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Effects of water saturation time on energy dissipation and burst propensity of coal specimens 含水饱和时间对煤样能量耗散和爆裂倾向的影响
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.3.205
Xiaohan Yang, T. Ren, Lihai Tan, A. Remennikov
Water infusion has long been taken as an effective way to eliminate coal burst risk as coal properties can be loosen and soften by water infusion. However, not all industrial trials of water infusion for coal burst prevention have been necessarily effective in all situations as the effectiveness of this method can be affected by water infusion time, coal properties and the parameters of water injection. Hence, some fundamental issues including the effects of water infusion time on burst propensity and energy evolution need to be further discussed. In this paper, four groups of coal specimens with 0 day, 5 days, 10 days, and 15 days water saturation time are tested under uniaxial compression load with the application of AE monitoring. To comprehensively compare the burst behavior of coal specimens under different water saturation time, stress-strain curves, AE counts, fragmentation characteristics and burst propensity of these groups are analyzed. It was found by this research that sufficient water saturation can mitigate the burst behavior of coal samples while insufficient water infusion might cannot reach the burst mitigation aims.
注水可以使煤的物性松动软化,长期以来被认为是消除冲击地压风险的有效途径。然而,并不是所有的工业试验都在所有情况下都有效,因为该方法的有效性受注水时间、煤的性质和注水参数的影响。因此,注水时间对破裂倾向和能量演化的影响等基本问题需要进一步探讨。本文采用声发射监测的方法,对饱和水时间分别为0天、5天、10天、15天的四组煤样进行了单轴压缩加载试验。为了综合比较不同含水饱和时间煤样的冲击行为,分析了不同含水饱和时间煤样的应力-应变曲线、声发射计数、破碎特征和冲击倾向。研究发现,足够的含水饱和度可以缓解煤样的冲击行为,而注水不足可能无法达到缓解冲击的目的。
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引用次数: 1
Design charts for consolidation settlement of marine clays using finite strain consolidation theory 用有限应变固结理论设计海相粘土固结沉降图
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.3.295
Sanghyun Jun, Jong-Ho Lee, Byung-Soo Park, H. Kwon
In this study, design charts for estimating consolidation settlement are proposed according to finite strain consolidation theory using a nonlinear constitutive relationship equation. Results of parametric sensitivity analysis shows that the final settlement, initial height, and initial void ratio exerted the greatest effect, and the coefficients of the void ratio–effective-stress. Proposed design charts were analyzed for three regions using a representative constitutive relationship equation that enables major dredged-reclaimed construction sites in Korea. The regional design charts can be calculated accurately for the final settlement because it is applied directly to the numerical analysis results, except for reading errors. A general design chart applicable to all marine clays is proposed through correlation analysis of the main parameters. A final self-weight consolidation settlement with various initial void ratios and initial height conditions should be estimated easily using the general design chart and constitutive relationship. The estimated final settlement using the general design chart is similar to the results of numerical analysis obtained using finite strain consolidation theory. Under an overburden pressure condition, design charts for estimating consolidation settlement are proposed for three regions in Korea.
本文根据有限应变固结理论,利用非线性本构关系方程,提出了固结沉降估计的设计图表。参数敏感性分析结果表明,最终沉降、初始高度和初始空隙比对土体的影响最大,空隙比-有效应力系数对土体的影响最大。使用具有代表性的本构关系方程分析了三个地区的拟议设计图,该方程使韩国主要的疏浚填海建筑工地成为可能。区域设计图直接应用于数值分析结果,除读取误差外,可准确计算出最终沉降。通过对主要参数的相关性分析,提出了适用于所有海相粘土的通用设计简图。利用一般设计图和本构关系,可以很容易地估计出不同初始空隙比和初始高度条件下的最终自重固结沉降。采用一般设计原理计算的最终沉降与采用有限应变固结理论计算的结果基本一致。在覆盖层压力条件下,提出了韩国三个地区固结沉降估算的设计图。
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引用次数: 0
Probabilistic tunnel face stability analysis: A comparison between LEM and LAM 隧道工作面稳定性概率分析:LEM与LAM的比较
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.4.399
Q. Pan, Zhiyu Chen, Yimin Wu, D. Dias, P. Oreste
It is a key issue in the tunnel design to evaluate the stability of the excavation face. Two efficient analytical models in the context of the limit equilibrium method (LEM) and the limit analysis method (LAM) are used to carry out the deterministic calculations of the safety factor. The safety factor obtained by these two models agrees well with that provided by the numerical modelling by FLAC 3D, but consuming less time. A simple probabilistic approach based on the Mote-Carlo Simulation technique which can quickly calculate the probability distribution of the safety factor was used to perform the probabilistic analysis on the tunnel face stability. Both the cumulative probabilistic distribution and the probability density function in terms of the safety factor were obtained. The obtained results show the effectiveness of this probabilistic approach in the tunnel design.
