Complex Rock Formations Research Articles

Radiological environmental impact analysis of the uranium mining site in Mika, Nigeria using time series forecast model.

This study employs time series forecasting, specifically Seasonal Auto-Regressive Integrated Moving Average, to predict the radiological impact of uranium mining in Mika, Nigeria. By utilizing meteorological data to model the dispersion of radioactive emissions to receptors, allowing for a comprehensive assessment of potential health and environmental consequences. The study observed a slight change in the Total Effective Dose Equivalent (TEDE) at the nearest residence northeast receptor between the actual and the forecasted data. The findings could be largely because of the basement complex rock formations that characterized the Mika region. The study recommend proper monitoring and evaluation should be done before full-scale mining can be carried out. However, the TEDE is generally below the International Atomic Energy Agency recommended level of 1mSv per y for public exposure. The research demonstrates the significance of predictive modeling in managing and mitigating the radiological risks associated with uranium mining activities. Findings contribute to informed decision-making and sustainable resource extraction practices in Mika, Nigeria.

Research on the "shape-performance-control" integrated digital twin system for boom-type roadheaders

The boom-type roadheader plays a crucial role in coal mining. However, conducting the real-time monitoring of the mechanical performance and comprehensive adaptive cutting in the dynamic cutting process are challenging. To address these issues, a digital twin system that integrates the elements of “shape, performance, and control” for roadheaders is presented in this paper. The system comprises three components: physical space, service space, and twin space. The service space forms the core of the entire system. Within this space, twin models and control models are created using numerical simulation, artificial intelligence and multi-source data fusion technology. These models serve the purpose of predicting the roadheader’s mechanical performance and controlling the swing speed of the cutting arm. The physical space is built using technologies such as robot kinematics, electrical systems, hydraulic transmission, and other relevant techniques. This approach facilitates the transmission of multi-sensor data to twin models. The control model then manages the roadheader’s function based on the output signals from the control model. The twin space is constructed utilizing physical rendering engines, databases, and 3D modelling tools. This space visualizes and stores the movement, performance, and control parameters of the roadheader. The results demonstrate that the average absolute error between the measured data from the test’s three position strain gauges and the predicted data from the twin system is 10.38 MPa. Furthermore, the twin system achieves an average update interval of 0.34 s, allowing real-time stress monitoring of the structural components of the roadheader and preventing damage caused by overload. The proposed control model enables adaptive adjustment of the swing speed of the cutting arm in approximately 0.3 s. This improvement significantly enhances the adaptive cutting capabilities of roadheaders when dealing with complex coal and rock formations.

Key factors controlling oil contents in different lithofacies shales from the Funing Formation, Subei Basin: Evidence from scanning electron microscopy

Lacustrine shales with complex mineral compositions and rock formations are associated with different lithofacies, and shale oil contents vary significantly depending on the lithofacies. This study examines lacustrine shales from the Funing Formation, Gaoyou Sag, Subei Basin using scanning electron microscopy, total organic carbon (TOC), Rock-Eval pyrolysis, X-ray diffraction, thin section, and nuclear magnetic resonance T1–T2 to determine the key factors controlling oil content in different shale lithofacies. Shale lithofacies were determined based on the mineral composition, rock structure, and organic matter content. The micro-distributions of shale oil in different lithofacies were disclosed. The results show that the studied shales in Gaoyou Sag are primarily divided into massive felsic-rich, stratified felsic-rich, laminated felsic-rich, laminated felsic, laminated calcareous-rich, and laminated calcareous shales. Massive felsic-rich shales have the largest TOC, S1, and free oil contents associated with organic-rich shales. Stratified felsic-rich shales have the larger TOC, S1, and free oil contents, followed by the laminated felsic-rich and felsic shales. However, laminated calcareous-rich shales are characterized by larger TOC but lower S1 and free oil contents, whereas laminated calcareous shales have the lowest organic matter and oil contents. Shale oil content is mainly affected by the organic matter content and the development of reservoir space. Massive felsic-rich shales are characterized by almost all pores saturated with oil. The oil contents in stratified felsic-rich, laminated felsic-rich, laminated felsic, and laminated calcareous-rich shales are primarily affected by the development of reservoir spaces, followed by organic matter abundance. However, laminated calcareous shales are the opposite. Interparticle pores at the edge of granules are the most developed pores, whereas interparticle pores associated with quartz are generally saturated with oil, followed by those related to calcite or dolomite. Intraparticle pores in clay minerals are usually free of oil. Moreover, shale oil primarily occurs in large interparticle pores. The organic-rich massive felsic-rich and organic-bearing laminated felsic-rich shales are favorable for shale oil enrichment, and organic-bearing laminated felsic-rich shales with larger pores and interlayer micro-fractures may be the optimal lithofacies for shale oil. This study provides insight into the micro-distribution of shale oil in different lithofacies, which will guide shale oil development in the Gaoyou Sag, Subei Basin.

