Jan Nemcik

• BE, ME, PhD
• Fellow at University of Wollongong

Fissured coal mass under triaxial unloading condition exhibits higher burst potential than the triaxial loading condition, which poses challenge to safety and productivity of resources extraction and underground space utilization. To comprehensively understand the mechanism of unloading-induced burst during excavation process, this study investigat...

Accurate knowledge of the stress-strain state in rock mass is absolutely critical to optimise support design. Therefore, the rock mass stresses are often measured for reasons of safety and efficiency in underground mining. Investigation of the rock mass stress is usually carried out by interpretation of the rock mass deformation processes. These ca...

Over the past few decades, the rapid development of efficient mathematical algorithms and the increasing availability of powerful computers have made it possible to develop realistic constitutive models. With the development of highly sophisticated constitutive models, the Finite Element Method (FEM) has become an invaluable tool for predicting ult...

As a typical roof-supporting system of tunnels, Cable bolts are subjected to static and dynamic loading conditions caused by ground movements and mining activities. As mining goes deeper, the chance of undetermined ground stress concentrations increases and subsequently, the probability of sudden unexpected failures such as rock bursts increases. M...

A variety of coal room and pillar mining methods have been efficiently practiced at depths of up to 500 m with least strata mechanics issues. However, for the first time, this method was trialled at depths of 850–900 m in CSM mine of Czech Republic. The rhomboid-shaped coal pillars with acute corners of 70°, surrounded with 5.2 m wide and 3.5–4.5 m...

Three stages of nitrogen (N2) injection enhanced gas drainage through underground in-seam boreholes were carried out in a coal mine located in the southern Sydney basin. Due to the high CO2 content and low permeability, hard-to-drain coals were encountered during the excavation process in this coal mine. Two parallel in-seam boreholes (the length o...

This paper focuses on the experimental study of shear testing of 15.2 mm, 25 t capacity seven wire cables at zero, 30° and 45° angles using two different shear testing facilities at the University of Wollongong (UOW) and the University of Southern Queensland (USQ) in Toowoomba. A circular double-shear rig MK-IV was used for testing cable perpendicu...

The influence of roughness, aperture and asperity irregularity on fluid flow regimes in rough rock fractures was investigated by performing coupled triaxial water flow tests and fluid dynamic computation. Ten sets of fabricated curved wedges were developed to obtain different fracture surface roughness by splitting under compression. Three fluid fl...

Numerical modelling has been widely used in the underground excavation design, where the in situ stress state plays a crucial role in the stability analysis. However, determination of an exact stress state for a specific geological region remains uncertain due to the complicated tectonic nature and measurement limitations. The stability is thus bet...

Current mining activities of the OKD mines are primarily focused on coal seams within the Karvina Formation in the Karvina sub-basin. A considerable amount of coal reserves are situated in protection pillars that lie under built-up areas. The longwall mining method is not applicable in these areas because significant deformation of the surface is n...

CO2 geo-sequestration in unminable coal seams is one promising method to mitigate greenhouse gas emissions and would be a means of cleaner production. At the same time, the injected CO2 can enhance coalbed methane recovery and offsets the economic cost for CO2 transportation and injection. However, this technology is still at its primary stage and...

This case study presents the verification of two surface subsidence prediction models for longwall mining at depths greater than 400 m. The surface subsidence points were surveyed and compared for both models. The first model uses empirical calculations to predict the surface subsidence. This method is reliable for predicting surface subsidence at...

This study investigates a glass-reinforced polymeric thin spray-on liner and its ability to reinforce substrate surface in underground excavations by the use of laboratory testing. Twenty-three hydrostone beams uncoated and coated with 5 mm thick fibre-reinforced polymer (FRP) coating were subjected to four-point bending tests to study their streng...

Since time immemorial, mining has been an inseparable part of human history. Generations of our ancestors drove and excavated mining workings to enable them find and exploit useful minerals from the ground. Shafts, drifts and corridors created in this way, however, had always limited service life; their significance and purpose mostly expired as so...

Presented here are the details of the seismic events that occurred at longwall 11 located at the CSM mine in the Ostrava coal region, Czech Republic. This longwall was excavated in a very complex area located within the shaft protective pillar and adjacent to the 50 m wide and steeply inclined fault zone at a depth of 850 m. In addition, 10 longwal...