开挖面的稳定性评价是隧道设计中的一个关键问题。采用极限平衡法(LEM)和极限分析法(LAM)两种有效的解析模型对安全系数进行确定性计算。两种模型得到的安全系数与FLAC 3D数值模拟结果吻合较好,但耗时较短。采用基于蒙特卡罗模拟技术的简单概率方法,快速计算安全系数的概率分布,对巷道工作面稳定性进行了概率分析。得到了用安全系数表示的累积概率分布和概率密度函数。计算结果表明了该概率方法在隧道设计中的有效性。
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引用次数: 0
Centrifuge modelling of rock-socketed drilled shafts under uplift load 抬升荷载作用下嵌岩钻杆的离心模拟
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.5.431
Sunjin Park, Jae‐Hyun Kim, S. Kim, J. H. Park, K. Kwak, Dong‐Soo Kim
Rock-socketed drilled shafts are widely used to transfer the heavy loads from the superstructure especially in mountainous area. Extensive research has been done on the behavior of rock-socketed drilled shafts under compressive load. However, little attention has been paid to uplift behavior of drilled shaft in rock, which govern the overall behavior of the foundation system. In this paper, a series of centrifuge tests have been performed to investigate the uplift response of rock-socketed drilled shafts. The pull-out tests of drilled shafts installed in layered rocks having various strengths were conducted. The load-displacement response, axial load distributions in the shaft and the unit skin friction distribution under pull-out loads were investigated. The effects of the strength of rock socket on the initial stiffness, ultimate capacity and mobilization of friction of the foundation, were also examined. The results indicated that characteristics of rock-socket has a significant influence on the uplift behavior of drilled shaft. Most of the applied uplift load were carried by socketed rock when the drilled shaft was installed in the sand over rock layer, whereas substantial load was carried by both upper and lower rock layers when the drilled shaft was completely socketed into layered rock. The pattern of mobilized shaft friction and point where the maximum unit shaft friction occurred were also found to be affected by the socket condition surrounding the drilled shaft.
嵌岩井被广泛应用于上部结构的重荷载传递,特别是在山区。对嵌岩钻杆在压缩载荷作用下的受力特性进行了大量的研究。然而,岩石中钻孔竖井的隆升行为却很少受到重视,而隆升行为决定着基础体系的整体行为。本文通过一系列离心试验研究了嵌岩钻井的隆升响应。在不同强度的层状岩层中进行了钻孔井的拔井试验。研究了拉拔荷载作用下的载荷-位移响应、轴向载荷分布和单元表面摩擦分布。研究了岩套强度对基础初始刚度、极限承载力和摩擦动员的影响。结果表明,岩穴特征对钻孔竖井的隆升行为有显著影响。当钻杆完全嵌套于层状岩石中时,上、下两层岩石均承担了较大的载荷,而当钻杆完全嵌套于层状岩石中时,上、下两层岩石均承担了较大的载荷。运动轴的摩擦模式和最大单位轴摩擦发生的点也受到钻井轴周围套筒条件的影响。
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引用次数: 0
Numerical investigation of geocell reinforced slopes behaviorby considering geocell geometry effect 考虑土工格室几何效应的土工格室加筋边坡性能数值研究
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.6.589
A. Ardakani, A. Namaei
The present study evaluates geocell reinforced slope behavior. A three dimensional analysis is carried out to simulate soil and geocell elastoplastic behavior using the finite difference software FLAC3D. In order to investigate the geocell reinforcement effect, the geocell aperture size, thickness, geocell placement condition and soil compaction had been considered as variable parameters. Moreover, a comparison is evaluated between geocell reinforcing system and conventional planar reinforcement. The obtained results showed that the pocket size, thickness and soil compaction have considerable influence on the geocell reinforcement slope performance. Moreover, it was found that the critical sliding surface was bounded by the first geocell reinforcement and the slope stability increases, by increasing the vertical space between geocell layers. In addition, the comparison between geocell and geogrid reinforcement indicates the efficiency of using cellular honeycomb geosynthetic reinforcement.
