Geological Assessment Research Articles

The Application of the Analytic Hierarchy Process (AHP) in Mine Geological Environment Evaluation

Mine environmental geological assessment usually uses the expert subjective assignment to determine the weights of affecting factors, but the mine environmental geological problems are the result of many factors. Each factor is complex on the suitability of the influence factors, and the factors interrelate and restrict each other, so the human factor is of great impact. Take the geological quality evaluation of the mine environment of Shanxi, Shaanxi and Inner Mongolia mining area as an example, this article discusses in detail the process of determining the weights of evaluation factors by using the analytic hierarchy process (AHP), which increases the scientific nature of the assignment and reduces the subjectivity, which achieves satisfactory results.

Characteristics, causation, and rehabilitation of Zhouqu extraordinarily serious debris flows in 2010, China

In early morning of Aug 8th, 2010, the rain-triggered tremendous debris flows broke out simultaneously at the Sanyanyu ravine and Luojiayu ravine, which locate in the north part of Zhouqu County town. The debris flow is the most severe event of the same kind of disasters in the past sixty years in China, which caused great losses of people’s lives and properties. Based on field investigation, remote sensing image interpretation and analysis of local climatological data, the local topographical conditions, active tectonic movement, massive debris source and torrential rains were the main formation causes which induced the catastrophic debris flows. Moreover, detailed geological surveys were carried out following the disaster, the other geological potential hazard sites were found out, and the geological and seismic hazard assessment has been put into practice. At last, scientific and appropriate countermeasures have been suggested to prevent and mitigate the extraordinarily serious debris flow.

Engineering geological assessment for route selection of railway line in geologically active area: A case study in China

Abstract The Cheng-Lan railway links Chengdu, a central city in Southwestern China, and Lanzhou, a central city in Northwestern China. The railway passes through the Longmenshan fault zone (Wenchuan earthquake happened there on May 12, 2008), Minjiang fault zone, and Dongkunlun fault zone, which are all active. It runs over the Yangtze River and the Yellow River, and crosses high mountains and deep valleys. There exists, along the railway’s alignment, different kinds of strata of hard granite and soft, weak metamorphic rocks such as carbonaceous slate, schist, and phyllite. It is, therefore, a key issue for such an infrastructure construction to assess the engineering geological conditions and risks, so as to mitigate or avoid possible georisks and to offer optional designs. Geological survey and georisk assessment along the railway corridor are carried out. Special attention is given to active faults, earthquakes and seismic zones. Based on these, discussions about geological aspects for route selection of the railway are conducted and countermeasures for georisk control are proposed accordingly. Main conclusions are achieved as follows: (1) Geohazards such as landslides, rockfalls and debries flows dominate both the route selection of the railway and the engineering structures (e.g., tunnels or bridges) adopted; (2) Tunnel has been proved to be an excellent structure for linear engineering in geologically active area; and (3) In the case where avoiding is impractical, necessary protection measures should be taken to engineering slopes in high earthquake intensity areas, especially the area with earthquake of Ms. 8 or greater.

Shallow water body data processing based on the seismic oceanography

Physical properties of sea water, such as salinity, temperature, density and acoustic velocity, could be demarcated through degradation of energy caused by water absorption, attenuation and other factors. To overcome the challenging difficulties in the quick monitoring of these physical properties, we have explored the high resolution marine seismic survey to instantly characterize them. Based on the unique wavefield propagating in the sea water, we have developed a new approach to suppress the noise caused by the shallow sea water disturbance and obtain useful information for estimating the sea water structure. This approach improves seismic data with high signal-to-noise ratio and resolution. The seismic reflection imaging can map the sea water structure acoustically. Combined with the knowledge of local water body structure profile over years, the instant model for predicting the sea water properties could be built using the seismic data acquired from the specially designed high precision marine seismic acquisition. This model can also be updated with instant observation and the complete data processing system. The present study has the potential value to many applications, such as 3D sea water monitoring, engineering evaluation, geological disaster assessment and environmental assessment.

