Hasil untuk "Engineering geology. Rock mechanics. Soil mechanics. Underground construction"

Wenhui Bian, Xiaohui He, Ke-xue Wang et al.

The stability of rock masses in deep underground excavations, such as deep tunnels, shafts, and caverns, critically depends on the mechanical performance of bolt–grout reinforcement systems. In high‐stress and complex geological environments, the interfacial bond–slip behavior between bolts and grouting materials governs the load transfer capacity and long‐term reliability of the support. This study develops an improved shear‐lag analytical model that explicitly incorporates plastic bond degradation, represented through a constant bond stress stage, to capture the complete pull‐out process in four stages: elastic, plastic deformation, debonding, and residual. Closed‐form solutions for the load–displacement response and axial stress distribution along bolts are derived and validated through laboratory pull‐out tests on three types of ribbed bolts embedded in cementitious grout and granite, simulating conditions in deep underground construction. The analytical predictions show excellent agreement with experimental pull‐out tests, capturing both global load–displacement trends and local axial force evolution. Sensitivity analyses indicate that while increasing anchorage length enhances peak capacity, its marginal benefit diminishes beyond a certain threshold. In contrast, the constant bond stress displacement shows a strong positive correlation with the peak pull‐out force, primarily affecting the plastic deformation stage without influencing elastic or residual responses. The proposed model provides a validated, mechanics‐based tool for predicting interface performance in deep underground rock reinforcement systems, offering practical guidance for the design, optimization, and safety evaluation of bonded support in deep mining, hydropower caverns, and large‐span underground spaces.

Jianxiu Wang, Bilal Ahmed, Jian Huang et al.

Research on the multi-field coupling effects in rocks has been ongoing for several decades, encompassing studies on single physical fields as well as two-field (TH, TM, HM) and three-field (THM) couplings. However, the environmental conditions of rock masses in deep resource extraction and underground space development are highly complex. In such settings, rocks are put through thermal-hydrological-mechanical-chemical (THMC) coupling effects under peak temperatures, strong osmotic pressures, extreme stress, and chemically reactive environments. The interaction between these fields is not a simple additive process but rather a dynamic interplay where each field influences the others. This paper provides a comprehensive analysis of fragmentation evolution, deformation mechanics, mechanical constitutive models, and the construction of coupling models under multi-field interactions. Based on rock strength theory, the constitutive models for both multi-field coupling and creep behavior in rocks are developed. The research focus on multi-field coupling varies across industries, reflecting the diverse needs of sectors such as mineral resource extraction, oil and gas production, geothermal energy, water conservancy, hydropower engineering, permafrost engineering, subsurface construction, nuclear waste disposal, and deep energy storage. The coupling of intense stress, fluid flow, temperature, and chemical factors not only triggers interactions between these fields but also alters the physical and mechanical properties of the rocks themselves. Investigating the mechanical behavior of rocks under these conditions is essential for averting accidents and assuring the soundness of engineering projects. Eventually, we discuss vital challenges and future directions in multi-field coupling research, providing valuable insights for engineering applications and addressing allied issues.

Seyed Morteza Davarpanah, Samad Narimani, Mohammad Sharghi et al.

This paper proposes a novel approach to rock mass characterization by adapting the coefficient of uniformity (Cu) and coefficient of curvature (Cc) from soil mechanics, redefining their mathematical formulations to align with RQD-based block size measurements. Specifically, Cu and Cc are calculated using D10, D30, and D60, derived from cumulative RQD data, while accounting for the increasing scale of block size distributions in rock masses. An illustrative case study demonstrates the application of this method, yielding insights into block size variability and heterogeneity in rock masses. The proposed coefficients enrich rock mass classification, offering enhanced quantitative tools for engineering and geological analyses.