本研究评估土工格室加筋边坡的性能。采用有限差分软件FLAC3D对土体和土工格室的弹塑性特性进行了三维模拟。为了研究土工格室的加固效果,将土工格室孔径大小、厚度、土工格室布置条件和土壤压实度作为可变参数。并对土工格室配筋体系与传统平面配筋体系进行了比较。结果表明,土袋尺寸、厚度和土压实度对土工格室加固边坡的性能有较大影响。此外,发现临界滑动面以第一格室加固为界,并通过增加格室层之间的垂直间距来增加边坡的稳定性。此外,土工格室加固与土工格栅加固的对比表明了采用蜂窝蜂窝土工合成加固的有效性。
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引用次数: 6
Vertical load on a conduit buried under a sloping ground 埋在倾斜地面下的管道的垂直荷载
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.6.599
Muhammad Umer Arif Khan, S. Shukla
Conduits are commonly installed below the ground for utility conveyance around the world. Vertical load on a buried conduit is an important parameter that needs to be known to ensure its safe design and installation. Consideration of soil arching in load calculations helps achieve a more realistic and efficient design. In the past, considering the arching effect, the design charts have been presented for use by practicing engineers to calculate the vertical load on the conduit buried below the level ground. There are currently no design charts for calculating the vertical load on the conduit buried under a sloping ground. In this paper, an attempt has been made to present the derivation of a generalized analytical expression considering that the soil mass overlying the conduit has a sloping face and the arching phenomenon takes place. The developed generalized expression has been used to present some design charts considering specific values of slope geometry, soil properties and burial depths. Furthermore, analytical results for specific soil parameters have been compared with the results extracted from a commercial software PLAXIS 2D, for a developed numerical model and an independent study.
在世界范围内,管道通常安装在地下进行公用事业输送。埋地管道的竖向荷载是保证其安全设计和安装的重要参数。在荷载计算中考虑土拱有助于实现更真实、更有效的设计。在以往的设计中,考虑到拱效应,设计图纸主要是供工程实践人员计算埋于水平地面以下的管道竖向荷载时使用。目前还没有计算斜坡地下埋管竖向荷载的设计图纸。本文尝试推导出考虑管道上覆土体坡面和拱拱现象的广义解析表达式。利用所开发的广义表达式给出了考虑边坡几何形状、土壤性质和埋深等特定值的设计图表。此外,针对开发的数值模型和独立研究,将特定土壤参数的分析结果与从商业软件PLAXIS 2D中提取的结果进行了比较。
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引用次数: 5
Cluster and information entropy analysis of acoustic emission during rock failure process 岩石破坏过程声发射的聚类与信息熵分析
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.2.135
Zhenghu Zhang, L. Hu, Tiexin Liu, Hongchun Zheng, Chun’an Tang
This study provided a new research perspective for processing and analyzing AE data to evaluate rock failure. Cluster method and information entropy theory were introduced to investigate temporal and spatial correlation of acoustic emission (AE) events during the rock failure process. Laboratory experiments of granite subjected to compression were carried out, accompanied by real-time acoustic emission monitoring. The cumulative length and dip angle curves of single links were fitted by different distribution models and distribution functions of link length and directionality were determined. Spatial scale and directionality of AE event distribution, which are characterized by two parameters, i.e., spatial correlation length and spatial correlation directionality, were studied with the normalized applied stress. The entropies of link length and link directionality were also discussed. The results show that the distribution of accumulative link length and directionality obeys Weibull distribution. Spatial correlation length shows an upward trend preceding rock failure, while there are no remarkable upward or downward trends in spatial correlation directionality. There are obvious downward trends in entropies of link length and directionality. This research could enrich mathematical methods for processing AE data and facilitate the early-warning of rock failure-related geological disasters.