Buracas: Novel and unusual sinkhole-like features in the Abrolhos Bank

Novel and unusual sinkhole-like features are described for the Abrolhos Bank continental shelf, eastern Brazil, based on geophysical and geological assessments. These unusual structures are large cup-shaped depressions similar to sink/blueholes (10–75m in diameter, 8–39m in height), occurring in a consolidated carbonate substrate in the mid and outer shelf. A total of 36 such features, locally named buracas, were found between 41 and 161km off the coast and between 24 and 65m depth (the bottom of these features may be as deep as 93m). The buracas’ walls are mainly composed of encrusting coralline algae. Radiocarbon dating has provided ages of 5400±90yr Cal BP, 8630±90yr Cal BP and 39,200±400yr BP. Besides providing a comprehensive description of these novel structures within the mesophotic zone, the potential mechanisms by which these sinkhole-like structures originated are discussed here, as well as the possible active mechanisms impeding their filling with sediments and biogenic material. We hypothesize that their origin could be related to either typical sinkhole formation during subaerial exposure or to a partially Holocene growth pattern influenced by antecedent morphology and gas/fluid escaping due to organic matter decomposition. The buracas are relevant not only because they comprise outstanding novel features, but also because they are relevant targets for marine conservation, as they enhance productivity and aggregate biomass in a region under growing fishing pressure.

Assessment of Regional Geological Disaster on Grey Clustering Methed in Shulan

Gray clustering method was used to establish the regional geological disaster risk assessment model by factor of the mean annual rainfall, relative height, ground slope ，geomorphological type, rock and soil type, fracture density, earthquake intensity, vegetation cover rate, human activity. This model was used to Predictive assessment of geological disasters in the Jilin Shulan region which is divided into the Ⅰ, Ⅱ, Ⅲ, Ⅳ districts according to the disaster assessment level. The Comparison of the model predicted disaster area and the actual geological disaster areas was correlation (accuracy) of 75% or more. The study confirms that the gray clustering method to predict geological disasters is effective to reduce the loss of geological disasters and to prevent geological disasters.

Engineering Geological and Geophysical Assessment of the 2009 Jiwei Shan Rockslide, Wulong, China

This study presents the engineering geological and geophysical assessment of the June 5, 2009 Jiwei Shan rockslide, Wulong, China. Jiwei Shan is a part of Wulong karst terrain lithologically, it’s composed of Quaternary Deposits, Jialingjiang Formation, Maokou, Qixia, Liangshan and Hanjiadian Groups (chronologically from younger to older). The surface is highly irregular (pinnached), the rocks contain two sets of fractures, networks of convoluted solution channels and caves and there are large voids filled by soil mantle. It’s a south-north dipping limb of an anticline fold composed of sedimentary rocks, mainly of limestone of variable composition, mudstone and shale and series of limestone deposited with interbedded mudstone and shale. There are two sets of steeply dipping fractures developed in the Maokou and upper strata of Qixia Groups; set one trending EW and set two trending nearly SN directions. The study has been conducted by geological fieldwork, geophysical investigation (Vertical Electrical Sounding), petrographical and scanning electron microscope (SEM) studies and laboratory testing on rock samples collected from Jialingjiang Formation and Maokou and Qixia Groups. The study of the SEM photomicrographs showed that the microcrack propagations in limestone indicated that the increases in crack length and micropores of limestone are indication to the weathering grade increase from II (slightly weathered rock) to grade III and IV (moderately and highly weathered, respectively). The Qixia Group; Middle Layer is highly weathered shale and bituminous interlayer with clear fissility, high porosity, and gently dipping strata, it represents the sliding surface of the rockslide. It’s comparatively weak and strongly weathered compared to the overlain EW and SN fractured stratum. Generally, the tectonic of the study area imposes controls on the rockslide in many ways: created favourable terrain, provided sufficient rockslide prone materials such as highly weathered limestone and shale, weak rocks, created very steep beds which reduced the stability of the highly fractured bedrock of the slope.

