Brittle crack growth in rocks     

W. Müller 《Pure and Applied Geophysics》1986,124(4-5):693-709

Fracture phenomena in rocks are associated with mainly mode I crack growth, sometimes superposed by shear or torsion. The present paper contributes to a fracture mechanics analysis of mode I and mixed mode crack propagation, by presenting reliable fracture toughness data for some rocks which include the effect of induced crack propagation rate, and the influence of effective pressure, and by numerical calculations on fracture propagation in layered rock formations. Empirical relations between fracture toughness,K _Ic' and induced crack opening displacement rate, as well as effective pressure, are given. The observedK _Ic pressure relation supports a theoretical model which takes into account the existence of microcracks in the crack tip region. Finite element calculations of fracture propagation in layered rock formations demonstrate the important effect of mixed mode crack growth. The numerical approach is particularly applied to single crack growth in hydraulic fracturing and in three point bending tests on layered single edge crack specimens.  相似文献   

单轴受拉时冻土结构变化及其机理初析     

沈忠言  王家澄 《冰川冻土》1996,18(3):262-268

土体地单轴拉应力作用下，轴向经历变形，结构发生本质性的变化，径向同时出现收缩。这种应变特性改变了矿物颗粒间的微应力场，它是土体在径向上发生颗粒错位，定向排列，微裂隙等发育等结构变化的源动力。  相似文献   

Analysis of long-period events recorded at Mount Etna (Italy) in 1992, and their relationship to eruptive activity     

S. Falsaperla  E. Privitera  B. Chouet  P. Dawson 《Journal of Volcanology and Geothermal Research》2002,114(3-4)

Seismic activity recorded at Mount Etna during 1992 was characterized by long-period (LP) events and tremor with fluctuating amplitudes. These signals were associated with the evolution of the eruptive activity that began on December 14, 1991. Following the occurrence of numerous volcano-tectonic earthquakes at the onset of the eruption, LP events dominated the overall seismicity starting in January, 1992. The LP activity occurred primarily in swarms, which were temporally correlated with episodic collapses of the crater floor in the Northeast Crater. Source depths determined for selected LP events suggest a source region located slightly east of Northeast Crater and extending from the surface to a depth of 2000 m. Based on the characteristic signatures of the time series, four families of LP events are identified. Each family shares common spectral peaks independent of azimuth and distance to the source. These spectral features are used to develop a fluid-filled crack model of the source. We hypothesize that the locus of the LP events represents a segment of the magma feeding system connecting a depressurizing magma body with a dike extending in the SSE direction along the western wall of Valle del Bove, toward the site of the Mount Etna eruption. We surmise that magma withdrawal from the source volume beneath Northeast Crater may have caused repeated collapses of the crater floor. Some collapse events may have produced pressure transients in the subjacent dike which acted as seismic wave sources for LP events.  相似文献   

1966年邢台Ms7.2级地震的前震序列分析   总被引：4，自引：0，他引：4  

左兆荣  吴建平 《华北地震科学》1995,13(2):7-15

断层或裂纹在其失稳破裂之前都要经历准静态的加速扩展过程。加速是失稳的一个必要条件。加速释放是成核在脆性层中的大地震的普遍前兆。且可将该加速过程简要地概括为地震释放速率比例于失稳破裂产剩余时间的负幂。  相似文献   

Post-seismic stress evolution for a strike-slip fault in the presence of a viscoelastic asthenosphere     

Maria Elina Belardinelli  Maurizio Bonafede 《Geophysical Journal International》1995,123(3):744-756

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On the stability of fissured slopes subject to seismic action     

S. Utili  A.H. Abd 《国际地质力学数值与分析法杂志》2016,40(5):785-806

A set of analytical solutions achieved by the upper bound theorem of limit analysis and the pseudo‐static approach is presented for the assessment of the stability of homogeneous c, ϕ slopes manifesting vertical cracks and subject to seismic action. Rotational failure mechanisms are considered for slopes with cracks of either known or unknown depth and location. A validation exercise was carried out based on numerical limit analyses and displacement‐based finite‐element analyses with strength reduction technique. Charts providing the stability factor for fissured slopes subject to both horizontal and vertical accelerations for any combination of c, ϕ and slope inclination are provided. The effect of the direction of the vertical acceleration on slope stability is specifically analysed. Yield seismic coefficients are also provided. When the presence of cracks within the slope can be ascertained with reasonable confidence, maps showing the zones within the slope where they have no destabilising effect are provided. Finally, Newmark's method was employed to assess the effect of cracks on earthquake induced displacements. To this end, displacement coefficients are provided in chart form as a function of the slope characteristics. Two examples of slopes subjected to known earthquakes are illustrated. © 2016 The Authors. International Journal for Numerical and Analytical Methods in Geomechanics published by John Wiley & Sons Ltd.  相似文献   

土壤添加物对土-水曲线和土体收缩的影响   总被引：3，自引：0，他引：3       下载免费PDF全文

邢旭光  柳烨  马孝义 《水科学进展》2016,27(1):40-48

为探索不同添加物(小麦秸秆、麦壳和植物油渣)对土壤持水性能和土壤收缩特性的影响,定量掺混3种粉末,采用离心机法测定土-水曲线,并对土壤持水能力和土壤收缩特征进行评价。结果发现:各处理土-水曲线形态无差异,van Genuchten模型可用于此条件土-水曲线拟合;3种添加物均可提高土壤容重和土壤含水率并利于保水,且土壤持水能力表现为油渣 >麦秆 >麦壳 >纯土;随着土壤脱水,土体以轴向收缩为主,三直线模型可用于土壤收缩曲线拟合,土体线缩率与吸力和含水率分别满足对数和Logistic函数关系;土体几何收缩量表现为麦壳 <油渣 <麦秆 <纯土,土壤开裂程度表现为油渣 <麦秆 <麦壳 <纯土。  相似文献   

Crack-wave dispersion at a fluid-filled fracture withlow-velocity layers     

Koji Nagano 《Geophysical Journal International》1998,134(3):903-910

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地下岩层裂隙的几种勘察研究方法     

张连明  周峰  张兆坤 《水文地质工程地质》2003,30(4):111-114

本文介绍了地下岩层裂隙的4种勘察研究方法:钻孔岩芯法、超声成像法、钻孔电视法、钻孔流量测井法。经过多项工程实践,我们认为超声成像法对钻孔孔壁扫描获得裂隙产状、开度等参数是研究地下岩层裂隙的有效方法。钻孔流量测井法也可研究裂隙,计算裂隙开度。  相似文献   

A Study on Shear Wave Splitting for the Sequence of the Aftershocks of the Yao''''an M_S6.5 Earthquake in Yunnan Province     

Qian Xiaodong  Li Baiji  Qin Jiazheng 《中国地震研究》2003,17(1):32-41

INTRODUCTIONS wavesplittingisnotonlystudiedintheory,buthasalsobeenthesubjectofalotoffieldobser vationsandcomputersimulationsinceCrampin (1978)raisedtheExtensiveDilatancyAnisotropy(EDA) .Thoseinvestigationstriedtotestifythecorrectnessofthehypothesis,namelythatthevertical lyparallelcracksappliedunderthestresshaveeffectiveanisotropy,whichcanresultinshearwavesplitting.Sincethe 1980s,thedigitalseismometerwithbroadbandandhighaccuracyhasbeenusedwidelyinseismicobservations,andtheprocessingtechn…  相似文献