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.

Projection-based stereolithography for direct 3D printing of heterogeneous ultrasound phantoms

Modern ultrasound (US) imaging is increasing its clinical impact, particularly with the introduction of US-based quantitative imaging biomarkers. Continued development and validation of such novel imaging approaches requires imaging phantoms that recapitulate the underlying anatomy and pathology of interest. However, current US phantom designs are generally too simplistic to emulate the structure and variability of the human body. Therefore, there is a need to create a platform that is capable of generating well-characterized phantoms that can mimic the basic anatomical, functional, and mechanical properties of native tissues and pathologies. Using a 3D-printing technique based on stereolithography, we fabricated US phantoms using soft materials in a single fabrication session, without the need for material casting or back-filling. With this technique, we induced variable levels of stable US backscatter in our printed materials in anatomically relevant 3D patterns. Additionally, we controlled phantom stiffness from 7 to >120 kPa at the voxel level to generate isotropic and anisotropic phantoms for elasticity imaging. Lastly, we demonstrated the fabrication of channels with diameters as small as 60 micrometers and with complex geometry (e.g., tortuosity) capable of supporting blood-mimicking fluid flow. Collectively, these results show that projection-based stereolithography allows for customizable fabrication of complex US phantoms.

Numerical Study on the Effects of Vegetation on the Intradelta Lobe Avulsion

<p>Coastal wetlands play an important role for both human society and coastal ecosystems. The intradelta lobe avulsion, which causes channel shift inside the delta lobe, can create new coastal wetlands and benefit wetland restoration. Previous studies suggest that intradelta lobe avulsion is controlled by the river mouth bar stagnation that results in back filling of the river channel, which further increases the overbank flow at the natural levees and eventually leads to the avulsion. However, the natural levees are commonly colonized by vegetation, and its relevant effects on the avulsion at the levees are still elusive. In this study, we aim to quantify the effects of vegetation on the occurrence of intradelta lobe avulsion at the natural levees through numerical experiments using Delft3D. Numerical simulations of vegetated and non-vegetated scenarios were conducted with different combination of vegetation height and density, river discharge, suspended-sediment concentration and Chezy coefficient. The model results show that the existence of vegetation results in shorter levee length and river mouth bar distance relative to those of non-vegetated scenarios. The levee length and the river mouth bar distance are primarily dictated by the Chezy coefficient and the representative Chezy coefficient for non-vegetated and vegetated scenarios, respectively. In addition, the time scales of river mouth bar stagnation and the intradelta lobe avulsion tend to be shorter for vegetated scenarios, which is presumably due to the shorter river mouth bar distance that leads to a smaller accommodation space for back filling of the river channel. Our findings have important implications for predicting the future avulsion of intradelta lobe and improving the management of deltas and estuaries.</p>

Effect of apexification on occlusal resistance of immature teeth

Background Strain distribution was investigated to assess the occlusal resistance alterations in immature teeth under different occlusal force. Methods In vitro apexification models of teeth with a funnel-shaped immature apex were obturated with mineral trioxide aggregate (MTA; ProRoot MTA) using different combinations of core materials (10/group): group 1, full-length orthograde obturation of MTA; group 2, a 5-mm MTA apical plug with a composite core; group 3, a 5-mm MTA apical plug and back-filling with warm gutta-percha. Teeth with calcium hydroxide (CH)-medicated canals and untreated teeth with normal apices were tested as controls. The teeth were arranged between two adjacent normal-apex teeth, embedded in a resin mold with a simulated periodontal ligament space. Strain data were recorded from the 3-unit teeth assembly under static compressive occlusal forces (50, 100, 200, and 300 N). Measurements were repeated 20 times for each condition, and the data were statistically analyzed. Results The immature teeth showed altered occlusal force resistance, placing increased strain on adjacent teeth. Teeth with CH-medicated canals showed significantly inferior occlusal resistance under all tested forces (P < 0.05). Application of an MTA plug with deep composite resin core resulted in significantly better stress-bearing capacity especially under forces of 50 and 300 N (P < 0.05). Conclusions The pattern of occlusal force distribution in immature teeth differed according to the canal obturation materials used for apexification. Immature teeth with an MTA apical plug showed more favorable occlusal force resistance than those with CH-medicated canals.

Sumber Daya Mineral Pasir Kuarsa Sebagai Alternative Pengembangan Usaha Pertambangan Di Daerah Kading Kabupaten Barru

Tujuan penelitian ini untuk merancang kewirausahaan suatu usaha pertambangan sumber daya mineral pasir kuarsa yang berwawasan lingkungan. Lokasi penelitian di daerah Kading Kecamatan Tanete Riaja. Penelitian dilakukan dengan cara survey dan pemetaan. Pembangunan usaha pertambangan yang berwawasan lingkungan mensyaratkan adanya pengelolaan sumber daya yang bijaksana. Di sisi lain usaha pertambangan tersebut memberikan resiko terhadap kerusakan lingkungan. Olehnya tindakan pengendalian lingkungan adalah upaya yang harus diperhitungkan dalam perencanaan pertambangan yang berwawasan lingkungan. Berdasakan hasil penelitian endapan pasir kuarsa yang terdapat di daerah penelitian menunjukkan kadar SiO2 = (85 – 90) %, sehingga dapat digunakan sebagai bahan baku pembuatan semen di Pabrik Semen Bosowa dan Pabrik Semen Tonasa. Pasir kuarsa tersebut menyebar pada daerah seluas 30 ha, mempunyai cadangan terukur 5.175.000 ton, mining recovery 90 % sehingga cadangan layak tambang adalah 4.657.500 ton. Penambangan yang cocok diterapkan di wilayah penelitian adalah tambang terbuka dengan system teras-teras, penggalian dilakukan dengan metode back filling. Peralatan tambang yang diperlukan adalah excavator dan dump truck. Rencana produksi 120.000 ton/tahun, sehingga umur tambang 38,81 tahun. Rencana pemasaran PT Semen Tonasa Pangkep dan PT Semen Bosowa Maros untuk bahan baku pengoreksi industri semen, harga jual Rp 100.000 per ton logo gudang pabrik semen.