Use of the system of dual-use of gateroads represents a significant change in the hitherto preferred method of addressing of mining works development. The entire system is based on the principle of reuse of one gateroad during the process of mining of the pair of neighbouring mining panels. The basic condition for its possible application is the st...

ABSTRACT: Room and Pillar method was used to develop shaft protection pillar, below 850 m from the surface at CSM mine of Upper Silesian Coal Basin of Czech Republic. First panel V was developed on rhomboid shaped pillars of different sizes by driving roadway of 3.5-4.5 m in height and 5.2 m in width. Field study was conducted using different geo-t...

In this study, laboratory tests using six-cycles of nitrogen (N2) injection were carried out to investigate nitrogen flushing effect on coal seam gas recovery. In each test, N2 was injected for 200 min into a coal sample saturated with carbon dioxide (CO2), in a triaxial-loaded cell. Nitrogen injection was paused for about 20 h to allow gas desorpt...

To improve ground skin support in highly stressed underground mines, new types of thin spray-on liners (TSL) are currently under development to replace steel mesh. To test these products, three different types of support material were tested for their ability to resist buckling failure, a mode of failure typically experienced by strata in highly st...

Cable shear behavior in reinforcing rock discontinuities involves both the axial shear behaviour along the cable-grout interface and the local lateral shear behaviour of the cable deflecting section. This is a complex condition which is difficult to be solved in a theoretical manner. Pile structural elements in Flac3D were used here to investigate...

A set of single shear tests on fully encapsulated cable bolts was carried out using a newly developed and integrated Megabolt single shear apparatus. The instrument is designed to determine the pure shear strength of cable bolts where there is no contact between the host body faces during the shearing process. Eight different types of cable bolt we...

There is an increasing need to determine accurately the strength properties of tendons for an effective ground control on mines and underground structures as well as on modelling simulations. The strength properties of cables, used as cable bolts, have been evaluated mainly by their ultimate tensile strength, as this kind of test can be carried out...

In the extra-thick coal seams and multi-layered hard roofs, the longwall hydraulic support yielding, coal face spalling, strong deformations of goaf-side entry, and severe ground pressure dynamic events typically occur at the longwall top coal caving longwall faces. Based on the Key strata theory an overburden caving model is proposed here to predi...

The performance of pre-gas drainage in low permeable seams especially in CO2 abundant coal seams is not satisfactory. Due to the high affinity of coal to CO2, much lead time is needed for gas drainage boreholes to reduce the coal seam gas content below the threshold limit value (TLV), thus meeting the demand of the scheduled mining activities. In t...

The trial operation of the room and pillar method has been implemented at the shaft protective pillar of CSM coal mine, Czech Republic. Mining depth of the room and pillar trial ranged from 700 to 900 metres, being perhaps the deepest room and pillar coal mining in the world. An extensive monitoring system was implemented to measure the load profil...

For several cable bolt technology has been used for ground reinforcement in civil, mining and other construction projects. The strength properties of these cables, used as cable bolts, have been evaluated mainly by their ultimate tensile strength as this kind of test could be carried out in the field as well as in the laboratory. Only recently ther...

Accurate knowledge of the stress-strain state of rock mass, not only in their vicinity but also in the wide surroundings of mine workings, is absolutely critical for precise support designing. Investigation of the rock stress is usually carried out by interpretation of the rock mass deformation processes, which can be relatively precisely observed...

Fracture propagation in brittle rock is very fast and highly dynamic. Typically this process consists of fracture initiation, propagation and termination. Growth of micro-fractures is conceptually and numerically well established, however, current practices to model fracture propagation in rock employs slow evolving static regimes that do not repre...

A new series of double shear tests were carried out using a newly modified double shear apparatus which prevented contacts between concrete block surfaces during shearing. 13 double shear tests were carried out using 21mm diameter 19 (9 × 9 × 1) seal construction wire strand cable (also called Superstrand cable), Plain SUMO, Indented SUMO, Spiral M...

Monitoring of pillar and roadway deformations is one of the most important issues in geotechnical engineering and mining practice. The use of 3D laser technology is ideal to monitor strata displacements in underground excavations enabling complex spatial data capture of the entire space around monitored pillars including all roof and rib deformatio...

