Mass Failure Research Articles

Re-evaluation of the structure, function and prognosis of bicuspid aortic valve with different anatomic morphology

Objective To investigate the association between bicuspid aortic valve (BAV) morphologic findings (raphe vs nonraphe), the degree of valve dysfunction and prognosis. Methods Clinical and echocardiographic data in 317 BAV patients were analyzed retrospectively. According to the Sievers classification, the morphologic BAV findings were categorized into no raphe (type 0), one raphe (type 1) and two raphes (type 2). The patients with type 1 were further divided into three subtypes, including R-L subtype (fusion of the left and right coronary cusps), R-N subtype (fusion of the right and noncoronary cusps) and L-N subtype (fusion of the left and noncoronary cusps). Results Of the 317 patients, there were 83 (26.2%) of type 0, 232 (73.2%) of type 1 and 2 (0.6%) of type 2.Among the 232 patients of type 1, there were 126 (54.3%) of R-L subtype, 88 (37.9%) of R-N subtype and 18 (7.8%) of L-N subtype. BAV with raphe had a significantly higher prevalence of aortic valve calcification [120 (51.3%) vs 19 (22.9%), P 0.05). Conclusions The presence of raphe is associated with a higher frequency of significant aortic valve calcification, aortic valve dysfunction, and increases left ventricular mass and left heart failure. The R-N type is also associated with aortic valve calcification and severe aortic stenosis. Key words: Echocardiography; Aortic valve stenosis; Aortic valve insufficiency; Bicuspid aortic valve; Complication

Rock mechanics for design of Brisbane tunnels and implications of recent thinking in relation to rock mass strength

This paper explores the potential implications of recent thinking in relation to rock mass strength for future tunnelling projects in Brisbane, Australia, particularly as they are constructed within deep horizons where the in situ stress magnitudes is larger. Rock mass failure mechanisms for the current tunnels in Brisbane are generally discontinuity controlled and the potential for stress-induced failure is relatively rare. For the road tunnels which have been constructed in Brisbane over the last 12 years, the strength of the more massive rock masses for continuum analysis has been estimated by the application of the Hoek-Brown (H-B) failure criterion using the geological strength index (GSI) to determine the H-B parameters mb, s and a. Over the last few years, alternative approaches to estimating rock mass strength for ‘massive to moderately jointed hard rock masses’ have been proposed by others, which are built on the work completed by E. Hoek and E.T. Brown in this area over their joint careers. This paper explores one of these alternative approaches to estimating rock mass strength for one of the geological units (the Brisbane Tuff), which is often encountered in tunnelling projects in Brisbane. The potential implications of these strength forecasts for future tunnelling projects are discussed along with the additional work which will need to be undertaken to confirm the applicability of such alternative strength criteria for this rock mass.

Analysis of generation and arrival time of landslide tsunami to Palu City due to the 2018 Sulawesi earthquake

Tsunami waves severely damaged the densely populated coast of Palu City immediately after the 2018 Mw 7.5 Sulawesi earthquake. Among the several tsunami waves that arrived to the city, the two initial waveforms were most likely generated by a landslide at the south-western shore of Palu Bay, about 5 km away from one of the city’s shopping malls. The authors accurately identified the arrival time and direction of the waves by comparing multiple videos taken by a pilot from the cockpit of a plane and local people who witnessed waves approaching the coast. Although the authors’ bathymetric survey only covered a limited area of 0.78 km2, it was found that about 3.2 million m3 of mass disappeared from it, causing a maximum decrease in the seabed elevation of 40 m. A landslide scarp up to 5 m height was also investigated in the southwestern shore of the bay, which seems to be relatively minor compared to the submarine mass failure. Visible clue for liquefaction was not observed at this particular site. A simplified numerical model suggests that the landslide tsunami propagated as an edge wave and split into two separate waves due to the presence of an underwater shallow area just north of Palu City. Both waves arrived to the coast of this city within several minutes: one from North-West and the other from the North. Three major waves were witnessed by residents, who felt horizontal and vertical ground movements and heard the sound of an explosion just after the earthquake. Wave splash exceeded the height of trees on the beach. Given the results, the authors conclude that any modern early warning system is unlikely to work well against such short-warning time tsunamis, and thus, it is necessary for disaster risk managers to consider a way to help people quickly become aware of the potential disaster and evacuate.