Xuefen Cheng, Shuimei Chen

The soil disturbance caused by deep excavation of adjacent buildings will have adverse effects on building foundation. This will threaten the stability of superstructure and engineering safety. In this paper, a three-dimensional finite element model is established by taking the renovation project of underground parking garage near a hotel as an example. The calculated results of the model agree well with the measured data, which verifies the validity of the model. On this basis, the construction mechanical behavior of deep excavation of adjacent buildings is studied. The research content mainly includes the stress and deformation characteristics of soil and structural members. The results show that the stress and deformation characteristics of soil and structural members are sensitive to the excavation depth of deep excavation. It increases with the increase of excavation depth. The vertical displacement of soil at the bottom of deep excavation is mainly uplift. When the excavation is completed, the maximum uplift value is 26.9 mm. The displacement of strip foundation is mainly settlement. The maximum vertical displacement of the foundation of buildings A and B is − 5.2 mm and − 10.98 mm, respectively. In general, the vertical displacement of column foot shows the deformation law of “slope”. The maximum displacements of diaphragm wall 1 and 2 are 6.09 mm and − 6.56 mm respectively. The maximum values of XX direction stress and YY direction bending moment are − 494.2 kN/m and − 746.1 kN m/m, respectively. The axial force of the internal support is mainly pressure. The maximum value is − 1225.9 kN. The total maximum axial force shows a trend of “increasing”. When the excavation is completed, the total maximum axial force is − 2748.3 kN. The deformation and internal force distribution of soil and structural members at the bottom of deep excavation have obvious spatial characteristics. The closer to the center of the deep excavation, the greater the value. Therefore, attention should be focused and necessary measures should be taken. For the renovation of the underground parking garage near the hotel, based on the modified Mohr Coulomb constitutive model, the three-dimensional finite element model is established by MIDAS/GTS software. And the numerical calculation is carried out. The reliability of the model is verified by comparing the numerical results with the measured results. The construction mechanics behavior of underground parking garage renovation project near existing buildings is studied. The research content mainly includes the stress and deformation characteristics of soil and structural members. For the renovation of the underground parking garage near the hotel, based on the modified Mohr Coulomb constitutive model, the three-dimensional finite element model is established by MIDAS/GTS software. And the numerical calculation is carried out. The reliability of the model is verified by comparing the numerical results with the measured results. The construction mechanics behavior of underground parking garage renovation project near existing buildings is studied. The research content mainly includes the stress and deformation characteristics of soil and structural members.

Hongying Wang, Qiang Zhang, Richeng Liu et al.

Rock joints always have a smaller strength, and it plays an important influence on the overall strength of rock mass. The mechanical behavior of rock joints is mainly governed by the surface topography, normal stress, and failure degree. In this study, a series of direct shear tests for four different rough rock joints under five normal stresses was carried out. The shear and normal stiffnesses were first determined, and the shear shrinkage effect was represented by a shear-normal coupling coefficient. Assuming that the strength of the joint is composed of frictional and cohesive parts, the evolutions of cohesion, friction angle with joint roughness coefficient (JRC), and plastic shear displacement are obtained. The dilatancy behavior is described by the dilation angle, which is considered a function of JRC, plastic shear displacement, and normal stress. A cohesive-frictional elastoplastic constitutive model is hence proposed. The theoretical curves under constant normal stress conditions of the proposed model are in good agreement with the experimental results. The shear behaviors under constant normal stiffness and constant normal displacement conditions can be predicted using the new constitutive model.

Muneera Bano, Hashini Gunatilake, Rashina Hoda

Large language models (LLMs) have rapidly gained popularity and are being embedded into professional applications due to their capabilities in generating human-like content. However, unquestioned reliance on their outputs and recommendations can be problematic as LLMs can reinforce societal biases and stereotypes. This study investigates how LLMs, specifically OpenAI's GPT-4 and Microsoft Copilot, can reinforce gender and racial stereotypes within the software engineering (SE) profession through both textual and graphical outputs. We used each LLM to generate 300 profiles, consisting of 100 gender-based and 50 gender-neutral profiles, for a recruitment scenario in SE roles. Recommendations were generated for each profile and evaluated against the job requirements for four distinct SE positions. Each LLM was asked to select the top 5 candidates and subsequently the best candidate for each role. Each LLM was also asked to generate images for the top 5 candidates, providing a dataset for analysing potential biases in both text-based selections and visual representations. Our analysis reveals that both models preferred male and Caucasian profiles, particularly for senior roles, and favoured images featuring traits such as lighter skin tones, slimmer body types, and younger appearances. These findings highlight underlying societal biases influence the outputs of LLMs, contributing to narrow, exclusionary stereotypes that can further limit diversity and perpetuate inequities in the SE field. As LLMs are increasingly adopted within SE research and professional practices, awareness of these biases is crucial to prevent the reinforcement of discriminatory norms and to ensure that AI tools are leveraged to promote an inclusive and equitable engineering culture rather than hinder it.

