检索结果-内蒙古大学图书馆

Numerical investigation on the dynamic progressive fracture mechanism of cracked chevron notched semi-circular bend specimens in split Hopkinson pressure bar tests

引用

ENGINEERING FRACTURE MECHANICS 2017年 184卷 202-217页

作者： Du, Hongbo Dai, Feng Xia, Kaiwen xu, nuwen xu, Yuan Sichuan Univ Coll Water Resources & Hydropower State Key Lab Hydraul & Mt River Engn Chengdu 610065 Sichuan Peoples R China Univ Toronto Dept Civil Engn Toronto ON M5S 1A4 Canada

The cracked chevron notched semi-circular bend (CCNSCB) method has been utilized in split Hopkinson pressure bar (SHPB) tests to measure the rock dynamic mode I fracture toughness. However, the measuring principle has never been thoroughly evaluated. In this study, a three-dimensional discrete element method has been employed to numerically investigate the dynamic fracture mechanism of CCNSCB specimens in SHPB testing considering different loading rates and supporting spans. Our results show that, even if the dynamic force balance can be efficiently satisfied, the conventional quasi-static analysis can still be questionable. For specimens with smaller supporting spans, the developing crack fronts are rather curved during the loading process, and the critical crack length is highly dependent on the loading rates. While for specimens with a large supporting span, the crack profiles are less affected and the critical crack fronts are finely confined within the chevron ligament with few undesirable damages. Thus, the CCNSCB method with a larger supporting span appear to be sound in the SHPB tests for measuring dynamic mode I fracture toughness of rocks. (C) 2017 Elsevier Ltd. All rights reserved.

关键词： Fracture toughness CCNSCB SHPB Rate dependence Discrete element method

来源：评论

学校读者我要写书评

暂无评论

Microseismic early warning of surrounding rock mass deformation in the underground powerhouse of the Houziyan hydropower station, China

引用

TUNNELLING AND UNDERGROUND SPACE TECHNOLOGY 2017年 62卷 64-74页

作者： Dai, Feng Li, Biao xu, nuwen Zhu, Yongguo Sichuan Univ Coll Water Resource & Hydropower State Key Lab Hydraul & Mt River Engn Chengdu 610065 Sichuan Provinc Peoples R China China Guodian Dadu River Houziyan Hydropower Dev Kangding 610041 Sichuan Provinc Peoples R China

Early warning of surrounding rock mass deformation and failure is of great significance for an underground powerhouse and remains a challenge in rock engineering. The microseismic (MS) monitoring technique was adopted for surrounding rock mass deformation forecasting in the underground powerhouse of the Houziyan hydropower station. By analysing the evolution laws of multiple MS parameters, including the MS event count, the energy release, the energy index, the apparent volume, the dominant frequency, the b value, and the fractal dimension, typical abnormal variations prior to a large deformation were obtained, and these MS parameters were found to behave differently. The MS event count appeared with escalating fluctuation as the energy demonstrated a gradually accelerating increase, while the energy index sharply increased with a stable increase of the cumulative apparent volume. Moreover, the dominant frequency, the b value, and the fractal dimension decreased. Accordingly, these MS abnormalities can be regarded as indicators prior to a large deformation of surrounding rock mass. A comprehensive analysis of these MS parameters could allow for better warning and risk assessment of surrounding rock mass deformation and failure in underground caverns. (C) 2016 Elsevier Ltd. All rights reserved.

关键词： Underground powerhouse Microseismic monitoring Deformation Early warning Houziyan hydropower station

来源：评论

学校读者我要写书评

暂无评论

Effects of coupled static and dynamic strain rates on mechanical behaviors of rock-like specimens containing pre-existing fissures under uniaxial compression

引用

CANADIAN GEOTECHNICAL JOURNAL 2018年第5期55卷 640-652页

作者： Feng, Peng Dai, Feng Liu, Yi xu, nuwen Fan, Pengxian Sichuan Univ Coll Water Resource & Hydropower State Key Lab Hydraul & Mt River Engn Chengdu 610065 Sichuan Peoples R China State Key Lab Disaster Prevent & Mitigat Explos I Nanjing 210007 Jiangsu Peoples R China