Exosome-Like Vesicles as New Mediators and Therapeutic Targets for Treating Insulin Resistance and β-Cell Mass Failure in Type 2 Diabetes Mellitus.

Exosome-like vesicles (ELVs), the smallest class of extracellular vesicles released from cells, function in cellular crosstalk and therefore profoundly affect physiologic responses and pathologic progression. A growing body of evidence supports a novel role for ELVs as important mediators and therapeutic targets due to their effects on regulation of both insulin signaling and β-cell mass. Pathologic conditions associated with type 2 diabetes (such as high blood glucose, inflammation, hypoxia, and fatty acids) can alter the quantity and components of ELVs secreted from the pancreas or peripheral insulin-targeting tissues. These released ELVs can either enter the blood circulation or be taken up by neighboring cells or macrophages, which can lead to insulin resistance or β-cell apoptosis. This review focuses on the roles of ELVs in insulin resistance and β-cell failure and also highlights the potential use of ELVs and exosome-based delivery systems in therapeutic interventions aimed at treating type 2 diabetes mellitus as well as the challenges associated with exosome-targeting therapeutics.

Prediction of Overtopping-Induced Breach Process of Cohesive Dams

AbstractBased upon large-scale model tests conducted at Nanjing Hydraulic Research Institute, China, the surface erosion and intermittent mass failure along a dam’s axis and the formation of headcu...

Effect of clay fraction on turbulence characteristics of flow near an eroded bank

Stream-bank erosion in the alluvial channel is a matter of great concern particularly for the irretrievable loss of fertile land. This in effect has direct impact on the agriculture, environment, economy and social issues at large. A series of laboratory experiments were carry out to study the turbulence structure over eroded bank topography. Modulation of mean, turbulent flow characteristics and the benefaction of turbulent bursting structures to the total Reynolds shear stress due to the changed geometry of the eroded bank wall are described for three different clay fraction variations. A side looking micro-acoustic Doppler velocimeter (ADV) was used to record the detailed high frequency velocity data near the bank wall to understand the coupled dynamics of flow and erosion on sediment-water interface. The information on clay and fine sand content of natural river bank was obtained from field observation. Results from the present study indicate that higher turbulence intensities and Reynolds shear stress have prominent role in the removal of bank materials from the bank wall and continues the dislodgement of material from the bank face until mass failure. Quadrant analysis to the random velocity fluctuation in the vicinity of eroded stream-bank shows that downstream bank material movement is strongly correlated to the presence of sweep events. Probability density function (PDF), kinetic energy fluxes and coefficients of skewness and kurtosis of velocity fluctuations show significant changes with the change in clay fraction of the bank material composition. Though the velocity spectral densities are in general observed to be similar for all the three different bank undercut depths for different clay fraction of bank; however, spectral energy shows signature of higher energy peak for lower clay fraction of the bank material.

What Would a Suprapubic Catheter Indwelling for 4 Years Be Like? A Case Report

A 35-year-old male of 165 cm height and weight of 65 kg, had a suprapubic catheter indwelling for 4 years without replacement for urethral stricture. The catheter became gradually obstructed, and urine leaked out around the suprapubic catheter. A lumbar abdominal distension, an inferior abdominal mass and renal failure prompted him to seek medical attention in our hospital in September 2018. This clinical case is hereby presented from 3 aspects of imaging, lab examination, and operation.

Towards O-Level Students’ Performance in Mathematics: Do Teaching and Learning Environment factors matter?

