Underground Space最新文献_第3页

Experimental and numerical investigation of the load-bearing capacity of bolt-fastened wedge active joints for prestressed internal bracing in subway excavations 用于地铁挖掘工程预应力内支撑的螺栓紧固楔形活动接头承载能力的实验和数值研究

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-27 DOI: 10.1016/j.undsp.2024.06.006

Chenhe Ge , Pengfei Li , Mingju Zhang , Meng Yang , Weizi Wan

The present study develops a novel type of active joint node-bolt fasten wedge (BFW) active joints, aiming to investigate the load-bearing capacity of a BFW joint in a quantitative way and put forward precise formulas for its yield load and compression rigidity. To achieve this, indoor axial loading tests were conducted on two BFW joints, accompanied by a set of numerical simulations with the finite element approach implemented in ABAQUS. Parametric research was then conducted to assess the impact of various factors on the yield load and initial compression rigidity of BFW joints, leading to the derivation of precise calculation formulas for accurate prediction of these parameters. The key findings indicate that enhancing the bolt strength from 10.9 to 12.9 significantly improves mechanical performance. Under axial compression, the final bearing force, yield load, and initial compression rigidity increase by 0.86, 1.06, and 0.15 times, respectively. Numerical models accurately predict joint behavior under axial force, confirming their reliability. Parameter studies reveal that increasing web and eaves thickness, bolt strength, and diameter improves bearing capacity, while splint thickness has little effect. The fitting formulas introduced can precisely estimate yield load and rigidity, providing practical value for engineering applications.

本研究开发了一种新型节点-螺栓紧固楔（BFW）主动连接，旨在定量研究 BFW 连接的承载能力，并提出其屈服载荷和压缩刚度的精确公式。为此，对两个 BFW 接头进行了室内轴向加载试验，并使用 ABAQUS 中的有限元方法进行了一系列数值模拟。然后进行了参数研究，以评估各种因素对 BFW 接头的屈服载荷和初始压缩刚度的影响，从而推导出精确预测这些参数的精确计算公式。主要研究结果表明，将螺栓强度从 10.9 提高到 12.9 可显著改善机械性能。在轴向压缩条件下，最终承载力、屈服载荷和初始压缩刚度分别增加了 0.86 倍、1.06 倍和 0.15 倍。数值模型准确地预测了轴向力作用下的连接行为，证实了其可靠性。参数研究表明，增加腹板和檐口厚度、螺栓强度和直径可提高承载能力，而夹板厚度影响不大。引入的拟合公式可以精确估算屈服载荷和刚度，为工程应用提供了实用价值。

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引用次数: 0

Numerical studies on the synergistic effects of smoke extraction and control performance by mechanical ventilation shafts during tunnel fires 隧道火灾中机械通风井排烟和控制性能协同效应的数值研究

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-27 DOI: 10.1016/j.undsp.2024.07.005

Bin Zhu , Haiyong Cong , Zhuyu Shao , Hairuo Hu , Lili Ye , Yubo Bi , Yiping Zeng

High smoke extraction efficiency and a relatively stable smoke layer stratification are both expected in tunnel ventilation systems. The purpose of this paper is to explore the overall performance of mechanical board-coupled shaft under different ventilation strategies. A total of 57 simulations were conducted, and the effects of the distance between the shaft and board (

h_{D}

) and ventilation velocity on the overall performance were investigated. The results indicate that the performance of smoke extraction and control will be improved by the application of mechanical ventilation and board. Smoke movement patterns under different working conditions were different, for cases of

h_{D} \leq 0.40 m

the smoke could propagate through the whole tunnel without backflow, while for cases of

h_{D} > 0.40 m

, the backflow exists and the smoke movement can be separated into three periods (propagation, stagnation, and retraction). The critical criterion of backflow was investigated and a simple model was deduced to estimate the maximum propagation length. Moreover, the dimensionless time for the smoke flow to reach its maximum propagation length was established. Finally, a comprehensive index

φ

was proposed to evaluate the synergistic effects of smoke extraction and control performance. These studies may provide positive significance for the ventilation design.