Modeling of multi-mineral-component digital core based on Res-Unet

Abstract As the exploration of oil and gas moves further into less conventional reservoirs, effective methods are required for the fine evaluation of complex formations, particularly digital core models with multiple mineral components. The current technology cannot directly produce digital core images with multiple minerals. Therefore, image segmentation has been widely used to create digital multi-mineral core images from computed tomography (CT) images. The commonly used image segmentation methods do not provide satisfactory CT images of complex rock formations. Consequently, deep learning algorithms have been successfully applied for image segmentation. In this paper, a novel method is proposed to develop an accurate digital core model with multiple mineral components based on the Res-Unet neural network. CT images of glutenite and the corresponding results of quantitative evaluation of minerals by scanning electron microscopy are used as a training dataset for the automatic segmentation of CT core images. The used quantitative metrics show that compared with the multi-threshold and U-Net segmentation methods, the Res-Unet network leads to better results of mineral morphology and distribution recognition. Finally, it is demonstrated that the proposed Res-Unet-based segmentation model is an effective tool for creating three-dimensional digital core models with multiple mineral components.

Enhancing the Detectability of Deep-Sensing Borehole Electromagnetic Instruments by Joint Inversion of Multiple Logs Within a Probabilistic Geosteering Workflow

The cost of drilling wells on the Norwegian Continental Shelf is exceptionally high, and hydrocarbon reservoirs are often located in spatially complex rock formations. Optimized well placement with real-time geosteering is crucial to efficiently produce from such reservoirs and reduce exploration and development costs. Geosteering is commonly assisted by repeated formation evaluation based on the interpretation of well logs while drilling. Thus, reliable, computationally efficient, and robust workflows that can interpret well logs and capture uncertainties in real time are necessary for successful well placement. We present a formation evaluation workflow for geosteering that implements an iterative version of an ensemble-based method, namely the approximate Levenberg-Marquardt form of the Ensemble Randomized Maximum Likelihood (LM-EnRML). The workflow jointly estimates the petrophysical and geological model parameters and their uncertainties. This paper demonstrates joint estimation of layer-by-layer water saturation, porosity, and layer-boundary locations and inference of layers’ resistivities and densities. The parameters are estimated by minimizing the statistical misfit between the simulated and the observed measurements for several logs on different scales simultaneously (i.e., shallow-sensing nuclear density and shallow to extra-deep electromagnetic (EM) logs). Numerical experiments performed on a synthetic example verified that the iterative ensemble-based method could estimate multiple petrophysical parameters and decrease their uncertainties in a fraction of the time compared to classical Monte Carlo methods. Extra-deep EM measurements provide the best reliable information for geosteering, and we show that they can be interpreted within the proposed workflow. However, we also observe that the parameter uncertainties noticeably decrease when deep-sensing EM logs are combined with shallow-sensing nuclear density logs. Importantly, the estimation quality increases not only in the proximity of the shallow tool but also extends to the look ahead of the extra-deep EM capabilities. We specifically quantify how shallow data can lead to significant uncertainty reduction of the boundary positions ahead of the bit, which is crucial for geosteering decisions and reservoir mapping.

Research on the Synchronization and Shock Characteristics of an Air Adjustment Mechanism for Cluster-Type DTH Hammers under Partial Loads

Cluster down-the-hole (DTH) hammers are often used in large-diameter hard rock drilling operations. Due to complex rock formation conditions, cluster DTH hammers cannot adjust the working airflow in time according to rock formation conditions, resulting in frequent damage to cluster DTH hammers and low work efficiency. Aiming at this problem, this paper proposes an airflow adjustment mechanism as a solution. In this paper, the operation stability and airflow adjustment characteristics of the adjustment mechanism are studied. The impact characteristics and driving force variation characteristics of the adjustment mechanism under different speeds and loading modes are analyzed, and the results show that the movement impact of the adjustment mechanism increases with the increase of the movement speed of the driving actuator under the same loading mode. With the increase of the eccentric load, the critical movement speed of the driving actuator decreases when the adjustment mechanism moves without impact. The test verifies the synchronization characteristics of the adjustment mechanism under different load modes and different control valves. The results show that, under the condition of uniform load, the synchronization accuracy of the dividing/focusing valve and the proportional valve is good. With the increase of the eccentric load difference, the synchronization performance of the dividing/focusing valve becomes worse, and the average error increases. The test results in this paper are of great significance for guiding the engineering design of cluster DTH hammers.

