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

Tao Wang, Chao-Sheng Tang, Bin-Qiang Ouyang et al.

Jiaxing Dong, Peixuan Dai, Wenlian Liu et al.

Disintegrated dolomite slope and tunnel disasters occur frequently due to poor water stability of disintegrated dolomite, primarily in a form of seepage failure. For engineering purposes, it is critical to determine the seepage properties of disintegrated dolomite within the strata. However, conventional experimental methods are time-consuming and expensive and may not be effective in investigating seepage characteristics due to the heterogeneity of disintegrated dolomite. In this study, pore network model (PNM) was established by the computerized tomography (CT) scanning technology to characterize the pores. Meanwhile, the seepage and coefficient of permeability under different inlet stress conditions based on the accurate pore model were realized by linking the commercial image processing software Avizo with the commercial multi-physics modeling package Comsol. The results show that the porosities of severely and completely disintegrated dolomites are 29.17% and 45.37%, respectively. The grade of pore development increases with disintegration grade, which facilitates seepage failure. Severely and completely disintegrated dolomites have the coefficients of permeability of 9.67 × 10−7 m/s and 1.61 × 10−6 m/s, respectively. Under conventional conditions, severely and completely disintegrated dolomites undergo seepage failure above a pressure difference of 6 × 103 Pa and 5 × 103 Pa, respectively. These results are consistent with both in situ water pressure tests in the borehole and laboratory tests with the constant-head method, demonstrating that CT scanning is an effective method for observing fractures and pores in disintegrated dolomite for seepage evaluation.

Milad Davoodi, Salvador Senent, Amin Keshavarz et al.

Tunnel face stability has received increasing research interest over the past few decades. However, computing time-efficient and safe three-dimensional solutions under seismic loading is still an unsolved problem, while case studies indicate that seismic loading can be one critical destabilizing factor affecting tunnel stability. The primary objective of this work is to fill this gap in knowledge by providing compromising and computationally efficient solutions, along with their respective lower and upper bounds, to compute face stability under seismic conditions. The analyses employ the finite element limit analysis method to evaluate the limit support pressure in undrained clay, considering horizontal pseudo-static seismic forces pointing outwards from the face. Moreover, the analyses employ both constant and linearly increasing shear strengths with depth. The results are summarized as dimensionless stability charts and tables to facilitate their interpretation and future use for tunnel design. A new design equation has been developed to evaluate the stability of the tunnel face considering the effect of seismic forces. Additionally, the effects of different parameters on the shape of the failure mechanism have been investigated by analysing the distribution of shear dissipation.

Redouane Meryem, Khalis Hind, Haissen Faouziya et al.

Abstract In the last few decades, addressing the global challenge of implementation of strategies for renewable energy and energy efficiency has become crucial. Morocco, since 2009, has made a steadfast commitment to sustainability, with a particular focus on advancing the development of renewable energy resources. A comprehensive strategy has been formulated, centering on utilizing the country's energy potential to drive progress in this vital sector. Morocco is considered a country with abundant thermal water, indicating deep reservoirs with significant hydrothermal potential. Geothermal zones were selected based on the abundance of hot springs where water temperatures were high and geothermal gradients were significant. The abundance and importance of hot springs, combined with recent volcanism and ongoing non‐tectonic activity linked to alpine orogeny, strongly suggest that these regions are promising reservoirs for geothermal energy. This great potential also extends to neighboring countries. In northeast and south Morocco, the temperature of thermal water ranges from 26 to 54°C. This study serves as an inclusive review of the geothermal potentialities in Morocco.

WANG Manling 1, 2, LI Shuchen 1, 2, 3, ZHOU Huiying 1, 2, WANG Xiuwei 1, 2, PENG Kefeng 1, 2, YUAN Chao 2, 4

The material point method (MPM) has good effects in simulating large deformation problems. However, the conventional MPM suffers from cell-crossing errors when particles cross grid boundaries, resulting in reduced accuracy. In order to overcome the cell-crossing errors of the conventional MPM, an improved convective particle domain interpolation material point method (CPDI) is proposed based on the conventional CPDI framework and the adaptive orthogonal improved interpolation moving least squares method (AOIIMLS). By constructing weighted orthogonal basis functions and disregarding the minimal or zero elements in the new diagonal matrix, the inverse matrix computation is avoided, and the robustness is enhanced. In the improved CPDI method, the particle domain velocity field is calculated using the velocity gradients, and the AOIIMLS shape functions are employed to reconstruct the background grid velocity function using the particle velocity and particle domain corner point velocity. The accuracy and applicability of the improved CPDI method are verified through simulations of various scenarios such as the compaction of a one-dimensional column under self-weight, the collapse of a sand column and the centrifuge tests on tunnel collapse. The results show that the improved CPDI method reduces the cell-crossing errors caused by the particles cross grid boundaries and achieves higher accuracy. Finally, the improved CPDI method is employed to simulate the whole process of ground collapse in the Jinggang Road Station–Shazikou Station tunnel section of Qingdao Metro Line 4, effectively confirming the applicability and advantages of the method in addressing large deformation problems in geotechnical engineering.