Lithospheric magnetic anomalies in Southeast Asia from CHAMP data

New possibilities for the interpretation of long-period magnetic anomalies were opened up by the construction of their first satellite-based maps. The anomalies are due to lateral variations in the magnetic properties and thickness of the deep layers of magnetized rocks. The CHAMP orbital geometry is suitable for providing daily information on the magnetic field over the almost uniform grid above the Earth’s surface. These measurements favor calculation of the spherical harmonic model of the main magnetic field for each day separately. The distribution of regional lithospheric anomalies derived from the satellite measurements over the territory of Southeast Asia is analyzed. These lithospheric anomalies agree with the zonal-block crustal structure of this region revealed from geological assessments.

Геолого-геохимическая оценка возможности нефтегазообразования в верхнепротерозойских отложениях на территории Пермского края

Геолого-геохимическая оценка возможности нефтегазообразования в верхнепротерозойских отложениях на территории Пермского края

Geological, environmental and political aspects of storage and disposal of nuclear materials

This paper presents further consideration of the following interrelation in the energy production sphere: oil and gas business and international projects on the long-term storage of nuclear materials. There are discussed some Russian versions of construction of nuclear depositories as well as corresponding geological assessments. In particular, for the North-West Russia.

Engineering Geological Assessment of Diversion Tunnel of Bakhtiari Damsite (Biggest Two-Arch Concrete Dam in Southern Iran)

Bakhtiari dam is located on the Bakhtiari river, 120 km away from the north of the Andimeshk city. Upper diversion tunnel of this dam with large cross section (13.7 m excavation diameter) and more than 1 km length is a huge construction. The tunnel is placed in the Sarvak formation carbonate rocks of Bangestan group which passes through seven different geological zones with various specifications (SV1, SV2, SV3, SV4, SV5, SV6, and SV7). Joint studies show two main discontinuit including bedding and a main group of joint (J1) together with random joints (faults and fractures). Most of discontinuities have been filled mainly by calcite or calcite and clay. Data deduced from testing and analysis shows good-to-excellent RQD classes with 75 to 90 values. Based on RMR and Q methods, generally rock masses have good to very good quality with 61 to 95 values for RMR and 10 to 35 values for Q. Based on conducted stability analysis, suitable supports were suggested for tunnel by RMR and Q methods. As a result, it can be concluded that all units have a good stability. Therefore, systematic rock bolting with 40–50 mm unreinforced shotcrete has been proposed for some special place. For rock support, according to RMR method, 3 m rock bolts in crown, 2.5 m spacing and with 50 mm shotcrete in crown has been proposed also 3 m rock bolts, based on Q method, 2.3-2.4 m spacing with systematic Bolting without shotcrete or 40 mm unreinforced shotcrete in some units, has been proposed. According to RMR method, for SV5 zone with very good and excellent quality, local 33 bolting without shotcrete and 3m rock bolts, 3 m spacing and spot bolting according to Q method has been proposed.

The new fundamental gravimetric network of Slovenia

The paper presents all stages of the development and processing of the fundamental gravimetric network of Slovenia, which consists of a zero order network, which has six absolute gravity stations, and twenty nine first order gravimetric stations. Descriptions are given of the design of the network, the geological assessment of the gravimetric stations, the gravity survey of the first order network, and the post-processing and adjustment of the gravimetric observations, which was performed in two stages. First the observations in the zero order network were adjusted as a free network, and then a standard adjustment of the first order network was performed. Finally, the adjusted gravity values at the stations were analysed against the Potsdam system, which was the basis of all previous gravimetric calculations in Slovenia. In the analyses an equation for the transformation of gravity values between the Potsdam system and the IGSN71 system (International Gravity Standardization Network 1971) has been derived.

