223 research outputs found
Bridge distress caused by approach embankment settlement
Surtees Bridge, which carries the A66(T) over the River
Tees near Thornaby-on-Tees in the UK, has been
showing signs of distress that predate its opening in
1981. Subsequent investigations have shown that the
bridge distress is related to unexpectedly large
settlement of the eastern approach embankment.
Recent ground investigations prompted by a proposed
widening of the river crossing have produced many new
data on the alluvial deposits underlying the site, and
explain why embankment settlement was so much larger
than originally anticipated. Comparison of the
geotechnical parameters obtained from the original and
more recent ground investigations suggests that the
original investigation significantly underestimated the
thickness of an alluvial clay layer underlying the site, and
that its coefficient of consolidation was overestimated.
Settlement analyses using geotechnical data from the
original ground investigations predict moderate
embankment settlements occurring principally during
construction. Settlement analyses based on all the
available data predict far larger embankment
settlements occurring over extended time periods. The
latter analyses predict an embankment settlement
similar to that observed and of sufficient magnitude to
cause the observed lateral displacement of the bridge
due to lateral loading of its piled foundation
QSD IV : 2+1 Euclidean Quantum Gravity as a model to test 3+1 Lorentzian Quantum Gravity
The quantization of Lorentzian or Euclidean 2+1 gravity by canonical methods
is a well-studied problem. However, the constraints of 2+1 gravity are those of
a topological field theory and therefore resemble very little those of the
corresponding Lorentzian 3+1 constraints. In this paper we canonically quantize
Euclidean 2+1 gravity for arbitrary genus of the spacelike hypersurface with
new, classically equivalent constraints that maximally probe the Lorentzian 3+1
situation. We choose the signature to be Euclidean because this implies that
the gauge group is, as in the 3+1 case, SU(2) rather than SU(1,1). We employ,
and carry out to full completion, the new quantization method introduced in
preceding papers of this series which resulted in a finite 3+1 Lorentzian
quantum field theory for gravity. The space of solutions to all constraints
turns out to be much larger than the one as obtained by traditional approaches,
however, it is fully included. Thus, by suitable restriction of the solution
space, we can recover all former results which gives confidence in the new
quantization methods. The meaning of the remaining "spurious solutions" is
discussed.Comment: 35p, LATE
Chiral bosonization for non-commutative fields
A model of chiral bosons on a non-commutative field space is constructed and
new generalized bosonization (fermionization) rules for these fields are given.
The conformal structure of the theory is characterized by a level of the
Kac-Moody algebra equal to where is the
non-commutativity parameter and chiral bosons living in a non-commutative
fields space are described by a rational conformal field theory with the
central charge of the Virasoro algebra equal to 1. The non-commutative chiral
bosons are shown to correspond to a free fermion moving with a speed equal to where is the speed of light. Lorentz
invariance remains intact if is rescaled by . The
dispersion relation for bosons and fermions, in this case, is given by .Comment: 16 pages, JHEP style, version published in JHE
Shear strength model for overconsolidated clay-infilled idealised rock joints
Saturated infilled joints can contribute to the instability of rock masses during undrained shearing. This paper reports an experimental investigation into the effect of the overconsolidation of infilled rough joints on undrained shear behaviour. A revised model is presented for predicting the shear strength of rough infilled joints on the basis of experimental tests carried out on idealised sawtoothed joints with natural silty clay as the infill material. Tests were conducted under consolidated undrained conditions in a high-pressure triaxial apparatus on joints having a dip angle of 60°. Pore pressure development in the infill materials was monitored. The results show that the effect of asperities on shear strength is significant up to a critical asperity height to infill thickness ratio (t/a), whereas the shear behaviour is controlled by the infill alone beyond this critical value. The proposed model for predicting the shear strength of rough infilled joints describes how the OCR influences the shear strength, pore water pressure development, and critical t/a ratio
Chalk-steel Interface testing for marine energy foundations
The Energy Technology Partnership (ETP) and Lloydâs Register EMEA are gratefully acknowledged for the funding of this project. The authors would also like to acknowledge the support of the European Regional Development Fund (ERDF) SMART Centre at the University of Dundee that allowed purchase of the equipment used during this study. The views expressed are those of the authors alone, and do not necessarily represent the views of their respective companies or employing organizations.Peer reviewedPostprin
Downwearing rates on shore platforms of different calcareous lithotypes
Vertical lowering (downwearing) of shore platform surfaces is a very important mechanism in their morphological evolution albeit much remains incompletely understood. The efficacy of mechanical and chemical weathering acting on a given substrate, together with erosional processes, influences downwearing rates. In order to determine the relationship between lithotypes and downwearing rates, data collected from a Transverse Micro-erosion Meter were obtained for shore platforms of three different calcareous lithotypes
(biocalcarenite, calcarenite and carbonated siltstone) along the central Algarve coast (Southern Portugal).
