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2 2016

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Evaluation of pre-jamming indication parameter during blind backfilling technique

Panda S., Pal S. K., Murthy P. V. S. N.

Journal of Sustainable Mining

2016

Vol. 15, iss. 3

100--107

Hydraulic blind backfilling is used to reduce subsidence problems above old underground water-logged coal mines. This paper describes experimental research on a fully transparent model of a straight underground mine gallery. An automatic data acquisition systemwas installed in the model to continuously record the sand and water flowrates along with the inlet pressure of the slurry near the model's inlet. Pressure signature graphs and pressure loss curves with bed advancement under different flow conditions are examined. Pressure signature analyses for various flowrates and sand slurry concentrations are conducted to evaluate a pre-jamming indication parameter, which could be used to indicate the arrival of the final stage of filling.

Analysis of hydrodynamic pressure fields of motorboats and pontoons in shallow water

Bielański J.

Hydroacoustics

2016

Vol. 19

9--16

The article presents the results of calculations of the pressure fields generated by a motorboat at the bottom of a shallow sea. Calculations were made using the boundary elements method (BEM), arranged on the surface of the boat and the bottom of the sea. This method is described in [3], and applied on a free surface linearized boundary condition. Results for four different lengths of motorboats, from 2.85 m to 9.5 m, sea depth from 1 m to 10 m, are presented in the form of a surface, approximated by a polynomial function whose coefficients are given. These functional relations allow one to calculate the maximum and minimum hydrodynamic pressure generated by the motor boat length, in the range as above, and the sea depth to about 10 m when flying at speeds of up to 20 m / s. Given functional dependencies can be used, in the field of security and anti-terrorism defences, and can serve to identify the type and size of speedboats, up to about 10 meters and a displacement of about 8 tons.