On the assessment of non-metallic inclusions by part 13 of API 579 -1/ASME FFS-1 2016

Improvement of nondestructive inspection techniques has allowed more frequent detection of closely spaced zones of non-metallic inclusions in pressure vessels made of low carbon steel. In the present study, closely spaced inclusions in an in-service cylindrical horizontal pressure vessel were detected by Scan-C ultrasonic inspection and considered as laminations to be assessed by Part 13 of the API 579-1/ASME FFS-1 2016 standard. The outcoming results were considered as a rejection for Level 1 assessment, and a repair or replacement of the component was required, even though it retained a significant remaining strength. Thus, an alternative procedure to assess the mechanical integrity of pressure vessels containing zones of non-metallic inclusions is proposed by adopting some criteria of the API 579-1/ASME FFS-1 Part 13 standard procedure and taking into consideration the dimensions and grouping characteristics of the inclusion zones.

Understanding of Vertical and Horizontal Pressure Barriers in the Naturally Fractured Carbonate Field

The Karachaganak field is a massive reef carbonate structure. The main reservoir is of the late Devonian-Carboniferous age, where sequence stratigraphic cycles of progradation and aggradation defining the growth stages of the carbonate build-up have been revealed. Vertical and horizontal semiconductive barriers was identified in the reservoir during the field development. It was assumed that these barriers are located at the boundaries of the changing depositional cycles, which took place during the reef structure growth. According to the simulation results on a sector model of the reservoir it was determined that the pressure barriers can be developed due to different fracture intensities observed in the reservoir and not because of rock property as such. The reason for the different fracture densities may be associated with compaction during primary diagenesis and may have a sync-depositional nature, which can be seen on carbonate structure outcrops.

Marine boundary layers above heterogeneous SST: Along-front winds

Turbulent flow in a weakly convective marine atmospheric boundary layer (MABL) driven by geostrophic winds Vg = 10ms−1 and heterogeneous sea surface temperature (SST) is examined using fine mesh large eddy simulation (LES). The imposed SST heterogeneity is a single-sided warm or cold front with jumps Δθ = (2, −1.5)K varying over a horizontal x distance of 1 km characteristic of an upper ocean mesoscale or submesoscale front. The geostrophic winds are oriented parallel to the SST isotherms, i.e., the winds are along-front. Previously, Sullivan et al. (2020) examined a similar flow configuration but with geostrophic winds oriented perpendicular to the imposed SST isotherms, i.e., the winds were across-front. Results with along-front and across-front winds differ in important ways. With along-front winds the ageostrophic surface wind is weak, about 5 times smaller than the geostrophic wind, and horizontal pressure gradients couple the SST front and the atmosphere in the momentum budget. With across-front winds horizontal pressure gradients are weak and mean horizontal advection primarily balances vertical flux divergence. Along-front winds generate persistent secondary circulations (SC) that modify the surface fluxes as well as turbulent fluxes in the MABL interior depending on the sign of Δθ. Warm and cold filaments develop opposing pairs of SC with a central upwelling or downwelling region between the cells. Cold filaments reduce the entrainment near the boundary-layer top which can potentially impact cloud initiation. The surface-wind SST-isotherm orientation is an important component of atmosphere-ocean coupling. The results also show frontogenetic tendencies in the MABL.

A Review on Dynamic Analysis and Design of R.C.C Solids Storage Structure

Aim of research paper is to compare and briefly describe about the advantage and limitations of solid storage structure by using Staad Pro Structural software. Solid storage structures are considered as special structures as its design is based on the properties of materials stored. The pressure exerted by the stored material on the side of a bin varies with the processes and arrangements of filling and emptying operations. Due to this variation, it is extremely difficult to analyze the pressure exerted on the walls of the bins. In our research work, we are designing the RCC solid storage structure located in all seismic zones with the help of structural software Staad Pro. The design concept include, all dimensions of structural component based on trial and error method, using Equivalent lateral force method in term of Comparison of different models of concrete solid storage structure for earthquake such as nodal displacement, stress and vertical or horizontal pressure on walls etc. for volume of 180 m3. All the designs have been based on the recommendations of I.S 4995 -1974 (part 1&2) and I.S 456 – 2000 codes, Based on these designs, that dimension of solid storage structures shows least amount of concrete and steel. Main objective of our research work is to compare of different models of concrete solid storage structure for earthquake in terms of nodal displacement, stress and vertical or horizontal pressure on walls etc.

Rayleigh–Bénard Instability of an Ellis Fluid Saturating a Porous Medium

The Ellis model describes the apparent viscosity of a shear–thinning fluid with no singularity in the limit of a vanishingly small shear stress. In particular, this model matches the Newtonian behaviour when the shear stresses are very small. The emergence of the Rayleigh–Bénard instability is studied when a horizontal pressure gradient, yielding a basic throughflow, is prescribed in a horizontal porous layer. The threshold conditions for the linear instability of this system are obtained both analytically and numerically. In the case of a negligible flow rate, the onset of the instability occurs for the same parametric conditions reported in the literature for a Newtonian fluid saturating a porous medium. On the other hand, when high flow rates are considered, a negligibly small temperature difference imposed across the horizontal boundaries is sufficient to trigger the convective instability.

