Effect Of Geological Structure Research Articles

Establishing a Bayesian Network model for predicting rockburst damage potential

In underground mines, rockburst can cause significant damages to underground excavations and equipment, which impacts negatively mine safety and productivity. Hence, the establishment of model capable of predicting the rockburst damage in a reliable manner is essential. Despite the existence of the extensive number of predictive models for rockburst, a reliable prediction of rockburst damage potential is challenging. One of the main difficulties to predict rockburst with existing models is their inability to account for missing or incomplete data, which is commonly encountered in practice. To overcome this issue, in this paper, a Bayesian network (BN) approach is employed to develop a short-term prediction model for rockburst on the basis of mine seismicity monitoring data. A rockburst database consisting of 254 case histories was compiled. The input parameters include the stress conditions, ground support capacity, excavation span, effect of geological structure, peak particle velocity, and the output defined as the rockburst damage scale (RDS) index. The Tree Augmented Naïve Bayes classifier structure was implemented. The proposed BN was tested using 5-fold cross-validation. The practical use of the BN was illustrated as well. Overall, the BN results indicated acceptable prediction accuracies ranging from 70 to 78%. It was concluded that BN could represent a reliable predictor to control excavation damages due to mine seismicity, especially when incomplete data prevail.

Mechanics of compression in talc considering sample quality

Despite numerous applications and occurrences of talc, investigation into its mechanics particularly compression behaviour is limited. This paper presents the mechanics of compression behaviour in talc through a series of oedometer tests for the samples in the reconstituted and intact states. The stress and strain one-dimensional compression paths were studied considering the effects of sample quality and effects of geological structure. The engineering properties, fabric and composition as well as mineralogy were investigated using classification and index tests, scanning electron microscope equipped with EDS and XRD, respectively. The compression curves converge to unique normal compression line. The intrinsic compressibility of talc is low, the yield stress range from low to medium and the sample quality vary from excellent to poor. The sample quality index increases with the in situ specific volume and reduces exponentially with yield stress. Sample disturbance has effect on compression characteristics of intact samples. The commonly used normalising parameters in literature to analyse the effects of structure in compression for geomaterials were not able to capture the real behaviour in talc with low in situ specific volume. Two new stress sensitivity methods which do not require reconstituted samples were developed, and they were found to better represent the degree of enhanced stiffness in compression. The effects of geological structure in compression are positive and small in magnitude, and the destructuration process is rapid in sample with low quality.

Effects of geological structures on rainfall‐runoff responses in headwater catchments in a sedimentary rock mountain

AbstractClarifying rainfall‐runoff responses in mountainous areas is essential for disaster prediction as well as water resource management. Although runoff is considered to be significantly affected by topography, some previous studies have reported that geological structures also have significant effects on rainfall‐runoff characteristics. Particularly in headwater catchments located in sedimentary rock mountains, dips and strikes may significantly affect rainwater discharge. In this study, the effects of geological structures on rainfall‐runoff characteristics were investigated based on observed discharge hydrographs from 12 catchments, which lie radially from the summit of a sedimentary rock mountain. The results obtained were as follows: (1) Even though the topographic wetness index (TWI) distributions of the 12 catchments were similar, there were significant differences in their runoff characteristics; (2) Catchments with average flow direction oriented towards the strike direction (strike‐oriented catchments) are characterized by large baseflows; (3) Catchments with average flow direction oriented towards the opposite dip direction (opposite dip‐oriented catchments) are steep, and this results in quick storm runoff generation; (4) Catchments with average flow direction oriented toward the dip direction (dip‐oriented catchments) are gentle, and this results in delayed storm runoff generation. It was presumed that in strike‐oriented catchments, large quantities of groundwater flowing along the bedding planes owing to hydraulic anisotropy, exfiltrate and sustain the large amount of the observed baseflow, that is, in strike‐oriented catchments, runoff is directly controlled by geological structures. Conversely, in opposite dip‐oriented and dip‐oriented catchments, runoff is indirectly controlled by geological structures, that is, geological structures affect slope gradients, which result in differences in storm runoff generation. Thus, this study clearly illustrates that geological structures significantly affect rainfall‐runoff responses in headwater catchments located in sedimentary rock mountains.