Daiqiang Deng, Buxian Li, Yunfei Yang et al.

Due to early geological movements, the formation of rock layers near the surface of the Earth's crust varied. In the later stages, intact rock layers were repeatedly subjected to external forces, resulting in varying degrees of damage. Additionally, during physical and chemical weathering, the properties of soil and rock materials in different regions of the Earth's surface showed certain differences. Therefore, in civil engineering construction, it is necessary to test the performance indicators of soil and rock in different regions in order to provide reliable basis for civil engineering design and construction. As an important physical property index of geotechnical materials, the testing process of soil moisture content is prone to some human or instrument equipment problems, which can affect the reliability of moisture content index determination. In the teaching of soil mechanics physical and mechanical performance index experimental courses in various higher education institutions, it is necessary to guide students to take some technical measures in testing experiments, enhance the sense of responsibility and standardized operation of testing personnel, and by formulating experimental plans and guidance documents, while following the various operational requirements of geotechnical testing regulations, accurately judge the type of rock and soil, correctly collect experimental samples, standardize the use of instruments and equipment, carry out experiments step by step, accurately weigh, scientifically read, set reasonable drying times, and use multiple sets of data averages. For the testing of moisture content indicators of special soil types in some areas, specialized methods can be used for experimental operations to avoid human operation errors and minimize experimental errors, thereby achieving ideal and efficient soil mechanics experimental goals.

Seyed Mostafa Emadi Baladehi

Introduction Landfill leachate, a liquid resulting from waste decomposition, contains nutrients like ammoniacal-N, Na, K, and organic matter. Biological treatments effectively remove degradable organics from young landfill leachate, but aged leachate with recalcitrant organics requires combined physical-chemical and biological methods or advanced technologies, leading to higher treatment costs. Even after treatment, leachate may not meet environmental standards for release. In arid and semi-arid regions with water scarcity and low soil organic matter, leachate application to soil presents a potential solution. Soil’s properties enable it to retain and degrade pollutants while utilizing leachate’s nutrients to enhance fertility and crop growth. However, leachate composition and application rates are critical factors due to potential negative impacts from total nitrogen, salinity, and heavy metals. Alkaline pH in aged leachate reduces heavy metal contamination risk. Detailed leachate characterization before soil application is crucial to prevent environmental and functional problems. This review examines existing research on leachate irrigation’s effects on soil properties and plant nutrition, contributing to sustainable leachate management and agricultural practices in water-limited regions. Additionally, the review explores potential risks associated with leachate irrigation, including soil salinization, heavy metal accumulation, and groundwater contamination. By understanding both the benefits and drawbacks, informed decisions can be made regarding the suitability and implementation of leachate irrigation in specific contexts.   Materials and Methods To carry out this study, keywords such as "Landfill leachate", "Composition of landfill leachate" and "Landfill leachate irrigation" were searched in the Web of Science, Google Scholar, ScienceDirect, and SID databases. For these keywords, 205 articles were found from 1989 to 2023. After the screening, quality review, and removal of repetitive and unrelated articles, 110 relevant articles were used. The main criterion for selecting articles was the effects of landfill leachate irrigation on the various properties of soil, and the nutrition of different plant species. The quality of the articles was evaluated through the Scimago Journal Rank (SJR) index, the citation, the Impact Factor, and the source normalized impact per paper (SNIP) index.   Results and Discussion Landfill leachate presents a complex environmental challenge due to its potential for both soil contamination and enrichment. Leachate's xenobiotic and heavy metal components can induce soil contamination, altering the natural environment. Studies have documented reduced hydraulic conductivity, increased gas production, and altered microbial communities, ultimately impacting soil productivity.  Leachate percolation can also modify physicochemical characteristics, including reduced microbial biomass, phosphorus-fixing capacity, and pH shifts, depending on waste composition. Conversely, research highlights the potential benefits of leachate application in arid and semi-arid regions facing water scarcity and low soil organic matter. Leachate can contribute to the increased organic content, improved soil structure, and regulated pH, enhancing soil fertility and crop productivity.  The presence of macro and micro-nutrients such as Fe, Mn, N, P, and Zn further supports leachate's potential as a fertilizer. However, concerns remain regarding inhibitory chemicals in leachate and their potential detrimental effects on plant growth and yield. Studies report instances of leaf injury, reduced yield, and poor survival rates in certain plant species.  In contrast, research demonstrates the positive effects of diluted or low-strength leachate application, stimulating plant growth and enhancing yield, particularly for Brassica species and tree species like Acacia confusa, Leucaena leptocephali, and Eucalyptus tortellini. These contradictory findings underscore the intricate interplay of factors influencing leachate irrigation outcomes. Soil characteristics, plant species, leachate source and composition, application methods, and their interactions all play significant roles in determining the success or failure of leachate irrigation. Conclusion Landfill leachate, characterized by its elevated nitrogen and nutrient levels, presents a potential alternative water and fertilizer source for agricultural practices, particularly in arid and semi-arid regions facing water scarcity. However, responsible leachate utilization necessitates a comprehensive approach that balances maximizing benefits with minimizing environmental risks. Prior to agricultural application, detailed leachate characterization is crucial to determine its precise composition and suitability for irrigation. This includes quantifying heavy metal concentrations, salinity levels, and the presence of potentially toxic organic compounds.  Concurrent plant selection is equally important, prioritizing species with demonstrated tolerance to leachate constituents. Given the potential for salinity and heavy metal accumulation, continuous application of raw leachate, especially for sensitive crops, should be avoided. Implementing alternating irrigation regimes with conventional water sources can mitigate these risks while providing essential nutrients for plant growth.  Monitoring soil health indicators, including pH, organic matter content, and microbial activity, is vital to assess long-term impacts and implement necessary soil amendments. Determining optimal leachate application rates requires a multifaceted approach that considers plant-specific nitrogen requirements, leachate toxicity levels, and soil infiltration capacity.  This ensures adequate nutrient supply without exceeding the assimilative capacity of plants and soil, preventing environmental contamination. Further research is needed to investigate the long-term impacts of leachate irrigation on soil health, crop quality, and potential groundwater contamination. Developing standardized guidelines for leachate treatment and application, tailored to specific regional contexts and crop types, is crucial for promoting sustainable and responsible leachate utilization in agriculture.

