The Effect of Heavy-Duty Vehicle Crossings on the State of Stress of Buried Pipelines

The aim of this article is to quantify the loads exerted by heavy-duty vehicles when crossing over buried pipeline. This problem arises in connection to the question pertaining to the use of protective sleeves (casings) applied to gas pipelines in regions with increased demands on pipeline operation safety. An experiment was conducted on a test pipe section made from L360NE pipeline steel equipped with strain gauges along the pipe perimeter, measuring strains in the axial and circumferential directions. Strain measurements were taken after back-filling the pipe trench, then during vehicle crossings over the empty pipe, and again after pressurizing the test pipe with air. Strain-based hoop stresses at the surface of the empty test pipe were found to exceed 30 MPa after back-filling the trench and increased to more than 40 MPa during the vehicle crossings. Similarly, axial stresses reached extremes of around 17 MPa in compression and 12 MPa in tension. Applying internal air pressure to the test pipe resulted in a reduced net effect on both the hoop and axial stresses.

Advantages and Limits of Remote Care and Stress Management Experienced by Mothers of Students with Specific Learning Disabilities During the Covid-19 Period

These instructions give you guidelines for preparing papers. Use this document as a template if you are using Microsoft Word. Otherwise, use this document as an instruction set.. Define all symbols used in the abstract. Do not cite references in the abstract. Do not delete the blank line immediately above the abstract; it sets the footnote at the bottom of this column. Page margins are 1,78 cm top and down; 1,65 cm left and right. Each column width is 8,89 cm and the separation between the columns is 0,51 cm. Abstract-Introduction : The period of confinement due to the COVID-19 pandemic has harmful consequences on the psychological state of parents and their children, especially those with psychological or neurocognitive problems. The care of these children plays a primordial role in their development, particularly during the COVID-19 period. For this reason, our objective is to assess the state of stress among mothers of children with learning disabilities during the COVID-19 period in Morocco, as well as the support of these children. Materials and methods : This is a cross-sectional study that was conducted during the period from April to June 2020. To realise it, we used a investigation form which contains three parts. To evaluate the state of stress in mothers, we used the "PSS10d" scale adapted to the Moroccan context. The target population is composed of mothers of children with learning disabilities who are being monitored by Moroccan Association for Learning Disorders and Difficulties (MALDD) in Casablanca. Results : During the period of confinement, only 13% (n=15) of mothers reported that their children "Dys" had benefited from remote remediation by specialists According to the Odds Ratio calculation, the risk factors influencing the care of "Dys" children during this period of confinement are: lack of cooperation from the child (Odds Ratio= 16.8; IC95%=[3.5-79]). 1]; P-value=0.001), the educational level of mothers (Odds Ratio= 9.4; IC95%=[2.4-35.7]; P-value=0.001), the economic situation (Odds Ratio= 5.1; IC95%=[1.5-17.4]; P-value=0.01) and technical problems (Odds Ratio= 5.1; IC95%=[1.5-17.4]; P-value=0.01). Conclusion : According to our results, we noticed that the psychological state of the mothers is influenced by the remote care of the "Dys" children. For this the responsible authorities in Morocco must support this population.

Effect of Pin Geometry and Orientation on Friction and Wear Behavior of Nickel-Coated EN8 Steel Pin and Al6061 Alloy Disc Pair

Most mechanical systems (in particular, gear transmission system) undergo relative motion which results in increased friction phenomenon (friction coefficient, stresses, and wear rate) and thereby results in loss of efficiency. Mechanical parts undergo relative motion in different geometry configurations and orientations that induce a different state of stress as a result of friction. Till date, attempts are being made to minimize the friction with full sphere pin geometry configuration. The present work focused to reduce the frictional and wear rate, and experiments are conducted with tribo-pairs. i.e., nickel-coated pin surface slide against Al6061 alloy disc. The friction studies are carried out at different loads and geometries of pin surfaces (sphere and hemisphere configured at different orientations such as full sphere and hemisphere configured at 0°, 45°, and 90°) to induce different stress states with reference to sliding directions. Change in the geometry of EN8 pin material and their orientation with reference to sliding direction resulted in a different state of stress. The resulting stress levels were examined under the scanning electron microscope, which revealed the mechanisms of adhesion, abrasion, and extrusion. At a lower magnitude of orientation and load, the extent of asperity breaking lessens and material removal from pin surface decreases. Abrasion wear mechanism was observed corresponding to full sphere configuration on Al 6061 disc, whereas adhesive wear mechanisms are seen with hemisphere pins. The amount of aluminum transfer on pin surface with a hemisphere pin is comparatively more than that of full sphere configuration. At a lower magnitude of state of stress, the mechanism of sliding was dominated by the adhesion effect. At a higher level of state of stress, the mechanism of sliding was dominated by abrasion and extrusion.