Analysis of the distribution characteristics and laws of in situ stress in China’s coal mines

Based on the measured in situ stress data in China’s coal mines, the relationship among the type of stress field, magnitude of stress, stress value, and the depth of burial was analyzed. The trends in the changes in side pressure coefficient and side pressure ratio were regressed and fitted with the increase in depth. This was compared to the Hoek-Brown curve, and the distribution characteristics and variation laws of underground stress field in China’s coal mines were determined. (1) Generally, in situ stress increases with burial depth, but the geological structure and lithology render horizontal stress considerable. (2) In 87.72% of stress fields, which are considered typical tectonic stress fields, the horizontal stress comes into prominence. (3) About 64% working environment is the middle- and high-stress zones, and low- and ultrahigh-stress zones account for about 18% each. (4) The ratio of horizontal principal stress was distributed within a range of 1.0~2.5, and it was affected very little by burial depth. However, the difference increased continuously with burial depth, causing an obviously growing shear failure of coal and rock. (5) The side pressure coefficient is mostly distributed in 0.9~2.0, and it decreases with burial depth and is gradually close to 1.32. (6) Most side pressure ratio is in 0.5~1.6. When the burial depth is less than 700~750 m, the horizontal principal stress is lower than one in the world. Conversely, the magnitude of horizontal principal stress was more pronounced in deeper areas, but it always plays a leading role in the in situ stress field. (7) The seismic belt has a great influence on coalfield stress fields. Without affecting the stress field, the direction of maximum principal stress is approximately parallel or perpendicular to the trajectories of principal stress in China Continental Plate. However, under the composite effect of geological structure, the direction changed visibly. There is no apparent relationship between the two and no law to follow. The statistics of in situ stress are important reference values for understanding stress distribution in China’s coal mines, and it also has a practical guiding significance for safely and efficiently mining underground.

Effect of Geological Structure on Flyrock Prediction in Construction Blasting

Blasting is sometimes inevitable in civil engineering work, to fragment the massive rock to enable excavation and leveling. In Minyak Beku, Batu Pahat also, blasting is implemented to fragment the rock mass, to reduce the in situ rock level to the required platform for a building construction. However, during blasting work, some rocks get an excessive amount of explosive energy and this energy may generate flyrock. An accident occurred on 15 July 2015 due to this phenomenon, in which one of the workers was killed and two other workers were seriously injured after being hit by the flyrock. The purpose of this study is to investigate the causes of the flyrock accidents through evaluation of rock mass geological structures. The discontinuities present on the rock face were analyzed, to study how they affected the projection and direction of the flyrock. Rock faces with lower mean joint spacing and larger apertures caused excessive flyrock. Based on the steoreonet analysis, it was found that slope failures also produced a significant effect on the direction, if the rock face failure lay in the critical zone area. Empirical models are often used to predict flyrock projection. In this study five empirical models are used to compare the incidents. It was found that none of the existing formulas could accurately predict flyrock distance. Analysis shows that the gap between predicted and actual flyrock can be reduced by including blast deign and geological conditions in forecasts. Analysis revealed only 69% of accuracy could be achieved if blast design is the only parameter to be considered in flyrock projection and the rest is influenced by the geological condition. Other causes of flyrock are discussed. Comparison of flyrock prediction with face bursting, cratering and rifling is carried out with recent prediction models.

The effect of geological structure on radon concentration dissolved in groundwater in nearby Anar fault based on a statistical analysis

The radon concentration in groundwater is due to amount of uranium existing in rocks and geological structures. Radon concentration in 33 groundwater samples from agricultural and drinking wells surrounding Anar fault have measured by RAD7 radon detector. The measured values ranged from 1.33 ± 0.48 to 29.91 ± 3.64 Bq L−1. The results show radon concentration varies by distance from main fault and main stream in which the effect of main fault is more than main stream.

Analysis of Mining-induced Valley Closure Movements

Valley closure movements have been observed for decades in Australia and overseas when underground mining occurred beneath or in close proximity to valleys and other forms of irregular topographies. Valley closure is defined as the inward movements of the valley sides towards the valley centreline. Due to the complexity of the local geology and the interplay between several geological, topographical and mining factors, the underlying mechanisms that actually cause this behaviour are not completely understood. A comprehensive programme of numerical modelling investigations has been carried out to further evaluate and quantify the influence of a number of these mining and geological factors and their inter-relationships. The factors investigated in this paper include longwall positional factors, horizontal stress, panel width, depth of cover and geological structures around the valley. It is found that mining in a series passing beneath the valley dramatically increases valley closure, and mining parallel to valley induces much more closure than other mining orientations. The redistribution of horizontal stress and influence of mining activity have also been recognised as important factors promoting valley closure, and the effect of geological structure around the valley is found to be relatively small. This paper provides further insight into both the valley closure mechanisms and how these mechanisms should be considered in valley closure prediction models.