Koichi Hayashi, Toru Suzuki, Tomio Inazaki et al.

S-wave velocity (Vs) profile or time averaged Vs to 30 m depth (VS30) is indispensable information to estimate the local site amplification of ground motion from earthquakes. We use a horizontal-to-vertical spectral ratio (H/V) of seismic ambient noise to estimate the Vs profiles or VS30. The measurement of H/V is easier, compared to active surface wave methods (MASW) or microtremor array measurements (MAM). The inversion of H/V is non-unique and it is impossible to obtain unique Vs profiles. We apply deep learning to estimate the Vs profile from H/V together with other information including site coordinates, deep bedrock depths, and geomorphological classification. The pairs of H/V spectra (input layer) and Vs profiles (output layer) are used as training data. An input layer consists of an observed H/V spectrum, site coordinates, deep bedrock depths, and geomorphological classification, and an output layer is a velocity profile. We applied the method to the South Kanto Plain, Japan. We measured MASW, MAM and H/V at approximately 2300 sites. The pairs of H/V spectrum together with their coordinates, geomorphological classification etc. and Vs profile obtained from the inversion of dispersion curve and H/V, compose the training data. A trained neural network predicts Vs profiles from the observed H/V spectra with other information. Predicted Vs profiles and their VS30 are reasonably consistent with true Vs profiles and their VS30. The results implied that the deep learning could estimate Vs profile from H/V together with other information.

Arthur Pilone, Paulo Meirelles, Fabio Kon et al.

A central challenge for ensuring the success of software projects is to assure the convergence of developers' and users' views. While the availability of large amounts of user data from social media, app store reviews, and support channels bears many benefits, it still remains unclear how software development teams can effectively use this data. We present an LLM-powered approach called DeeperMatcher that helps agile teams use crowd-based requirements engineering (CrowdRE) in their issue and task management. We are currently implementing a command-line tool that enables developers to match issues with relevant user reviews. We validated our approach on an existing English dataset from a well-known open-source project. Additionally, to check how well DeeperMatcher works for other languages, we conducted a single-case mechanism experiment alongside developers of a local project that has issues and user feedback in Brazilian Portuguese. Our preliminary analysis indicates that the accuracy of our approach is highly dependent on the text embedding method used. We discuss further refinements needed for reliable crowd-based requirements engineering with multilingual support.