隧道通风系统需要较高的排烟效率和相对稳定的烟层分层。本文旨在探讨机械板耦合竖井在不同通风策略下的整体性能。共进行了 57 次模拟，研究了竖井与板之间的距离（hD）和通风速度对整体性能的影响。结果表明，机械通风和板的应用将提高排烟和控烟性能。不同工况下的烟雾运动模式也不同，当 hD≤0.40m 时，烟雾可在整个隧道内传播，不会出现回流现象；而当 hD>0.40m 时，则会出现回流现象，烟雾运动可分为三个时期（传播期、停滞期和回缩期）。研究了回流的临界标准，并推导出一个简单的模型来估算最大传播长度。此外，还确定了烟流达到最大传播长度的无量纲时间。最后，提出了一个综合指标 φ 来评估排烟和控制性能的协同效应。这些研究可为通风设计提供积极意义。

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引用次数: 0

Coal-rock interface real-time recognition based on the improved YOLO detection and bilateral segmentation network 基于改进的 YOLO 检测和双边分割网络的煤岩界面实时识别技术

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-26 DOI: 10.1016/j.undsp.2024.07.003

Shuzhan Xu , Wanming Jiang , Quansheng Liu , Hongsheng Wang , Jun Zhang , Jinlong Li , Xing Huang , Yin Bo

To improve the accuracy and efficiency of coal-rock interface recognition, this study proposes a model built on the real-time detection algorithm, you only look once (YOLO), and the lightweight bilateral segmentation network. Simultaneously, the regional similarity transformation function and dragonfly algorithm are introduced to enhance the quality of coal-rock images. The comparison with three other models demonstrates the superior edge inference performance of the proposed model, achieving a mean Average Precision (mAP) of 90.2 at the Intersection over Union (IoU) threshold of 0.50 (mAP₅₀) and 81.4 across a range of IoU thresholds from 0.50 to 0.95 (mAP_[50,95]). Furthermore, to maintain high accuracy and real-time recognition capabilities, the proposed model is optimized using the open visual inference and neural network optimization toolkit, resulting in a 144.97% increase in the mean frames per second. Experimental results on four actual coal faces confirm the efficacy of the proposed model, showing a better balance between accuracy and efficiency in coal-rock image recognition, which supports further advancements in coal mining intelligence.

为了提高煤岩界面识别的准确性和效率，本研究提出了一种基于实时检测算法 "只看一次（YOLO）"和轻量级双边分割网络的模型。同时，还引入了区域相似性变换函数和蜻蜓算法，以提高煤岩图像的质量。与其他三种模型的比较结果表明，所提出的模型具有卓越的边缘推断性能，在交集大于联合（IoU）阈值为 0.50 时，平均精度（mAP）为 90.2（mAP50），在 IoU 阈值为 0.50 到 0.95 的范围内，平均精度（mAP[50,95]）为 81.4。此外，为了保持高精确度和实时识别能力，还使用开放式视觉推理和神经网络优化工具包对所提出的模型进行了优化，使平均每秒帧数提高了 144.97%。在四个实际煤炭工作面的实验结果证实了所提模型的有效性，表明在煤岩图像识别的准确性和效率之间取得了更好的平衡，从而为煤矿智能化的进一步发展提供了支持。

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引用次数: 0

Experimental investigation on damage development and failure mechanism of shield tunnel lining under internal blast considering stratum-structure interaction 考虑地层-结构相互作用的盾构隧道衬砌在内部爆破下的损伤发展和破坏机理的实验研究

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-26 DOI: 10.1016/j.undsp.2024.07.004