Seam gas pre-drainage, is widely used as an effective method to control gas and coal outburst in underground coal mines. However, in CO 2 abundant low permeable seams, this technology seems to be less efficient due to the CO 2 sorption characteristics and the lower safe mining threshold limit for CO 2 applied in many outburst risk management plans....

A newly developed double shear apparatus without contact between concrete blocks was developed to conduct a series of double shear tests. This new double shear apparatus is capable of determining the pure shear strength of pre-tensioned fully grouted cable bolt without friction between sheared concrete blocks. Five different types of cable bolt, wi...

Carbon dioxide (CO2) enhanced coalbed methane (ECBM) is an effective method to improve methane (CH4) production and this technology has already been used to increase gas production in several field trials worldwide. One major problem is the injection drop in the later period due to permeability decrease caused by coal matrix swelling induced by CO2...

The bond characteristics of fully grouted rockbolts installed in steel tubes were investigated by bolt push tests. Steel tubes were inserted in a mine roadway roof to represent the confinement of rock boreholes. Rockbolts were installed in tubes using the installation technique of Australian underground mines. These tubes, with rockbolts inside, we...

The prediction of gas emissions arising from underground coal mining has been the subject of extensive research for several decades, however calculation techniques remain empirically based and are hence limited to the origin of calculation in both application and resolution. Quantification and management of risk associated with sudden gas release d...

Discontinuous deformation analysis (DDA) has been widely applied in analyzing various rock engineering problems. As the joint strength play a vital role in the stability of jointed rock mass, this paper makes an attempt to implement the Barton-Bandis rock joint model into the DDA code to replace the original Mohr-Coulomb joint model. The developed...

Sixteen single shear tests were carried out on eight geometric cable variations provided for testing from Australian suppliers – Jennmar, Megabolt and Minova. Each test was subjected to varying pre-tension values of zero and 15 tonnes, exploring the effect of plain, spiral, bulbed, indented and a combination of plain and indented wire strands. The...

A new series of double shear tests were carried out using a newly modified double shear apparatus which prevented contacts between concrete block surfaces during shearing. 13 double shear tests were carried out using 21 mm diameter 19 (9x9x1) seal construction wire strand cable (also called Superstrand cable), Plain SUMO, Indented SUMO, Spiral MW9...

The strain gauge probes of different construction are typically used for determination of stress state rock mass. The modified overcoring method known as the Compact Conical ended Borehole Overcoring method (CCBO) for stress state determination in rock mass was designed in Institute of Geonics of the CAS (IGN) in cooperation with Kumamoto Universit...

The application of cable bolts for ground support is increasing in underground coal mines worldwide. Currently, two methods of evaluating the performance of the cable bolt are favoured: the short encapsulation pull test, and the shear test. The former method can be used both in the laboratory and in the field while the latter can be undertaken main...

Bolt installation quality is influenced by various factors, some are well known and others are less recognised. A programme of field and laboratory studies was undertaken to examine various factors of relevance to the load transfer mechanism between the bolt, resin and rock to ensure test methods truly represent field performance. Short encapsulati...

This paper experimentally compares the shear behavior of fiber glass (FG) bolt, rock bolt (steel rebar bolt) and cable bolt for the bolt contribution to bolted concrete surface shear strength, and bolt failure mode. Two double shear apparatuses of different size were used for the study. The tensile strength, the shear strength and the deformation m...

Current mining activities of the OKD mines are primarily focused on coal seams within the Karvina Formation in the Karvina sub-basin. A considerable amount of coal reserves are situated in protection pillars that lie under built-up areas. The longwall mining method is not applicable in these areas because significant deformation of the surface is n...

A mathematical model which is able to determine the pure shear strength of cable bolt was introduced and calibrated for various conditions. The proposed equation is developed based on the Fourier series concept and a linear relationship between shear and normal forces generated during cable bolt shearing. The conventional double shearing instrument...

Although the room and pillar mining method is world-known and widely used, in terms of the Czech coal mines located in the Upper Silesian Coal Basin it is still in the testing phase. Unfavourable mining, geotechnical conditions at large depths and the ban by Czech mining authorities prevented this method from being used on rock bolt reinforcement w...

