Study on low‐strain integrity testing of pipe‐pile using the elastodynamic finite integration technique

This study focuses on the three‐dimensional (3‐D) characteristics of wave propagation in pipe‐pile using elastodynamic finite integration technique. First, a real 3‐D pile‐soil model in cylindrical coordinate system is presented. Then, the governing equations are established. With the boundary and initial conditions, the numerical solution is obtained. The accuracy and feasibility of the self‐written code are further verified via comparing with the measured data. Velocity histories at different angles of pile top and pile tip are illustrated, and the snapshots reflecting the 3‐D characteristics of wave propagation are given. It shows that the interferences of Rayleigh waves can confuse the result interpretation for pile integrity testing. The increase of hammer contact time can effectively mitigate the interferences, and the interferences of Rayleigh waves are weakest at an angle of 90° from where hammer hits. Besides, surrounding soil can partly mitigate the wave interferences. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis of flood propagation changes in the Kienstock—Bratislava reach of the Danube River/Analyse des changements de propagation des crues dans le tronçon Kienstock—Bratislava du Fleuve Danube

Abstract

In the first part of this study, a flood wave transformation analysis for the largest historical floods in the Danube River reach Kienstock–Bratislava was carried out. For the simulation of the historical (1899 and 1954) flood propagation, the nonlinear river model NLN-Danube (calibrated on the recent river reach conditions) was used. It was shown that the simulated peak discharges were not changed significantly when compared to their historical counterparts. However, the simulated hydrographs exhibit a significant acceleration of the flood wave movement at discharges of between 5000 and 9000 m³ s^-1. In the second part, the travel time-water level relationships between Kienstock and Bratislava were analysed on a dataset of the flood peak water levels for the period 1991–2002. An empirical regression routing scheme for the Danube short-term water level forecast at Bratislava station was derived. This is based on the measured water level at Kienstock gauging station.     

Effective block diagonal preconditioners for Biot's consolidation equations in piled‐raft foundations

The finite element (FE) simulation of large‐scale soil–structure interaction problems (e.g. piled‐raft, tunnelling, and excavation) typically involves structural and geomaterials with significant differences in stiffness and permeability. The symmetric quasi‐minimal residual solver coupled with recently developed generalized Jacobi, modified symmetric successive over‐relaxation (MSSOR), or standard incomplete LU factorization (ILU) preconditioners can be ineffective for this class of problems. Inexact block diagonal preconditioners that are inexpensive approximations of the theoretical form are systematically evaluated for mitigating the coupled adverse effects because of such heterogeneous material properties (stiffness and permeability) and because of the percentage of the structural component in the system in piled‐raft foundations. Such mitigation led the proposed preconditioners to offer a significant saving in runtime (up to more than 10 times faster) in comparison with generalized Jacobi, modified symmetric successive over‐relaxation, and ILU preconditioners in simulating piled‐raft foundations. Copyright © 2012 John Wiley & Sons, Ltd.     

Copper‐gold mineralisation in New Guinea: Numerical modelling of collision,fluid flow and intrusion‐related hydrothermal systems

Two‐ and three‐dimensional numerical modelling techniques, constrained by key geodynamic data, provide insights into the controls on development of porphyry‐related Cu–Au mineralisation in the Tertiary collision zone of New Guinea. Modelling shows that the creation of local dilation to facilitate magma emplacement can be caused by reactivation of arc‐normal transfer faults, where they cut the weakened fold belt. Additionally, dilation occurs where fluid overpressuring is caused by collision‐related, south‐directed fluid flow being localised into the more permeable units of the Mesozoic passive‐margin sedimentary succession. Rapid uplift and erosion, which may be a mechanism for magmatic fluid release in these systems, is shown to be greatest in the west of West Papua, where the stronger Australian crust acts as a buttress. Within the Papuan Fold Belt, uplift is greatest near the margins, where the weaker fold belt abuts the stronger crust and/or major faults have been reactivated. Increased orographically induced precipitation and erosion exposes the lower parts of the stratigraphy within or on the margins of these uplifted zones. On a smaller scale, 2–D coupled fluid‐flow ‐ thermal‐chemical modelling uses a scenario of fluid mixing to calculate metal precipitation distribution and magnitude around an individual intrusive complex. Modelling highlights the interdependence of the spatial permeability structure, the regional temperature gradient, and the geometry of the convection cells and how this impacts on the distribution of metal precipitation.     

A mass‐balance approach to estimate in‐stream processes in a large river

A mass‐balance approach was used to estimate in‐stream processes related to inorganic nitrogen species (NH₄⁺, NO₂^? and NO₃^?) in a large river characterized by highly variable hydrological conditions, the Garonne River (south‐west France). Studies were conducted in two consecutive reaches of 30 km located downstream of the Toulouse agglomeration (population 760 000, seventh order), impacted by modification of discharge regime and high nitrogen concentrations. The mass‐balance was calculated by two methods: the first is based on a variable residence time (VRT) simulated by a one‐dimensional (1‐D) hydraulic model; the second is a based on a calculation using constant residence time (CRT) evaluated according to hydrographic peaks. In the context of the study, removal of dissolved inorganic nitrogen (DIN) for a reach of 30 km is underestimated by 11% with the CRT method. In sub‐reaches, the discrepancy between the two methods led to a 50% overestimation of DIN removal in the upper reach (13 km) and a 43% underestimation in the lower reach (17 km) using the CRT method. The study highlights the importance of residence time determination when using modelling approaches in the assessment of whole stream processes in short‐duration mass‐balance for a large river under variable hydrological conditions. Copyright © 2007 John Wiley & Sons, Ltd.     