Rocks containing pre-existing fissures in underground engineering are likely to be subjected to static pre-stress and dynamic loads simultaneously. Understanding the deformation and failure mechanism of fissured rocks under coupled static and dynamic strain rates is beneficial for the stability assessment of rock engineering structures. This study experimentally investigates the mechanical behaviors of fissured specimens under coupled static and dynamic loads with different loading parameters. Our experiments reveal that the coupled static-dynamic strain rates significantly affect the strength, deformation, energy characteristics, and failure mode of fissured specimens. For each dynamic strain rate, the strength and elastic modulus of specimens feature an increase first as the static pre-stress increases up to half of the uniaxial compression strength, and then a decrease. However, for each static pre-stress of coupled loads, the strength and elastic modulus increase noticeably with increasing dynamic strain rate. From the perspective of energy partition, for each static pre-stress, the higher dynamic strain rate induces greater energy dissipation of the specimens during the coupled loading, and more elastic energy is released at the end of loading. Moreover, for each dynamic strain rate, the pre-stress of half uniaxial compression strength induces the highest released elastic energy.

关键词： coupled loads strain rate mechanical behaviors energy characteristics fissured specimen

来源：评论

学校读者我要写书评

暂无评论

Experimental Investigation of the Influence of Joint Geometric Configurations on the Mechanical Properties of Intermittent Jointed Rock Models Under Cyclic Uniaxial Compression

引用

ROCK MECHANICS AND ROCK ENGINEERING 2017年第6期50卷 1453-1471页

作者： Liu, Yi Dai, Feng Fan, Pengxian xu, nuwen Dong, Lu Sichuan Univ Coll Water Resource & Hydropower State Key Lab Hydraul & Mt River Engn Chengdu 610065 Sichuan Peoples R China PLA Univ Sci & Technol State Key Lab Disaster Prevent & Mitigat Explos & Nanjing 210007 Jiangsu Peoples R China

Intermittent joints in rock mass are quite sensitive to cyclic loading conditions. Understanding the fatigue mechanical properties of jointed rocks is beneficial for rational design and stability analysis of rock engineering projects. This study experimentally investigated the influences of joint geometry (i.e., dip angle, persistency, density and spacing) on the fatigue mechanism of synthetic jointed rock models. Our results revealed that the stress-strain curve of jointed rock under cyclic loadings is dominated by its curve under monotonic uniaxial loadings;the terminal strain in fatigue curve is equal to the post-peak strain corresponding to the maximum cyclic stress in the monotonic stress-strain curve. The four joint geometrical parameters studied significantly affect the fatigue properties of jointed rocks, including the irreversible strains, the fatigue deformation modulus, the energy evolution, the damage variable and the crack coalescence patterns. The higher the values of the geometrical parameters, the lower the elastic energy stores in this jointed rock, the higher the fatigue damage accumulates in the first few cycles, and the lower the fatigue life. The elastic energy has certain storage limitation, at which the fatigue failure occurs. Two basic micro-cracks, i.e., tensile wing crack and shear crack, are observed in cyclic loading and unloading tests, which are controlled principally by joint dip angle and persistency. In general, shear cracks only occur in the jointed rock with higher dip angle or higher persistency, and the jointed rock is characterized by lower fatigue strength, larger damage variable and lower fatigue life.

关键词： Jointed rock Cyclic loading Geometric configuration Mechanical property

来源：评论

学校读者我要写书评

暂无评论

Deformation Forecasting of Surrounding Rock Mass Based on Correlation between Frequency and Fracture Scale of Microseismicity

引用

ADVANCES IN CIVIL ENGINEERING 2018年第1期2018卷

作者： Xiao, Peiwei Qian, Bo Jiang, Peng xu, nuwen Li, Biao China Guodian DaDu River Hydropower Dev Co Ltd Chengdu 610016 Sichuan Peoples R China Sichuan Univ State Key Lab Hydraul & Mt River Engn Coll Water Resource & Hydropower Chengdu 610065 Sichuan Peoples R China Southwest Petr Univ Sch Geosci & Technol Chengdu 610500 Sichuan Peoples R China

Th macroscopic deformation and failure of engineering rock mass may occur as a result of evolution and breakdown of its internal microfracture. Therefore, the macroscopic state of rock mass can be obtained from fracture scale of microfracture in real time. To assess instability and predict macroscopic deformation and failure of engineering rock mass, a time-frequency analysis technique based on S transform was proposed to investigate microseismic waveform and reveal the correlation between macroscopic deformation failure and microseismic frequency characteristics of engineering rock mass in combination with fracture scale. To minimize the influence of external factors on parameters calculated, a significant amount of microseismic data from three large-scale hydropower projects in southwestern China was collected as the statistical sample. The analysis of correlation between fracture scale and frequency characteristics of microseismic events was carried out based on the statistical sample. Combining with microseismic data and multipoint extensometers in the underground powerhouse of the Houziyan hydropower station, engineering verification was conducted. The result shows that the high-frequency components decrease and microseismic signals display low-frequency characteristic as the fracture scale increases;the microseismic high-frequency components decreased at first and then increased during the deformation process of surrounding rock mass, and the frequency of microseismic events shifts from high band to a lower one before deformation.

