Calculation Of Heave Research Articles

Defective vacuum well in a deep excavation, prevention of a serious incident

AbstractIn the course of the new construction of the Wehrhahn Line in Düsseldorf, works included the top‐down building of the station at Schadowstraße with back‐anchored diaphragm walls embedded up to 12 m into the Tertiary fine sand. The formation of the excavation was planned to lie above this in the Quaternary sand gravel. During the construction period, it was noticed that the Tertiary groundwater aquitard in the east part of the excavation is up to 2.5 m higher than forecast. This made necessary the installation of partially inclined suction wells in the Tertiary, in the protection of which the Tertiary groundwater was to be replaced by a surface filter. Altogether 41 suction wells were sunk.Shortly before reaching the excavation bottom level, an increased sand freight and an unplanned higher inside water level were recorded in places. Immediately introduced investigations showed that a defective foot cap had led to the intake of fine sand. In consequence, an erosion channel had formed at the underside of the lance, running through under the diaphragm wall. After a first stabilisation, a remedial concept was worked out collaboratively with all parties. Accordingly the filter section was closed by nitrogen freezing and the action point of the heave was moved downward. An adapted excavation concept was also decided from heave calculations. The extent of the frozen body was checked with an extensive monitoring programme. Through meticulous preparation and the frictionless collaboration of all parties, a major incident could be prevented.

THE RESEARCH OF ADDED RESISTANCE IN WAVES BASED ON NONLINEAR TIME-DOMAIN POTENTIAL FLOW THEORY

In order to accurately predict the motion performance of the ship in waves, the numerical calculation of heave, pitch and added resistance of a container ship in a regular wave is studied based on the three-dimensional fully nonlinear time-domain potential flow theory. The boundary element method is used to deal with the quadrilateral elements, and the governing equations are solved by the first-order flat-plate theory and the fourth-order Runge- Kutta time integration method. The ship hull is divided by the fixed mesh. Considering the non-linear superposition of the forward velocity, the stationary ship wave, diffracted wave, diffraction wave and incident wave field, the free surface is generated by the hybrid Euler-Lagrangian method, and the damping area is set manually at the edge. Take the KCS container ship for instance, the calculation results of heave, pitch and added resistance in waves are compared with the experimental values. The results show that the biggest advantage of this method is to get a more accurate prediction of ship motion in a short time, and this method has a broad application prospect in the analysis and motion prediction of ship hydrodynamic performance in waves.

Prediction of the Vertical Swelling Percentage of Expansive Clays Using a Two-Stage Artificial Neural Networks Methodology

Abstract Artificial Neural Networks (ANN), which are used in many different areas, have been applied to predict the vertical swelling percentage of expansive clays. In contrast to previous models that estimated ANN Models in a single phase, this paper proposes an alternative analysis in based on the following two-stage operation: (a) conducting an ANN analysis on the swelling-pressure test results (i.e., the ASTM 4546 Method C test results) to obtain the swelling-pressure model for any given clay characteristics, and (b) performing an additional ANN analysis on the swelling-percentage test results (i.e., the ASTM 4546 Method B test results), including the former ones, with the given independent variables of the clay characteristics. This second stage includes a defined expression containing the given surcharge pressure and the predicted value of the swelling pressure as obtained from the model of the previous stage. Two final ANN Models, each with a different arrangement of the given independent variables, were derived from this two-stage procedure. Their statistical fit was clearly found to be superior in comparison to previous models estimated with the same data set. Furthermore, one of these two models exhibited the expected geophysical behavior. As this new ANN Model yields higher predicted swelling-percentage values, it can definitely be regarded as a preferable one in the sense of enlarging the safety margin in heave calculations.

Using the Artificial Neural Networks Methodology to Predict the Vertical Swelling Percentage of Expansive Clays

AbstractRegular use of artificial neural networks (ANN) analysis for predicting the vertical swelling percentage of expansive clays may lead to inappropriate results in terms of their geophysical behavior. This paper presents two new ANN Models derived from a two-stage procedure. The models were estimated using the same data set from the previous paper, and their statistical fit was clearly found to be superior in comparison to the previous models. Furthermore, one of these two models exhibited the expected geophysical behavior. As this new ANN Model yields higher predicted swelling-percentage values, it can definitely be regarded as a preferable one in the sense of enlarging the safety margin in heave calculations.

Comprehensive Methodology for the Evaluation of Clay Expansiveness. A Case Study

Although expansive soils have been widely studied by different authors, just a few have made methodological proposals to comprehensively evaluate this phenomenon. The aim of this paper is to suggest a methodology which will serve as guideline to evaluate soil expansiveness in a comprehensive way. This methodology comprises a series of tasks: identification and classification of potentially expansive soils, estimation of the active zone depth, quantification of the expansion, calculation of heave and choice of a solution.