Size and quantity of fractured zone and non-fractured zone are controlled by cracks contained in deep rock masses. Zonal disintegration mechanism is strongly dependent on the interaction among cracks. The strong inter...Size and quantity of fractured zone and non-fractured zone are controlled by cracks contained in deep rock masses. Zonal disintegration mechanism is strongly dependent on the interaction among cracks. The strong interaction among cracks is investigated using stress superposition principle and the Chebyshev polynomials expansion of the pseudo-traction. It is found from numerical results that crack nucleation, growth and coalescence lead to failure of deep crack- weakened rock masses. The stress redistribution around the surrounding rock mass induced by unloading excavation is studied. The effect of the excavation time on nucleation, growth, interaction and coalescence of cracks was analyzed. Moreover, the influence of the excavation time on the size and quantity of fractured zone and non-fractured zone was given. When the excavation time is short, zonal disintegration phenomenon may occur in deep rock masses. It is shown from numerical results that the size and quantity of fractured zone increase with decreasing excavation time, and the size and quantity of fractured zone increase with the increasing value of in-situ geostress.展开更多
Residue deep hydrotreating(RDHT)process was developed by the Research Institute of Petroleum Processing(RIPP)to provide high quality feedstock for deep catalytic cracking(DCC)process.In this research work,the effects ...Residue deep hydrotreating(RDHT)process was developed by the Research Institute of Petroleum Processing(RIPP)to provide high quality feedstock for deep catalytic cracking(DCC)process.In this research work,the effects of RDHT process and reaction severity on heteroatom removal,hydrogen content increase,hydrocarbon composition improvement,and DCC product yields were studied.It was showed that the RDHT process can effectively reduce heteroatoms,increase hydrogen content and improve the hydrocarbon compositions,which can contribute to an increase of light olefins yield in DCC unit.展开更多
In this study, it was assumed that three-dimensional penny-shaped cracks existed in deep rock masses. A new non-Euclidean model was established, in which the effects of penny- shaped cracks and axial in-situ stress on...In this study, it was assumed that three-dimensional penny-shaped cracks existed in deep rock masses. A new non-Euclidean model was established, in which the effects of penny- shaped cracks and axial in-situ stress on zonal disintegration of deep rock masses were taken into account. Based on the non-Euclidean model, the stress intensity factors at tips of the penny- shaped cracks were determined. The strain energy density factor was applied to investigate the occurrence of fractured zones. It was observed from the numerical results that the magnitude and location of fractured zones were sensitive to micro- and macro-mechanical parameters, as well as the value of in-situ stress. The numerical results were in good agreement with the experimental data.展开更多
To analyze and predict the mechanical behaviors of deep hard rocks,some key issues concerning rock fracturing mechanics for deep hard rock excavations are discussed.First,a series of apparatuses and methods have been ...To analyze and predict the mechanical behaviors of deep hard rocks,some key issues concerning rock fracturing mechanics for deep hard rock excavations are discussed.First,a series of apparatuses and methods have been developed to test the mechanical properties and fracturing behaviors of hard rocks under high true triaxial stress paths.Evolution mechanisms of stress-induced