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Surface erosion behavior of biopolymer-treated river sand 生物聚合物处理河砂的表面侵蚀行为
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.1.049
Yeong-Man Kwon, G. Cho, Moonkyung Chung, I. Chang
The resistance of soil to the tractive force of flowing water is one of the essential parameters for the stability of the soil when directly exposed to the movement of water such as in rivers and ocean beds. Biopolymers, which are new to sustainable geotechnical engineering practices, are known to enhance the mechanical properties of soil. This study addresses the surface erosion resistance of river-sand treated with several biopolymers that originated from micro-organisms, plants, and dairy products. We used a state-of-the-art erosion function apparatus with P-wave reflection monitoring. Experimental results have shown that biopolymers significantly improve the erosion resistance of soil surfaces. Specifically, the critical shear stress (i.e., the minimum shear stress needed to detach individual soil grains) of biopolymer-treated soils increased by 2 to 500 times. The erodibility coefficient (i.e., the rate of increase in erodibility as the shear stress increases) decreased following biopolymer treatment from 1 x 10-2 to 1 x 10-6 times compared to that of untreated river-sands. The scour prediction calculated using the SRICOS-EFA program has shown that a height of 14 m of an untreated surface is eroded during the ten years flow of the Nakdong River, while biopolymer treatment reduced this height to less than 2.5 m. The result of this study has demonstrated the possibility of cross-linked biopolymers for river-bed stabilization agents.
土壤对水流牵引力的阻力是直接暴露在河流和海底等水的作用下土壤稳定性的重要参数之一。生物聚合物是可持续岩土工程实践的新事物,已知可以增强土壤的力学特性。本研究探讨了几种来自微生物、植物和乳制品的生物聚合物处理河沙的表面抗侵蚀性。我们使用了最先进的侵蚀函数仪器和p波反射监测。实验结果表明,生物聚合物显著提高了土壤表面的抗侵蚀能力。具体而言,生物聚合物处理土壤的临界剪应力(即分离单个土壤颗粒所需的最小剪应力)增加了2至500倍。与未经处理的河砂相比,生物聚合物处理后的可蚀性系数(即随着剪切应力的增加而增加的可蚀性速率)从1 × 10-2降低到1 × 10-6倍。利用SRICOS-EFA程序计算的冲刷预测结果表明,在洛东江10年的流量中,未经处理的地表被侵蚀的高度为14 m,而生物聚合物处理将这一高度降低到2.5 m以下。本研究结果证明了交联生物聚合物作为河床稳定剂的可能性。
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引用次数: 6
Evaluation of geological conditions and clogging of tunneling using machine learning 利用机器学习评估地质条件和隧道堵塞
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.1.059
Xue-Dong Bai, W. Cheng, D. Ong, Ge Li
There frequently exists inadequacy regarding the number of boreholes installed along tunnel alignment. While geophysical imaging techniques are available for pre-tunnelling geological characterization, they aim to detect specific object (e.g., water body and karst cave). There remains great motivation for the industry to develop a real-time identification technology relating complex geological conditions with the existing tunnelling parameters. This study explores the potential for the use of machine learning-based data driven approaches to identify the change in geology during tunnel excavation. Further, the feasibility for machine learning-based anomaly detection approaches to detect the development of clayey clogging is also assessed. The results of an application of the machine learning-based approaches to Xi'an Metro line 4 are presented in this paper where two tunnels buried in the water-rich sandy soils at depths of 12-14 m are excavated using a 6.288 m diameter EPB shield machine. A reasonable agreement with the measurements verifies their applicability towards widening the application horizon of machine learning-based approaches.
沿隧道路线安装的钻孔数量往往不足。虽然地球物理成像技术可用于隧道前地质表征,但其目的是检测特定物体(如水体和溶洞)。该行业仍然有很大的动力开发一种将复杂地质条件与现有隧道参数相关联的实时识别技术。本研究探索了使用基于机器学习的数据驱动方法来识别隧道开挖期间地质变化的潜力。此外,还评估了基于机器学习的异常检测方法用于检测粘土堵塞发展的可行性。本文介绍了基于机器学习的方法在西安地铁4号线的应用结果,在12-14 m的富水沙土中,使用直径为6.288 m的EPB盾构机开挖了两条隧道。与测量值的合理一致验证了它们对扩大基于机器学习的方法的应用范围的适用性。
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引用次数: 23
Shear strength behaviour of coral gravelly sand subjected to monotonic and cyclic loading 珊瑚砂在单调和循环荷载作用下的抗剪强度特性
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.25.2.089
A. Vu
The paper presents an experimental study on the strength behaviour of a coral gravelly sand from Vietnam subjected to monotonic and cyclic loading. A series of direct shear tests were carried out to investigate the shear strength behaviour and the factors affecting the shear strength of the sand such as relative density, cyclic load, amplitude of the cyclic load and loading rate. The study results indicate that the shear strength parameters of the coral gravelly sand include not only internal friction angle but also apparent cohesion. These parameters vary with the relative density, cyclic load, the amplitude of the cyclic load and loading rate. The shear strength increases with the increase of the relative density. The shear strength increases after subjecting to cyclic loading. The amplitude of the cyclic load affects the shear strength of coral gravelly sand, the shear strength increases as the amplitude of the cyclic load increases. The loading rate has insignificantly effect on the shear strength of the coral gravelly sand.
