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

Eduard Enoiu, Jean Malm, Gregory Gay

We explore the concept of folklore within software engineering, drawing from folklore studies to define and characterize narratives, myths, rituals, humor, and informal knowledge that circulate within software development communities. Using a literature review and thematic analysis, we curated exemplar folklore items (e.g., beliefs about where defects occur, the 10x developer legend, and technical debt). We analyzed their narrative form, symbolic meaning, occupational relevance, and links to knowledge areas in software engineering. To ground these concepts in practice, we conducted semi-structured interviews with 12 industrial practitioners in Sweden to explore how such narratives are recognized or transmitted within their daily work and how they affect it. Synthesizing these results, we propose a working definition of software engineering folklore as informally transmitted, traditional, and emergent narratives and heuristics enacted within occupational folk groups that shape identity, values, and collective knowledge. We argue that making the concept of software engineering folklore explicit provides a foundation for subsequent ethnography and folklore studies and for reflective practice that can preserve context-effective heuristics while challenging unhelpful folklore.

Hao Liu, Zenghui Zhao, Qing Ma et al.

Driven by the “dual carbon” strategy, the functionality of coal mine underground reservoirs is transitioning toward multimedia collaborative storage, such as CO2 geological sequestration and strategic energy reserves. The microscopic structures of the coal pillar dams, which are subjected to mining-induced damage and long-term infiltration erosion by highly mineralized mine water, continuously deteriorate over time, posing significant risks to the long-term safety and stability of the reservoirs. This study, based on the Lingxin Coal Mine Underground Reservoir Demonstration Project, employs a multi-technique characterization approach including X-ray diffraction (XRD), scanning electron microscope, nuclear magnetic resonance, and computed tomography to systematically reveal the multiscale collaborative erosion mechanisms of highly mineralized mine water on the mineral composition, crystal structure, and pore development of coal pillar dams. The results indicate: (1) significant concentration-dependent deterioration of mineral composition and crystal structure; kaolinite hydrolysis had a weakening effect on XRD peaks while quartz remained inert; (2) initiation of progressive microstructural damage at boundaries via dissolution/loosening; this damage advanced through layered mineral delamination and pore development (evidenced by NMR T2 broadening), resulting in irreversible void formation with chloride precipitation; (3) formation of pore-throat halite crystals, primarily due to chloride ions (Cl–); these crystals propagated microfractures through salt-expansion stress, establishing a cyclic dissolution–migration–crystallization–cracking process; (4) triggering of accelerated deterioration of the coal matrix owing to prolonged retention; this induced time- and concentration-dependent expansion and interconnection of pore-fracture networks, resulting in geomechanical deterioration.

Heng Liu, Peng Xi, Xihao Yan et al.

As a novel type of pile foundation structure, the strength composite (SC) piles lack a settlement calculation method that accurately reflects the stress diffusion state within the composite soil mass. In this study, based on the multilayer theory, a settlement calculation formula for strength composite (SC) piles is proposed for homogeneous foundations, which accounts for the evolution of the plastic zone in the surrounding soil. This method is then extended to the settlement calculation of SC piles in layered foundations encountered in practical engineering. A corresponding calculation program is also developed. Through comparison with static load tests, recommendations are provided for the form of the soil modulus distribution around the pile and the value of the soil disturbance radius. Finally, the proposed method is applied to case studies of typical engineering sites. The results show that the calculated values agree well with the measured values in both trend and magnitude, reflecting the nonlinear bearing characteristics of the SC pile. The proposed method demonstrates broad applicability and satisfactory engineering accuracy.

Roberto Verdecchia, Justus Bogner

While mastered by some, good scientific writing practices within Empirical Software Engineering (ESE) research appear to be seldom discussed and documented. Despite this, these practices are implicit or even explicit evaluation criteria of typical software engineering conferences and journals. In this pragmatic, educational-first document, we want to provide guidance to those who may feel overwhelmed or confused by writing ESE papers, but also those more experienced who still might find an opinionated collection of writing advice useful. The primary audience we had in mind for this paper were our own BSc, MSc, and PhD students, but also students of others. Our documented advice therefore reflects a subjective and personal vision of writing ESE papers. By no means do we claim to be fully objective, generalizable, or representative of the whole discipline. With that being said, writing papers in this way has worked pretty well for us so far. We hope that this guide can at least partially do the same for others.