disasters in deep hard rock excavations,such as spalling,deep cracking,massive roof collapse,large deformation and rockbursts,have been recognized.The analytical theory for the fracturing process of hard rock masses,including the three-dimensional failure criterion,stress-induced mechanical model,fracturing degree index,energy release index and numerical method,has been established.The cracking-restraint method is developed for mitigating or controlling rock spalling,deep cracking and massive collapse of deep hard rocks.An energy-controlled method is also proposed for the prevention of rockbursts.Finally,two typical cases are used to illustrate the application of the proposed methodology in the Baihetan caverns and Bayu tunnels of China.展开更多
有效的道路裂缝检测是保障道路安全的关键。针对现有道路裂缝检测方法效率低,检测结果易受检测环境影响的问题,文章结合深度学习与计算机视觉技术,在DeepLabV3+架构的基础上提出了一种适用于复杂道路场景下的道路裂缝检测网络Crack-Deep...有效的道路裂缝检测是保障道路安全的关键。针对现有道路裂缝检测方法效率低,检测结果易受检测环境影响的问题,文章结合深度学习与计算机视觉技术,在DeepLabV3+架构的基础上提出了一种适用于复杂道路场景下的道路裂缝检测网络Crack-Deeplab。Crack-Deeplab引入新颖的网络模块和结构设计,具有轻量化、强泛化的特点以及精细分割的能力。文章基于数据集Crack500进行试验,验证和测试数据集的裂缝交并比(Intersection over Union,IoU)分别达到了0.67和0.58,比现有的网络有明显提高;另外,采用复杂环境下拍摄的广州大学校内道路图片对该网络进行实际工程验证,基于Crack500数据训练的Crack-Deeplab在无需新增附加训练数据的情况下,能精准识别和分割出不同场景及环境下校内道路的裂缝,证明了该方法的有效性和鲁棒性,以及在实际工程中的应用价值。展开更多
针对裂缝图像背景复杂噪声多导致检测精度差的问题,设计了基于特征金字塔注意力的裂缝检测模型(Crack Detection Network Based on Feature Pyramid Attention, FPA)。模型以VGG16为特征提取网络。首先,在模型中引入特征金字塔注意力模...针对裂缝图像背景复杂噪声多导致检测精度差的问题,设计了基于特征金字塔注意力的裂缝检测模型(Crack Detection Network Based on Feature Pyramid Attention, FPA)。模型以VGG16为特征提取网络。首先,在模型中引入特征金字塔注意力模块产生像素级注意力,在扩大感受野的同时减少空间分辨率损失的影响。然后,提出多尺度特征融合模块MFF,将具有更大感受野的特征图与每个阶段的特征图进行特征融合,在低层特征中引入语义信息丰富的高层特征,提升对不同尺寸裂缝的检测能力。最后,将全局上下文模块添加到每个分支的特征融合后,提高裂缝区域的权重,减少特征融合过程中低层特征所携带的噪声干扰。通过与多个模型进行对比,所提模型有良好的抗噪性。在CrackTree260数据集上,MPA、MIoU、F-measure指标比其它模型平均提升了3.84、2.09、2.22个百分点。展开更多
基金supported by the National Natural Science Foundation of China(Nos.50490275 and 50778184)
文摘Size and quantity of fractured zone and non-fractured zone are controlled by cracks contained in deep rock masses. Zonal disintegration mechanism is strongly dependent on the interaction among cracks. The strong interaction among cracks is investigated using stress superposition principle and the Chebyshev polynomials expansion of the pseudo-traction. It is found from numerical results that crack nucleation, growth and coalescence lead to failure of deep crack- weakened rock masses. The stress redistribution around the surrounding rock mass induced by unloading excavation is studied. The effect of the excavation time on nucleation, growth, interaction and coalescence of cracks was analyzed. Moreover, the influence of the excavation time on the size and quantity of fractured zone and non-fractured zone was given. When the excavation time is short, zonal disintegration phenomenon may occur in deep rock masses. It is shown from numerical results that the size and quantity of fractured zone increase with decreasing excavation time, and the size and quantity of fractured zone increase with the increasing value of in-situ geostress.
基金This work was supported by the Science and Technology Project of Sinopec(118015-1).
文摘Residue deep hydrotreating(RDHT)process was developed by the Research Institute of Petroleum Processing(RIPP)to provide high quality feedstock for deep catalytic cracking(DCC)process.In this research work,the effects of RDHT process and reaction severity on heteroatom removal,hydrogen content increase,hydrocarbon composition improvement,and DCC product yields were studied.It was showed that the RDHT process can effectively reduce heteroatoms,increase hydrogen content and improve the hydrocarbon compositions,which can contribute to an increase of light olefins yield in DCC unit.