The purpose of this work is to highlight the importance of terrestrial laser scanning as an essential engineering design tool to evaluate the displacements and deformations of mine excavations at large depths. The 3D scanning results gave relevant information about displacements and deformations that occurred at the tested site and thereby helped t...

Coalburst (also known as coal bump) is a well known phenomenon in underground coal mines internationally, however, it was not recognised as a risk for Australian coal mines until the recent double fatality at Austar Coal Mine in the Hunter Valley in 2014. This paper reviews the international knowledge base from research and practice to provide Aust...

The load transfer mechanisms of cable bolts differ from normal rebar bolts. Cable bolts used in mines are basically steel strands with different constructions depending on the number of wires or elements and the way that these elements are laid. Tendon bolts (rebar and cable) are normally evaluated for strength and load transfer properties. The str...

Several mines operating in the Bulli seam of the Sydney Basin in NSW, Australia are experiencing difficulties in reducing gas content within the available drainage lead time in various sections of the coal deposit. Increased density of drainage boreholes has proven to be ineffective, particularly in sections of the coal seam rich in CO2. Plus with...

Current mining activities of the OKD mines are primarily oriented to coal seams within the Karvina Formation in Karvina SubBasin. A considerable amount of coal reserves are situated in protection pillars that lay under built-up areas. The longwall mining method is not applicable in these areas because significant deformation of the surface is not a...

An experimental investigation into the performance of two 22 mm diameter, 60 t tensile strength capacity Hilti cable bolts in shear was conducted using the double-shear testing apparatus at the laboratory of the School of Civil, Mining and Environmental Engineering, Faculty of Engineering and Information Sciences, University of Wollongong. The test...

In this study, numerical simulation was conducted to model the behavior of rockbolts with free-end slip in tension. A nonlinear bond-slip relationship was input to the numerical model to represent the interaction mechanism of the interface between rockbolt and grout. The results of the model were validated against laboratory tests. The numerical mo...

The strength properties of Secura Hollow Groutable Cable-bolts (HGC) were examined for tensile and shear failures. The 30 mm diameter, nine strand, cable bolt consisted of a mixture of five 7.5 mm plain and four 7.0 mm indented strands wrapped around a central 14 mm steel grouting hole to make a round cable with lay length of 500 mm with bulbs at 5...

The strength properties of Secura Hollow Groutable Cable-bolts (HGC) were examined for tensile and shear failures. The 30 mm diameter, nine strand, cable bolt consisted of a mixture of five 7.5 mm plain and four 7.0 mm indented strands wrapped around a central 14 mm steel grouting hole to make a round cable with lay length of 500 mm with bulbs at 5...

Cable bolting and rock/rebar bolting are the two main reinforcement techniques used in underground coal mines to maintain the stability of openings. Due to the structural features of cable strands, cables and solid bolts behave differently in reinforcing rock strata. Since the generation of a cable model is different in a numerical program, and esp...

Glass-Reinforced Polymer (GRP) bolts, commonly known as Fibre Glass (FG) dowels are increasingly applied for strata reinforcement in mines. The most popular dowels used in coal mines are the 22 mm diameter fully threaded type. A series of tests were undertaken to evaluate various strength properties of FG dowels. These include tensile failure tests...

Permeability is assessment of the ability of rock to transmit fluid flow through the rock body. It can be affected by rock structure due to the grain size, formation and the pressure or concentration gradient existing within and across it. Past studies focused on the relationship between permeability and axial stress on rock, and there has been lim...

Thin spray-on liners (TSLs) are attracting attention as effective rock support reinforcement in underground mines. They have the potential to increase roadway development rates and provide resistance at small rock surface displacements. To study the reinforcement provided by a TSL when applied onto a pillar surface, the support mechanism of TSL-coa...

Thin spray-on liners (TSLs) are attracting attention as effective rock support reinforcement in underground mines. They have the potential to increase roadway development rates and provide resistance at small rock surface displacements. To study the reinforcement provided by a TSL when applied onto a pillar surface, the support mechanism of TSL-coa...

A new approach was proposed to minimize the effect of normal stress induced by shrinkage on the shear-bond strength thereby improving the accuracy in assessing the shear-bond strength of TSL materials.