本文对越南珊瑚砂土在单调和循环荷载作用下的强度特性进行了试验研究。进行了一系列的直剪试验,研究了相对密度、循环荷载、循环荷载幅值和加载速率等因素对砂体抗剪强度的影响。研究结果表明,珊瑚砾石砂的抗剪强度参数不仅包括内摩擦角,还包括表观黏聚力。这些参数随相对密度、循环荷载、循环荷载幅值和加载速率的变化而变化。抗剪强度随相对密度的增大而增大。受循环荷载作用后,抗剪强度增大。循环荷载幅值影响珊瑚砂抗剪强度,随着循环荷载幅值的增大,珊瑚砂抗剪强度增大。加载速率对珊瑚砂抗剪强度的影响不显著。
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引用次数: 0
Load-displacement behaviour of tapered piles: Theoretical modelling and analysis 锥形桩的荷载-位移特性:理论建模与分析
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.1.001
Yunong Li, Wei Li
This paper presents a simplified analytical approach for evaluating the load-displacement response of single tapered pile and pile groups under static axial compressive loads. The response of the tapered pile shaft is considered elastically in the initial stage, whereas the increase in stresses due to slippage along the pile-soil interface is obtained from a developed undrained cylindrical cavity expansion solution based on the K0-based anisotropic modified Cam-clay (K0-AMCC) model. An effective iterative computer program is developed to calculate the load-displacement behaviour of a single tapered pile. Regarding the response analysis of tapered pile groups, a finite-difference method is employed to calculate the interaction between tapered pile shaft, and the linear elastic model to simulate the interaction developed at the pile base. A reduction coefficient is introduced into the analysis of pile shaft interaction to clarify the reinforcing effect between tapered piles. Therefore, the settlement calculation methods of pile groups are proposed for different pile cap stiffness. The calculation methods of single tapered pile and pile groups are validated using two 3D Finite Element (FE) programs, and the comparison results show that reasonable predictions can be made using the method proposed in this paper. Parametric studies are conducted to investigate the effects of taper angle, soil anisotropy, pile spacing, and pile number on the load-displacement behaviour of single tapered pile and tapered pile groups.
本文提出了单桩和群桩在静轴压荷载作用下的荷载-位移响应的简化分析方法。锥形桩轴在初始阶段的响应考虑为弹性响应,而沿桩-土界面滑移引起的应力增加则采用基于k0 -基各向异性修正Cam-clay (K0-AMCC)模型的不排水柱腔扩展解来计算。开发了一种有效的迭代计算程序来计算单桩的荷载-位移特性。针对锥度桩群的响应分析,采用有限差分法计算锥度桩身之间的相互作用,采用线弹性模型模拟锥度桩身与锥度桩身之间的相互作用。在桩身相互作用分析中引入折减系数,以阐明锥形桩间的加固作用。据此,提出了不同承台刚度下群桩沉降计算方法。采用两种三维有限元程序对单桩和群桩的计算方法进行了验证,对比结果表明,采用本文提出的方法可以做出合理的预测。参数化研究探讨了锥角、土体各向异性、桩间距和桩数对单桩和群桩荷载-位移特性的影响。
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引用次数: 1
Allowable wall deflection of braced excavation adjacent to pile-supported buildings 桩承式建筑物旁支撑开挖允许墙体挠度
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.2.161
Linlong Mu, Maosong Huang, G. H. Roodi, Zhenhao Shi
To protect adjacent buildings is a major concern for the construction of excavation in urban areas. In practice, the impacts on neighboring pile-supported buildings are normally minimized by limiting the deflection of earth retaining wall. Existing deflection criteria, however, are often empirical. In this work, we employ an analytical model to relate the wall deflection of braced excavation to the response of adjacent pile-supported buildings and thus forming a theoretical tool for determining the allowable deformation of excavation support structures based on the tolerance of buildings to distortion. The model combines closed-form excavation-induced free-field soil movements with elastic continuum solution that explicitly accounts for the interactions between raft, piles, and soils. Following validation against field model test and finite element simulation, the model is utilized to reveal the correspondence between the angular distortion of pile-supported buildings and the maximum retaining wall deflection under different combinations of excavation geometry, soil properties, and parameters of pile foundation potentially encountered in practice. A dimensionless factor composed of these influencing variables is proposed, and its correlation with the ratio of the building angular distortion over the maximum retaining wall deflection provides a rational way to determine the serviceability limit states of braced excavation.
