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

Wenhao Wang, Xiang He, Shifan Wu et al.

Microbial induced carbonate precipitation (MICP) and enzyme induced carbonate precipitation (EICP) processes can be affected by many factors. The influence of magnesium on the MICP and EICP based soil improvement was studied in this paper across different scales ranging from micro, pore to macro. Results obtained from microfluidic chip tests indicate that the presence of a little amount of Mg ions in the cementation solution can reduce the bacterial cell coagulation and promote a more uniform distribution of crystals in the reaction channel. Aqueous phase tests were performed by controlling the concentration of calcium (Ca) to magnesium (Mg) ratio to vary from 1.00 : 0 to 0 : 1.00. The results show that magnesium could delay the precipitation process and increase the quantity of the precipitates. As the magnesium content increases, the crystal morphology of precipitates changes from calcite to Mg-calcite, vaterite, rosette and nesquehonite. Cementation effect in the Ca-rich group is superior to that in the Mg-rich group. In terms of unconfined compressive strength of the treated sand, the contribution of Mg is much less significant in Mg-rich groups. The performance of the sand treated with both MICP and EICP based methods under the presence of Mg was evaluated and discussed. All samples exhibited strength improvement after biotreatments. Among all the four groups, the EICP 1-phase group with Ca: Mg of 0.90 : 0.10 and 0.75 : 0.25 exhibited the largest strengths of 4.5 MPa and 4.7 MPa, respectively.

Hongru Li, Manchao He, Yingming Xiao et al.

In this study, based on the rockburst disaster mechanism of excess energy ΔE > 0, true triaxial transient unloading strainburst (including instantaneous strainburst and delayed strainburst) experiments were performed on granite specimens at different maximum principal stress levels. The experimental results were then analyzed, with the strainburst characteristics and acoustic emission (AE) responses of the granite specimens being examined. The excess energy ΔE was derived through a comparison with the results of conventional biaxial compression tests. The following beneficial conclusions were drawn. The mechanical strength of delayed strainburst specimens initially increases and then decreases with the rise of the unloading stress level. In contrast, the mechanical strength of instantaneous strainburst specimens is higher than that of delayed ones, increasing with the unloading stress level. In terms of fragment ejection velocity and scale, the rockburst intensity of a specimen is positively correlated with its mechanical strength. A pronounced linear relationship exists between the excess energy ΔE and the fragment ejection velocity (as well as weight), indicating that ΔE is intimately linked to the kinetic energy of rockbursts. Rockbursts lead to the formation of burst pits and typical V-shaped damage zones near the free face of the specimens, within which tensile cracks dominate. Additionally, the distribution of AE AF-RA values indicates that the proportion of tensile cracks increases with the rise of unloading stress level, suggesting that transient unloading under high stress levels significantly promotes tensile fracture. It is anticipated that this study will provide further elucidation on the mechanism of rockburst kinetic energy generation, thereby establishing a foundation for the design of rockburst support measures in engineering applications.

Alejandro L. Garcia

This paper presents a perspective in which Direct Simulation Monte Carlo (DSMC) is viewed not in its traditional role as an algorithm for solving the Boltzmann equation but as a numerical method for statistical mechanics. First, analytical techniques such as the collision virial and Green-Kubo relations, commonly used in molecular dynamics, are used to study the numerical properties of the DSMC algorithm. The stochastic aspect of DSMC, which is often viewed as unwanted numerical noise, is shown to be a useful feature for problems in statistical physics, such as Brownian motion and thermodynamic fluctuations. Finally, it is argued that fundamental results from statistical mechanics can provide guardrails when applying machine learning to DSMC.

Jan Eliáš, Gianluca Cusatis

This article answers the question of whether homogenization of discrete fine-scale mechanical models, such as particle or lattice models, gives rise to an equivalent continuum that is of Cauchy-type or Cosserat-type. The study employs the machinery of asymptotic expansion homogenization to analyze discrete mechanical models with rotational degrees of freedom commonly used to simulate the mechanical behavior of heterogeneous solids. The proposed derivation has general validity in both stationary (steady-state) and transient conditions (assuming wavelength much larger that particle size) and for arbitrary nonlinear, inelastic fine-scale constitutive equations. The results show that the unit cell problem is always stationary, and the only inertia term appears in the linear momentum balance equation at the coarse scale. Depending on the magnitude of the local bending stiffness, mathematical homogenization rigorously identifies two limiting conditions that correspond to the Cauchy continuum and the Cosserat continuum. A heuristic combination of these two limiting conditions provides very accurate results also in the transition from one limiting case to the other. Finally, the study demonstrates that cases for which the Cosserat character of the homogenized response is significant are associated with non-physically high fine-scale bending stiffness and, as such, are of no interest in practice.

