Floor heaving is a phenomenon that occurs in almost all mining roadways and tunnels. It can restrain the advance of the heading face or cause serious problems during roadway use. The highest levels of floor uplifting are observed in coal mines, which can reduce the output or even stop it altogether. The floor heaving intensity depends on the rock type, the stress in the rock mass, and rocks’ mechanical properties. Floor deformation develops when the secondary state of stress is formed around the working, and it is much higher and more dynamic in the case of waterlogged rocks. The presence of water increases the floor’s propensity to heave, especially clay rocks, such as claystones or mudstones, if they include water-absorbed minerals. In this paper, we present a new modeling methodology for roadway floor heave. The modeling covers a dry floor condition in which the parameters of the Hoek-Brown failure criterion are gradually lowered over time, and a waterlogged floor condition, in which the strength and strain parameters of the rocks are gradually reduced in line with their progressive saturation. In the second case, the claystone floor’s geomechanical parameters were investigated, and the rocks were subjected to water for up to 24 h. The results of the numerical simulation were compared with the in situ measurements of convergence and floor heave in the same coal mines from which the rock samples were collected. The consistency between the numerical simulations and the underground measurements reached 90–99%.

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: u_fl = a·t² + b·t + c or by a power function: u_fl = a·t^b. 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 σ_c and Young’s modulus E: $ln(u_{fl})=a·ln\left(\frac{t}{{\sigma }_c}\right)-\frac{b}{E}-c$; in the case of rock mass condition affected by water depends on the rock compressive strength reduction after submerging rock in water σ_{cs 6h}: $u_{fl}=a·t^{0.5}-b\frac{{\sigma }_{cs 6h}}{{\sigma }_c}+c$ and in the case of fault depends on the fault’s throw f: $u_{fl}=a·t^{0.8}+b·f^{1.2}-c$. 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.

The small throw fault zones cause serious problems for mining engineers. The knowledge about the range of fractured zone around the roadway and about roadway’s contour deformations helps a lot with the right support design or its reinforcement. The paper presents the results of numerical analysis of the effect of a small throw fault zone on the convergence of the mining roadway and the extent of the fracturing induced around the roadway. The computations were performed on a dozen physical models featuring various parameters of rock mass and support for the purpose to select the settings that reflects most suitably the behavior of tectonically disturbed and undisturbed rocks around the roadway. Finally, the results of the calculations were verified by comparing them with in situ convergence measurements carried out in the maingate D-2 in the “Borynia-Zofiówka-Jastrzębie” coal mine. Based on the results of measurements it may be concluded that the rock mass displacements around a roadway section within a fault zone during a year were four times in average greater than in the section tectonically unaffected. The results of numerical calculations show that extent of the yielding zone in the roof reaches two times the throw of the fault, in the floor 3 times the throw, and horizontally approx. 1.5 to 1.8 times the width of modelled fault zone. Only a few elasto-plastic models or models with joints between the rock beds can be recommended for predicting the performance of a roadway which is within a fault zone. It is possible, using these models, to design the roadway support of sufficient load bearing capacity at the tectonically disturbed section.

The article presents the e valuation o f h ow suitable waste from the production of aggregates in quarries could be in earthwork using the example of screen-outs from Krosno sandstone. The waste, called screen-out, is characterised by an uncontrolled content of dust and clay fractions. Screen-outs have a relatively low bearing ratio (CBR not exceeding 20%) and a tendency to heave due to frost (SE <35). To check whether the geotechnical properties can be improved, mixtures with 2%, 5%, and 8% binders, such as lime, fly ash, and two road binders with lime, fly ash, and cement were prepared. The analysis was based on the results of the CBR and compressive strength tests. The use of mineral binders caused the value of the immediate CBR to increase compared to the screen-out itself from a dozen to as much as 50%. For a binder containing 20% Portland clinker, the CBR was about 60% after 4 days of saturation, while for a binder containing up to 50% Portland clinker, it was over 200%. The value of compressive strength after 28 days of maturing ranged from about 100 kPa to 1 MPa for all mixes tested. The lowest values were obtained for screen-outs activated with fly ash, and the highest for road binder with cement content of up to 50%.

Reliable determination of Mode I fracture toughness is essential for evaluating crack initiation and propagation in rock engineering applications such as hydraulic fracturing, underground energy storage, geothermal energy extraction, and CO₂ sequestration. The Short Rod (SR) test is the only ISRM-suggested direct method for determining Mode I rock fracture toughness, but its wider application is limited by a relatively complex loading system. This study proposes a simple shear-to-tensile (ST) fixture for conducting SR tests using a conventional direct shear apparatus. The CNC-cut steel fixture converts the applied shear load into direct tensile loading on the specimen. Tests on gypsum produced symmetric fracture paths and consistent load–displacement responses, with a mean $K_{IC}$ of 0.287 ± 0.008 MPa√m. SCB tests on the same material yielded 0.288 ± 0.020 MPa√m, showing close agreement between the two methods. DEM simulation further captured fracture initiation at the chevron-notch tip and progressive crack propagation through the specimen ligament. The results demonstrate the feasibility of the proposed configuration as a proof of concept for direct SR testing, with future studies aimed at extending its validation to stronger rock materials.