Soil Pressure and Deformation Analysis of Small Size Deep Foundation Pit

In this paper, the influence of space effect on soil pressure and deformation of deep foundation pit was considered, and the finite soil pressure calculation model was established. The soil pressure of deep foundation pit was calculated by assuming the slip surface and using the finite soil limit equilibrium theory. Then, PLAXIS 3D finite element software was used to establish finite element models of different plane sizes and depths. The distribution regulation of side wall soil pressure and deformation of deep foundation pit was calculated. Finally, the results of finite soil pressure calculation was compared with finite element method. The results shown that: The soil pressure of small deep foundation pit was affected by space effect, and the soil pressure and deformation decrease significantly along the foundation pit depth. Shear fracture Angle was related to the ratio of width to depth of foundation pit, and it was no longer a constant value of 45°+φ/2. Therefore, the spatial effect should be considered in the calculation of soil pressure of small deep foundation pit. The research results can provide some guidance for the design and calculation of similar small size deep foundation pit.

Pengelasan pada Stainless Steel dengan Tipe yang Berbeda Menggunakan Resistance Spot Welding untuk Aplikasi Gerbong Kereta

Salah satu jenis proses pengelasan yang banyak digunakan di dunia industri Kereta Api adalah proses <em>resistance spot welding</em>. Proses pengelasan ini mempunyai banyak keunggulan pada pengelasan pelat tipis dengan menggunakan sambungan tumpang yang diaplikasikan pada <em>side wall</em> kereta api. Penelitian ini dilakukan dengan tujuan untuk mengetahui pengaruh variasi parameter pengelasan yang meliputi <em>current</em>, <em>weld time</em>, dan <em>pulsation</em> terhadap <em>shear strength</em>, struktur mikro dan diameter <em>nugget</em>. Material yang digunakan adalah material SA-240 tipe 304 dan SA-240 tipe 201 dengan ketebalan 2 mm untuk material SA-240 tipe 304 dan tebal 3 mm untuk material SA-240 tipe 201. Pengujian <em>shear strength</em> diperoleh parameter<em> resistance spot welding</em> semakin tinggi, maka nilai <em>shear strength </em>juga semakin tinggi. Strukturmakro didapatkan semakin tinggi <em>current</em>, <em>weld time</em>, dan <em>pulsation</em>, maka <em>nugget</em> semakin lebar. Sedangkan pada hasil uji mikro pada daerah <em>base metal</em> struktur yang tebentuk adalah <em>austenite</em>, sedangkan pada daerah HAZ dan <em>weld metal</em> adalah struktur <em>ferrit</em> dan <em>austenite</em>. Ukuran butir pada daerah HAZ yang semakin mendekat ke daerah <em>weld metal</em> ukuran butirnya menjadi semakin besar. Struktur mikro yang terbentuk pada <em>weld metal</em> bentuknya memanjang (<em>columnar grains</em>) ke daerah yang mengalami pembekuan paling akhir.

Topological description of near-wall flows around a surface-mounted square cylinder at high Reynolds numbers

This study topologically describes near-wall flows around a surface-mounted cylinder at a high Reynolds number ( $Re$ ) of $5\times 10^4$ and in a very thick boundary layer, which were partially measured or technically approximated from the literature. For complete and rational flow construction, we use high-resolution simulations and critical-point theory. The large-scale near-wake vortex is composed of two connected segments rolled up from the sides of the cylinder and from the free end. Another large-scale side vortex clearly roots on two notable foci on the lower side wall. In the junction region, the side vortex moves upwards with a curved trajectory, which induces the formation of nodes on the ground surface. In the free-end region, the side vortex is compressed, which results in a smaller trailing-edge vortex and its downstream movement. Only tip vortices are observed in the far wake. The origin of the tip vortices and their distinction from the near-wake vortex are discussed. Further analyses suggest that $Re$ independence should be treated with high caution when $Re$ increases from 500 to ${O}(10^4)$ . The occurrence of upwash flow behind the cylinder strongly depends on the increase in $Re$ , the mechanism of which is also provided. The separation–reattachment process in the junction region and the trailing-edge vortices are discovered only at a high $Re$ . The former should significantly affect the strength of the side vortex in the junction region and the latter should cause a sharp drop in pressure near the trailing edge.

CFD Modeling of Multiphase Flow in an SKS Furnace with New Tuyere Arrangements

There has been a great deal of focus on the optimization of tuyere arrangements in SKS bottom blown copper smelting furnaces since the last decade, as the improved furnace operation efficiency of SKS technology has potential that cannot be ignored. New –x + 0 + x deg tuyere arrangements with 14 tuyeres are proposed in this research paper. Using a previously verified numerical model, CFD tests on the velocity distribution and wall shear stress for scaled-down SKS furnace models were conducted, with a constant total volumetric gas flow rate, and different operating parameters and furnace cross-section geometries. The results indicate that, at a relatively low gas injection speed compared with the previously optimized tuyere arrangement, although the –x +0 +x deg tuyere arrangements are unable to supply enhanced agitation in the typical round furnaces, they achieve better performance in elliptical furnaces. At a comparatively higher gas injection speed, the – x + 0 + x deg tuyere arrangements can improve the agitation performance in a round furnace while maintaining an acceptable wall shear stress on the bottom and side wall. The agitation enhancement with the − x +0 +x deg tuyere arrangements can essentially be attributed to stronger interactions between bubble plumes and furnace side walls. To further exploit the advantages of the new tuyere arrangements, an optimized tuyere angle was confirmed by a full-scale furnace model simulation.