Mohammad Nooraiepour, Krzysztof Polanski, Mohammad Masoudi et al.

Predictive modeling of CO2 storage sites requires a detailed understanding of physico-chemical processes and potential challenges for scale-up. Dramatic injectivity decline may occur due to salt precipitation pore clogging in high-salinity reservoirs, even over a short time frame. This study aims to elucidate the adverse impact of CO2-induced salt crystallization in porous media on the geomechanical properties of near-wellbore reservoir sandstones. As the impact of salt precipitation cannot be isolated from the precursor effects of interaction with CO2 and carbonic acid, we initiated our study by a comprehensive review of CO2 chemo-mechanical interactions with sandstones. We conducted laboratory geochemical CO2-brine-rock interactions at elevated pressures and temperatures on two sets of porous sandstone with contrasting petrophysical qualities. Two paths were followed: treatment with (a) CO2-acidified brine at 10 MPa fluid pressure and 60C for 7 days, and a second subset continuation with (b) supercritical injection until complete dry-out and salt precipitation. Afterward, the core samples were tested in a triaxial apparatus at varying stresses and temperatures. The elastic moduli of intact, CO2-reacted, and salt-damaged sandstones were juxtaposed to elucidate the extent of crystallization damages. The salt-affected specimens showed a maximum of 50 percent reduction in Young's and shear moduli and twice an increase in Poisson's ratio compared to intact condition. The deterioration was notably higher for the tighter rocks with higher initial stiffness.

Johan Cederbladh, Antonio Cicchetti

In this paper we discuss the growing need for system behaviour to be validated and verified (V&V'ed) early in model-based systems engineering. Several aspects push companies towards integration of techniques, methods, and processes that promote specific and general V&V activities earlier to support more effective decision-making. As a result, there are incentives to introduce new technologies to remain competitive with the recently drastic changes in system complexity and heterogeneity. Performing V&V early on in development is a means of reducing risk for later error detection while moving key activities earlier in a process. We present a summary of the literature on early V&V and position existing challenges regarding potential solutions and future investigations. In particular, we reason that the software engineering community can act as a source for inspiration as many emerging technologies in the software domain are showing promise in the wider systems domain, and there already exist well formed methods for early V&V of software behaviour in the software modelling community. We conclude the paper with a road-map for future research and development for both researchers and practitioners to further develop the concepts discussed in the paper.

Mathis Caprais, Oriane Shviro, Ugo Pensec et al.

Modeling underground temperatures provides a practical application of the one-dimensional heat equation. In this work, the one-dimensional heat equation in surface soil is extended to include heat carried by the vertical flow of rainwater through the soil. Analytical solutions, with and without water flow, illustrate the influence of rainwater circulation on the sub-surface propagation of seasonal temperature variations, an important effect that is generally neglected in textbooks. The surface temperature variations are damped by the soil, and this effect was used by the Troglodytae in Egypt or the Petra in South Jordan to insulate against extreme temperatures. For a realistic case of horizontally layered geology, a finite difference Python code was developed for the same purpose. Subsurface temperatures were also measured over a full year at depths up to 1.8 m and used to estimate the thermal skin depth and thermal wavelength. This study provides students with a practical example of how a textbook physics problem can be modified to extract information of contemporary importance in geophysics and global warming.

Oleksandr Kosenkov, Michael Unterkalmsteiner, Jannik Fischbach et al.

Context: Regulatory acts are a challenging source when eliciting, interpreting, and analyzing requirements. Requirements engineers often need to involve legal experts who, however, may often not be available. This raises the need for approaches to regulatory Requirements Engineering (RE) covering and integrating both legal and engineering perspectives. Problem: Regulatory RE approaches need to capture and reflect both the elementary concepts and relationships from a legal perspective and their seamless transition to concepts used to specify software requirements. No existing approach considers explicating and managing legal domain knowledge and engineering-legal coordination. Method: We conducted focus group sessions with legal researchers to identify the core challenges to establishing a regulatory RE approach. Based on our findings, we developed a candidate solution and conducted a first conceptual validation to assess its feasibility. Results: We introduce the first version of our Artifact Model for Regulatory Requirements Engineering (AM4RRE) and its conceptual foundation. It provides a blueprint for applying legal (modelling) concepts and well-established RE concepts. Our initial results suggest that artifact-centric RE can be applied to managing legal domain knowledge and engineering-legal coordination. Conclusions: The focus groups that served as a basis for building our model and the results from the expert validation both strengthen our confidence that we already provide a valuable basis for systematically integrating legal concepts into RE. This overcomes contemporary challenges to regulatory RE and serves as a basis for exposure to critical discussions in the community before continuing with the development of tool-supported extensions and large-scale empirical evaluations in practice.