Assessment of a New Dam Site for Water Supply Potential in Bauchi Metropolis, Nigeria

The maximum yield of 90,000 m3 /day from the existing Gubi dam in Bauchi will barely meet the water demand beyond 2030 at an average water use of 100 litres per capita/day. For higher water demand of up to 250 litres per capita/day expected in an urban centre, the existing dam capacity is inadequate, and the demand should grow to 253,102 m3/day by 2037. This is the rationale for this study, which showed the feasibility of a new dam through technical reviews and analysis of topography, hydrology of the site, field and laboratory investigations, computer analyses and designs. Hydrologic simulation of rainfall-runoff processes for 57 years of rainfall data using the Soil Conservation Service (SCS) method gave an annual runoff volume of 59 Mm3 on a stream in Miri, which can be harnessed to assure adequate water supply in the metropolis. This will require the construction of a 25 m high embankment dam. Topographic survey and analysis indicated that the proposed site has good water retention capability. Although net flow adjustment analysis showed a high evaporation loss of up to 13.5 Mm3 annually, seepage loss is expected to be small in view of the underlying basement complex rock formation.

A gas migration law study of a large-scale 3D physical similarity simulation with an adaptive Kalman filter algorithm

PurposeIn this study, a physical similarity simulation plays a significant role in the study of crack evolution and the gas migration mechanism. A sensor is deployed inside a comparable artificial rock formation to assure the accuracy of the experiment results. During the building of the simulated rock formation, a huge volume of acidic gas is released, causing numerous sensor measurement mistakes. Additionally, the gas concentration estimation approach is subject to uncertainty because of the complex rock formation environment. As a result, the purpose of this study is to introduce an adaptive Kalman filter approach to reduce observation noise, increase the accuracy of the gas concentration estimation model and, finally, determine the gas migration law.Design/methodology/approachFirst, based on the process of gas floatation-diffusion and seepage, the gas migration model is established according to Fick’s second law, and a simplified modeling method using diffusion flux instead of gas concentration is presented. Second, an adaptive Kalman filter algorithm is introduced to establish a gas concentration estimation model, taking into account the model uncertainty and the unknown measurement noise. Finally, according to a large-scale physical similarity simulation platform, a thorough experiment about gas migration is carried out to extract gas concentration variation data with certain ventilation techniques and to create a gas chart of the time-changing trend.FindingsThis approach is used to determine the changing process of gas distribution for a certain ventilation mode. The results match the rock fissure distribution condition derived from the microseismic monitoring data, proving the effectiveness of the approach.Originality/valueFor the first time in large-scale three-dimensional physical similarity simulations, the adaptive Kalman filter data processing method based on the inverse Wishart probability density function is used to solve the problem of an inaccurate process and measurement noise, laying the groundwork for studying the gas migration law and determining the gas migration mechanism.

Finite element implementation of coupled hydro-mechanical modeling of transversely isotropic porous media in DEAL.II

In geotechnical engineering, modeling geo-structures is challenging, particularly in cases where the interaction between the structures and soil or rock is complex. Most well-known commercial modeling software is based on homogenous and isotropic materials. However, soil and rock are often modeled in heterogeneous and anisotropic media because of the inherent anisotropy of sedimentary rock masses and their stratified structure. In recent decades, coupled hydro-mechanical (HM) interactions in isotropic porous media have been studied; however, the behavior of transversely isotropic porous media is rarely considered. In addition, it is difficult for commercial software such as Plaxis and Flac3D to express complex rock formation where the anisotropy of the material and the associated cracks and fractures could be assembled into a single model. In this study, a finite element implementation using Differential Equation Analysis Library (DEAL.II), an open-source library of finite element codes, was developed to model the fully coupled HM behavior of transversely isotropic porous media. The proposed implementation can be applied to both isotropic and transversely isotropic porous media based on Biot’s theory. The developed code can be used to model poroelastic media with (1) equations of linear elasticity for the solid matrix and (2) diffusion equations for fluid flow based on mass and linear-momentum conservation laws. We verified the performance and accuracy of the code through two examples, i.e., Mandel’s problem with a compared analytical solution and a tunnel excavation process with the Flac3D software. On the basis of these numerical applications, we present the code to model the behavior of various geo-structures such as tunnels and pile–soil interactions with anisotropic materials.

