Pressure Relief Mechanism of Directional Hydraulic Fracturing for Gob-Side Entry Retaining and Its Application

In order to make clear the pressure relief mechanism and application effect of directional hydraulic fracturing for gob-side entry retaining, the directional hydraulic fracturing was carried out by 400 m in haulage gateway remaining along the goaf in 50108 working face of Hejiata Coal Mine. Taking this as the engineering background, a mechanical model of roof cutting was established and the pressure relief mechanism was clarified. The theoretical research shows that it is the moments of gravity FG of the curved triangular roof plate at the face end, the pressure q of the overlying soft rock, and the transverse force TCB in the “voussoir beam” structure to the left endpoint of the triangular block, that is, M F G , M q , and M T CB , which determines the roadside supporting resistance. Hydraulic fracturing can reduce the lateral cantilever length of the basic roof, thus greatly reducing the values of M F G , M T CB , and M q , and significantly reduce the roadside supporting resistance. The field test shows that the directional hydraulic fracturing technology can effectively improve the stress environment of the face end and reduce the deformation of the roadway, and it has a good application effect on the gob-side entry retaining.

Three-dimensional imaging of the Mérida Andes, Venezuela

<p>The Mérida Andes are a 100 km wide mountain chain that extends from the Colombian/Venezuelan border to the Caribbean coast. To the north and south, the Mérida Andes are bound by hydrocarbon-rich sedimentary basins. Uplift of the mountains started in the late Miocene due to oblique convergence of the Caribbean and South American tectonic plates and the north-eastwards expulsion of the North Andean Block (NAB). This tectonic interaction fostered major strike-slip fault systems, with associated high seismicity, and the partitioning of the North Andean Block into smaller tectonic units, whose interaction accelerated the uplift of the Mérida Andes since the Plio-Pleistocene.</p><p>We present the three-dimensional inversion results of broadband magnetotelluric (MT) data from 72 sites gathered along a 240 km long profile across the central part of the MA, the Maracaibo (MB), and Barinas-Apure (BAB) foreland basins. Directionality and dimensionality analyses suggested 3D structures for the MA section, with the induction vectors indicating off-profile structures, particularly at long periods. Since the distribution of sites predominantly along a single profile can have adverse effects on the outcome of the 3D inversion, we rigorously tested all model features for robustness and excluded artefacts.</p><p>One of the main findings is a deep connection (> 10km) between the most prominent faults of the MA, the Valera and Boconó fault systems, with a deep off-profile conductor to the east of our profile. We interpret this conductive structure as a detachment surface of the Trujillo Block, which is part of the NAB and whose expulsion to the NE significantly influences the present-day geodynamic evolution of western Venezuela. A conductive zone under the Maracaibo Basin correlates spatially with the location of a Bouguer low. Both geophysical anomalies may be caused by a SE tilt of the Maracaibo Triangular Block under the Mérida Andes, bound by the north-western thrust system which could reach depths of 30 km.</p>

POTENSI PENGEMBANGAN BLOK SEGITIGA TUNJUNGAN SEBAGAI BAGIAN DARI PEMBENTUK CITRA KOTA

Title: Potential Development of Tunjungan Triangle Blocks As Part of Image of The CityMaker Good urban space is created from a good urban planning also. In the planning phase of the city, it is simulated how a good city consists of well synchronized urban components. Tunjungan, as one of the important formers of Surabaya character, is the most dynamic developed block. The gap between good planning and real condition, was become larger due to partially development. The diversity of land ownership, the capabilities of each developer and so on, are some of the causes. Yet the success of an urban architectureis affected by the ability of spatial planning and city planning collectively.Integrated development involving all aspects of urban space constituency is something that is expected to happen. This study attempted to read the conditions of the triangular block of Tunjungan from urban planning theory perspectives, then reflected on the real conditions in the field. The goal is to get a recommendation based on the development potential of urban elements that will strengthen the identity of the city of Surabaya itself.

