The FEBEX (Full-scale Engineered Barriers Experiment in Crystalline Host Rock) ''in situ'' test was installed at the Grimsel Test Site underground laboratory (Switzerland) and is a near-to-real scale simulation of the Spanish reference concept of deep geological storage in crystalline host rock. A modelling exercise, aimed at predicting field behaviour, was divided in three parts. In Part A, predictions for both the total water inflow to the tunnel as well as the water pressure changes induced by the boring of the tunnel were required. In Part B, predictions for local field variables, such as temperature, relative humidity, stresses and displacements at selected points in the bentonite barrier, and global variables, such as the total input power to the heaters were required. In Part C, predictions for temperature, stresses, water pressures and displacements in selected points of the host rock were required. Ten Modelling Teams from Europe, North America and Japan were involved in the analysis of the test. Differences among approaches may be found in the constitutive models used, in the simplifications made to the balance equations and in the geometric symmetries considered. Several aspects are addressed in the paper: the basic THM physical phenomena which dominate the test response are ARTICLE IN PRESS www.elsevier.com/locate/ijrmms 1365-1609/$ -see front matter r
The HG-A in situ test, located at the Mont Terri Underground Rock Laboratory (URL), was analysed as part of the FORGE project. This test investigated the behaviour of the excavation damage zone (EDZ) around a backfilled microtunnel by a series of water- and gas-injection tests. Prior to testing, the backfilled microtunnel was sealed with a hydraulic megapacker system. A key aspect was the investigation of crack opening and closure along the EDZ in response to water and gas injections in the context of radioactive waste disposal. In the model, the intrinsic permeability of the EDZ was assumed to depend on deformation, and additional simplifying assumptions were considered: axisymmetry about the tunnel axis; no gravity; soil slices orthogonal to the tunnel axis move independently and in plane strain; liquid and gas flows along the EDZ parallel to the tunnel axis; and undrained saturated conditions for the Opalinus Clay. As a result, the field equations were reduced to differential equations for liquid and gas pressures defined in a one-dimensional (1D) domain representing the EDZ. The main trends of the pressure evolution observed in the test section were reproduced. A 2D axisymmetric model confirmed the validity of the simplifying assumptions, except for small zones of the EDZ near the megapacker ends.
On 12 October 2013, the 24-storey high ‘Space’ building collapsed in Medellín, Colombia. The building had a reinforced concrete structure founded on large-diameter piles with enlarged bases. During and after construction the building exhibited structural problems and excessive settlements of some piles. Because of the evidence of structural damage, the building was evacuated on 11 October 2013, 1 day before the collapse. Isolated large-diameter piles excavated in a firm, high-plasticity saprolitic residual clay, supported building columns. Building collapse was triggered by a significant increase of the vertical load transmitted by some columns, which, in turn, is explained by widely different settlements experienced by neighbouring piles and the resulting loading transfer mechanisms. The first part of the paper presents the results of the field exploration and laboratory tests, as well as the structural and architectural layout, including the construction process and other forensic aspects that could influence the collapse of the structure. Afterwards, the joint structure–foundation–soil numerical model developed and its predictions are described. Matching the records of pile settlements, measured during construction and afterwards until building collapse, with model predictions allowed the validation of the model. The causes that triggered the collapse were identified and some other lessons were learned.
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