement except when ϕ′ is zero. It is also found that the strength reduction method (SRM) is usually not sensitive to the dilation angle, soil moduli or the solution domain size and the choice of these parameters is not critical in the analysis. While the SRM may perform well in many cases, two major limitations of this method are found in this study: it is sensitive to the nonlinear solution algorithm for the case of a soft band with frictional material and it is incapable of determining other failure surfaces which may be only slightly less critical than the SRM solution but still require treatment for good engineering practice.

A full-scale embankment failure experiment was conducted in 2009 in Perniö, Finland. A small, extensively instrumented railway embankment on a soft clay foundation was brought to failure by loading over a period of 30 h. Instrumentation consisted of over 300 different measurement points, including 37 piezometers and nine automatically monitored inclinometer tubes. The relatively rapid loading simulated a heavy train coming to a standstill on the embankment. The primary purpose of the experiment was to gather field data of a failure caused by a rapidly applied load, with an emphasis on the pore pressure response in the clay foundation layer. The test was also used to assess the suitability of various instruments for real-time stability monitoring. The embankment failure was an asymmetric bearing capacity mechanism that is hypothesised to have been triggered by an undrained creep rupture.During the last 2 h of the experiment, pore pressure and displacements increased at an accelerating rate while the external load was kept constant. The time-dependency of the pore pressure and displacement responses was a key factor in the experiment. With regards to monitoring of similar in-service train embankments, proper placement of instruments according to predicted failure mechanisms was found to be important. publishedVersion