Peiwei Xiao, Xingguo Yang, Biao Li et al.

Ensuring the stability of the surrounding rock mass is of great importance during the construction of a large underground powerhouse. The presence of unfavorable structural planes within the rock mass, such as faults, can lead to substantial deformation and subsequent collapse. A series of in situ experiments and discrete element numerical simulations have been conducted to gain insight into the progressive failure behavior and deformation response of rocks in relation to controlled collapse scenarios involving gently inclined faults. First, the unloading damage evolution process of the surrounding rock mass is characterized by microscopic analysis using microseismic (MS) data. Second, the moment tensor inversion method is used to elucidate the temporal distribution of MS event fracture types in the surrounding rock mass. During the development stage of the collapse, numerous tensile fracture events occur, while a few shear fractures corresponding to structural plane dislocation precede their occurrence. The use of the digital panoramic borehole camera, acoustic wave test, and numerical simulation revealed that gently inclined faults and deep cracks at a certain depth from the cavern periphery are the primary factors contributing to rock collapse. These results provide a valuable case study that can help anticipate and mitigate fault-slip collapse incidents while providing practical insights for underground cave excavation.

Xiao Wang, Wenbin Sun, Changdi He et al.

Abstract This study explored the dynamic behaviors and fracturing mechanisms of flawed granite under split‐Hopkinson pressure bar testing, focusing on factors like grain size and flaw dimensions. By means of digital image processing and the discrete element method, Particle Flow Code 2D (PFC2D) models were constructed based on real granite samples, effectively overcoming the limitations of prior studies that mainly relied on randomized parameters. The results illustrate that the crack distribution of granite is significantly influenced by grain size and flaw dimensions. Tension cracks predominate and mineral boundaries, such as between feldspar and quartz, become primary crack sites. Both flaw length and width critically affect the crack density, distribution, and dynamic strength of granite. Specifically, dynamic strength tends to decrease with the enlargement of flaws and increase with an increase in flaw angles up to 90°.

Bei Zhang, Yandong Bi, Yu Huang

Coriolis effects, encompassing the dilative, compressive, and deflective manifestations, constitute pivotal considerations in the centrifugal modelling of high-speed granular run-out processes. Notably, under the deflective Coriolis condition, the velocity component parallel to the rotational axis exerts no influence on the magnitude of Coriolis acceleration. This circumstance implies a potential mitigation of the Coriolis force's deflective impact. Regrettably, extant investigations predominantly emphasize the dilative and compressive Coriolis effects, largely neglecting the pragmatic import of the deflective Coriolis condition. In pursuit of this gap, a series of discrete element method (DEM) simulations have been conducted to scrutinize the feasibility of centrifugal modelling for dry granular run-out processes under deflective Coriolis conditions. The findings concerning the deflective Coriolis effect reveal a consistent rise in the run-out distance by 2%–16%, a modest increase in bulk flow velocity of under 4%, and a slight elevation in average flow depth by no more than 25%. These alterations display smaller dependence on the specific testing conditions due to the granular flow undergoing dual deflections in opposing directions. This underscores the significance and utility of the deflective Coriolis condition. Notably, the anticipated reduction in error in predicting the final run-out distance is substantial, potentially reaching a 150% improvement compared to predictions made under the dilative and compressive Coriolis conditions. Therefore, the deflective Coriolis condition is advised when the final run-out distance of the granular flow is the main concern. To mitigate the impact of Coriolis acceleration, a greater initial height of the granular column is recommended, with a height/width ratio exceeding 1, as the basal friction of the granular material plays a crucial role in mitigating the deflective Coriolis effect. For more transverse-uniform flow properties, the width of the granular column should be as large as possible.