关键词：

来源：评论

学校读者我要写书评

暂无评论

Microseismic Monitoring of the Left Bank Slope at the Baihetan Hydropower Station, China

引用

ROCK MECHANICS AND ROCK ENGINEERING 2017年第1期50卷 225-232页

作者： Dai, Feng Li, Biao xu, nuwen Meng, Guotao Wu, Jiayao Fan, Yilin Sichuan Univ Coll Water Resource & Hydropower State Key Lab Hydraul & Mt River Engn Chengdu 610065 Sichuan Peoples R China HydroChina Itasca R&D Ctr Hangzhou 310014 Zhejiang Peoples R China China Three Gorges Corp Beijing 100038 Peoples R China

The Baihetan hydropower station is a large-scale step hydropower project recently constructed on the Jinshajiang River in southwest China. The microseismic (MS) monitoring system has been successfully implemented at the rock slope from November 10, 2014. A total of 18 uniaxial accelerometers with a natural frequency of 10 kHz deployed in boreholes drilled from the sidewalls of different tunnels have been installed. After filtering out the noisy events, 833 MS events have been recorded within a given volume of interest during the selected period from November 10, 2014, to March 20, 2015. A plot of the cumulative number of MS events recorded during the selected period shows one period of increased MS activity, namely December 5, 2014, to January 10, 2015.

关键词： Rock slope Microseismic monitoring Field observation Baihetan hydropower station

来源：评论

学校读者我要写书评

暂无评论

Comprehensive evaluation of excavation-damaged zones in the deep underground caverns of the Houziyan hydropower station, Southwest China

引用

BULLETIN OF ENGINEERING GEOLOGY AND THE ENVIRONMENT 2017年第1期76卷 275-293页

作者： xu, nuwen Dai, Feng Li, Biao Zhu, Yongguo Zhao, Tao Yang, Diansen Sichuan Univ Coll Water Resource & Hydropower State Key Lab Hydraul & Mt River Engn Chengdu 610065 Sichuan Peoples R China China Guodian Dadu River Houziyan Hydropower Dev Kangding 626005 Sichuan Peoples R China Chinese Acad Sci Inst Rock & Soil Mech State Key Lab Geomech & Geotech Engn Wuhan 430070 Hubei Peoples R China

The disturbance of a rock mass by blasting or stress redistribution can significantly influence the overall performance of an underground excavation. The characteristics of excavation-damaged zones (EDZs) during the excavation of underground caverns at the Houziyan hydropower station in Sichuan Province, China, were investigated using various in situ tests. This study presents a comprehensive evaluation of the evolution of EDZs in the surrounding rock mass in the underground powerhouse caverns using microseismic (MS) monitoring and conventional testing methods, including multi-point extensometers, acoustic wave testing and borehole TV. First, by analyzing a series of conventional testing and MS monitoring results, the deformation and failure characteristics of the surrounding rock mass were determined. Next, the formation mechanisms of fractures in the surrounding rock mass subjected to excavation-induced unloading in the underground powerhouse caverns were determined. The relationships between the EDZs of the surrounding rock mass, crack evolution and construction status were then analyzed to investigate the crack formation, development and coalescence processes. Finally, the thicknesses of the EDZs were quantitatively determined, the relationships between the fracture evolution and construction progress were established, and the EDZ formation and evolution mechanisms were evaluated. The results not only provide direct data for geological exploration but also contribute to optimizing excavation design and support for analyzing the deformation behaviors of underground powerhouse caverns.

关键词： Excavation-damaged zone Underground powerhouse Microseismic monitoring Acoustic wave testing Borehole TV Multi-point extensometer

来源：评论

学校读者我要写书评

暂无评论

白鹤滩水电站左岸边坡开挖卸荷过程微震视应力特征研究

引用

岩石力学与工程学报 2018年第A02期37卷 4133-4141页

作者：张敏徐奴文陈文夫谭尧升戴峰蒋雄李韬四川大学水力学与山区河流开发保护国家重点实验室四川成都610065 成都理工大学地质灾害防治与地质环境保护国家重点实验室四川成都610059 中国长江三峡集团公司北京100038 中国矿业大学