Chao Liu , Guanhua Zhao , Yijie Liu , Jie Cui , Hai Liu , Shunhang Zhu

With the expansion of international terrorism and the potential threat of attacks against civil infrastructure, the dynamic response and failure modes of underground tunnels under explosive loads have become a prominent research topic. The high cost and inherent danger associated with explosion experiments have limited current research on tunnel internal explosions, particularly in the context of scaled model tests of shield tunnels. This study presents a series of scaled model tests under 1g-condition simulating internal blast events within a shield tunnel based on the prototype of the Shantou Bay Tunnel, considering the influences of surrounding stratum and equivalent explosive yield. Three different TNT explosive yields are considered in the model tests, namely 0.2, 0.4, and 1.0 kg. The model tests focus on the damage behavior and collapse modes of the shield tunnel lining under internal explosive loads. The model tests reveal that the shield tunnel is prone to damage at the joints of the tunnel crown and shoulder when subjected to internal explosive loads, with the upper half of the tunnel lining experiencing segment collapse, while the lower half remains largely undamaged. As the TNT equivalent increases, the damage area at the tunnel joints expands, and the number of segment failures in the upper half of the tunnel rises, transitioning from a damaged state to a collapsed state. The influence of “stratum-structure” interaction is investigated by comparing two models, one with overburden soil and the other positioned at the ground surface. The model tests reveal that the presence of soil pressure and confinement can significantly enhance the tunnel resistance to internal blast loads. Based on the observation of the model tests, five different damage modes of segment joints under internal explosion are proposed in this study.

随着国际恐怖主义的扩大和民用基础设施受到攻击的潜在威胁，地下隧道在爆炸载荷作用下的动态响应和失效模式已成为一个突出的研究课题。爆炸实验的高成本和固有危险性限制了目前对隧道内部爆炸的研究，特别是在盾构隧道的比例模型试验中。本研究以汕头海湾隧道原型为基础，考虑了周围地层和当量爆炸当量的影响，在 1g 条件下进行了一系列模拟盾构隧道内部爆炸事件的比例模型试验。模型试验考虑了三种不同的 TNT 爆炸当量，即 0.2、0.4 和 1.0 千克。模型试验的重点是盾构隧道衬砌在内部爆炸荷载作用下的破坏行为和坍塌模式。模型试验结果表明，盾构隧道在承受内部爆炸荷载时，隧道顶部和肩部的接缝处容易发生损坏，隧道衬砌的上半部分会发生分段坍塌，而下半部分则基本没有损坏。随着 TNT 当量的增加，隧道接缝处的损坏面积扩大，隧道上半部分的分段坍塌数量增加，从损坏状态过渡到坍塌状态。通过比较两个模型，一个是覆土模型，另一个是位于地表的模型，研究了 "地层-结构 "相互作用的影响。模型试验显示，土壤压力和封闭的存在可显著增强隧道对内部爆炸荷载的抵抗力。根据模型试验的观察结果，本研究提出了五种不同的内爆条件下节段连接的破坏模式。

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引用次数: 0

RM2D: An automated and robust laser-based framework for mobile tunnel deformation detection RM2D：基于激光的移动隧道变形自动稳健检测框架

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-16 DOI: 10.1016/j.undsp.2024.07.002

Boxun Chen , Ziyu Zhao , Lin Bi , Zhuo Wang

As mining operations extend to greater depths, the risk of deformation in high-stress tunnels increases significantly, posing a substantial threat. This study introduces a novel framework known as “robust mobility deformation detection” (RM2D), designed for real-time tunnel deformation detection. RM2D employs mobile LiDAR scanner to capture real-time point cloud data within the tunnel. This data is then voxelized and analyzed using covariance matrices to create a voxel-based multi-distribution representation of the rugged tunnel surface. Leveraging this representation, we assess deformations and scrutinize results through machine learning models to swiftly pinpoint tunnel deformation locations. Extensive experimental validation confirms the framework’s capacity to successfully detect deformations, including floor heave, side rib spalling, and roof fall, with remarkable accuracy. For deformation levels at 0.15 m, RM2D was able to successfully detect deformations with an area greater than 2 m². For deformation areas of (3 ± 0.5) m², RM2D successfully detected deformations of levels at (0.05 ± 0.01) m, and its detection capability meets the standard criteria for mining tunnel deformation detection. When compared to two conventional methods, RM2D demonstrates its real-time deformation detection capability in complex environments and on rough surfaces with precision, all at speeds below 10 km/h. Furthermore, we evaluated the predictive performance using multiple evaluation metrics and provided insights into the decision mechanism of the machine learning employed in our research, thereby offering valuable information for practical engineering applications in tunnel deformation detection.