The effect of terrace geology on ground‐water movement and on the interaction of ground water and surface water on a mountainside near Mirror Lake,New Hampshire,USA

The west watershed of Mirror Lake in the White Mountains of New Hampshire contains several terraces that are at different altitudes and have different geologic compositions. The lowest terrace (FSE) has 5 m of sand overlying 9 m of till. The two next successively higher terraces (FS2 and FS1) consist entirely of sand and have maximum thicknesses of about 7 m. A fourth, and highest, terrace (FS3) lies in the north‐west watershed directly adjacent to the west watershed. This highest terrace has 2 m of sand overlying 8 m of till. All terraces overlie fractured crystalline bedrock. Numerical models of hypothetical settings simulating ground‐water flow in a mountainside indicated that the presence of a terrace can cause local ground‐water flow cells to develop, and that the flow patterns differ based on the geologic composition of the terrace. For example, more ground water moves from the bedrock to the glacial deposits beneath terraces consisting completely of sand than beneath terraces that have sand underlain by till. Field data from Mirror Lake watersheds corroborate the numerical experiments. The geology of the terraces also affects how the stream draining the west watershed interacts with ground water. The stream turns part way down the mountainside and passes between the two sand terraces, essentially transecting the movement of ground water down the valley side. Transects of water‐table wells were installed across the stream's riparian zone above, between, and below the sand terraces. Head data from these wells indicated that the stream gains ground water on both sides above and below the sand terraces. However, where it flows between the sand terraces the stream gains ground water on its uphill side and loses water on its downhill side. Biogeochemical processes in the riparian zone of the flow‐through reach have resulted in anoxic ground water beneath the lower sand terrace. Results of this study indicate that it is useful to understand patterns of ground‐water flow in order to fully understand the flow and chemical characteristics of both ground water and surface water in mountainous terrain. Copyright © 2007 John Wiley & Sons, Ltd.     

Mathematical and numerical filtration–advection–dispersion model of miscible grout propagation in saturated porous media

The development of a predictive model of behaviour of porous media during injection of miscible grout, taking into account convection, dilution and filtration of grout solution with interstitial water, as well as consolidation aspects, is presented. Model assumptions are reviewed and discussed first. During the establishment of the model, we insist on surface terms and their physical relevance in expressing adsorption effects. Constitutive laws such as Fick's law for diffusive mass transport, hydrodynamic dispersion tensor dealing with miscibility, are modified by taking into account filtration effects. A new surface term appears in mass balance equations as a consequence of filtration. According to the filtration laws used, an initial filtration rate is estimated on the basis of a one‐dimensional experimental campaign. The field equations are discretized by using Galerkin finite element and θ‐scheme standard method. For transport equation, Streamline Upwind Petrov Galerkin method is employed to prevent numerical oscillations. Lastly, confrontation of numerical results with laboratory experiments constitutes a first step to validate the model on a realistic basis. Copyright © 2001 John Wiley & Sons, Ltd.     

Moraine development at a small High‐Arctic valley glacier: Rieperbreen,Svalbard

Ice‐cored lateral and frontal moraine complexes, formed at the margin of the small, land‐based Rieperbreen glacier, central Svalbard, have been investigated through field observations and interpretations of aerial photographs (1936, 1961 and 1990). The main focus has been on the stratigraphical and dynamic development of these moraines as well as the disintegration processes. The glacier has been wasting down since the ‘Little Ice Age’ (LIA) maximum, and between 1936 and 1990 the glacier surface was lowered by 50–60 m and the front retreated by approximately 900 m. As the glacier wasted, three moraine ridges developed at the front, mainly as melting out of sediments from debris‐rich foliation and debris‐bands formed when the glacier was polythermal, probably during the LIA maximum. The disintegration of the moraines is dominated by wastage of buried ice, sediment gravity‐flows, meltwater activity and some frost weathering. A transverse glacier profile with a northward sloping surface has developed owing to the higher insolation along the south‐facing ice margin. This asymmetric geometry also strongly affects the supraglacial drainage pattern. Lateral moraines have formed along both sides of the glacier, although the insolation aspect of the glacier has resulted in the development of a moraine 60 m high along its northern margin. Copyright © 2001 John Wiley & Sons, Ltd.     

Late Glacial fluvial response of the Niers‐Rhine (western Germany) to climate and vegetation change

The Niers valley was part of the Rhine system that came into existence during the maximum Saalian glaciation and was abandoned at the end of the Weichselian. The aim of the study was to explain the Late Pleniglacial and Late Glacial fluvial dynamics and to explore the external forcing factors: climate change, tectonics and sea level. The sedimentary units have been investigated by large‐scale coring transects and detailed cross‐sections over abandoned channels. The temporal fluvial development has been reconstructed by means of geomorphological relationships, pollen analysis and ¹⁴C dating. The Niers‐Rhine experienced a channel pattern change from braided, via a transformational phase, to meandering in the early Late Glacial. This change in fluvial style is explained by climate amelioration at the Late Pleniglacial to Late Glacial transition (at ca. 12.5 k ¹⁴C yr BP) and climate‐related hydrological, lithological and vegetation changes. A delayed fluvial response of ca. 400 ¹⁴C yr (transitional phase) was established. The channel transformations are not related to tectonic effects and sea‐level changes. Successive river systems have similar gradients of ca. 35–40 cm km^?1. A meandering river system dominated the Allerød and Younger Dryas periods. The threshold towards braiding was not crossed during the Younger Dryas, but increased aeolian activity has been observed on the Younger Dryas point bars. The final abandonment of the Niers‐Rhine was dated shortly after the Younger Dryas to Holocene transition. Traces of Laacher See pumice have been found in the Niers valley, indicating that the Niers‐Rhine was still in use during the Younger Dryas. Copyright © 2005 John Wiley & Sons, Ltd.