J. K. Furtney, C. Thielsen, W. Fu et al.

SUN De'an

The ground surface soils are almost unsaturated, especially in arid and semi-arid areas, and the engineering problems of unsaturated soils cannot be properly explained and dealt with by the saturated soil mechanics and the relevant experimental means. First the unsaturated degrees of soils are described by low and high suctions, respectively. By reviewing the theory of saturated soil mechanics, the current commonly accepted theories of unsaturated soil mechanics are introduced. Then, the testing methods for measuring the water retention and mechanical behaviors of unsaturated soils in the low suction range are presented. The focus is on the precautions and countermeasures required by the use of ceramic plates and the volume measurement method for unsaturated soils by using the triaxial instruments. The results of the suction-controlled compression, triaxial shear and true triaxial tests are used to illustrate the typical mechanical behaviors of unsaturated soils. After analyzing the coupling characteristics of hydraulic and mechanical behaviors and the factors directly influencing the water-retention curves based on the test results, a coupling model for describing the hydraulic and mechanical behaviors of unsaturated soils is established by the using the elastic-plastic method, and is verified by suction-controlled or measured isotropic compression and triaxial test results. Subsequently, the stress-strain relationships of four typical soils over a wide suction range are given by means of the suction-controlled triaxial test method developed by the author's group in the high suction range. Finally, the measured strength data of two soils over a wide suction range are used to analyze the applicability of various equations for calculating the strength of unsaturated soils.

Manchao He, Tai Cheng, Yafei Qiao et al.

Rockburst is becoming a huge challenge for the utilization of deep underground space. Extensive efforts have been devoted to investigating the rockburst behavior and mechanism experimentally, theoretically, and numerically. The aim of this review is to discuss the novel development and the state-of-the-art in experimental techniques, theories, and numerical approaches proposed for rockburst. The definition and classification of rockburst are first summarized with an in-depth comparison among them. Then, the available laboratory experimental technologies for rockburst are reviewed in terms of indirect and direct approaches, with the highlight of monitoring technologies and data analysis methods. Some key rockburst influencing factors (i.e. size and shape, rock types, stress state, water content, and temperature) are analyzed and discussed based on collected data. After that, rockburst theories and mechanisms are discussed and evaluated, as well as the microscopic observation. The simulation approaches of rockburst are also summarized with the highlight of optional novel numerical methods. The accuracy, stability, and reliability of different experimental, theoretical and numerical approaches are also compared and assessed in each part. Finally, a summary and some aspects of prospective research are presented.

Ci-Jyun Liang, Thai-Hoa Le, Youngjib Ham et al.

Artificial intelligence (AI) and robotics research and implementation emerged in the architecture, engineering, and construction (AEC) industry to positively impact project efficiency and effectiveness concerns such as safety, productivity, and quality. This shift, however, warrants the need for ethical considerations of AI and robotics adoption due to its potential negative impacts on aspects such as job security, safety, and privacy. Nevertheless, this did not receive sufficient attention, particularly within the academic community. This research systematically reviews AI and robotics research through the lens of ethics in the AEC community for the past five years. It identifies nine key ethical issues namely job loss, data privacy, data security, data transparency, decision-making conflict, acceptance and trust, reliability and safety, fear of surveillance, and liability, by summarizing existing literature and filtering it further based on its AEC relevance. Furthermore, thirteen research topics along the process were identified based on existing AEC studies that had direct relevance to the theme of ethics in general and their parallels are further discussed. Finally, the current challenges and knowledge gaps are discussed and seven specific future research directions are recommended. This study not only signifies more stakeholder awareness of this important topic but also provides imminent steps towards safer and more efficient realization.

