Influence Of Fault Zones Research Articles

To explore the optimal solution of different mapping units and classifiers and their application in the susceptibility evaluation of slope geological disasters

Slope geological disaster is a type of natural disaster that is prevalent in the plateau mountainous area. Its occurrence frequently brings substantial harm to the local human population and living environment. The aim of this research is to investigate the suitability of various mapping units for different classifiers in the process of creating susceptibility zoning maps for slope geological disasters and to evaluate the effectiveness of each model. Concurrently, the susceptibility map produced by the high-accuracy model will assist relevant authorities in conducting disaster management tasks and also serve as a reference for modeling the susceptibility assessment of environmental geological disasters in other mountainous regions. Fuyuan County of China was considered as the research area, based on two different mapping units and four classifiers. Nine factors leading to disasters, such as elevation and topographic relief, were chosen as the evaluation indexes. With the help of the ArcGIS platform, the zoning map of geo-logical disaster susceptibility is drawn. Ultimately, the accuracy of the evaluation results was verified by the receiver operating characteristic curve and the confusion matrix. The findings indicate that all approaches are capable of producing susceptibility maps for geological disasters. However, the outcomes from the four classifiers that utilize slope units are more precise and logical than those that employ grid units. Lithology and the water system emerge as the most significant factors causing disasters in the study area, while the influence of fault zones is found to be minimal. The integration of the slope unit with the random forest classifier achieves the highest accuracy in predictions, maximizing the capabilities of both, and presents a promising application in the susceptibility mapping of slope geological disasters.

Typology of hard rock ground waters within the Lower Sassandra, a main catchment in humid tropical West Africa

Abstract Randomness of fracture networks still makes channelized flow a challenge to track in hard-rock aquifers. While not underestimating geological and hydrological criteria that are also handled here through mapping exercises, this study raises an issue of water quality encountered in lifelong boreholes. Chemical classification checked against a recent conceptual model of bedrock aquifers gives birth to a new typology of groundwater in a complex granitic aquifer system located in the SW of Ivory Coast (West Africa). Major ion chemistry, borehole completion data, digital elevation model and satellite images are used to interpret the geochemical water facies as an expression of connexions between the saprolite and the saprock, or transient insulation. From major ions ratios, cumulate mineralization, carbonate equilibrium, stable isotopes, the maturation of ground waters and mixing between bedrock layers are described at seasonal and local scales. The results highlight some vertical feeding of the water table into the main saprock aquifer owing to shortcuts through the saprolite, along with the existence of dead-ends in the hydraulically active fracture network. Also, some influence of fault zones, either drain or barrier, is confirmed on the (Ca, Mg) bicarbonate water facies within the saprock.

Influence of fault zone on the respect distance and margin for excavation: a case study of the F4 fault in the Jijicao rock block, China

A high-level radioactive waste repository requires a rock mass to have good retardation properties. However, because a fault zone can be a potential seepage conduit for nuclides, its influence on the hydraulic conductivity of that fault zone must be assessed. Key sets of fractures were found based on an assessment of the statistical characteristics of fracture orientations and the tectonic analysis of a representative north–east fault in the Jijicao rock block in the Beishan region of Gansu Province, China. The trace midpoint density of each set was calculated using ArcGIS, a geographic information system, and a model of the hydraulic conductivity in the fault zone was developed based on a water pressure test and calculations, such that the respect distance and margin for excavation of this fault could also be determined. The calculated results show that the fault core and host rock are less conductive when the damage zone is 10- to 100-fold more conductive due to its greater density of fractures. The density is stable at 100 m, while the key set is stable until 65 m, and the calculated hydraulic conductivity is stable until 25 m; these results are consistent with the results of water pressure analysis.