Yvonne Dittrich, Helen Sharp, Cleidson de Souza

Ethnography has become one of the established methods for empirical research on software engineering. Although there is a wide variety of introductory books available, there has been no material targeting software engineering students particularly, until now. In this chapter we provide an introduction to teaching and learning ethnography for faculty teaching ethnography to software engineering graduate students and for the students themselves of such courses. The contents of the chapter focuses on what we think is the core basic knowledge for newbies to ethnography as a research method. We complement the text with proposals for exercises, tips for teaching, and pitfalls that we and our students have experienced. The chapter is designed to support part of a course on empirical software engineering and provides pointers and literature for further reading.

Javad Ghorbanian, Nicholas Casaprima, Audrey Olivier

In recent years, neural networks (NNs) have become increasingly popular for surrogate modeling tasks in mechanics and materials modeling applications. While traditional NNs are deterministic functions that rely solely on data to learn the input--output mapping, casting NN training within a Bayesian framework allows to quantify uncertainties, in particular epistemic uncertainties that arise from lack of training data, and to integrate a priori knowledge via the Bayesian prior. However, the high dimensionality and non-physicality of the NN parameter space, and the complex relationship between parameters (NN weights) and predicted outputs, renders both prior design and posterior inference challenging. In this work we present a novel BNN training scheme based on anchored ensembling that can integrate a priori information available in the function space, from e.g. low-fidelity models. The anchoring scheme makes use of low-rank correlations between NN parameters, learnt from pre-training to realizations of the functional prior. We also perform a study to demonstrate how correlations between NN weights, which are often neglected in existing BNN implementations, is critical to appropriately transfer knowledge between the function-space and parameter-space priors. Performance of our novel BNN algorithm is first studied on a small 1D example to illustrate the algorithm's behavior in both interpolation and extrapolation settings. Then, a thorough assessment is performed on a multi--input--output materials surrogate modeling example, where we demonstrate the algorithm's capabilities both in terms of accuracy and quality of the uncertainty estimation, for both in-distribution and out-of-distribution data.

Luming Zhou, Zhende Zhu

Thermal damage and thermal fracture of rocks are two important indicators in geothermal mining projects. This paper investigates the effects of heating and water-cooling on granite specimens at various temperatures. The laboratory uniaxial compression experiments were also conducted. Then, a coupled thermo-mechanical ordinary state-based peridynamic (OSB-PD) model and corresponding numerical scheme were developed to simulate the damage of rocks after the heating and cooling processes, and the change of crack evolution process was predicted. The results demonstrate that elevated heating temperatures exacerbate the thermal damage to the specimens, resulting in a decrease in peak strength and an increase in ductility of granite. The escalating occurrence of thermal-induced cracks significantly affects the crack evolution process during the loading phase. The numerical results accurately reproduce the damage and fracture characteristics of the granite under different final heating temperatures (FHTs), which are consistent with the test results in terms of strength, crack evolution process, and failure mode.

Ferri Hassani, Pejman M. Nekoovaght, Nima Gharib

Tao Yu, Haixiang Hu, Qi Li et al.