Analysis of Deformation Damage in Deep Well Roadway and Supporting Countermeasures

The roadway with a depth of 760 m in Menkeqing coal mine is located in a complex rock formation, with mudstone containing gangue, serious roof drainage, developed fractures, and surrounding rock softening under water. In addition, affected by mining, the original support of return air roadway in 2201 workface has been difficult to be effective. In this study, FLAC3D was used for analysis of the process and mechanism of roadway deformation. Based on the analysis and combined with the research on deep roadway support theory research, it is determined that the numerical simulation of the joint support form of the bottom angle of the roadway is effectively controlled by using the 45° bottom corner bolt to control the heaving floor of the roadway. In other words, the surrounding rock grouting + anchor cable spraying + bottom corner bolt, and not only the heaving floor of the roadway has been effectively controlled, but also the coal rib and the roof support also have a more obvious prominent effect. According to the design and construction, the roadway maintenance condition is good after the field observation, which indicates that the design parameters are reasonable and can meet the requirements of roadway use, which can provide reference for roadway support under similar conditions.

Nachbrüche im Nahbereich von Störungen – Geotechnische Ursachen und Identifikation

AbstractThe Semmering Base Tunnel with a total length of 27.3 km is being excavated from the Gloggnitz portal as well as from three intermediate faces at Göstritz, Fröschnitzgraben and Grautschenhof. The geological conditions of the project are characterized by tectonically extremely complex rock formations with difficult geotechnical conditions. The excavation passes through numerous fault zones with deep overburden. During the excavation works, some large‐volume collapses occurred. In this article, the collapse events are reconstructed from the available geological and geotechnical information. The reconstruction of the observed system behaviour is based on analytical and numerical calculations. The aim is to identify the respective failure mechanisms.

A slope movement in a complex rock formation: Deformation measurements and DEM modelling

The case history of a deep-seated slope movement in a complex rock formation (Marly-Arenaceous Formation) is analyzed. The movement, monitored for more than 20years, was recognized after the discovery of intense cracking in the concrete lining of a hydraulic tunnel running across the slope. The time history of displacements shows that the ongoing deformation process is essentially a stationary creep phenomenon, also influenced by transient variations in pore pressure distribution. The shearing zone is mainly formed by tectonized clay gouge and is characterized by a mobilized strength close to residual. The slope has been modelled (by DEM approach) as a complex blocky structure defined by several joint sets: bedding planes, inclined and sub-vertical joints. Different hypotheses about the geometry of the slip surface, compatible with field evidences, are discussed as well as their influence on the critical friction angle of the slope. The type of model adopted for rock mass, with continuous or staggered joints, influences the pre-failure deformation mode, but the failure conditions are not as much affected. Finally, the response of DEM models to the increase in water level at the toe of the slope and to the rise of the groundwater table inside the slope has been analyzed. The results of simplified models, without flow calculation, and coupled hydro-mechanical analyses are compared, finding some relevant differences.

A deep seated movement in a marly-arenaceous formation: analysis of slope deformation and pore pressure influence

The case history of a deep-seated slope movement in a complex rock formation (Marly-Arenaceous Formation) is analyzed. The movement, monitored for more than 20 years, was recognized after the discovery of intense cracking in the concrete lining of a hydraulic tunnel running across the slope. The time history of displacements shows that the ongoing deformation process is essentially a stationary creep phenomenon, also influenced by transient variations in pore pressure distribution. The slip surface is formed by a tectonized clay gouge layer and the mobilized shear strength is close to residual. The slope has been modelled (UDEC code) as a complex blocky structure defined by several joint sets: bedding joints, inclined and sub-vertical discontinuities. Different geometries of the slip surface, reasonably varied within the range of hypotheses compatible with field evidences, have limited influence on the limit friction angle of the slip surface. Joint patterns have influence on the deformation mode and minor impact on the mobilized friction angle. The model response is less sensitive to the water level at the slope toe as compared to the rise of groundwater table.