An Experimental Study of a Nailed Soil Slope: Effects of Surcharge Loading and Nails Characteristics

The earth nailing system is a ground improvement technique used to stabilize earth slopes. The behavior of the earth nailing system is dependent on soil and nailing characteristics, such as the spacing between nails, the orientation, length, and method of installation of nails, soil properties, slope height and angle, and surcharge loading, among others. In the present study, a three-dimensional physical model was built to simulate a soil nailed slope with a model scale of 1:10 with various soil nail characteristics. The simulated models consist of Perspex strips as facing and steel bars as a reinforcing system to stabilize the soil slope. Sand beds in the model were formed, using a sand raining system. The performance of nailed soil slope models under three important nails characteristics, i.e., length, spacing and orientation, with varying surcharge loading were studied. It was observed that there is a reduction in the lateral movement of slope and footing settlements with an increase in length. It was found that the slope face horizontal pressure is non-linear with different nail characteristics. The increase in length and inclination of the soil nails decreased the vertical, horizontal stress and footing settlement, while the increase in spacing of the nails increased the vertical and horizontal stress behind the soil mass.

Numerical forward modelling of the overpressure build-up in the Cenozoic section of the Central Graben in the North Sea

One of the most widespread hypotheses for the origin of the present-day overpressure in the shale Post-Chalk section in the North Sea is the very rapid sedimentation from Neogene to present day. We tested this hypothesis by the means of numerical forward finite elements modelling and successfully simulated the overpressure build-up during the Cenozoic filling of the North Sea with relatively simple model set-up. Our model shows that overpressure of approximately 28% above hydrostatic developed in the Neogene, while during the Quaternary, it reached up to 36% above hydrostatic. At present day, the predicted onset of overpressure starts at about 800–1000 m below seafloor, while the maximum (magnitude about 1.36 sg, i.e. 36% above the normal hydrostatic pressure) is at approximately 2100 m. This overpressure profile fits reasonably well with data from wells drilled in the Central Graben. The exact magnitude of the overpressure depends on the used assumptions, the model set-up and the values of the input parameters. Especially the dynamic interaction between high sedimentation rates, clay permeability and low horizontal pressure gradient seems to be a key factor in the efficiency of dewatering of saturated clays during burial. The results indicate that, the assumption of horizontal stress isotropy results in nearly no horizontal fluid flow, despite the same magnitude for the vertical and the horizontal permeability. In these conditions, the vertical permeability plays much bigger role than the horizontal one in the effective de-watering of the sediments during burial. Further investigation is needed to explore the role of horizontal pressure gradient in fluid migration in passive sedimentary basins.

Study on the horizontal bearing characteristics of pile foundation in coral sand

This paper presents the horizontal bearing characteristics of piles in coral sand and silica sand from comparative experimental studies. A total of 6 model piles with different diameters are tested. The horizontal bearing capacity, deformation characteristic, bending moment, p-y curve, the change in soil horizontal pressure, as well as the particle breakage behaviour of coral sand are investigated. The results show that, in coral sand foundation, the horizontal bearing capacities of piles and the increments of soil horizontal pressures are obviously greater than those in silica sand. Accordingly, the lateral displacement, the rotation of pile head, the bending moment and the corresponding distribution depth in coral sand are significantly smaller than that in silica sand. The p-y curves indicate that the horizontal stiffness of coral sand is greater than that of silica sand. Remarkably, the breakage behaviour of coral sand is mainly distributed in the range of 10 times pile diameter depth and 5 times pile diameter width on the side where the sand is squeezed by pile. Furthermore, in coral sand, the influence of pile size is more pronounced, the squeezing force generated by pile spread farther and its influence range is larger compared to those in silica sand.

Exploring horizontal pressure gradient (HPG) schemes for general vertical coordinates.

<p>Terrain following coordinates allow for better representation of physics at the sea-bed than traditional z-coordinates but result in numerical discretisation errors in the calculation of the horizontal pressure gradient (HPG) which manifest as spurious currents.  As of NEMO r4.0.4, there were two HPG schemes available for use with terrain following coordinates, the traditional 2<sup>nd</sup> order sco scheme and the 3<sup>rd</sup> order prj scheme.  The prj scheme, while highly accurate in the ocean interior, shows unphysical behaviour at the sea-bed for steeply sloping bathymetry.  A task in the IMMERSE project was set up to identify, implement and test promising HPG schemes suitable for general vertical coordinates that are accurate, robust and physically consistent.  As part of this task, the 3<sup>rd</sup>-order accurate density Jacobian scheme (djc) as proposed by Shchepetkin and McWilliams (2003) has now been implemented in the NEMO trunk (as a rewrite of the previously existing but non-operational djc scheme).  Idealised testing has shown this scheme to be significantly more accurate than the sco scheme, and more robust than the prj scheme in coping with steeply sloping bathymetry.  Initial results from applying the djc scheme in a challenging realistic configuration (the AMM7 with hybrid s-z-coordinates and non-uniform vertical discretisation) show a reduction in spurious currents with respect to the sco scheme.  The prj scheme is highly sensitive to the rmax (maximum permitted slope) criterion.  In cases where the bathymetry is so steep that a velocity-point may lie multiple levels below one of its neighbouring tracer-points, the nature of the prj near-bed HPG calculation leads to sudden spin-ups of spurious velocities which can exceed those of the djc scheme in the longer-term.  Performance-wise, the djc scheme is 3 times slower than the sco scheme, but less expensive than the prj.  Further work is planned to reduce the memory footprint.  In addition to continued testing of the djc scheme, further work will look at alternative formulation (finite volume) HPG schemes, and high order variants.</p><p>This work is distributed under the Creative Commons Attribution 4.0 License. This licence does not affect the Crown copyright work, which is re-usable under the Open Government Licence (OGL). The Creative Commons Attribution 4.0 License and the OGL are interoperable and do not conflict with, reduce or limit each other.</p>