Kaiwei Tian, Zhu Zeqi, Sheng Qian

In this paper, we propose a new simulation method based on peridynamic for quasi-static fracture propagation in isotropic and transverse isotropic rocks. The new method is based on coupled peridynamic least square minimization and finite element method (PDLSM-FEM). The original isotropic elastic PDLSM-FEM is further extended to a transverse isotropic model, which can analyze the elastic deformation and fracture propagation of transverse isotropic rocks. The proposed model naturally employs transverse isotropic Hooke's law to calculate the internal force. To break the bond and characterize crack propagation, a new bond stretch failure criterion is also presented. The elastic deformation of a transverse isotropic plate with a hole and fracture propagation in a transverse isotropic rock under semi-circular bending (SCB) tests are simulated and compared to finite element method (FEM) results and experimental data, respectively. It is demonstrated that the presented model is capable of modeling transverse isotropic rock elastic deformation and fracture propagation in isotropic SCB specimens and transverse isotropic specimens subjected to SCB tests. There are many sedimentary rocks in nature, such as shale and coal, which should be regarded as transverse isotropic materials because of their interior transverse isotropic structures formed by geological deposition. Fracture propagation is important in the failure process of rocks and has a great influence on the stability of underground excavation, efficiency of hydraulic fracture and other geotechnical engineering applications (Xie et al., 2017). Given the distinctions in fracture propagation patterns between transverse isotropic and isotropic rocks, a thorough understanding of the inner mechanism of fracture propagation in isotropic rocks and transverse isotropic rocks is fundamental in rock engineering. Several computational approaches, such as the extended finite element method (XFEM) (Motamedi, 2010) and phase field method (PFM) (Wang, 2020), have been developed in recent years to investigate crack propagation in isotropic and transverse isotropic materials. These approaches, however, are based on classical (local) continuum mechanics (CCM) and need extra processing strategies for dealing with fractures. Peridynamic (PD) theory (Silling, 2000) is a type of non-local theory, which could naturally simulate fracture propagation since its governing equations are integral equations rather than partial differential equations. Bond-based theory (Silling, 2000), ordinary state-based theory (Silling et al., 2007), and non-ordinary state-based theory (Warren et al., 2009) are the three main types of PD theory. Bond-based PD has a fixed Poisson's ratio, but the other two types have no restriction. The advantage of NOSB PD is evident, since it inherits PD's capability of dealing with cracks while permitting implementations of stress and strain the same as CCM. However, the traditional NOSB PD is computationally expensive and suffers from numerical oscillation. To overcome those limitations, coupled PD least squares minimization and FEM (PDLSM-FEM) (Liu, 2021a) model have been proposed. In light of these concerns, we use the PDLSM-FEM theory as the foundation in this paper for simulating elastic deformation and fractures propagation in isotropic and transverse isotropic rocks.

Jie Xu, Ying Liang, Zhenchao Zhang et al.

Objective Dissolved organic matter (DOM) is an important carbon source in the biogeochemical process of groundwater. Methods To reveal the impact of the seasonal variation in DOM on the migration and transformation in groundwater on N in the Jianghan Plain, long-term water level and hydrochemical data of groundwater and surface water at the Shahu monitoring site were obtained, and the hydrogeochemistry analysis was carried out. The seasonal variation characteristics of DOM were analysed by combing with three-dimensional fluorescence spectroscopy and UV-V is spectroscopy, to explore the role of DOM in groundwater in N migration and transformation under the influence of hydrological conditions. Results The results show that DOM in groundwater and surface water includes three components: terrestrial humic-like component (C1), microbial tryptophan-like component (C2) and microbial humic-like component (C3). The input of microbial tryptophan-like components increases in dry season and terrestrial humic-like components increase in wet season. The strong reducibility and high dissolved organic carbon(DOC) content of groundwater provide conditions for the nitrate reduction, and low humification and low molecular weight C2 components are preferentially utilized in N migration and transformation. In dry season, the groundwater level decreases, the aquifer is partial to oxidation, the unstable protein-like components quickly degrade and release NH4-N, the nitrification and organic nitrogen mineralization rates are higher, and the denitrification and dissimilatory nitrite reduction to ammonium(DNRA) reaction rates are lower. In the wet season, the groundwater level rises, the aquifer tends to be reductive, and nitrification is inhibited. The presence of a large amount of DOM that is not easy to be degraded reduces the mineralization reaction rate of organic nitrogen in the aquifer, and the denitrification and DNRA processes are promoted. Conclusion In summary, the seasonal variation in DOM in the study area is an important factor in controlling the migration and transformation of N in groundwater.

Debankur Sanyal, Avik Mukherjee, Amin Rahhal et al.

