Risk assessment of seismic impact on the roof and pillars stability in Estonian underground (original) (raw)
Related papers
Risk assessment of vibration impact on roof and pillars stability in Estonian underground
2008
The processes of immediate roof exfoliation and pillars collapse accompanies by significant subsidence of the ground surface. Ground surface subsidence causes soil erosion and flooding, swamp formation, agricultural damage, deforestation, changes in landscape, ground water level decreasing and the formation unstable cavities. During the period of four last years the oil-shale mining at experimental mining block introduced by new blasting technology with great entry advance rates (EAR). With such improved technology the EAR reached 4 m that is two times greater than conventional technology can guarantee, but emulsion explosive volume increase up to two times and explosion occurs during 4.5 seconds (~15 times longer than old technology). As a result of such greater advance rates the situatio ns with unsupported room length up to 5.5 m with decreasing the stability of IR can be expected. Analysis of the immediate roof (IR) stability by th e deformation criteria for new room-and-pillar ...
Analysis of Earthquakes Available Influence on „Estonia” Mine Underground Construction Stability
Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference, 2007
The processes of immediate roof exfoliation and pillars collapse accompanies by significant subsidence of the ground surface. Ground surface subsidence causes soil erosion and flooding, swamp formation, agricultural damage, deforestation, changes in landscape, ground water level decreasing and the formation unstable cavities. During experimental measurement of immediate roof absolute deformation on "Estonia" mine three earthquakes were registered. The main reason of investigation has served jumping characteristic of absolute deformation near a pillar after earthquake. Method of final elements for analysis of deformation modelling is used. Seismic risk assessment for underground constructions stability is presented in this study.
Immediate Roof Stability Analysis for New Roomand- Pillar Mining Technology in “Estonia” Mine
Environment. Technology. Resources. Proceedings of the International Scientific and Practical Conference, 2005
This paper analysis the immediate roof (IR) stability by the deformation criteria for new room-andpillar mining technology with modern machines in “Estonia” mine. The new mining technology based on a blasting method to move from packaged to emulsion explosives, from 2.0 m to 4.0 m boreholes (FRANZ SCHELL machine) and on new undercutting (SMAG machine) method. With such equipped new technology the entry advance rates reached 3.8 m. As a result of such greater advance rates the situations with unsupported room length up to 5.5 m with decreasing the stability of IR can be expected. The analysis of IR stability based on an in-site underground testing by the leaving bench-mark stations and convergence measurements. The main targets of this study to determine the main parameters for supported/unsupported IR deformation in areas with great entry advance rates and risk analysis concept elaboration.
Risk Assessment of Pillars Stability for Experimental Mining Blocks in Estonian Oil-Shale Mines
2007
This study addresses risk associated with pillars dimension using new room-and-pillar mining technology with modern machines at Estonian oil shale mines. Processes in overburden rocks and pillars have caused unfavourable environmental side effects accompanied by significant subsidence of the ground surface. The aim of this work was to determine the damage of new technology on pillars dimension and to define the coefficient of blasting operation influence (q). During the last three years, oil shale mining at an experimental mining block introduced a new blasting technology with great entry advance rates (EAR). With such improved technology the EAR reached 4 m, two times greater than conventional technology can guarantee. However, explosive volume increased up to two times and explosions occur during 4.5 seconds (~15 times longer than old technology). In places with complicated mine-geological conditions in the mining blocks, deviation of pillars dimension from project value was up to...
Applied Sciences
Vibrations caused by blasting works have an impact not only on buildings but also the internal environment of the buildings. If these buildings are situated in the surroundings of quarries, the citizens can perceive these vibrations negatively. By applying an appropriate millisecond timing interval, it is possible to lower the intensity of vibrations to the levels that the citizens will not perceive as negative effects inside the buildings. The limit values for this vibration intensity have not been defined to date. For the protection of the building from the vibrations, normative values of the particle velocity and frequency were determined. Hygienic standards for the inhabitants of the housing were applied, which assessed the impact of the vibration on humans through the measurement of the vibration acceleration in the housing. In this article, the results of the research carried out in Trebejov Quarry are presented. The experimental blasts carried out in Trebejov Quarry proved th...
Pillar stability assessment approach for mechanized and drill and blast excavations
Stability of pillars is essential in achieving maximum safety and economic values in room-and-pillar and block cave mining projects. Today's economic market is motivating underground mining companies to increase development advance rates and enhance their NPVs. There is a drive to move away from the conventional drill-and-blast as the main excavation method to alternative means such as mechanized excavation. The cyclic nature of drill and blast, and its inherent tendency to damage the surrounding excavation rock mass and increase support demand often result in poor advance rates. There is little experience with mechanized or non-explosive excavation methods in hard rock metalliferous underground mining. Therefore, the perceived benefits of mechanized excavation over drill-and-blast must be demonstrated. The application of numerical modeling in rock pillar stability analysis has recently become popular. In this paper a numerical modeling approach has been developed and used to investigate the impact of excavation method on the stability of hard rock rib pillars. Phase 2 , the two-dimensional finite element program was selected for the numerical analysis. The 3D advance of two parallel drifts in mechanized and drill and blast excavations is first modeled using the internal pressure reduction approach. The drill and blast excavation is simulated by assigning lower strength and stiffness properties to a zone adjacent to the excavation boundary representing a blast-induced damaged zone, while no such zone is considered to exist in the case of mechanized excavation. The mechanical properties of rock around the mechanized excavation, and the zone outside the perceived blast damage zone are kept the same, and higher than the blast damaged zone. The impact of excavation method on pillar stability is then assessed using the criteria including the distribution of stresses in the pillar, damage initiation and propagation thresholds, strainburst potential as well as depth of yielding.
