Evaluation of consolidation parameters of cohesive soils using PCPT method

The piezocone penetration test (PCPT) has emerged as most widely used in situ method for obtaining soil profile as well as physical properties. The PCPT method provides three independent and nearby continuous measurements with the depth; they are: tip stress (qc), sleeve friction (fs) and pore pressure (u1, u2, or u3). These measurements have been successfully used to correlate various soil properties such as undrained shear strength, unit weight and consolidation parameters. This study presents the evaluation of the PCPT interpretation methods for their capability to reasonably estimate the consolidation parameters namely constrained modulus, overconsolidation ratio and vertical coefficient of consolidation (cv) of cohesive soils in Louisiana. Statistical analyses were conducted to evaluate current interpretation methods and to explore new correlations. Test data collected previously from seven sites in Louisiana were used for this. Settlement analysis and monitoring results from five different project sites were used for field verification of PCPT correlations. User friendly Visual Basic program was developed to facilitate the analyses of PCPT data and estimate of magnitude and time rate of settlement under the embankment loading

Nanoindentation characterization of clay minerals and clay-based hybrid bio-geomaterials

Layered hydrous aluminosilicates are key constituent minerals in rocks, soils, and other parts of the Earth crust. Understanding mechanical properties of these aluminosilicates is crucial for seismic study, stability of parent rocks and geomaterials, and for geophysical subsurface exploration. Recently, growing prospects of clay based nanocomposites have renewed further interest in understanding the fundamental elastic and plastic properties of hydrous aluminosilicates. Their distinct, nanoscale layered crystal structure is known to result in anisotropic responses to loading, however, owing to their tiny sizes; it is a significant challenge to determine the anisotropic properties. There is a little data available in the literature on the elastic and plastic properties of clays and clay-based geomaterials. This Ph.D. research work has undertaken the novel approach to study mechanical properties of geomaterials using a pioneering nanomechanical testing method, nanoindentation, to probe the elastic and plastic properties at nano/micro scale. Genesis of these nanomechanical properties are analyzed in the light of microstructures, interatomic bonds, mineralogical and chemical composition. A nanoindentation study of muscovite mica revealed highly anisotropic behavior. Both elastic and plastic anisotropy exist for indentation normal and perpendicular to the basal plane. Nano-mechanical behavior of the well-ordered, nanocrytalline clay minerals is, mainly, governed by generation and storage of dislocations, formation and annihilation of kink bands and intermittent kink bands. Interpretations of indentation test based on continuum mechanics and gradient plasticity models, therefore, give satisfactory result. On the other hand, chemical, morphological, microstructural and structural characterization of a hybrid clay-lime-starch bio nanocomposite material revealed highly heterogeneous, amorphous and multi-phase matrix. Statistical analysis of the massive volume of data obtained using grid indentation technique revealed that this matrix is composed of five distinct mechanical phases. Thus, this study proposes that slow and weak pozzolanic reaction between clay and lime produces cementitious binder network consisting of C-S-H phase. Interaction of the biopolymer (sticky rice) with clay and C-S-H resulted in intercalated nanocomposites that have superior mechanical and barrier properties. Clay, sand, and silt particles act as active fillers in this composite, whereby forming a dense and compact mass, which renders durability and toughness to this hybrid composite

Micromechanical Properties of Nanostructured Clay-Oxide Multilayers Synthesized by Layer-by-Layer Self-Assembly

Clay-based nanostructured multilayers, such as clay-polymer multilayers and clay-oxide multilayers, have attracted growing attention owing to their remarkable mechanical properties and promising application in various fields. In this paper, synthesis of a new kind of nanostructured clay-oxide multilayers by layer-by-layer self-assembly was explored. Nano-mechanical characterization of 18 clay-based multilayer samples, prepared under as-deposited (i.e., air-dried) and annealing conditions at 400 °C/600 °C with different precursor cations and multilayer structure, were carried out using nanoindentation testing, atomic force microscopy (AFM), and X-ray diffraction (XRD). The influencing factors, including as-deposited and annealing conditions and clay concentrations on the mechanical properties were analyzed. Results show that all of the multilayers exhibit high bonding strength between interlayers. Higher modulus and hardness of clay-based multilayers were obtained with lower clay concentrations than that with higher clay concentrations. Different relationships between the modulus and hardness and the annealing temperature exist for a specific type of clay-oxide multilayer. This work offers the basic and essential knowledge on design of clay-based nanostructured multilayers by layer-by-layer self-assembly

Carbon Sequestration Potential of Pasture-Based Systems Along an Altitudinal Gradient in the North-Western Himalayas

The present investigation was carried out in the Chamba district of Himachal Pradesh (India) to identify the pasture-based land use systems being practiced by farmers and to find out their carbon sequestration potential along different altitudes. For carrying out the study, the area was divided into four altitudinal ranges viz., zone-I (\u3c1000 m amsl), zone-II (1000-1500 m amsl), zone-III (1500- 2500 m amsl) and zone-IV (\u3e 2500 m amsl), according to agro-ecological zones in the state. Results revealed that the pasture-based systems practiced by the farmers in the altitudinal zone-I and zone-II were silvo-pasture and pastoral-silviculture, while, at altitudinal zone-III and zone-IV, the pasture-based systems being practiced were pastoral-silviculture and horti-pastoral depending upon the composition of the components. The aboveground biomass was found ranging between 27.78- 38.18 Mg ha-1 among different pasture-based land use systems with maximum aboveground biomass under silvo-pasture system and minimum under pastoral-silviculture. Along altitudinal gradient, aboveground biomass was found to have been increased with values varying between 29.09- 34.12 Mg ha-1 . Belowground biomass ranged between 6.93- 9.80 Mg ha-1 in different systems under consideration and generally showed increasing trend with increasing altitude. Overall biological productivity was found to be highest under silvo-pasture system followed by horti-pastoral and pastoral-silviculture system. Being biologically most productive, silvopasture system stored maximum carbon stock and ultimately sequestered more carbon as compared to the other systems. The estimated vegetation carbon sequestration potential of the pasture-based systems was 63.71- 88.06 Mg ha-1 , while, along altitude the carbon sequestration potential varied from 67.14- 78.62 Mg ha-1 showing increasing trend with altitude

