When building the mine workings in the underground conditions the initial stress-deformed state of the rocks around the workings changes with changing the value and sign. At the same time the selection of the appropriate support becomes more complicated. With the development of computer science and technology the numerical method has been widely used in solving the geotechnical problems. The numerical method for Phase 2 program is used to calculate internal forces when selecting the mine working supports in Kuangnin Province, Vietnam.

To solve the geomechanical problem the following initial data were adopted: the depth of the mine working deposit is 100 m, the width of mine workings is 5 m, and the height is 4.5 m. The following options are considered: a) B/D = 5/2; b) B/D = 5/4; c) B/D = 5/8; d) B/D = 5/16, the mine working is in the center of the rock thickness; e) B/D = 5/16, the mine working is at the top of the rock thickness; e) B/D = 5/16, the mine working is at the bottom of the rock thickness (where B is the width of the mine workings, D is the thickness of the rocks).

The results of the study showed that the geological properties of rocks, the angle of gradient and the thickness of the rocks, and also the place of location of the workings significantly effect the stress-deformed state of the rocks around the workings. The values of the bending moments in the support are changing at different thicknesses of the rocks, the diagrams of the internal forces are not symmetrical.

Maximum values of bending moments in the support can be reduced to 80 % when using adjustable elements of the metal support. When locating workings in the isotropic rock massif and at the ratio of the width of the mine working and the thickness of the rock massif 5/8 and 5/16, the stress-deformed state is symmetrical, and the best results are shown in the theory of rock pressure of Protodyakonov and P.M. Tsimbarevich. If the ratio of the width of the mine working to the thickness of the rock mass is less than 5/16, in practice the theory of V.T. Glushko suits most of all.

**Tran Tuan Minh, Lecturer
Xuan Nam Bui, Dr. Sci. (Eng.), Prof., Deputy Principal
Kuang Khieu Chan, Cand. Sci. (Eng.), Lecturer
Hanoi University of Mining and Geology, Hanoi, Vietnam
Nguyen Quang Huy, Research Associate
Transport Scientific and Technological Institute, Hanoi, Vietnam
V.I. Golik, Dr. Sci. (Eng.), Prof., v.i.golik@mail.ru
FGBOU VPO «NCSTU», Vladikavkaz, Russia**

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