该研究为处理和分析声发射数据评价岩石破坏提供了新的研究视角。采用聚类方法和信息熵理论研究了岩石破坏过程中声发射事件的时空相关性。对花岗岩进行了室内压缩实验,并进行了实时声发射监测。采用不同的分布模型拟合了单连杆的累计长度和倾角曲线,确定了连杆长度和方向性的分布函数。在归一化外加应力条件下,研究了以空间相关长度和空间相关方向性两个参数表征的声发射事件分布的空间尺度和方向性。讨论了链路长度和链路方向性的熵。结果表明,累计链路长度和方向性的分布服从威布尔分布。空间相关长度在岩石破坏前呈上升趋势,而空间相关方向性没有明显的上升或下降趋势。链路长度和方向性熵有明显的下降趋势。该研究可以丰富声发射数据处理的数学方法,为岩石破坏相关地质灾害的预警提供依据。
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引用次数: 0
Study on bearing characteristic of rock mass with different structures: Physical modeling 不同结构岩体承载特性研究:物理模拟
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.3.179
Z. Zhao, H. Jing, Xinshuai Shi, Lijun Yang, Q. Yin, Yuan Gao
In this paper, to study the stability of surrounding rock during roadway excavation in different rock mass structures, the physical model test for roadway excavation process in three types of intact rock mass, layered rock mass and massive rock mass were carried out by using the self-developed two-dimensional simulation testing system of complex underground engineering. Firstly, based on the engineering background of a deep mine in eastern China, the similar materials of the most appropriate ratio in line with the similarity theory were tested, compared and determined. Then, the physical models of four different schemes with 1000 mm (height) x1000 mm (length)x 250 mm (width) were constructed. Finally, the roadway excavation was carried out after applying boundary conditions to the physical model by the simulation testing system. The results indicate that the supporting effect of rockbolts has a great influence on the shallow surrounding rock, and the rock mass structure can affect the overall stability of the surrounding rock. Furthermore, the failure mechanism and bearing capacity of surrounding rock were further discussed from the comparison of stress evolution characteristics, distribution of stress arch, and failure modes in different schemes.
为了研究不同岩体结构巷道开挖过程中围岩的稳定性,利用自行开发的复杂地下工程二维模拟试验系统,对完整岩体、层状岩体和块状岩体三种类型巷道开挖过程进行了物理模型试验。首先,结合华东某深部矿山的工程背景,根据相似理论对最合适配比的相似材料进行了试验、比较和确定;然后,构建了高度为1000 mm ×长度为1000 mm ×宽度为250 mm的四种不同方案的物理模型。最后,通过仿真测试系统对物理模型施加边界条件后,进行巷道开挖。结果表明,锚杆支护效果对浅埋围岩影响较大,岩体结构会影响围岩的整体稳定性。在此基础上,从不同方案的应力演化特征、应力拱分布及破坏模式对比等方面,进一步探讨了围岩的破坏机制和承载能力。
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引用次数: 1
Ageing effect on compressibility, permeability and shear strength of clayey soils exposed to salt solutions 老化对盐溶液下粘性土压缩性、渗透性和抗剪强度的影响
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.3.245
Emel Çakar, Y. Yukselen-Aksoy
The present study investigated the ageing effect on compressibility, permeability and shear strength behavior of kaolin and bentonite samples in the presence of NaCl and CaCl2 solutions. The compressibility, permeability and shear strength parameters were determined on the 60, 190, and 250 days cured samples. The results have shown that, the kaolin sample becomes more compressible in the presence Ca2+ ions with ageing. Generally, the normalized compression index values of bentonite samples increased at the end of 60 days and 250 days curing time periods. The normalized permeability value of kaolin decreased by ageing in the presence of Na+ ions almost twofold. The permeability values of bentonite increased both in NaCl and CaCl2 solutions during ageing. In the presence of Na+ ions kaolin had higher max. shear stress value than Ca2+ ions. When the max. shear stress values of 0, 60 and 190 days samples were compared, it was seen that NaCl solution had no significant effect on the shear strength of kaolin sample. However, the shear strength of kaolin increased in the CaCl2 solution during ageing. In the presence of Ca2+ ions the max. shear stress value of bentonite was higher. The results of this study have shown that ageing has significant effects on the compressibility, permeability and shear strength of kaolinitic and bentonitic clayey soils.