微震事件视应力可反映岩质边坡应力变化情况。以白鹤滩水电站左岸边坡为研究背景,分析岩质边坡爆破开挖卸荷过程微震视应力与能量、地震矩的关系,重点研究微震视应力在爆破开挖前后变化特征,结合数值模拟,通过微震视应力变化情况开展边... 详细信息

微震事件视应力可反映岩质边坡应力变化情况。以白鹤滩水电站左岸边坡为研究背景,分析岩质边坡爆破开挖卸荷过程微震视应力与能量、地震矩的关系,重点研究微震视应力在爆破开挖前后变化特征,结合数值模拟,通过微震视应力变化情况开展边坡稳定性评价。研究结果表明:微震视应力随地震矩和辐射能量的增大而增大;高视应力微震事件的出现可反映工程施工中的强烈爆破开挖扰动程度;通过微震视应力分布特征圈定的主要损伤区与RFPA3D数值模拟结果基本吻合;视应力急剧下降,累积视体积呈增长趋势,是边坡围岩变形的前兆信号。研究成果可为基于微震监测的类似大型岩石边坡稳定性评价提供参考。

关键词：岩石力学边坡稳定视应力微震监测视体积白鹤滩水电站

来源：评论

学校读者我要写书评

暂无评论

软岩巷道掘进期间微震活动特征及稳定性分析

引用

采矿与安全工程学报 2018年第1期35卷 10-18页

作者：王雷王琦李术才徐奴文潘锐何满潮许英东张皓杰山东大学岩土与结构工程研究中心山东济南250061 中国矿业大学(北京)深部岩土力学与地下工程国家重点实验室北京100083 四川大学水力学与山区河流开发保护国家重点实验室四川成都610065

为明确软岩巷道掘进期间围岩变形破坏机制,在梁家煤矿4106材料巷构建微震监测系统,监测围岩破坏情况,分析软岩巷道掘进期间微震活动特征,研究微震活动与巷道收敛变形、支护构件受力的相互关系。结果表明:1)巷道掘进过程中,微震事件矩震... 详细信息

为明确软岩巷道掘进期间围岩变形破坏机制,在梁家煤矿4106材料巷构建微震监测系统,监测围岩破坏情况,分析软岩巷道掘进期间微震活动特征,研究微震活动与巷道收敛变形、支护构件受力的相互关系。结果表明:1)巷道掘进过程中,微震事件矩震级主要集中在-2.770~0.589,微震事件矩震级平均值为-1.5;微震事件分为3个区域,即高密度区域(0~2 m)、中密度区域(2~6 m)和低密度区域(6 m以外)。2)微震事件主要聚集在巷道顶板、肩部和底板,为巷道围岩破裂严重区域。3)微震事件聚集规律与巷道收敛变形、支护构件受力规律具有一致性。研究结果表明利用微震监测系统定量监测围岩破坏情况,结合传统监测技术是可行的,弥补了传统定性分析围岩破坏的局限性。

关键词：软岩巷道微震监测定量评价关键部位

来源：评论

学校读者我要写书评

暂无评论

Cyclic flattened Brazilian disc tests for measuring the tensile fatigue properties of brittle rocks

引用

REVIEW OF SCIENTIFIC INSTRUMENTS 2017年第8期88卷 083902页

作者： Liu, Yi Dai, Feng xu, nuwen Zhao, Tao Sichuan Univ Coll Water Resource & Hydropower StateKey Lab Hydraul & Mt River Engn Chengdu 610065 Sichuan Peoples R China

We propose a cyclic flattened Brazilian disc (FBD) testing method to measure the tensile fatigue properties of brittle rocks. Our method has obvious merits in its specimen preparation and experimental operation. Two parallel flattens are introduced in the disc specimen, which facilitate easily and uniformly loading the specimen without special loading devices required. Moreover, the contact regions between two flattens and loading planes barely change during the entire loading and unloading process, ensuring a consistent contact condition. With certain appropriate loading angles, this method guarantees that the very first breakage of the specimen occurs at the center of the disc, which is the prerequisite of the Brazilian-type indirect tensile tests. To demonstrate our new method, nine cyclic FBD tensile tests are conducted. The fatigue load-deformation characteristics of FBD specimens are revealed. The tensile fatigue lives of tested specimens are observed to increase with the increase in cyclic loading frequency. Our proposed method provides a convenient and reliable approach to indirectly measure the fatigue tensile properties of brittle rocks and other brittle solids subjected to cyclic tensile loadings. Published by AIP Publishing.

关键词： Tensile testing

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：