IntroductionCover crop (CC) is an essential tool to improve or maintain soil health, potentially improving cash crop productivity. Several recent reports of cash crop yield reduction following cover cropping necessitated this research to guide efficient CC decisions in the season before corn (Zea mays) or soybean (Glycine max) is to be grown.MethodsTherefore, we designed this multi-year, multi-location study to include the farmers who plant CC following the harvest of a small grain crop, majorly wheat (Triticum aestivum) or oats (Avena sativa), and then grow corn or soybean cash crop in the subsequent season. We also selected the farmers who used a fall CC mix that was winter-terminated, to avoid further complexities. The major objective of this study was to document soil health changes and cash crop yields following CC in eight selected locations around SD for three consecutive CC seasons between 2017-2020. Experimental plots were laid out at the farmer-cooperators’ CC fields, where no cover (NC) ‘control’ was tested against CC in a randomized complete block design (RCBD). Soil samples were analyzed for selected soil health indicators (SHIs): potentially mineralizable nitrogen (PMN), permanganate oxidizable carbon (POXC), soil respiration (SR), soil microbial biomass (SMB), soil nitrate-nitrogen, soil organic matter (SOM), and other basic soil properties (pH, electrical conductivity, etc.); crop and residue biomass were calculated, and cash crop economic yields were measured. Results and discussionNo statistically significant (p<0.05) advantage was found for SHIs or cash crop yields under CC plots compared to NC plots as these fields had healthy soils (long-term no-till was practiced, high SOM levels >30 g kg-1). These findings directed us to investigate hydroclimatological parameters and climatological indices such as accumulated precipitation, standardized precipitation index (SPI), and standardized precipitation-evapotranspiration index (SPEI) for their impact on CC’s influence on cash crop yields. ConclusionOur analyses indicated that hydroclimatology, especially SPEI for the month before CC planting can be used as a tool to guide successful CC decisions, reducing the risk of cash crop yield loss. Further investigations with SPI and SPEI, along with other climatological parameters are needed to explore and design better CC management tools.

Karamat Akhavan Giglou, Milad Kheiry, Hedieh Ahmadpari et al.