Xin Wang, Guo-qiang Zhou, Yan-guang Liu et al.

This paper focuses on the study of the evolutionary mechanism governing the temperature field of geothermal reservoir under low-temperature tailwater reinjection conditions, which is crucial for the sustainable geothermal energy management. With advancing exploitation of geothermal resources deepens, precise understanding of this mechanism becomes paramount for devising effective reinjection strategies, optimizing reservoir utilization, and bolstering the economic viability of geothermal energy development. The article presents a comprehensive review of temperature field evolution across diverse heterogeneous thermal reservoirs under low-temperature tailwater reinjection conditions, and analyzes key factors influencing this evolution. It evaluates existing research methods, highlighting their strengths and limitations. The study identifies gaps in the application of rock seepage and heat transfer theories on a large scale, alongside the need for enhanced accuracy in field test results, particularly regarding computational efficiency of fractured thermal reservoir models under multi-well reinjection conditions. To address these shortcomings, the study proposes conducting large-scale rock seepage and heat transfer experiments, coupled with multi-tracer techniques for field testing, aimed at optimizing fractured thermal reservoir models' computational efficiency under multi-well reinjection conditions. Additionally, it suggests integrating deep learning methods into research endeavors. These initiatives are of significance in deepening the understanding of the evolution process of the temperature field in deep thermal reservoirs and enhancing the sustainability of deep geothermal resource development.

Ping Wu, Xuejun Sun, Gang Chen et al.

Rectangular tunnels are often encountered in geotechnical engineering. To clarify the mechanical mechanism of the stresses around tunnels, this study presents new analytical approximant solutions for evaluating stresses around tunnels under arbitrary stress boundary conditions. The solutions consist of two parts: one is the solution for a half-plane before excavation, and the other is the solution for a half-plane with tunnels. The second part can be further decomposed into solutions of a half-plane without tunnels subjected to virtual tractions along the ground surface and solutions of an infinite plane with tunnels loaded by virtual tractions along tunnel boundaries. An efficient iterative procedure is proposed for determining the two sets of unknown virtual tractions, which are transformed into equivalent concentrated forces to simplify the computational process. The solutions agree very well with the results obtained by the finite element method. A parametric study is finally performed to investigate the influences of the tunnel buried depth, the tunnel shape, and surcharge loads on the stresses along the ground and around tunnels. The new proposed solutions potentially provide a potential alternative approach for preliminary designs of future rectangular tunnels.

S. Mohsen Haeri, Morteza Rajabigol, Saman Salaripour et al.

In this research, two shake table experiments were conducted to study the effects of non-liquefiable crust layer and superstructure mass on the responses of two sets of 2 × 2 pile groups to liquefaction-induced lateral spreading. In this regard, an inclined base layer overlain by a very loose liquefiable layer was constructed in both models; while only in one model, a non-liquefiable crust layer was built. A lumped mass, being representative of a superstructure, was attached to the cap of one pile group in both models. The models were fully instrumented with various sensors, including acceleration, displacement, and pore water pressure transducers. Also, the piles were instrumented with pair strain gauges to measure pure bending moments induced by cyclic and monotonic loadings associated with ground shaking and lateral spreading, respectively. The results showed that the existence of the non-liquefiable crust layer increases both the maximum and residual soil displacements at the free field and also the maximum bending moments in the piles. The results of the experiments indicated that the crust layer induces a high kinematic lateral soil pressure and force on the piles which are not present in the crustless case. The crust layer increases the pile cap displacement before liquefaction, albeit decreases it after liquefaction, due to the elastic rebound of the piles in the liquefiable layer. The crust layer postpones both liquefaction triggering and dissipation of excess pore water pressure. The existence of the superstructure mass on the pile caps decreases the acceleration amplitude of the pile caps, while increases their maximum displacement.