基金supported by the 973 Project(No.2014CB046903)the National Natural Science Foundation of China(Nos.51325903 and 51279218)the Natural Science Foundation Project of CQ CSTC(Nos.CSTC2013KJRC-1JRCCJ30001 and CSTC2013JCYJYS0005)
文摘In this study, it was assumed that three-dimensional penny-shaped cracks existed in deep rock masses. A new non-Euclidean model was established, in which the effects of penny- shaped cracks and axial in-situ stress on zonal disintegration of deep rock masses were taken into account. Based on the non-Euclidean model, the stress intensity factors at tips of the penny- shaped cracks were determined. The strain energy density factor was applied to investigate the occurrence of fractured zones. It was observed from the numerical results that the magnitude and location of fractured zones were sensitive to micro- and macro-mechanical parameters, as well as the value of in-situ stress. The numerical results were in good agreement with the experimental data.
基金financial support from the National Natural Science Foundation of China(Grant Nos.51839003 and 41827806)Liaoning Revitalization Talents Program of China(Grant No.XLYCYSZX1902)。
文摘To analyze and predict the mechanical behaviors of deep hard rocks,some key issues concerning rock fracturing mechanics for deep hard rock excavations are discussed.First,a series of apparatuses and methods have been developed to test the mechanical properties and fracturing behaviors of hard rocks under high true triaxial stress paths.Evolution mechanisms of stress-induced disasters in deep hard rock excavations,such as spalling,deep cracking,massive roof collapse,large deformation and rockbursts,have been recognized.The analytical theory for the fracturing process of hard rock masses,including the three-dimensional failure criterion,stress-induced mechanical model,fracturing degree index,energy release index and numerical method,has been established.The cracking-restraint method is developed for mitigating or controlling rock spalling,deep cracking and massive collapse of deep hard rocks.An energy-controlled method is also proposed for the prevention of rockbursts.Finally,two typical cases are used to illustrate the application of the proposed methodology in the Baihetan caverns and Bayu tunnels of China.
文摘有效的道路裂缝检测是保障道路安全的关键。针对现有道路裂缝检测方法效率低,检测结果易受检测环境影响的问题,文章结合深度学习与计算机视觉技术,在DeepLabV3+架构的基础上提出了一种适用于复杂道路场景下的道路裂缝检测网络Crack-Deeplab。Crack-Deeplab引入新颖的网络模块和结构设计,具有轻量化、强泛化的特点以及精细分割的能力。文章基于数据集Crack500进行试验,验证和测试数据集的裂缝交并比(Intersection over Union,IoU)分别达到了0.67和0.58,比现有的网络有明显提高;另外,采用复杂环境下拍摄的广州大学校内道路图片对该网络进行实际工程验证,基于Crack500数据训练的Crack-Deeplab在无需新增附加训练数据的情况下,能精准识别和分割出不同场景及环境下校内道路的裂缝,证明了该方法的有效性和鲁棒性,以及在实际工程中的应用价值。
文摘针对裂缝图像背景复杂噪声多导致检测精度差的问题,设计了基于特征金字塔注意力的裂缝检测模型(Crack Detection Network Based on Feature Pyramid Attention, FPA)。模型以VGG16为特征提取网络。首先,在模型中引入特征金字塔注意力模块产生像素级注意力,在扩大感受野的同时减少空间分辨率损失的影响。然后,提出多尺度特征融合模块MFF,将具有更大感受野的特征图与每个阶段的特征图进行特征融合,在低层特征中引入语义信息丰富的高层特征,提升对不同尺寸裂缝的检测能力。最后,将全局上下文模块添加到每个分支的特征融合后,提高裂缝区域的权重,减少特征融合过程中低层特征所携带的噪声干扰。通过与多个模型进行对比,所提模型有良好的抗噪性。在CrackTree260数据集上,MPA、MIoU、F-measure指标比其它模型平均提升了3.84、2.09、2.22个百分点。