Introduction Agriculture has played a vital role in the economy, life, and culture in the civil history of Iranians. In recent years, this sector is the largest consumer of freshwater resources in this country. One of the adaptive ways to deal with the water shortage is the optimal use of water. In the production process of a commodity, different sources of water may be used, and the type of water supply source can play a significant role in the analysis of virtual water trade. In the period of 2016-2018, previous research covered by the Moghan irrigation network has been conducted in the field of physical and economic water productivity indicators estimation of crops. Moreover, in previous studies, only benefit per drop (BPD) and net benefit per drop (NBPD) indices have been used to estimate the economic productivity of agricultural water. Therefore, in this research, the agricultural year 2020-2021 was studied in order to investigate the physical and economical water productivity indicators of crops covered by the Moghan irrigation network.   Materials and Methods The Moghan Plain is located in the northwestern part of Iran, on the west side of the Caspian Sea, and north of Ardabil province, on the border between Iran and the Republic of Azerbaijan. The total area of the Moghan watershed is more than 5545 km2. The altitude of the region is 50 to 600 m above sea level and its climate is semi-arid and moderate. Most of the agricultural farm covered by Moghan's irrigation and drainage network is devoted to cultivating crops such as wheat, barley, seed corn, fodder corn, soybean, rapeseed, rice, tomato, cotton, sugar beet, and peanut. In this research, these products' virtual water content and physical and economic water productivity are investigated. In this research, to complete the previous studies in the aforementioned field, the virtual water content of the studied products has also been investigated. In addition to the BPD and NBPD, the unit virtual water value (UWV) has been studied to further investigate the Moghan irrigation network economic efficiency of water crops.   Results and Discussion The content of gray, blue, green, and white virtual water of the studied crops, sugar beet, tomato, and fodder corn, have the lowest content of gray virtual water among crops. Among the studied crops, fodder corn, tomato, and sugar beet products, respectively, have the highest physical water productivity, and rice, soybean, cotton, and peanut respectively have the lowest physical water productivity. Regarding gross value index per unit of irrigation volume among the studied crops tomatoes, peanuts, fodder corn, barley, and wheat, respectively have the; highest, moreover peanut, tomato, cotton, fodder corn, and sugar beet products, respectively, have the highest net value index per unit of irrigation volume among the studied crops, however, barley, wheat, rice, and grain corn, respectively, have the lowest net value index per unit of irrigation volume among the studied crops. In addition, tomatoes, peanuts, fodder corn, wheat, and barley have the highest index of value per virtual water unit among the studied crops, respectively, while rice has the lowest value index per virtual water unit among the studied crops. According to the BPD index, tomatoes, peanuts, fodder corn, barley, and wheat are the first to fifth priorities for cultivation in the Moghan Plain. The first to fifth priorities for cultivation in the Moghan plain according to the NBPD index are peanuts, tomatoes, cotton, fodder corn, and sugar beet, and based on the UWV index, tomatoes, peanuts, fodder corn, wheat, and barley are the first to fifth priorities.   Conclusion In the current research, the content of virtual water and the amount of physical and economic water productivity of crops covered by the Moghan irrigation network were calculated. The crop per drop (CPD) index of rice shows the last level in the crop year 2020-2021 due to the amount of water consumed and the significant cost. Also, in the analysis of the BPD and NBPD index, this product has the lowest and ninth priority, respectively, and in the current water shortage conditions in the Moghan Plain, there is a need to review the cultivation of this product. Tomatoes and fodder corn have good productivity in all three indices of CPD, BPD, and NBPD in the crop year 2020-2021. In fact, while tomato does not have a low water requirement, measuring the performance of this product shows the high net and gross profit obtained according to the cost of planting and harvesting. The amount of UWV index of wheat, rapeseed, soybean, rice, fodder corn, seed corn, tomato, barley, sugar beet, cotton, and peanut products is 24269, 15644, 18894, 9956, 36279, 17362, 50073, 23010, 21748, 19403, and 45718 rials per m3, respectively. The proposed approaches and models of this research are different depending on whether the index of physical productivity or economic productivity of water is considered in planning and policy-making.

Daniel Regulin, Thomas Aicher, Birgit Vogel-Heuser

For improving flexibility and robustness of the engineering of automated production systems (aPS) in case of extending, reducing or modifying parts, several approaches propose an encapsulation and clustering of related functions, e.g. from the electrical, mechanical or software engineering, based on a modular architecture. Considering the development of these modules, there are different stages, e.g. module planning or functional engineering, which have to be completed. A reference model that addresses the different stages for the engineering of aPS is proposed by AutomationML. Due to these different stages and the integration of several engineering disciplines, e.g. mechanical, electrical/electronic or software engineering, information not limited to one discipline are stored redundantly increasing the effort to transfer information and the risk of inconsistency. Although, data formats for the storage and exchange of plant engineering information exist, e.g. AutomationML, fixed domain specific structures and relations of the information, e.g. for automated material flow systems (aMFS), are missing. This paper presents the integration of a meta model into the development of modules for aMFS to improve the transferability and consistency of information between the different engineering stages and the increasing level of detail from the coarse-grained plant planning to the fine-grained functional engineering.