Raoni Arroyo, Jonas R. Becker Arenhart

Philosophers of science commonly connect ontology and science, stating that these disciplines maintain a two-way relationship: on the one hand, we can extract ontology from scientific theories; on the other hand, ontology provides the realistic content of our scientific theories. In this article, we will critically examine the process of naturalizing ontology, i.e., confining the work of ontologists merely to the task of pointing out which entities certain theories commit themselves to. We will use non-relativistic quantum mechanics as a case study. We begin by distinguishing two roles for ontology: the first would be characterized by cataloging existing entities according to quantum mechanics; the second would be characterized by establishing more general ontological categories in which existing entities must be classified. We argue that only the first step is available for a naturalistic approach; the second step not being open for determination or anchoring in science. Finally, we also argue that metaphysics is still a step beyond ontology, not contained in either of the two tasks of ontology, being thus even farther from science.

Haodong Xu, Meng Zhang, Zhou Zheng et al.

The frost heaving damage mechanism of fractured rock masses (FRM) is the basis of theoretical research related to rock mechanics in cold regions, and it is also an important factor that must be considered in the investigation, design, construction, and operation and maintenance stages of cold-region rock engineering projects. Despite the great achievements made by scholars worldwide regarding this aspect, it still faces many difficulties and challenges. This paper firstly briefly reviews the development history of research on low-temperature FRM, and clarifies the differences and connections between them and soil and porous media rocks in terms of frost heaving damage mechanism. The progress of research on the frost heaving damage mechanism of FRM is introduced from four aspects of theoretical studies, laboratory experiments, field tests, and numerical simulations. The hotspots and difficulties in the study of FRM under conditions of low temperature and freeze-thaw cycle are summarized, including theoretical solution method of frost heaving force, migration law of water in the fracture and matrix, and crack expansion law, and numerical simulation method, etc. Finally, an outlook on the future development directions of this field is provided, with emphasis on the importance of the investigation on ice-rock properties, water migration, etc., to improve the existing research results and further expand future research directions.

Zhicheng Liu, Jianmei Liu, Muyu Li et al.

The stability of underground diaphragm walls is crucial for ensuring the safety and integrity of trench excavations in geotechnical engineering. This study addresses this critical issue by proposing a novel destabilization mechanism based on a sliding body model specifically designed for diaphragm wall trenching operations. The research employs an analytical framework rooted in soil mechanics and plasticity theory, utilizing limit equilibrium analysis to develop a method for calculating the minimum required slurry density and corresponding safety factor for trench stability. The study compares two distinct approaches to slurry density computation, analyzing their sensitivity to various influencing factors. Theoretical findings are validated through multiple real-world engineering case studies. Comparative analysis demonstrates the superiority of the proposed method, particularly in assessing trench stability within clay layers. Key variables influencing the safety factor are identified, including trench length, slurry density, soil friction angle, and the relative height difference between slurry and groundwater levels. Results indicate that actual slurry densities observed in practice consistently fall within the bounds predicted by the theoretical calculations. This research contributes a valuable theoretical framework to the field of diaphragm wall construction, offering improved accuracy in stability assessments and potentially enhancing safety in geotechnical engineering projects.

MA Dongdong 1, 2, 3, 4, WANG Xinpeng 2, 3, ZHANG Wenpu 2, 3, MA Qinyong 1, 2, 3, ZHOU Zhiwei 4, ZHANG Rongrong 1, 2, 3

