Determining the parameters of a natural arch while forming support load of a horizontal roadways

Abstract

Purpose. Development of a semiempirical method to identify rock pressure on the support of underground mine roadways as well as substantiation of its efficient use area taking into consideration the depth of the mine roadway, its geometry, and hardness of enclosing rocks. Methodology. Theoretical studies on geomechanical processes taking place in the neighbourhood of roadways using analytical mathematical methods as well as numerical ones. Analysis of the research results and their generalization are involved. Findings. Methods to identify load (i.e. rock pressure) on the supporting structures have been developed. The methods are based upon the proposed calculation technique for the rock stability coefficient at the boundary of contact between a collapsing arch of the rock (i.e. fall arch) and undisturbed rock mass, i.e. at the boundary of elastic share of peripheral rock mass, and non-elastic one. A stability coefficient has been proposed in the form of projection on vertical axis of forces holding the rock mass, limited by a fall arch, to projection of shear forces. Originality. For the first time, an analytical and empirical method to identify natural arch over horizontal and vertical mine roadways has been proposed involving their depth, geometry, parameters of rock strength, and its gravity. The abovementioned is the key distinction of the proposed method from the known semiempirical technique by M.M. Protodyakonov to determine natural arch as well as support load. Practical value. The findings make it possible to predict stability of horizontal mine roadways using mathematical methods. In this context, the depth, geometry, and hardness of enclosing rocks are taken into consideration.

Assessing the stability of underground workings in urban infrastructure

“…A promising approach for solving the problems posed in this study is the approach proposed by the authors of [28], which was used to determine the load on the support of horizontal underground workings.…”

“…In other words, from equality (3) it follows that from all possible values of the lifting boom of the arch of natural equilibrium, one should choose such at which the ratio of the forces holding the rock and the forces that shift it will be minimal. Despite the obvious advantages compared to the classical Protodyakonov method and many of its modifications, the algorithm proposed by the authors of [28] for calculating the parameters of underground mine workings still has certain drawbacks:…”

“…From a physical point of view, the lift boom of a natural equilibrium arch calculated using ( 18) is Shashenko strength criterion [5,20,28], multiplied by half the span of the arch and divided by the specific adhesion of the rock, and the stability coefficient calculated using (19) is the same criterion multiplied by two and divided by the value of rock pressure at the level of the mine roof. The table compares the results obtained with the data reported in [28] (table 1).…”

“…The results obtained by the authors of work [28] Calculation results using ratios ( 18), (19), and ( 21) : fis the height of the rise of the arch of natural equilibrium above the working; st Kstability coefficient; Qload on the support. During a numerical experiment using relations (20) for workings located at depths of 50, 100, 500, and 1000 meters with a span width of the values of the stability coefficient of the natural arch and the arch lift boom were calculated.…”

“…The data used by the authors of [28] were taken as initial data: specific gravity of the rock kN/m 3 ; rock compressive strength MPa; rock tensile strength MPa. To move from the strength characteristics and adopted in (19) and (20) to the uniaxial compressive and uniaxial tensile strengths, the well-known relationships were used [28,30]:…”