Flood Risk Assessment: Level of Property Damage and Casualty in Northeastern Mindanao Philippines

Flood disaster poses a serious threat to people and property. As society progresses, it constantly modify the environmental landscape which heightens the risk of a disaster. Vital step to disaster reduction should be directed to a comprehensive evaluation of the likelihood of potential losses such as destruction of property and/ or deaths. This study aims to assess the level of risk associated to flood damage and casualty at Community level. The level of risk depends on two interrelated factors: level of hazard and the level of its consequence. A Modified Risk Assessment Framework was utilized to evaluate each of the components of risk. Results significantly matched the geological hazard assessment conducted by local experts. Eleven Villages are high risk of loss of life while eight Villages are high risk of property damage. Restricting physical developments, limiting population expansion, investing on structural measures, boosting the socio-economic condition and strengthening the environmental regulations may help reduce the risk. Keywords - Risk, Vulnerability, Exposure, Hazard, Consequence, Descriptive, Surigao City, Philippines

Geological assessment of the East Greenland margin

The East Greenland margin consists of a number of sedimentary basins, platforms and structural highs (Figs 1, 2). Due to the challenges imposed by the Arctic climate, the region is in an early stage of exploration, and knowledge of the geology and petroleum potential of the margin is limited. However, the significant prospectivity of the conjugated European North Atlantic margin and the nature of the North-East Greenland onshore geology prompt for future offshore exploration. The US Geological Survey thus highlighted the North-East Greenland margin in their latest assessment of the Arctic region (Gautier et al. 2011). With a mean estimate of undiscovered recoverable oil, gas, and natural gas liquids of approximately 31 billion barrels of oil equivalents, the US Geological Survey ranked the North-East Greenland margin fourth in the entire Arctic region, only superseded by known producing petroleum provinces.
 In preparation for the initial East Greenland licence rounds in 2012 and 2013 the Geological Survey of Denmark and Greenland gathers geological information on the margin necessary for the decision process of the Greenland authorities regarding exploration. Geophysical analyses complemented by well-data, onshore geology and information from the conjugated Atlantic margin form the backbone of the study. The East Greenland margin is covered by an open seismic grid supplemented by gravimetric and magnetic data. All existing 2D seismic, gravimetric and magnetic data are included in the current study. Most of the data are confi-dential. Restricted by the general confidential nature of the project, this paper aims to summarise the geology of the East Greenland margin based on the current and previous studies and to briefly assess some of the implications for the regional petroleum prospectivity.

A geological assessment method of floor water inrush risk and its application

The risk assessment of floor water inrush is essential to assure the safe production in a coal pit. Floor aquifuge is the key factor controlling water inrush. Both the impermeability and the resistance to water pressure of an aquifuge vary with its lithology and structure features. With the increase of mudstone content, the permeability and resistance to water pressure of the floor drops. The dense tectonic fissures in floor will transform intact, blocky structure into very blocky or blocky/disturbed structure, lower the resistance to water pressure, increase the permeability of floor aquifuge, and thereby will raise the risk of water inrush. Considering the lithology and structure features, and based on a conventional water inrush coefficient, a coal floor water inrush risk assessment method is put forward. With Fangezhuang coal mine of China as a case study, the implementation of this method is elaborated.

The Potential Effect of CO2-Water-Rock Reaction on The Caprock Formation (<i>Mudstone</i>) Case Study

By using a 1D column geometrical model this paper carried out research on the effects of CO2 penetration on the caprock properties. The result show that due to CO2 ingression the formation water environment changed greatly. The pH reduced to 3.8 from initial 7.48 and then buffered to 5.6; The supercritical CO2 reached to 0.006 m in the caprock, but aqueous CO2 reached to 1.1 m. The self-sealing efficiency worked after about 25 years, and the relevant minerals were calcite, quartz, kaolinite and calcite. The research will provide some technical reference for site selection of CO2 geological storage projects and CO2 leakage assessment.

Landslide Hazard Divisions of Shaanxi Province

With the factor superposition method, we conduct a risk of landslide hazard zoning of Shaanxi province based on the detailed investigation of landslide disaster risk of there. Learn from the experience of past geological hazard zonation, we determine the geological hazard assessment criterion. At the same time, we establish the geological disaster evaluation index system through the analysis of the forming conditions and the influencing factors of landslide disaster. Then, we determine the weight of each index by using gold segmentation method. At last, we make the landslide of Shaanxi province in a four levels of risk division by using the comprehensive analysis of the factors superposition method.