The dynamic tensile strength and failure characteristics of frozen soils have important reference value in the field of efficient crushing and safety stability analysis of frozen soil projects. To study the effects of negative temperature and loading rate on the dynamic tensile properties of the frozen soils, the aluminum split Hopkinson pressure bar system is employed to conduct the dynamic Brazilian disc splitting test of frozen soil. In addition, by using the high-speed camera system, the influences of temperature and loading rate on the dynamic tensile strength, energy dissipation and failure mode of the frozen soils are analyzed. Finally, the splitting failure mechanism of the Brazilian disc and the influencing factors of dynamic tensile strength of the frozen soils are discussed. The results indicate that under the dynamic loads, the Brazilian disc specimens of frozen clay and frozen sand follow the central initiation failure mode, and the specimens are split into two relatively intact halves along the axial direction. With the increase of the impact pressure, the loading rate of two frozen soil types increases linearly, and the duration required for reaching the dynamic tensile peak stress for them is in the range of 92~242 μs. The dynamic tensile strength of the frozen soils shows the obvious temperature effects and loading rate effects, and its values increase with the decrease of the temperature and the increase of the loading rate. There is a good linear relationship between the absorbed energy and the dynamic tensile strength of the frozen soils under various negative temperature conditions. With the increase of the impact pressure, the damage degree of the frozen soil specimens is aggravated, and the triangular fracture zone area caused by high shear stress gradually increases.

Changgui Jia, Bo Xiao, Lijun You et al.

Through the stimulation method of large-scale hydraulic fracturing, the spontaneous imbibition capacity of the water phase in the shale reservoir has great influence on the effect of stimulation. Generally, the lacustrine shale has the characteristics of high clay minerals content, strong expansibility, development of nanopores and micro-pores, and underdevelopment of fractures, which leads to the unclear behavior of spontaneous imbibition of aqueous phase. The lacustrine shale of Da'anzhai Member and marine shale of Longmaxi Formation in Sichuan Basin were selected to prepare both the shale matrix sample and fractured shale sample, and the spontaneous imbibition experiment of simulated formation water was carried out. By means of an XRD test, SEM observation, nuclear magnetic resonance test and linear expansion rate test, the mineral composition, the structure of pores and fractures, the capacity of hydration and expansion of both lacustrine and marine shale are compared and analyzed. The results show that the average spontaneous imbibition rate of lacustrine shale is 60.8% higher than that of marine shale within the initial 12 hours of imbibition. The lacustrine shale has faster imbibition rate than the marine shale in the initial stage of spontaneous imbibition. However, the lacustrine shale has underdeveloped pores and fractures, as well as poor connectivity of pores. Besides, the strong hydration and expansion of clay minerals can easily lead to dispersion and migration of clay minerals on the fracture surface, which will plug up the seepage channels, resulting in poor capacity of spontaneous imbibition. The spontaneous imbibition rate in the middle and late stage of Lacustrine shale is obviously lower than that of the marine shale. The overall spontaneous imbibition rate ability of the lacustrine shale is less than that of the marine shale. According to the characteristics of water imbibition of lacustrine shale, considering the dual effects of hydration expansion of clay minerals on the effective reconstructed volume, the microfractures can be initiated and extended by fully utilizing the hydration of shale. Acidification treatment, oxidation treatment or high temperature treatment can be used to expand pore space, enhance water phase imbibition capacity and improve multi-scale mass transfer capacity of the lacustrine shale.

XUE Xiuli , LIAO Huan , ZENG Chaofeng , LIU Yunsi , ZENG Xing

When a foundation pit is adjacent to the existing underground structures, the groundwater seepage and ground movement caused by dewatering will be blocked by the underground structures (i.e., the water- and soil-blocking effects). On this occasion, the deformations of the foundation pit with or without adjacent underground structures should be different. A pumping test is carried out based on an actual project, and the variations of water levels and the deformations of retaining walls and soils induced by pumping are measured. Thus, a three-dimensional fluid-solid coupling model is established to simulate the dewatering of a foundation pit considering the effect of adjacent underground structures. The distance between the foundation pit and the existing underground structures (D) and the dewatering depth (Hd) are selected as the two varying parameters in the numerical model to investigate the barrier effects of the adjacent underground structures on the deformation of the foundation pit caused by pumping. It is found that when D is small (e.g., D < 20 m), the soil-blocking effects play a leading role, reducing the ground settlement outside the pit (compared with the condition without the underground structures outside the pit). When D is large (e.g., D > 20 m), the water-blocking effects play a leading role, increasing the ground settlement outside the pit. However, with the further increase of D (e.g., D > 40 m), both the water- and soil-blocking effects gradually decrease, and the distribution of the ground settlement outside the pit tends to be similar to that without the underground structures. In the design of foundation pits, the coupling actions of the water- and soil-blocking effects of the adjacent underground structures should be considered so that more accurate calculation of the ground losses and wall deflections will be achieved, which is helpful to optimize the design of the foundation pits.