2010
This paper presents part of the work on ground vibrations induced by blasting, and to estimate safe maximum charge per delay to protect the nearby structures. Blasting near sensitive areas has always been a cause of concern and utmost care has to be taken to keep the charge per delay below the stipulated level A number of field visits were made to collect the geotechnical data, and monitoring ground vibrations induced by blasting. A number of blasts were monitored to study various blast parameters related to blasting Overburden and Coal benches and to understand the effect of blast on the surrounding structures, and rock mass conditions at the mine site. Drilling is accomplished by tire mounted drill machine capable of drilling large diameter holes of 159mm. The drilling pattern of the mine benches is based on the rock formation of the particular bench and varies with the variation in strata from 4 m to 6 m. Holes were charged with Bulk Emulsion Explosives in association with Booster(Cap sensitive). Nonel systems of initiation were used to reduce vibration. Accordingly, the safe charge per delay for the distance of 100 m, 200 m, 300 m, 400 m, and 500 m is 18.9 Kg, 75.9 Kg, 170.8 Kg, 303.7 Kg, and 474.5 Kg, respectively to keep the vibration level below 5 mm/sec for the above geomining conditions of Jindal Power Opencast Coal Mine-Tamnar. The damage criteria was proposed by many organizations including USBM, DGMS, Indian Standards etc based on the Permissible PPV in mm/s and Frequency of the ground vibrations for various types of structures. The criteria based on the Permissible PPV in mm/s and Frequency of the ground vibrations for various types of structures was presented. In the present investigations safe charge per delay 3 was estimated through empirical model to limit the ground vibrations within safe limit of 5 mm/sec considering the structures as sensitive and not belonging to the owner. Hence, the mining technology in terms of blasting pattern and explosive charge was recommended for local environmental protection of the structures.
A new damage criteria norm for blast-induced ground vibrations in Turkey
Arabian Journal of Geosciences, 2014
Environmental problems such as vibration and air blast are often faced and discussed in mining, quarrying, civil construction, shaft tunnel, pipeline, and dam operations, where blasting is inevitable. It is necessary to establish national standards in order to minimize environmental problems induced by blasting and judicial matters in our country as it is in the USA, European Union (EU) countries, and other developed countries. This necessity and the obligation of Turkey, which has started the procedure of joining the EU, to accept EU criteria emphasize the importance of this study. In other words, the establishment of a particular national standard related with this subject is inevitable for Turkey. This will be possible only by studying and applying scientific methods and techniques by experts. This paper presents a new damage criterion norm for blast-induced ground vibrations in Turkey. In this study, first, numerous vibration records were taken in blasting operations performed at different sites and rock units. For these rock units, particle velocity predictions and frequency analysis were done. At the same time, structures in the neighborhoods of these blasts were also observed and investigated. Finally, a damage criterion norm based on risk analysis was established and proposed by using these collected data. In light of the norm to be obtained from the data that were collected in the research, it will lead the excavation work in our country to be performed in such way that they are more effective and will cause minimum environmental problems.
1998
The author considers the structural response of various types of surface structures along with their resonance characteristics as well as magnification and attenuation problems. Experimental data from 20 different mines in India, are compiled and analysed to develop simple general equations for use in field conditions. Interpretation of low frequency waves and their active role in enhancing damage probability of structures is also discussed. Particular situations are examined where low and high dominant band frequencies could obtain. It is suggested that a response analysis be undertaken before establishing damage threshold values of any type of structure.
Potential risks and earthquake effects to the underground constructions
Nepal Tunnelling Conference, 2017
Potential risks and earthquake effects to the underground structures For centuries, mankind has excavated caverns and tunnels for various purposes. Use of underground spaces and tunnels has been increasing year by year. Road and railway tunnels, water conveyance tunnels, hydropower station caverns, oil and gas storage caverns, caverns for defence, tunnels and caverns for mining, waste deposition caverns and underground sport halls are some of the examples of this kind of applications. Through the development of science and technology, tunnel design and construction methods have been very much improved. It is safe to site underground constructions in hard and competent rock from a rock mechanical point of view. However, the tunnels required to meet the present day infrastructural demands cannot always be optimally sited in competent rock, so future tunnelling will to a greater extent than today be carried out in weak rock. When an underground excavation is made in a rock mass, the mechanical resistance, ability to transmit a force and the ability to hold a water pressure are removed in the space created. Thus it causes three primary effects posing risks to the underground stability. In addition, tectonic activities have added stability problems with the fragile regional geology and mountainous topography. Some of the main risks to the underground structures are: • Occurrence of sheared zone due to faults • Ground water problem: ingressing and leakage • Stress induced problem: squeezing and rock burst • Weak rock mass • Thin rock cover • High temperature condition • Hazardous Gas: inflammable, toxic. • Tunnel portal blockade OR flood/debris into tunnel by landslide, GLOF, LDOF. Sometimes earthquake event may cause stability problem to the underground structures but at certain situation only.Empirical correlation of seismic ground shaking-induced damage to over 100 excavated tunnels is given in the Figure 1. Underground structures with seismic risks needs to be designed with the consideration of dynamic loads generated by earthquake.