随着采矿作业向更深的深度延伸，高应力隧道的变形风险显著增加，构成了巨大的威胁。本研究介绍了一种被称为 "鲁棒移动变形检测"（RM2D）的新型框架，专为实时检测隧道变形而设计。RM2D 利用移动式激光雷达扫描仪捕捉隧道内的实时点云数据。然后，使用协方差矩阵对这些数据进行体素化和分析，以创建基于体素的崎岖隧道表面多分布表示法。利用这种表示方法，我们通过机器学习模型评估变形并仔细检查结果，从而迅速确定隧道变形位置。广泛的实验验证证实了该框架能够成功检测变形，包括底板隆起、侧肋剥落和顶板塌陷，而且精确度极高。对于 0.15 米的变形水平，RM2D 能够成功检测到面积大于 2 平方米的变形。在变形面积为（3 ± 0.5）平方米时，RM2D 能成功检测出（0.05 ± 0.01）米的变形水平，其检测能力达到了矿山隧道变形检测的标准。与两种传统方法相比，RM2D 展示了其在复杂环境和粗糙表面上精确的实时变形检测能力，所有检测速度均低于 10 km/h。此外，我们还使用多个评估指标对预测性能进行了评估，并深入分析了研究中采用的机器学习的决策机制，从而为隧道变形检测的实际工程应用提供了有价值的信息。

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引用次数: 0

Lightweight defocus deblurring network for curved-tunnel line scanning using wide-angle lenses 使用广角镜头进行曲线隧道线扫描的轻量级去焦模糊网络

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-13 DOI: 10.1016/j.undsp.2024.06.005

Shaojie Qin , Taiyue Qi , Xiaodong Huang , Xiao Liang

High-resolution line scan cameras with wide-angle lenses are highly accurate and efficient for tunnel detection. However, due to the curvature of the tunnel, there are variations in object distance that exceed the depth of field of the lens, resulting in uneven defocus blur in the captured images. This can significantly affect the accuracy of defect recognition. While existing deblurring algorithms can improve image quality, they often prioritize results over inference time, which is not ideal for high-speed tunnel image acquisition. To address this issue, we developed a lightweight tunnel structure defect deblurring network (TSDDNet) for curved-tunnel line scanning with wide-angle lenses. Our method employs an innovative progressive structure that balances network depth and feature breadth to simultaneously achieve good performance and short inference time. The proposed depthwise ResBlocks significantly improves the parameter efficiency of the network. Additionally, the proposed feature refinement block captures the structurally similar features to enhance the image details, increasing the peak signal-to-noise ratio (PSNR). A raw dataset containing tunnel blur images was created using a high-resolution line scan camera and used to train and test our model. TSDDNet achieved a PSNR of 26.82 dB and a structural similarity index measure of 0.888, while using one-third of the parameters of comparable alternatives. Moreover, our method exhibited a higher computational speed than that of conventional methods, with inference times of 8.82 ms for a single 512 × 512 pixels image patch and 227.22 ms for completely processing a 2048 × 2560 pixels image. The test results indicated that the structural scalability of the network allows it to accommodate large inputs, making it effective for high-resolution images.