Effects of geological structures on groundwater flow and quality in hardrock regions of northern Tirunelveli district, southern India

Geological and structural influences on groundwater flow and quality were evaluated in the present study in the hardrock regions of Tirunelveli District, southern India. Groundwater is a major source of freshwater in this region to cater to the requirements of domestic and agricultural activity, as there are no surface water resources. Geologically, the area is characterized by charnockites and garnetiferous biotite gneiss. Groundwater in this region is found to occur in the weathered portion under unconfined condition and in fractured/fissured portions under unconfined to semi-confined condition. Existence of deep-seated fractures are minimal. Lineaments/dykes play a major role in the occurrence and movement of groundwater in the region. Lineaments/dykes of the study area can be broadly divided into two types: north–south and west–east oriented structures. Analysis and field observations revealed that the north–south dykes act as a barrier of groundwater while the west–east oriented structures behave as a carrier of groundwater. Both quality and quantity of groundwater is different on the upstream and downstream sides of the dyke. Hence, it is conclusive that the west–east oriented dykes in this region are highly potential and act as a conduit for groundwater movement from recharge areas to the discharge area.

Casing mechanism of engineering hazards in a oil field in central China

Based on the statistics data extracted from underground hazards in “A” region of Yuan Shi oilfield, and with casing failures as an example, engineering hazards, such as sand production, casing hazards, etc., in different geological structures are compared and distinguished. A detailed examination of their relationship is conducted in terms of mineral composition, sedimentary facies and other reservoir aspects. The triggering mechanism of engineering hazards is also theorized. Especially under water injection, the effect of geological structures on engineering hazards is illustrated. Finally, engineering hazards prevention and minimization measures are presented. The results show that in fluvial sediments, casing damage is mainly on the outside of the casing and casing bending. In a shallow lake environment, casing damage is chiefly of the leakage and rupture type.

Characterization and Triggering Mechanism of Underground Engineering Hazards in a Terrestrial Oil Field in Central China

On the basis of the statistics data extracted from underground hazards in “A” region of Yuan Shi oilfield, and with casing failures as an example, engineering hazards such as sand production, casing damages etc. in different geological structures are compared and distinguished. A detailed examination of their relationship is conducted in terms of mineral composition, sedimentary facies and other reservoir aspects. The triggering mechanism of engineering hazards is also theorized. Especially, under water injection, the effect of geological structures on engineering hazards is illustrated. Finally, engineering hazards prevention and minimization measures are presented. The latter include: 1) the shallow underground water must be fine filtered with oxygen removed & sterilized, and water pipelines corroded in the entire process; 2) reduce the casing pipe intensity by injected water corrosion.

Effect of geological structure and stressed conditions of rock mass in designing underground power house

Effect of geological structure and stressed conditions of rock mass in designing underground power house

Effects of Geological Structure and Geophone Field Configuration on Seismic Velocity Accuracies

In the seismic reflection method the determination of vertical signal velocities is of basic importance, but timing perturbations which result from raypath distortion may cause discrepancies in the process of calculating true velocities from the velocities obtained by a stacking process. In particular, if different configurations of geophones ('field configurations') are employed over an area, the 'stacking velocities' obtained can vary greatly with different shot-to-receiver distances, even though a constant separation ('spread length') of the geophones is maintained. In this paper the modelling of raypaths in some simple geological sections shows that the combined effects of both velocity errors and timing errors may be so significant as to obscure the resolution needed in the method for the detection of subtle hydrocarbon traps.

SIGNIFICANCE AND IMPLICATIONS OF SHINGLING IN REFRACTION RECORDS *

ABSTRACTThe occurrence of shingling in. long range refraction records often makes the task of the seismic interpreter heavier, especially when several refractors are encountered and the velocity contrasts are small.The explanation of the phenomenon given by the existing literature is examined and the theoretical results are compared with the observed data on field records.In field seismograms shingling must be separated from the effect of geological structures or lateral discontinuities.If an appropriate analysis of shingling is possible, this phenomenon can be related to the type of refracting layer, being a useful tool to a qualitative approach.On the other hand the implications of shingling are examined on the side of the geometrical interpretation

SIGNIFICANCE AND IMPLICATIONS OF SHINGLING IN REFRACTION RECORDS *

AbstractThe occurrence of shingling in. long range refraction records often makes the task of the seismic interpreter heavier, especially when several refractors are encountered and the velocity contrasts are small.The explanation of the phenomenon given by the existing literature is examined and the theoretical results are compared with the observed data on field records.In field seismograms shingling must be separated from the effect of geological structures or lateral discontinuities.If an appropriate analysis of shingling is possible, this phenomenon can be related to the type of refracting layer, being a useful tool to a qualitative approach.On the other hand the implications of shingling are examined on the side of the geometrical interpretation

The Effect of Geological Structure Upon Microseismic Disturbance.

The Effect of Geological Structure Upon Microseismic Disturbance.