The Effect of Selected Factors on Floor Upheaval in Roadways—In Situ Testing

Abstract

The phenomenon of the floor upheaval occurs in virtually every type of rock mass and at every depth, accompanying the process of excavation of tunnels and headings. Despite its inconvenience, it is rarely studied because of the complexity of the process and the multiplicity of the factors causing deformations in floor rocks. To quantify the effect of the selected factors on floor upheaval, this article presents an analysis of results of in situ measurements carried out in three coal mine roadways at 15 measuring stations. These measurements were taken over varying periods of time, between 129 and 758 days. Groundwater and fault zones intersecting the excavations were considered as the key factors that affect floor upheavals. Therefore, the measurement bases were located at local faults and sites of water inflow. To compare the results, the stations were also located where the rock mass was not exposed to any factors other than stresses resulting from the depth of the excavation. The excavations were driven in various rocks and were located at different depths from 750 to 1010 m. The analyses of the study results show that the floor upheaval always depends on time and can be described in polynomial form: ufl = a·t2 + b·t + c or by a power function: ufl = a·tb. However, the further regression analyses show that roadway’s floor upheaval can be expressed by a complex form using the key parameters determining the phenomena. In the absence of an impact of geological factors on the stability of the excavation, the floor upheaval depends on floor rocks compressive strength σc and Young’s modulus E: ln(ufl)=a·ln(tσc)−bE−c; in the case of rock mass condition affected by water depends on the rock compressive strength reduction after submerging rock in water σcs 6h: ufl=a·t0.5−bσcs 6hσc+c and in the case of fault depends on the fault’s throw f: ufl=a·t0.8+b·f1.2−c. Statistical analysis has shown that the matching of the models to the measurement data is high and amounts to r = 0.841–0.895. Hence, in general, the analysis shows that the floor upheaval in underground excavation in any geological conditions may grow indefinitely.

Technical and technological aspects of the coal mine closure based on the geomechanical component assessment

“…The dependences of the increase in the convergence of the roof and bottom U r,b (t), as well as the sides U s (t) in time t is determined by Formulas ( 9) and (10), and the value of the residual cross-sectional area constantly decreases and is calculated by the same Expressions (5) and ( 6) by substituting values U r,b (t) and U s (t) in them for the corresponding period t of mine working maintenance: ( It is worth mentioning another rock mass behavior and convergence tendency if the floor rocks are waterlogged, what was investigated in the paper [51].…”

Numerical Studies of Floor Heave Control in Deep Mining Roadways with Soft Rocks by the Rock Bolts Reinforcement Technology

“…Te results of observation are in good agreement with measurements in situ. Te foor heave on stations, which were built in roadways D-2 and F-33b, was monitored over two years [30]. In roadway D-2, the maximum value of upheaval after almost 800 days of monitoring was 0.54 m, and in roadway F-33b 0.6 m. Te average value of foor heave on monitoring stations in the conveyor roadway of 5 longwalls of 3 m seam was 0.7 m [31].…”

Numerical Modeling of Controlling a Floor Heave of Coal Mine Roadways with a Method of Reinforcing in Wet Soft Rock

“…Małkowski et al [9] studied the multiplicity of the factors causing floor heave. To quantify the effect of the different factors on floor upheaval, an analysis of results of in situ measurements carried out in three coal mine roadways at 15 measuring stations was presented.…”