Mechanical behaviors of conjugate-flawed rocks subjected to coupled static–dynamic compression     

Feng  Peng  Zhao  Jiachen  Dai  Feng  Wei  Mingdong  Liu  Bo 《Acta Geotechnica》2022,17(5):1765-1784

Conjugate flaws widely exist in rock masses and play a significant role in their deformation and strength properties. Understanding the mechanical behaviors of rock masses containing conjugate flaws is conducive to rock engineering stability assessment and the related supporting design. This study experimentally investigates the mechanical properties of conjugate-flawed sandstone specimens under coupled static–dynamic compression, thereby providing insight into how conjugate fractures interact to produce tracing tensional joints. Results indicate that the coupled compressive strength and the dynamic elastic modulus of conjugate-flawed rock specimens show remarkable loading rate dependence. For a fixed strain rate, the specimen with a static pre-stress equal to 60% of its uniaxial compressive strength has the highest coupled strength. Besides, both higher static pre-stress and strain rate can induce smaller mean fragment size and greater fractal dimension of the specimen, corresponding to a more uniform distribution of the broken fragments with smaller sizes. When the static pre-stress is lower than 80%UCS, the flawed specimen under a higher strain rate is characterized by higher absorbed energy. However, when the pre-stress equals 80%UCS, the value of the energy absorbed by the specimen in the dynamic loading process is negative due to the release of the preexisting considerable elastic strain energy input from the static pre-loading. As for the failure modes, cracks always penetrate the preexisting ipsilateral flaw tips to form anti-wing cracks. Under dynamic loading, the conjugate-flawed specimen generally shows tensile failure at a low strain rate, while the shear failure dominates at a high strain rate. In addition, based on progressive failure processes of the conjugate-flawed rock specimens, the evolution of tracing tensional joints in the field is discussed.

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Hydro-mechanical coupled analyses on wall deformations caused by deep excavations and dewatering in a confined aquifer     

Peng  Chen-Xin  Liu  Nian-Wu  Li  Ming-Guang  Zhen  Liang  Chen  Jin-Jian 《Acta Geotechnica》2022,17(6):2465-2479

Acta Geotechnica - This study investigates the effect of dewatering on wall deformations of deep excavations through numerical analyses. A hydro-mechanical coupled method...  相似文献   

Dynamic multifield coupling model of gas drainage and a new remedy method for borehole leakage     

Zhang  Junxiang  Li  Bo  Liu  Yanwei  Li  Peng  Fu  Jiangwei  Chen  Liang  Ding  Pengchu 《Acta Geotechnica》2022,17(10):4699-4715

Acta Geotechnica - Air leakage in borehole not only seriously restricts the development and utilization of coal bed methane (CBM) but also affects gas disaster prevention and underground safety...  相似文献   

A simplified analysis approach for the effect of the installation of adjacent XCC pile on the existing single XCC pile in undrained clay     

Zhou  Peng  Liu  Hanlong  Zhou  Hang  Cao  Guangwei  Ding  Xuanming 《Acta Geotechnica》2022,17(12):5499-5519

Acta Geotechnica - In this paper, a simplified two-stage analysis method is introduced to predict the lateral response of the existing X-section Cast-in-place Concrete (XCC) pile caused by adjacent...  相似文献   

Strengthening mechanisms in cement-stabilized kaolinite revealed by cross-scale nanoindentation     

Liu  Li  Li  Yucheng  Wu  Yongkang  Luo  Shengmin  Peng  Jing  Deng  Yongfeng  Zhang  Guoping 《Acta Geotechnica》2022,17(11):5113-5132

Acta Geotechnica - The macroscale mechanical properties of cement-stabilized soil have been widely reported, but the microscale behavior remains largely unexplored. This paper presents the first...  相似文献   

Experimental and numerical investigation of groundwater head losses on and nearby short intersections between disc-shaped fractures          下载免费PDF全文

Ci-xiao Qu  Ming-yu Wang  Peng Wang 《地下水科学与工程》2022,10(1):33-43

Discrete fracture models are used for investigating precise processes of groundwater flow in fractured rocks,while a disc-shaped parallel-plates model for a single fracture is more reasonable and efficient for computational treatments.The flow velocity has a large spatial differentiation which is more likely to produce non-linear flow and additional head losses on and nearby intersections in such shaped fractures,therefore it is necessary to understand and quantify them.In this study,both laboratory experiments and numerical simulations were performed to investigate the total head loss on and nearby the intersections as well as the local head loss exactly on the intersections,which were not usually paid sufficient attention or even ignored.The investigation results show that these two losses account for 29.17%-84.97%and 0-73.57%of the entire total head loss in a fracture,respectively.As a result,they should be necessarily considered for groundwater modeling in fractured rocks.Furthermore,both head losses become larger when aperture and flow rate increase and intersection length decreases.Particularly,the ratios of these two head losses to the entire total head loss in a fracture could be well statistically explained by power regression equations with variables of aperture,intersection length,and flow rates,both of which achieved high coefficients of determination.It could be feasible through this type of study to provide a way on how to adjust the groundwater head from those obtained by numerical simulations based on the traditional linear flow model.Finally,it is practicable and effective to implement the investigation approach combining laboratory experiments with numerical simulations for quantifying the head losses on and nearby the intersections between disc-shaped fractures.  相似文献   

The first extra-large helium-rich gas field identified in a tight sandstone of the Dongsheng Gas Field,Ordos Basin,China     