Comparative Study of Soils Derived from Sedimentary and Basement Rock Formations of the Lower Ogun River Floodplain, South Western Nigeria

The anisotropic nature of soils makes it imperative to study the associations of soils and regional landscapes for sustainable land use planning and management. This paper examines soil properties involving four catenas on two parent rock formations in two ecological zones. It simultaneously studied the vertical and lateral variations of soil properties in relation to parent materials, slope positions and pedogenetic-geomorphic processes along hillslopes extending over basement complex and sedimentary rock formations of the Lower Ogun River Floodplain. The different parent materials from different parent rocks, slope positions and pedogenetic-geomorphic processes accounted for the intra-profile and inter-profile variations of topsoil and subsoil properties in the landscape. The study demonstrated that in a given hillslope, topsoil and subsoil properties show more significant differences (p<0.05) between diverse rock formations, distinct parent materials and different slope positions than within them. This suggests that the soils are genetically linked due to the influence of relief (differences in elevations) along the hillslope and geomorphic factors (parent materials) which affirms catenary associations of soils along the hillslopes.

A SUMMARIY OF THE DEVELOPMENT PRESENT SITUATION FOR THE VOLCANIC-ROCK GAS RESERVOIR

According to the successful example of the exploration and exploitation for the volcanic rocks gas reservoir of domestic and overseas. Geologic feature and development characteristic of general volcanic rocks gas reservoir was analyzed and summarized. That is to say, volcanic rocks gas reservoir has numerous rock type, complex rock formation nature, complicated pore structure, special and diversified reservoir space, small porosity and low permeability. The differential of porosity and permeability was big. The reservoir heterogeneity was serious. The containing gas area and effective thickness change a lot. The gas-water distribution is complex. The reservoir is moderate porosity and low permeability double porosity reservoir. It is key to analyze the geologic feature and development characteristic of volcanic rocks reservoir for Shengping Gas- field. The yield of Shengping Gas- field is steady. The reservoir pressure of Shengping Gas- field declined a little. The output of gas well is closely related with fracture. The fracture spacing has an important guide meaning for well position deployment. The incremental production measure and reservoir protective measure of volcanic rocks gas reservoir was presented.

A review of in-situ testing of rock mechanical parameters in hydropower projects of Nepal

In-situ testing of rock mechanical parameters is essential for rock mass characterisation. The rock mass characterisation is important in design and construction of underground works forming major component of Hydropower projects. The major civil structures of most of the hydropower projects planned in Nepal have to be founded on complex rock formations on fragile geological environments. In-situ rock mechanics tests carried out at various hydropower projects sites are described and the findings are summarised.

Wave propagation, damage evolution, and dynamic fracture extension. Part II. Blasting

Blasting and blast-induced three-dimensional dynamic fracture propagation in prestressed complex rock formations are addressed. Three-dimensional cube-type laboratory models fabricated from PMMA are dynamically loaded with explosives and the resulting contained fracture structures are studied. Highspeed photography is used to record the dynamic evolution of blast-induced fractures and the effect of stemming of the borehole and blasting under uniaxial stresses is investigated. The series of three-dimensional experiments provide not only new information on the physics and mechanics of the development of the fracture network during blasting but also serve as an input and guide for experts in numerical simulation.

Monolithic stability analysis of Ertan Arch Dam in complex rock formations : Zhou Weiyan; Yang Ruoqiong; Yang Quiang Proc 7th ISRM International Congress on Rock Mechanics, Aachen, 16–20 September 1991V1, P827–831. Publ Rotterdam: A A Balkema, 1991

Monolithic stability analysis of Ertan Arch Dam in complex rock formations : Zhou Weiyan; Yang Ruoqiong; Yang Quiang Proc 7th ISRM International Congress on Rock Mechanics, Aachen, 16–20 September 1991V1, P827–831. Publ Rotterdam: A A Balkema, 1991

Tunnelling in complex rock formations in China. Importance of geotectonic stress and time effects : Tan Tjong Kie Proc International Symposium on Underground Engineering, New Delhi, 14–17 April 1988 V1, P15–26. Publ Rotterdam: A A Balkema, 1988

Tunnelling in complex rock formations in China. Importance of geotectonic stress and time effects : Tan Tjong Kie Proc International Symposium on Underground Engineering, New Delhi, 14–17 April 1988 V1, P15–26. Publ Rotterdam: A A Balkema, 1988

Deformation monitoring of galleries in fractured rockmass and research on failure mechanism of surrounding rocks: Bai Shiwei; Gu Zhimeng Proc International Symposium on Engineering in Complex Rock Formations, Beijing, 3–7 November 1986P909–914. Publ Beijing: Science Press, 1986

Deformation monitoring of galleries in fractured rockmass and research on failure mechanism of surrounding rocks: Bai Shiwei; Gu Zhimeng Proc International Symposium on Engineering in Complex Rock Formations, Beijing, 3–7 November 1986P909–914. Publ Beijing: Science Press, 1986