Purpose: This paper is aimed at assessing the possible factors which impacted the mass failure in O-Level mathematics examinations for the year 2012 in Tanzania. Methodology: The paper benefited from the secondary data collected from the Open Data Portal hosted by the Government of Tanzania. Common factors which determine the students‟ performance such as class-size, teacher-students ratio, number of mathematics textbooks and learning environment were examined in different secondary schools across 7 zones in Tanzania to see how much they might have contributed to this poor performance in mathematics. Using ttest statistics, the results show that neither of these common factors had a statistically significant impact in a concerned students‟ performance in mathematics. To test whether the year 2012 students‟ performance in mathematics was statistically significantly different from other neighbouring years, t-statistics was employed to test statistical difference of the mathematics results between 2012 and 2013 and that between 2013 and 2014. Results: The results show that there is a strong significant statistical difference in performance between 2012 and 2013. However, the difference in performance between 2013 and 2014 is reported to be statistically insignificant. These findings propose the possible effect of grading system change between 2012 and 2013 which was an outcry all over country by the education stakeholders. It is thought that change in grading system from division system to GPA system had its large contribution in the poor performance of mathematics in 2012. Recommendation: Following the wide-spread complaints from educational stakeholders that the process of changing the grading system lacked transparency and no clear justification was provided in lowering the pass benchmarks, this paper recommends the education policy makers to involve all key education stakeholders in changing any education policy which might affect the education standards in the country.

The influences of mass failure on the erosion and hydraulic processes of gully headcuts based on an in situ scouring experiment in Dry-hot valley of China

Gully headcut retreat (GHR) is an important processes in gully development, and previous studies have tried to predict GHR rates based on flow hydraulic parameters during runoff scouring, but other dynamics such as gravity also affect GHR processes in addition to flow hydraulics. The aim of this study is to examine the influences of mass failures due to gravity on the erosion and hydraulics processes of gully headcuts during runoff scouring. A flow scouring experiment including 11 tests with two discharges (i.e., 7 tests with 83.3 l min−1 and 4 tests with 166.7 l min−1) was conducted on 5 in situ gully head plots with similar initial topographies. Totally 36 mass failure events were observed of all the 5 gully heads during the experiment, and 63.9% of the events were occurred during the first 10 min of the tests after drying-rewetting cycles. The tests were classified into two series according to whether the mass failure occurred during the scouring. The tests with mass failures (Series I) contributed 81.7% of the total soil loss of GHR, and the average GHR rates by mass (GHRm) was about 5 times higher than that of the tests without mass failures (Series II). The mass failure clearly influenced the flow resistances on gully beds by increasing the surfaces roughness and the sediment load to gully beds, and the average Darcy–Weisbach friction factor (f) and Manning coefficient (n) of Series I were clearly higher than those of Series II. Compared to the previous studies without significant soil collapse from gully heads, the logarithmic growth relationship between GHRm and the energy consumption (ΔEt) was quite weak in this study, but the R2 between GHRm and ΔEt increased for longer time scales. The results indicated that for individual runoff events, GHR rates could not be predicted by flow hydraulics alone because mass failures due to gravity made great contribution, but on longer time scales, the influence of soil collapse is reduced, and flow hydraulics become the key factor impacting GHR processes.

Riverbank Stability under the Influence of Soil Dispersion Phenomenon

AbstractErosion is one of the key factors in environmental management and river restoration. Different mechanisms influence riverbank stability and mass failure, such as seepage erosion. The presen...

Method for Generating a Discrete Fracture Network from Microseismic Data and its Application in Analyzing the Permeability of Rock Masses: a Case Study

The deformation and failure process of rock masses is accompanied by the initiation, propagation and connection of fractures. The behaviors of fractures under engineering disturbance can be effectively determined by microseismic (MS) monitoring, and such information is essential for the stability analysis of rock masses. Based on moment tensor theory, the geometric properties of focal planes and the failure mechanisms of the seismic source can be determined, and this study proposes criteria for extracting the reasonable fracture from focal planes associated with different failure mechanisms and provides a detailed example. The fracture identified by the proposed criteria is called MS-derived fracture, and a formula describing the aperture is derived from the moment tensor theory and the motion characteristics of the MS-derived fractures associated with different failure mechanisms. This work chose the Shirengou Iron Mine as a case and selected an area exhibiting seepage and rock mass failure as the study area. Based on a three-dimensional noncontact discontinuity scan, a natural discrete fracture network (DFN) was generated. With the help of the proposed fracture generation method, a new DFN based on MS data was generated and is referred to as the MS-derived DFN. With the aid of Oda’s theory, the changes in the permeability value, principal direction and anisotropy degree in the study area were analyzed based on the MS-derived DFN, and the seepage channels in the study area were also determined. Therefore, the research methods in this paper could be used to better understand the changes in the permeability of rock masses based on MS data.