保护邻近建筑物是市区挖掘施工的一个主要问题。在实际应用中,通常通过限制挡土墙的挠度来减小对邻近桩基建筑的影响。然而,现有的挠度准则往往是经验的。在这项工作中,我们采用了一个解析模型,将支撑开挖的墙体挠度与邻近的桩基建筑的响应联系起来,从而形成了一个基于建筑物对变形的容忍度来确定开挖支护结构允许变形的理论工具。该模型结合了封闭形式的开挖引起的自由场土壤运动和弹性连续体解决方案,明确地说明了筏板,桩和土壤之间的相互作用。通过现场模型试验和有限元模拟验证,揭示了在实际可能遇到的开挖几何形状、土体性质和桩基参数的不同组合下,桩支建筑的角变形与最大挡土墙挠度之间的对应关系。提出了由这些影响变量组成的无量纲因子,并将其与建筑物角变形与挡土墙最大挠度之比的关系,为确定支撑开挖的使用极限状态提供了一种合理的方法。
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引用次数: 0
Three-Dimensional Modeling of Monopiles in Sand Subjected to Lateral Loading under Static and Cyclic Conditions 静态和循环条件下受侧向荷载作用的砂土中单桩的三维建模
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.2.175
A. Barari, X. Zeng, M. Rezania, L. Ibsen
Here, the results of a three-dimensional finite element study of the complex interaction of horizontal and moment loads (HM) on offshore monopiles as failure envelope, are reported. A new design criterion is described which is based on critical length, ultimate limit states, load characteristics and Eigen-frequency to ensure stable behavior of laterally loaded monopiles. Numerical analyses were performed to examine nonlinear interaction of a soil-pile system for 10,000 load cycles. The resulting framework can predict angular rotation due to cyclic loading. According to the loading level and duration of a load, elastic strains accumulate in the vicinity of a pile. Fairly intermediate two-way cyclic loading induced the largest rotations irrespective of the analysis performed (i.e., drained versus partially drained). Based on the regression coefficients of the non-dimensional frameworks used, accumulating rocking deformations of a pile at seabed level appear to be dependent on cyclic load ratio, drainage condition, and duration of loading. For safe design, sensitivity of the natural frequency of offshore wind turbine (OWT) at a monopile critical length as well as shorter lengths were also examined. The analytical model proposed here for determining the natural frequency of an OWT considers that soil-structure interaction (SSI) can be represented by monopile head springs characterized by lateral stiffness, KL, rotational stiffness, KR, cross-coupling stiffness, KLR, and parabolic soil stiffness variation with depth.
本文报道了海上单桩作为破坏包络的水平和弯矩载荷(HM)复杂相互作用的三维有限元研究结果。提出了一种基于临界长度、极限状态、荷载特性和本征频率的单桩稳定设计准则。对1万次荷载循环下桩土系统的非线性相互作用进行了数值分析。所得到的框架可以预测由于循环加载的角旋转。根据荷载水平和荷载持续时间的不同,弹性应变会在桩的附近累积。无论进行何种分析(即排水还是部分排水),相当中等的双向循环荷载都会引起最大的旋转。根据所采用的无量纲框架的回归系数,海底水平桩的累积摇摆变形似乎与循环荷载比、排水条件和荷载持续时间有关。为了安全设计,还研究了单桩临界长度和较短长度下海上风力机固有频率的敏感性。本文提出的用于确定OWT固有频率的解析模型认为,土-结构相互作用(SSI)可以用单桩头弹簧来表示,其特征是侧向刚度、KL、旋转刚度、KR、交叉耦合刚度、KLR和土壤刚度随深度的抛物线变化。
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引用次数: 2
A similarity solution for spherical cavity drained expansion in overconsolidated soils considering large deformation 考虑大变形的超固结土球形孔洞排水膨胀的相似解
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.5.427
Hanbo Zheng, Hao Zhang, F. Liang
This paper presents a novel similarity solution for drained spherical cavity expansion in overconsolidated soils, which creatively incorporates the large strain into similarity solution. The salient feature of the present solution lies in that it properly represents the large deformation associated responses of the overconsolidated soil during cavity expansion. The logarithmic strain components are reasonably incorporated into the similarity solution, which is a general solution technique that has been widely used to solve cavity expansion problems, to creatively account for the large deformation of soils during cavity expansion in such a solution framework. The competent modified unified-hardening (UH) model is employed to properly represent the unique behavior of overconsolidated soils during expansion, where three-dimensional strength characteristics of the soil are taken into account as well. The partial differential governing equations under Eulerian description are transformed into a set of first order ordinary differential equations under Lagrangian description and further solved as an initial value problem by MATLAB. The present method is verified by comparing with the modified Cam-clay model based solutions and an extensive parameter analysis is subsequently conducted for soils with different overconsolidation ratio. The unique expansion behaviors in the overconsolidated soils including the peak strength behavior, strain-hardening/softening and shear dilatancy behaviors are discussed in a comprehensive and in-depth manner.