Amin Manouchehrian, Pinnaduwa H.S.W. Kulatilake

A destressing method for reducing the strainburst risk in burst-prone grounds is suggested. In this method, the rock is destressed by cutting notches at the excavation boundary. First, the concept of the proposed method is described both analytically and numerically. Then, the method is applied to a tunneling problem. Several numerical models are built to study the destressing process and the failure mechanism around a circular tunnel. Results show that when the notch is added to the model, the rock at the tunnel wall is destressed, and the stress concentration zones shift to a farther distance away from the wall. Also, the analysis of the failure zone around the tunnel and the velocity of the failed elements show that the failure in the notched tunnel is less violent compared to that in the tunnel without the notch. Finally, a parametric study is conducted to investigate the influences of the notch dimensions on the stress distribution, deformation, and failures around the tunnel.

XIN Gong-feng 1, 3, ZHOU Hai-zuo 2, 4, ZHANG Wen-liang 1, 3, ZHENG Gang 2, 4, YANG Xin-yu 2, 4, YU Xiao-xuan 2, 4, XU Shi-qian 2, 4

The design of cap in rigid columns, which has been widely used in engineering practice, can avoid the stress concentration at the column top and enhance the performance of composite foundation. However, the effects of the cap on the stability and progressive failure of rigid column-supported embankment is relatively lacking. A finite difference numerical model is established to simulate the behavior of rigid columns with cap. The influences of the cap on the stress and failure mode of the columns under embankment loads are analyzed, and those of different cap sizes on the stability of embankment are compared. The results show that the tensile stress and the bending moment decrease significantly when cap is used, and the critical failure mode is bending failure. Compared with that of the case without cap, the continuous failure of the case with cap is more obvious. An increase in the cap size can effectively reduce the loads on the columns and improve the stability of the embankment, but there is a risk of cap damage. Therefore, it is necessary to estimate the bearing capacity of the cap in the design.

Ma Fangyuan, Wang Hui, Cheng Jiulong et al.

Magnetic remote-reference is the most practical noise suppression method in magnetotelluric data processing.In actual audio-frequency magnetotelluric (AMT) sounding observation, usually the "one with three" or "one with four" acquisition method is used, i.e., acquiring magnetic field of only one site and simultaneously acquiring electric field of multiple sites, without magnetic field data for remote-reference processing.The natural electro-magnetic field in the 5~1 kHz "dead band" range of signal strength is weak, resulting in the impedance in this band to have "outlies".In this paper, we found that the impedance estimated by using the local magnetic field and the local electric field as the reference in the "dead band" will be "upward" and "downward" biased respectively, while the electric field as the remote-reference channel can significantly improve the impedance quality in the "dead band".After processing the measured data of different reference distances, it is found that the effect of the electric field remote-reference processing is better than that of the local magnetic field and the local electric field.And the effect is comparable to that of magnetic field remote-reference.This has practical implications for AMT data processing.

Heng Wang, Junying Hu, Zhi Yang et al.

A highly efficient and environment-friendly scale inhibitor (MA-VA-VS) was synthesized via free radical solution polymerization method, where maleic anhydride (MA), vinyl acetate (VA) and vinyl sulfonate (VS) acted as monomers, while ammonium persulfate was used as initiator. The inhibition performance and the structure as well as properties was characterized using static jar measurement and dynamic test, Fourier transform infrared spectroscopy and thermogravimetric analysis. The surface morphology and composition of scale formed in the solution were examined using scanning electron microscopy and X-ray diffraction, respectively. The binding energies of inhibitor with calcite (104) face were calculated using Materials Studio 2017 (MS) at 323 K.The results show that the inhibition efficiency gradually increases with increasing inhibitor concentration. While as the Ca2+ concentration increases, the efficiency first increases and then decreases. With the increase in temperature or pH, the efficiency generally decreases. It is confirmed that the inhibition efficiency can reach 91.4% when 150 mg/L MA-VA-VS is used in a flow condition. Both the calculated binding energy and inhibition performance evaluation results demonstrate that the scale inhibition performance of MA-VA-VS is better than a commercial scale inhibitor (HPMA). The excellent inhibition performance of this inhibitor is due to its chelation and dispersion properties.

Xiaoqin Song, Dongxin Li, Xiao Sun et al.