Oluwasanmi Olabode, Pelumi Adewunmi, Odera Uzodinma et al.

Gas cap blow down strategy is normally deployed for Ultra-thin oil rim reservoirs with huge gas caps due to extremely high gas oil ratios from wells in such reservoirs. The current state leads to loss of production from the oil reserves due to high initial reservoir pressure thus, reducing its net present value. Data on important factors essential to the productivity of oil rim reservoirs are used to build a heterogeneous ultra-thin reservoir with a time step of 10,000 days using the Eclipse software and its embedded correlations. The reservoir is subjected to a gas cap blowdown via a gas well, then an oil well is initiated into the model at onset and after time periods of 2000 days, 4000 days, 6000 days and 8000 days to estimate the oil recovery. It is expected that due to the large nature of the gas cap, pressure decline will be drastic and leading to a low oil recovery, hence the injection of water and gas at different rates at the periods indicated. The results indicate an oil recovery of 4.3% during gas cap blow down and 10.34% at 6000 days. Peak oil recoveries of 12.64% and 10.80% are estimated under 30,000 Mscf/day at 4000 days and 1000 stb/day at 6000 days respectively. This shows an incremental oil recovery of 8.34% and 6.5% over that recorded during gas cap blow down. The results also indicate that the gas production at those periods was not greatly affected with an estimated increment of 257 Bscf recorded during 30,000 Mscf/day at 4000 days. All secondary injection schemes at the respective time steps had positive impact on the overall oil recoveries. It is recommended that extra production and injection wells be drilled, enhanced oil recovery options and injection patterns be considered to further increase oil recovery.

Yang Ge, Qingping Li, Xin Lv et al.

To facilitate the recovery of natural gas hydrate (NGH) deposits in the South China Sea, we have designed and developed the world's largest publicly reported experimental simulator for NGH recovery. This system can also be used to perform CO2 capture and sequestration experiments and to simulate NGH recovery using CH4/CO2 replacement. This system was used to prepare a shallow gas and hydrate reservoir, to simulate NGH recovery via depressurization with a horizontal well. A set of experimental procedures and data analysis methods were prepared for this system. By analyzing the measurements taken by each probe, we determined the temperature, pressure, and acoustic parameter trends that accompany NGH recovery. The results demonstrate that the temperature fields, pressure fields, acoustic characteristics, and electrical impedances of an NGH recovery experiment can be precisely monitored in real time using the aforementioned experimental system. Furthermore, fluid production rates can be calculated at a high level of precision. It was concluded that (1) the optimal production pressure differential ranges from 0.8 to 1.0 MPa, and the wellbore will clog if the pressure differential reaches 1.2 MPa; and (2) during NGH decomposition, strong heterogeneities will arise in the surrounding temperature and pressure fields, which will affect the shallow gas stratum.

Deng Wang

Whether the first law of black hole mechanics is correct is an important question in black holes physics. Subjected to current limited gravitational wave events, we propose its weaker version that permits a relatively large perturbation to a black hole system and implement a simple test with the first event GW150914. Confronting the strain data with the theory, we obtain the constraint on the deviation parameter $α=0.07\pm0.11$, which indicates that this weaker version is valid at the 68\% confidence level. This result implies that the first law of black hole mechanics may be correct.

Jie JW Wu

Machine learning (ML) components are being added to more and more critical and impactful software systems, but the software development process of real-world production systems from prototyped ML models remains challenging with additional complexity and interdisciplinary collaboration challenges. This poses difficulties in using traditional software lifecycle models such as waterfall, spiral, or agile models when building ML-enabled systems. In this research, we apply a Systems Engineering lens to investigate the use of V-Model in addressing the interdisciplinary collaboration challenges when building ML-enabled systems. By interviewing practitioners from software companies, we established a set of 8 propositions for using V-Model to manage interdisciplinary collaborations when building products with ML components. Based on the propositions, we found that despite requiring additional efforts, the characteristics of V-Model align effectively with several collaboration challenges encountered by practitioners when building ML-enabled systems. We recommend future research to investigate new process models, frameworks and tools that leverage the characteristics of V-Model such as the system decomposition, clear system boundary, and consistency of Validation & Verification (V&V) for building ML-enabled systems.