本文提出了一种新的超固结土排水球孔扩展相似解,创造性地将大应变纳入相似解中。该解的显著特点在于能较好地反映超固结土在洞室膨胀过程中的大变形相关响应。将对数应变分量合理地纳入到相似解中,这是一种广泛用于解决洞室扩展问题的通解技术,创造性地解释了在这种解框架下,洞室扩展过程中土体的大变形。在考虑了超固结土三维强度特性的基础上,采用了修正统一硬化(UH)模型,较好地反映了超固结土在膨胀过程中的独特行为。将欧拉描述下的偏微分控制方程转化为一组拉格朗日描述下的一阶常微分方程,并用MATLAB作为初值问题求解。通过与基于修正Cam-clay模型的解的比较,验证了本文方法的正确性,并对不同超固结比的土体进行了广泛的参数分析。对超固结土的峰值强度特性、应变硬化/软化特性和剪切剪胀特性等独特的膨胀特性进行了全面深入的讨论。
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引用次数: 0
Analytical assessment of coupled influences of surrounding rock reinforcement and deformation release on tunnel response 围岩加固与变形释放对隧道响应耦合影响的分析评价
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.26.6.541
S. Qin, Kui Wu, Z. Shao
Attempt has been proved to be effective that surrounding rock reinforcement is emphasized simultaneously considering displacement release in weak rock tunnels. In this study, the calculation formulas for mechanical parameters of bolt-reinforced rocks are provided using the homogenization method and the supporting characteristic curve is divided into three stages with proposing the corresponding stiffness equations. The mechanical model for bolted-reinforced rock-yielding supports interaction is then established and coupled solutions for displacements and stresses around tunnels considering bolt reinforcement and yielding effects are provided. Furthermore, parametric investigations on the influences of rockbolts and yielding supports are carried out. Results show that (1) rock displacement gradually decreases as the rockbolt length increases. However, when rockbolt length becomes large enough, the further improvement of rock displacement will not be obvious by still increasing their length. (2) Both rock displacement and plastic zone of tunnel decrease with the increase of rockbolt radius. There exists the highest utilization of rockbolts corresponding to a certain rockbolt radius. (3) Also, the rock displacement and plastic zone of tunnel decrease as installation density of rockbolts including circumferential space and longitudinal space increases. Under the condition prescribed, this decreasing trend becomes sharper and the improvement is more evident. (4) Larger yielding displacement or stiffness parameter leads to smaller support pressure, but greater plastic radius of tunnel. The optimal yielding displacement and stiffness parameters need to be determined through a comprehensive investigation combining rock properties, support characteristics and tunnel design requirements.
