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

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.

Evaluating the Impact of Blast-Induced Damage on the Rock Load Supported by Liner in Construction of a Deep Shaft: A Case Study of Ventilation Shaft of Micangshan Road Tunnel Project

The rock load acting on the lining of an underground excavation is influenced by multiple factors, including rock type, rock mass condition, depth, and construction method. This study focuses on quantifying the magnitude and distribution of the radial loads on the lining of a deep shaft constructed in hard rock by the so-called short-step method. The blasting-induced damage zone (BDZ) around the shaft was characterized using ultrasonic testing and incorporated into the convergence-confinement method (CCM) and 3D numerical analyses to assess the impact of BDZ on rock loading against the liner. The results show that excavation blasting of shafts is an important controlling factor for the degradation of the rock mass, while the orientation and magnitude of the principal stress had a minimal influence on the distribution of blast-induced damage. The analysis shows that increasing the depth of blast damage in the walls can increase the loads acting on the lining, and the shear loads acting on the liner could be significant for shafts sunk by the short-step method in an area with anisotropic in situ stresses.

Investigation of geomechanical parameters of rock mass condition of Magnezitovaya mine**

Mining is a sphere of human activity connected with extraction of minerals from Earth’s interior in conditions of alternating change of the sizes of Earth accompanied by change of the stress-deformed state (SDS) of the rock mass, resulting in sudden destructions of rock structures and earthquakes, with considerable human victims. The results of long-term geodeformation monitoring of natural stresses at Ural mines conducted by the Laboratory of geodynamics and mining pressure of the Ural Branch of Russian Academy of Sciences over the past 20 years have allowed us to offer new, more modern structure of the natural stress field with a reference to their changes in time. The Laboratory of geodynamics and mining pressure of the Institute of Geodynamics of the Ural Branch of Russian Academy of Sciences has created the geodeformation field test site at the Magnezitovaya mine [1] This field test site allows to quickly track the changes in the stress state by deformation methods and to react in time to the changes in the stress state of the rock mass. And by applying the measures to control the state of the rock mass, the company’s personnel ensure the safety of room work at the deposit. This allows to minimize the occurrence of the rock pressure in static and dynamic forms, and thus to ensure the safety of people working in underground conditions.

Experimental Study on Comprehensive Real-Time Methods to Determine Geological Condition of Rock Mass along the Boreholes while Drilling in Underground Coal Mines

The geological condition is essential for mining design and disaster control in underground coal mines. The present research focuses on the real-time assessment method on rock mass condition during drilling boreholes. In situ comprehensive experiments were carried out using three methods, which are measurement while drilling (MWD) system, vibration measurement while drilling (VMWD) system, and borehole camera detecting system. In the MWD system, the operating parameters of the drilling machine were recorded, and a dimensionless index Id based on the collected parameters was adopted to assess the geological condition along the borehole. The results show that the state of rock mass can be well classified using the MWD system for both the cross-layer and in-seam boreholes. In the VMWD system, the vibration of the drilling bit was monitored, and the signal was analyzed in both time domain and frequency domain. The results indicate that the rock mass condition can be quantitatively evaluated using the mean square value of the signal and qualitatively estimated using the energy of the spectrum. In the borehole camera system, the photos of the rock mass along the borehole could be well captured, and the identified rock mass condition was used to verify the results of the MWD and VMWD systems. Comprehensive compassion between the results from the three systems shows that all the methods can give valuable information for the geological condition, and the outcomes of the different methods are generally comparable. For practical purposes, the advantages of the involved three detecting systems are discussed.

Analisis Pengaruh Getaran Peledakan Terhadap Kestabilan Lereng Pada Tambang Batubara Pit Roto Selatan Site Kideco, Kecamatan Batu Sopang, Kabupaten Paser, Provinsi Kalimantan Timur

In PT. BUMA site, there are some landslide which affected by blasting activity. Blasting activity iscarried out to destroy overburden material. The purpose of this research is to know the type oflandslide, the coefficient value of vibration decay from Peak Particle Acceleration (PPA), rock masscondition constant value from Peak Particle Acceleration (PPA), the Peak Particle Acceleration (PPA)value and the maximum acceleration (amax) which is at a point of safe in South Roto Pit. The researchmethods which used are the window mapping method in several sections at South Roto Pit.Description of rock mass that includes type of rock, rock strength, degree of weathering, block shape,type and shape of discontinuity, discontinuity filler and roughness level of discontinuity. ThisDescription of rock mass use Geological Strength Index (GSI) classification as a parameter to knowthe mechanical properties of rock mass (cohesion and internal shear angle). The research area has atype of toppling failure with eastward avalanche. The value of coefficient of vibration decay from PPA(k) is 44,66. The rock mass condition constant (α) is 1,802. The safe value of PPA highwall slopesarea of B STA 1 value is 0,184 g and the maximum acceleration (amax) value is 0,12 g. Highwall slopesarea B STA 2 with PPA value is 0,0769 g and maximum acceleration (amax) value is 0,05 g. Highwallslopes area C5 STA 3 with PPA value is 0,153 g and the maximum acceleration (amax) value is 0,1 g.Highwall slopes area C5 STA 4 with PPA value is 0,0307 g and the maximum acceleration (amax) valueis 0,02 g. Overall slopes area with PPA value is 0,0307 g and maximum acceleration (amax) value is0,02 g.

Study on Dynamic Disaster in Steeply Deep Rock Mass Condition in Urumchi Coalfield

The possible mining seismicity (MS) and its prediction are important for safety and recovery optimization of mining in steep-heavy-thick rock mass condition. The stress-lever-rotation-effect (SLRE) model of fault-like mobilization was proposed preliminarily. Some innovation monitoring technique approaches for mining seismicity assessment were successfully fulfilled at Wudong Mine of Urumchi Coalfield, China. The characteristics on acoustic-seismic-wave index indicated the spatial-temporal-strength and stress redistribution of steeply deeper-heavy thick coal and rock masses. Applications in field investigations showed that the innovation monitoring (in time and space) of these instruments could provide important information about the performance of mining disturbed structures (heading and steep pillar) during caving of competent overlying roof strata. The prediction and evaluation for mining seismicity were applicable and valid. Operating practice showed that mining efficiency was raised and conspicuous economic benefit was obtained. This approach provides essential data for assessing mining seismicity, coal burst, dynamic hazard prevention, and deep mining potential.