Nanoindentation Characterization of a Ternary Clay-Based Composite Used in Ancient Chinese Construction

Ternary clay-based composite material (TCC), composed of lime, clay and sand, and usually modified with sticky rice and other organic compounds as additives, was widely used historically in Chinese construction and buildings due to its high mechanical performance. In this study, to gain an insight into the micromechanical mechanism of this cementitious material, the nanomechanical properties and volume fraction of mechanically different phases of the binder matrix are derived from the analysis of grid nanoindentation tests. Results show that there are five distinct mechanical phases, where the calcium silicate hydrate (C-S-H) and geopolymer present in the binder matrix are almost identical to those produced in ordinary Portland cement (OPC) and alkali-activated fly-ash geopolymer materials in nano-mechanical performance. The nano-mechanical behavior of calcite produced by the carbonation of lime in this binder is close to the calcite porous outer part of some sea urchin shells. Compared to OPC, the C-S-H contained in the TCC has a relatively lower ratio of indentation modulus to indentation hardness, implying a relatively lower resistance to material fracture. However, the geopolymer and calcite, at nearly the same volume content as the C-S-H, help to enhance the strength and durability of the TCC by their higher energy resistance capacity or higher strength compared to the C-S-H. Rediscovering of TCC offers a potential way to improve modern concrete’s strength and durability through synergy of multi-binders and the addition of organic materials if TCC can be advanced in terms of its workability and hardening rate

Application of Handheld Tele-ECG for Health Care Delivery in Rural India

Telemonitoring is a medical practice that involves remotely monitoring patients who are not at the same location as the health care provider. The purpose of our study was to use handheld tele-electrocardiogram (ECG) developed by Bhabha Atomic Research Center (BARC) to identify heart conditions in the rural underserved population where the doctor-patient ratio is low and access to health care is difficult. The objective of our study was clinical validation of handheld tele-ECG as a screening tool for evaluation of cardiac diseases in the rural population. ECG was obtained in 450 individuals (mean age 31.49 ± 20.058) residing in the periphery of Chandigarh, India, from April 2011 to March 2013, using the handheld tele-ECG machine. The data were then transmitted to physicians in Postgraduate Institute of Medical Education and Research (PGIMER), Chandigarh, for their expert opinion. ECG was interpreted as normal in 70% individuals. Left ventricular hypertrophy (9.3%) was the commonest abnormality followed closely by old myocardial infarction (5.3%). Patient satisfaction was reported to be ~95%. Thus, it can be safely concluded that tele-ECG is a portable, cost-effective, and convenient tool for diagnosis and monitoring of heart diseases and thus improves quality and accessibility, especially in rural areas

Do digital innovations for HIV and sexually transmitted infections work? Results from a systematic review (1996-2017).

OBJECTIVE: Digital innovations with internet/mobile phones offer a potential cost-saving solution for overburdened health systems with high service delivery costs to improve efficiency of HIV/STI (sexually transmitted infections) control initiatives. However, their overall evidence has not yet been appraised. We evaluated the feasibility and impact of all digital innovations for all HIV/STIs. DESIGN: Systematic review. SETTING/PARTICIPANTS: All settings/all participants. INTERVENTION: We classified digital innovations into (1) mobile health-based (mHealth: SMS (short message service)/phone calls), (2) internet-based mobile and/or electronic health (mHealth/eHealth: social media, avatar-guided computer programs, websites, mobile applications, streamed soap opera videos) and (3) combined innovations (included both SMS/phone calls and internet-based mHealth/eHealth). PRIMARY AND SECONDARY OUTCOME MEASURES: Feasibility, acceptability, impact. METHODS: We searched databases MEDLINE via PubMed, Embase, Cochrane CENTRAL and Web of Science, abstracted data, explored heterogeneity, performed a random effects subgroup analysis. RESULTS: We reviewed 99 studies, 63 (64%) were from America/Europe, 36 (36%) from Africa/Asia; 79% (79/99) were clinical trials; 84% (83/99) evaluated impact. Of innovations, mHealth based: 70% (69/99); internet based: 21% (21/99); combined: 9% (9/99).All digital innovations were highly accepted (26/31; 84%), and feasible (20/31; 65%). Regarding impacted measures, mHealth-based innovations (SMS) significantly improved antiretroviral therapy (ART) adherence (pooled OR=2.15(95%CI: 1.18 to 3.91)) and clinic attendance rates (pooled OR=1.76(95%CI: 1.28, 2.42)); internet-based innovations improved clinic attendance (6/6), ART adherence (4/4), self-care (1/1), while reducing risk (5/5); combined innovations increased clinic attendance, ART adherence, partner notifications and self-care. Confounding (68%) and selection bias (66%) were observed in observational studies and attrition bias in 31% of clinical trials. CONCLUSION: Digital innovations were acceptable, feasible and generated impact. A trend towards the use of internet-based and combined (internet and mobile) innovations was noted. Large scale-up studies of high quality, with new integrated impact metrics, and cost-effectiveness are needed. Findings will appeal to all stakeholders in the HIV/STI global initiatives space