配备广角镜头的高分辨率线扫描相机在隧道探测方面具有高精确度和高效率。然而，由于隧道的弧度，物体距离的变化会超过镜头的景深，从而导致捕捉到的图像出现不均匀的虚焦模糊。这会严重影响缺陷识别的准确性。虽然现有的去模糊算法可以提高图像质量，但它们通常会优先考虑结果而不是推理时间，这对于高速隧道图像采集来说并不理想。为了解决这个问题，我们开发了一种轻型隧道结构缺陷去毛刺网络（TSDDNet），用于使用广角镜头进行曲线隧道线扫描。我们的方法采用了创新的渐进式结构，在网络深度和特征广度之间取得了平衡，从而同时实现了良好的性能和较短的推理时间。所提出的深度ResBlocks大大提高了网络的参数效率。此外，提出的特征细化块能捕捉结构相似的特征，从而增强图像细节，提高峰值信噪比（PSNR）。我们使用高分辨率线扫描相机创建了一个包含隧道模糊图像的原始数据集，用于训练和测试我们的模型。TSDDNet 的 PSNR 为 26.82 dB，结构相似度指数为 0.888，而使用的参数仅为同类替代方法的三分之一。此外，与传统方法相比，我们的方法具有更高的计算速度，单个 512 × 512 像素图像片段的推理时间为 8.82 毫秒，完全处理一幅 2048 × 2560 像素图像的推理时间为 227.22 毫秒。测试结果表明，该网络的结构可扩展性使其能够适应大型输入，从而有效地处理高分辨率图像。

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引用次数: 0

Experimental investigation on the failure characteristic and synergistic load-bearing mechanism of multi-layer linings for deep soft rock tunnels 深层软岩隧道多层衬砌的破坏特征和协同承载机理的试验研究

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-07 DOI: 10.1016/j.undsp.2024.06.004

Haibo Wang , Fuming Wang , Chengchao Guo , Lei Qin , Jun Liu , Tongming Qu

Multi-layer linings have been widely used in deep rheological soft rock tunnels for the excellent performance in preventing large-deformation hazards. Previous studies have focused on the bearing capability of multi-layer lining, however, its failure characteristics and synergistic load-bearing mechanisms under high geo-stress are still unclear. To fill the gap, three-dimensional geomechanical model tests were conducted and synergistic mechanisms were analysed in this study. The model test was divided into normal loading, excavating, and overloading stages. The surrounding rock deformation was monitored by using an improved high-precise extensometer measurement system. Results show that the largest radial deformation appears on the sidewall, followed by the floor and vault during the excavating stage. The relative convergence deformation of sidewalls springing reaches 1.32 mm. The failure characteristics of the multi-layer linings during the overloading stage undergo an evolution of stability, crack initiation, local failure, and collapse, with a safety factor of 1.0–1.6, 1.6–2.0, and 2.0–2.2, respectively. The synergistic load-bearing mechanism analysis results suggest that the early stiffness and late yielding deformation capacity of large deformation support measures play important roles in stability maintenance both in the construction and operation of deep soft rock tunnels. Therefore, the combination of yielding support or a compressible layer with reinforced support is recommended to mitigate the effect of the high geo-stress.

多层衬砌因其在防止大变形危害方面的优异性能，已被广泛应用于深层流变软岩隧道。以往的研究主要集中在多层衬砌的承载能力上，但其在高地质应力下的破坏特征和协同承载机理尚不清楚。为填补这一空白，本研究进行了三维地质力学模型试验，并分析了协同机制。模型试验分为正常加载、开挖和超载阶段。使用改进的高精度伸长计测量系统对围岩变形进行了监测。结果表明，在开挖阶段，最大的径向变形出现在侧壁，其次是底板和拱顶。侧壁弹簧的相对收敛变形达到 1.32 毫米。多层衬砌在超载阶段的破坏特征经历了稳定、裂缝起始、局部破坏和坍塌的演变过程，安全系数分别为 1.0-1.6、1.6-2.0 和 2.0-2.2。协同承载力机理分析结果表明，大变形支护措施的早期刚度和后期屈服变形能力在深层软岩隧道施工和运营的稳定性维护中发挥着重要作用。因此，建议将屈服支护或可压缩层与加固支护相结合，以减轻高地质应力的影响。

