Dynamics of structures

Some forty years ago, when geotechnical centrifuge modelling had been rediscovered and was being developed once more after the early work of Phillips (1869), only a few studies were devoted to the questions and concerns about scaling laws and similitude conditions. During the first decades, it was relatively easy for researchers to keep themselves informed about the main outcomes of these studies and to take them into account when designing new centrifuge model tests. This is obviously not true today following the welcome growth in terms of the large number of centrifuge facilities now in operation around the world. It is increasingly difficult, but yet absolutely essential, to know about the relevant developments concerning studies into the scaling laws and, furthermore, into the limits of the domains of the use of centrifuge modelling. On the other hand, new media offers a significant opportunity to provide this resource to the physical modelling community. New topics are investigated by many researcher...

Catalogue of scaling laws and similitude questions in geotechnical centrifuge modelling

In this paper, a new multi-criteria problem solving method—the Full Consistency Method (FUCOM)—is proposed. The model implies the definition of two groups of constraints that need to satisfy the optimal values of weight coefficients. The first group of constraints is the condition that the relations of the weight coefficients of criteria should be equal to the comparative priorities of the criteria. The second group of constraints is defined on the basis of the conditions of mathematical transitivity. After defining the constraints and solving the model, in addition to optimal weight values, a deviation from full consistency (DFC) is obtained. The degree of DFC is the deviation value of the obtained weight coefficients from the estimated comparative priorities of the criteria. In addition, DFC is also the reliability confirmation of the obtained weights of criteria. In order to illustrate the proposed model and evaluate its performance, FUCOM was tested on several numerical examples from the literature. The model validation was performed by comparing it with the other subjective models (the Best Worst Method (BWM) and Analytic Hierarchy Process (AHP)), based on the pairwise comparisons of the criteria and the validation of the results by using DFC. The results show that FUCOM provides better results than the BWM and AHP methods, when the relation between consistency and the required number of the comparisons of the criteria are taken into consideration. The main advantages of FUCOM in relation to the existing multi-criteria decision-making (MCDM) methods are as follows: (1) a significantly smaller number of pairwise comparisons (only n − 1), (2) a consistent pairwise comparison of criteria, and (3) the calculation of the reliable values of criteria weight coefficients, which contribute to rational judgment.

https://www.mdpi.com/2073-8994/10/9/393/pdf

A New Model for Determining Weight Coefficients of Criteria in MCDM Models: Full Consistency Method (FUCOM)

【臨床医学の展望 2012】 呼吸器病学

The Encyclopaedia of Islam

When performing centrifuge tests, it is necessary to carry out in-flight tests such as the cone penetration test (CPT). Recently, miniature CPTs have formed one collaboration entitled 'European Pro ...

/pdf/centrifuge-cone-penetration-tests-in-sand-140nx2889z.pdf

Centrifuge cone penetration tests in sand

An investigation of the behaviour and energy budget of sturzstroms has been carried out using physical, analytical and numerical modelling techniques. Sturzstroms are rock slides of very large volume and extreme run out, which display intensive fragmentation of blocks of rock due to inter-particle collisions within a collisional flow. Results from centrifugal model experiments provide strong arguments to allow the micro-mechanics and energy budget of sturzstroms to be described quantitatively by a fractal comminution model. A numerical experiment using a distinct element method (DEM) indicates rock mass and boundary conditions, which allow an alternating fragmenting and dilating dispersive regime to evolve and to sustain for long enough to replicate the spreading and run out of sturzstroms without needing to resort to peculiar mechanism. The fragmenting spreading model supported here is able to explain the run out of a fluid-absent granular flow beyond the travel distance predicted by a Coulomb frictional sliding model. This, and its strong relation to internal fragmentation, suggests that a sturzstrom constitutes a landslide category of its own. This study provides a novel framework for the understanding the physics of such sturzstroms.

/pdf/fractal-fragmentation-of-rocks-within-sturzstroms-insight-jquoguqjjq.pdf

Fractal fragmentation of rocks within sturzstroms: insight derived from physical experiments within the ETH geotechnical drum centrifuge

Stone columns are primarily used for the purpose of ground improvement in fine grained soils in order to reduce settlements and the risk of bearing failure. They are also designed to improve the drainage conditions in the ground and to accelerate the consolidation processes within the clay. However, smear and disturbing effects caused during the construction of stone columns result in degradation of consolidation performance in comparison with the theoretically ideal conditions. Model stone columns are constructed in-flight under 50 times gravity in centrifuge tests and the soil micro-structure in the vicinity of these columns is investigated by applying different methods, including environmental scanning electron microscopy and mercury intrusion porosimetry. The results of these tests confirm that smear and disturbance occur owing to stone column installation and the region influenced can be divided into three sections: a penetration zone (1) where the sand particles are squeezed through the clay; a smea...

Smear zone identification and soil properties around stone columns constructed in-flight in centrifuge model tests

Most of the third world countries having rivers passing through them suffer from the water contaminant problem. This problem is considered so difficult to get the water quality within the standard allowable limits for drinking, as well as for industrial and agricultural purposes. This research aims to assess the water quality of the Tigris River using the water quality index method and GIS software. Twelve parameters (Ca, Mg, Na, K, Cl, SO4, HCO3, TH, TDS, BOD5, NO3, and EC) were taken from 14 stations along the river. The weighted arithmetic method was applied to compute the water quality index (WQI). The interpolation method (IDW) was applied in ArcGIS 10.5 to produce the prediction maps for 12 parameters at 11 stations along the Tigris River during the wet and dry seasons in 2016. The regression prediction was applied on three stations in the Tigris River between observed values and predicted values, from the prediction maps, in both seasons. The results showed that the regression prediction for all parameters was given the acceptable values of the determination coefficient (R2). Furthermore, the state of water quality for the Tigris River was degraded downstream of the Tigris River, especially at the station (8) in Aziziyah in the wet and dry seasons and increase degradation clearly at Qurnah (Basrah province) in the south of Iraq. This paper considers the whole length of the Tigris River for the study. This is important to give comprehensive knowledge about the contamination reality of the river. Such that it becomes easier to understand the problem of contamination, analyze it, and then find the suitable treatments and solutions.

/pdf/water-quality-assessment-along-tigris-river-iraq-using-water-zj6ylun3zi.pdf

Jan Laue

Papers

Centrifuge cone penetration tests in sand

Fractal fragmentation of rocks within sturzstroms: insight derived from physical experiments within the ETH geotechnical drum centrifuge

Smear zone identification and soil properties around stone columns constructed in-flight in centrifuge model tests

Water quality assessment along Tigris River (Iraq) using water quality index (WQI) and GIS software

Guidelines for cone penetration tests in sand