Glass-Reinforced Polymer (GRP) bolts, commonly known as Fibre Glass (FG) dowels and Fibre–Reinforced polymer (FRP) or plastic bolts or plastic dowels are increasingly applied for strata reinforcement in mines as well as in concrete reinforcement in civil engineering. The most popular dowels used in coal mines are the 22 mm diameter fully threaded t...

The direct shear test was adopted to investigate the shear behavior of thin spray-on liner (TSL) penetrated rock joints. The effects of surface roughness, penetrated thickness to asperity height ratio, shear rate, and normal load on the shear behavior of TSL penetrated rock joints were investigated. The direct shear apparatus used consisted of two...

Accurate testing coal isotherm can play a significant role in the areas of coal seam gas drainage, outburst control, CO2 geo-sequestration, coalbed methane (CBM) and enhanced coalbed methane recovery (ECBM) etc. The effect of particle size on the CO2 and CH4 sorption capacity of bituminous coal from Illawarra, Australia was investigated at 35°C and...

Numerical modelling of fully grouted rock bolts loaded in tension is presented by implementing a non-linear bond–slip relationship of bolt–grout interface into a commercial finite difference rock mechanics code. The proposed model shows a close match with the experimental results and analytical predictions in terms of load–displacement relationship...

Thin spray-on liners (TSLs) have been attracting increasing attention as an alternative to steel mesh in underground roadway support. In order to investigate the shear strength of glass fibre reinforced TSLs, an improved punch test was developed: the steel ring is replaced by TSL plates and four screws are used to tighten the TSL sample between the...

The variation of the shear strength of infilled rock joints under cyclic loading and constant normal stiffness conditions is studied. To simulate the joints, triangular asperities inclined at angles of 9.5° and 18.5° to the shear movement were cast using high-strength gypsum plaster and infilled with clayey sand. These joints were sheared cyclicall...

The reinforcement quality of the fully resin encapsulated bolt depends on several factors, which are a combination of the bolt design configuration, bolt/hole diameter ratio and installation procedure. A total of ten bolts were installed into 1.7 m long threaded steel pipes with different resin spin times. The pipes were retrieved from the installe...

Rock fracture roughness and tortuosity caused by contact asperities produce extra resistance for fluid flow in comparison with the channel consisting of two smooth parallel plates. To characterise the role of roughness and tortuosity in water flow through rock fractures, the existing studies of the effect of fracture roughness and contact area (tor...

The effect of long term exposure of full size bolts to corrosive environments is presented. A special test rig was used to test four bolts under different loading conditions. Four X-grade identical profile bolts, each 21·7 mm core diameter (23·7 mm full diameter) were subjected to prolonged corrosion testing using acid sulphate water. The pH value...

Steel mesh is used as a passive skin confinement medium to supplement the active support provided by rock bolts for roof and rib control in underground coal mines. Thin spray-on liners (TSL) are believed to have the potential to take the place of steel mesh as the skin confinement medium in underground mines. To confirm this belief, large scale lab...

Advanced microfluidic technology was used to examine the microscopic viscous and inertial effects evolution of water flow in rock joints. The influence of void space on fluid flow behaviour in rock joints under different flow velocities was experimentally investigated at the micro scale. Using advanced fabrication technology of microfluidic device,...

A new numerical model is presented to simulate fracture initiation and propagation in geological structures. This model is based on the recent amalgamation of established failure and fracture mechanics theory, which has been implemented to the finite difference FLAC code as a constitutive FISH user-defined-model. Validation of the model has been st...

This paper presents the difference of behaviour between fully grouted bolts with and without free end slip when loaded in tension. An analytical approach is proposed for fully encapsulated bolts when the free end of the bolt slips. This model is based on the existing bond–slip relationship of bolt–grout interface with no free end slip. The derived...

A numerical modelling approach of a mine roadway reinforced with fully encapsulated rockbolts is proposed to study the interaction between rockbolts and the rock mass. The rockbolt bond–slip relationships defined by conducting push tests of short rockbolts are implemented in the rockbolt elements used in the two-dimensional Fast Lagrangian Analysis...

Effects of shearing direction on shear behaviour of rock joints were studied. Artificial triangular asperities with initial asperity angles of 9.5° (Type I) and 18.5° (Type II), inclined at 0°, 30°, and 60° from the direction perpendicular to the shearing movement were cast using high strength gypsum plaster. Samples were tested at different initia...