A. Morgun, I. Met, I. Shevchenko

A significant difference between soils and homogeneous elastic bodies is that under action External loads residual deformations are always concomitant elastic, even at low loads. The sum of residual and elastic deformation is the total deformation of the soil base. The simultaneous presence in the soil of zones operating in both elastic and plastic zones requires the involvement of the theory of elasticity and plasticity to model its behavior [1-4]. It is known that the solution of the mixed problem of the theory of elasticity and the theory of soil plasticity brings the results of sedimentation calculations much closer to reality. The current trend towards automated calculation methods has dramatically changed the priorities towards the need to develop more reliable mathematical models of nonlinearly deformed soil massifs composed of layers with different properties. Urban planning and modern industry require the construction of responsible structures on increasingly complex engineering and geological conditions for which the rational type of foundations are piles. Widespread use of pile foundations requires the development of reliable methods for their calculation in order to obtain reliable design solutions. Therefore, the current stage of development of soil mechanics is characterized by an active transition to new computational models that more fully reflect the nonlinearity of deformation and rheological properties of soils and these issues remain an urgent problem today. The paper uses the numerical method of boundary elements, which emerged as a result of further theoretical development of a wide class of numerical methods, united under the common name of finite element theory. It is based on the existence of a fundamental solution of the boundary value problem, which corresponds to the source function given in the form of the Dirac delta function. The availability of a fundamental solution is very important from a practical point of view for the numerical implementation of the IHE task. A fundamental solution is a partial solution of the Laplace equation for a semi-infinite domain for a potential value of one given at some point. This type of solution is widely used in boundary value problems and is a Green's function or influence function. In the presence of a fundamental solution, finite elements are used to approximate the boundary of the domain, and the apparatus of classical integral equations is applied to the inner part of the domain/

Xingang Bu, Ming Han, Abdulkareem M. AlSofi

This work numerically investigates surfactant effects on spontaneous water imbibition in oil-wet carbonates. An open boundary core-scale imbibition model with 9 × 9 × 10 gridblocks was used in UTCHEM to simulate carbonate core plug exposure to a vast water body. The simulation models were developed based on surfactant-assisted imbibition tests that were conducted in secondary and tertiary oil production modes using Amott cells at 75°C. Capillary and gravity forces were captured by history matching the experiments. Through history matching, the inputs for surfactant adsorption and diffusion, capillary pressure and relative permeability were calibrated. In tertiary mode, the surfactants-assisted imbibition process presents the performance in mixed-wet state rather than oil-wet state, which is governed by wettability alteration. A simulation model for surfactant-assisted imbibition in secondary mode was used to investigate the effects of various factors including interfacial tension (IFT) reduction, wettability alteration, adsorption, volume of surrounding water and capillary force. The simulation results suggest that surfactant-assisted water imbibition in secondary mode is gravity dominant, which is facilitated by both IFT reduction and wettability alteration caused by addition of proper surfactants. Different from water imbibition in water-wet core, it presents vertically dominant oil flow with a hemispherical oil-rich area and uneven remaining oil saturation. It is obvious that sufficient surfactant supply in vast water is required to make effective imbibition, in consideration of surfactant consumption and changes in concentration gradients. This core-scale modeling provides insights of surfactant-assisted imbibition in initially oil-wet carbonates and helps scale up the application in a cost-effective way.

Mingjin Jiang, Akiyoshi Kamura, Motoki Kazama

In liquefaction analyses, liquefaction is conventionally assumed to originate from the vertical propagation of shear waves. However, some field and theoretical evidence has demonstrated that the risk of liquefaction may be induced or increased by surface waves. In this study, the liquefaction characteristics of K0-consolidated granular materials under Rayleigh-wave strain conditions, ideal deformation conditions under the assumption of constant volume, were investigated by the three-dimensional discrete element method (3D DEM). The results indicate that Rayleigh-wave strain conditions combine pure and simple shear modes. As the ratio of the shear strain amplitude to the normal strain amplitude (RSN) increases from 1 to +∞, granular materials tend to have a slower liquefaction rate and higher liquefaction resistance; however, the difference in the undrained responses is negligible when the RSN is less than 1. The distribution of the magnitude and orientation of the contact forces also varies with the RSN, while it is similar when the RSN is less than 1. The degradation of the skeleton structure and the evolution of the structural anisotropy accelerate the liquefaction of granular materials. Moreover, in situations with the same accumulated equivalent strain per cycle, the Rayleigh-wave strain condition with a low RSN value will make granular materials more vulnerable to liquefaction compared with Love- and SH-wave strain conditions.