PENGELOLAAN LINGKUNGAN PADA KEGIATAN OPERASI TAMBANG DARAT BIJIH TIMAH MENGGUNAKAN METODE BOREHOLE MINING DI WIUP PT. TIMAH, TBK

ABSTRAK Borehole mining (BHM) merupakan metode penambangan menggunakan aliran air bertekanan tinggi (water jet) dan dikombinasikan dengan sistem pemompaan slurry dari bawah tanah. Dalam upaya meningkatkan produksi bijih timah, PT. TIMAH, Tbk melakukan kegiatan penambangan menggunakan metode BHM. Pemilihan metode penambangan BHM bertujuan untuk menambang sumberdaya marginal tanpa memerlukan stripping overburden (OB), dengan prinsip kerja: membuat lubang vertikal hingga dasar zona target menggunakan alat holemaker; dengan memanfaatkan tekanan water jet, air akan memberai material di sekelilingnya; saat material terberai, pompa tanah siap menghisap slurry hingga ke permukaan. Kapasitas penambangan efektif menggunakan metode BHM adalah 750 m3/bulan, dengan jam jalan efektif alat 125 jam/bulan. Kegiatan penambangan dengan metode BHM ini, berpotensi menimbulkan masalah lingkungan diantaranya terbentuknya lubang bekas penambangan (void) dan genangan air di sekitar lokasi tambang. Pemindahan tanah dari bawah permukaan pada kegiatan ore getting dengan volume 750 m3 dapat mengganggu struktur dan kekuatan tanah sehingga menyebabkan runtuhan/amblesan yang pada akhirnya menghasilkan void. Pengelolaan lingkungan yang tidak baik dapat menimbulkan masalah yang serius terhadap bentang lahan dan akan menimbulkan dampak turunan seperti masalah sosial. Perencanaan desain penutupan lahan dengan metode backfilling menjadi terobosan untuk mengatasi void yang ada. Prinsipnya, material yang akan diambil pada titik penambangan berikutnya ditransfer ke void sebelumnya yang telah terbentuk dan demikian seterusnya. Di samping itu, dilakukan revegetasi di sekitar lokasi penambangan BHM untuk meningkatkan daya dukung tanah. Limpasan air ke permukaan secara kontinu menyebabkan kondisi lahan sekitar menjadi lembab (jenuh air) sehingga daya dukung tanah menurun. Kegiatan penambangan menggunakan metode BHM di PT. TIMAH, Tbk memang merupakan suatu terobosan dalam konservasi cadangan bijih timah. Namun, aspek lingkungan juga menjadi hal yang perlu diperhatikan. Pengelolaan lingkungan yang tepat dapat meminimalkan masalah lingkungan yang terjadi. Lubang-lubang berdiameter 1,5 hingga 3 meter yang dihasilkan dapat diatasi dengan sistem back-filling. Limpasan air di permukaan diatasi dengan perencanaan sistem penirisan tambang yang terencana yaitu dengan pembuatan jalur/paritan di sekitar area penambangan. Kata kunci: borehole mining, void, backfilling ABSTRACT Borehole mining (BHM) is a mining method using high pressure water flow (water jet) and combined with an underground slurry pumping system. In an effort to increase tin ore production, PT. TIMAH, Tbk conducts mining activities using the BHM method. The selection of the BHM mining method aims to mine marginal resources without the need for stripping overburden (OB), with the working principle: making vertical holes to the bottom of the target zone using a holemaker; by utilizing the pressure of a water jet, water will fill the surrounding material; when the material is dispersed, the ground pump is ready to suction the slurry to the surface. The effective mining capacity using the BHM method is 750 m3 / month, with effective road hours of 125 hours / month. Mining activities using the BHM method have the potential to cause environmental problems including the forming of void pits and puddles around the mine site. Displacement of soil from below the surface in ore getting activities with a volume of 750 m3 can disrupt the structure and strength of the soil, causing collapse / subsidence which eventually produces voids. Improper environmental management can cause serious problems for the landscape and will cause derivative impacts such as social problems. Land cover design planning with backfilling method is a breakthrough to overcome existing voids. In principle, the material to be taken at the next mining point is transferred to the previously formed voids and so on. In addition, revegetation was carried out around the BHM mining location to increase the carrying capacity of the soil. The runoff of water to the surface continuously causes the surrounding land to become moist (saturated with water) so that the carrying capacity of the soil decreases. Mining activities use the BHM method at PT. TIMAH, Tbk is indeed a breakthrough in the conservation of tin ore reserves. However, environmental aspects also need to be considered. Proper environmental management can minimize environmental problems that occur. The holes with a diameter of 1.5 to 3 meters produced can be overcome with a back-filling system. Surface runoff is overcome by planning a planned mine drainage system by making a path / trench around the mining area Key Words: borehole mining, void, backfilling