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引用次数: 0

Full-scale loading test for shield tunnel segments: Load-bearing performance and failure patterns of lining structures 盾构隧道分段全尺寸加载试验：衬砌结构的承载性能和破坏模式

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-07 DOI: 10.1016/j.undsp.2024.05.003

Gang Wei , Feifan Feng , Shiyu Huang , Tianbao Xu , Jiaxuan Zhu , Xiao Wang , Chengwei Zhu

To explore the load-bearing performance and the failure patterns of the lining structures, a full-scale loading test on the three-ring staggered assembled shield tunnel segments is carried out through a hydraulic loading system. In the experimental study, the segments’ internal force, convergence deformation, and displacement, and the bolts’ internal force, are analyzed. According to the experimental results, the relationship between internal force and deformation is obtained to determine the residual bearing capacity of the shield tunnel at each stage. Three stages are specified for the evolution of the segment’s maximum bending moment during the loading process, in which, the elastic stage is the main and longest stage, in which the bending moment of the segment increases the most. There are two stages for convergence deformation development and segment misalignment development. At the end of loading, the segment’s maximum positive and negative convergence values reach 61.22 and −57.69 mm, respectively. Besides, the maximum segment misalignment is 3.67 mm, which occurs in the direction of 90°. The segment cracks when its maximum convergence value reaches 25.03 mm. Moreover, there are signs of fracturing on the waist joint of the segment when its maximum convergence value reaches 32.73 mm. The concrete at the waist joint starts fracturing in pieces when the segment’s maximum convergence value reaches 38.93 mm, which is defined as the type of shear failure. Finally, the bearing capacity of shield tunnels during segment failure period can be evaluated by using the corresponding relationship between deformation and internal force.

为探索衬砌结构的承载性能和破坏模式，通过液压加载系统对三环交错拼装盾构隧道节段进行了全尺寸加载试验。在实验研究中，分析了分段的内力、收敛变形和位移，以及螺栓的内力。根据实验结果，得出内力与变形之间的关系，从而确定盾构隧道在每个阶段的剩余承载力。加载过程中，区段最大弯矩的演变分为三个阶段，其中弹性阶段是最主要和最长的阶段，在此阶段区段弯矩增加最大。收敛变形发展和节段错位发展分为两个阶段。加载结束时，节段的最大正收敛值和负收敛值分别达到 61.22 毫米和-57.69 毫米。此外，最大节段偏差为 3.67 mm，发生在 90° 方向上。当最大收敛值达到 25.03 mm 时，分段出现裂缝。此外，当最大收敛值达到 32.73 mm 时，分段的腰部连接处出现断裂迹象。当区段的最大收敛值达到 38.93 毫米时，腰部连接处的混凝土开始碎裂，这被定义为剪切破坏类型。最后，可以利用变形和内力之间的相应关系来评估盾构隧道在断面破坏期间的承载能力。

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引用次数: 0

Grain-based coupled thermo-mechanical modeling for stressed heterogeneous granite under thermal shock 热冲击下受力异质花岗岩的基于晶粒的热机械耦合建模

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-09-07 DOI: 10.1016/j.undsp.2024.06.003