Peng  Weilong  Liu  Quanyou  Zhang  Ying  Jia  Huichong  Zhu  Dongya  Meng  Qingqiang  Wu  Xiaoqi  Deng  Shang  Ma  Yongsheng 《中国科学:地球科学(英文版)》2022,65(5):874-881

Science China Earth Sciences - Helium gas is a scarce but important strategic resource, which is usually associated with natural gas. Presently, only one extra-large helium-rich gas field has been...  相似文献   

Multi-scale climate variations and mechanisms of the onset and withdrawal of the South China Sea summer monsoon     

Chen  Wen  Hu  Peng  Huangfu  Jingliang 《中国科学:地球科学(英文版)》2022,65(6):1030-1046

Science China Earth Sciences - The onset of the South China Sea summer monsoon (SCSSM) heralds the establishment of the large-scale East Asian summer monsoon and the western North Pacific summer...  相似文献   

Under the surface: Pressure-induced planetary-scale waves,volcanic lightning,and gaseous clouds caused by the submarine eruption of Hunga Tonga-Hunga Ha'apai volcano     

David A. Yuen  Melissa A. Scruggs  Frank J. Spera  Yingcai Zheng  Hao Hu  Stephen R. McNutt  Glenn Thompson  Kyle Mandli  Barry R. Keller  Songqiao Shawn Wei  Zhigang Peng  Zili Zhou  Francesco Mulargia  Yuichiro Tanioka 《地震研究进展（英文）》2022,2(3):100134

We present a narrative of the eruptive events culminating in the cataclysmic January 15, 2022 eruption of Hunga Tonga-Hunga Ha'apai Volcano by synthesizing diverse preliminary seismic, volcanological, sound wave, and lightning data available within the first few weeks after the eruption occurred. The first hour of eruptive activity produced fast-propagating tsunami waves, long-period seismic waves, loud audible sound waves, infrasonic waves, exceptionally intense volcanic lightning and an unsteady volcanic plume that transiently reached—at 58 ?km—the Earth's mesosphere. Energetic seismic signals were recorded worldwide and the globally stacked seismogram showed episodic seismic events within the most intense periods of phreatoplinian activity, and they correlated well with the infrasound pressure waveform recorded in Fiji. Gravity wave signals were strong enough to be observed over the entire planet in just the first few hours, with some circling the Earth multiple times subsequently. These large-amplitude, long-wavelength atmospheric disturbances come from the Earth's atmosphere being forced by the magmatic mixture of tephra, melt and gasses emitted by the unsteady but quasi-continuous eruption from 0402±1–1800 UTC on January 15, 2022. Atmospheric forcing lasted much longer than rupturing from large earthquakes recorded on modern instruments, producing a type of shock wave that originated from the interaction between compressed air and ambient (wavy) sea surface. This scenario differs from conventional ideas of earthquake slip, landslides, or caldera collapse-generated tsunami waves because of the enormous (～1000x) volumetric change due to the supercritical nature of volatiles associated with the hot, volatile-rich phreatoplinian plume. The time series of plume altitude can be translated to volumetric discharge and mass flow rate. For an eruption duration of ～12 ?h, the eruptive volume and mass are estimated at 1.9 ?km³ and ～2 900 ?Tg, respectively, corresponding to a VEI of 5–6 for this event. The high frequency and intensity of lightning was enhanced by the production of fine ash due to magma—seawater interaction with concomitant high charge per unit mass and the high pre-eruptive concentration of dissolved volatiles. Analysis of lightning flash frequencies provides a rapid metric for plume activity and eruption magnitude. Many aspects of this eruption await further investigation by multidisciplinary teams. It represents a unique opportunity for fundamental research regarding the complex, non-linear behavior of high energetic volcanic eruptions and attendant phenomena, with critical implications for hazard mitigation, volcano forecasting, and first-response efforts in future disasters.  相似文献   

内蒙古西辽河平原植被指数时空变化及其影响因素研究          下载免费PDF全文

高萌萌  刘琼  王轶  李小磊  石鹏 《水文地质工程地质》2022,49(1):175-182

西辽河平原位于我国北方农牧交错带,属半干旱气候,发育科尔沁沙地,生态环境极其脆弱,开展植被指数时空变化及其影响因素研究,对于预测土地退化风险意义重大,可为该流域生态环境保护治理及水资源合理开发利用提供技术支撑。利用2000—2019年MODIS NDVI数据,采用一元线性回归趋势法和Mann-Kendall检验分析了近20年来该地区的植被生长变化趋势及突变情况。从影响植被生长的水热条件出发,分析了NDVI值与气象因素（降水、气温）、土壤湿度、地下水埋深等因子的相关关系;结合人类活动,分析了土地利用类型变化对NDVI值的影响。结果表明:（1）2000—2019年生长季NDVI值整体呈上升趋势,不存在显著突变点,最高值0.56,最低值0.41。（2）NDVI值在空间上呈现“东高西低”的分布特征,不同用地类型的NDVI值由大到小依次为耕地>林地>沼泽地>滩地>草地>盐碱地>沙地。（3）92.5%的区域植被呈增长趋势,7.5%的区域植被呈减少趋势。（4）NDVI值与降水、气温、土壤湿度呈正相关关系,相关系数分别为0.86,0.78,0.81,降水对植被影响最大。（5）最适宜天然植被生长的地下水埋深约为3 m,当地下水埋深大于10 m时,NDVI值会随着埋深的增加剧烈减小。（6）人类活动如土地开垦、植树造林是近20年来NDVI值呈增加趋势的主要原因之一,在一定程度上改善了当地生态环境。  相似文献