Xiaoguang Song, Yan Lu, Shikai Liang et al.

Totally, 391 unconfined groundwater samples(depth ≤ 100 m) were collected in order to investigate the high-fluoride groundwater formation causes, and explore the potential impacts on drinking water safety to local residents in Baxia region, Zhangjiakou.Hydrochemical analysis, graphical method, ions ratio method and saturation index calculation method were applied in this study to analyze the spatial distribution and formation mechanisms of high-F- groundwater.Meanwhile, the non-carcinogenic human health risk assessment model recommended by US EPA was also used to evaluate health risk of four groups of receptors.The results indicate that high-F- groundwater(F->1.5 mg/L) mainly distribute in the low-lying and piedmont zone of the downstream of high-F- magmatic rock, enclosed basin, runoff stagnant area along the river and other areas.The dissolution and precipitation of the minerals, crystal lattice replacement under alkaline environment, ion exchange are the major mechanisms for high-F- groundwater formation in the study area.Salt effect can affect F- enrichment in groundwater, but it is not the principal mechanism.There is no correlation between agricultural activities and F- enrichment in groundwater.Additionally, the power plants, steelworks and other factories distributed in Baxia region are the potential pollution sources of the Yongding River system.The impacts of these industrial contamination sources on high-F- groundwater formation cannot be ignored.The hazard index values of infants, children, adult males and adult females were 1.20, 0.74, 0.69 and 0.56, respectively, demonstrating the younger people are more susceptible to fluoride contamination.Moreover, the adult females are more resistant to fluoride contamination than the adult males in the study area.Thus, it is suggested to develop the multi-source combined water supply mode for high risk areas and improve the efficiency of defluorination, in order to ensure water supply safety.

Bouchra Nasslahsen, Bouchra Nasslahsen, Bouchra Nasslahsen et al.

Arbuscular mycorrhizal fungi are major components of soil microbiota and mainly interact with other microorganisms in the rhizosphere. Mycorrhiza establishment impacts the plant physiology and some nutritional and physical properties of the rhizospheric soil. These effects alter the development of the root or mycorrhizas resulting from the activity of soil microorganisms. The rhizosphere of mycorrhizal plants (mycorrhizosphere), is inhabited by large microbial activities responsible for several key ecosystem processes. This review is focused on the microbial interactions between mycorrhizal fungi and components of rhizosphere microbiota and highlight the agronomic potentialities of the Mycorrhiza Helper Bacteria on mycorrhiza formation. The main conclusion is that this MHB effect in the rhizosphere of mycorrhizal plants, enhance plant fitness and soil quality and are of great interest to ensure sustainable agricultural development and ecosystem functioning.

TIAN Ning 1, 2, CHEN Jian 1, 2, 3, YOU Wei-jun 4, HUANG Jue-hao 1, 2, 3, ZHANG Jiang-xiong 4, YI Shun 1, 2, FU Xiao-dong 1, 2, TIAN Kai-wei 1, 2

Due to the geological tectonic movements such as stratum uplift, fractures and folds, natural soils often exhibit rotated anisotropy. In addition, a large number of field trials show that soil parameters will show obvious non-stationarity with the increase of buried depth. It is necessary to study the non-stationary random field simulation method for rotated anisotropy of soil parameters. On the basis of the non-stationary random field simulation method proposed by Griffiths, through the coordinate transformation of the autocorrelation function of the soil parameters, the non-stationary random field and the rotated anisotropy correlation structure are merged, and the rotated anisotropy non-stationary random field simulation method for soil parameters is proposed. A saturated clay slope is taken as an example to study the influences of the spatial variability of undrained shear strength on the slope stability. The results show that the random field which ignores the non-stationary characteristics of soil parameters will underestimate the reliability of the slope. The rotated anisotropy correlation structure has a significant impact on the reliability of the slope, and this effect gradually weakens with the increase of the parameter variability.

Yongqing Zeng, Haibo Li, X. Xia et al.

Huaizhong Liu, Jeen-Shang Lin, Jiangda He et al.