Zheng Yang , Ming Tao , Wenbin Fei , Tubing Yin , P.G. Ranjith

Microscopic damage and macroscopic mechanical properties of granite under the coupling effect of thermal load and initial stress are crucial considerations for the safe construction of underground geo-energy engineering. However, visualizing real-time micro-crack processes in rocks under high-temperature and high-pressure conditions using the current experimental techniques remains challenging. In this study, a numerical method is developed to analyze the thermally induced damage in heterogeneous granite under the coupled influence of initial stress and thermal loading. A biaxial thermo-mechanical grain-based model considering real mineral distribution is established based on digital image processing technology, the grain-based modeling method, and heat conduction theory. The microscopic parameters are calibrated and the effectiveness of the model is verified based on thermal shock and uniaxial compression experiments. The thermal destruction mechanism of granite under initial stress from a microscopic perspective was unveiled for the first time. During the thermal shock process, the stress within the rock does not remain constant at the initial stress value. Instead, it changes continuously with the progression of heat conduction. The impact of the initial stress on the thermally induced cracks is relatively minor. Cooling causes more damage to the rock than heating during thermal shock. The intragranular cracks of quartz consistently outnumber other intragranular or intergranular cracks during thermal shock. The initial stress and thermal shock damage enhance and weaken the biaxial peak strength of granite, respectively. The weakening effect of thermal shock on the peak strength becomes more pronounced at a higher initial stress. These research findings and proposed research techniques contribute to the management and optimization of underground geo-energy engineering.

在热负荷和初始应力的耦合作用下，花岗岩的微观损伤和宏观力学性能是地下地质能源工程安全施工的关键因素。然而，利用现有的实验技术对岩石在高温高压条件下的微裂缝过程进行实时可视化仍然具有挑战性。本研究开发了一种数值方法，用于分析在初始应力和热负荷耦合影响下，异质花岗岩中的热诱导损伤。基于数字图像处理技术、基于晶粒的建模方法和热传导理论，建立了考虑真实矿物分布的双轴热机械晶粒模型。基于热冲击和单轴压缩实验，校准了微观参数并验证了模型的有效性。首次从微观角度揭示了花岗岩在初始应力作用下的热破坏机理。在热冲击过程中，岩石内部的应力并不会保持恒定的初始应力值。相反，它随着热传导的进行而不断变化。初始应力对热裂缝的影响相对较小。在热冲击过程中，冷却比加热对岩石造成的破坏更大。在热冲击过程中，石英的粒内裂缝始终多于其他粒内或粒间裂缝。初始应力和热冲击破坏分别增强和削弱了花岗岩的双轴峰值强度。当初始应力较大时，热冲击对峰值强度的削弱作用更加明显。这些研究成果和建议的研究技术有助于地下地质能源工程的管理和优化。

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引用次数: 0

Model test on the effects of shield machine cutterhead vibration on tunnel face stability in sandy ground

IF 8.2 1区工程技术 Q1 ENGINEERING, CIVIL

Underground Space

Pub Date : 2024-08-30 DOI: 10.1016/j.undsp.2024.04.009

Meng-Bo Liu , Jun-Hua Xiao , Shao-Ming Liao , Zhi-Yong Liu , Jun-Zuo He , Yan-Qing Men , Jia-Cheng Sun

Face stability is one of the essential problems in shield tunneling. When tunneling in cobble stratum or mixed face ground conditions, significant cutting-induced cutterhead vibration would occur and affect the face stability. To reveal the mechanism and effect of vibration on the tunnel face stability, a transparent tunnel model with a movable vibration exciter was designed and a series of model tests were performed under different vibration magnitudes A_a and frequencies f. Meanwhile, particle image velocimetry was used to reveal the displacement field and the failure pattern of the tunnel face. The test results indicate that the cutting-induced vibration produces a significant reduction effect on the tunnel face stability, as expressed by the increase of the face support pressure and the failure zone when the vibration magnitude and frequency increase. Compared with the static unloading conditions, the width of the failure wedge L_wt increased by about 5.75% and 35.66% for the loose and dense sand, respectively, under dynamic unloading conditions (A_a = 0.2g, f = 10 Hz). The limit support pressure increased up to about 0.20γD at a vibration of 0.3g and 50 Hz, much larger than those of static conditions, which were about 0.08γD–0.09γD. An observable self-stabilizing arch can be formed in dense sand under static unloading conditions, while under dynamic unloading conditions, the long-time stable soil arch would not occur. The contributions of this paper could provide an insightful understanding of the effects of cutterhead vibration on tunnel face stability.

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引用次数: 0