研究了NaCl和CaCl2溶液存在下高岭土和膨润土试样的老化对其压缩性、渗透性和抗剪强度的影响。测定了固化60、190和250天试样的压缩性、渗透性和抗剪强度参数。结果表明,随着年龄的增长,高岭土样品在Ca2+离子存在下变得更具压缩性。膨润土样品的归一化压缩指数值一般在养护60天和250天结束时有所增加。在Na+离子存在下,高岭土的标准化渗透率值随着老化而降低了近2倍。老化过程中,膨润土在NaCl和CaCl2溶液中的渗透率均有所增加。在Na+离子存在下,高岭土具有较高的max。剪应力值大于Ca2+离子。当最大值。对比了0、60和190 d试样的剪切应力值,发现NaCl溶液对高岭土试样的抗剪强度无显著影响。而高岭土在CaCl2溶液中的抗剪强度随着老化而增加。在Ca2+离子存在的情况下。膨润土剪切应力值较高。研究结果表明,老化对高岭石和膨润土的压缩性、渗透性和抗剪强度有显著影响。
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引用次数: 1
Shear behavior of EPS geofoam reinforced with polypropylene fiber 聚丙烯纤维增强EPS土工泡沫塑料的剪切性能
IF 3.2 3区 工程技术 Q2 ENGINEERING, CIVIL Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.5.347
M. R. Arvin, Gholam Reza Ghafary, N. Hataf, A. Ghafary
The EPS geofoam as a lightweight material has been widely used in recent years to boost the performance of geotechnical structures. Both the internal and external stability of the fills made by the EPS blocks should be met. Overlying concrete slabs and thick pavements or applying denser EPS blocks provide internal stability of EPS geofoam lightweight fills by reducing the internal vertical stress within the EPS blocks. As an alternative way, in this study, new composite material is introduced by using the polypropylene fiber to reinforce the EPS geofoam in the factory as an attempt to improve the mechanical properties of the EPS geofoam. The composite material was fabricated in different fiber contents by solidifying the mixture of fiber and geofoam beads using controlled heat and temperature. Then, the behavior of the composite was studied using a series of direct shear tests. The results show that including fiber leads to a rise in the shear strength and a significant decline in the compressibility of the reinforced EPS geofoam. For the geofoam reinforced with 80% fiber content, up to 23.3% increase in the shear strength and 57.6% reduction in the vertical displacement (Δz) were observed in the laboratory. In addition, while the change in the composite's cohesion is largely decreased, the friction angle of the composite shows an increasing trend with fiber content increase. A maximum of 12.6% reduction in the cohesion and 100% increase in the internal friction angle of the reinforced material were observed in the laboratory.
EPS土工泡沫作为一种轻质材料,近年来被广泛应用于提高土工结构的性能。EPS砌块填充物应同时满足内部稳定性和外部稳定性。铺上混凝土板和厚路面或使用较密的EPS砌块,可减少EPS砌块内部的垂直应力,从而提供EPS土工泡沫轻质填充物的内部稳定性。作为一种替代方法,本研究引入了一种新的复合材料,在工厂中使用聚丙烯纤维对EPS土工泡沫进行增强,试图改善EPS土工泡沫的力学性能。通过控制热量和温度,将纤维与土工泡沫珠的混合物固化,制成不同纤维含量的复合材料。然后,通过一系列的直剪试验研究了复合材料的性能。结果表明:纤维的加入使增强EPS土工泡沫的抗剪强度提高,压缩性能明显下降;在实验室试验中,纤维含量为80%的土工泡沫的抗剪强度提高了23.3%,竖向位移降低了57.6% (Δz)。此外,随着纤维含量的增加,复合材料的黏聚力变化幅度大大减小,但摩擦角呈增大趋势。在实验室中观察到增强材料的黏聚力最大降低12.6%,内摩擦角最大增加100%。
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引用次数: 3
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Geomechanics and Engineering
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