V-shaped breakouts, which may appear in underground opening during excavation, are the results of two different failure mechanisms: tensile spalling and shear fracturing. This study uses discrete elements in exploring the conditions that would lead to different breakout mechanisms under plane strain conditions. The test tunnel of the Mine-by Experiment in Lac du Bonnet granite batholith is adopted as the base problem. In order to carry out the study, some fundamental issues need to be addressed. First, an exponential softening bond that enables the incorporation of fracture energy is adopted. In order to obtain a reasonable ratio between the uniaxial compressive strength, σc, and the uniaxial tensile strength, σt, discrete disc particles are tied together to form an irregular shape clump as the basic discrete element. This effort is supported by a successful reproducing of test results from Lac du Bonnet granite in DEM modeling. The issue of sensitivity of discrete particle size on results is examined. The reduction of strength with increase in specimen size is also modeled. After the calibration work is completed, the Mine-by tunnel behavior is studied. Finally, this study shows that a reduction in σc/σt ratio, under the same setup, would cause the failure mechanism to transit from tensile spalling to shear fracturing in V-shaped breakouts.

D. E. Tonkacheev, D. A. Chareev, V. D. Abramova et al.

Research subject. Sphalerite (ZnS) is a widespread mineral that can be found in various depositional environments. During formation, this mineral can accumulate minor and trace impurities, with gold being one of the most valuable component. The issue of the chemical state of Au in sphalerite has been much discussed recently.Methods. Samples of In-, Fe- and In-Febearing sphalerite with a composition ranging from 0 to 2.5 mol.% In2S3 and 0 – 40 mol.% FeS were synthesized in an Ausaturated system using gas transport and salt flux techniques. The resulting products were subsequently investigated using EPMA and LA-ICP-MS. Results. All the elements under investigation are found to be homogeneously distributed within the sphalerite matrix. After quenching, sphalerite is shown to retain Au. Our data indicates that the observed increase in Au concentration is caused by the presence of In (up to 1.02 wt % Au) and, to a lesser extent, by that of Fe (up to ≈600 ppm Au). These elements substitute Zn in the crystal structure of sphalerite following the scheme Au+ + In3+(Fe3+) ↔ 2Zn2+, which is in good agreement with previous data obtained using the XAS method.Conclusions.A higher sulphur fugacity in the system leads to a more significant accumulation of Au in sphalerite. The concentration of Au in pure sphalerite does not exceed 10 ppm under our experimental conditions and does not depend on the activity of sulphur in the system.

محبوبه لجمیراورک نجاتی, نفیسه رنگ زن, حبیب اله نادیان et al.

سابقه و هدف: فلزات سنگین جزء آلاینده‌هایی هستند که با توجه به پایداری و دوام آن در محیط زیست، امروزه به یک معضل جهانی تبدیل شده اند. ورود این عناصر به زنجیره غذایی از روش های مختلف، تهدیدی جدی برای انسان و سایر موجودات می باشد. در اراضی کشاورزی واقع در اطراف مناطق صنعتی این تهدید جدی تر به نظر می رسد. لذا این پژوهش، با هدف ارزیابی خطر فلزات سنگین در خاک های اطراف شرکت صنایع فولاد خوزستان صورت گرفت. مواد و روش‌ها: به منظور بررسی اثر کودهای آلی بر غلظت عناصر سنگین در گیاه اسفناج و گشنیز در خاک‌های آلوده طبیعی اطراف کارخانه صنایع فولاد خوزستان و محاسبه نسبت خطر (HQ) جهت ارزیابی سلامت غذایی این محصولات، آزمایشی فاکتوریل در قالب طرح پایه کاملاً تصادفی با سه تیمار فاصله از کارخانه صنایع فولاد (در سه سطح 100، 1000 و 10000 متر)، کود پیت (در دو سطح 0 و 3 درصد وزنی) و کود ورمی کمپوست (در دو سطح 0 و 3 درصد وزنی) با کشت دو گیاه آزمایشی اسفناج و گشنیز در سه تکرار انجام شد. مقدار عناصر روی، مس، نیکل، کادمیوم و سرب در نمونه های خاک به روش هضم با اسید (جهت برآورد مقدار کل)، عصاره گیری با DTPA و EDTA (جهت برآورد مقدار قابل دسترس) و در گیاه به روش خاکستر گیری تر انجام و با استفاده از دستگاه جذب اتمی اندازه گیری شد. نتایج مربوط به خاک و گیاه به ترتیب برای محاسبه شاخص آلودگی خاک و نسبت خطر مورد استفاده و ارزیابی قرار گرفتند. یافته‌ها: نتایج نشان داد با افزایش فاصله از 100 متر به 10000 متر، مجموع مقدار کل فلزات سنگین در خاک حدود 75 درصد کاهش می یابد که مؤید نقش مستقیم کارخانه صنایع فولاد در آلودگی زمین‌های اطراف است. نتایج نشان داد کود های آلی با تاثیر بر تثبیت فلزات، خطر رها سازی آن‌ها به محیط زیست را کاهش می‌دهند. با مقایسه اثرات دو کود نتایج حاکی از آن است که اثر کود پیت نسبت به کود ورمی‌کمپوست در جذب سطحی عناصر و در نتیجه کاهش انتقال فلزات سنگین به گیاه بیشتر بوده و اما ورمی‌کمپوست در افزایش وزن تر و خشک گیاه موثر‌تر عمل کرده است. نسبت خطر محاسبه شده برای عناصر سرب و کادمیوم بیشتر از حد مجاز بود، اما در مورد سایر عناصر در شرایط فعلی خطری وجود ندارد که علت آن را می توان اثر ویژگی های خاک بر عدم انحلال پذیری ترکیبات حاوی فلزات سنگین دانست. نتیجه‌گیری: با توجه به ارزش غذایی سبزیجات و اهمیت سلامت محصولات ارائه شده، استفاده از کودهای آلی جهت غنی سازی خاک ها علاوه بر افزایش کمیت، می تواند بر سلامت محصولات به ویژه در مناطق با تهدید آلودگی های زیست محیطی کمک نماید.

