The FEBEX benchmark test: case definition and comparison of modelling approaches

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 discussed, a comparison of different modelling results with actual measurements is presented and a discussion is given to explain the performance of the various predictions.Peer Reviewe

Wheat intake, mill performance, quality control Flour milling industry correspondence course

Module II in workbook seriesAvailable from British Library Document Supply Centre- DSC:q93/11252(Wheat) / BLDSC - British Library Document Supply CentreSIGLE2. edGBUnited Kingdo

Unexpected behaviour of a large excavation in saturated sands

The paper describes the behaviour of the perimeter wall of a very large excavation in saturated sands. The excavation was extended to a depth of 20m (17m below the water table) and the walls reached an impervious silty clay formation which appears 55 m below the surface. The reinforced concrete walls were stabilized by a single row of anchors grouted in sand, below the water table. Stabilizing berms were also left unexcavated against the walls to allow reaching the maximum excavation depth in the large central area of the site. Later, basement slabs were built and propped against the walls, before the excavation was completed. A disturbing finding was the large horizontal displacements measured in the walls during the early excavation stages. These large displacements extended to large depths, well beyond the excavation depth. However, anchor loads remained essentially constant throughout the excavation and water lowering operations. Computer results were found in reasonable agreement with available wall displacements and anchor loads. A most interesting part of the analysis was the distribution of movements in the active zone of the walls. It was found that significant displacements extended well beyond the expected distance from the wall. In fact, wall displacements and anchor fixed length displacements were similar in magnitude. This result could be interpreted as an indication of impending failure but further finite element analysis carried out to establish the safety factor against failure showed that the entire system was far from limiting conditions. This effect is related to some features of the project, which include the anchor length, the stiffness of the wall and the size of the excavated area.Postprint (published version

Development of a direct methanol fuel cell system

SIGLEAvailable from British Library Document Supply Centre-DSC:DXN038017 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

The collapse of Space building

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.Peer ReviewedPostprint (author's final draft

The collapse of Space building

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.Peer Reviewe

The FEBEX benchmark test: case definition and comparison of modelling approaches

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 discussed, a comparison of different modelling results with actual measurements is presented and a discussion is given to explain the performance of the various predictions.Peer Reviewe