Investigating the Effect of Ageing on the Behaviour of Chalk Putty

Substantial recent investment in offshore wind energy developments and other foundation projects in chalk dominated locations has created an urgent need for a better understanding of how driven piles behave in this variable and unpredictable material. Pile driving in chalk is known to create a remoulded zone of chalk ‘putty’ around the pile which mobilises low shaft resistance on installation; however, shaft capacity has been reported to increase over time through a process referred to as pile ‘set-up’ or ageing. Although field evidence of ageing has been reported, the potential role of the chalk putty’s behaviour in the ageing process is not well understood. This is partly due to a lack of published laboratory testing on chalk samples which have been conditioned to represent the conditions adjacent to a pile after driving. This paper presents selected results from a suite of laboratory tests undertaken at Imperial College London. Specimens from intact Maastrichtian Chalk were reduced to putty by Proctor compaction applied at natural water content and subjected to either drained or undrained ageing for periods of between 0 and 28 days. Consolidated undrained triaxial tests, with pore water pressure measurement and local strain measurements, were undertaken on the aged specimens, along with thixotropy testing on unconsolidated samples employing a fall cone. An interpretation of the test results within a critical state framework combined with a conceptual small strain stiffness model is presented. The ageing of chalk putty is shown to encompass a combination of consolidation, thixotropic hardening and re-cementation, with small increases in undrained shear strength seen due to thixotropic hardening, and larger increases in strength evident following consolidation

Cardiac sub-study of the IDEAL renal dialysis trial

Abnormalities of cardiac structure and function are common in dialysis patients and cardiovascular disease (CVD) is the major cause of mortality in this group. Heart failure is a common clinical manifestation of CVD and is preceded by left ventricular hypertrophy (LVH) and There are variable reports about the impact of dialysis on LVH, both deleterious and beneficial. Our study investigated whether the timing of the initiation of dialysis impacted upon cardiac structure and function

Criteria for the trivial solution of differential algebraic equations with small nonlinearities to be asymptotically stable

Differential algebraic equations consisting of a constant coefficient linear part and a small nonlinearity are considered. Conditions that enable linearizations to work well are discussed. In particular, for index-2 differential algebraic equations there results a kind of Perron-Theorem that sounds as clear as its classical model expect for the expensive proofs. (orig.)Available from TIB Hannover: RR 6329(97-13) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

A new strategy for vascular complications in young people with type 1 diabetes mellitus

Diabetes vascular complications, including cardiovascular disease, diabetic nephropathy and retinopathy, have a negative effect on the long-term prognosis of young people with type 1 diabetes mellitus (T1DM). Poor glycaemic control and consequent increased HbA1c levels are major risk factors for the development of vascular complications. HbA1c levels are the main focus of current management strategies; however, the recommended target is rarely achieved in adolescents. Thus, a clear need exists for improved biomarkers to identify high-risk young people early and to develop new intervention strategies. Evidence is accumulating that early increases in urinary albumin excretion could be predictive of adolescents with T1DM who are at an increased risk of developing vascular complications, independent of HbA1c levels. These findings present an opportunity to move towards the personalized care of adolescents with T1DM, which takes into consideration changes in albumin excretion and other risk factors in addition to HbA1c levels.M. Loredana Marcovecchio, R. Neil Dalton, Denis Daneman, John Deanfield, Timothy W. Jones, H. Andrew W. Neil ... et al. (on behalf of the Adolescent type 1 Diabetes cardio-renal Intervention Trial (AdDIT) study group