Composable, Scalable Solvers on Staggered Grids

<p>Scalable preconditioners for saddle point problems are essential to the solution of problems in geodynamics and beyond. Recent years have produced a wealth of research into efficient solvers for finite element methods.  These solvers are also effective, however, for orthogonal-grid finite volume discretizations of saddle point problems, also know as "staggered grid" or "marker and cell (MAC)" methods. Perhaps, ironically, due to the highly-structured nature of these discretizations, the use of advanced solvers is stymied due to the lack of a uniform topological abstraction, which is required for most scalable solvers, such as geometric multigrid.  We present new software to allow experimentation with and composition of these advanced solvers.  We focus on variable-viscosity Stokes problems with discontinuous coefficient jumps.  In particular, we attempt to demonstrate how the important know robust preconditioners may be employed, and how new variants may be experimented with.  Important solvers are compositions of block factorizations and multigrid cycles.  We demonstrate as many of these as possible, including triangular block preconditioners with nested multigrid solves, and monolithic multigrid solves with cellwise (Vanka) or field-based (Distributed Gauss-Seidel, Braess-Sarazin) smoothers.  Implementations are provided as part of the PETSc library, using the new DMStag component, and examples from the StagBL library are also shown where appropriate.  These tools are intended to help break down the barrier between cutting-edge research into advanced solvers (which is only becoming more complex, as multi-phase problems are further explored) and practical usage in geophysical research and production codes.</p>

CFD Analysis on the Heat Transfer and Fluid Flow of Solar Air Heater having Transverse Triangular Block at the Bottom of Air Duct

In this study, a two-dimensional CFD (computational fluid dynamics) analysis was performed to investigate the heat-transfer and fluid-friction characteristics in a solar air heater having a transverse triangular block at the bottom of the air duct. The Reynolds number, block height (e), pitch (P), and length (l) were chosen as design parameters. The results are validated by comparing the Nusselt number predicted by simulation with available experimental results. Renormalization-group (RNG) k - ε model with enhanced wall-treatment was selected as the most appropriate turbulence model. From the results, it was found that the presence of a transverse triangular block produces a higher Nusselt number than that of smooth air duct. The enhancement in Nusselt number varied from 1.19 to 3.37, according to the geometric conditions investigated. However, the use of transverse triangular block also results in significantly higher friction losses. The thermohydraulic performance (THPP) was also estimated and has a maximum value of 1.001 for height (e) of 20 mm, length (l) of 120 mm, and pitch (P) of 150 mm, at Reynolds number of 8000. Furthermore, in the present study, correlations of the Nusselt number and friction factor were developed as a function of geometrical conditions of the transverse triangular block and Reynolds number, which can be used to predict the value of Nusselt number and friction factor with the absolute percentage deviations of 3.29% and 7.92%, respectively.

Analytical Model of Wellbore Stability of Fractured Coal Seam Considering the Effect of Cleat Filler and Analysis of Influencing Factors

Currently, coal borehole collapses frequently occur during drilling. Considering that the coal near to the wellbore is cut into blocks, and the cleat filler of the coal influences the stress distribution near the wellbore, a new theoretical solution of a near-wellbore Stress Field in coal bed wells is established. In addition, according to the limit equilibrium theory and the E.MG-C criterion, the limit sliding formula of the quadrilateral and triangular block is deduced, and the slipping direction of the blocks is further judged. Finally, the wellbore stability model of the coal seam is established. The accuracy of the theoretical model is verified through a numerical method by using the PFC software. Based upon this wellbore stability theoretical model of coal, many cleat affecting factors such as cleat spacing, cleat length, cleat angle and the cleat geometric position, are studied, and the results show that a quadrilateral block slides off more easily than a triangular block under the same boundary condition; the bigger the cleat spacing and cleat length are, the lower is the risk that blocks slide off, and increasing the cleat angle could cause blocks to slide off easily. Under the same boundary condition, whether blocks slide off or not is closely related to the well round angle.