In this work, numerical models were developed to investigate the critical inclination of a pipeline to eliminate the water accumulation at the floor of the pipe carrying oil-water fluid. Computational fluid dynamics software was used to establish a geometric model of the pipe with various inclination angles, and a grid-independent verification was conducted to determine a reasonable meshing method. Quantitative relationships were determined between the pipe inclination angle and the affecting factors including the flow velocity, viscosity and the pipe diameter, where the water accumulation would not be able to occur. Generally, the critical inclination angle increases with the fluid flow velocity. The refluxing of water is the key mechanism causing the water accumulation at the bottom of the pipe. In addition to the fluid flow velocity, an increase in fluid viscosity and a decrease in the pipe diameter cause an increase of the critical inclination angle that the water phase can be carried away by oil. The model can be used to determine the critical inclination of pipelines carrying oil-water fluid to cause the water accumulation and the operating conditions that can eliminate the accumulation of water phase at the pipe floor.

Olga A. Nikitenko , Valery V. Ershov

The paper discusses the directions of hydrogeochemical researches used to solve actual problems of the oil and gas industry: assessment of the oil and gas potential of territories, localization of oil and gas trap, prediction of the phase composition of hydrocarbon fields, control the development process of hydrocarbon fields, etc. Based on the literature data, the analysis and systematization of the main hydrogeochemical indicators of groundwater with oil and gas prospecting significance, as well as used already at the stage of development of oil and gas fields, have been carried out. The most efficiency of the application of hydrogeochemical researches in oilfield practice is achieved with the integrated use of various indicators. On the example of researches of the oil and gas potential of Sakhalin Island, it is shown that the hydrogeochemical data of the middle of the 20th century, obtained by outdated chemical analytical methods, cannot always be considered reliable. In this regard, additional researches are required to update the relevant hydrogeochemical data in this region.

Ling Wu, Ludovic Noels

Artificial Neural Networks (NNWs) are appealing functions to substitute high dimensional and non-linear history-dependent problems in computational mechanics since they offer the possibility to drastically reduce the computational time. This feature has recently been exploited in the context of multi-scale simulations, in which the NNWs serve as surrogate model of micro-scale finite element resolutions. Nevertheless, in the literature, mainly the macro-stress-macro-strain response of the meso-scale boundary value problem was considered and the micro-structure information could not be recovered in a so-called localization step. In this work, we develop Recurrent Neural Networks (RNNs) as surrogates of the RVE response while being able to recover the evolution of the local micro-structure state variables for complex loading scenarios. The main difficulty is the high dimensionality of the RNNs output which consists in the internal state variable distribution in the micro-structure. We thus propose and compare several surrogate models based on a dimensionality reduction: i) direct RNN modeling with implicit NNW dimensionality reduction, ii) RNN with PCA dimensionality reduction, and iii) RNN with PCA dimensionality reduction and dimensionality break down, i.e. the use of several RNNs instead of a single one. Besides, we optimize the sequential training strategy of the latter surrogate for GPU usage in order to speed up the process. Finally, through RNN modeling of the principal components coefficients, the connection between the physical state variables and the hidden variables of the RNN is revealed, and exploited in order to select the hyper-parameters of the RNN-based surrogate models in their design stage.

Rodrigo Henrique Barbosa Monteiro, Maurício Ronny de Almeida Souza, Sandro Ronaldo Bezerra Oliveira et al.

Gamification has been used to motivate and engage participants in software engineering education and practice activities. There is a significant demand for empirical studies for the understanding of the impacts and efficacy of gamification. However, the lack of standard procedures and models for the evaluation of gamification is a challenge for the design, comparison, and report of results related to the assessment of gamification approaches and its effects. The goal of this study is to identify models and strategies for the evaluation of gamification reported in the literature. To achieve this goal, we conducted a systematic mapping study to investigate strategies for the evaluation of gamification in the context of software engineering. We selected 100 primary studies on gamification in software engineering (from 2011 to 2020). We categorized the studies regarding the presence of evaluation procedures or models for the evaluation of gamification, the purpose of the evaluation, the criteria used, the type of data, instruments, and procedures for data analysis. Our results show that 64 studies report procedures for the evaluation of gamification. However, only three studies actually propose evaluation models for gamification. We observed that the evaluation of gamification focuses on two aspects: the evaluation of the gamification strategy itself, related to the user experience and perceptions; and the evaluation of the outcomes and effects of gamification on its users and context. The most recurring criteria for the evaluation are 'engagement', 'motivation', 'satisfaction', and 'performance'. Finally, the evaluation of gamification requires a mix of subjective and objective inputs, and qualitative and quantitative data analysis approaches. Depending of the focus of the evaluation (the strategy or the outcomes), there is a predominance of a type of data and analysis.