Intelligent Exploration and Appraisal Program for a Multiprospect Development

Summary While many companies are hunting for elephants, exploration results in deep offshore plays over the past years show the increasing trend away from giant-field discoveries toward smaller fields in the 50-100 million bbl range, which tend to be geographically dispersed. These resources need to accumulate to a critical mass, a global threshold, to justify an economically viable development. This is not only a question of volume but also of geographic location of the discoveries, and the threshold, of course, also depends on economic factors. A methodology is proposed to evaluate the potential of a block to lead to a multiprospect development and to optimize exploration and appraisal. It is illustrated by a real deepwater case study including five discoveries and four prospects, 10-30 km apart. The practical approach taken is to define circles or ellipses on a map representing potential hubs and their catchment areas. For each area, a global resource threshold is defined by analogy with other regional developments or by a detailed economic study of representative cases (not discussed in the paper). A probabilistic model of the resource base is derived from the geological assessments of discoveries and prospects. It is entered into Monte Carlo simulation to generate a large number of scenarios representing exploration outcomes and discovery volumes, which are stored in a scenario database. This allows a probabilistic evaluation of the performance of an exploration and appraisal program, using specially developed indicators such as the cumulative discovered P50. Intelligence is introduced in the process by evaluating after each well the probability of meeting the threshold with the remaining wells. If it is low (10% or less) the program is stopped, which has a great impact on risked economics. The main results of the analysis are the economic decision tree with the probability of a development decision and the P90/ P50/P10 of the developed resources; the number of wells in the dry branch of the tree, which actually is not a fixed number but a probability distribution; the definition of a firm and contingent well program; and an optimum drilling order, which may also reduce the well count.

Potentiality of Zubair Formation for deep slurry injection in Kuwait

Selection of a suitable reservoir for fluid storage depends on the reservoir characteristics including permeability, porosity, depth, and reservoir volume. A prospective injection site requires certain quantitative or qualitative value for every parameter involved in a selection criterion. The Barremian–lower Aptian Zubair Formation, at the Burgan oilfield in southern Kuwait, was selected as a potential site for a deep slurry injection project. The Zubair Formation is a major siliciclastic wedge; the target zone (second sand layer) ranges in thickness from 85.3 to 115.8 m with lateral extension measuring 35 by 20 km. The Zubair Formation parameters were evaluated, using log information, provided by Kuwait Oil Company, from three existing oil wells in the Burgan oilfield, and applying Nadeem and Dusseault (Environ Geosci 14(2):61–71, 2007) geological assessment model for deep slurry injection. The results of the model show that the Zubair Formation is an excellent reservoir to receive injected slurried waste.

Study on the Seismic Damaging Effects of Mountainous Towns in Wenchuan Earthquake

Through the survey and research on seismic damage phenomena of damaged towns by Wenchuan Earthquake and geological environment , this article identify that the seismic damage effect of towns damaged by Wenchuan Earthquake mainly includes four types which are fault dislocation effect、site and foundation effect、topography motion amplified action and geologic hazard effect. Site selection of the reconstruction of damaged towns and seidmic design of building and other problems are complex and systemic engineering problems, and they refer to many complex factors such as earthquake faults、geologic hazards、national well-being and the people's livelihood, economic development and so on. The basic principles of consideration should be: for the mountain towns which are located at seismic fault zone and exist serious geological disaster, they must be avoided and relocated off-site; for the towns which are away from the fault for a distance and have no fatal geological disaster risk, we should follow the principles of "scientific planning, normative avoidance and reasonablely adjust the seismic standards" and reconstruct in the former location. Reconstruction site should also pay attention to the concealment of geological hazards, the multiplicity and long-term sustainability of induced factors and so on, so we should enhance the suitability evaluation of the geological environment and risk assessment of geological disaster.