Downwearing rates ranged between 0.096 mm yearâ1 and 1.676 mm yearâ1 in biocalcarenite and weakly cemented calcarenite, respectively. In addition, physical properties of the rocks comprising the platforms were measured, including uniaxial compressive strength (as determined by the Point Load Test), porosity, and calcium carbonate content. The results show that downwearing depends primarily on the intrinsic properties of the substrate. Porosity, in particular, acts in two ways: (i) it tends to weaken the substrate; and, (ii) it controls the downward extent of the water percolation and therefore the depth of the weathering mantle subject to erosion by waves and currents.Portuguese Foundation for Science and Technology (FCT) through Research Projects PTDC/CTEGEX/70448/2006 (BISHOP) and PTDC/CTE-GIX/111230/2009 (EROS)
Physical mechanical consolidation and protection of Miocenic limestone used on Mediterranean historical monuments: the case study of Pietra Cantone (southern Sardinia, Italy)
The present work aims to study the consolidating and protective chemical treatments of the Pietra Cantone, a Miocenic (lower Tortonian) limestone widely used in important monuments and historical buildings of Cagliari (southern Sardinia, Italy). Similar limestones of the same geological period have also been used in several important monuments of Mediterranean area, i.e., Malta and Gozo Islands, Matera (central Basilicata, Italy), Lecce (southern Puglia, Italy) and Balearic Islands (Spain). The Pietra Cantone limestone shows problems of chemicalâphysical decay, due to their petrophysical and compositional char- acteristics: high porosity (on average 28â36 vol%), low cemented muddy-carbonate matrix, presence of phyllosil- icates and sindepositional sea salts (\3%). So, after placed in the monument, this stone is easily alterable by weath- ering chemical processes (e.g., carbonate dissolution and sulfation) and also by cyclic mechanisms of crystalliza- tion/solubilization of salts and hydration/dehydration of hygroscopic phases of the clay component. To define the mineralogical-petrographic features (composition, texture) of limestone, the clay and salt crystalline phases, the optical microscope in polarized light and diffraction anal- ysis were used. To define the petrophysical characteristics (i.e., shape and size distribution of porosity, surface area(SBET), matrix microstructures, rock composition) and interactions of chemical treatments with rock, SEMâEDS analysis and N2 porosimetry with BET and BJH methods were used. To evaluate the efficacy of Na/K-silicates, ethyl silicate consolidants and protective nano-molecular silane monomer water repellent, the mechanical strengths (uni- axial compressive strength, point load and flexural resis- tance), water/helium open porosity, water absorption and vapour permeability data determined before and after the chemical treatments of the Pietra Cantone samples from monument were compared
Experimental determination of the stress-crack opening relation in fibre cementitious composites with a crack-tip singularity
A J -based-fracture-testing method is presented for determining the bridging-stress-crackopening-displacement (Ï-ÎŽ) relationship in fibre-reinforced composites where the crack-tip toughness is not negligible. The J -based technique originally proposed for concrete has been well-established for cementitious composites where the fracture process is primarily dominated by the formation of a fracture-process zone and the contribution of the crack-tip toughness is negligibly small. In this study, the J -based technique is further extended to cover materials for which the crack-tip stress singularity coexists with the fracture-process zone. This extended version of the J -based technique explicitly accounts for the crack-tip singularity while considering the fracture-process zone. This newly derived testing technique has been applied to a high-strength-mortar (HSM) reinforced with carbon and steel fibres where the fibrebridging toughness can be of the same order of magnitude as the crack-tip toughness. The validity of the Ï-ÎŽ relationships deduced has been examined by comparing with results obtained from direct uniaxial tension tests. It is suggested that the J -based-fracture-testing technique can provide reasonable Ï-ÎŽ relationships and fracture parameters in a fibrereinforced HSM.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/44728/1/10853_2004_Article_BF00356823.pd
- âŠ