Alan Bloodworth, Jiang Su

Spray-applied membranes for waterproofing of sprayed concrete tunnels have led to the possibility of shear transfer between primary and secondary linings through the membrane interface, with the potential for reducing overall lining thickness. Laboratory tests have shown a reasonable degree of composite action in beam specimens. In this study, a numerical model previously calibrated against such tests is applied to a whole tunnel, considering soil–structure interaction and staged lining construction. The model shows composite action, and load sharing between the lining layers is expected in the tunnel as in the beams. Parametric studies over the practical range of interface stiffness values show that composite action is maintained, although at high interface stiffness, excessive bending may be imposed on the secondary lining, requiring additional reinforcement. An efficient composite shell design with minimal additional reinforcement is achievable if the secondary lining thickness is reduced as compared to current practice. Robustness of the system, measured in terms of the interface’s ability to transfer stress under unequal loading causing distortion on the tunnel, is found to be generally adequate. However, adjacent construction in close proximity may provide insufficient margin on membrane tensile de-bonding, particularly if the membrane is partially or fully saturated. Keywords: Composite sprayed concrete lining, Spray-applied waterproofing membrane, Interface parameters, Lining efficiency

Qin Hu, Huan Zhu, Hang Ren

Through the single row drilling experiment, this paper studied the regularity of the tooth shape parameter's influence to the disc teeth's rock-breaking effect, which provided some basis for the composite teeth type roller bit's combined experimental study and the structure design of the tooth type. This experimental research is only for the circular arc disc teeth which is arranged on the composite teeth type roller bit's main tooth. The experiments were designed using the method of orthogonal design and the results were analyzed by the fuzzy optimization method. The results show that the disc tooth's drilling effect is the best when the tip diameter is 2 mm, taper angle is 30° and the groove number is 8, and the disc tooth's drilling effect is the second best when the tip diameter is 3 mm, taper angle is 30° and the groove number is 7. The above two combined ways of drilling effect's difference is very small (the difference of the degree of the membership is 0.003).

Editorial Article

Guo Zhiguo, Wu Bing

In order to master thoroughly the different fire-extinguishing effects of N₂ and CO₂ on coal flame combustion, the self-developed experiment device of coal flame combustion was used to conduct the fire-extinguishing experiment on coal flame combustion under the condition of importing same flux N₂ and CO₂ gas fire-extinguishing agent for coal samples in Eight mine of Ping Dingshan coal mine, and the change laws of temperature of temperature field, index gas formation (O₂, CO and CH₄), heat release rate and flame image area obtained from the experimental stages of the coal flame combustion and smoldering extinguished were measured.The results show that:compared to the free combustion of coal, in coal flame combustion stage, flame out time, coal temperature rise rate, oxygen consumption, heat release rate as well as the speed of CO and CH₄ concentration decline in coal combustion with CO₂ much lower than that of coal combustion with N₂; meanwhile, the flame image area exponentially decline in coal combustion with CO₂, but the flame image area linearly decreases in coal combustion with N₂.In the coal smoldering extinguishes stage, the coal temperature, the speed of CO and CH₄ concentration decline in the coal combustion with CO₂ much higher than that of coal combustion with N₂, but the oxygen consumption and heat release rate are lower.It follows that CO₂ has greater capacity of extinguishing coal combustion compared to N₂.