Wellbore Integrity: An Integrated Experimental and Numerical Study to Investigate Pore Pressure Variation during Cement Hardening under Downhole Conditions

Summary Understanding the cement hardening process and determining the development of the state of stress in the cement under specific downhole conditions are challenging but fundamental requirements to perform an accurate prediction of wellbore integrity. As an essential component of the state of stress, the temporal variation of cement pore pressure is a critical factor that affects the occurrence of cement failure. In this study, we present a novel laboratory setup to measure the cement pore pressure variation during hardening under representative downhole conditions, including the pressure, temperature, and water exchange between the cement and formation. The pore pressure measurements are further incorporated with a staged finite element analysis (FEA) approach to investigate the state of stress development during cement hardening and to evaluate cement failure under different operations and after different wait-on-cement (WOC) periods. The laboratory measurements show that the external water supply from the formation significantly impedes the pore pressure drop in the cement. The numerical results indicate that the accelerated pore pressure decrease obtained without considering downhole conditions elevates the contact pressure at the cement-formation interfaces significantly and moderately increases the von Mises stress in the cement. The numerical results further predict that the accelerated pore pressure decrease leads to an overestimation of shear failure during pressure testing and steamflooding operations but an underestimation of debonding failure during severe fluid loss and injection-related cooling processes. Based on the results of the integrated laboratory and numerical approach, qualitative and quantitative suggestions are provided for field operations to inhibit wellbore integrity risk during the wellbore life cycle.

Dislocations in an arbitrary angle wedge. Part I: The dislocation kernel

We consider the state of stress created by the presence of an edge dislocation at an arbitrary position, in a wedge of arbitrary internal angle. A method for determining the state of stress in the wedge is demonstrarted and verified against finite element method simulations. Furthermore, a Mellin transform is employed to ensure that the free surfaces of the wedge remain traction free along their length.

Mining-Induced Seismicity during Development Works in Coalbeds in the Context of Forecasts of Geomechanical Conditions

Mining-induced seismicity in the area of development works and proper mining operations is one of the major determinants of the rockburst hazard level in underground mines. Rockburst hazard assessment in Polish collieries is performed by a variety of mining and geophysical methods, including seismic and seismoacoustic techniques, borehole surveys, small diameter drilling, rock strata profiling and analyses of geomechanical properties of rocks, geological structure and geological mining conditions. In the case of zones particularly exposed to potential hazards, it is recommended that analytical or numerical forecasts of the state of stress in the vicinity of workings should be used already at the stage of planning of mining operations. This study summarises the comparative analysis of seismic test data and analytical forecasts of the state of stress in five selected headings in one of the burst-prone collieries within the Upper Silesia Coal Basin in Poland (USCB). As regards the seismic data, duly defined quantitative indicators and energy criteria of the registered seismic activity are recalled in the assessment of rockburst hazard level during the roadheading operations. Analytical simulations utilise a developed geomechanical model and stress–strain relationships stemming from the principles of elastic media mechanics. From the standpoint of mining engineering practice, interpretation of results obtained by the two methods reveals how effective analytical models will be in prognosticating or verification of rockburst hazard conditions.

Geomechanical simulation of energy storage in salt formations

A promising option for storing large-scale quantities of green gases (e.g., hydrogen) is in subsurface rock salt caverns. The mechanical performance of salt caverns utilized for long-term subsurface energy storage plays a significant role in long-term stability and serviceability. However, rock salt undergoes non-linear creep deformation due to long-term loading caused by subsurface storage. Salt caverns have complex geometries and the geological domain surrounding salt caverns has a vast amount of material heterogeneity. To safely store gases in caverns, a thorough analysis of the geological domain becomes crucial. To date, few studies have attempted to analyze the influence of geometrical and material heterogeneity on the state of stress in salt caverns subjected to long-term loading. In this work, we present a rigorous and systematic modeling study to quantify the impact of heterogeneity on the deformation of salt caverns and quantify the state of stress around the caverns. A 2D finite element simulator was developed to consistently account for the non-linear creep deformation and also to model tertiary creep. The computational scheme was benchmarked with the already existing experimental study. The impact of cyclic loading on the cavern was studied considering maximum and minimum pressure that depends on lithostatic pressure. The influence of geometric heterogeneity such as irregularly-shaped caverns and material heterogeneity, which involves different elastic and creep properties of the different materials in the geological domain, is rigorously studied and quantified. Moreover, multi-cavern simulations are conducted to investigate the influence of a cavern on the adjacent caverns. An elaborate sensitivity analysis of parameters involved with creep and damage constitutive laws is performed to understand the influence of creep and damage on deformation and stress evolution around the salt cavern configurations. The simulator developed in this work is publicly available at https://gitlab.tudelft.nl/ADMIRE_Public/Salt_Cavern.