在软弱围岩隧道中,考虑位移释放同时强调围岩加固的尝试已被证明是有效的。本文采用均质化方法,给出了锚杆加固岩石力学参数的计算公式,并将支护特性曲线划分为三个阶段,提出了相应的刚度方程。在此基础上,建立了锚杆加固围岩屈服支护相互作用的力学模型,给出了考虑锚杆加固和屈服效应的巷道周围位移和应力耦合解。此外,还对锚杆和屈服支架的影响进行了参数化研究。结果表明:(1)随着锚杆长度的增加,岩石位移逐渐减小。然而,当锚杆长度足够大时,继续增加锚杆长度对岩石位移的进一步改善并不明显。(2)随着锚杆半径的增大,围岩位移和巷道塑性区均减小。一定的锚杆半径对应的锚杆利用率最高。(3)随锚杆安装密度(包括周向空间和纵向空间)的增大,巷道围岩位移和塑性区减小。在规定的条件下,这种下降趋势更加明显,改善更加明显。(4)屈服位移或刚度参数越大,支护压力越小,巷道塑性半径越大。需要结合岩石特性、支护特性和隧道设计要求进行综合研究,确定最优屈服位移和刚度参数。
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引用次数: 4
The bearing capacity of circular footings on sand with thin layer: An experimental study 薄层砂土圆形地基承载力试验研究
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.27.2.123
M. Askari, A. Khalkhali, M. Makarchian, N. Ganjian
Thin layers have substantial effects on the ultimate bearing capacity, despite their seeming insignificant. In this research, the effects of a thin layer on the ultimate bearing capacity of a circular footing on the sand bed are investigated by small-scale physical models. The investigations were carried out by varying the material type, thickness, and depth of the thin layer. The results indicate that the weak thin layer decreases both the ultimate bearing capacity and stiffness of the soil-footing system and the strong thin layer increases both the ultimate bearing capacity and the soil-footing system stiffness. The amount of this effect depends on the thickness, depth of deposition, and the material type of the thin layer. According to the results, the weak layer for the critical depth of 1B led to the most reduction in ultimate bearing capacity by 26% (from 183 kPa to 135 kPa), while no effects were observed at the depth of 2B. The strong layer is also for the state where this layer is just below the footing, had the highest increase in ultimate bearing capacity by 329% (from 183 kPa to 603 kPa), but at a depth of about 1.25B, it was ineffective.
薄层对极限承载能力有实质性的影响,尽管它们看起来微不足道。本文采用小尺度物理模型研究了薄层对砂床圆形基础极限承载力的影响。通过改变薄层的材料类型、厚度和深度来进行调查。结果表明:弱薄层降低了基础体系的极限承载力和刚度,强薄层增加了基础体系的极限承载力和刚度;这种影响的大小取决于厚度、沉积深度和薄层的材料类型。结果表明,临界深度为1B的弱层对极限承载力的影响最大,降低幅度为26%(从183 kPa降至135 kPa),而在临界深度为2B的弱层对极限承载力没有影响。加固层也适用于加固层刚好位于基础下方的状态,加固层的极限承载力提高幅度最大,达到329%(从183 kPa提高到603 kPa),但在约1.25B深度处加固层效果不佳。
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引用次数: 0
Study on lateral behavior of digging well foundation with consideration of soil-foundation interaction 考虑地基-地基相互作用的挖井基础横向性能研究
IF 3.2 3区 工程技术 Q1 Engineering Pub Date : 2021-01-01 DOI: 10.12989/GAE.2021.24.1.015
W. Yi, Xingchong Chen, Xiyin Zhang, M. Ding, Jinhua Lu, Hua Ma
Digging well foundation has been widely used in railway bridges due to its good economy and reliability. In other instances, bridges with digging well foundation still have damage risks during earthquakes. However, there is still a lack of knowledge of lateral behavior of digging well foundation considering the soil-foundation interaction. In this study, scaled models of bridge pier-digging well foundation system are constructed for quasi-static test to investigate their lateral behaviors. The failure mechanism and responses of the soil-foundation-pier interaction system are analyzed. The testing results indicate that the digging foundations tend to rotate as a rigid body under cyclic lateral load. Moreover, the depth-width ratio of digging well foundation has a significant influence on the failure mode of the interaction system, especially on the distribution of foundation displacement and the failure of pier. The energy dissipation capacity of the interaction system is discussed by using index of the equivalent viscous damping ratio. The damping varies with the depth-width ratio changing. The equivalent stiffness of soil-digging well foundation-pier interaction system decreases with the increase of loading displacement in a nonlinear manner. The absolute values of the interaction system stiffness are significantly influenced by the depth-width ratio of the foundation.
挖井基础以其良好的经济性和可靠性在铁路桥梁中得到了广泛的应用。在其他情况下,具有良好基础的桥梁在地震中仍然存在损坏风险。然而,考虑地基-地基相互作用的挖井基础横向行为研究仍然缺乏。本文建立了桥梁桥墩-挖井基础体系的比例模型,进行了准静力试验,研究了其横向特性。分析了地基-桥墩相互作用体系的破坏机理和响应。试验结果表明,在循环横向荷载作用下,基坑基础呈刚体旋转趋势。此外,挖井基础的深宽比对相互作用体系的破坏模式有显著影响,特别是对基础位移分布和桥墩破坏有显著影响。利用等效粘性阻尼比指标讨论了相互作用系统的耗能能力。阻尼随深宽比的变化而变化。土-挖井-基础-墩相互作用体系的等效刚度随荷载位移的增加呈非线性减小。基础的深宽比对相互作用体系刚度的绝对值有显著影响。
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引用次数: 1
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Geomechanics and Engineering
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