Rock mass failure at Baba-dani, a tributary of the Kurobe River, eastern Toyama Prefecture, central Japan with its action to restoration process

Rock mass failure at Baba-dani, a tributary of the Kurobe River, eastern Toyama Prefecture, central Japan with its action to restoration process

Study of Shear Capacity of Jointed Rock Mass with Prestressed Anchor Bolt

Rock mass failure caused by jointed plane is the common disaster in geotechnical engineering. Research on shearing property of jointed rock mass with prestressed anchor bolt and its mechanical property is an aspect for the stability analysis of rock slope and tunnel. This paper studies the stress and deformation of bolt and jointed plane, as well as anchored body and rock mass during shearing by indoor model testing and theoretical analysis. The shearing strength and mechanical property of anchored jointed plane have been systematically studied, and the additional force caused by deformation of prestressed anchor bolt and jointed rock mass during the shearing has been proposed and verified. The anchorage interaction between rock mass and bolt is revealed.

Mechanical Properties and Failure Mechanism of Sandstone with Mudstone Interlayer

In order to study the strength and failure characteristics of sandstone with mudstone interlayer. According to mudstone interlayer dip and distribution form, it can be divided into three kinds of sandstone: sandstone with horizontal mudstone interlayer is Class I; sandstone with inclined mudstone interlayer is Class II; sandstone with irregular distribution mudstone is Class III. The three kinds of sandstone uniaxial test were carried out and combined with the theory of layered rock mass failure, it revealed mechanical properties and failure mechanism of sandstone with mudstone interlayer. The results show that: crack generated from interface in Class I and II and crack generated from irregular distribution mudstone interlayer in Class III; The sandstone with higher strength is destroyed before the mudstone interlayer; sandstone at unbonded interface is failure before sandstone at bonded interface; Three kinds of sandstone vary in compressive strength, Class II is greater than Class III while Class III is greater than Class I.

SUBMARINE MASS FAILURE: WAVE GENERATION BY GRANULAR SLIDES

Submarine mass failures (SMF) are a potential source of hazardous tsunamis. While the link between seismic events and the magnitude of tsunami waves has been extensively studied and corresponding approaches are included in numerical tsunami warning models, the basic implementation of SMF generated waves is subject to ongoing research. In this context, laboratory experiments are essential for the validation of numerical schemes. Most experimental studies apply rigid slide models whereas only few include granular slides (e.g. Watts 1997, Ataie-Ashtiani & Najafi-Jilani 2008, Grilli et al. 2017). The objective of this study is to gain a better insight into the hydraulic processes related to wave generation by submarine granular slides based on experiments as well as establishing a comprehensive data set for the validation of numerical models.

Strength of massive to moderately jointed hard rock masses

The Hoek-Brown (HB) failure criterion and the geological strength index (GSI) were developed for the estimation of rock mass strength in jointed and blocky ground where rock mass failure is dominated by sliding along open joints and rotation of rock blocks. In massive, veined and moderately jointed rock in which rock blocks cannot form without failure of intact rock, the approach to obtain HB parameters must be modified. Typical situations when these modifications are required include the design of pillars, excavation and cavern stability, strainburst potential assessment, and tunnel support in deep underground conditions (around σ1/σci > 0.15, where σ1 is the major principal compressive stress and σci is the unconfined compressive strength of the homogeneous rock) in hard brittle rocks with GSI ≥ 65. In this article, the strength of massive to moderately jointed hard rock masses is investigated, and an approach is presented to estimate the rock mass strength envelope using laboratory data from uniaxial and triaxial compressive strength tests without reliance on the HB-GSI equations. The data from tests on specimens obtained from massive to moderately jointed heterogeneous (veined) rock masses are used to obtain the rock and rock mass strengths at confining stress ranges that are relevant for deep tunnelling and mining; and a methodology is presented for this purpose from laboratory data alone. By directly obtaining the equivalent HB rock mass strength envelope for massive to moderately jointed rock from laboratory tests, the HB-GSI rock mass strength estimation approach is complemented for conditions where the GSI-equations are not applicable. Guidance is also provided on how to apply the proposed approach when laboratory test data are not or not yet available.