The North Tabriz Fault, a barrier to groundwater flow in an alluvial aquifer northwest of Tabriz, Iran

Geological structures, specifically faults, may influence the permeability of geological units and so can be an important factor in the movement of groundwater and hydrogeological processes. This study is an investigation of the local influence of the North Tabriz Fault on the hydrogeology of the adjacent unconfined alluvial aquifer. The study area is located northwest of the city of Tabriz, Iran, on the North Tabriz fault zone. The North Tabriz Fault is a prominent tectonic structure with strike-slip right-lateral kinematics and is considered as one of the most active faults in Iran. This study shows that the fault has a major influence on the hydrogeological characteristics of the local aquifers. Sharp changes in the position of aquifer bedrock and aquifer thickness over relatively short distances (<200 m) suggest a near-vertical dip for the fault evidencing its reverse movement. The fault displacement has reduced the saturated aquifer thickness in the northern sector because the northern block (hanging wall) is thrust over the southern block (foot wall). As a result of barrier behavior prohibiting flow across it, the fault has channelized groundwater roughly parallel to its strike. Sharp changes of EC and chloride values over short distances across the fault show that there is no significant leakage or groundwater mixing across the barrier. A Chadha diagram indicates a Ca–Mg–Cl water type for the majority of northern water samples and Ca–Mg–HCO3 type for all southern samples, without any transitional modes. From Gibbs plots, rock type determines the groundwater hydrochemistry. Abundant Ca + Mg in all of the southern water samples are interpreted as related to carbonate weathering and dissolution, increasing SO4 more rapidly than Cl there. Gypsiferous marl and sandstone are prominent throughout the study area, especially in the southern part, and thus can be the sources of excess SO4. As a result of this study, subsurface structural evidences such as hydraulic head patterns, flow path variations and changes in groundwater hydrochemical properties across the fault are useful tools to understand the influence of fault zones on aquifer characteristics and the hydrogeological behavior of these zones.

Hydrodynamic modeling of a complex karst-alluvial aquifer: case study of Prijedor Groundwater Source, Republic of Srpska, Bosnia and Herzegovina

Middle Triassic fractured and karstified limestone and dolomite form a karst aquifer in the Sana River Valley near the town of Prijedor. As a result of intensive tectonic movements, carbonate rocks are mostly below the Sana River level, covered by younger Pliocene and alluvial deposits. The main source of groundwater recharge is infiltration from the Sana River through its alluvium over most of the aquifer. The main objective of the research reported in this paper was to evaluate the hydraulic relationships of the alluvial, Pliocene and karst aquifers in order to better understand the water supply potential of the karst aquifer. Although the use of hydrodynamic modeling is not very common with karst aquifers, the developed model provided significant and useful information on the groundwater budget and recharge type. The influence of fault zones and spatial anisotropy of the karst aquifer were simulated on the hydrodynamic model by varying permeability on the x- and y-axes of the Cartesian coordinate system with respect to the fault, the main pathway of groundwater circulation. Representative hydraulic conductivities were Kx = 2.3·10-3 m/s and Ky = 5.0·10-3 m/s in the faults of NW to SE direction, and Kx = 2.5·10-3 m/s and Ky 1.2·10-3 m/s in the faults of SW to NE trend. Model research showed that the karst aquifer can be used in the long term at maximal tested capacities and that current groundwater exploitation is not compromised in dry periods when the water budget depends entirely on recharge from the Sana River.

Variáveis Geológicas no Comportamento das Razões qc/N em Porto Alegre, RS – Brasil

The gathering of geotechnical investigation by SPT and CPT follow geological and environmental criteria, identified in maps, allowed identify different units, influence zones of degree of maturity or geomorphological conditions, influence of fault zones and different alluvial areas, allowed to identify different behavior of ratio qc/N in soils of Porto Alegre city. This work presents the criteria utilized for this differentiation, showing the figures of correlation between qc and N, and figures showing the behavior of K (qc/N) related to the depth, with considerations about the results.

A simulation using a hybrid method for predicting fault zones ahead of a tunnel face

AbstractBy monitoring and analysing three‐dimensional absolute displacement during tunnel excavation, it is possible to predict discontinuity zones ahead of tunnel face. This paper presents results of the three‐dimensional displacement obtained from three‐dimensional simulations using hybrid method for assessing the effect of discontinuity zones on monitoring data. The influence of fault zones and in situ initial stresses on the three‐dimensional tunnel movement is evaluated. Copyright © 2002 John Wiley &amp; Sons, Ltd.