Revisiting rock classification to estimate rock mass properties

This paper presents the results of ongoing research carried out by the author exploring methods to provide a more robust estimate of rock mass properties specifically for use in tunnel design. Data from various large-scale rock mass failures are introduced, including coal pillars. The damage-initiation, spalling-limit approach is compared to the coal pillar database. New comparisons of estimating the geological strength index (GSI) and relationships to estimate the Hoek–Brown failure criterion parameters, mb, s and a, are presented.

Granite residual soil properties in collapsing gullies of south China: spatial variations and effects on collapsing gully erosion

Collapsing gully erosion, a special erosion phenomenon in the hilly granitic regions, is an important factor responsible for the deterioration of the ecological environment in southern China. The granite residual soil properties tend to vary with soil depth and their spatial variations have an important impact on the formation and development of collapsing gullies. Here, two typical granitic soil profiles in the north boundary of collapsing gully erosion in south China were selected to investigated the spatial variations of soil physicochemical, hydraulic, and mechanical properties along the profile and their influences on collapsing gully erosion. The upper two soil layers (surface soil layer and red soil layer) were significantly different from the lower two soil layers (sandy soil layer and detritus layer) in the investigated properties. The soil texture performed a large variation along the profile, which might be a positive factor for the formation of secondary vertical joints, faults, and weak structural planes. Meanwhile, the lower soil layers had a lower value of PL, LL, organic matter, and iron‑aluminum oxides, demonstrating their poor structure and vulnerability to erosion under rainfall conditions. Additionally, the upper soil layers had a higher water-holding capacity, but a lower decreasing rate in the unsaturated coefficient of permeability, leading to the overburdening of the lower soil layers under rainfall conditions. And the low soil layers had a low shear strength, which could also lead to the sliding of the gully head and sidewall, especially under saturated conditions. Collectively, the special geological structure of the granite residual soil layers plays an important role in the occurrence and development of collapsing gully erosion. The data reported in this paper may facilitate a better understanding of soil mass failure on the gully head and the collapsing gullies.

Mass Media Success and Failure in the Horn of Africa (HoA): A Preliminary Review of the Cases from Ethiopia and Sudan

As many African countries are liberalising, deregulating their economies and allowing more freedom, many others are on the opposite side - restricting and showing a digressing media atmosphere. The aim of this study is to examine why the media in two Eastern African countries Sudan and Ethiopia fail or have failed in the past decade and how the international community could assist their sustainability. Both countries have strong state owned media but very weak private (free) press. In the overarching study, archival and official national data analysis and semi-structured interviews are conducted to collect empirical data from each country. Theoretically, as there is no media related theory available to study mass media sustainability, theories from economics such as Systems Theory and the Four Capital Model have been consulted. The study has found that due to “contextual” reasons most media outlets fail in the countries and shows what the international community could do to assist sustainability in the countries.

Private Equity in Higher Education Sector in India- Need of the Hour!

Setting up of an educational institution is not easy and requires a lot of regulatory formalities to be completed before opening and during its operations. If it is shut down within initial phase it is painful as well as legally difficult to close it, especially in India. It has been observed that a significant number of academic institutions of technical higher education have been shut down by the promoters due to lack of financial viability, lack of knowledge of about the business, poor management, and other social factors. The present study is an attempt to find out the reasons of mass failure of many technical higher education institutions and to suggest a unique financing model in order to ensure the quality of education and long-term benefit for the promoters by maintaining financial discipline.